- 
 
A New 
 
 Considerable attention is now being given in Paris to a 
 new lamp, the invention of Messrs. B. Delachanal and A. 
 Mermet, and intended for photographic and other purposes 
 where a brilliant light is required. 
 
 The media employed are carbon sulphide and binoxide of 
 nitrogen. Ignition of binoxide of nitrogen containing vapor 
 of carbon sulphide produces a brilliant flame of a violet blue 
 tint, peculiarly rich in chemical rays. The carbon sulphide 
 lamp by which this flame is produced continuously is con- 
 structed simply of a flask with two tubulures, the vesse 1 
 having about 30'5 cubic inches capacity. The flask is 
 filled with spongy fragments of coke, or, better, of dried 
 pumice, which imbibes the carbon sulphide. Through the 
 central tubulure passes a tube to within a short distance of 
 the bottom; in the other mouth or tubulure is fixed a tube 
 of larger dianietar, about 7*85 inches in length. Th<- 
 latter tube is of glass or metal, and contains an arrange- 
 ment acting as a safety valve as well as impeding return of 
 the gas and preventing explosion. Binoxide of nitrogen is 
 passed by this tube into the flask, and the gaseous mixture 
 is conducted by a caoutchouc tube to a kind of Bunsen 
 burner, from which has been removed the air port and the 
 cone regulating the supply of gas. The binoxide of nitro- 
 gen is produced by a St. Claire Deville apparatus ; but instead 
 of decomposing nitric acid by copper, which would be too 
 expensive, a mixture of nitric and sulphuric acid is caused 
 to act upon iron. 
 
 The flame, which is about 10 inches in hight, possesses 
 high photogenic properties, and is much superior to the 
 light obtained from the magnesium ribbon. The apparatus 
 is nearly as portable, the mixed acid being contained in one 
 vessel which communicates by a tube with a vessel contain- 
 ing fragments of iron. Supply is regulated by a cock. The 
 flame is constant, unlike that of the electric light, and is not 
 subject to spontaneous extinctions like the magnesium 
 lamp. Photographs of human subjects are obtained in a 
 less exposure than fourteen seconds. Photometric tests 
 show (flame for flame, per measure) about twice the power of 
 the oxyhydrogen light. 
 
 The inventors are studying the question of development of 
 the green coloring matter of plants by means of this light. 
 The experiments are being made in M. Dumas' laboratory at 
 the Central School of Paris, an d the result will shortly be 
 pnade public. 
 
CHEMICAL AND PHARMACEUTICAL 
 
 MANIPULATIONS: 
 
 A MANUAL OP THE 
 
 MECHANICAL AND CHEMICO-MECHANICAL OPERATIONS 
 
 LABORATORY. 
 
 FOR THE USB OF 
 
 CHEMISTS, DRUGGISTS, MANUFACTURERS, 
 TEACHERS, AND STUDENTS. 
 
 aiib 
 
 BY 
 
 CAMPBELL MORFIT, 
 
 PROFESSOR OF ANALYTIC AND APPLIED CHEMISTRY IX TUB UNIVERSITY OF MARYLAND, 
 
 AND 
 
 CLARENCE MORFIT, 
 
 ASSISTANT MELTER AND REFINER IN UNITED STATES ASSAY OFFICE. 
 
 FIVE HUNDRED AND THIRTY-SEVEN ILLUSTRATIONS. 
 
 PHILADELPHIA: 
 
 LINDSAY AND BLAKISTON. 
 
 185T. 
 
Entered, according to Act of Congress, in the year 1856, 
 
 BY LINDSAY & BLAKISTON, 
 In the Clerk's Office of the District Court for the Eastern District of Pennsylvania. 
 
 C. SHERMAN' & SOX, PRINTERS- 
 
 19 St. James Street. 
 
DEDICATED 
 
 JOHN HENRY ALEXANDER, 
 
 ETC. ETC. ETC.! 
 
 IN APPRECIATION OF 
 
 HIS HIGH MORAL WORTH 
 
 GREAT SCIENTIFIC ATTAINMENTS. 
 
. 
 
 
PREFACE. 
 
 To realize for Chemistry its true character of a science 
 to render it "a system illustrated and proved by experi- 
 ment," there is an indispensable need of proficiency in those 
 manual operations of the laboratory, by means of which 
 chemical changes are induced, observed, and estimated. 
 This accomplishment in manipulation this expertness in 
 handling and adjusting implements, it is true, depends upon 
 time and practice ; but although the student may riot become 
 an adept in the art solely from written instructions, yet 
 much may be thus taught which will lighten his labors, and 
 smooth the way to the acquisition of skill and accuracy. 
 
 Such is the object of the present work ; and it has been 
 made to comprise practical lessons upon the mechanical and 
 chemico-mechanical business of the chemist, in reference 
 both .to the exact detail of analytic research, and the more 
 extended processes of pharmaceutical science. Explanatory 
 drawings of important forms of apparatus, too, have been 
 profusely employed to give v greater intelligibility to the text; 
 and while the authors have drawn largely from their own 
 personal experience, they have not neglected to make avail- 
 able all the useful information that was to be derived from 
 other sources. 
 

 viii PREFACE. 
 
 In this second and enlarged edition, there are many im- 
 provements upon the original work. The old matter has 
 been emended, and much that is novel and valuable added ; 
 so that in its present form it embraces full and fresh teach- 
 ings, adapted to the requirements of the uninitiated, as well 
 
 as of the more advanced student. 
 
 C. M. 
 
 UNIVERSITY OF MARYLAND, BALTIMORE, 
 October 15, 1856. 
 
TABLE OF CONTENTS. 
 
 CHAPTER I. 
 
 THE LABORATORY. 
 
 Its construction; arrangement; ventilation. The office; its furniture, . 17 
 
 CHAPTER II. 
 
 THE BALANCE ROOM. 
 
 Its arrangement; tables for the support of the balances, . . .28 
 
 CHAPTER III. 
 
 THE FURNACE ROOM. 
 
 Its arrangement; the furnace; the sand-baths; the hood; the steam 
 generator; the steam jack; steam series; the still; the gas chamber; 
 Beindorff's apparatus; the sink; the draining racks; the cleansing 
 apparatus; the tool chest, "... 29 
 
 CHAPTER IV. 
 
 THE OPERATING ROOM. 
 
 Its furniture ; the operating table ; the test rack ; the spirit lamp ; the 
 gas furnace; the table sand-bath; the centre table; the blowpipe table: 
 
CONTENTS. 
 
 the air-pump; the closets; the bottles; the labels; the test case; the 
 test series; the cleansing of glassware; the records of analyses; index 
 
 DIVISION OF SUBSTANCES. 
 
 Slicing; crushing; pulverization; Coffey's apparatus; mortars; tritura- 
 tion; Hewitt's apparatus; Goodal's grinding machine; porphyrization ; 
 sifting; sieves; Harris's sieve; levigation; elutriation; granulation; 
 division by chemical means; by intermedia, ..... 86 
 
 CHAPTER V. 
 
 THE BALANCE. 
 
 Its requisite conditions; the Mint balance ; Eater's and Robinson's ba- 
 lance; Berlin balance; Tralle's beam; Beranger's platform balance; 
 preservation of balances, . . . . . .100 
 
 CHAPTER VI. 
 
 THE WEIGHTS. 
 
 Metrical or decimal weights; table of their relative value with troy and 
 avoirdupois weights ; adjustment, preservation, and handling of weights, 1 IG 
 
 CHAPTER VII. 
 
 WEIGHING. 
 
 Preliminary remarks; weighing of solids; of corrosive substances: of 
 liquids; weighing of gases; correction of gases for moisture, . . 120 
 
 CHAPTER VIII. 
 
 DETERMINATION OF SPECIFIC GRAVITY. 
 
 Specific gravity of solids; by means of the balance; by means of the stop- 
 pered flask; by the areometer; by Alexander's method; specific gra- 
 vity of fluids; by means of the flask; specific gravity bottles; by the 
 hydrometer; by Harris's method; Nicholson's gravimeter; specific 
 gravity of gases; rules for determining the changes in the bulk of gases 
 induced by pressure and temperature; specific gravity of vapors; table 
 of specific gravities, 129 
 
CONTENTS. XI 
 
 CHAPTER IX. 
 
 MEASURES AND MEASURING. 
 
 Measuring of fluids; graduates; the graduation of vessels; of tubes; mea- 
 surement of gases; pipettes; dropping-tubes, . . ".' "' . 194 
 
 CHAPTER X. 
 
 MEASUREMENT OF TEMPERATURE. 
 
 Pyrometers; thermometers; Fahrenheit's, Celsius's, and Reaumur's 
 scales; rules for translating the degrees of one into those of the others; 
 differential thermometers; the therm ometrograph; the mode of using 
 thermometers; table of thermometrical equivalents, .... 205 
 
 CHAPTER XL 
 
 SOURCES AND MANAGEMENT OF HEAT. 
 
 Furnaces; wind furnace; universal furnace; portable furnace; evapo- 
 rating, calcining, reverberatory, blast, assay, or cupel furnaces; Bar- 
 ren's wind furnace ; Liebig's furnace ; the management of furnaces ; 
 their furniture. Lamps; glass spirit lamp; heating of tubes by lamps; 
 Berzelius's spirit lamp; supports; crucible jacket; Luhme's and Rose's 
 lamps; the Russia lamp; Deville's blast lamp; Nunn's blast lamp; 
 the table gas lamp; the use of gas and its manufacture from grease 
 and resin; crucibles heated over blowpipe flame; Beale's gas furnace; 
 Hoffman's gas furnace; Hart's gas furnace ; Hare's compound blow- 
 pipe; Tate's blowpipe; Sonnenschein's blowpipe; generation of oxygen 
 and hydrogen gases; self-regulating gas reservoir; the Drummond 
 light. Supports; the universal support; wooden supports; retort 
 holders; tube and bulb rests ; filter stands; the test rack, . . . 218 
 
 CHAPTER XII. 
 
 BATHS. 
 
 Their construction; the steam-bath; the water-bath ; saline baths; table 
 of the boiling-points of saturated solutions; metallic baths; oil-baths; 
 the sand-bath, ..... 264 
 
Xii CONTENTS. 
 
 CHAPTER XIII. 
 
 THE MODE OF PRODUCING LOW TEMPERATURES. 
 
 Freezing mixtures j their modes of application ; ice-box ; tables of the 
 composition of a number, and of the degrees of cold which they pro- 
 duce, 271 
 
 CHAPTER XIV. 
 
 FUSION. 
 
 Igneous and aqueous fusion; crucibles, clay, Hessian, London, French, 
 black lead; blue pots; porcelain and metallic crucibles; iron, silver, 
 platinum crucibles; instructions as to the proper manner of using pla- 
 tinum crucibles ; directions for heating crucibles ; fusion of substances 
 unalterable by heat or air; of substances alterable by heat; of bodies 
 alterable by air; of difficultly fusible substances, . 277 
 
 CHAPTER XV. 
 
 IGNITION. 
 
 Ignition of filters; of bodies in vapors; with fluxes; non-metallic fluxes; 
 metallic fluxes; fluxing and calcination; coking; incineration; roast- 
 ing; deflagration; decrepitation; reduction; reduction by charcoal; 
 by hydrogen ; flexible tubes ; india rubber gas bags ; reduction by car- 
 bonic oxide; roasting and reduction in tubes; combustion in glass 
 tubes; tube jacket; glass, porcelain, metallic tubes, . . . .287 
 
 CHAPTER XVI. 
 
 CUPELLATION. 
 
 Cupels; their manufacture; process of cupellation; muffles, Taylor's, . 310 
 
 CHAPTER XVII. 
 
 SUBLIMATION. DISTILLATION. 
 
 Sublimation; in tubes; in flasks; in retorts; in alembics; in crucibles; 
 in shallow vessels; Ure's apparatus; hydro-sublimation. Distillation; 
 the still; the cooler; Gedda's condenser; distillation in retorts; the 
 
CONTENTS. Xlll 
 
 mode of arranging apparatus for distillation ; receivers ; distillation in 
 tubes; platinum, iron, porcelain, earthenware and stone retorts; gene- 
 ral rules for distillation ; of liquids ; of volatile liquids ; application of 
 freezing mixtures; Florentine receivers; cohobation; rectification; 
 distillation of gases ; tube apparatus; flask generators; funnel tubes; 
 Kemp's generator; Fresenius's sulphuretted hydrogen apparatus ; col- 
 lection of gases; solution of gases; WolfFe's bottles; safety tubes; 
 gasometer; caoutchouc bags; gases received in Pepy's and other 
 gasometers; transferred from gasometers; mercurial gasometer; De- 
 ville's gasometer ; pneumatic troughs ; the water trough ; bell glasses ; 
 gas jars; the mercury trough ; gases collected over air; transfer of 
 gases; distillation in vacuo; dry distillation; heating under pressure 
 in tubes, V, -" . . . . x . . . . . 314 
 
 CHAPTER XVIII. 
 
 LUTES. 
 Lutes for coating fire vessels; mode of applying lutes, .... 380 
 
 CHAPTER XIX. 
 
 THE BAROMETER. 
 
 Its principle and application ; stationary and portable or mountain baro- 
 meters; wheel barometer; cistern barometers ; Newman's, Troughton's, 
 Fortin's, Hassler's, and Alexander's barometers ; Gay Lussac's syphon 
 barometer; Morland's diagonal barometer; rectangular barometer; 
 Daniell's water barometer; sulphuric acid barometer; Adie's sympie- 
 someter; aneroid barometers; Bourdon's barometer; Wollaston's and 
 Regnault's barometer; register barometer; table of corrections for 
 capillary depression in barometer tubes; table of barometric correc- 
 tions for temperature, V v n,: : 336 
 
 CHAPTER XX. 
 
 SOLUTION. 
 
 Solution, simple and chemico-mechanical ; neutralization; solution of . 
 solids; of liquids; of gases; table of the solubility of salts. . .417 
 
 CHAPTER XXL 
 
 MACERATION. INFUSION. DECOCTION. DIGESTION. 
 
 Digestion under pressure ; Papin's digester ; D'Arcet's and Mohr's di- 
 gesters ; boiling in tubes ; test-tubes ; beaker-glasses ; flasks and cap- 
 
XIV 
 
 CONTENTS. 
 
 sales-, solution by steam; by displacement; Robiquet's displacing 
 apparatus ; by Cadet's method ; under pressure by steam ; Duvoir's 
 apparatus ; pressing, ''- v : " ' t 437 
 
 CHAPTER XXII. 
 
 EVAPORATION. 
 
 Evaporating vessels; spontaneous evaporation; evaporation in vacuo ; 
 by heat in open air ; over baths ; by steam ; by heated air ; over the 
 naked fire ; Marcet's experiments, 463 
 
 CHAPTER XXIII. 
 
 CRYSTALLIZATION. 
 
 Crystallization by fusion ; by sublimation ; from solution ; granulation ; 
 purification of crystals ; crystallization by chemical reaction, . .472 
 
 CHAPTER XXIV. 
 
 DESICCATION. 
 
 Desiccation of solids ; efflorescence ; desiccation in air-chambers ; over 
 baths; of easily alterable substances ; in vacuo; of liquids; of gases; 
 Kemp's thermostat, .......... 478 , 
 
 CHAPTER XXV. 
 
 PRECIPITATION. 
 Precipitating vessels ; directions for precipitating, . . . .491 
 
 * ' 
 
 CHAPTER XXVI. 
 
 DECANTATION FILTRATION. 
 
 Decantation by pouring ; by syphons ; Coffee's syphon ; filtration through 
 paper; filtering papers; funnels; filters folded and introduced into 
 funnels ; supports for funnels ; directions for filtering ; pouring ; spritz 
 bottle ; filtration promoted by warmth ; filter baths ; filtration through 
 cloths ; through pulverulent matter ; of volatile liquids ; Donovan's 
 and Riouffe's filters, .... 493 
 
CONTENTS. XV 
 
 CHAPTER XXVII. 
 
 WASHING. 
 
 Washing of precipitates ; the spritz or washing bottle ; edulcoration ; 
 Cook's apparatus for washing with volatile liquids, . . . .513 
 
 CHAPTER XXVIIL 
 
 THE PRACTICAL RELATIONS OF ELECTRICITY. 
 
 Cylinder and plate electrical machines ; Leyden jar ; electrical battery ; 
 discharger ; the electrophorus : Detection and measurement of Elec- 
 tricity: Electroscopes; Henly's quadrant electrometer; Bennet's 
 electrometer ; voltaic pile electroscope ; Coulomb's torsion balance ; 
 Lane's discharging electrometer ; calorific electrometer ; the galvano- 
 meter ; astatic galvanometer ; differential galvanometer ; Weygandt's 
 galvanometer. Application of Electricity : Eudiometry ; Ure's eudio- 
 meter. Electricity developed by galvanic action: Wollaston's, Daniell's, 
 Smee's, Grove's, and Bunsen's batteries; connection of batteries; elec- 
 trolysis ; production of heat and light by galvanism ; Hare's sliding 
 rod eudiometer and calorimotor. Electro-Metallurgy: Preliminary 
 manipulations; moulds; plating solutions, . . . . .519 
 
 CHAPTER XXIX. 
 
 BLOWPIPE MANIPULATIONS. 
 
 Use and construction of blowpipes; Gahn's, Mitscherlich's, and De Luca's 
 blowpipes; economical blowpipe; the combustible; blowpipe lamp 
 and appliances ; flame ; the mode of holding the blowpipe ; the blast ; 
 the -supports ; detection of volatile substances by means of the blow- 
 pipe ; instruments used in analysis by the blowpipe ; reagents ; blow- 
 pipe table ; Herapath's table for testing by the blowpipe, . . .572 
 
 CHAPTER XXX. 
 
 GLASS BLOWING. 
 
 Blowpipe table and lamp : implements ; cutting of glass ; tubes cement- 
 ed, bent, drawn out, and closed ; lateral attachments ; bulbs blown ; 
 Welters and funnel-tubes fashioned, . ... . i . G01 
 
XVI CONTENTS. 
 
 CHAPTER XXXI. 
 
 CORKS. 
 
 Corks softened, perforated ; cork-borer, . . . . . ,612 
 
 CHAPTER XXXII. 
 
 WEIGHTS AND MEASURES. 
 Corresponding values of French and English weights and measures, 614 
 
CHEMICAL AND PHARMACEUTICAL 
 MANIPULATIONS. 
 
 CHAPTER I. 
 
 THE LABORATORY. 
 
 THE Laboratory is emphatically the workshop of the chemical 
 operative ; and chemical manipulation may be termed the practice 
 of the science. A convenient arrangement of the first is no less 
 desirable, for the success of operations, than a proficiency and 
 skill in the latter are indispensable. New facts in science are 
 mainly developed by experiment ; and as chemistry is a purely 
 experimental science, in every course of research, as well in the 
 most ordinary experiments as in the more delicate manipulations 
 of analysis, the surest basis of exact deductions is a skilful 
 manipulation coupled with correct reasoning. This exemplifica- 
 tion, by the hands, of the conceptions of the mind, is, therefore, 
 an art of the highest importance in the study of chemistry. 
 
 The laboratory should be appropriately fitted, and arranged 
 with a view to the ready prosecution of chemical investigation in 
 all its several branches ; and being the place where most of the 
 operator's time is so profitably and pleasantly employed, no little 
 regard, in its appointments, should also be given to personal 
 comfort and convenience. 
 
 The apparatus must be selected with careful discrimination, so 
 that the stock may consist, chiefly, of such pieces as admit of 
 being adapted to the greatest variety of uses ; and it will prove, 
 ultimately, most economical to prefer those of the best materials 
 and workmanship, though their first cost may be a little higher 
 than that of inferior and less durable articles. Ample facilities, 
 to this end, are presented by the extensive assortments of esta- 
 blishments whose speciality is the sale of chemical wares and 
 
 2 
 
18 THE LABORATORY ITS CONSTRUCTION. 
 
 pure chemicals. They are now to be found in all our principal 
 cities and towns, having risen during the last few years in obedi- 
 ence to the requirements of a prevailing taste for chemical 
 pursuits. The implements which they offer, being skilfully con- 
 structed upon correct principles, promote the spirit and progress 
 of experiment and facilitate a promptness and accuracy of results 
 which might not be obtainable by less favorable means, except at 
 a large expenditure of time and patience. Moreover, a familiarity 
 with the use of good tools begets habits of precision which soon 
 render the operator an adept in manipulation, and enable him to 
 meet the exigencies of any new case by the suggestions of his 
 experience and genius. 
 
 It is true that the dealers' exorbitant prices for apparatus are 
 unreasonably high, and in a measure restrict the study of che- 
 mistry ; but this imposture will be regulated by competition, as 
 time increases the demand ; for the original manufacturing cost 
 is only a small moiety of the retail charge. Even at present 
 prices, it is perhaps more judicious to draw supplies from such 
 sources, for there is very little satisfaction and much loss of time 
 that might be more profitably applied, in the employment of 
 crude contrivances. In discouraging "home manufactures" in 
 this connection, therefore, we cannot incur the reproach of ex- 
 travagance, as our advice is based upon personal experience, 
 and intended to protect the interest of the student. 
 
 In developing the plan for a Laboratory, we shall make our 
 suggestions consistent with true economy ; and while presenting a 
 design, complete in all its details, will accompany it with such 
 incidental instruction, as will render it capable of being modified 
 according to the means of the operator or the purposes for which 
 it may be intended, whether as a Laboratory for public instruc- 
 tion or for private research. 
 
 Health and comfort demand free light, regular warmth, and 
 ample ventilation in all the apartments of a Laboratory. Light 
 should be admitted through side windows, as they afford the 
 greatest advantage for examining the action of reagents, par- 
 ticularly in those instances of delicate testing which result only 
 in light flocculse, faint cloudiness, slight change of color, or other 
 behavior requiring nice scrutiny. By elongating the sash to 
 nearly the whole height of the ceiling, the solar rays may be 
 
THE LABORATORY ITS CONSTRUCTION. 
 
 19 
 
 Fig. 1. 
 
 brought under management when their aid is required in certain 
 operations. 
 
 The sash should he hung with counterpoise weights, so as to 
 give facility in raising or lowering them for the admission of air 
 or other purposes. 
 
 Skylights are objectionable on account of their liability to 
 frequent damage by storm and acci- 
 dent. They moreover present recepta- 
 cles for dust and cobwebs. 
 
 The warming of the apartments may 
 be best accomplished by means of Tas- 
 ker's or other self-regulating water- 
 furnace (Journal Frank. Instit. xxix, 
 417). The heat is radiated directly 
 from the surface of iron pipes, dis- 
 tributed throughout the building and 
 connecting with the generator in the 
 cellar, which should supply them with 
 a continuous current of steam. 
 
 This mode of heating combines 
 economy with efficiency and is promo- 
 tive of health, comfort, convenience, 
 and safety from accident by fire ; as it 
 produces none of the usual disagreea- 
 bility of dust and irregular tempera- 
 ture incident to "hot-air furnaces" 
 and open fires. 
 
 As the internal atmosphere of the 
 Laboratory is being constantly vitiated 
 by noxious emanations from substances 
 under process, as well as by respira- 
 tion, efficient means must be adopted 
 for displacing the foul air by introdu- 
 cing, simultaneously, pure fresh air 
 in such a manner as to prevent dis- 
 comfort from cold draughts. The 
 tendency of the foul air, even when not specifically lighter than 
 the surrounding air, is to ascend, owing to its being rarefied by 
 the heat of the Laboratory, and therefore it may be readily made 
 
20 THE LABORATORY ITS CONSTRUCTION. 
 
 to pass from the apartment through a panel of coarse wire grating 
 (Fig. 1, a) placed in the wall of the chimney flue, near the ceiling. 
 This panel should be twelve inches broad and nine inches high 
 for a room of forty feet square, and proportionally smaller for 
 one of lesser dimensions ; and to prevent the entrance of smoke 
 in gusty weather, there should be affixed to the inside a hinged 
 flap (b) made of very fine wire gauze. The draught action of 
 the warm flue carries away the unwholesome air, as shown by the 
 arrows ; and the pure air entering, to supply its place, through 
 the many crevices in the doors and windows, and about the build- 
 ing, quickly diffuses itself and thus becomes warm without cre- 
 ating any perceptible cold currents. Even in summer, or when 
 there is no fire on the hearth to dilate the air in the flue, the wind 
 blowing across the top of the chimney produces a partial vacuum 
 at the mouth, towards which the upper air of the room will be 
 moved by the upward pressure of the denser lower strata. 
 
 Dr. Murray uses a funnel-mouthed tube instead of a grating, 
 and conveys the tube through the ceiling into a chimney, where 
 there is a constant fire. To provide against the entrance of 
 smoke through any imperfection of draught, the pipe is continued 
 to the top of the chimney. The warmth of the chimney rarefies 
 the air within the pipe, and ventilation is effected, upon the prin- 
 ciple above-mentioned. 
 
 The laboratory apartment should be sufficiently spacious to 
 afford a separate place for each of the requisite utensils. Too 
 much crowding of apparatus is apt to produce damage, and is, 
 besides, inconvenient ; for nowhere than in a Laboratory is there 
 more necessity of a strict observance of the rule, " a place for 
 everything, and everything in its place." Hunting up mislaid 
 apparatus consumes time, and the delay thus occasioned, in many 
 instances, may be the means of serious detriment to important 
 operations. 
 
 A roomy apartment on the first floor of a building is best 
 suited for laboratory purposes. The first floor is recommended, 
 because of its greater convenience for the admission of water, 
 fuel, &c., and for the removal of the slops, sweepings, &c. It 
 should be partitioned off into four several apartments, the middle 
 or larger of which should be the main operating room, whilst the 
 smaller at either of its sides are used, the one as an office, the 
 
THE LABORATORY ITS CONSTRUCTION. 
 
 21 
 
 other as the furnace room, and the third for the balances. This 
 arrangement protects the middle room from the dirt and dust of 
 the coarser furnace operations, and the balances from the influ- 
 ence of corrosive vapors ; and what is equally indispensable, by 
 means of the office as a reception room, presents a bar to all un- 
 welcome intrusion from without. 
 
 As, in some instances, it may be convenient to construct a 
 building especially for a laboratory, we present the plan of a 
 properly furnished one, such as might be completed for a very 
 moderate outlay. It is of coarse brick, and rough-cast with 
 mastic, which, becoming indurated in a short time, serves as a 
 
 Fig. 2. 
 
 perfect protection to the walls against all dampness, and imparts 
 a stone-like appearance to the building. A very good mastic 
 may be made by oven-drying a mixture of the following powders, 
 and then working it, in the usual manner of mortar, with one- 
 seventh of its total weight of linseed-oil : 14 volumes of sili- 
 cious sand ; 14 volumes of powdered limestone ; 1-14 in weight 
 of litharge, that is, one-fourteenth of the joint weight of the 
 
22 THE LABORATORY ITS CONSTRUCTION. 
 
 sand and stone. The surfaces, which are to be covered with 
 this mastic, must first be washed over with linseed-oil containing 
 five to ten per cent, of rosin-oil. The linseed-oil used in the 
 mixture might also contain a portion of rosin-oil, which, without 
 detracting from its quality, will lessen the cost of the mastic. 
 
 Figure 2 gives the front view of the building. Though regard 
 is had more particularly to economy and convenience in its con- 
 struction and arrangement, yet there is sufficient reservation of 
 architectural symmetry to impart a neat and becoming appear- 
 ance. In the arrangement of the ground plan, we observe the 
 same positions as are recommended in the adaptation of a room 
 to laboratory purposes, so that our suggestions are equally ap- 
 plicable to either case. The whole front of the building is forty 
 feet. Its depth is twenty-four feet. The ceiling should be high, 
 say from eighteen to twenty feet. The roof is square, slightly 
 inclined, and of metal. There are two entrances only, one in 
 the left wing or furnace room, for the ingress and egress of 
 material and refuse, and the other in the office or anteroom. The 
 centre or operating apartments are thus preserved from all in- 
 convenience of dirt, dust, or intrusion. There are two chimneys, 
 that in the office being for the stove-pipe, when a stove is to be 
 used for warming, and the other in the left wing for the flues of 
 the furnaces, still, &c. The windows should extend nearly to 
 the top of the ceiling. In the preceding figure, they are twelve 
 feet by two feet eight inches, in the centre apartment, and twelve 
 feet by two feet in the wings. The glass panes of the former 
 number eighteen, those of the latter twelve. The doors have a 
 width of two feet nine inches, and height of seven feet ; and 
 each should be furnished with a spring. Oiled linen makes an 
 excellent curtain for protection against the summer sun, without 
 too much obstruction of the light. It should be hung on Putnam's 
 
 Fig. 3. 
 
 " balance spring-rollers" Fig. 3 in which the use of cords is 
 dispensed with, the curtain being raised, lowered, or held in a 
 fixed position by means of a counterpoise weight. 
 
 Curtains thus hung were exhibited at the last Annual Fair 
 
THE LABORATORY ITS CONSTRUCTION. 
 
 23 
 
 Fig. 4. 
 
 of the Maryland Institute, by Baker and Cushman, of Balti- 
 more. The roller is a hollow tin cylinder, 1 J inches diameter, 
 and revolving upon a metal rod, which is wrapped with a spiral 
 spring of brass wire ; and the combination is so adjusted, that 
 when the weight, disguised as a tassel, receives a slight upward 
 motion from the hand, the wire spring recoils, and the curtain J, 
 Fig. 4, fastened in a groove, is wound up by the roller to any 
 desired height. The roller and curtain are suspended by brack- 
 ets at the top of the window ; and the act of drawing down the 
 curtain turns the cylinder and 
 winds up the spring. This ar- 
 rangement admits also of the ap- 
 plication of a self-acting dust- 
 bar a, which consists of mosquito- 
 netting so fixed to the lower half 
 of the sash, that when the lat- 
 ter is raised it draws up the for- 
 mer to take its place. his ap- 
 paratus will be found very con- 
 venient in windy and dusty 
 weather, when it is desirable to 
 have free access for air to the 
 apartment without endangering 
 the comfort of the occupant or 
 the safety of the apparatus, &c. 
 The roller is equally advantage- 
 ous for hanging diagrams as curtains. 
 
 The top moulding of the building is of wood, plain and painted, 
 and the pillars represented in the cut, are only projections of 
 the brickwork to ornament the front of the building. It is seen 
 by Fig. 5, which represents a back view of the laboratory, that 
 the rear windows differ in form and position from those in the 
 front. The reasons will be obvious on explanation. For the 
 convenient arrangement of apparatus, it is necessary to have as 
 much wall-room, interiorly, as possible ; and as the ample win- 
 dows in the front will furnish most of the requisite light, the rear 
 windows, which are of sufficient extent to supply the remainder, 
 are elevated so as not to interfere with the tables, shelving, and 
 fixtures, resting against the wall beneath'. These windows should 
 
24 
 
 THE LABORATORY ITS ARRANGEMENT. 
 
 be hung upon metal pivots, so that they may be readily opened 
 or shut at will. The front window-sash, for reasons before given, 
 
 Fig. 5. 
 
 should be counterpoised by balance weights. The dimensions of 
 the rear windows in the wings are six by three feet, and the 
 number of glass panes in each window are eight. The side 
 light is also admitted through three elevated windows in each 
 end of the building. Their size is six by three feet, with 
 eight panes of glass each. The centre apartment has also two 
 elevated windows in the rear, but their width is one foot greater 
 than those in the wings. All of these elevated windows should 
 be hung upon metal pivots. This elevation of windows in these 
 apartments is also with a view to the economy of wall space 
 within. The basement, which, by a little expense, may be ap- 
 propriately fitted for the purpose, serves as a receptacle for fuel, 
 bricks, charcoal, tile, rough materials, and cumbersome apparatus 
 not in constant use. The best color for the woodwork is white 
 preferably, of pure zinc white ; and the walls and partitions 
 of lath and plaster should be smooth, so that the laboratory may 
 be as free as possible from loopholes for the accumulation of 
 dust. A stiff brush mat and scraper should always be furnished 
 for each entrance. If the means of the owner will permit the 
 expense, it would add much to the appearance of his place to sur- 
 
THE OFFICE THE MINERAL CASE. 25 
 
 round it with a garden plat. Thus, in improving the beauty of 
 the spot, he would be providing the means of pursuing investiga- 
 tion practically, to a limited extent, in agricultural chemistry. 
 
 Plate 2 represents a ground plan of an experimental and 
 analytical laboratory, either as especially constructed for the 
 purpose, or from any room of adequate dimensions. The main 
 divisions of the apartment, as before said, are three, the fourth 
 in the plan being only a subdivision. The two wings A and B, 
 of equal size, are 10-3 by 22-6 feet in the. clear. That on the 
 right should be used as the office and balance room, the left wing 
 being occupied exclusively for furnace and grosser operations, 
 leaving the centre or operating room C, occupying the whole 
 residual space of the floor, for the nicer manipulations. 
 
 The Office. This being the studio of the operative should 
 contain both the library and the mineralogical, geological, and 
 technical cabinets. These latter, not, however, necessarily 
 extensive, are very convenient for reference, as instances fre- 
 quently occur, in the course of practice, requiring a comparison 
 of specimens. The two front windows, together with the two 
 elevated windows at the outer side, serve for the free admission 
 of light. This being also used as the reception room, there is 
 an entrance door, between the two windows, of dimensions equal 
 to those of the door in the furnace room. The floor should be 
 carpeted, or, preferably, covered with oil-cloth, which is more 
 durable, and readily cleansed. The bare spots on the walls, as 
 well as the upper parts of the blank spaces between the doors 
 and windows, may be furnished with brackets for the busts of 
 distinguished chemists, or hooks upon which to hang their framed 
 portraits ; and the lower part beneath the windows may be reserved 
 for chairs k. The blank space j over the door leading into the 
 operating room can be occupied with a cheap Yankee clock, a 
 very requisite and convenient piece of furniture in a laboratory. 
 
 It is necessary to be minute in describing the arrangement, 
 for, unless there is some system, there can be no economy of 
 space, and hence much confusion. In the centre of the wing is 
 the chimney a, and immediately opposite, in near juxtaposition, 
 the hot-water stove b which warms the apartment. 
 
 Against the off wall, and to the left of the stove, is the mineral 
 case. There should be at least two of these, and the second may 
 
26 
 
 THE OFFICE THE WRITING-DESK. 
 
 Fig. 6. 
 
 occupy the vacancy in the wall immediately opposite. The 
 positions of these cases are represented in Plate 2 by the letters 
 c and d. Fig. 6 below gives an idea of their form and construc- 
 tion. They are, in fact, nothing more than mere wardrobes, with 
 
 the shelves and drawers substituted by 
 sliding trays. They can be of some 
 cheap wood, and painted. The slid- 
 ing trays are much more convenient 
 than drawers, and present less lia- 
 bility of damage to their contents, as 
 they admit of easier handling, it 
 being frequently necessary to draw 
 them out to examine their contents. 
 The specimens which they are to 
 preserve, secure from dust and un- 
 warrantable handling, should be sepa- 
 rately encased in shallow pasteboard 
 boxes, each bearing the name and 
 locality of the mineral. The mine- 
 rals should be so classified that only one species may be assigned 
 to a tray, which should be labelled on its face accordingly. The 
 trays may be of 3 to 4 inches depth, with intervening spaces of 
 an inch or less, and the number of them in proportion to the 
 dimensions of the case, which, in height, should not exceed eight 
 feet. 
 
 There ought to be, properly, another case of smaller dimen- 
 sions, for the reception of such minerals and specimens as may 
 have been subjected to analysis. They should be labelled to 
 correspond with the memoranda of them noted in the record 
 book of the laboratory, as instances frequently arise of a neces- 
 sity of future reference, and hence the policy of this arrangement. 
 The writing-desk, which is the main piece of furniture of this 
 room, should stand against the back wall of the office, as shown 
 in Plate 2 by letter e. Its form and construction are represented 
 by Fig. 7. It is made to occupy as little room as possible, and 
 yet at the same time to possess all the requisite conveniences of 
 an escritoir. The small drawers and cuddies are concealed by a 
 cover or writing flap, which is supported by metal quadrants, and 
 goes up perpendicularly, forming, when closed, a part of the front. 
 
TUB OFFICE THE DRAWING-TABLE. 
 
 27 
 
 Fig. 7. 
 
 The drawers are well adapted for stationery, and the cells for the 
 manuscript papers, notes, letters, &c. The doors in the lower part 
 cover a series of shelves, which may be used as receptacles for accu- 
 mulating papers, which should be filed 
 away in bundles, and indorsed with 
 memoranda of their contents. The 
 sliding flap, as well as the doors 
 beneath, are fitted with locks ; and 
 the desk, when closed, has the ap- 
 pearance of a handsome secretary ; 
 and thus we have the means of pre- 
 serving its privacy during our tem- 
 porary absence from the office. To 
 the right and left of the desk, the 
 
 blank spaces of the side and end walls must be appropriated to 
 shelving for the library. It is better to have them elevated, 
 rather than resting immediately upon the floor. The pedestals 
 may be two feet, and the shelving above, six feet high. The 
 pedestals, or base, should be broader than the shelving above, and 
 may be fitted with deep slats for the reception of charts, diagrams, 
 pamphlets, &c. The upper shelves are to be reserved exclusively 
 for books ; and to protect them from the dust, must be enclosed 
 with curtains, hung as before directed. The position of this 
 shelving is shown in Plate 2 by the letters///. 
 
 The vacant spaces upon the wall above the shelving and cases 
 may be very appropriately used for hanging maps, mounted 
 charts, diagrams, &c., selecting such as are of frequent use for 
 reference. 
 
 The table g l standing midway between the centre and front of 
 the room, is one of the greatest conveniences of the apartment. 
 It combines in its construction the requisites of a drawing-table 
 and chest, a centre-table, and map-stand. Walnut is the most 
 preferable material for this piece of furniture, which should be 
 strongly made, and firmly fastened to the floor by iron clamps 
 and screws. Its superficial dimensions are 4 by 2 feet, and its 
 height 38 inches. The top, of an inch thickness, is a rising flap, 
 and covers a shallow tray, or receptacle for paper, drawing ma- 
 terials, and unfinished drafts. The prop-stick catches in a gra- 
 duated ratchet, indented in the flap, and permits the raising of 
 
28 
 
 BALANCE-ROOM. 
 
 the top to any desired inclination, and renders it available as a 
 
 writing or drawing-desk. By 
 8 - lowering the top, so as to 
 
 make a level table, a flat sup- 
 port is formed for the examina- 
 tion of folios, large drafts, and 
 charts, which require a broad 
 spread and careful usage. 
 The shelving beneath is very 
 convenient for the preserva- 
 tion of this portion of the 
 library, for being of adequate 
 dimensions, the drawings need 
 not, necessarily, be crumpled, 
 in being placed away. 
 A small step-ladder, for convenience in reaching the top 
 shelves of the mineral and book-cases, is very necessary in the 
 office, as well also in the other apartments of the laboratory. 
 
 CHAPTER II. 
 
 THE BALANCE-ROOM. 
 
 THE small room D in the rear of the office, and from which it 
 has been partitioned, has a width of eight feet, and is to be ex- 
 clusively used as the balance-room, and store for metallic appa- 
 ratus. They are thus housed in a close, dry apartment, to 
 preserve them from dampness and injury, and from deleterious 
 exhalations to which they would be exposed in the working-room 
 during the progress of operations. The two balances occupy 
 separate places, and should rest upon solid shelves, firmly fast- 
 ened to brackets set into the wall. These shelves stand imme- 
 diately against the outer side wall, as shown at letters g g in 
 Plate 2. The remaining wall space is fitted with curtained 
 shelves, or, preferably, glass cases, for the reception of the me- 
 tallic and other finer apparatus which require care in their pre- 
 servation. The entrances h h from the office into the main room 
 
THE FURNACE. 29 
 
 are closed with tightly fitting doors, which may be fastened by 
 dead-latches, and should always be kept closed by means of a 
 spring. Their dimensions are 2 feet 10 inches in width, and 7 
 feet height. 
 
 This apartment is also to be kept warm by means of a water- 
 stove placed in the corner or other convenient position. 
 
 CHAPTER III. 
 
 THE FURNACE-ROOM. 
 
 PASSING over the operating-room for the present, we pro- 
 ceed to describe the furnace-room B, which occupies the left 
 wing of the building to the whole depth, without any subdivision 
 for other purposes. Its width is ten feet three inches. In 
 this room are performed all the operations requiring the use of 
 furnaces, stills, and steam, and in their progress generating 
 deleterious fumes, dust, or dirt. It is therefore necessary for 
 the comfort of the chemist, and the preservation of the appa- 
 ratus, to keep the side door z, (7 feet high, and 2-10 wide,) lead- 
 ing into the main apartment, constantly closed. The front of this 
 wing is, as to windows, identical with that of the office. The 
 free admission of light, which is effected by means of the two 
 long front and three elevated side windows, is as requisite in this 
 as in the operating-room. The chimney of this apartment occu- 
 pies the centre of the outer wall, and receives the main flue, fur- 
 nishing draft to the main furnace and two lateral branches. Of 
 these two branch flues, both of which have circular openings, 
 with movable tin stopples, one is for the reception of the smoke- 
 pipe of the still furnace E, and the other for that of the steam 
 generator F ; or, when not in use otherwise, for the portable 
 blast, and other furnaces. These flues are fitted with dampers 
 to regulate the draught; and the circular opening, when not 
 occupied with apparatus, or as vent-holes for the dispersion of 
 noxious vapors, should be kept covered, so as to preserve unim- 
 paired the draught of the main furnace. 
 
 The Furnace. The furnace G, which is in constant use for 
 
30 
 
 THE FURNACE. 
 
 the ordinary operations of the laboratory, o'ccupies the centre of 
 the outer wall. One of simple construction is described by 
 Faraday, to whom we are indebted for drawings, &c. 
 
 " Being in constant requisition as a table, it should be about 
 34 or 35 inches in height. The brickwork should measure 36 
 by 20 inches, and the iron plate, including sand-baths, 40 by 28 
 inches. A warm air chamber may be built in the walls beneath 
 the flue. Projecting spikes should be fastened into one or two 
 sides of this chamber, to hold a temporary shelf when required. 
 
 " Precipitates, filters, and other moist substances put into such 
 a chamber, are readily and safely dried. The hot air causes 
 evaporation of the water, whilst the current removes the rising 
 vapor. The chamber is very useful in effecting the slow evapora- 
 tion of liquids, and also for hot filtrations, when the entering 
 current of air is of a temperature sufficient for the purpose. 
 
 "The principal part of this furnace is necessarily of brick- 
 work, only the top plate with the baths and the front, being of 
 iron. The front is a curved iron plate, having two apertures 
 closed by iron doors, one belonging to the fire-place, and the 
 other to the ash-pit. It is 34 inches high, and 14 inches wide. 
 The ash-hole door moves over the flooring beneath ; the bottom 
 of the fire-place door is 22 inches from the ground, and the door 
 itself is 8 J inches by 7. This front is guarded within at the part 
 which encloses the fire by a strong cast-iron plate, having an 
 opening through it corresponding to the door of the fire-place. 
 
 It has clamps attached to it, 
 
 ^ ; which, when the furnace is 
 
 built up, are enclosed in the 
 brickwork." 
 
 In the setting or building 
 of the furnace, two lateral 
 brick walls are raised on each 
 side the front plate, and a ba-jk 
 wall at such a distance from it 
 as to leave space for the ash- 
 hole and fire-place ; these walls 
 are lined with Welsh lumps, 
 
 where they form the fire-chamber ; two iron bars are inserted in 
 the course of the work to support the loose grate bars in the 
 
THE FURNACE. 31 
 
 usual manner, the grate being raised 19 inches from the 
 ground. The side walls are continued until of the height of 
 the front, and are carried backward from the front in two 
 parallel lines, so as to afford support for the iron plate which is to 
 cover the whole. The back wall of the fire-place is not raised 
 so high as the side walls by six inches and a half, the interval 
 which is left between it and the bottom of the sand-bath, being 
 the commencement of the flue or throat of the furnace. In this 
 way the fire-place, which is fourteen inches from back to front, 
 and nine inches wide, is formed, and also the two sides of the 
 portion of horizontal flue which belongs to the furnace, and is 
 intended to heat the larger sand-bath. The bottom of this part 
 of the flue may be made of brickwork, resting upon bearers laid 
 on the two side walls, or it may be a plate of cast iron resting 
 upon a ledge of the brickwork on each side, and on the top of the 
 wall, which forms the back of the fire-place. When such an ar- 
 rangement is adopted, the plate must not be built into the brick- 
 work, but suffered to lie on the ledges, which are to be made flat 
 and true for the purpose ; for, if attached to the walls, it will, 
 by alternate expansion and contraction, disturb and throw them 
 down. The ends of the side walls, forming as it were the back 
 of the furnace, may be finished either by being carried to the 
 wall against which the furnace is built, or enclosed by a piece of 
 connecting brickwork, to make the whole square and complete ; 
 or a warm air cupboard may be built in the cavity beneath the 
 flue, and the door made to occupy the opening between the walls. 
 Occasionally the flue may be required to descend there, and pass 
 some distance under ground. These points should be arranged 
 and prepared before the plate constituting the top of the furnace 
 is put oh to the brickwork, so that when the plate with its sand- 
 baths are in their places, they may complete the portion of 
 horizontal flue by forming its upper side. 
 
 The size of this plate is the first thing to be considered, and 
 having been determined upon, from a consideration of the situa- 
 tion to be occupied by the furnace, and the places of the sand- 
 baths also having been arranged, the brickwork must then be 
 carried up, so as to correspond with these determinations, and 
 with the plate itself, which in the meantime is to be cast. The 
 sand-baths and the plate are to be formed in separate pieces. 
 
32 THE FURNACE. 
 
 The bath over the fire is best of a circular form, and of such 
 diameter that, when lifted out of its place, it may leave an aper- 
 ture in the plate equal in width to the upper part of the fire-place 
 
 beneath ; so that a still, or 
 - 10 - cast-iron pot, or a set of rings, 
 may be put into its place over 
 the fire. The other sand- 
 bath must be of such a form 
 as to correspond with the 
 shape and size of the flue be- 
 neath. These vessels are to 
 be of cast iron, about three- 
 tenths of an inch thick ; their 
 depth is to be two inches and a half or three inches, and they 
 are to be cast with flanches, so as to rest in the corresponding 
 depressions of the plate, that the level of the junctions may be 
 uniform. This will be understood from the accompanying sec- 
 tion of the furnace, given through the line A B of the view. It 
 is essential that these sand-baths be of such dimensions as to fit 
 very loosely into the apertures in the plate, when cold, a space 
 of the eighth of an inch or more being left all round them, as 
 shown in the section, otherwise, when heated, they will expand 
 so much as entirely to fill the apertures, and even break the 
 plate. The plate itself should be half an inch thick. 
 
 When the plate and its sand-baths are prepared, and the brick- 
 work is ready, the furnace is finished by laying the plate on the 
 brickwork, with a bed of mortar intervening. If the walls are 
 thin, or any peculiarity in their arrangement occasions weakness, 
 they should be bound together, within by cranks built into the 
 work, and without by iron bands. The alternate changes of 
 temperature from high to low, and low to high, to which the fur- 
 nace is constantly subject, renders it liable to mechanical injury, 
 in a degree much surpassing that which would occur to a similar 
 piece of brickwork, always retained nearly at one temperature." 
 The square space enclosed by the fire-place and flues may be 
 converted into an excellent drying or warm air chamber if de- 
 sired. 
 
 Cast iron is the best material for these baths, for, though liable 
 to be cracked when first heated, by their unequal expansion in 
 
THE FURNACE THE SAND-BATHS. 
 
 33 
 
 Fig. 11. 
 
 different parts, they do not warp and assume the irregular and 
 inconvenient shapes that wrought iron acquires under similar 
 circumstances. 
 
 " These baths should have washed sea-sand put into them ; it 
 is heavy, and occasions no dust when moved, whilst, on the con- 
 trary, unwashed and bad sand contains much dirt, and occasions 
 great injury in experimenting. A piece of straightened iron 
 hoop, about twelve inches in length, should lie on the furnace, as 
 an accompaniment to the baths, being a sort of coarse spatula 
 with which to move away the sand. 
 
 " The circular sand-bath is frequently replaced by a set of con- 
 centric iron rings, or a cast-iron pot. 
 The rings are convenient for leaving an 
 aperture over the fire of larger or smaller 
 dimension, according as a smaller or 
 larger number are used at once ; and 
 being bevelled at the edges, fit accu- 
 rately into each other, without any risk 
 of becoming fixed by expansion. The 
 external one, like the sand-baths, should 
 be made smaller than the depression in 
 the furnace plate in which it rests. The 
 iron pots are of various sizes, and are 
 
 adapted to the furnace by means of the rings; a red heat is 
 easily obtained in them for sublimation." 
 
 In many instances, where economy is of prime importance, 
 the foregoing sand-bath may be replaced by an ordinary cylinder 
 stove, the pipe of which leading into a four-sided sheet iron box, 
 divided into flues by partitions, imparts its heat in transitu to 
 the chimney. The top of this box, when covered with sand, 
 forms the sand-bath. That portion of its surface immediately 
 over the first flue, is the hottest. The remote or cooler end, is 
 best adapted for gradual digestions, evaporations, &c. ; and so by 
 these flues there is a means of graduating the temperature of the 
 bath. The top of the stove itself being directly over the fire, 
 makes an excellent bath for those operations requiring a higher 
 temperature ; and by a djusting an outer casing of tin plate to the 
 circumference of the stove, a drying chamber may be formed. 
 
 The steam generator (Fig. 13) when used as a stove for heat- 
 
 3 
 
34 
 
 THE FURNACE- THE HOOD. 
 
 ing the apartment, answers equally well to heat the bath, it being 
 only necessary to conduct its smoke-pipe into the iron box instead 
 of leading it directly into the chimney. 
 
 To prevent contamination of the atmosphere of the apartment, 
 by admixture with the deleterious fumes evolved during the 
 various operations of digestion, fusing, melting, heating, and 
 evaporating in progress upon the sand-bath and in the furnaces, 
 there should be firmly fastened to the ceiling and immediately 
 over its surface, extending beyond its superficies some four inches 
 all around, a sheet-iron hood, of form at the base corresponding 
 with that of the top of the furnace. The barrel of this hood may 
 pass either directly through the ceiling and roof into the atmo- 
 sphere, or else be formed into an elbow, leading into the main flue 
 of the chimney. In either case, the draft must be thorough, so 
 
 as to aiford a free egress of 
 the fumes into the atmosphere 
 without. It should also be 
 immovably fixed by rod iron 
 stretchers, and well payed 
 over with zinc paint. The 
 fixture is represented by Fig. 
 12. It should descend as near 
 to the surface of the bath as 
 convenience of manipulation 
 will allow ; and to prevent 
 any accumulation of dirt in 
 the interior, it should be fre- 
 quently brushed out with a 
 soft brush ; and for protection to the vessels on the sand-bath, 
 against falling particles, the top of the furnace should, during 
 the operation, be covered with paper. It is advisable at all 
 times, independently of the foregoing suggestion, to keep each 
 vessel covered with plates or clean white paper, which, while 
 protecting against dirt, offers no impediment to the processes of 
 evaporation, digestion, &c. If the hood, instead of being fixed, 
 is counterpoised, so as to admit of ready depression or elevation 
 at will, it is a little more convenient ; but that arrangement has 
 the disadvantage of liability to accident, for a carelessness in 
 fastening the suspension cords may create a very annoying da- 
 
THE STEAM GENERATOR. 
 
 35 
 
 Fig. 13. 
 
 mage. Of course, this mode of hanging the hood can only be 
 adopted where the barrel or pipe is straight, and leads directly- 
 through the roof; and then to protect the exit hole from the 
 wear and tear consequent upon the abrasion of its circumference, 
 it should be fitted with an earthenware cylinder ; and further- 
 more, to prevent the entrance of rain through the slight open- 
 ings, there should be a spreading flange around the protruding 
 portion of the barrel of the hood, near the roof. 
 
 Furnace. The air or wind furnace of a laboratory is gene- 
 rally a fixture made of refractory brickwork and iron ; but the 
 Universal Furnace and Barren's Blast Furnace, described in Chap- 
 ter XI, are more convenient portable apparatus, which will serve 
 for all the purposes of the laboratory. 
 
 The Steam Generator. To the right of the furnace, at a 
 convenient distance, is the portable steam generator F, with its 
 smoke pipe leading into the circular opening of the lateral flue 
 opposite. It has a stove-like form, is compact, requires no brick- 
 work, and but very little fuel, and can be set up and removed at 
 will, when it is desired to occupy the 
 flue with other .apparatus. The only 
 fixtures requisite, in addition to the 
 machine, are feed pipes to convey the 
 water, and conduits for the passage of 
 the steam. It is a most convenient ap- 
 paratus for the laboratory, being alike 
 handy for economically supplying hot 
 water to all parts of the building, and 
 for boiling substances, where the direct 
 admission of steam is preferable; and 
 also for heating the steam series in the 
 range a little to its left. This mode of 
 applying heat, having the great advan- 
 tages of safety, convenience, and regu- 
 larity, is absolutely requisite in many 
 cases where the naked fire does not offer 
 that uniformity of temperature which the 
 alterability of certain substances under 
 process renders necessary. Fig. 13 repre- 
 sents the apparatus. By means of coup- 
 ling screws and flexible lead pipe, the steam may be carried to 
 
36 * LABORATORY JACK. 
 
 any reasonable distance in any direction, thus affording great 
 facility in many operations ; as the loss by condensation in thus 
 conveying it is inconsiderable. In very cold apartments, how- 
 ever, when the conduit pipe is of any great length, it may 
 very properly be enveloped with woollen listing or other bad con- 
 ducting materials. The lower cock in the figure connects with 
 the feed pipe. The three smaller cocks above, and placed equi- 
 distant from each other, are try cocks, to ascertain the height of 
 the water, by which its supply must be accordingly regulated. 
 The steam conduits are coupled by a cock fitted to the top of the 
 generator. 
 
 The door in the lower part is for the introduction of the coal 
 into the fire hole. 
 
 For laboratories of public institutions, or for any laboratory 
 which it is desirable should be complete in its arrangement, the 
 better plan will be to combine the generator, sancKbath, and dry- 
 ing chamber in one and the same piece of apparatus. This is 
 done to a certain extent in Beindaff's apparatus, which will here- 
 after be described ; but that implement is only adapted to small 
 operations. We have, therefore, aided by the practical skill of 
 Matthew Y. Forney, engineer, of Baltimore, devised an econo- 
 mical and compact substitute, which is efficient for all the pur- 
 poses of a large laboratory, and may, from its capacity for so 
 many uses, very properly be called the 
 
 Laboratory Jack. It consists wholly of metal, and may be 
 set up like a stove in any position convenient to a chimney flue. 
 This is a saving of all the expensive mason-work of other forms 
 of furnaces now in general use for similar objects, and the 
 arrangement, though simple, comprises all the requisites of such 
 a structure in the minimum of space and over a single fire. 
 
 The apparatus consists of two parts, the frame and the boiler. 
 The first, with the exception of the glass window, is cast in iron, 
 from patterns ; and the latter is made of strong wrought iron 
 plates. It is very essential that all the workmanship shall be 
 exact, for unless the various parts are closely adjusted at the 
 joints, the machine will be wanting in that neatness of appear- 
 ance which otherwise would render it an ornament to the apart- 
 ment. 
 
 The annexed drawings show the apparatus upon a scale of one 
 
LABORATORY JACK. 
 
 37 
 
 twenty-fourth its actual size, Fig. 14 being a front view, Fig. 
 15 a side view, and Figs. 16 and 17 longitudinal and transverse 
 sections. 
 
 Fig. 14. 
 
 For convenience of illustration, we will divide the frame or 
 stand into an upper and lower story. The front and sides of the 
 upper story are formed of sash-work, the rear and top of stiff 
 sheet iron plate ; and this enclosure covers the sand-bath form- 
 ing the top of the lower story. The front window is stationary, 
 but each of those at the sides are hung with counterpoises con- 
 cealed in the corner pillars ; this facility for raising and lowering 
 them being indispensable to prevent damage to vessels in placing 
 them or removing them from the bath. The bath is also ledged 
 around its circumference, with soap-stone slabs of about one 
 inch thickness and six inches width, so as to provide against the 
 breakage of glass or other fragile vessels, in case they should be, 
 temporarily, placed there on being taken from the bath. The 
 durability of that material, its resistance of the action of corro- 
 
88 
 
 LABORATORY JACK. 
 
 Fig. 15. 
 
 sive agents, and limited power of conducting heat, render it mucli 
 more suitable for this purpose than metal. The four slabs form- 
 ing the ledge are so fitted as to present a level and smooth sur- 
 face, in order that the base of the sash may fit closely to it. 
 
 As the emanations from the vessels on the sand-bath are always 
 more or less deleterious, provision is made for their uninterrupted 
 passage into the chimney through a register like the one already 
 described at page 19, and which is set at the top of the rear of the 
 jack, and, by means of a pipe-connection, is made to penetrate 
 into the flue against which the jack is placed. In this way, any 
 accumulation of fumes within the glass enclosure is prevented ; 
 so that, when the windows are raised, as may be necessary, there 
 will be little or none to escape and contaminate the atmosphere 
 
 of the laboratory. 
 
 The lower story consists of 
 the sand-bath, a cylindrical 
 boiler of about 25 gallons' capa- 
 city, with its fire-place and ash- 
 hole in the centre beneath, and 
 spacious drying-chambers at the 
 sides. 
 
 The sand-bath i i is a cast 
 iron box forming the cap of the 
 fire-place b 5, which receives 
 its fuel through the doorway 
 d. The heating-chamber is so 
 planned, that the draught enter- 
 ing at e, Fig. 14, follows the 
 direction of arrows 1 1 until it 
 reaches the extreme end of the 
 boiler, where it divides to rise in 
 two lateral currents, as shown 
 by arrows 2, 2, 2', 2', Fig. 16, 
 and then pass forward through 
 the openings // to the front of 
 the boiler, where they turn into 
 the flue g g. Fom this latter it continues back in the direction 
 of the arrows. 3 3, Fig. 17, to the flue h leading into the chim- 
 ney. This winding course graduates the heat of the bath to 
 
LABORATORY JACK. 
 
 39 
 
 different degrees, the hottest temperature being in that part 
 where the draught first strikes the bottom plate, and the most 
 moderate over the exit flue. The heat of the other portions 
 varies according to proximity or remoteness in regard to these 
 two extreme positions. This multiplicity of temperatures by 
 means of one fire, and always ready for use, will be found a great 
 convenience. A damper for regulating the fire is placed at 5 5, 
 Fig. 17, where the two flues //enter the flue g g. 
 
 The boiler a a, which, as before directed, should be made 
 neatly and strong, is placed below the bottom and centre of the 
 sand-bath, and extends the whole depth of the jack. On the 
 front end is the safety-valve p p, with a side nozzle q for con- 
 necting the distillation and steam-pipe, as will be described 
 directly. Immediately below it are the guage-cocks r r r, for 
 determining the height of water in the boiler ; arid under these, 
 
 Fig. 16. 
 
 again, is the hand-hole s for cleaning the boiler, as may become 
 necessary by the accumulation of deposited matters. 
 
 The boiler, from its position, will be always more or less heated 
 by the fire beneath, which is kept constant, for the purpose of 
 maintaining the heat of the sand-bath during the night as well 
 as the day, so that there may be no interruption to the digestions 
 and other processes in action upon the bath during the absence 
 of the attendant. This circumstance is also made subservient, 
 in the construction of the jack, to a very necessary provision, and 
 that is a continuous supply of distilled and warm waters, and a 
 
40 
 
 LABORATORY JACK. 
 
 regular uninterrupted temperature in the adjacent drying-cham- 
 bers at the sides. When the use of the boiler is to be restricted 
 to these objects, the heat must be kept down ; for which purpose, 
 there is a sliding shelf I I in the fire-place. This, on being 
 drawn forward, as shown in Fig. 17, turns the draught in the 
 direction of the arrows 1 1, and thus intercepts the immediate 
 action of the fire upon the boiler. The shelf is of cast iron : and 
 has a grooved rim for holding in place a soap-stone lining, 
 which is necessary to diminish the conducting power of the 
 metal. As a further means of restricting the heat within the 
 proper degree, there are openings 1 1 for admitting cold air under 
 the boiler ; but as it will be necessary to use steam occasionally, 
 they are fitted with covers for shutting off the current in such cases. 
 The heat obtained as above is sufficient to evaporate the water 
 in the boiler and send it off in the form of vapor, to be con- 
 densed as distilled water ; but, to convert it into steam, the 
 whole force of the fire is requisite. This is applied by pushing 
 the sliding-shelf backwards, so as to close the opening m, Fig. 
 17, and at the same time expose the lower portion of the boiler 
 to the direct action of the fire ; the draught then passing up- 
 wards in the direction of the arrows I 0, through the openings 
 m n, Fig. 17. The fire-place and bottom of the ash-pit are 
 lined with soap-stone, to prevent the burning of the sides and 
 danger from fire to the floor upon which the jack rests. 
 
 The drying-chambers 
 
 Flg ' 17 ' ^^^ j j j j are spacious apart- 
 ments, which derive a con- 
 tinuous warmth from the 
 sides of the adjacent boiler 
 and fire-place ; and the 
 temperature is of a degree 
 most suitable for the drying 
 operations of the labora- 
 tory. They are always ready 
 for use ; and to add to 
 their convenience, the ends 
 are cast with projections 
 at proper intervals, for the 
 support of iron shelves. All of these shelves are movable, and 
 
LABORATORY JACK. 41 
 
 I ' ' ' '' 7 *^ 
 
 some are bored with holes throughout their surface, so as to make 
 the chamber available for large vessels and funnels, as well as for 
 those of smaller dimensions. The doors k Jc afford access to the 
 interior as may be necessary. 
 
 To carry out the design of making this apparatus self-managing 
 as far as possible, the boiler is fed from a suitably adapted 
 reservoir, Fig. 16, in proportion as it loses water by evaporation. 
 The supplies are admitted through the opening v, and the pipe 
 #, connecting with a wooden cistern v v, placed in any con- 
 venient corner of the apartment. This pipe may be, for the 
 sake of protection and convenience, laid under the floor, but, in 
 such case, it will be necessary to wrap it with several layers of 
 woollen listing, or else to imbed it deeply in straw, to prevent 
 freezing in cold weather. The level of the water in the reservoir 
 is kept constantly in adjustment with that in the boiler, by means 
 of the valve-cock w ; and to regulate this cock, there is a hollow 
 ball or float g of sheet-copper. As the level of the water in the 
 reservoir falls, the float of course descends with it, and, in so 
 doing, opens the cock for admission of water from the hydrant, 
 to replace that which passes into the boiler. In like manner, 
 when the original level is restored, the float having risen with it, 
 closes the cock. This arrangement keeps up a supply of water 
 in the boiler as fast as it is diminished by evaporation ; and this 
 affords, at all hours of the day and night, an abundance of dis- 
 tilled and hot waters at little cost, as but one fire is used ; and it 
 is thus made to heat, at the same time, the bath and drying- 
 chambers. 
 
 For technical operations and experiments on an extended scale 
 and requiring the use of steam, the above apparatus will not 
 answer without a supplementary arrangement ; for the pressure 
 of the steam generated in the boiler being greater than that of 
 the external atmosphere, the water in the reservoir will not act 
 alone ; and we have, therefore, provided for a forcing pump. 
 This pump is not shown in the drawings ; but it is of ordinary 
 construction, and worked by the hand. It connects with the 
 pipe x, carrying the water from the reservoir to the boiler. The 
 reservoir derives its supply of water from the hydrant through 
 the service pipe 2, and it should be fitted with a loose cover, 
 which, while keeping out the dust, will allow an occasional in- 
 
42 LABORATORY JACK. 
 
 spection of the cock, as will be necessary to feel assured that it 
 continues in good order. 
 
 The outlet for the distilled water and ste*am is through a tinned 
 gas pipe of an inch diameter, which is attached by a coupling- 
 nut to the nozzle #, projecting from the side of the valve p. 
 This tube rises upwards to the top of the jack, when it is bent 
 outwards and continued in a straight line to the opposite wall, 
 where it is to diverge at angles by means of a T joint. To each 
 end of these angular joints is fitted a stop-cock and connect- 
 ing-pipe, turned interiorly, as above directed. One leads to the 
 steam series, and forms the conduit for serving it and the still 
 with steam ; the other conveys away the vaporized water to the 
 cooling-worm, where it is condensed into distilled water. These 
 two cocks allow the use of either branch, as may be necessary; 
 for when the boiler is generating steam, the cock on the branch 
 leading to the condenser is to be closed, and vice versa, as it can- 
 not be used simultaneously for both purposes. 
 
 The branches conveying the steam should be thickly enveloped 
 with woollen list to prevent loss of heat by radiation. 
 
 The condensing apparatus consists of a block-tin worm and 
 tub, very similar to that described when speaking hereafter upon 
 the STILL. It is placed in a remote corner of the room and upon 
 a high pedestal, so that there may be space beneath for a vessel to 
 receive the distilled water as it trickles from the worm. This re- 
 ceiving-vessel is of blue or white stoneware, free from lead glazing, 
 and made pear-shaped, with a flat bottom, and its narrow mouth 
 kept always protected, by a suitable cover, against entrance of dust 
 or absorption of acid fumes. A glass cock at the bottom is neces- 
 sary for drawing off the water when it is needed for use. The tub 
 is of zinc or galvanized iron, and bevelled at the rim, so as to present 
 a bed or rest for a round-bottom pan, when it is desired to use it 
 as an economical water-bath for large operations. The heat, in 
 such instances, is derived from the water contained in the tub and 
 surrounding the worm, its temperature being always high from 
 the heat radiated by the aqueous vapors passing through the 
 wown, in the act of condensing into distilled water. The water 
 being the condensing medium, must, therefore, be replaced by 
 cold water as fast as it becomes heated, otherwise the condensa- 
 tion of the vapors will be imperfect. To this end, there is a 
 
 i ' '' :; - :;: \ 
 
LABORATORY JACK. 43 
 
 small annular opening near the top of the tub, which connects 
 with an external tube running down the side and out into the 
 gutter. Complementary to this opening is another similar one 
 on the opposite side and connecting with the hydrant, but with 
 its tube passing into the interior of the tub, and down to the 
 bottom. When the hydrant-cock is opened for the admission of 
 cold water into the tub or cooler, the hot water being specifically 
 lightest, rises as the cold water enters below, and flows out at the 
 top through the exit tube. The bottom of this tub is fitted with 
 a cock for drawing off hot water, as may be needed for washing 
 or other purposes. 
 
 By means of this apparatus, one fire is made to heat the sand- 
 bath and drying-chambers, furnish a constant supply of distilled 
 and hot water, and generate steam for the various operations of 
 heating, boiling, distilling, evaporating, &c. Besides these ap- 
 plications, it is capable of being adapted to many other minor 
 purposes, which experience must determine, as it would require 
 too much space to enumerate all its claims to be appreciated as a 
 most serviceable assistant in the work of the laboratory. 
 
 Steam Series. This is a range of implements designed for the 
 nicer technical operations of the laboratory, or for extensive 
 experiments requiring care and an easily manageable temperature 
 below the boiling-point of water. It consists of five pieces, each 
 of which has its appropriate service ; and the whole mounted in a 
 wooden framework rests against the back wall of the apartment, 
 as at / 1, Plate 2. Steam is the heating medium, and the neces- 
 sary supply may be derived from the generator, Fig. 13, or any 
 other form of steam boiler ; but we have designed it, more espe- 
 cially, as an appendix to our jack. 
 
 The great and manifold advantages of heating by steam render 
 the boiler the chief source of heat for the general purposes of the 
 laboratory. In all operations which do not come within its de- 
 gree of temperature, the use of the naked fire must be resorted 
 to, but these cases are comparatively rare, and limited mostly to 
 fusions, ignitions, and certain operations which will be more fully 
 explained in their proper place. 
 
 Fig. 18 presents an intelligible view of the series, each imple- 
 ment being shown in its proper form and position. The first, A, is 
 the still, of ten gallons capacity, and made of tinned copper, or 
 
44 
 
 LABOEATOKY JACK, 
 
 Fig. 18. 
 
LABORATORY JACK. 45 
 
 much better of block tin, about three-sixteenths of an inch thick. 
 It is composed of two separate pieces ; the body or lower part a, 
 and the head or capital 6, the latter being so nicely adjusted to 
 the neck c, of the former, as to make a close joint when the two 
 are put together, as shown in the drawing. Its lower part is en- 
 veloped by a jacket 0, forming a steam chamber of two or three 
 inches space between the inner and outer vessel. The rim of this 
 jacket is a broad flange, serving to support the still by a corre- 
 sponding flange around the circumference of its shoulder, and to 
 make the connection steam tight, the flanges should be interposed 
 with a piece of felt, and tightly bolted by nut-screws or clamps, 
 as shown at p. The steam is introduced into the chamber, at the 
 rear and just below the flange aforesaid, through a wrought pipe 
 2, of three and a quarter inches diameter, branching from the 
 main conduit M ; the stop-cock ?/, in the middle, serving to shut 
 off the current as may be required. Immediately in the bottom 
 centre of the jacket there is a pipe d, leading downwards into a 
 gutter, and fitted with a valve-cock, as a vent for the escape of 
 condensed water and excessive steam. 
 
 To render the still available for distillations at temperatures 
 below steam heat, there is a small circular opening n, through 
 the united flanges, which leads into the steam chamber, and is 
 fitted with a screw-cap for closing it when not in use. This 
 opening or mouth is for the introduction of a funnel, which con- 
 veys water to the interior to form a bath, as may be necessary. 
 Steam being then cautiously let on, the water-bath may be raised 
 to any required temperature below 212 F. The worm and cool- 
 ing-tub for this still are of the same form and material as 
 described for Fig. 20, but their size is necessarily smaller, to 
 correspond with that of the still. 
 
 It is scarcely necessary to remark, that as the mouth of the 
 still body is wide and smooth, it may be used, without the head, 
 as an open vessel, for infusions, evaporations, &c. 
 
 Next to the still is the steam-kettle, B, a double-bottom vessel, 
 the interior of which is tinned copper or block tin, supported in a 
 jacket exactly as described for the still, A. It is of five gallons 
 capacity, and round at the bottom. The branch-pipe, exit-tube, 
 valve-cock, and funnel-hole, have the same relative positions in 
 
46 LABORATORY JACK. 
 
 this piece of apparatus as in the preceding. A cover is provided 
 for boilings which require its use. 
 
 This kettle is particularly adapted for concentrating liquids by 
 evaporation, making solutions of salts in hot water, and similar 
 operations. 
 
 The centre-piece of the series is an iron-bound cedar tub C, 
 of form shown in the drawing. It is of fifteen gallons capacity, 
 and has a hinged cover for keeping out dust and retaining heat and 
 steam vapors, through the back of which the branch-pipe descends 
 into the interior of the tub, and ends at the bottom in a ring, per- 
 forated upon its upper surface with small holes for the better 
 diffusion of the steam. When it is not desired to use wet steam, 
 a close ring may be substituted for the calendered circle of pipe ; 
 and to this end, the upper and lower part of the branch-pipe are 
 made separate, and screw cut at the ends, to be connected when 
 necessary by a coupling-nut immediately below the cover of the 
 tub. This arrangement is necessary for the convenient substi- 
 tution of the open for the close ring, and vice versa. It must be 
 added, however, that in the use of the close ring for a dry heat, 
 proyision is made for the escape of condensed steam into the 
 gutter beneath by passing out the exit end through the side of 
 the tub. , 
 
 This tub is very convenient for making aqueous solutions of 
 the soluble matters of plants, dye-woods, &c., whose active prin- 
 ciples are liable to become altered by direct fire heat. It is, 
 moreover, applicable to boiling purposes generally. A cock near 
 the bottom allows the saturated liquid to be drawn off below, after 
 which, fresh water being added, the boiling may be renewed. 
 These alternate boilings and drainings may be continued indefi- 
 nitely without the necessity of once removing the solid contents 
 of the tub. To the right of the tub is the steam-bath D, which 
 is simply a round-bottom bowl of iron, fitted with an exit-tube 
 and valve-cock in the centre of the bottom, and after the manner 
 directed for the other pieces of the series. The flange serves as 
 a support for the containing vessels, which are set upon the top. 
 To contract the top and adapt it to any size of vessel, there is a 
 series of concentric rings, Fig. 19', made of iron plates, and fitting 
 closely to the flange. The branch-pipe, instead of entering at 
 the top of the jacket, is led in near the bottom, and made, by 
 
LABORATORY JACK. 47 
 
 *r^ i ' 
 
 means of a coupling-nut, to expand in a circle perforated with 
 small holes throughout its upper surface. The steam ascending 
 through these openings in forcible jets, strikes against the bottom 
 of the vessel resting on the flange, and there condensing is rever- 
 berated as water, which finds escape through the valve-cock. This 
 
 Fig. 19. 
 
 steam-bath is alike applicable to porcelain, glass, and metallic 
 vessels, and will be found very convenient for evaporations' in 
 capsules and distillations in glass retorts; it being only necessary, 
 in manipulating with the latter, to fit the ring with a wire basket 
 for its support. The flow of steam must be gentle, else the ves- 
 sel will be forced upwards by the confined steam, and possibly to 
 its damage and that of its contents. 
 
 The last of the series is the stone still E. It is made of blue, 
 salt-glazed stoneware after the form shown by the drawing, s 
 being the body and t the head. Like the tin still, it rests, by a 
 projecting flange around its shoulder, upon the rim or flange p 
 and an iron outer jacket 0, which is fitted with a valve- cock and 
 funnel-tube in the same manner as the other jackets. The stone- 
 ware flange being fragile, when brought in close contact with the 
 iron flange, it is necessary to interpose a piece of lead or thick 
 felt cloth, and to use clamps instead of nut-screws for tightening 
 the connection. The head of the still is movable, but fits closely 
 to the neck m of the body, so that a steam-tight joint may be 
 readily made with the aid of lute. To afford facility for intro- 
 ducing fresh charges without stopping the process or disturbing 
 the tub, there is a stoppered hole v in the head of the still. 
 The form of the head prevents any falling back, into the still, of 
 any distillate which may condense in the former, and sends it all 
 forward through the beak into an adjacent worm of the same ma- 
 
48 
 
 LABORATORY JACK. 
 
 terial as the still, and arranged in a cooling-tub after the manner 
 hereafter described for Fig. 20. The branch-pipe which conveys 
 the steam to the jacket of this still enters, as usual, in the rear 
 and just below the flange ; and it is proper to add, that the cur- 
 rent must be gentle and cautiously regulated, as the stoneware 
 is not capable of resisting as much pressure as metal. This still 
 is used for the distillation of acid mixtures which might act upon 
 metal ; and of ethers and similar substances, which are manage- 
 able with difficulty in glass retorts over the naked fire or sand- 
 baths. Moreover, being measurably free from any liability of 
 breakage, it is adapted to the treatment of larger quantities than 
 could be well operated upon in a glass retort. 
 
 It will be seen, by reference to the drawing, that the branch- 
 pipes proceed, severally, from a single pipe M ; and this latter is 
 of welded wrought iron, and about one and a half inch diameter. 
 It runs along the wall immediately above the series, and derives 
 its supply of steam from the jack or generator, with which it 
 connects by means of a coupling-nut. A cock, G, serves to regu- 
 late the current ; and as the branch-pipes are severally supplied 
 with a cock, it renders each vessel independent of the rest, so 
 that they may be put in operation either singly or collectively. 
 It is proper to add, that on first letting the steam into any one 
 
 Fig. 20. 
 
 of the chambers, care should be taken to open the valve-cock, so 
 as to afford free escape to the confined air. 
 
LABORATORY JACK. 
 
 49 
 
 Fig. 21. 
 
 When the still is to be an independent piece of apparatus, it 
 should be movable, and constructed as hereafter described ; but 
 in those laboratories provided with a jack, the better plan is to 
 make it a permanent fixture, and so arrange it as to make it use- 
 ful either with the naked fire, or a direct current of wet steam 
 from the jack, as the heating medium. Such a system, combin- 
 ing its advantages with those of the steam series and the jack 
 itself, will render the laboratory most conveniently and economi- 
 cally efficient for every branch of chemical pursuit. 
 
 The arrangement best suited to this end, is shown by the fore- 
 going drawing, Fig. 20. The whole is presented in front view, 
 just as it appears when in operation. The brickwork, in which it 
 is set, abuts against the chimney and connects with the flue through 
 the furnace of the still. This furnace, instead of being in front, 
 to inconvenience the operator with its heat and dust, is placed at 
 the side 9r right end, as shown by Fig. 21, the lower door being, 
 the entrance to the ash-pit, and the upper to 
 the furnace or fire-hole. The refrigerant or 
 cooling-tub c, has its position to the left of 
 the brickwork. All the parts are drawn to a 
 scale of one inch to the foot ; and their proper 
 shapes are shown by the figures, to avoid the 
 necessity of elaborate description. 
 
 The lower portion or body of the still 5, 
 is made of heavy sheet copper tinned inte- 
 riorly. The head c is cast, wholly, from pure 
 block tin. Projecting from the interior of 
 the' still, near the bottom, is a tinned copper tube, which passes 
 forwards through the brickwork and ends in a stop-cock fixture, 
 from which rises a glass tube. The cock serves to shut off com- 
 munication between the still and tube, as may be necessary in 
 case of accident to the latter ; and the tube itself, graduated into 
 inches, presents a scale which will at all times indicate the height 
 of liquid in the still. This indicator is protected by a half 
 casing of metal, in which it rests against the front wall of the 
 brickwork, a clamp or two serving to keep it steady. The still 
 has two supplementary parts, one of which is a cullendered lining 
 of block tin, shown by Fig. 22, and the other a perforated false 
 
50 LABORATOKY JACK. 
 
 bottom of the same material. The 
 Fig. 22. firgt is made to fit to the jnouth O f 
 
 the still in such a manner that the 
 same head will adjust with both the 
 inner and outer vessel equally well. 
 The latter is intended as a support for organic 
 or other matters alterable by contact with highly 
 heated surfaces, and is more particularly adapted for distillations 
 with the naked fire. As it may be necessary frequently to re- 
 move this bottom, for the purpose of cleaning it or dispensing 
 with its use in some operations, it is constructed of two parts, 
 connected by hinges in the centre, so as to form a fold which will 
 pass through the mouth of -the still. 
 
 The block tin cullender, shown in the drawing of the still by 
 dotted lines, is designed for use in the distillation of bulky sub- 
 stances, particularly those of vegetable origin, by a direct cur- 
 rent of wet steam. It allows, in a degree, the application of the 
 displacement principle in distillation, for as the current of steam 
 enters, it passes upwards through the holes, thence through the 
 mass of matter supported in the cullender, and the first portion 
 of the distillate reaches the condenser saturated with the volatile 
 parts of the substance under treatment, and without mixture of 
 any, light, solid particles driven over mechanically, as would 
 otherwise be the case. The process effects filtration at the same 
 time that it constantly renews the surface of the solid matter to 
 the solvent action of succeeding relays of fresh steam, while it 
 also affords the means of determining when the former is ex- 
 hausted, and the distillation should be stopped. 
 
 The steam-pipe is introduced through the opening 0, and leads 
 to within an inch of the bottom, where it takes an angular bend 
 and ends in a rose, which is a perforated copper ball with a screw- 
 cut shoulder, by which it is attached to the steam-pipe. The 
 latter is so adjusted in the opening, by means of a shoulder and 
 coupling-nut, as to form a tight joint. When the still is to be 
 used with the naked fire alone, this pipe must be removed, and 
 the opening closed with a screw-plug provided for the purpose. 
 It should be remarked, that .this opening serves also for the en- 
 trance of a funnel-tube through which to introduce fresh addi- 
 tions of liquid as may be required to maintain a supply in the 
 
THE STILL. 51 
 
 still, without the necessity of stopping the operation or removing 
 the head. 
 
 The distillate, in passing from the still-head, goes into the 
 worm firmly fixed in a cooler, c. The worm is a series of block 
 tin tubes, as shown by the dotted lines. The mouth of the first 
 joint receives the beak of the still-head, and that of the last joint 
 empties, through a bent nozzle, into the receiving vessel, gene- 
 rally a glass or stone jar, as seen at d. To facilitate the cleans- 
 ing of the joints, they are fitted at the ends g with screw-plugs, 
 which being removed, allow free access to the interior with a cloth 
 and ramrod. 
 
 The cooler is made of galvanized iron, or, still better, of tinned 
 copper ; and in order to accommodate the long joints of the worm 
 which is soldered to it, its form is oval. The pipe through which 
 it receives cold water is close to the side, and extends nearly to 
 the bottom, as shown at s. A connection with the hydrant is 
 made by a branch-pipe and cock, as shown at m. The opening 
 for the exit of the warm water is seen at #, and leads into another 
 pipe hj running down the outside of the cooler into the drain or 
 gutter. A cock x serves fer draining off sediment as it accumu- 
 lates by deposition from the water. 
 
 We have left the framework or stand open in the drawings for 
 the better exhibition of the different parts of the apparatus ; but 
 in practice it must be closed, so as to circumscribe the radiated 
 heat, which would otherwise escape and be lost. There is, how- 
 ever, a door in front of each vessel to afford access within, as 
 may be necessary for occasional inspection of the valve-cock. 
 
 The description of this apparatus will, itself, afford a fair idea 
 of the great convenience of its several parts. Not the least im- 
 portant of its advantages is the readiness with which the pieces 
 may be adapted to so many uses. Moreover, deriving its steam 
 from the jack, which is always in operation, no fuel or time are 
 wasted in getting it ready for service. It gives, too, an easily 
 manageable heat, and is free from all the objections to a naked 
 fire, particularly in the treatment of many vegetable matters, 
 which are easily altered by the action of the latter. 
 
 When the laboratory is not provided with a jack or steam- 
 generator, then the construction of the still must be somewhat 
 different, and its position may be to the left of the furnace, as at 
 
52 
 
 THE STILL. 
 
 Fig. 24. 
 
 E H, PI. 2. It should combine the double advantage of an adap- 
 tation to the heat of a direct fire, or that of a water-bath ; and 
 to economize room, it must be compact and movable, and there- 
 fore is set in a heavy, stove-like cylinder of sheet iron as a sub- 
 stitute for brickwork. The fire-door is as shown in the figures 
 be'low, and in order to prevent the overheating of the iron cylin- 
 der, the part which contains the fire should be lined with a re- 
 fractory earthen cylinder, of about two inches thickness, as at b 
 and c, in Fig. 24. The smoke-pipe leads into the circular open- 
 ing of the opposite flue. The 
 body of the still rests upon 
 the rim of this furnace at #, 
 by its flange, which surrounds 
 it immediately below its han- 
 dles. It is shown by C, Fig. 
 25. Its dimensions should 
 be so much less than those of 
 the furnace, as to leave suffi- 
 cient heating space around its 
 sides and bottom. The ma- 
 terial of the still is copper, and the joints are rounded so as to 
 
 Fig. 25. Fig. 26. 
 
 give every facility in cleansing. Moreover, round edges are less 
 liable to become bruised than the angular. For the distillation 
 of substances indestructible at high temperatures, this still is ap- 
 plicable over the naked fire, but for more alterable bodies, the 
 intervention of water is necessary, and so, accordingly, an inner 
 tinned copper or enamelled iron jacket is provided. The form 
 
THE STILL. 53 
 
 and position of this jacket are shown at B, by the dotted lines in 
 Fig. 25. It is a straight cylinder with convex bottom, and a 
 broad rim, serving also as a flange or rim for its support in the 
 still. Its dimensions are four inches in diameter and eight inches 
 in depth less than those of the still. The head or capital, which 
 should be of tinned copper, or, preferably, of pewter, is shown 
 at B. The rim is made to fit the mouth of either the still or 
 water-bath, and hence the same head answers in both naked and 
 bath distillations. The beak conveys the vapors accumulating in 
 the capital, into the refrigerant or condenser, which consists of a 
 pewter worm, Fig. 26, encased in a wooden tub kept constantly 
 supplied with cool water through the pipe e. The water-pipe, 
 which carries off the heated water displaced by the cold water, 
 runs from the top of the tub and has its exit into the sink, or 
 through the wall, into the gutter. These two pipes are better of 
 lead. The vapors in passing through the worm are condensed, 
 and drop as a liquid into a receiver, which is placed beneath the 
 outlet pipe near the bottom of the tub. 
 
 To convert the apparatus into a water-bath (for in many dis- 
 tillations the temperature must not exceed the boiling-point of 
 water or a saline solution), it is only necessary to charge the 
 outer jacket, or still, with the proper quantity of liquid, and 
 then to insert the inner casing B, which slides into the mouth 
 and fits tightly. 
 
 In the distillation of flowers, roots, and other substances, in 
 the naked still, a too close contact with its heated sides and 
 bottom renders them liable to injury by scorching, and therefore 
 it is necessary to have a strong wire stand 
 with one or two cullendered shelves upon Fig. 27. 
 
 which to place the material. The lower shelf 
 h being an inch or two from the bottom of the 
 still, prevents all liability of contact between 
 it and the material. This apparatus is shown 
 by Fig. 27. When the still is not in use for 
 its legitimate purpose, by removal of the wire shelving, it be- 
 comes an excellent kettle for any of the ordinary boiling 
 operations. 
 
 In the blank space of the wall to the left of the front entrance, 
 stands a deal wood cask, with wooden spigot, mounted upon a 
 
54 
 
 THE LABORATORY THE SINK. 
 
 stand of convenient height. This serves as a reservoir for dis- 
 tilled water, and the opening in the top, for pouring in the water, 
 must be kept tightly closed to prevent the admission of dust or 
 absorption of gases. 
 
 Fig. 28. 
 
 Beindroffs Apparatus. This utensil, Fig. 28, is not suited for 
 very large operations, but, being compact and convenient in 
 arrangement, will answer admirably for small laboratories. It 
 combines many of the conveniences of the jack, and most of the 
 requisites for general furnace business, such as digesting, distil- 
 ling, macerating, boiling, decocting, dissolving, and evaporating. 
 
THE LABORATORY GAS CHAMBER. 55 
 
 The whole is set in brickwork against a chimney-flue, and occu- 
 pies a space of about four square feet. There is a furnace and 
 grate in the brickwork for heating it by the naked fire when 
 necessary; but there are arrangements, also, for the use of steam. 
 
 The framework is of copper, and constructed so as to act the 
 double part of a boiler and a support for the smaller pieces of 
 apparatus. To this end it is studded throughout with circular 
 openings of different sizes, which are, severally, receptacles for a 
 tinned copper still, a tinned copper evaporating pan, a porcelain 
 and wedgwood capsule, a block tin digesting cup, and two other 
 digesting cups of copper, lined respectively with glass and cop- 
 per. There is also a hole for a steam-funnel for the support 
 of retorts, dishes, &c., when a steam bath is desirable. All 
 these vessels are surrounded by the boiler, which imparts to 
 them its heat ; and a small screw-plug in the top of the boiler 
 serves as a connection for a steam-pipe, as may be desirable. 
 The height of the water in the boiler is indicated by a glass tube 
 properly affixed. A block tin worm or condenser and a cooling- 
 tub are also accompaniments for the still, and to add still more 
 to the efficiency of the apparatus there is a sand-bath on the top 
 and a drying-chamber at the side. 
 
 G-as Chamber. This is a very necessary appointment of every 
 laboratory, as there are many operations which, in > the cold, give 
 off unwholesome vapors that should be excluded from the work- 
 ing apartment, and must, therefore, be conducted under cover; 
 such, for example, as processes requiring the use of sulphuretted 
 hydrogen, carbonic acid, and other gases deleterious in their 
 effects upon the system or discomforting to the operator. The 
 proper arrangement is 'a close framework set into the wall against 
 a chimney-flue, or in such a position that a pipe leading from 
 it may readily communicate with a neighboring flue. A dove- 
 tailed window frame, divided midway by a strong and level shelf, 
 will be appropriate for the purpose. It should have a height of 
 six feet, a width of three feet, and a depth of sixteen inches. 
 Four inches of the depth should be imbedded in the wall, and to 
 insure perfect tightness, the joints should be closed with plaster. 
 The part above the shelf is a common glazed sash hung with 
 counterpoise weights, to afford facility of access and for viewing 
 the interior during the progress of operations, without the neces- 
 
56 
 
 THE LABORATORY THE SINK. 
 
 sity of raising the window. The shelf is the table upon which 
 the apparatus rests when in operation, and immediately below it 
 is a range of small drawers for containing matters pertaining to 
 the business of the chamber. The space beneath the drawers 
 is divided down the centre and fitted with shelves and doors, so 
 as to form a closet for storing the apparatus which may be needed 
 for use in the chamber. The annexed drawing, Pig. 29, presents 
 
 Fig. 29. 
 
 an intelligible view of the structure. It is necessary to add that 
 the noxious emanations find vent as they rise, through a perfo- 
 rated valve let into the chimney after the manner described at 
 p. 19. 
 
 , The Sink. In the corner of the room to the right of the 
 refrigerant, is the sink. Its position will be better understood by 
 reference to I, PI. 2. As it is necessary that the laboratory 
 should be abundantly and constantly supplied with water for 
 cleansing, distilling, and many other operations, it is better, in 
 those cities where the water is supplied by public water-works, to 
 
THE LABORATORY THE SINK. 57 
 
 make an attachment to the main conduit, and lead the water 
 through a lead pipe directly into the laboratory, and immediately 
 over the sink. The only arrangement necessary is a stop-cock 
 at the termination of the pipe, to regulate the flow of water. 
 Fig. 30 represents a sink thus arranged. The trough may be of 
 wood and lined with sheet lead, which metal is preferable to 
 
 Fig. 30. 
 
 Fig. 31. 
 
 zinc, because less liable to corrosion by 
 acids. It would be much better, however, 
 to have it constructed wholly of soap- 
 stone, as this material possesses all the 
 necessary qualities. The floor beneath, 
 to a certain extent around the sink, should 
 also be covered with sheet lead, otherwise 
 its continual dampness from the splash- 
 ing water would endanger the health of 
 the operator. When the introduction of 
 
 water by conduit is impossible, it is necessary to erect immedi- 
 ately over the sink a strong iron-bound oaken reservoir with 
 cover, which must be daily filled with buckets from the neigh- 
 boring pump. In either case, the exit-cock should be fitted with 
 a diaphragm filter, Fig. 31, containing a stratum of crushed 
 quartz, which arrests the suspended impurities of the water 
 during its percolation through. If it is not convenient to pro- 
 vide one of the above filters, an economical but slower and less 
 convenient one can be made of a common red earthenware 
 flower-pot, by covering its bottom interiorly with a linen cloth 
 and filling it with coarse white sand. The waste-pipe, which 
 must be constructed so as to admit of the free discharge of the 
 waste-water, is led, by a gradual descent, into a drain, which 
 conveys its charge into cess-pools or tanks lined with bricks, and 
 sunk into the ground. As the emanations of foul air from these 
 pools are noxious, they should be placed some distance from the 
 building, and kept well covered. If the situation be favorable, 
 the drains should empty themselves into a gutter or some running 
 
58 
 
 THE LABORATORY CLEANSING APPARATUS. 
 
 Fig. 32. 
 
 stream, which, in conducting away the foul matter, would relieve 
 the air of the apartments of its noxious effluvia. 
 
 The mouth of the discharge-pipe must be 
 fitted with a cullendered plug (Fig. 32) to ar- 
 rest the passage of solid matters, which, other- 
 wise, would fall in and prevent the egress of 
 the waste waters. 
 
 As all the cleansing operations are per- 
 formed at the sink, it is necessary that it should be fitted with 
 several shelves, in addition to those which may be arranged by 
 its sides. To afford free escape to the draining water, those 
 
 Fig. 33. 
 
 Fig. 34. 
 
 which are to hold the glass-ware had better be 
 
 cullendered; and upon one, for the safety of the 
 
 test-tubes and other hollow apparatus of too small 
 
 circumference to stand upright alone, there should 
 
 be a series of draining-pins, as shown by Fig; 33. 
 
 A rack of horizontal pegs, for draining retorts and 
 
 other irregular-shaped apparatus, might also be 
 
 conveniently arranged upon a part of the space. 
 
 For draining vials and small flasks, an upright 
 
 stand fitted with pegs, as shown in Fig. 34, is perhaps preferable 
 
 to the horizontal rack. 
 
 A jar of soft and a piece of Castile soap should have appro- 
 priate places in the vicinity of the sink ; and near by also, say 
 on the back of the door, for the sake of economizing room, there 
 must be two long towels hung on rollers, as at Fig. 35. One of 
 these towels is exclusively for the hands, 
 the other for drying the cleansed glass- 
 ware, &c. The other accompaniments to 
 the sink are a coarse towel, a small paint- 
 brush, a bottle of shot, a series of wires, 
 some tow and raw cotton, and a wire in- 
 strument for the removal of corks from 
 
 Fig. 35. 
 
THE LABORATORY CLEANSING APPARATUS, 
 
 59 
 
 Fig. 36. 
 
 O 
 
 the interior of bottles. This latter is nothing more than three 
 plies of stiff wire united together at their upper ends, and bent 
 in angular forms at their lower ends. A hair brush, 
 like that shown by Fig. 36, for cleansing the sides 
 of test tubes and cylindrical vessels, should also be 
 provided. The paint-brush is for washing out wide- 
 mouthed apparatus, and can be well substituted by a 
 mop or twine-brush of similar shape, and much used 
 in housewifery for washing tea-china. These and the 
 cork-wires are to be had at any house-furnishing esta- 
 blishment. 
 
 Of the series of wires, one should be stiff and skewer- 
 like, with pointed end, to remove those particles of dirt, 
 tenaciously adhering to bottles, which have resisted 
 the cleansing action of agitation with sand or gravel. 
 The remaining wires may be of stiff iron and rough- 
 ened, or jagged at the ends, in order the more securely 
 to prevent the slipping of the tow or cotton, which is 
 wrapped and tied thereon to facilitate the cleansing of 
 the glasses. The tow or cotton is to be renewed as 
 frequently as is necessary to cleanliness. A portion 
 of the wires may be from J to J of an inch thick, and 
 16 to 18 inches long. The rest for smaller apparatus 
 may be of proportionably less dimensions. Several 
 long wedge-shaped oaken sticks are also convenient for more 
 effectually applying the cloth or towel, with which they are tem- 
 porarily wrapped, to the angular spaces at the bottom of the 
 glasses. For long tubes, flasks, and deep bottles, a ramrod with 
 its screw end is a most efficient cleansing instrument, as it takes 
 a tight hold of the cotton or cleansing rag and may be very dex- 
 terously handled. All of these pieces of apparatus should have 
 appropriate places near to the sink. Pegs or nails are very con- 
 venient hangers, and two or four cuddies or drawers make ser- 
 viceable receptacles for the tow, cotton, and rags. 
 
 In those situations where it is not convenient to introduce the 
 water through a pipe, there must be erected immediately over 
 the sink a strongly braced shelf, as a support to a closely covered 
 deal-wood cistern for the reception of water. The water is sup- 
 plied either by bucketfuls from a neighboring pump, or else is 
 
60 
 
 THE LABORATORY THE TOOL-CHEST. 
 
 Fig. 37. 
 
 pumped in. In the former case, the position of the sink in the 
 corner, and near to the door, allows great facility in filling it. 
 
 Next to the sink, occupying the inner wall-spaces on either 
 side of the door, as at m m, PL 2, are strong shelving cuddies, 
 racks, and pegs, as receptacles for crucibles, furnaces, iron pots, 
 pans, lead coils, and other apparatus needful in the processes and 
 operations performed in the room. 
 
 The corner shelves K, PL 2, strongly built, are for the re- 
 ception of the larger pieces of apparatus. There should also 
 be reserved a wall space for the still, generator, &c., when out 
 of use. 
 
 The anvil occupying the position L, Plate 2, and resting upon 
 a foot-block, is a most useful implement, and a necessary accom- 
 paniment to the tool-chest, upon the opposite side of the room, 
 at w, PL 2. This tool-chest, which is shown by Fig. 37, com- 
 bines in its construction the 
 conveniences of a work- 
 bench. The vice is affixed 
 towards the end, so as to 
 give full working room. The 
 drawers are receptacles for 
 the requisite tools, among 
 which should be a hammer, 
 
 hatchet, saw, a chisel of each kind, gimlets, awls, files of the 
 various shapes, pincers, a soldering iron, a screw-driver, with an 
 assortment of screws, nails, &c. A glue-pot will also be found a 
 necessary addendum. The bench should be about four feet in 
 length, and of height suitable to the comfort and convenience of 
 the operator. 
 
 The pedestal 0, PL 2, occupying the space between the door 
 and left front window, supports a pear-shaped reservoir of deal- 
 wood, or preferably of blue stone, for the reception of distilled 
 water, a supply of which should be constantly kept on hand. 
 
 A tin match-box, an essential requisite of the furnace-room, 
 should have a dry position in some convenient place upon the 
 wall. 
 
 The charcoal, coke, and sand can either be kept in the cellar, 
 or else in bins occupying the base of the shelving, and resting 
 immediately upon the floor. 
 
H 
 
 
 
THE LABORATORY THE OPERATING-ROOM. 
 
 61 
 
 A solid oaken pedestal for the iron mortar, and several wooden 
 buckets for general convenience, are also necessary pieces of 
 furniture. 
 
 All operations emitting corrosive or disagreeable vapors should 
 be confined, as far as possible, to this room. In passing sulphur- 
 etted hydrogen, chlorine, or sulphurous acid through liquids, the 
 vessels should rest either upon a shelf projecting out of the 
 window, or else under a hood which can carry the emanations 
 into the flues, and thus prevent much corrosion of apparatus and 
 discomfort to the operator. 
 
 CHAPTER IV. 
 
 Fig. 38. 
 
 THE OPERATING-KOOM. 
 
 BETWEEN the office and the furnace-room, and occupying the 
 whole residual floor-space C, PI. 2, of the apartment, is the main 
 operating-room (PI. 1), of dimensions on the plan, 24 by 18-6 
 feet. In this room are performed all the more delicate manipu- 
 lations of analysis and experimental research, and hence the 
 necessity of great cleanliness. The prescribed arrangement 
 frees it entirely from the dust 
 of the coarser operations of the 
 furnace-room (the door of which 
 should be kept constantly closed), 
 while the perforated register, 
 before recommended, and coun- 
 terpoised windows, of adequate 
 dimensions to afford abundant 
 light, promote thorough ventila- 
 tion. In this room is stored 
 nearly all the finer apparatus 
 and materials. The main fea- 
 ture of the apartment is the 
 operating-table, which is shown by Fig. 38. Its position (M, PI. 
 2) is against the front wall-space between the middle and left 
 window. It may be constructed of pine wood, though cherry or 
 
62 THE LABORATORY THE OPERATING-TABLE. 
 
 walnut is preferable. At all events, the top, which must project 
 over all around 2 inches, should be either of these woods or ash, 
 and at least of an inch thickness ; glued at the grooves, and 
 grooved and clamped at the cross-grained end, so as to prevent 
 warping or shrinking, either of which creates a great inconveni- 
 ence to the operator. It is indispensable that the stuff be old, well 
 seasoned and joined, because any shrinking will form cracks and 
 crevices for leakings to penetrate into the drawers beneath, and 
 injure their contents. When the top is made of common wood, 
 it should be covered with india-rubber cloth, drawn tightly over, 
 and fastened under the edges by copper nails. The height of 
 the table proper is 3 feet. Depth 2 feet 4 inches. The length 
 of the top is 5 feet. The shelf-stand or test-case, which slides 
 in grooves, and is fastened to the top of the table by screws, is 
 30 inches in length, and 30 to 32 in height. The distance 
 between the shelving is unequal, in order to accommodate the 
 different sized bottles. The space between the lower and first 
 shelf may be 7J inches, diminishing gradually upward, so that 
 the interval between the top and topmost shelf shall not be 
 greater than 5 inches. The shelves may be of light stuff, say f 
 inch thickness. To protect the bottles from dust, the test-case 
 should have a glass front, hung with counterpoise weights in the 
 manner of a window sash, so as to afford facility in raising and 
 lowering it. The upper drawers should have a depth of 2J 
 inches ; the lower 3 \ inches. The closets below should be fitted, 
 the one on the right, with movable shelves, the other on the left 
 with rows of wooden pegs, obliquely hung. 
 
 All the knobs should be of that kind known as " "White Ar- 
 gillo" both on account of their durability and neat appearance. 
 
 This table thus constructed is the operating-table of the 
 experimenter, and must be furnished with such apparatus and 
 materials as are in constant requisition, and hence the conve- 
 nience of the shelving, drawers, and pegs, as their receptacles. 
 As it is desirable that the table should not be encumbered with 
 apparatus in unnecessary amount, only those pieces which are of 
 constant use, and required to be at hand, should find an abode 
 within the limits of this table. The general supplies of the 
 laboratory are stored elsewhere, as will be directed hereafter. 
 
THE LABORATORY THE OPERATING-TABLE. 
 
 63 
 
 One of the upper drawers should be reserved for filters, of the 
 different kinds of paper used for the purpose. These may be 
 purchased, already cut, and of the different sizes, neatly put up 
 in boxes. If they are made in the laboratory, it is necessary to 
 have a series of circular tins, corresponding with the size of the 
 funnels most in use, by which to shape them. 
 
 Another drawer may be reserved for small tubes, rods, pipettes, 
 and glass or porcelain connections. Another for platinum cru- 
 cibles, spatulas, and fine metallic vessels. 
 
 The small retorts, bulbs, and the like, should also have an 
 appropriate drawer. The larger retorts and glass apparatus find 
 appropriate places in the cupboards. 
 
 The top drawer to the extreme right should be fitted up in 
 desk-form, and furnished with pen, ink, and paper, for the con- 
 venience of making rough notes during operations, which are 
 afterwards to be neatly transcribed in a note-book, or " Record 
 of Laboratory Operations," kept especially for the purpose in 
 an appropriate place in the office desk. The valuable infor- 
 mation which can in this way be stored up, in a short time, 
 amounts to a vast fund, and will serve, to the great convenience 
 of the writer, as a remembrancer of facts acquired and of errors 
 avoided. A coarse towel should always be an accompaniment to 
 this table, and have a hanging position at its side. 
 
 The two lower drawers beneath the closets may be reserved 
 for the more weighty implements. 
 
 A leaden funnel, supported by a wooden casing, with its barrel 
 
 Fig. 39, 
 
 united to a leaden pipe leading through the floor into the street 
 
64 
 
 THE LABORATORY THE SPIRIT-LAMP. 
 
 Fig. 40. 
 
 gutter, and placed immediately to the right of the table, would 
 be very convenient for receiving and conveying off the slops from 
 the test-tubes. When this arrangement is not practicable, a 
 bucket of india-rubber must be substituted ; for the practice of 
 emptying test-tubes upon the floor is slovenly and reprehensible, 
 and by keeping it constantly damp, the comfort of the operator 
 is greatly disturbed. 
 
 A rack with test-tubes, Fig. 39, may be considered one of the 
 fixtures of the operating-table. 
 
 The spirit-lamp which furnishes the 
 heat for table operations, and is shown 
 by Fig. 40, will be spoken of more fully 
 hereafter. When coal gas can be com- 
 manded, it is far more convenient and 
 economical, and by a particular arrange- 
 ment, may be made to yield heat enough 
 for evaporation and ebullition in capsules, 
 and the different operations of digesting 
 in bell glasses, &c. By the use of a large 
 Argand burner fixed over the jet of the 
 table blow-pipe, we can obtain the power 
 of a blast. The admixture of the gas, in 
 this way, with atmospheric air, increases 
 the heat to such an extent as to allow the 
 ignition of precipitates in crucibles, and 
 the accomplishment of many other minor 
 
 operations, which formerly required the use of a furnace. The 
 
 arrangement by which these 
 results are attained, so as to 
 avoid entirely the deposition 
 of carbon on the bottoms of 
 the vessels, is shown by Fig. 
 41. B is a cylinder of sheet 
 copper, stretched over the top 
 of which, and fastened by an 
 iron hoop, is a fine wire gauze, 
 covered with fine gravel to 
 protect it from wear and 
 
 Fig. 41. 
 
THE LABORATORY THE GAS FURNACE. 65 
 
 tear. In order to promote a more thorough admixture of the 
 gas and atmospheric air (which is effected in the chimney), there 
 is a coarse wire gauze diaphragm c. The flexible gas-pipe of 
 vulcanized india-rubber depending from, and connected by a gal- 
 lows screw A, with the permanent hanger 0, terminates in an 
 argand burner d. To prevent a scorching of the table, the 
 burner and cylinder both rest upon a thick metallic foot. The 
 air enters through the openings in the lower circumference, being 
 drawn up by the upward current of gas, which is let on and 
 regulated by the stop-cock r\ and the mixture thus formed 
 passing through the upper fine wire gauze, above which it is 
 ignited, should burn with a bluish flame. 
 
 " Where the quantity of gas is too great for the amount of air 
 admitted, the flame will be white and smoky, but by regulating 
 the supply of gas, the due proportion for a blue flame may be 
 easily attained. To obtain a blue flame from a cylinder of large 
 diameter, a considerable quantity of gas will be requisite, and 
 hence an economical advantage is gained by employing cylinders 
 of different diameters. In the same cylinder, also, where dif- 
 ferent quantities of heat are desired, the lower series of holes 
 may be made large, and a ring of sheet-iron slid over them, by 
 which the quantity of air admitted may be regulated according 
 to the quantity of gas consumed. The cylinders may be 2J to 
 5 inches diameter by 6 8 inches in height ; but by introducing 
 several pieces of coarse gauze <?, at short distances apart, the 
 height may be diminished. The highest amount of heat produced 
 by this apparatus is a cherry-red by daylight. For burning off 
 filters in a platinum crucible, a cylinder of 2J inches diameter is 
 amply sufficient ; but for heating larger vessels, such as capsules, 
 those of 4 5 inches diameter are desirable. This mode of 
 burning the gas presents the advantages of producing any de- 
 gree of heat as high as a red, of not blackening vessels im- 
 mersed in the flame, and of avoiding, with more certainty, the 
 fracture of porcelain or glass vessels, from the diffusive character 
 of the flame." 
 
 The ring n, sliding upon the rod of the upright stand A, 
 serves as a support for a retort, capsule, or crucible. A second 
 chimney g placed over the crucible creates a uniform and constant 
 draught. 
 
66 
 
 THE LABORATORY THE TABLE SAND-BATH. 
 
 Fig. 42. 
 
 Very neat gas furnaces are made by W. F. Shaw, Boston. 
 
 Those for laboratory purposes 
 have a broad base, as shown 
 in the drawing Fig. 42 to 
 steady their position on the 
 table. Surmounting the wire 
 gauze diaphragm is a perforated 
 cylinder, with large openings 
 near its top circumference for 
 the promotion of influent air- 
 currents. These, by perfecting 
 the combustion of the burning 
 mixture of air and gas, not only 
 increase its heating power, but 
 prevent all smoke and odor. It 
 is necessary to add, that the 
 meshes of the wire gauze should 
 be kept clean by the occasional application of a tooth-brush. 
 
 The whole of this apparatus is movable, and when the space 
 which it occupies upon the table is required for other purposes, 
 it is only necessary to disconnect it from the hanger, and place 
 the whole aside, to be as readily replaced again when wanted. 
 
 The introduction of gas into the room also allows the use of a 
 convenient table sand-bath, for certain operations which require 
 the constant supervision of the operator. It consists of a copper 
 
 Fig. 43. 
 
 box B, eighteen inches long, twelve inches wide, and six inches 
 deep. The top, which is ledged, projects over about an inch, 
 and forms the bed for the sand. The door <?, having a small 
 semicircular opening at its base, is for the entrance of the gas 
 
THE LABORATORY THE CENTRE-TABLE. 
 
 6T 
 
 pipe with an argand burner attached, as well also for the supply 
 of air necessary to sustain combustion. The fire thus applied 
 heats the sand on the top. The heated air has an exit through 
 the circular aperture a, after having traversed the interior, which 
 is divided lengthwise by the partition, as represented by the 
 dotted lines. The communication between the apartments is by 
 an opening d, in the diaphragm. In this way we obtain a gradua- 
 tion of the temperature of the bath. The Swedish chemists im- 
 prove upon this construction, by annexing an apartment for dry- 
 ing filters and precipitates as well as for keeping liquids hot while 
 filtering. 
 
 These, with the test-bottles and contents, complete the para- 
 phernalia of the operating-table, and so we proceed to describe 
 the next most important piece of furniture of the room. 
 
 The Centre or General Table. This table (N, PL 2), com- 
 pactly fitted to serve the double purpose of an operating-table 
 
 Fig. 44. 
 
 for distillations, and other large general operations of the labo- 
 ratory which would occupy too much room upon the smaller 
 table, has its top, also of cherry, projecting two inches all 
 around, and grooved, glued, and tightly jointed, as directed for 
 the preceding table, like which, its lower portions may also be of 
 white pine. Its proper position is near the centre of the room, 
 so as to afford free access to all of its sides. Fig. 44 gives a 
 view of it. Its dimensions are 2-10 feet height; 6-6 feet 
 length ; and 3-4 inches breadth. The legs are fitted to a bed, 
 which is to be firmly screwed to the floor, so that the table may 
 
 
68 THE LABORATORY THE CENTRE-TABLE. 
 
 be stationary and firm, as any jarring may create serious damage 
 to a delicately arranged apparatus. 
 
 The drawer space should not exceed 15 inches of the whole 
 height of the table. The end drawers are necessarily, from the 
 construction of the table, very short, and may be omitted en- 
 tirely, though it is better policy to have as many receptacles as 
 possible, for they will all be found useful as well as convenient. 
 
 Of the front drawers, one should be appropriated exclusively 
 to the sheets and other articles of india-rubber. Accompanying 
 these must also be a pair of shears and a ball of very fine linen 
 twine for fashioning and securing joints. Another drawer must 
 be reserved exclusively for the corks of assorted sizes. Two 
 smaller apartments or divisions are also necessary, one for the 
 files of different sizes and shapes, and the other for the cork- 
 presser, and borer, of which more will be said hereafter. 
 
 The stock of filtering paper is also kept in another of these 
 drawers ; and with it, the circular tins by which it is cut into 
 different sized filters. The shears for cutting the paper should 
 be kept always sharp and clean. Another drawer divided into 
 compartments is required for the reception of tow, raw cotton, 
 bladders, string, &c. ; and another for the clean dusters and 
 towels of the establishment. 
 
 The filtering-cloths and material for that purpose are also kept 
 in a separate drawer. The thermometers and hydrometers are 
 likewise kept in a distinct drawer. 
 
 There are many other articles which are better preserved in 
 drawers, and hence there is a necessity for the whole number in 
 the table. The short drawers in the end of the table can be re- 
 served for minor matters, such as the writing-diamond and similar 
 implements. 
 
 The lower bed of the table forms an excellent shelf for the 
 filter-stands, retort-holders, clamps, supports, and other wooden 
 apparatus in frequent use upon the operating-table. 
 
 All the irOn stands and similar apparatus should be painted 
 with black varnish,* in order to preserve them from rust. In 
 
 * To fused asphaltum, 40 ozs. add a half gallon of boiled linseed oil, 6 ozs. 
 each of red lead and litharge, 4 ozs. dried and powdered white copperas. Boil 
 for two hours, then mix in 8 ozs. of fused dark amber gum, and a pint of hot lin- 
 seed oil, and boil again for two hours more. When the mass has thickened, with- 
 draw the heat and thin down with a gallon of turpentine. 
 
THE LABORATORY THE PNEUMATIC OR BLAST TABLE. 
 
 69 
 
 the selection of iron hollow-ware for purposes of ebullition or 
 evaporation, that which is lined with enamel should be preferred, 
 for it is convenient, readily cleansed, and not much more costly 
 than the naked iron ware. 
 
 The mouth blow-pipe table, occupying a position against the 
 front wall, and immediately under the right window, as shown at 
 
 Fig. 45. 
 
 p, PI. 2, is an indispensable piece of apparatus, which will be more 
 fully spoken of under blow-pipe operations. 
 
 The blast or pneumatic table (shown in position at ^, PI. 2), 
 which is sometimes also called the table blow-pipe, may be consi- 
 dered as an implement indispensable to the chemist, it being 
 alike useful for bending glass tubes, blowing bulbs and other small 
 apparatus, and for rapidly effecting the decomposition and igni- 
 tion of substances, which, for their fusion, would require an 
 ordinary wind furnace. The most convenient form of this appa- 
 ratus is shown by Fig. 45. It consists of a brass cylinder piston 
 2, worked by a treadle, which drives the air into a large tin box 
 enclosed in a framework 1, immediately under the top of the 
 table. From the front end of the box a tube rises 
 through the table top, and terminating with its 
 small jet within the interior of an Argand burner, 
 urges the air directly upwards, producing a full 
 flame. The Argand burner may be connected with 
 a lamp or reservoir, containing a solution of oil of turpentine, or 
 alcohol, or with a gas-pipe. In using spirit, the burner must have 
 
 Fig. 46. 
 
70 THE LABORATORY THE AIR-PUMP. 
 
 a circular wick with a contrivance for adjusting its height. Gas, 
 however, when it can be conveniently obtained, is now gene- 
 rally used, on account of the greater power, convenience, and 
 manageableness of its flame. An approved form of Argand 
 burner, for laboratory service, is shown by Fig. 46. Being con- 
 structed with a porcelain cap, the holes through which the gas 
 arises are always clean and free from stoppages by rust or other 
 imperfections incident to metal. 
 
 Air-Pump. The small table at r, PI. 2, is used for the air- 
 pump, which, when not in use, should be kept in an appropriate 
 place in one of the cases in the balance-room. Being a costly 
 apparatus, it is now almost exclusively replaced by syringes, 
 which are more economical and not much less convenient, as 
 made for the purpose at the present time. For the convenience 
 of uniformity, the attachment screws should have a thread similar 
 to that of the stop-cock, so as to admit of a ready adaptation to 
 each other when an attachment is to be effected. 
 
 The Pneumatic Syringe is a very serviceable implement.. It 
 serves for exhausting air from the various forms of vessels in 
 numerous experiments, and particularly from tubes in organic 
 analyses and similar operations. It is also useful in analyses, for 
 evaporations and dryings under an exhausted receiver and over 
 sulphuric acid, or other hygroscopic substance, as will be men- 
 tioned hereafter, under the proper heads, a 4-.^ 
 
 To preserve the efficiency of this piece of apparatus it must be 
 frequently worked, and to prevent leakage at the joints, the 
 latter as well as the piston must be kept well oiled. 
 
 Fig. 47. 
 
 The most convenient form of Pneumatic Syringe is shown in 
 side view and plan by Figs. 47 and 48. When in use, it is fast- 
 
THE LABORATORY THE AIR-PUMP. 71 
 
 ened firmly to the table by means of a screw-clamp made ex- 
 pressly for the purpose. 
 
 The base A, is a solid piece of mahogany, to which the pump 
 arrangement is firmly attached by screws. The barrel B, 9 
 inches long, by 1J inches diameter, is of brass, and carries an 
 air-tight piston, having an ordinary silk valve opening towards 
 the handle L. There is a second valve also at K. A four-way 
 cock C, allows the air to be drawn through either of the nozzles 
 D and E ; and a tube F, connects this cock with the ground glass 
 bed-plate G, which is surmounted by a glass bell receiver H. 
 The edges of the receiver are ground perfectly smooth and flat, 
 and should be greased, so that, when set upon the bed-plate, it 
 may form an air-tight joint. Connection is made between the 
 receiver and atmosphere by means of a cock, I. To this latter 
 there is a screw adjustment for attaching a flexible india-rubber 
 tube in tube manipulations. 
 
 Fig. 48. 
 
 The construction of this instrument is such as to render it not 
 only efficient, but also convenient for general laboratory purposes. 
 Tubes may be connected at either end of the cross-piece D, E, as 
 well as at I; and the bell serves for all the analytic operations of 
 drying and evaporating. 
 
 The table s, PI. 2, to the right of the air-pump, is a stand for 
 the common scales of the laboratory, which are useful for testing 
 the weights of materials purchased and for weighing coarser 
 articles in large quantities. A cheap platform balance with a 
 movable tin dish answers conveniently for this purpose. The 
 accompanying (Avoirdupois) set of weights should range from J 
 oz. to 8 Ibs. 
 
 The next fixtures to be described are the cupboards. Those 
 affixed to the partition of the furnace-room, as at t and u y PL 2, 
 
'' 
 
 72 THE LABORATORY THE CUPBOARDS. 
 
 are more properly shelves, with curtains instead of doors to pro- 
 tect their contents from the dust. The set t may be occupied 
 with the leaden coils, wooden and coarser apparatus of the apart- 
 ment. The curtains of common muslin, rendered fire proof by 
 immersion in a solution of borax and sal ammoniac, and drying, 
 are hung by means of small brass rings upon an iron rod running 
 the whole length of the cap of the shelving ; and in order to keep 
 them distended, leaden bullets should be sewed at occasional dis- 
 tances upon the lower ends. The shelving u ascends to only half 
 the height of that of , because the upper space js to be reserved 
 for racks and rings. The shelves are intended as receptacles for 
 the porcelain capsules, crucibles, &c., the bell, beaker, and other 
 similar glass apparatus, care being always taken to place the 
 larger and heavier articles upon the lower shelves. The tube 
 rack is nothing more than a series of pegs, placed closely adjoin- 
 ing in a straight line and inclining upwards, so as to prevent the 
 tubes from falling through. This open work presents the whole 
 stock of tubing to view at one glance, and enables a ready selection 
 of any particular piece of rod or tube. The smaller pieces which 
 would be apt to fall through, should be kept in a drawer of the 
 centre-table specially appropriated for the purpose. The remain- 
 ing portion of the upper space must be furnished with a series of 
 various sized spikes to hold retort and flask rings. These rings, 
 readily made of wire, vary in size from a half to two or more 
 inches in diameter, and receiving the necks of retorts and other 
 curved or bent apparatus, retain them in a safe and convenient 
 position. The rings may also occupy any small vacancies upon 
 the walls for the use of such a portion of the apparatus as the 
 cupboard cannot contain. 
 
 The small cupboard (v, PI. 2) in the corner opposite, may be 
 used as a sort of general cupboard for very nice little matters, 
 which require great care and cleanliness in their preservation. 
 The door consequently should be fitted with a fastening and kept 
 constantly closed when not in use. 
 
 The cupboards w and x erected against the part'tion opposite, 
 and occupying the spaces on either side of the entrance into the 
 office are, the one x for the stock of drugs and chemicals ; the 
 other w for the new empty bottles, to be confined to the lower 
 shelves, and for the specimens that may from time to time be ac- 
 
THE LABORATORY THE BOTTLEF. 73 
 
 cumulated by the labors of the operator. The. lower half of the 
 cupboard X should be furnished with small drawers similar to a 
 druggist's case. These are for the dye-woods, sulphur, chalk, 
 and other similar coarse articles of stock, which are more securely 
 kept in this way than in bundles, which are liable to rupture and 
 damage by rough handling and by retaining moisture. The 
 upper shelving is to be exclusively occupied with the articles in 
 bottles, which are to be arranged in classes, the compounds of 
 each base forming a class. The mineral and vegetable acids and 
 organic compounds, have also each a separate position. The 
 weightier articles, as elsewhere directed, should always occupy 
 the lower shelves, both for convenience of handling and on ac- 
 count of the greater stability and power of bearing heavier 
 weights than the upper shelves. 
 
 The "black-board," ?/, PL 2, made of artificial slate, is hung 
 sash-like between the uprights of the cupboard w and x, and, 
 being counterbalanced by weights, can be lowered or raised at 
 will, and thus leaves free access to the office. For rough calcu- 
 lations and plans, drafts of apparatus, diagrams, &c., the black- 
 board is very convenient. When a hand-slate is substituted, the 
 pencil should be of talc (French chalk) which makes a more dis- 
 tinct mark than the common slate-pencil, and gives more facility 
 in writing. These pencils are now sold in most of the stationery 
 stores. 
 
 Bottles. Particular regard must be had to the shape and ma- 
 terial of bottles for laboratory use. Those intended for holding 
 acids or salt solutions, must be of well-annealed glass, which is 
 free from lead, and can resist the corrosive action of their con- 
 tents. Some glasses, containing an excess of alkali, gradually 
 lose their brilliancy by absorption of moisture from the atmo- 
 sphere ; others again are attacked by acid and alkaline solu- 
 tions ; and some, indeed, even by prolonged contact with boiling 
 water. 
 
 The inalterability of glass by air or chemical agents (hydro- 
 fluoric acid excepted) is proportional to its hardness and infusi- 
 bility. Flint glass is the most brilliant and comparatively fusible, 
 and its consequent pliability renders it available for thermometer 
 and barometer tubes, but as material for chemical vessels it is 
 far inferior to the Bohemian glass (a silicate of potassa and lime, 
 
74 
 
 THE LABORATORY THE BOTTLES. 
 
 with large traces of alumina), which is harder, lighter, and while 
 possessing many better qualities for chemical ware is, when well 
 made, scarcely less remarkable for beauty than crystal lead glass. 
 Care must be taken in the selection of glass apparatus, espe- 
 cially those which are to serve as implements for reactions, to 
 choose such as are free as possible from striae, knots, or bubbles, 
 defects owing to the imperfect mixture of the materials of the 
 glass. They should have great uniformity throughout both as to 
 material and workmanship. The more transparent the glass, the 
 more readily can the interior cleanliness of the vessel be ascer- 
 tained. The common green glass bottle from the factories of 
 New Jersey, in the absence of better, answers every purpose for 
 the common acids, coarser dry substances, and the solutions of 
 such as are soluble ; and are, moreover, economical. For the 
 reagents and finer chemicals, there is a cheap kind of white 
 glass, free from lead, now manufactured in Philadelphia, and 
 which is well adapted to the purposes, and satisfactorily replaces 
 the elegant, but, at the same time, much more costly imported 
 Bohemian glass. The laboratory series should vary in size from 
 one ounce to one gallon, ranging as follows : 1, 2, 4, 8, 16, 32, 
 64, 128 ounces. The most approved shapes are shown by the 
 cuts below. Fig. 49 represents a wide-mouth bottle for powders 
 
 and crystals. It is short 
 
 Fig. 49. 
 
 Fig. 50. Fig. 51. 
 
 and wide, with round shoul- 
 ders to admit of ready empty- 
 ing and cleansing, and has a 
 strong tall neck for tightly 
 corking. The corks should 
 be perfectly smooth and of 
 the velvet kind. This shape 
 is equally applicable to the 
 bottles of white glass, as is 
 also that of the narrow mouth, 
 glass stoppered, as shown by 
 
 Fig. 51. The narrow necks and their stopples must be accu- 
 rately ground, so as to insure perfect tightness. As the cost of 
 this white glass above mentioned is so very little greater than the 
 Jersey green, it would probably be more advisable to purchase 
 
THE LABORATORY THE BOTTLES. 75 
 
 the whole suite of bottles of such material. The stopples of the 
 narrow-necked bottles are made nearly spherical, but somewhat 
 flattened on the top to project over the mouth so as to protect it 
 from dust. The lips are flat and stout for pouring readily. The 
 wide-mouthed stoppered bottles are, as to body, similar in shape 
 to the above, but their stopple-heads are flattened, and cover 
 both the mouth and the rim. The series of all these bottles con- 
 sists of the sizes above mentioned. For one or two substances 
 both in solid state and solution, which are sensitive to the decom- 
 posing influence of the light, nitrate of silver and protochloride 
 of mercury, for instance, it is necessary that the bottles be either 
 of dark-colored glass, or else covered exteriorly with tin foil. 
 For hydrofluoric acid, a lead or gutta percha bottle is necessary, 
 as glass is decomposed by that body. All solutions should be 
 kept in ground-stoppered bottles ; and if economy is indispen- 
 sable, let the series consist of as many of the green glass bottles 
 as possible, retaining only as many of the white Bohemian glass 
 as are absolutely necessary for the finer reagents. Corked bot- 
 tles are inconvenient and liable to leakage, and their use as per- 
 manent receptacles of liquid should, if possible, be entirely dis- 
 carded. We have consequently not given the shape of a narrow- 
 mouthed unstoppered bottle, though, if they are preferred, the 
 shape of Fig. 51, without the stopper, must be the pattern. 
 
 All bottles with contents must be labelled in full and with sym- 
 bols. This injunction as to labelling applies with equal force to 
 the beaker glass upon the sand-bath and the capsule over the 
 lamp, and to every vessel resting upon the shelves or employed 
 in operations, which contain any substance or solid, whether the 
 material or product of any process. An omission of this pre- 
 caution frequently leads to much confusion, and occasionally to 
 serious errors. Thin writing paper glazed upon one side with a 
 solution of gum tragacanth, and divided into small squares of 
 different dimensions to suit the several sizes of vessels, answers 
 very well for the purpose of labelling operating vessels; but the 
 blue-bordered labels of the shops are much more convenient, and 
 fully as cheap ; their cost being 12 cents per box containing from 
 100 to 500 labels, according to the size of the latter. With a 
 pencil, or more properly pen and ink, the designation may be 
 
76 
 
 THE LABORATORY THE BOTTLES. 
 
 Fig. 52 
 
 written on the label, and thus completed, it is to be pasted on the 
 bottle. For bottles containing the chemicals, materials, &c., 
 these paper squares are equally applicable, but for the test series, 
 upon which the labels are to be permanent, it is better that the 
 names be etched upon the glass by the action of fluohydric acid. 
 Indelible labels may also be made extemporaneously, according 
 to Schubert's suggestion, by writing the letters on paper with 
 a solution of one part of oil of vitriol in six parts of water, dry- 
 ing, and then exposing it to a moderate heat. The written letters 
 being thus partially carbonized, form an indestructible label. 
 
 For writing on glass, Brunnquell proposes the use of a crayon 
 formed by melting together 4 parts of spermaceti, 3 parts of 
 tallow, and 2 parts of wax, and when the whole is fluid, stirring 
 in 6 parts of red lead and 1 part of potash. 
 
 Bottles are now made with indelible names in black enamel, 
 upon a white ground ; and where economy is an object, the annexed 
 
 label (Fig. 52), published by 
 Bullock & Crenshaw, Phila- 
 delphia, from our design, will 
 be found an excellent substi- 
 tute. It expresses the full 
 name of the article, with its 
 symbol ; and, having a carbon 
 ground, will, when varnished with a benzole solution of caout- 
 chouc, present an indestructible surface. 
 
 Let it be a cardinal rule of the laboratory, that no experiment 
 or operation shall be abandoned even for a moment without hav- 
 ing the containing vessels labelled. Those bottles of 
 the test series which are receptacles for acids or other 
 corrosive liquids, wholly or in part volatile, should be 
 provided with ground glass caps. Fig. 53 represents 
 a bottle of this pattern with the label corroded in by 
 fluohydric acid. The mouths of all the test-bottles should 
 have a flange in order to facilitate pouring. The last 
 drop of liquid generally adhering to the lip can be 
 arrested by touching it with the stopple, which catches and 
 reconveys it to the bottle, when returned to the mouth. As 
 there is such frequent annoyance from the obstinate adhesion of 
 
 Chloride Calcium 
 CaCl 
 
THE LABORATORY CLEANSING OF GLASSWARE. 
 
 77 
 
 the stopper in the bottle containing liquor potassce, it would be 
 advisable to have one of the test-bottles constructed specially for 
 holding that substance. The stopper should then be dispensed 
 with, and the neck of the bottle made straight, so that when 
 ground on the exterior to fit a cap like that in Fig. 53, the joint 
 may be tight. A little care in preventing any dripping down 
 the side when pouring from the bottle will always insure an easy 
 removal of the cap, as may be necessary. 
 
 There are other laboratory uses, independent of the aforemen- 
 tioned, to which bottles are applicable. The wide-mouthed, when 
 accurately stoppered and rendered air-tight in the mouth with a 
 little lard or suet, are excellent substitutes for jars, for the re- 
 ception and safe keeping of gases which are soluble in water 
 or corrosive of mercury, and consequently cannot be collected 
 over either. 
 
 Cleansing of Crlassware. When bottles or glassware are greasy, 
 the aid of alkali or ashes is necessary for the removal of the dirt. 
 In open vessels bran or sawdust, by their mechanical action, will 
 cleanse the surface of grease. In either case hot water is a great 
 assistant; and when the laboratory 
 is not provided with a jack or gene- 
 rator, an iron or copper kettle, Fig. 
 54, fitted to the top of a stove or 
 one of the openings in the top of the 
 furnace, is a convenient vessel for 
 furnishing a constant supply. The 
 rinsing afterwards may be with cold 
 water. A short twine brush, similar 
 to that used by housewives for wash- 
 ing tea things, is an excellent assistant in cleansing operations, 
 and there should be several of them about the laboratory. For 
 alkali, lime as an example, which coats the sides, a little common 
 muriatic acid is requisite. When the dirty matter is fixed and 
 resists the purifying action of these two agents, and also of hot 
 water, resort must be had to the use of small round pebbles, or 
 very coarse sand, which, when agitated with a little water in the 
 interior of the bottle, gradually removes the adherent dirt, and 
 can then be rinsed out with clean water. Shot, though much used, 
 are objectionable, as portions of the metal are apt to be left upon 
 
 Fig. 54. 
 
78 THE LABORATORY CLEANSING OF GLASSWARE. 
 
 the sides of the bottle, by abrasion of their surfaces. Careless- 
 ness in leaving behind one or more shot, which frequently secrete 
 themselves in the crease at the bottom, may result in injury to 
 the next contents of the bottle, if it be solvent of metal. The 
 daily ablution of apparatus had better be performed at the close, 
 and after the labors of the day, so that the advantage of the 
 night may be obtained for draining and drying. Retorts and 
 beaked vessels should be ranged on shelves with circular holes 
 for the reception of their beaks. In this case as well also in 
 that of open vessels, the mouths should always be placed down- 
 wards. When it is] necessary to dry the cleansed vessel for im- 
 mediate use, it may be well wiped with a towel exteriorly and 
 then placed upon a moderately heated sand-bath, which will soon 
 expel all internal moisture. Wide-mouthed vessels can be dried 
 with a cloth. For cleansing test-tubes, a goose-feather or stick 
 with a small sponge fastened to its lower end is very convenient ; 
 or, still better, a screw-ramrod. 
 
 The removal of corks from the interior of bottles is effected 
 by an instrument consisting of four strands of iron wire, of 
 about one foot length each, united together at one end, and at 
 the other four extremities bent into an angular shape. Being 
 elastic, there is no impediment to its passage through the mouth 
 of the bottle, in the interior of which it is made, by a dexterous 
 management, to catch and secure the cork, which can then be 
 drawn out with the wire. This simple little instrument is to be 
 purchased at any house-furnishing bazaar. A very convenient 
 substitute is a doubled string ; the loop thus formed, when in- 
 troduced into the bottle, secures the cork and allows its easy ex- 
 traction. 
 
 It not unfrequently happens with ground-stoppered bottles, 
 in cases where certain substances form their contents, that the 
 stopple adheres so firmly as to resist all efforts to remove it with 
 the fingers. It is then necessary to tap it gently and alternately 
 on each side with the handle of a spatula, the spatula being 
 held by the blade, and the bottle, by the top of its stopple, while 
 the body rests on the table. In ordinary cases this process 
 loosens the stopper, but if it fails, it then becomes necessary 
 to carefully expand the neck over the flame of the small spirit- 
 lamp, and in order that it may be uniform, the bottle must 
 
THE LABORATORY THE TEST-CASE. 79 
 
 be kept constantly revolving in a 'horizontal position. When 
 sufficient warmth has been applied, a gentle tapping of the 
 stopple, as above directed, effects its removal. After the neck 
 of the bottle has cooled, it and the stopper must be washed and 
 dried before the latter is returned to its place, otherwise it will 
 soon become tightened again. The plan sometimes adopted of 
 inserting the head of the stopper in a chink and then wrenching 
 it out as it were by turning the bottle with the hand, is not ad- 
 visable, as it endangers the safety of both the vessel and hand. 
 
 When the lamp is used, the motions must be dexterous and 
 careful, so as to confine the heat to the neck of the bottle, for 
 if it is allowed to reach the stopper also, the expansion of both 
 being then equal, the removal of the former cannot be effected. 
 The success of the effort depends upon a difference of tempera- 
 ture between the stopple and the neck which encloses it. Fric- 
 tion, induced by drawing a string constantly, and for a length of 
 time, to and fro around the neck of the bottle, is sometimes sub- 
 stituted for the heat of a lamp. 
 
 When the cementing matter is a crystallized salt, hot water 
 placed around the edges will loosen the stopper by dissolving the 
 salt ; when it is metallic matter, hydrochloric acid is necessary, 
 care being requisite that it does not injure the contents of the 
 bottle. In some cases olive oil, similarly applied, is more effec- 
 tual than either hot water or acid ; and for resins, alcohol is most 
 suitable. 
 
 These remarks are equally applicable to nearly all kinds of 
 closed glass vessels. Broken glass and odd stoppers being often 
 needed for various uses, should be preserved in a box for the pur- 
 pose. 
 
 The Test-case. The bottles of the test-case should be of 
 white glass, entirely free from lead, and accurately fitted with 
 ground stoppers. As they are constantly in use, it is preferable 
 to etch their labels upon the glass. This is readily done by the 
 operator himself, who has only to coat a limited space of the 
 bottle (see Fig. 53) with melted wax, and after tracing thereon, 
 with an iron style, the name and symbol of the reagent to be 
 contained therein, to wet the marks with sulphuric acid, and 
 then sprinkle on some finely-powdered fluoride of calcium (fluor 
 spar). The fluohydric acid thus set free attacks the glass, 
 
80 THE LABORATORY THE TEST SERIES. 
 
 and rendering the latter opaque, makes the lc tters appear distinct, 
 whilst the wax protects the other portion from its action, and when 
 removed, presents the smooth surface of the glass. Care should 
 be taken to avoid inhaling any of the escaping vapor, as it is 
 highly dangerous in its effects upon the sysetm. 
 
 When paper labels are used they must be payed over with a 
 thick coating of insoluble varnish, and written upon with incor- 
 rodible ink. The former consists of white of egg (strained), 
 which is to be applied with a camel's hair pencil, and immediately 
 coagulated by steam heat and then dried in an oven at about 
 212 F. : or it may be a solution of caoutchouc in benzole. The 
 ink is made by dissolving one part of genuine asphaltum in four 
 parts of oil of turpentine, and adding lampblack to render it 
 properly consistent. The neatest method of marking the labels 
 with the ink is by means of a small stamp and types. When the 
 ink has dried, the varnish is to be applied as above, but prefer- 
 ably after the label has been pasted (with gum tragacanth) upon 
 the bottle. The transparent film, hardened and rendered inso- 
 luble by heat, presents a firm resistance to strong acids, alkaline 
 solutions, and other reagents ; and, moreover, this kind of label is 
 economical. 
 
 The test series should consist of ninety-one bottles, all of 
 which are to be kept on the shelf-stand placed on the top of the 
 table in the rear and resting against the wall, as shown at Fig. 
 38. The first ten bottles should be narrow-mouthed and of eight 
 ounces capacity, to contain the following liquids : 
 
 1. Sulphuric acid (pure), . . , ? . S0 3 . 
 
 2. " " (common), . * \ ',' ***** ' *'' S0 3 . 
 
 3. Hydrochloric acid (pure), . . . HCl. 
 
 4. " " (common), '*;,-' j.v HCl. 
 
 5. Nitric acid (pure), J^; . : * ;'. ..-; N0 5 . 
 
 6. " " (common), , .. ^r'"*' < ->- NO 5 . 
 
 7. Aqua ainmonise, % r .*' . . NH^O. 
 
 8. Hydrate of potassa, in solution, . . KO. 
 
 9. Carbonate. of soda, , *V Mi .* : ..' i NaO,C0 2 . 
 10. " ammonia, ; ,v Jk.yji"','--* :. NH 4 0,C0 2 . 
 
 The next division of the series should comprise twelve narrow- 
 mouth bottles, of six ounces capacity, and containing liquids, as 
 follows : 
 
THE LABORATORY THE TEST SERIES. 81 
 
 11. Acetate of lead (neutral), f^f. :> ^*-;. :-V\j . PbO,A~. 
 
 12. Chlorine water, . . -*-'j . . Cl. 
 
 13. Absolute alcohol, , ( .,, , ' *'.' " " . * . C 4 H 6 2 . 
 
 14. Ether, . ._ .. . -."'*' ^.. .; C 4 H 5 0. 
 
 15. Chloroform, ^ . *> . .* ' ,.' ~'- . . C 2 HC1 3 . 
 
 16. Chloride of ammonium, . W . .-<'" . NH 4 Cl. 
 
 17. Oxalate of ammonia, . . - . . NH 4 O.O. 
 
 18. Phosphate of soda,. . .... . 2NaO,PO 5 ,HO. 
 
 19. Chloride of barium, . . . . BaCl. 
 
 20. Sesquichloride of iron, -. f , .- r .' . Fe 2 Cl 3 . 
 
 21. Sulphate of magnesia, . ., . . MgO,SO 3 . 
 
 22. Succinate of ammonia, . -. . . . ' NH 4 O,S 
 
 The third division should consist of sixteen four- ounce, narrow- 
 mouth bottles, containing the following solutions : 
 
 23.; Sulphate of lime, ' . ' '. t " .'' " '. ' ' . . CaO,SO ? . 
 
 24. Sulphite of soda, . . . . .' V" NaO,S0 2 . 
 
 25. Acetic acid, . -..^ .. ".. ' .?< . A(=C 4 H 3 O 3 ). 
 
 26. Oxalic acid, .. ' ' ^ ' /.., , . .: O(=C 2 H 3 ,HO). 
 
 27. Sulphide of ammonium, .^. .. - 'J NH 4 S-|-HS. 
 
 28. Acetate of soda, .. .'; .yV ' . "i Na6,A. 
 
 29. Nitrate of baryta, .;. v * .. .-+ ,. . " .. BaO,N0 5 . 
 
 30. Baryta water, - .. ;. " ..*. ' .. .,: ..<:,' ' BaO+HO. 
 
 31. Chromate of potassa, . . ;, , t -:-. ; . KaO, Cr0 3 . 
 
 32. Sulphate of potassa, >" . ' .. ' \ . KO,S0 3 . 
 
 33. Chloride of calcium, . "; ''J- , ^ . CaCl. 
 
 34. Bicarbonate of potassa, . '*.. ' . % * KO,2C0 2 . 
 
 35. Nitrate of silver, .^' ' . ^ ^ . AgO,NO 5 . 
 
 36. Sulphate of copper, . . jv .",' CuO,S0 3 . 
 
 37. Protochloride of tin, . ... ^, .. . Sn,Cl. 
 
 38. Sulphide of sodium, .. ' . . ' '. ^ ." NaS,HS. 
 
 The fourth division should consist of twelve narrow-mouth 
 bottles of two ounces capacity, and containing liquids, as fol- 
 lows : 
 
 39.Tartaricacid, . -.' .. ^ .' ' . . T(=C 8 H 4 10 ). 
 
 40. Hypermanganate of soda, . ' . . . 
 
 41. Sulphate of alumina, . . / ' : ." ^Y . A1 2 O 3 ,3SO 3 . 
 
 42. Tincture of galls, . . . ... 
 
 43. Bi-tartrate of potassa, . . , r . . KOyZT-fcHO. 
 
 44. Protonitrate of mercury, . . .. . . HgO,N0 5 . 
 
 45. BicMoride of mercury, . < % *^ ; % . . HgCl 2 . 
 
 46. Ferrocyanide of potassium, . . ' ! ' . 2K,Cfy. 
 
 47. Solution of indigo, .- . ; ''*/" . ' 
 
 48. Molybdate of ammonia, . . . . ? 
 
 49. Sulpho-cyanide of potassium, . . -Vi " . K,CyS.,. 
 
 50. Carbazotic acid, . p~ 
 
82 fc: .. THE LABORATORY THE TEST SERIES. 
 
 The fifth division embraces ten reagents, contained in one- 
 ounce, narrow-mouth bottles : 
 
 51. Hydro-fluosilicic acid, .';; .... Si,Fl 2 ,HFl. 
 
 52. Nitrate of nickel, . - ,.' '^': ,. . NiO,NO 5 . 
 
 53. Protonitrate of cobalt, ..... CoO,NO 5 . 
 
 54. Arseniate of ammonia, . . . *%* 3NH 4 0,As0 5 . 
 
 55. Sodio-protochloride of palladium, ... 
 
 56. Bichloride of platinum, . . . . PtCl 2 . 
 
 57. Tefchlorideofgold, . . . .- . AuCl s . 
 
 58. Hydrate of soda, . . . . ,, . NaO. 
 
 59. Antimoniate of potassa, . . . . KO,SbQ 5 . 
 
 60. Cyanide of mercury, . . . . . HgCy. 
 
 The sixth and succeeding divisions comprise solid matters which 
 require wide-mouth bottles. The first ten bottles should be of 
 four-ounce capacity. 
 
 61. Carbonate of lime, . . . .' -.,-' CaO,C0 2 . 
 
 62. " , baryta, . . . " . BaO,CO 2 . 
 
 63. Sulphate of lead, . ."'>.' >!*V ; ^ 'V- PbO,SO 3 . 
 
 64. Sulphuret of iron, . . ". .- FeS. 
 
 65. Bisulphate of potassa, . . . *'*' KO,2S0 3 . 
 
 66. Dry carbonate of soda, .... NaO,C0 2 . 
 
 67. Mixed carbonate of soda and potassa (dry), . NaO,CO 2 -4-KO,C0 2 . 
 
 68. Pulverized charcoal, .... C. 
 
 69. Granulated zinc, . . . . . . Zn. 
 
 70. Nitrate of potassa, . . . . - KO,N0 5 . 
 
 The seventh division should comprise nine two-ounce bottles. 
 
 71. Fluoride of barium, . . .', r r .\ 
 
 72. Chlorate of potassa, . . . /* KO,Cl0 5 . 
 
 73. Copper wire clippings, . . " . . ^^. l , Cu... 
 
 74. Iron wire clippings, . . ' ,% . . Fe. 
 
 75. Cyanide of potassium, s- m . . . . KCy. 
 
 76. Dry carbonate of potassa, .... KO,CO a . 
 
 77. Starch paste, . . . . . 
 
 78. Hydrated teroxide of bismuth, . . . Bi0 3 ,HO. 
 
 79. Oxide of lead, .. - . . " > . . PbO. 
 
 The eighth division should consist of twelve one-ounce bottles. 
 
 80. Iodide of potassium, . . : s , KI. 
 
 81. Ferri-cyanide of potassium, . . 3K,2Cfy. 
 
 82. Biborate of soda, . . .' . NaO,2B0 3 . 
 
 83. Oxide of barium, . . v * BaO,HO. 
 
 84. Nitro-prusside of sodium, ". . Fe 2 Cy 5 ,N0 2 ,Na 2 + 4HO. 
 
 85. Peroxide of mercury, . . HgO 2 . 
 
 86. Phosphate of soda and ammonia, . . HO,NH 4 0,NaOP0 5 +8HO. 
 
THE LABORATORY THE TEST SERIES. 83 
 
 87. Blue litmus paper, ,- *.'*<* *,-> : --M* r *' 
 
 88. Red " ; .; r ^ ,.,- -, ,, , , 
 
 89. Turmeric " J, ^ '. "V ' 'V' , ? 
 
 90. Georgina " . ' . . ;.." .' ; * 
 
 91. Lead 
 
 A leaden or gutta-percha bottle, with a closely fitting stopper, 
 and of two ounces capacity, for the fluohydric (HF) acid, com- 
 pletes the series. 
 
 All these bottles should be made heavy, for if too thin, being 
 so frequently handled, they are liable t& be broken. Of the 
 preceding numbers, 1, 2, 3, 4, 5, 6, . 7, 8, 14, 27, should be 
 furnished with ground glass caps, as shown by Fig. 53. No. 
 35 must be of dark glass, or else covered exteriorly with black 
 paper. Nos. 87, 88, 89, 90, 91, should always be accompanied 
 with a pair of pincers with platinum points, similar to those 
 used in blowpipe operations, as the test papers should never 
 be handled with the fingers. The bottles for alcohol (C 4 H 6 2 ) 
 and distilled water (HO) may be of common green glass, narrow- 
 mouthed, and quart-size. They are fitted with double tubes so 
 as to admit the air gradually, and thus promote a gentle flow of 
 the liquid from them, in the act of pouring ; and are designed as 
 conveniences to the operating-table, for supplying small quanti- 
 ties of their contents to test tubes and narrow-mouthed vessels 
 without the aid of a funnel. Fig. 55 shows their form and ar- 
 rangement. 
 
 A piece of bright copper, and one of iron, are also frequently 
 needed as reagents. 
 
 All of the forenamed reagents must be chemically 
 pure, as also the water used in making solutions of 
 them. 
 
 The reservoir for distilled water should be a 
 close jar of blue stoneware or white iron stone 
 china, the glazing of which is free from lead ; and 
 it must have a glass cock near the bottom through 
 which to draw off supplies for use, as may be re- 
 quired. 
 
 Besides the reagents, a small stock of which 
 should always be kept in reserve on the shelves of the cupboard, 
 there is required a general assortment of drugs and chemicals in 
 
84 THE LABORATORY. 
 
 limited quantity. The coarser and cheaper articles of this stock 
 should preferably be purchased from the dealers, but it is advi- 
 sable for the operator to prepare the costlier ones for himself, 
 not only on the score of economy, but also because of the prac- 
 tice which he will acquire in the manipulations of various pro- 
 cesses. 
 
 There remain but few points to be remarked upon before 
 closing our chapters upon the laboratory. We have already en- 
 joined upon the experimenter great cleanliness, and we now re- 
 peat the injunction. The hands should always be free from dirt, 
 and invariably washed with castile or palm soap before going to 
 meals. This precaution is absolutely necessary on account of 
 health, for otherwise, in working with deleterious matters, the 
 minute particles which secrete themselves under and around the 
 finger nails, may be conveyed into the system, and thereto work 
 an injury. So, also, when engaged at one time upon several 
 operations of a different nature, it is necessary to rinse the hands 
 in passing from the management of one to that of another of 
 them. For this purpose, the hydrant or reservoir with its ad- 
 joining hand-towel, Fig. 30, ia very convenient. 
 
 To protect the person from dirt, the operator should provide 
 himself with a suitable costume. A long wrapper of linsey or 
 baize for winter, and of Holland linen for summer, is very suit- 
 able. A light cap of some cheap material, is a good shield to 
 the hair against the bad effects of dust and vapor. 
 
 In all investigations, the practice of working upon small quan- 
 tities will lead to habits of nice and delicate manipulation. Be- 
 sides, it is easier, less costly and fatiguing to manage a small 
 portion of any substance. 
 
 There are three blank books requisite in every laboratory. 
 The first may be called the Laboratory Record, as it is de- 
 signed to contain full notes of the progress of every experiment 
 and operation going on in the laboratory. In this way, a large 
 store of valuable facts is preserved for future reference. The 
 second book is the Record of Analyses, in which are transcribed 
 the results of analyses of such substances as may have undergone 
 examination in the laboratory. The mode of analysis may also 
 be included. This record is also very useful for future reference. 
 The other book is an "Index rerum," after the plan of the Rev. 
 
INDEX RERUM. 85 
 
 J. Todd, author of the Student's Manual. As it is impossible 
 to retain all that one reads, and much heing valuable, some other 
 means more practicable and less laborious than copying out ex- 
 tracts must be adopted for preserving its remembrance. Mr. Todd 
 recommends the habit of making an index rerum in reading. 
 This book consists of several quires of blank sheets, letter form, 
 and is alphabetically classified, so as to exhibit at a glance, the 
 name of the book and the number of the page treating of the 
 subject, the synopsis of which is recorded under its appropriate 
 letter and heading. Such a digest of journals and books, though 
 very meagre, will still present their notable points, and prove an 
 all-sufficient key, when making researches in the future upon any 
 subject about which it is desired to have all existing information. 
 Always, as Mr. Todd directs, have your index at hand when read- 
 ing book, journal, pamphlet, or newspaper ; and " when you meet 
 with anything of interest, note it down, the subject, the book, the 
 volume, and the page ; and make your index according to sub- 
 jects as much as possible, selecting that word for the margin 
 which conveys the best idea of the subject," so, that there may 
 be no difficulty in finding the original place when it is necessary 
 to refer to it. The following are a few examples of the manner 
 in which the digests should be recorded : 
 
 A 1 New theory of their constitution, by James C. Booth, 
 
 ACIDS FATTY. J Journal of the Franklin Institute for 1848. 
 
 I Investigation of the properties of, by M. Payen, Chem. 
 GUTTA-PERCHA, j Gaz. 1852, p. 176. 
 
 I New mode of making, with Silica and Sodium, by St. 
 SILICIUM. j Clair Deville, Comptes Rendus, 1855, p. 1053. 
 
 There are many other minutiae that might be mentioned, but 
 for want of room for more important matter ; and so we leave 
 them to be suggested by experience. 
 
 Habits of industry, close observation, and neatness, are in- 
 dispensable to the acquisition of skill in manipulating, and without 
 them it will be difficult to become an accurate chemist. 
 
 The laboratory which we have described, is well appointed for 
 every branch of research. Many of the implements enumerated 
 
86 DIVISION OF SUBSTANCES. 
 
 may be dispensed with for ordinary operations, but they are 
 requisite for a complete arrangement, which, as given in the pre- 
 ceding chapters, is not at all extravagant. Moreover, with a 
 little extra industry, the operator can soon realize the outlay for 
 all conveniences, in the manufacture and sale of such pure chemi- 
 cals as may be in demand. We have provided him with every 
 appliance for the purpose, so that his self-improvement may be 
 attended also with pecuniary profit. 
 
 Where the means are limited, it is better that the purchase of 
 apparatus should be gradual, commencing with those pieces which 
 are of most general use. This course judiciously carried out, 
 will in time secure a well-stored laboratory. All stock and appa- 
 ratus can be bought from the manufacturer, or importer, at very 
 little over one-half the dealer's prices, for the same articles. 
 
 CHAPTER IV. 
 
 DIVISION OF SUBSTANCES. 
 
 THIS operation is a mechanical process, by which the surface 
 and points of contact of solid bodies are multiplied ; thus dimi- 
 nishing, in a high degree, the opposing force of cohesion, and, 
 consequently, by promoting greater access to its particles, en- 
 abling the more ready and rapid action of reagents upon solid 
 matter. 
 
 The means by which the division of solid matters is accom- 
 plished are manifold, and vary with the nature of the substance 
 to be reduced ; some bodies being pulverizable by almost any of 
 the processes, while others again require a particular method for 
 their reduction. The different modes of operating may be classi- 
 fied as follows : 
 
 1st. Slicing. This process applies to fibrous matters, and is 
 practised with a spring lever-knife, similar to that used by to- 
 bacconists for cutting tobacco, and shown by Fig. 56. 
 
 Being thus reduced to thin slices, the substance is in better 
 form for maceration, &c. ; and, moreover, admits of readier desic- 
 
CRUSHING. 
 
 87 
 
 cation, a necessary process when it is required to be further 
 reduced under the pestle, or by being grated on a coarse rasp. 
 
 Fig. 56. 
 
 This mode of pulverization by rasping, though particularly 
 applicable to fibrous substances, such as fresh roots and the like, 
 is sometimes used for metals and hard matters. In the latter 
 case, the files must have finer and sharper teeth, and in both 
 instances be perfectly clean, and free from grease and dust. 
 
 Fig. 57. 
 
 2d. OwsAw#. Fresh roots and juicy vegetable matters of a 
 tough, stalky, and fibrous nature, which are not required to be 
 reduced under the knife, may be better prepared for the action 
 of solvents or the press, by being crushed under the pestle in a 
 common mortar. As this mode, however, is very tedious, and 
 . 
 
 .- 
 
88 
 
 CRUSHING. 
 
 inapplicable even to moderately large quantities, it is best to use 
 a machine -which has been devised for the purpose bj Coffey. 
 It is shown, in section and elevation, by Figs. 57, 58, and consists 
 a cast iron frame F F, on which is set a pair of hard wooden 
 rollers revolving towards each other, and fed from a hopper C 
 with the material to be crushed. The latter, as it passes through 
 
 Fig. 58. 
 
 the rollers, falls into a receiver D beneath. The gearing com- 
 prises a fly-wheel G, a spur-wheel H, and the cog-wheels 1 1. 
 Being put in motion by turning the handle, which, however, re- 
 quires considerable power, the rollers draw the material through, 
 and drop it in the reseiver in a thorough state of contusion. It 
 must be mentioned, however, that some tough substances require 
 to be passed through the rollers several times before they become 
 thoroughly crushed; and for such cases, the wheels B B, com- 
 municating with the rollers, serve to regulate the distance between 
 the two, as may be necessary for widening it at the first step, 
 and closing at the final operation. In this way, the hard as well 
 as the soft parts of the substance become uniformly crushed; and, 
 the crushed matter may be pressed, without passing any sus- 
 pended particles of woody fibre with the juice. 
 
PULVERIZATION. 89 
 
 3d. Pulverization. In order to obtain a minute division of 
 the denser substances, whose particles are very cohesive, resort 
 must be had to the pestle and mortar. The material of this ap- 
 paratus varies with the nature of the substance to be powdered. 
 To prevent errors, corrosive or caustic matter should never be 
 pulverized in metallic mortars, else by a solution of a portion, or 
 contamination with abraded particles, unavoidable confusion will 
 ensue. The resistant nature of the material of the mortar must 
 be proportional to the hardness of the body to be operated upon. 
 For the harder insoluble substances, those of iron, or steel, 
 are generally used. For the less dense and more pulverizable 
 bodies, especially those which are acid, or corrosive, porcelain, 
 wedgwood, or glass, is the proper material. Marble, being 
 readily attacked by acids, mortars of that material are only used 
 for reducing those inert substances which are readily comminuted 
 merely by trituration, such as chalk, neutral salts, &c. This 
 material, as well as glass, is well replaced by porcelain or wedg- 
 wood, which are stronger, and otherwise much less objectionable. 
 There should be an assorted series of mortars for laboratory 
 purposes. 
 
 The large iron mortar has its position in the furnace-room, and 
 is permanently and firmly fitted upon ,an upright block of hard 
 wood, Fig. 59, in some convenient place, for general use, in 
 pounding ores, metals, and coarser substances. The pestle of 
 this, as .of all other mortars, should invariably be of one piece 
 and of the same material as the mortar ; because, when the lower 
 part is fitted to a handle, it is apt to become loosened and drop 
 off particles of the cement with which it is fastened, to the injury 
 of the contents of the mortar. The handle or upper portion must 
 afford convenient space for grasping, and the base or lower por- 
 tion, roughened on its face by use of sand, should diverge to a 
 diameter of about one-fourth of that of the mouth of the mortar. 
 Fig. 60 exhibits a mortar of proper form and proportionate thick- 
 ness as to its different parts. Its interior form is nearly that of 
 the butt end of an egg, so as to promote a constant contact of the 
 matters under process, with the rotating pestle. To prevent the 
 ejection of particles of matter or the escape of dust, and conse- 
 quent inconvenience to the operator, as the case may be, the 
 mortar should be provided with a sheep-skin conical coverlet, 
 
90 
 
 MORTARS. 
 
 Fig. 59. 
 
 with a hole in its centre for the passage of the pestle, which is to 
 
 be fastened around its rim and 
 over its mouth, with a string. 
 Circular pasteboard and wooden 
 covers, of eizes corresponding 
 with the mortars and with a 
 hole in their centres, are often 
 substituted for the conical co- 
 verlet. The operator should 
 always stand with his back to a 
 current of air; and to further 
 guard against the unpleasant or 
 deleterious effects of the fine 
 dusty particles which may arise 
 from the mortar, he can moisten 
 
 Fig. 60. 
 
 its contents with a little water, provided that liquid is without 
 action upon the substance. Exposure to warmth, for the evapo- 
 ration of the water, will restore the matter to its original dryness. 
 
 All substances formed of an organic tissue should be previously 
 dried, so as to afford greater facility in their pulverization, but 
 care must be observed to avoid a heat sufficiently high to injure 
 their properties. A previous reduction of ores, and coarse hard 
 substances into lump, by concussion with a hammer upon an 
 anvil, and of roots and the like into slices or bits with a common 
 knife or lever-cutter (Fig. 56), are preliminary processes which 
 greatly facilitate their pulverization. The substance to be struck 
 upon the anvil should be previously wrapped in strong brown 
 paper. 
 
 Silicious stones pulverize much more readily after having been 
 
MORTARS. 
 
 91 
 
 heated to redness in a crucible, and in that state projected into 
 cold water. This increased friability is occasioned by the unequal 
 cooling of the mass. 
 
 Metals, alloys, and the like, which are difficultly pulverizable 
 whilst cold, may also be readily crushed when heated to redness. 
 
 When it is required to reduce the substance into small frag- 
 ments only, it can be broken down by a succession of blows with 
 the pestle. If the substance is very hard, the foroe of the arm 
 should be added to the descending weight of the pestle, so as to 
 impart power to the blow. A subsequent circular grinding mo- 
 tion of the pestle, continued for a length of time, will further 
 reduce these fragments to fine powder, and consequently this 
 movement must be avoided when only a coarse comminution is 
 desired. The mortar must always rest upon a solid foundation, 
 and during the operation of pounding should be occasionally 
 shaken, in order that the coarser particles which mount to the 
 sides may be forced back to the centre of the mortar, so as to 
 receive the full effects of the descending pestle, which should 
 never be allowed to strike the sides of the mortar. If the sub- 
 stance is to be reduced to a fine powder, the process is greatly 
 facilitated by operating upon only a small portion at a time, as 
 the pestle is less liable to become clogged. 
 
 In the analysis of rare minerals, especially those which are 
 
 Fig. 61. 
 
 very hard, the reduction is effected in a small mortar of hardened 
 steel. This apparatus, shown by Fig. 61, consists of three sepa- 
 rable pieces, each of which is smoothly turned, so as to present 
 
92 TEITURATION. 
 
 an even surface exteriorly and interiorly. C is the base piece, 
 into the cavity of which the cylinder B fits somewhat loosely. 
 It is this cylinder which receives the mineral to be reduced. 
 Sliding into it is the exactly fitting pestle A, which being struck 
 successively with a hammer, crushes the mineral to powder with- 
 out waste of any of its particles by ejection. 
 
 When the powder thus obtained is not yet sufficiently fine for 
 analysis, it must be transferred to an agate mortar, and rubbed 
 with the pestle until reduced to an impalpable state. The pestle 
 and mortar are of the same material, the hardness and smooth- 
 ness of which render it particularly applicable for the purpose. 
 The motion of the pestle should always be circular, otherwise a 
 perpendicular blow may endanger the safety of the mortar, espe- 
 cially if it has a fissure, as is often the case, running through it. 
 The given weight of the mineral for analysis must always be esti- 
 mated after pulverization ; never previously, lest a loss by ejec- 
 tion, or adhesion to the mortar or spatula, may lead to inexact 
 results. Fig. 62 exhibits an agate mortar, which 
 Fig. 62. can j^ p urc hased of sizes varying from 1 to 6 
 inches in diameter. One of about 3J inches width 
 will be most useful. It should be selected as free 
 from indentations, fissures, or cavities as possible, 
 for these faults not only impair the durability of 
 the mortar, but render its cleansing very difficult. An excellent 
 plan of removing tenaciously adhering matter from the sides or 
 bottom of a mortar, is to rub them with pumice-stone and water. 
 4th. Trituration. This mode of manipulating with the pestle 
 is application to those substances which are friable, and fall to 
 powder by being merely rubbed up by a circular or grinding 
 motion of the pestle, and which would soften and become obsti- 
 nate by being pounded. Chalk and the like, and most of the 
 salts, are in the first category ; the resins and gum-resins in the 
 second. 
 
 Sand is added to facilitate the reduction of resins and similar 
 substances, which cake under the pestle, only when they are in- 
 tended for maceration or solution. Under other circumstances, 
 the medium would be an adulterant on account of the impossibility 
 of separating it. 
 
 The proper material for a mortar for this purpose is white 
 
TRITURATION. 93 
 
 wedgwood, of form as shown by Fig. 63. Berlin porcelain 
 mortars, glazed outside and biscuit internally, with broad-butted, 
 solid pestles, as shown at Fig. 64, are neat and convenient im- 
 plements, but less available for general purposes than those of 
 
 Fig. 63. Fig. 64. 
 
 wedgwood, which are stronger, more durable, and will stand 
 harder blows. These are purchased by the diametrical inch, and 
 the most convenient size is 6 to 8 inches width at the mouth. It 
 will be well also to have a smaller one of the same material, say 
 of 2 inches diameter at the top. 
 
 Fig. 65. 
 
 Hewitt proposes to reduce the amount of labor and time re- 
 quired in the use of mortars, by the substitution of machinery ; 
 
94 
 
 TRITURATION. 
 
 and to this end, has presented an ingenious invention, Fig. 65, 
 which imitates exactly the rotating motion given to the pestle by 
 the hand. The weight of the pestle of this machine is 12 to 14 
 pounds, and its gearing and action are intelligibly expressed by 
 the drawing. 
 
 It is said to require very little power, and that only from the 
 hand. Aloes, cantharides, and similar substances, are reduced to 
 fine powder, by its means, with great promptness; moreover, it 
 moves noiselessly, and does not scatter dust. 
 
 Another machine, of similar purport, but of more extended ap- 
 plication than the above, both as regards the varieties of sub- 
 stances and the quantities which may be operated upon, is that 
 known as Goodall's grinding and levigating apparatus, shown by 
 Fig. 66. In this, as in the former invention, the pestle acts 
 
 Fig. 66. 
 
 from a motion similar to that imparted by the hand ; and as it 
 traverses a different surface each rotation, no scrapers are re- 
 quired to keep the powder constantly under action. Steam- 
 power increases the efficiency of the apparatus; but it acts 
 readily with hand-power, even upon the hardest substances. 
 

 PORPHYRIZATION. 95 
 
 A weighted lever secures the pestle at the top, and the gearing 
 from which it derives motion is driven by a bevel-toothed cog- 
 wheel on the main driving-shaft, which is provided with a winch- 
 handle. The mortar is placed in front, to be wholly out of the 
 way of falling dust and dirt from the moving wheels and other 
 parts of the machinery. 
 
 The pestle being attached to the driving-shaft by a screw can 
 be removed as may be required. 
 
 5th. Porphyrization. This mode of pulverizing, only em- 
 ployed when it is required to reduce the powder to the greatest 
 fineness, takes its name from that of the material of the vessels 
 in which it is practised. A small porphyry mortar, hemispheri- 
 cal interiorly, or, preferably, a slab and muller, is the apparatus 
 employed. Flint, and even glass, which are equally as hard as 
 porphyry, form an economical substitute for that material. It is 
 highly important that the material of the apparatus shall be less 
 easily abraded than the substance being ground ; for if too soft, 
 the latter becomes contaminated with the particles which are 
 rubbed off, and, hence, in exact investigations, inaccuracy is 
 occasioned. 
 
 Porphyrization is generally effected by rubbing the coarse 
 powder between a flat slab and muller, until reduced to an im- 
 palpable state. The circular motion of the muller disperses the 
 powder over the slab, rendering it frequently necessary to collect 
 it together in the centre with a spatula, so as to keep it uniformly 
 under the action of the muller. The spatula may be of horn or 
 steel, but is better when of platinum. Fig. 67 exhibits a slab 
 and muller. When the substance under 
 operation is unalterable by water, it may ^ ig ' 67> 
 
 be moistened with that liquid, which, by C\ 
 
 converting it into a paste, facilitates its i_JI 
 
 reduction, and prevents any waste by the ^ " iii ' !!;; i 
 
 escape of dusty particles. The powdered 
 
 paste is easily dried by being dropped in dots upon a porcelain 
 plate and exposed to warmth. Those matters which are soluble 
 in or alterable by water, must be porphyrized in a dry state. 
 
 6th. Sifting. The impossibility of reducing the whole of a 
 substance at once to a uniform state of fineness by any of the 
 preceding processes, renders necessary an occasional separation, 
 
96 SIFTING. 
 
 during the progress of pulverization, of the more comminuted 
 portions from the grosser particles. This is effected by means 
 of a sieve, of which there should be several in the laboratory. A 
 wooden cylinder of about four inches depth, with an accompany- 
 ing ring of the same materials, constitutes the frame, over which 
 can be stretched a cloth of any required fineness. For coarser 
 articles, fine brass wire is the best material for the cloth, but 
 when the powder is to be impalpable, bolting cloth (raw silk), or 
 gauze is requisite. Sieves are also covered with hair-cloth, buck- 
 ram, book-muslin, and iron wire of different sized meshes, each 
 of which has its appropriate application. The metallic sieves 
 should have their cloths permanently fitted to them. For all the 
 rest, two frames, as above described, one of much larger dimen- 
 sions than the other, will serve ; as it is only necessary to remove 
 the ring when it is desired to substitute one kind of covering for 
 another. The sieves of cloth, of graduated fineness, can be kept 
 in some secure place, and withdrawn as wanted, and thus we 
 have the economical means of possessing a full suite of sieves 
 from the metallic wire, through all the grades of fineness up to 
 the closest wrought bolting-cloth. The form of a sieve is shown 
 at A, Fig. 68. After the separation of the finer portions by the 
 sieve, "the coarser particles are again sub- 
 Fig 68. jected to grinding and sieving as often as 
 is necessary to convert the whole into the 
 requisite state of uniform fineness. Horn- 
 scoops, or porcelain spoons, or ladles, are 
 the proper implements for transferring 
 the contents of the mortar to the sieve. 
 In some cases, a stiff pasteboard card, 
 being more pliable, is a convenient sub- 
 stitute. The use of the hand, for this 
 
 purpose, should always be avoided as a slovenly practice. A 
 platinum, horn or bone, or, less preferably, steel spatula may, be 
 used to detach the particles adherent to the sides of the mortar. 
 To prevent inconvenience or injury to the operator (who, both in 
 powdering and sieving, should always stand with his back to a 
 current of air), from particles of dust or acrid poisonous matter, 
 as well also to avoid waste, the sieve should be fitted with a top 
 and bottom covering, as shown at B and C, in Fig. 68, the upper 
 
SIEVES. 97 
 
 of which arrests the escape of the light dust into the air, and the 
 lower receives that portion which passes through the cloth. 
 These covers are headed with parchment or calf-skin, and the 
 three divisions, when joined together, form what is called a drum 
 or box-sieve. The powder is made to pass through the meshes 
 by gently agitating the sieve between the hands. A rough jar- 
 ring motion will force through some of the coarser particles, and 
 thus destroy the uniformity of the powder ; and hence the com- 
 mon practice of tapping it frequently against the side of the 
 mortar should be abandoned, unless the state of fineness is imma- 
 terial, as a regular and gentle horizontal motion is indispensable 
 to insure uniformity and impalpability. Some substances, how- 
 ever, as magnesia, &c., which obstruct the pores of the cloth, 
 must be forced through in this manner, and even, if necessary, 
 by a circular motion of the fingers over the interior surface of 
 the cloth. This manipulation frees the meshes of the cloth from 
 obstructions, but it must be carefully done, otherwise the safety 
 of the cloth will be endangered. A sieve is also useful for the 
 admixture of powders of uniform fineness. 
 
 The importance of restricting the sieve to a horizontal motion 
 induced Mr. Harris, of Philadelphia, to invent a special ar- 
 rangement (Fig. 69) for the purpose. The sieve is of the usual 
 form, but requires to be enclosed in a box. Motion is communi- 
 cated by means of a wheel, an axle, and a crank, with six eccentric 
 depressions and elevations 
 
 upon one of its sides. There Fi?. 69. 
 
 are two upright standards 
 fastened to the same foot- 
 board, one of which supports 
 the wheel and the other a 
 horizontal bar of iron pass- 
 ing through the side of the 
 box and attached by the 
 other end to the side of the 
 sieve, resting on horizontal 
 ledges in the interior of the 
 box. On turning the crank, 
 the horizontal bar will, in 
 
 its motion, necessarily follow the sinuosities of the wheel, and as 
 
 7 
 
98 LEVIGATION. 
 
 a consequence draw the sieve backwards and forwards. Very 
 fine powders are obtained by enclosing the powdered matters in 
 a bag of close texture and shaking it within a tin canister, which 
 catches and retains the dust as it passes through the meshes. 
 
 7th. Levigation Is that mode of mechanical reduction which 
 is practised by first rubbing the substance into a smooth paste, 
 and then separating the finer from the coarser portions by agita- 
 ting the triturated matters with water. After a sufficient repose, 
 the grosser and heavier portions subside, leaving the lighter par- 
 ticles still suspended in the water. This water, after decantation, 
 gives a second deposit of an increased state of fineness. The 
 third or fourth decantation yields the powder of impalpable fine- 
 ness. The time of repose between the decantations, unless great 
 impalpability is required, should be limited, and only long enough 
 to allow the deposition! of the heavier portions. The coarse pre- 
 cipitates are collected together, a second and as many more times 
 as necessary, rubbed up as before, and treated with water, until 
 all the lighter portions have been separated. This process ap- 
 plies only to substances unalterable by w r ater. When uniformity 
 of fineness is not all-important, one washing even suffices, and 
 can be accomplished in the mortar without the use of glasses. 
 Alternate poundings and washings will eventually reduce and 
 remove the whole contents of the mortar. In washing over gold 
 and other metallic ores, where only the heavier portions are to 
 be reserved, the water may be allowed to flow directly into the 
 mortar, which being held in an inclined position, permits its exit, 
 together with the fine dusty portions which are kept in suspension 
 by trituration with the pestle. 
 
 This process of levigation is founded upon the different specific 
 gravities of the coarse and fine bruised matters, and is, therefore, 
 not only applicable for the separation of the particles of homo- 
 geneous matters, but also of equally fine matters of unequal den- 
 sities. In the latter case it takes the name of elutriation. 
 
 All minerals for analysis, which have to undergo ignition with 
 alkalies, should be previously levigated, in order that decompo- 
 sition may be complete ; for if the powder is not uniform the 
 larger particles will escape decomposition. 
 
 Pulverization in this manner, by uniformly comminuting the 
 particles, promotes their equal expansion and the escape of con- 
 
GRANULATION. 99 
 
 tained moisture, and thus prevents the decrepitation of substances 
 when heated. 
 
 The deposited powder must always be dried, by exposure, pre- 
 vious to subjecting it to any other process. 
 
 8th. Reduction by Granulation. The reduction of metals to 
 granules is effected by fusing them in a crucible, and pouring the 
 melted matter, from an elevation, in a thin stream, very gradu- 
 ally, into a large bulk of cold water which must be kept, during 
 the process, in constant agitation with a stirrer. The fineness of 
 the resultant granules is proportional to the slowness with which 
 the fused metal was poured into the water. It is more convenient 
 to transfer the metal from the crucible into a ladle, and project 
 it into the water from that more handy vessel, which enables a 
 frequent change of the position of the descending stream, and 
 thus prevents the formation of clots instead of smaller and more 
 solid granules. The fusion of zinc for granulation must be in a 
 covered crucible, otherwise it becomes oxidized whilst hot, and 
 partially sublimes by exposure in an open vessel. Zinc and tin 
 may also be finely divided by heating them a little above their 
 melting-points and rubbing them in a previously heated iron 
 mortar, until the mass congeals into powder. Iron is brought to 
 powder mechanically by the file, and chemically by reduction in 
 an atmosphere of hydrogen gas. 
 
 The process of fusing metals and then agitating the melted 
 matter in a wooden box until cool, reduces them to a state of 
 minute division, but at the same time promotes their oxidation. 
 For general purposes, however, it is not objectionable, and the 
 particles of charred wood with which it becomes mixed can be 
 separated by elutriation. The sides of the box are generally 
 well chalked, to prevent any adherence of the metal; and this 
 also is separable by elutriation. 
 
 REDUCTION BY CHEMICAL MEANS. 
 
 9th. Division by Intermedia. This mode is both mechanical 
 and chemical, and applies particularly to the noble metals, in 
 foil, which are difficult of pulverization. Honey, sugar, salts, 
 &c., are the most usual media. By binding the particles together, 
 it assists their minute division, and prevents their escape from 
 
100 THE BALANCE. 
 
 the mortar. The addition of boiling water solves out the medium, 
 without action upon the metallic powder, which then only requires 
 to be thrown upon a filter and dried. 
 
 Phosphorus may be finely divided by fusing it, with alcohol, 
 over a water-bath, and shaking the contents of the flask until 
 thoroughly cooled. The phosphorus subsides at the bottom in 
 pulverulent form. Camphor, which is obstinate under the pestle, 
 readily yields to its power when mixed with a few drops of alco- 
 hol or ether, to destroy its elasticity. 
 
 Silica may be precipitated from lime-glass in a pulverulent 
 form, by the digestion of that compound with hydrochloric acid. 
 Silver is obtained in a powder by the decomposition of its nitric 
 solution with a metallic copper rod ; or of its chloride by metallic 
 zinc. Proto-sulphate of iron throws down gold, in a finely-divided 
 state, from the solution of its chloride; and spongy platinum is 
 formed by the dull ignition of the ammonia-chloride of that metal. 
 These are instances of chemical division by purely chemical 
 means. The extreme state of division thus obtained by the 
 solution and precipitation of a solid body, (a chemico-mechanical 
 process) cannot be effected by any purely mechanical power. 
 
 The sublimation of sulphur into flowers, as also of calomel into 
 fine powder by means of large airy chambers, are instances of 
 comminution by chemico-mechanical means ; the vaporized par- 
 ticles being prevented from reunion, at the moment of solidifica- 
 tion, by the intervention of the cold air. So, likewise, in cases 
 of division by hydro-sublimation, the intervention of aqueous 
 vapor prevents the conjunction of the vaporized molecules. Dr. 
 Joslin (Sillimaris Journal, p. 48, vol. v) treats of this subject in 
 extenso. 
 
 CHAPTER V. 
 
 THE BALANCE. 
 
 A BALANCE may be considered the most indispensable imple- 
 ment of the laboratory, as affording the only means by which the 
 chemist can accurately estimate the quantitative results of his in- 
 
THE BALANCE ITS REQUISITE CONDITIONS. 101 
 
 vestigations. The construction of this instrument for determining 
 the relative weight (the measure of the force by which any body, 
 or a given portion of it, gravitates towards the earth) of sub- 
 stances, is based upon certain mechanical principles, of which we 
 proceed to give a brief explanation. 
 
 A balance consists of an upright shaft, supporting, by its 
 immediate centre, an inflexible lever or beam, with arms of equal 
 length and symmetry, to each of which is suspended a dish for 
 the reception of the weights (the power), and the body to be 
 weighed (the resistance). Of the three axes of the beam, that in 
 the middle is the fulcrum or centre of motion, upon which it 
 turns in a vertical plane. The other two axes are at the extre- 
 mities of the arms. All three axes should be at right angles to 
 the plane of motion, and parallel to each other. 
 
 The requisite conditions of a good balance. One of the chief 
 conditions of an accurate balance is a free suspension of the 
 beam, in order that it may vibrate with the least possible friction. 
 The two arms must also be precisely equal, so that when empty, 
 or the weight in each dish is uniform, there will be a perfect 
 equilibrium. The sensibility of a balance is proportional to the 
 angle formed by the beam with the horizon, when a slightly 
 greater weight is placed in one dish than in the other. This 
 sensibility depends on the position of the centre of gravity of the 
 beam with reference to the line of suspension ; this centre must 
 be below that line, but as near as possible to it, so that the 
 slightest weight will cause the beam to oscillate freely. 
 
 As the inertia and friction are proportional to the weight of 
 the beam, it must be made of material entirely free from imper- 
 fections, and so as to combine strength and inflexibility with 
 lightness. It may be of solid steel, rolled brass, German silver, 
 or of a malleable alloy of copper and tin, but not of cast metal 
 of any kind. The upright support can be of brass, and the 
 dishes and suspension frames of platinum. 
 
 The sensibility of the balance increases with the length of the 
 arms, which should, however, have a certain limit, and be as 
 nearly uniform as possible in every respect. When, through 
 unskilful construction, the length of one arm is slightly greater 
 than that of the other, in order to avoid the error in weighing 
 which this defect would occasion, the body to be weighed is 
 
102 THE MINT BALANCE. 
 
 placed in one pan, and counterbalanced by weights in the other. 
 The amount of weight required to restore the equilibrium, after 
 the withdrawal of the substance, is its correct weight. 
 
 In order to avoid friction, the parts of contact should be as 
 few as possible, and the knife edges must be made of highly 
 polished, hardened steel, and the beds or planes upon which they 
 rest, of agate or flint. The accuracy of the balance will depend 
 greatly upon the skill and precision with which these portions 
 and the beam are elaborated. 
 
 A good balance, with 1 to 2000 grains on each dish, should be 
 sensitive to the one or two thousandth of a grain. 
 
 The Mint Balance. " To obtain the greatest degree of uni- 
 form precision, it is requisite that the beam should be lifted from 
 a state of rest, in a perfectly level position, and that the stirrups 
 should be lifted simultaneously with their loads from their rests 
 or supports; also that the oscillations of the stirrups should 
 be prevented or checked at the earliest moment; and, finally, 
 that the whole system should be left at liberty with delicacy and 
 exactitude, so as to remain in equilibrium, or vibrate as the case 
 may be." 
 
 " To command the above conditions, the beam should be sup- 
 ported upon cones at each extremity, adjusted level with each 
 other, from which it is lifted, by a plane (and not a portion of a 
 hollow cylinder, as is usual), which rises under its centre knife- 
 edge, and to which it is returned by its depression, the cones 
 guiding the beam to the same position exactly from which it was 
 elevated. 
 
 " The stirrups, in like manner, should hang upon hollow cones 
 or V's, so as to be taken up from, and returned invariably to the 
 same position. 
 
 " The beam should rest upon its cones, and the stirrups should 
 be supported by their V's at such heights as to relieve entirely 
 the knife-edges, with a sufficient space between them and their 
 respective planes to permit inspection and wiping, when it may 
 be needed. This construction admits of the placing of the 
 weights, &c., and guards the knife-edges from the consequences 
 of displacement during use.. 
 
 " The beam should be raised by the elevation of the centre 
 plane, subsequently lifting with it the stirrups with their weights 
 and load, and all oscillation checked by platforms placed in the 
 
THE MINT BALANCE. 
 
 103 
 
 table under the centre of the stirrups, which should be made to 
 rise simultaneously, and should be counter-weighed to the requi- 
 site delicacy. 
 
 " The descent of these platforms, effected by the pressure of 
 a finger on a lever conveniently placed, will leave the stirrups, 
 &c., at liberty to vibrate, or bring the beam to a horizontal position, 
 at the will of the operator, being a convenient, certain, and rapid 
 method of manipulating, not equalled by any other arrangement, 
 and, in fact, essential to a well-constructed balance." 
 
 These essential qualities of an accurate balance for the more 
 delicate operations of the ' laboratory are comprised in that form 
 of balance used in the United States Mint, and which " combines 
 all the important advantages heretofore known with such im- 
 provements as have been the growth of their own experience." 
 
 This form of balance is best adapted for exact weighings of 
 large quantities of matter ; and therefore should constitute the 
 larger weighing apparatus of the laboratory. 
 
 Fig. TO gives a front view of it. We take our description from 
 the Journal of the Franklin Institute, vol. xiv. 
 
 Fig. 70. 
 
 A table, marked A, is furnished with levelling screws upon the 
 front and back edge, and at each end, marked b. In Fig. 72, 
 which exhibits different views of all the parts, the levelling screws 
 are marked 5, and their positions in the table (the view of the 
 under side of which is given) are marked c. 
 
 The balance is intended to be placed upon a counter, or any 
 
104 
 
 THE MINT BALANCE. 
 
 other firm support, and the table levelled by means of the screws 
 last described, its true position being indicated by a plumb-line 
 and weight occupying the rear opening in the column (Fig. 72, 
 C) ; the plumb-line and weight being marked d. 
 
 The column, marked C, Figs. 70, 72, contains the lifting ap- 
 paratus, and supports the cap-plate, marked D. The cap-plate 
 guides the lifting apparatus, and supports the V's, or hollow 
 cones, for the stirrups, and is strengthened and stayed by braces, 
 marked E ; the section of which braces is cruciform, with circular 
 ends, for firm bearing upon the plate and base of the column, to 
 which they are secured by screws. 
 
 Figs. 71, 72, exhibit upper and under views of the table, co- 
 lumn, plate, &c., also upper and lower end views of the column, 
 showing the means of its attachment to the table and cap-plate. 
 
 Fig. 71. 
 
 The lifting apparatus consists of a winch-handle, marked /, 
 Fig. 72, fitting upon a round shaft #, with a feather, so as to 
 admit of its convenient removal; upon this shaft is fitted a cam 
 A, also secured by a feather ; the cam is carefully constructed, 
 so as to give equal elevation to equal parts of its revolution ; and 
 upon the cam rests a roller i, which turns upon a pin in the 
 frame /, intended to reduce friction, and give facility in raising 
 the beam with its load. 
 
 The lifting frame /, is forked cross-wise, so as to straddle the 
 shaft and accommodate the cam and roller, at the same time that 
 it allows the necessary vertical motion, without the possibility of 
 being displaced ; all of which is exhibited in the two views of the 
 
THE MINT BALANCE. 105 
 
 lifting frame marked j, which is also accompanied by sections in 
 proximity to the parts which they are intended to explain. 
 
 The handle is so placed as to be on the left when the beam is 
 down and at rest, and to the right when the beam is raised, in the 
 act of weighing, and makes, together with the cam, more than 
 three-fourths of a revolution, the cam having a very slight de- 
 pression upon its upper, or highest point, into which the roller 
 falls, maintaining it in its position when the beam is raised. It 
 is then extended beyond the centre of the roller, so as to be 
 stopped at the limit of motion, as exhibited A, Fig. 72. 
 
 Fig. 72. 
 
 s "^ >i* H 13 
 
 The lifting-frame is forked at the top for the accommodation 
 of the beam. Upon it rests the plane, the top and side view of 
 which are marked k, for the support of the centre knife-edge, 
 secured to the frame by screws. In balances of ordinary t con- 
 struction, this plane may be made of hardened cast-steel ; in finer 
 instruments, of bronze, or brass, with an inserted block of polished 
 agate, secured by fusible metal or cement. 
 
 The position of the handle, lifting-frame, &c., are exhibited 
 with sufficient clearness in the front view, Fig. 70. 
 
 The cap-plate, views of the upper and under sides of which are 
 given at D, Fig. 71, is constructed with horizontal spaces at the 
 centre and each end. In the middle it is secured to the column 
 by four screws, and to the braces B in the same manner, the 
 holes for which are marked in all the views. 
 
 The square opening in the middle serves as a guide and sup- 
 port to the lifting-frame, which must be accurately fitted, so as 
 to prevent any lateral play. 
 
106 THE MINT BALANCE. 
 
 The horizontal spaces at the extremity of the cap-plate support 
 short pillars terminated by cones, upon which the beam rests ; 
 these pillars are secured to the cap-plate by screws passing 
 through it from the under side, the holes through which they 
 pass being large enough to admit of the adjustment of the beam 
 to its proper place, previous to their being permanently fastened 
 down. 
 
 The details of these pillars are given at ?, Fig. 72, the cones 
 being constructed of cast steel, hardened and polished. 
 
 The same space also supports the V's, or guide supports of the 
 hangers, different explanatory views of which are given in Fig. 
 72, the V's being marked m 9 and the hangers n. All these 
 parts have been devised with reference to the simplest and most 
 economical construction consistent with the requisite accuracy, 
 and for affording the greatest facility in the final adjustment of 
 the balance. 
 
 The most important part of the balance is the beam o ; and Fig. 
 72 exhibits side and top views. The projections marked <?, are 
 the supports of the beam when at rest ; the conical cavities, indi- 
 cated by dotted lines, being made to fit the cones marked I. 
 
 This form of beam affords facility in construction, being com- 
 posed of straight surfaces, without ribs or curves ; is well adapted 
 to maintain its form when loaded : affords the least surface for 
 accumulation of dust, and is readily wiped when it may be 
 necessary. The means of adjustment for the length of arm is 
 exhibited at r, Fig. 72. 
 
 It will be seen, that the needle of the balance which is the 
 subject of description, is pointed downwards ; and there are good 
 reasons for this disposition, In the first place it is directly 
 before the eye of the operator, and, therefore, more convenient 
 in use, than it is when elevated above ; again, it may be made 
 longer than the arms of the beam, and will, consequently, de- 
 scribe a larger arc, and thus give more distinct indications, 
 whilst the whole arrangement need occupy no more space than is 
 requisite for the other parts ; and, finally, the needle is protected 
 from external injury by the lifting-frame and column, in the 
 centre of which it is placed* 
 
 The parts which remain to be described have been usually 
 considered of minor importance, but experience has shown that 
 
THE MINT BALANCE. 107 
 
 this estimate is scarcely a just one, inasmuch as they afford faci- 
 lities for accuracy and rapidity, that leave no doubt of their value, 
 and place them in a most important position in practice. The 
 parts now alluded to, constitute the system by which the opera- 
 tor is enabled to find the equilibrium of which he is in search. It 
 consists of the pedestals, as they have been termed, marked s, 
 Figs. 70 and 71, and the parts connected with them, marked t, 
 u, v, and w, in Fig. 71 ; a light shaft, made of tubular iron, , 
 supported by pivots w, which pivots are screwed through a piece 
 cast on the under side of the table, marked V ; upon the ends of 
 this shaft there are levers W, upon the ends of which levers, when 
 in place, the pedestals rest. 
 
 The remaining part of this system is a double armed lever, 
 placed in the middle of the shaft t (represented in the engraving 
 detached), and marked x ; it is connected by a pin, with the 
 trigger, z, represented in its place in Fig. 71, with the same 
 letter. Upon the other end of the lever x, there is a weight #, 
 capable of adjustment by a screw upon which it traverses, so that 
 it may be made to approach, or recede from the shaft t. 
 
 The action of this system is easily understood; its whole ob- 
 ject is to depress the platforms by sufficient force, applied by the 
 finger, to the trigger, the counter-weight returning them to their 
 original position, after its removal. 
 
 It will be seen, by reference to Fig. 70, that the under sides 
 of the stirrups have a space, represented by dotted lines, in which 
 the platforms are placed, which allows the stirrups to oscillate 
 within its limits, but beyond which they cannot move. This con- 
 struction is intended to guard the hangers from displacement, 
 and to prevent injury by too much movement of the stirrups, an 
 accident very likely to occur, when the pans or weights are 
 hastily removed, especially in the use of heavy weights or large 
 masses. 
 
 The cavity, whose object was described in the last paragraph, 
 forming the under side of the base of the stirrups, is turned as 
 truly as possible in the form of a portion of a sphere, whose 
 radius is its distance from the bearing of the knife-edge. The 
 platforms are adjusted by means of the counter-weight, so as to 
 press lightly up against the stirrups, and to follow them when 
 raised. 
 
108 EATER'S BALANCE, 
 
 It is found convenient in practice to turn the handle of the 
 balance but a small portion of its movement, if the weights are 
 not equal on opposite sides, a circumstance to be expected \vhen 
 searching for a weight. The heavy side will remain down, and 
 the needle will indicate whether addition of weight or its removal 
 is requisite. These trials are continued until the platforms fol- 
 low up the whole lift, the needle remaining opposite the middle 
 line of its scale, until the handle is stopped by its limit of motion, 
 where it remains. The finger, then, by pushing down the trig- 
 ger, will depress the platforms, when smaller weights are em- 
 ployed, until the needle indicates equilibrium. 
 
 In this balance there is little or no embarrassment from oscil- 
 lation, because the stirrups immediately accommodate themselves 
 to the position of the weights, the light pressure permitting them 
 to take any position required by the load ; nevertheless, having 
 sufficient power, from their pressure, to prevent any swinging. 
 If from any cause the stirrups should be in motion, three conse- 
 cutive depressions of the platforms will bring them to a state of 
 rest with absolute certainty, and with a loss of time so short as 
 to be entirely immaterial. 
 
 The stirrups are connected with the hangers, by a rod, which 
 is double-jointed, as near to the hangers as possible, so as to 
 allow perfect freedom of motion ; at the same time, so well fitted 
 as to allow no change of position in the parts. On the lower 
 ends of these rods there are screws and nuts, to regulate the 
 height of the stirrups, together with a jam-nut, to prevent any 
 change after the adjustment has been satisfactorily made. 
 
 The bases of the stirrups are designedly made small, requiring 
 the use of a dish on the one side, and a platform for weights on 
 the other. This dish and platform being made of equal weight, 
 renders the use of a counter-weight unnecessary ; and as the 
 balance cannot be used without both, the liability to mistakes 
 from this cause is entirely avoided. 
 
 The principle of the Mint balance has been adopted in the 
 construction of one of our finest analytical balances, which was 
 made for us by John Jones, Baltimore. 
 
 Hater's and Robinson's .balance. This, Fig. 73, though more 
 complicated than the preceding, is an excellent balance for estima- 
 ting minute quantities with precision ; and, indeed, for all the 
 
ROBINSON'S BALANCE. 
 
 109 
 
 weighing operations of delicate research. When carefully pre- 
 served, it retains its sensibility for many years. 
 
 Fig. 73. 
 
 We are indebted for our description to Lardners Elements of 
 Mechanics. 
 
 " The beam of this balance is only ten inches long. It is a 
 frame of bell-metal in the form of a rhombus. The fulcrum is 
 an equilateral triangular prism of steel, one inch in length ; but 
 the edge on which the beam vibrates is formed to an angle of 
 120, in order to prevent any injury from the weight with which 
 it may be loaded. The chief peculiarity in this balance consists 
 in the knife-edge, which forms the fulcrum, bearing upon an 
 agate plane throughout its whole length ; whereas in the other 
 balances the whole weight is supported by portions only of the 
 knife-edge, amounting together to one-tenth of an inch. The 
 supports for the scales are knife-edges, each six-tenths of an inch 
 long. These are each furnished with two pressing-screws, by 
 means of which they may be made parallel to the central knife- 
 edge. , 
 
 "Each end of the beam is sprung obliquely upwards and 
 towards the middle, so as to form a spring through which a 
 
110 ROBINSON'S BALANCE. 
 
 pushing-screw passes, which serves to vary the distance of the 
 point of suspension from the fulcrum, and, at the same time, by 
 its oblique action, to raise or depress it, so as to furnish a means 
 of bringing the points of suspension and the fulcrum into a right 
 line. 
 
 " A piece of wire, four inches long, on which a screw is cut, 
 proceeds from the middle of the beam downwards. This is 
 pointed to serve as an index, and a small brass ball moves on the 
 screw, by changing the situation of which the place of the centre 
 of gravity may be varied at pleasure. 
 
 " The fulcrum, as before remarked, rests upon an agate plane 
 throughout its whole length, and the scale-pans are attached to 
 planes of agate, which rest upon the knife-edges, forming the 
 points of support. This method of supporting the scale-pans, 
 we have reason to believe, is due to Mr. Cavendish. Upon the 
 lower half of the pillar, to which the agate plane is fixed, a tube 
 slides up and down by means of a lever which passes to the out- 
 side of the case. From the top of this tube, arms proceed 
 obliquely towards the ends of the balance, serving to support a 
 horizontal piece, carrying at each extremity two sets of Y's, one 
 a little above the other. The upper Y's are destined to receive 
 the agate planes to which the scale-pans are attached, and thus 
 to relieve the knife-edges from their pressure ; the lower to 
 receive the knife-edges themselves, which form the points of 
 suspension of the pans, consequently these latter Y's, when in 
 action, sustain the whole beam. 
 
 " When the lever is freed from a notch in which it is lodged, 
 a spring is allowed to act upon the tube we have mentioned, and 
 to elevate it. The upper Y's first meet the agate planes carry- 
 ing the scale-pans, and free them from the knife-edges. The 
 lower Y's then come into action, and raise the whole beam, ele- 
 vating the central knife-edge above the agate plane. This is the 
 usual state of the balance when not in use: when it is to be 
 brought into action, the reverse of what we have described takes 
 place. On pressing down the lever, the central knife-edge first 
 meets the agate plane, and afterwards the two agate planes, 
 carrying the scale-pans, are deposited upon their supporting 
 knife-edges. 
 
 "A balance of this construction was employed by Captain 
 
BERLIN BALANCE. 
 
 Ill 
 
 Kater in adjusting the national standard pound. With a pound 
 troy in each scale, the addition of one-hundredth of a grain 
 caused the index to vary one division, equal to one-tenth of an 
 inch ; and Mr. Robinson adjusts these balances so that with one 
 thousand grains in each scale, the index varies perceptibly on the 
 addition of one-thousandth of a grain, or of one-millionth part of 
 the weight to be determined." 
 
 Duffy has added a very simple but useful improvement. It 
 consists of an elastic spring, 
 A A, Fig. 74, serving as a sup- 
 port for the dishes when the ba- 
 lance is at rest; and at the 
 same time so arranged, that by 
 the depression of the thumb- 
 lever suitably attached, the dishes are thrown off their supports, 
 and the beam put into action simultaneously. 
 
 Fig. 75. 
 
 Fig. 74. 
 
 Berlin Balance. This pattern of balance combines, in an 
 eminent degree, all the requirements of a convenient and exact 
 weighing apparatus at a moderate cost. It is, therefore, deserv- 
 
112 BERLIN BALANCE. 
 
 edly popular with chemists for the analytical and delicate weigh- 
 ings of the laboratory. Fig. 75 presents the instrument in its 
 most improved form. 
 
 The support and beam are, as usual, of brass; the pans of 
 platinized copper, and the suspension wires of the same material, 
 or pure platinum. The beam is constructed with knife-edges at 
 the ends, and upon which the pans are suspended by agate planes. 
 The centre knife-edge also moves upon an agate plane ; and to 
 bring all the knife-edges into the same straight line as well as to 
 equalize the lengths of the arms of the beam, the latter is fitted 
 with a suitable means of adjustment. A screw-knob above the 
 centre of the beam serves to adjust the centre of gravity. 
 
 The balances are made either with or without supports to the 
 pans, as may be preferred by the operator ; but, in either case, 
 there is a mechanical system for steadying them. It connects 
 with the same axis which moves the beam, so that one movement 
 of the handles first releases the pans and then the beam. When 
 supports are used, they must be faced with ivory to prevent the 
 pans losing any weight by abrasion of their under surfaces. 
 
 The beam is graduated on each arm into ten divisions, for the 
 use of a sliding-weight or "rider;" and an apparatus above the 
 beam, at the right side, serves, by means of an external handle 
 or knob, for moving the rider from division to division, as may be 
 necessary, without opening the case. The use of the rider, as 
 will be learned in the chapter on WEIGHING, does away with the 
 necessity of having weights lower than the hundredth of a grain 
 or a centigramme. 
 
 These balances are generally provided with the supplementary 
 apparatus for taking specific gravities and for 
 weighing tubes, bulbs, &c. (Fig. 76). The 
 lantern, or glass case, is constructed with ad- 
 justing screws to maintain a perfect level ; 
 and the drawers at the bottom being fitted 
 with plush-covered receptacles for the several 
 parts of the apparatus, it becomes a safe 
 means of transporting the instrument without 
 the trouble of special packing. The sliding 
 part and back, and the hinged doors at the 
 end, afford every facility for weighing long 
 
TRALLE'S BALANCE. 113 
 
 tubes and similar apparatus; and in the finer balances, the bot- 
 tom is of glass-plate, which contributes materially to the good 
 order of the balance, as it may be readily kept clean. These ba- 
 lances cost $30, $60, $90, and $125, according to finish, and 
 inclusive of weights. Those at the lowest prices will carry four 
 hundred grains, and turn with one-fiftieth of a grain. Those of 
 greatest delicacy will turn with one-thousandth of a grain when 
 loaded with fifteen hundred grains. 
 
 Assay Balance. This instrument should be constructed with 
 great skill and accuracy ; for it is used only for the very precise 
 weighing of minute quantities. When the luxury can be afforded, 
 the laboratory should be provided with one ; but otherwise the 
 analytical balance may be made to serve its purposes. To this 
 end, it must always be kept in perfect adjustment. For blow- 
 pipe operations, Plattner's Assay Balance will be found very satis- 
 factory. If skilfully made, it will turn with one-fifth of a milli- , 
 gramme ; but the pans should be suspended by platinum wire 
 instead of a silken cord as at present. The top of the box 
 forms the base for the pans, which are raised by a lever. These 
 balances, compactly arranged in portable boxes, cost, with weights, 
 from $26 to $32. 
 
 Tralles Balance. This is an appropriate apparatus for weigh- 
 ing heavy or bulky articles, of which the required quantities are 
 large, for example, gold ores, vegetable matters, &c., intended 
 for analysis and investigation ; as in such instances, the dusty 
 emanations would render the use of the finer mint balance inju- 
 dicious. They are made of sufficient delicacy to turn with one or 
 two grains when loaded with five pounds, and at a cost of only 
 $20 to $25. 
 
 The annexed drawing represents the instrument, which consists 
 of two brass dishes A A, suspended by loops D D, resting upon 
 the steel knife-edges at the extremities of -the beam C. The 
 beam is supported by the knife-edge in its centre as at E, and 
 the whole balance is suspended to an upright, crooked at its top, 
 by the hanger B. Annexed to the eentre of the beam is a long 
 vertical needle, which, following the vibrations of the beam, 
 serves to indicate the least oscillation, which is rendered more 
 perceptible by an ivory segment situated behind its point, and 
 divided into degrees. This balance is placed in the room D, PL 
 
 8 
 
114 
 
 PLATFOKM BALANCE. 
 
 2, upon the table adjoining that upon which is the finer balance. 
 The support to which it is suspended may be either of wood or 
 metal. To prevent damage to the knife-edges, the dishes, when 
 
 Fig. 76 a. 
 
 -A. 
 
 the scales are not in use, should be unhung, and the whole ba- 
 lance kept covered with a linen cover, distended over a wire 
 framework, which may be suspended by a cord upon a pulley, 
 and counterpoised so as to admit of being readily raised or 
 lowered. It would add to the durability of the balance to gild 
 the knife-edges. 
 
 Platform Balance. This is for the general purposes of the 
 store-room. The best form is that known as "Beranger's Pen- 
 Fig. 77. 
 
 dulum Scale," Fig. 77, as it combines the advantages of precision, 
 strength, and durability. 
 
PRESERVATION OF THE BALANCES. 115 
 
 Preservation of the Balances. Each of the finer balances 
 should have a separate table, and these tables a permanent posi- 
 tion in a close, well-lighted room, expressly appropriated for the 
 purpose. The top of the table must be of hard wood and per- 
 fectly horizontal; and to secure the table itself against the 
 slightest jarring motion, it may be tightly fastened to the floor 
 by iron clamps and screws fitted to its legs. Great care is requi- 
 site to have it plumb. Of the two drawers which it should con- 
 tain, one is for the spatulas, spoons, crucible tongs, papers, watch- 
 glasses, and other implements used in weighing; the other may 
 be fitted deskwise, and furnished with slips of paper, or a porce- 
 lain slate and pencil, to afford convenience in recording the 
 weights. A polished cast iron slab, about six inches square, upon 
 which to set the heated crucibles and promote their cooling by 
 conducting off the excess of heat previous to weighing, may be 
 considered a necessary accompaniment x)f the table. In order to 
 preserve its brightness, it should be encased in a woollen bag and 
 kept within the drawer when not in use ; or it may be enclosed in 
 a frame with a sliding cover, and fastened to the top of the table 
 near to one of its corners. The cover which protects its surface 
 from oxidation can readily be drawn out whenever it is required 
 to use the slab. 
 
 It is not sufficient for the preservation of the delicacy of the 
 balances, that the room in which they are kept should be dry and 
 tight. Vapors, aqueous and corrosive, will in divers ways find 
 entrance into the apartment, and so, therefore, besides the pre- 
 caution of lacquering the brass and gilding the steel parts of the 
 balance, the instrument should be enclosed in a sufficiently capa- 
 cious mahogany or walnut case, with sash-doors in the front and 
 back, and sash-windows at either side. The doors should be 
 always kept closed and fastened by their buttons when the ba- 
 lance is not in use, else the entrance of dust and moisture will 
 impair its accuracy. An additional and very effectual precaution 
 against oxidation by moisture, is to keep constantly within the 
 case a glass containing some absorbent matter, as fused chloride 
 of calcium or carbonate of potassa. By an occasional renewal of 
 the absorbent matter, the atmosphere within the case can be 
 kept very dry. The multiplication of doorways is to afford faci- 
 lity for the passage and weighing of long tubes, which have to 
 
116 THE BALANCE THE WEIGHTS. 
 
 be placed across the' pan. The divisions in the drawer at the 
 bottom of the ease must be lined with velvet, and so arranged as 
 to receive the different parts of the balance, and allow its trans- 
 portation without the least risk of damage. 
 
 In order to preserve the edges of the knives, the beam should 
 always be thrown out of action when the balance is not in use, 
 otherwise their constant contact with the planes, and the pressure 
 of the balances, as well as the sudden addition of a heavy weight, 
 will injure their delicacy. 
 
 The three or four feet upon which the case rests have screws 
 passing through them. These serve to give the balance a per- 
 fectly horizontal position, even upon an uneven surface the 
 level being obtained by raising or depressing either of the screws, 
 as the case requires, and as will be indicated by the two spirit- 
 levels, which should be fitted to the pedestal of each balance. 
 
 The. position of the balance should be with due regard to light, 
 but while placed near the window, to afford facility in perceiving 
 the slightest oscillations of the needle, it should be free from 
 draughts of air, and also from the action of the solar rays, which, 
 by producing unequal expansion of the different parts, would occa- 
 sion inexact results in weighing. 
 
 The balances should be cleansed and adjusted whenever they 
 have become inaccurate, for it is almost impossible for even the 
 best balance to retain its sensitiveness indefinitely. This work 
 should rather be confided to a manufacturer of balances, as it 
 requires both skill and experience. Slight discrepancies in the 
 weight of the two dishes can be temporarily compensated for by 
 adding to that dish which is deficient, sufficient weight to restore 
 its equilibrium. 
 
 CHAPTER VI. 
 
 THE WEIGHTS. 
 
 THERE are three sets of weights requisite, of which one for 
 the platform balance of the store-room should be avoirdupois, 
 and range from eight or more pounds downward to a quarter of 
 an ounce. These weights are for the rougher operations of 
 
THE WEIGHTS. 117 
 
 weighing, and may be of brass or of cast iron coated with black 
 japan to protect them against oxidation. 
 
 For the larger balances, a finer and exact set is necessary. 
 They should be made of brass, in the form of short cylinders, /, 
 Fig. 80, with knobs at the top, and range from 25,000 to 0-1 
 grains, decreasing by fives in the series to 500, as follows: 
 25,000, 20,000, 15,000, 10,000, 5,000,1,000, 500; and from 
 that point as follows: 400, 300, 200, 100, 50, 30, 20, 10, 5, 4, 
 3, 2, 1, 0-1. 
 
 The weights for the analytical or assay balances must be of the 
 finest and most precise workmanship. 
 
 If they are grain weights, the series should range from 5,000 
 grains to Tu y o th of a grain, as follows: 5,000,. 3,000, 2,000, 
 1,000, 500, 300, 200, 100, 50, 30, 20, 10, 5, 3, 2, 1, -1, -2, -3, 
 5, -05, -03, -02, -01, -005, -003, -002. The gramme weights 
 range from one centigramme to one milligramme. The divisions 
 of the gramme (the standard unit of the French weights) are the 
 decigramme = y^th gramme; the centigramme = jjo^h gramme; 
 the milligramme = yiraoth gramme. Its multiples are the 
 decagramme = 10 ; the hectogramme = 100 ; the kilogramme = 
 1000; and the myriagramme = 10,000 grammes. The table 
 below shows the relative value and proportions of the French 
 decimal and troy and avoirdupois weights : 
 
 Metrical or Decimal Weights. 
 Name, Equiv. in grammes. ^ Equiv.^.avoirdupois 
 
 Ibs. oz. grs. 
 
 Milligramme, -001 '0154 
 
 Centigramme, -01 -1543 
 
 Decigramme, ! 1-5434 
 
 Gramme, ! 15-434 
 
 Decagramme, 10- 154-3402 OJ 45- 
 
 Hectogramme, 100- 1543-4023 3 12-152 
 
 Kilogramme, or Kilo, 1000- 15434-0234 2 3 12-173 
 
 Myriagramme, 10000- 154340-2344 22 Of 12- 
 
 All of the weights for the fine balance must be adjusted with 
 the nicest accuracy, and before being used should be compared 
 with others of attested correctness. Of the French weights those 
 from the milligramme to the gramme should be of platinum ; and 
 so, also, of the grain weights, those from the ten-grain weight 
 downwards should be of the same metal. Palladium being of 
 
118 THE WEIGHTS. 
 
 but half the specific gravity of platinum, and similar to it in 
 other respects, is sometimes used for the fractional grain weights, 
 because of the greater relative surface which it presents. They 
 are frequently made of silver, and gilded. Aluminium being 
 very light might also be used for the purpose. The remaining 
 larger weights, to save expense, may be of brass, and, to pre- 
 serve them from Oxidation, should either be covered with a thin 
 coat of lacquer, or, better, galvanized with gold or platinum. 
 
 Each set should contain duplicates of the 10, 2, and 1 grain 
 weights; triplicates of the '2, -1, '02, -01, and quadruplicates of 
 the *001 grain weights; for in many instances, especially in taking 
 specific gravities, these additional weights are indispensable. 
 Berlin balances are provided with "riders" which do away with 
 the necessity of having weights less than a centigramme, or hun- 
 dredth of a grain. 
 
 In order to preserve the weights free from dust and oxidation, 
 they must be encased in a close box with hinged cover and fas- 
 tenings. The interior of the box should be divided into com- 
 partments, lined with velvet, to prevent abrasion of the surfaces 
 of the weights, each of which must have a separate division. 
 The edges of every compartment should be marked in ink with 
 the value of the weight it contains ; and the weights themselves 
 must have their denominations stamped upon them. The series 
 must be so accurately adjusted, that the difference between any 
 one of the large weights and the combined number of smaller 
 ones, equal to it, shall not be perceptible in a balance turning 
 with one-tenth of a milligramme. 
 
 To test their accuracy, take any two of them of the same 
 denomination, convey them, with the fork or forceps, to the 
 balance, and place one in each dish. If the beam upon being 
 put in action is in perfect equilibrium, the weights are uniform, 
 and can serve as standards. Then, for further verification, place 
 both together in one dish, and in the opposite pan add enough of 
 smaller weights to equal that of the two combined. If the 
 beam still retains its equilibrium, when put in action, the weights 
 may be considered correct. 
 
 As frequent handling of- the weights with the fingers would 
 tarnish them, and otherwise injure their value, a small fork and a 
 pair of forceps are necessary accompaniments to each set of 
 
THE WEIGHTS. 119 
 
 weights. The fork, represented by Fig. 78, made of either 
 ivory, horn, or wood, and being intended for 
 raising the brass weights, has its notches at 
 either end of different size, so as equally to 
 accommodate the knobs of both the larger 
 and smaller weights. A small pair of elastic 
 forceps, Fig. 79, of brass or plated, or po- 
 lished steel, with ivory points, serve for the 
 smaller platinum weights, which, for conveni- 
 ence of handling, should be turned up at one 
 corner, as at #, Fig. 80. 
 
 The box should be closed after each weighing, and, to preserve 
 it from the corrosive vapors that may be floating about, should be 
 kept in the drawer of the balance-table. 
 
 Fig. 80, represents a box of weights and all the necessary ap- 
 purtenances. The ribs, a a a, 
 fitted to the interior of the top. Flg- 80 " 
 
 by pressing against them when 
 the box is closed, %eep the 
 weights in their places. The 
 fork and forceps are shown in 
 place at b b. The channel df, 
 kept always covered with a 
 thick glass plate, contains the 
 platinum weights, an extra quantity of the smaller of which are 
 kept in the cavity e. When the weights are in constant use for 
 the day, they may be, during that period, kept on a small stand 
 under a glass cover near the balance-pan, as shown in Fig. 75. 
 This will save the inconvenience and delay of repeated transfers 
 . to and from the box and balance. 
 
 Small weights may be made, by first determining the weight 
 of a given length of wire of uniform thickness throughout, and 
 then dividing it into perfectly equal parts ; the number of the 
 divisions or angles indicates the fraction of the original weight 
 which they represent as a whole ; for instance, if the wire weighed 
 ten grains, and is divided into 10 or 20 portions, each fraction 
 will represent a grain or half grain, accordingly. 
 By using wire of greater thickness, weights of aug- lg ' 
 
 mented value can, in like manner, be made and I I Z\ I I 
 
 adjusted. This form, as shown (Fig. 81), is that 
 
120 WEIGHING. 
 
 in which all weights below ten grains are now, generally, 
 made. 
 
 Shot, of which there should be a box of the several sizes kept 
 in the balance table-drawer, are convenient counterpoises for 
 tubes, capsules, crucibles, watch-glasses, and other receptacles 
 for substances to be weighed. 
 
 CHAPTER VII. 
 
 WEIGHING. 
 
 THERE are certain preliminaries to be observed in all delicate 
 weighing operations, of which the most important is to ascertain 
 whether the balance is in order, as regards equilibrium and free- 
 dom of oscillation. To do this, each dish should be loaded nearly 
 to the full extent of the power of the balance. If, when the 
 beam is put in action, there is no perceptible variation in the 
 dishes, the equilibrium is perfect. For further verification, there 
 should be an exchange of loads, from one dish to the other, and 
 the beam again set in motion. The recovery of the equilibrium, 
 after the cessation of the vibrations, indicates the correctness of 
 the balance. The need of more than a milligramme for the ana- 
 lytic balance, or of T ^ th of a milligramme in the more delicate 
 balance, to restore a deficiency in either dish, should condemn 
 the instruments for quantitative examinations, unless previously 
 adjusted. This is done by the addition of bits of tin-foil to that 
 dish which is lightest. When, however, the balance is carefully 
 used, and by but one operator, it will be only necessary to re- 
 assure himself of its equilibrium in those weighings where abso- 
 lute accuracy is all-important. Be careful, however, in adjusting, 
 as well as in weighing, that the weights in the pan do not over- 
 load the balance and make it set, an effect the more prompt, in 
 proportion to the greater accuracy and sensibility of the balance. 
 The setting, which makes one scale appear heavier than the 
 other, is a permanent depression of the lowest pan by the slight- 
 est impulse to the exactly horizontal beam of a surcharged 
 balance. Hence the necessity of loading the balance within the 
 limit of its maximum power. 
 
WEIGHING. 121 
 
 In all weighing operations, the counterpoising of substances is 
 more speedily attained, and with less injury to the balance, by 
 systematically following a weight, which is removed from the 
 pan as too heavy, by the next in succession, until equilibrium is 
 obtained. Thus, in balancing a watch-glass, if the 20 grain 
 weight drags the beam, replace it by the 15 ; if this is still too 
 much, use the 10 weight ; and if this is too little, make up the 
 deficiency with the smaller weights, by adding them consecutively, 
 and decreasing gradually their denomination as the counterpoise 
 is approached. 
 
 To preserve the accuracy of the balance, it should be put out 
 of action upon every addition, removal, or substitution of weights. 
 As a precaution against error, the weights must always be re- 
 moved from the pan and spread upon white paper to be counted ; 
 and to verify the aggregate, in putting them away, their denomi- 
 nations should also be compared with their value, as marked upon 
 the vacancies which they occupy in the box in which they are 
 kept. The slips of paper and porcelain slate, in the table- 
 drawer, serve to make notes of their amount, which should be 
 done before placing them in the box. 
 
 A provision against inaccuracy, from very slight inequality of 
 the arms of the beam or imperfect equilibrium from other causes, 
 is the invariable use of the same pan for the reception of the 
 substance to be weighed. By this practice, notwithstanding the 
 difference in the weights of the two dishes, the ratio being kept 
 uniform, the quantities will be proportionably augmented or de- 
 creased, so that the products of analyses can be as accurately 
 estimated as in a perfect balance. An alternate use of the pans 
 for the weights and the substance to be weighed, will, on the 
 contrary, lead to results too high or low, as the case may be. 
 We, however, obtain, in this way, only the relative weight of the 
 substance, and not its absolute weight, which requires a perfect 
 balance. 
 
 Borda proposes to avoid the errors of inaccurate balances, by * 
 first taking the tare of the substance with that or any other 
 counterpoise, and afterwards substituting, in its stead, weights 
 sufficient to restore the equilibrium, which was disturbed by its 
 withdrawal from the dish. The sum of these added weights re- 
 present exactly that of the substance being weighed. This mode 
 
122 WEIGHING OF SOLIDS. 
 
 is termed double weighing, and affords very nice results even in 
 balances with disproportioned beams. 
 
 In weighing with the Berlin, or any balance having the arms 
 of its beam graduated into decimal divisions, all weights less than 
 the tenth of a grain, or the one-hundredth of a gramme, may be 
 dispensed with, as the riders, heretofore described at p. 118, are 
 much more convenient, and afford very prompt and accurate re- 
 sults. 
 
 They are looped forks of fine gilt wire, Fig. 82, weighing 
 
 exactly ! of a grain for grain 
 Fig< 82> weights, and -01 of a gramme for 
 
 gramme weights. As the value of 
 its weight upon the beam depends 
 upon its distance from the point of 
 suspension of the latter, it must be placed thereon, and moved 
 along from division to division until the exact point is attained, 
 by means of the arm and knob mentioned at p. 112. For example, 
 the weight of the rider being one-tenth of a grain, it expresses at 
 division one, one-hundredth placed in the pan ; at division two, 
 two-hundredths, and so on. To obtain intermediate values, the 
 decimal divisions of the arm must be further subdivided. In the 
 use of gramme weights, the rider being exactly -01 of a gramme, 
 any weight, from a centigramme downwards, may be determined 
 in the manner just mentioned. 
 
 Weighing of Solids. The balance being in perfect order and 
 repose, the next step is to counterpoise the vessel in which the 
 substance, which should in no instance be placed upon the naked 
 dish, is to be weighed. Circular disks of highly glazed paper 
 are sometimes used as recipients, but being attractive of mois- 
 ture, are preferably replaced by a watch-glass, or crucible of 
 platinum or of porcelain. The recipient being placed upon the 
 pan, appropriated exclusively for the purpose, is then accurately 
 counterbalanced by shot or fragments of metal. In analyses, 
 the counterpoise must be preserved for future references. They 
 may be either wrapped in paper or enclosed in paper pill-boxes, 
 but in either case must be labelled. In delicate analyses, to 
 avoid error, the tare of the vessel should be estimated in weights, 
 and their amount immediately noted down, to be afterwards sub- 
 tracted from the combined weight of it, and the substance 
 
WEIGHING OF SOLIDS. 123 
 
 weighed. The tare of the drying tubes, or of Liebig's and other 
 apparatus used in organic analysis requiring to be weighed, to 
 prevent mistakes, should be labelled upon the implements them- 
 selves with which it corresponds. This done, the substance is 
 introduced into the recipient, if in lumps, by means of a pair of 
 forceps with platinum points ; if in powder, with an ivory, horn, 
 or platinum spoon or spatula, accordingly as it may be inert or 
 corrosive. The blade of the spatula should never be of steel, as 
 it is so liable to oxidation. A slip of very thick sheet platinum, 
 one inch in width and two inches long, fastened in a wooden or 
 metallic handle, is generally used. Its usefulness for this pur- 
 pose may be increased by alloying it with a very minute portion 
 of silver, which increases its elasticity in an eminent degree. 
 The weights are added to the opposite dish, and always after 
 throwing the beam out of action, through the side-door of the 
 case, which must be immediately closed after each addition. If, 
 when the balance is lifted from its supports, by means of the 
 thumb-screw or lever, the index needle turns rapidly towards the 
 dish opposite to the weights, the balance must be put in repose, 
 another weight added, and the motion of the needle again exa- 
 mined. This operation should be repeated upon the addition of 
 each weight, however small. As the pans approach equilibrium, 
 the vibrations of the needle decrease in rapidity, and a little ex- 
 perience and observation will enable the operator to determine 
 the right point after one or two trials. When any given quan- 
 tity of a substance is to be weighed, the requisite weight should 
 be placed in the dish first, and the substance, if in powder, de- 
 posited in the other dish with a spoon or spatula, until an accu- 
 rate counterpoise is obtained ; taking care, however, to bring the 
 balance at rest upon each addition of material, which may be 
 made to fall in very minute quantities from the spatula by gently 
 tapping against its handle with the finger. 
 
 Those substances which are hygroscopic, should be weighed in 
 a covered vessel ; for instance, between two -watch-glasses, Fig. 
 83, or in a small tube with a ground stopper, which may be held 
 in an upright position by a loop of platinum wire slipped over 
 the suspending wire of the pan, or by a cork and wire stand, as 
 shown by Fig. 84. 
 
 The more delicate balances have for this purpose, for that of 
 
124 WEIGHING OF LIQUIDS. 
 
 organic analysis and of weighing substances in water, a supple- 
 mentary pan, with a hook beneath, for convenience of suspension, 
 
 Fig. 83. 
 
 This pan, which descends from the beam only one-half the dis- 
 tance of the other, is shown in the chapter upon SPECIFIC GRAVITY. 
 After the weighing is completed, the weights, as before 
 directed, are withdrawn with forceps, placed upon a piece of 
 white paper, and their several amounts added together; the 
 total gives the weight of the substance in the opposite dish. 
 
 Covered vessels are also requisite for those corrosive sub- 
 stances, the exhalations from which would be injurious to the 
 balance, and impair its accuracy. 
 
 Substances should never be weighed whilst hot, even in closed 
 vessels, otherwise the ascending current of air thus produced 
 draws after it a current of cold air, and not only promotes an 
 unequal expansion of one arm of the beam, but also an upward 
 motion to the pan, which will lead to error. A crucible, therefore, 
 which has been over the lamp for the ignition of its contents, 
 should be first cooled by standing upon the iron slab accompany- 
 ing the balance-table, otherwise its hot weight, not corresponding 
 with its cold weight, would, in estimating the result, lead to an 
 error in the real weight. 
 
 Weighing of Liquids. The nature of liquids, especially their 
 temperature and volatility, have an important influence upon the 
 precision of the results. 
 
 Non-volatile liquids may be weighed in a counterpoised cap- 
 sule, watch-glass, flask, or tube. Those vessels which have 
 spherical bottoms are supported in the pans upon cork rings, 
 which are readily made by hollowing out a cork and 
 bevelling its upper edges interiorly. If the recipient 
 is tall, it requires a stand to maintain it in an upright 
 position. This stand, shown by Fig. 84, is nothing 
 more than a disk of cork 6, with the wire-catch <z, 
 fastened to it. An excellent substitute is a broad 
 cork, with a hole in its centre, corresponding with the 
 
WEIGHING OF LIQUIDS. 125 
 
 size of the tube, and bored smoothly and nearly through the 
 cork with the cork-borer hereafter to be described. The use of 
 the wire-loop, before mentioned, is less safe and convenient for 
 suspending these vessels. 
 
 The liquids are conveyed to the recipients in dropping-tubes 
 or pipettes. This mode allows their gradual addition, and in 
 small quantities. 
 
 Any excess of the liquid, preventing a perfect adjustment, 
 may be removed from the recipient with an empty pipette in the 
 same manner as it was introduced. With a little precaution in 
 the management of the pipette, the flow may be made so gradual 
 that it can be arrested as soon as the vessel has received the re- 
 quired quantity. The insertion of slips of bibulous paper serves 
 to withdraw any slight excess, unless the liquid is corrosive and 
 acts upon paper, in which case, a glass rod must be substituted. 
 The insertion of this rod into the liquid, and its subsequent with- 
 drawal, causes a loss thereto of the small adherent quantity, and 
 thus we have a means of accurately weighing any required quan- 
 tity of liquid. 
 
 The stock of pipettes should consist of several sizes. After 
 being used, they should be carefully laid across a porcelain plate, 
 there to remain until the completion of the weighing, when they 
 must be well rinsed out previous to being returned to their places 
 in the drawers. 
 
 All volatile substances must be weighed in the small, closely 
 stoppered flasks, tubes, sealed glass bulbs, or other vessels, pre- 
 viously counterpoised. To insure accurate results, care must be 
 taken that the temperature does not fayor volatilization. Fuming 
 liquids should, if possible, be measured. 
 
 Very deliquescent substances, such as are not checked in their 
 liquefying tendency by the greatest practicable dryness of the 
 balance-case, and are not alterable by water, should be weighed 
 in solution. First, pour into the counterpoised recipient a suffi- 
 ciency of water, and note its weight. The increase of weight 
 given to this water by the addition of the deliquescent body, is 
 the actual weight of the latter, and the solution can be used in 
 the analysis instead of the solid. In some instances, according 
 to the nature of the substance, alcohol, or other more appropriate 
 liquid, may be substituted for water. 
 
126 
 
 WEIGHING OF GASES. 
 
 Fig. 85. 
 
 Fig. 86. 
 
 Weighing of Gases. In weighing gases, it is necessary, in 
 order to obtain nice results, to guard against the least variations 
 of temperature, pressure, and humidity of the atmosphere. Gases 
 are readily estimated by means of a very sensitive balance, 
 though the old plan, by measurement of volume in graduated 
 vessels, is accurate and easily executed. 
 
 Gases are weighed in counterpoised balloons, which must be 
 thoroughly cleaned and dried, and wiped exteriorly and interiorly, 
 so as to remove every particle of grease, dirt, or dust. The bal- 
 loon is then to be connected by a coupling-cock fitted to its neck, 
 with an air-pump Fig. 47, or syringe, Fig. 86, and exhausted of its 
 air. To insure the expulsion of all remnants of gas from a former 
 weighing, the balloon should be subjected to repeated alternate 
 exhaustions and airings. The exhausted balloon is then to be 
 attached to a graduated bell-glass, also fitted with a coupling- 
 cock, as shown by Fig. 85. This bell- 
 glass is the reservoir of the gas which is 
 received or collected over (see PNEUMATIC 
 TROUGH) water or mercury. Communi- 
 cation between the balloon and bell-glass, 
 being made by opening thein connecting- 
 cocks, the gas rushes from the latter into 
 the former by force of atmospheric pres- 
 sure upon the mercury. When the bal- 
 loon is filled, the flow is to be stopped by 
 closing the cocks. A delay of several 
 minutes is necessary (see MEASUREMENT 
 AND TRANSFER OF GASES) to allow the 
 temperature within the bulb to become that of the external air, 
 that the level within and without the bell-glass may be equalized, 
 and the quantity of gas noted. The balloon must then be de- 
 tached, and again weighed with care and accuracy. The diffe- 
 rence between its present and original weight, is that of the 
 volume of gas which it contains. 
 
 In the weighing of gases, it is indispensable to note the tem- 
 perature and barometric pressure, and to observe all other con- 
 ditions and precautions requisite in the MEASUREMENT OF GASES. 
 Those gases which are without action upon mercury, ought to 
 be collected over that metal, for most gases, by contact with 
 water, absorb more or less of its vapor, according to the tempera- 
 
WEIGHING OF GASES. 
 
 127 
 
 ture ; and, therefore, to insure correct results, it is generally 
 preferable to purify the gas of moisture previous to weighing it. 
 This is done by passing it through a tube (see DESICCATION OF 
 GASES) containing fused chloride of calcium, or some other ab- 
 sorbent substance. 
 
 It must be remembered, however, in the desiccation of gases, by 
 transit through tubes containing absorbent matter, that the quan- 
 tity of dry gas, entering into the globe, is less than that received 
 from the bell-glass, the volume of vapor abstracted in its passage. 
 To determine the amount of this loss, " observe the temperature 
 of the moist gas, and correct its volume by the pressure of thirty 
 inches of mercury. Then, by the table below, ascertain the pro- 
 portion of vapor which was present in the volume which left the 
 jar, and subtract it from the corrected volume ; the remainder 
 will be the volume of dry gas whieh has entered the globe." 
 
 The table, taken from Faraday, " exhibits the proportion by 
 volume of aqueous vapor existing in any gas standing over or in 
 contact with water, at the corresponding temperatures, and at 
 mean barometric pressure of thirty inches." 
 
 40 
 
 00933 
 
 51 
 
 01380 
 
 61 
 
 01923 
 
 71 
 
 02653 
 
 41 
 
 00973 
 
 52 
 
 01426 
 
 62 
 
 01980 
 
 72 
 
 02740 
 
 42 
 
 01013 
 
 53 
 
 01480 
 
 63 
 
 02000 
 
 73 
 
 02830 
 
 43 
 
 01053 
 
 54 
 
 01533 
 
 64 
 
 02120 
 
 74 
 
 02923 
 
 44 
 
 01093 
 
 55 
 
 01586 
 
 65 
 
 02190 
 
 75 
 
 03020 
 
 45 
 
 01133 
 
 56 
 
 01640 
 
 66 
 
 02260 
 
 76 
 
 03120 
 
 46 
 
 01173 
 
 57 
 
 01693 
 
 67 
 
 02330 
 
 77 
 
 03220 
 
 47 
 
 01213 
 
 58 
 
 01753 
 
 68 
 
 02406 
 
 78 
 
 03323 
 
 48 
 
 01253 
 
 59 
 
 01810 
 
 69 
 
 02483 
 
 79 
 
 03423 
 
 49 
 
 01293 
 
 60 
 
 01866 
 
 70 
 
 02566 
 
 80 
 
 03533 
 
 50 
 
 01333 
 
 
 
 * 
 
 
 
 
 This table is also useful for determining that part of the 
 volume and weight of a moist gas y due to aqueous vapor after it 
 has been weighed without previous desiccation, for as it " includes 
 any temperature at which gases are likely to be weighed, the 
 proportions in bulk of vapor present, and consequently of the 
 dry gas, may easily be ascertained. For this purpose the ob- 
 served temperature of the gas should be looked for, and opposite 
 to it will be found the proportion in bulk of aqueous vapor at a 
 pressure of 30 inches. The volume to which this amounts should 
 be ascertained and corrected to mean temperature. Then the 
 
128 WEIGHING OF GASES. 
 
 whole volume is to be corrected to mean temperature and pres- 
 sure, and the corrected volume of vapor subtracted from it. This 
 will leave the corrected volume of dry gas. It has been ascer- 
 tained, in a manner approaching to perfect accuracy, that a cubic 
 inch of permanent aqueous vapor corrected to the temperature of 
 60, and a mean pressure of 30 inches, weighs 0-1929 grains. 
 The weight, therefore, of the known volume of aqueous vapor is 
 now easily ascertained, and this being subtracted from the weight 
 of the moist gas, will give the weight of the dry gas, the volume 
 of which is also known. 
 
 " As an illustration, suppose a gas standing over water had 
 been thus weighed, and that 220 cubic inches at the temperature 
 of 50 Fahr., and barometric pressure of 29-4 inches had entered 
 into the globe and caused an increase in weight of 101-69 grains. 
 By reference to the table it will be found that at the temperature 
 of 50, the proportion of aqueous vapor in gas standing over 
 water is '01333, which in the 220 cubic inches will amount to 
 2*933 cubic inches, which, corrected to the temperature of 60, 
 becomes 2*942 cubic inches. The whole volume corrected to 
 mean temperature and pressure will be found to equal 219-929 
 cubic inches, from which, if the 2*942 cubic inches of aqueous 
 vapor present be subtracted, it will leave 216*987 cubic inches as 
 the volume of dry gas at mean temperature and pressure : 2-942 
 cubic inches of aqueous vapor weigh *5675 grains, for 2-942x 
 0-1929 = 0-5675 ; this subtracted from 101*69, the whole weight, 
 leaves 101*1225 grains, which is the weight of the 216-987 cubic 
 inches of dry gas ; and by the simple rule of proportion, there- 
 fore, it will be found that 100 cubic inches of such gas, when 
 dried and at mean temperature and pressure, will weigh 46*603 
 grains. 
 
 " It is not necessary in this experiment that the globe or flask 
 be perfectly exhausted of air before the gas be admitted, all that 
 is necessary in that respect being, that the quantity of gas which 
 enters, and the corresponding increase of weight, be known. For 
 the same reason it is not necessary that the globe be filled, pro- 
 vided the quantity which does enter is ascertained upon the gra- 
 duation of the jar when the level is the same inside and outside ; 
 and that no alteration of the quantity in the globe be allowed 
 before the weighing is completed. The state and quantity of the 
 
DETERMINATION OF SPECIFIC GRAVITY. 129 
 
 gas are estimated in the jar, and it is there that the temperature 
 and pressure should be attended to. It is essentially necessary 
 that the temperature of the globe over the water should have 
 been steady for some time before the experiment be made, and 
 that it does not change until the gas has entered the globe and 
 the stop-cock is securely closed. After that, a little variation of 
 temperature is of no consequence, so that nothing passes into or 
 out of the globe until the conclusion of the experiment. The 
 globe, as before said, should be clean and dry." 
 
 CHAPTER VIII. 
 
 THE DETERMINATION OF SPECIFIC GRAVITY. 
 
 BODIES which are of uniform bulk may vary in density, and 
 thus give rise to a difference in their specific gravity, the rela- 
 tion of their weight to their volume. The density of bodies is 
 estimated by certain standards ; that for solids being pure dis- 
 tilled or rain water (=1-000) at 62 F. The number, therefore, 
 expressing the specific gravity of a body is the number of times 
 it is heavier or lighter than an equal volume of water. For ex- 
 ample, if two bodies of equal bulk differ in density in the ratio of 
 one to two, the latter is said to have twice the specific gravity of 
 the former, and so in proportion. Therefore, "the volumes 
 being equal, the densities of bodies are directly as their weights ; 
 or, the weights being equal, the densities are inversely as their 
 volumes." 
 
 " Thus, if a cubic centimetre of iron weighs 7'8, while an equal 
 volume of water weighs only one gramme, 7'8 is the specific gra- 
 vity of iron." Hence, to find the density or specific gravity of a 
 solid substance, its absolute weight must be divided by the weight 
 of an equal volume of water. 
 
 SPECIFIC GRAVITY OF SOLIDS. By means of the Balance. 
 The two principal operations for estimating the specific gravity 
 of a solid heavier than water, are: first, to weigh it accurately 
 in air ; and, secondly, to weigh it in water. The weight at each 
 weighing must be immediately noted in the record book. 
 
130 
 
 SPECIFIC GRAVITY OF SOLIDS. 
 
 All of the finer balances are provided with a supplementary 
 pan (Fig. 87), for these weighings in fluids. Though necessarily 
 but one-third the depth of the regular pans, it is accurately 
 made so as to exactly counterbalance either of them, and when 
 adjusted to the beam, in its stead, to maintain perfect equilibrium. 
 The hook beneath the pan is a convenience for the suspension of 
 the body to be weighed. This arrangement permits the weighing 
 of the body in air, and subsequently in water, without disturbing 
 it or the balance. The process is as follows : Suspend the body 
 to be weighed by a very fine platinum wire or unspun silken 
 thread, to the hook at the bottom of the supplementary pan, and 
 adjust this dish to that side of the beam from which the regular 
 dish has been removed to give place to it. There are substi- 
 tutes for platinum and silk, but being more permeable and less 
 capable of furnishing a very fine and strong thread, they do not 
 aiford such nice results in delicate experiments. This done, take 
 the weight of the body in air, observing the requisite precision in 
 WEIGHING, and note it down in the record book without delay. 
 To take the weight in water, it is then only necessary to convey 
 a beaker-glass containing that liquid immediately under the dish, 
 and carefully to immerse therein the suspended body. This ves- 
 sel must be of diameter sufficient to allow a 
 free play of the body without contact with its 
 sides. Fig. 87 represents the whole arrange- 
 ment. In introducing the body into water, 
 particularly if it presents rough surfaces, the 
 air attaches itself in bubbles, which must be 
 removed with either a camel's hair pencil or 
 wooden stick. These precautions being duly 
 observed, put the balance in action and take 
 the weight of the body, and immediately record 
 it. The apparent loss of weight represents 
 the weight of the bulk of water which the body displaces, and 
 hence we have the requisite data upon which to calculate its spe- 
 cific gravity, viz., its weight in air and the weight of its own bulk 
 of water. 
 
 Thus, for example, the body weighs : 
 
 Fig. 87. 
 
HYDROSTATIC BALANCE. 131 
 
 Grains. 
 
 In air, . '.., . 373 
 
 In water, 341 
 
 Loss, 32 
 
 By following the rule, and dividing the total weight by the 
 loss of weight in water, thus 37332, we have 1-165 as its spe- 
 cific gravity or density. 
 
 If the body is lighter than water, a weight of known magni- 
 tude and density is joined with it to sink it. The weight may 
 be a capsule, and form a part of the furniture of the balance for 
 this especial purpose. It should be cullendered to allow the free 
 escape of the globules of air adherent to the body, after receiv- 
 ing which, it should be suspended to the short pan as before 
 directed. 
 
 In this, as in the previous instance, the weight required to 
 re-establish the equilibrium disturbed by the immersion of the 
 body in water, expresses the weight of the volume of water dis- 
 placed. 
 
 "The rule, therefore, is from the difference between the 
 weight of the two in water and their weight in air, subtract the 
 difference between the weight of the heavy solid in air and its 
 weight in water ; the remainder is the weight of a quantity of 
 water equal in bulk to the light solid, from which the specific 
 gravity of the substance may be obtained by simple proportion. 
 
 "As an example, suppose the following case: 
 
 Grains. 
 
 1. The weight of the light solid in air, . . , - ., . ". . . 12 
 
 2. The weight of the heavy solid in air, ..... 22 
 
 3. The weight of the heavy solid in water, . . . . 19 
 
 4. The weight of both tied together in water, ..... . . 8 
 
 Then, from the weight of both in air (12-4-22), .' ..- . . 34 
 Deduct the weight of both in water, . . . , . . . 8 
 
 26 
 And from the remainder deduct 22 19=3, .... 3 
 
 Which gives the weight of the bulk of water displaced by the light 
 
 body alone, . ... . . . . . . 23 
 
 " The following proportion then affords the specific gravity of 
 the body : 
 
 As 23 : 12 : : 1- : O5217." 
 
132 STOPPERED FLASK. 
 
 If the substance is porous or in powder, its specific gravity is 
 better estimated by weighing it in the bottle (Fig. 89), after the 
 precaution of disengaging all adherent globules of air ; other- 
 wise it must, in following the preceding process, be weighed in 
 a capsule, counterpoised first in air and afterwards in water. 
 The water also should, before being used for this purpose, be 
 freed of any contained air by pouring it several times from one 
 vessel to another. 
 
 When the body is soluble in water, it must be replaced by some 
 other liquid of determined specific gravity, which is without 
 action. Olive oil, spirits of turpentine, and alcohol, are appli- 
 cable, one or the other, for most cases. 
 
 " The specific gravity of the substance is then found by the 
 following proportion : As the density of water is to the density 
 of the liquid used, so is the density of the substance in relation 
 to the liquid in which it is weighed as unity, to its density com- 
 pared with water as unity." 
 
 "By the above-described process, we find how much a certain 
 quantity of fluid weighs which has the same volume with the body 
 to be weighed, and when once the specific gravity of the fluid is 
 known, it is necessary to ascertain the weight of an equal volume 
 of water." 
 
 " Let it be assumed, that a piece of salt, which is insoluble in 
 oil of turpentine, weighs 0*352 gram., and displaces when put 
 into the glass 0-13 gram, of oil of turpentine. The specific 
 gravity of this fluid is 0-8725 ; 
 
 0-13 
 an equal volume of water will therefore weigh" =0-149, 
 
 0-8725 
 
 0-352 
 
 and the specific gravity of the salt is, therefore, =2-36. 
 
 0*149 
 
 The preceding mode of taking the specific gravity of substances 
 is founded upon the Archimedean law of hydrostatics, " that the 
 weight of a substance in any medium is less than its absolute 
 weight, by the weight of the bulk of the medium which it dis- 
 places, obviously its own bulk." It is, however, not wholly un- 
 objectionable, as it is liable to give inaccurate results. 
 
 2d. By means of a Stoppered Flask. In this mode of weigh- 
 
STOPPERED FLASK. 133 
 
 ing, which is very available for taking the density of minute bulks 
 of matter, and applies to bodies either heavier or lighter than 
 water, the same attention to temperature is requisite, as in the 
 preceding process. 
 
 The glass bottle, in which the body is to be weighed, is of form 
 as shown by Figs. 88, 89. Its stoppei should be round, slightly 
 
 conical, and accurately ground. To facilitate 
 
 c : - r Fig. 88. Fig. 89. 
 
 the egress of any excess of water, in case of 
 
 expansion by heat, and to enable it to sink 
 
 to a uniform depth in all positions, the centre 
 
 of the stopper should be perforated. The 
 
 precision with which the bottle and its stopper 
 
 are manufactured, 'has an important influence 
 
 in bringing out an exact result. This bottle is especially adapted 
 
 for taking the specific gravity of liquids, and its capacity may be 
 
 from 100 to 1000 grains of distilled water. 
 
 Three weighings are required in taking the specific gravity by 
 this mode. The flask is first filled with water, so as to exclude 
 all air, then conveyed to the balance and accurately counter- 
 poised. The body to be examined is then placed in the same 
 pan with the flask, and the balance being again set in action, the 
 weight of the body is expressed by the additional weight neces- 
 sary to produce equilibrium ; and that of the body and flask by 
 the whole weight. The substance being examined, is then placed 
 in the flask, which is again weighed, after having been wiped 
 clean, to free it from the displaced fluid which has flowed over 
 its sides. The third weighing is to determine the quantity of 
 water, which is a volume equal to its own bulk, displaced by the 
 immersed body. Having thus obtained the requisite data, we 
 calculate as follows : 
 
 The glass vessel with water weighs, 
 
 The body, 
 
 Both together, 17-576 
 
 "If, after throwing the body into the bottle, putting the stop- 
 per in, and weighing the whole together, we find it to be 17*316 
 
* * 
 
 AREOMETER. 
 
 grammes, the weight of the water forced out by the body must 
 be 17*576 17'316 0-26 gram.; consequently the specific 
 
 4-056 
 gravity of the body is = 15-6." 
 
 3d. By means of the Areometer. The areometer is an instru- 
 ment which may be conveniently substituted for the balance in 
 taking the specific gravity of solids. That known as Nicholson's 
 is most generally used. Muller describes the apparatus and the 
 mode of manipulating with it, clearly and concisely, as follows : 
 " To a hollow glass or metal body A, Fig. 90, a small heavy 
 mass B (a glass or metal sphere filled with 
 lead) is suspended, and superiorly there is 
 attached to it a fine stem supporting a plate 
 c, on which small bodies and weights may be 
 laid. The instrument floats vertically in the 
 water, because its centre of gravity is very 
 low in consequence of the weight B. The 
 instrument is so arranged that the upper part 
 of the body A projects above the water. If 
 now we lay the body, whose specific gravity 
 we would ascertain, upon the plate c, the 
 instrument will descend, and by adding ad- 
 ditional weight, we may easily make it sink 
 to the point/, marked generally by a line on 
 the rod. We remove the mineral or other 
 substance we have been using, and substitute 
 in its place as many weights as will again 
 make the instrument sink to D. If, in the 
 place of the mineral, we have had to lay on n grains, the weight 
 of the mineral is equal to n grains. 
 
 " If, in this manner, we have ascertained the absolute weight 
 of the mineral, the n grains must be again removed, and the body 
 laid in a basket placed between A and B. The instrument would 
 now again sink to D if the body laid in the basket had not lost 
 weight by being immersed in the water : we must, therefore, lay 
 on the plate the weight m grains, that the body may be immersed 
 to the mark. In this manner we obtain the absolute weight of 
 
ALEXANDER S METHOD. 
 
 135 
 
 the body n, and the weight of an equal volume 
 of water m ; the specific gravity we seek is, 
 
 therefore, . 
 m 
 
 " If, for instance, we have to determine the 
 specific gravity of a diamond, we must lay it 
 on the plate and add sufficient weight to make 
 the whole sink to D. If we find, after remov- 
 ing the diamond, that we must lay on 1*2 
 grains to cause the areometer to sink again 
 to the same point, the absolute weight of the 
 stone would be 1'2 grains. These weights 
 must be again taken away and the diamond 
 laid in the basket; then, in order to make 
 the instrument sink to D, we must add 0*34 
 grains more; the weight of a volume of water 
 equal in volume to the diamond is, therefore 
 0-34 grains, and the specific gravity required 
 
 1-2 
 
 Fig. 91. 
 
 IS 
 
 0-34 
 
 = 3-53." 
 
 4th. By Alexander s Method. Analogous 
 to the method by the bottle (p. 133), but ap- 
 plied inversely, is the mode proposed and 
 employed by J. H. Alexander, wherein the 
 precision attainable from the former by minute 
 weighings is compensated by the largeness of 
 the masses that can be operated with, and the 
 resulting accuracy that, other things being 
 equal, is always proportionate to the masses 
 employed. 
 
 For this an ordinary bolt-head of glass, as 
 shown in Fig. 91, is taken, and the weight of 
 its contents of distilled water at a fixed tem- 
 perature, filled to some convenient mark along 
 the stem, to serve as a zero-point, is carefully 
 ascertained. It is most convenient for use that this point should 
 be adjusted so as to give the weigh fin question at a round num- 
 
136 ALEXANDER'S METHOD. 
 
 her of grains, say 10,000 ; but in the abstract this is quite imma- 
 terial, and practically only serves to diminish the calculations. 
 Then the stem is divided by equal additions of mercury, in the 
 ordinary manner, into tenths, hundredths, and thousandths of the 
 capacity of the bulb and stem, below zero. The ten-thousandths, 
 which in ordinary cases will be between B J and T J of an inch, 
 are too confusing to be engraved upon the stem, but can be 
 readily estimated by the eye, or ascertained more precisely by a 
 paper or ivory scale of equal parts. 
 
 To use this implement, the specimen whose specific weight is 
 required is first reduced to masses of a size that will admit of 
 passing freely through the stem, arid the actual weight of the 
 masses determined as usual. The bolt-head is then filled with 
 water of a known temperature to any stand, and in general as 
 near zero and above it as convenient, and the stand noted. Then 
 the weighed masses are introduced through the stem, and the 
 stand of the water again noted. It is manifest that the difference 
 between the two stands is the aggregate volume of the masses 
 expressed by the volume of water they have displaced, and the 
 weight of these masses being already known we have both the 
 elements whose relation determines the sp. gr. sought; or, in 
 other words, we have the absolute weights of water and of the 
 substance in question, both under the same volumes, and it is 
 only necessary to divide the former by the latter to have the 
 specific gravity sought. 
 
 Thus, to take an instance, let the aggregate weight of sundry 
 masses of bituminous coal be 1512*5 grains ; the stand of the 
 water in the stem before their immersion be 1-0005 and after 
 immersion 1-2115. The difference of these readings, viz., 1-2115 
 1-0005 = 0-2110, multiplied by whatever number represents 
 the absolute weight of the unitary volume of water at zero, ex- 
 presses the weight of a volume of water equal to that of the coals 
 immersed ; and in this instance as the unitary weight is 10,000 
 gr. we have, by merely removing the decimal point, this weight 
 as 2110 gr. Then, this weight divided by the absolute weight of 
 
 the coals, or = 1-39504, the specific gravity sought. 
 
 151.2*5 
 
 Of course, this method requires the same corrections to be ap- 
 
ALEXANDER'S METHOD. 137 
 
 plied for the expansion of water as do all other methods, when 
 the temperature of the experiment varies materially from that at 
 which the scale of the instrument was originally adjusted. Such 
 correction here can be the most conveniently applied by using 
 respectively, according to the appropriate temperature, the fac- 
 tors in the third column of the following table as multipliers of 
 the sp. gr. obtained. In this table, the second column gives the 
 absolute sp. gr. of water, at various temperatures above that of 
 maximum density, and is universally applicable in all cases of 
 correction for temperature. The third column contains that sp. 
 gr. corrected on purpose for the expansion of the glass bulb. 
 
 Temp. 
 
 40 
 
 Absolute Weight of 
 Identical Volumes of Water. 
 
 . . r 
 
 Weight of Ide 
 Volume of Walei 
 
 . , . . I' 
 
 45 
 
 0-99997 
 
 :.-; *-T^ . I' 
 
 50 
 55 
 
 0-99986 
 0-999G6 . . f f - 
 
 ';;#' .*! i 1 ' 
 
 09999 
 
 60 
 
 0-99937 
 
 0-9997 
 
 65 
 
 H'\ : . 0-99899 
 
 0-9994 
 
 70 
 
 ;*,:'. 0-99853 .m^lllfe 
 
 ?j! W* . 0-9990 
 
 75 
 
 80 
 
 i . 0-99797 . . 
 O99733 . . wf 
 
 0-9985 
 = S -, . . 0-9979 
 
 85 
 
 0-99660 
 
 0-9972 
 
 Thus, in the example just seen, where the unitary weight of 
 the water had been adjusted at 40 F., if the observation had 
 been made at a temp, of 70 F. the sp. gr. first found would 
 have been compared with a fluid lighter by T Q OI) than water at 
 its max. density, and the corrected sp. gr. should be 1 -39504 X 
 0-9990 = 1-39364 to compare the coal with water at 40 F. 
 
 Of course, if an instrument of this kind should be adjusted to 
 a unitary weight of water at some other temp., say 60 F., re- 
 gard must be had in correcting to the proportion of the factors 
 above and below such temperature and to the consequent differ- 
 ence of sign. For all cases above, the correction diminishes the 
 result at first found ; for all cases below, it increases that result. 
 
 In general, on the Continent of Europe, specific gravities are 
 habitually referred to the temperature of water at its maximum 
 density, rarely to that of melting ice, or 32 Fahr. But in 
 England, the temperature of 62 Fahr., which is also the stand- 
 ard of their national weights and measures, is usually adopted ; 
 as a more practical point, and as one which, more frequently 
 
138 SPECIFIC GRAVITY OF BODIES SOLUBLE IN WATER. 
 
 occurring naturally, and more easily maintained artificially, tends 
 to diminish the necessity for tabulated or special reductions. It 
 is to be observed, however, that reductions under this system, 
 when they have to be applied, are more complicated and more 
 liable to errors of incaution. In America, the practice is not 
 uniform and cannot be said to be settled, further than in the 
 adoption by the Government of the temperature of maximum 
 density for our national standards. This adoption, coupled with 
 what has been already observed upon the English system, and 
 with the manifest advantages of referring wherever we can to a 
 natural zero, seems to justify the scale which has been taken in 
 the preceding table, and to warrant the uniform reduction to the 
 temperature of maximum density. 
 
 No account is here taken of the expansion, and consequent 
 diminution of density, which the body itself operated on under- 
 goes by an augmentation of temperature; both because in general 
 the rate of such expansion is unknown at the time, and because 
 it would be, unless the material be in very large quantities, nearly 
 inappreciable. 
 
 Specific Gravity of Bodies Soluble in Water. Besides this 
 method, whose results are perfectly accurate, if the liquid em- 
 ployed is entirely without solvent action on the body immersed 
 (as it may be either 1, because of natural affinities, or 2, because 
 of its being previously saturated with molecules of the body in 
 question), other modes have been devised and practised, as by 
 Say, Leslie, and Regnault, whereby atmospheric air is substituted, 
 and all contact with any possibly solvent liquid is avoided. The 
 problem upon which these last modes rest is the measurement of 
 the same volume either at constant or different temperatures, at 
 different pressures ; a problem -whose performance is quite prac- 
 ticable. It is manifest further, that such measurement can be 
 made irrespective of the capacity of the vessel employed, or, 
 what is the same, just as well when said vessel is empty of all 
 but air, as when it contains some solid body besides. If, then, 
 such measurement be made first, and once for all when the vessel 
 is empty, and then again at two different pressures when it con^ 
 tains the substance in question, the expansion at the lower pres- 
 sure being altogether that of the air contained, and being less in 
 
. 
 
 SPECIFIC GRAVITY OF FLUIDS. 139 
 
 amount than that of the higher, because the volume of air is less 
 by the aggregate volume of the substance in question, the dif- 
 ference between the two volumes reciprocally, indicated by the 
 two lower pressures respectively, must be the volume of the sub- 
 stance in question ; the ratio of which volume to its ascertained 
 weight is the specific gravity. 
 
 Such is the general principle of these modes, which are entirely 
 correct in theory, and furnish results of an accuracy proportfoned 
 to that of the apparatus and care in manipulation. Also, after 
 the apparatus has been once accurately tared, their application 
 requires less time than the former methods, which, in fact, is equi- 
 valent to taking two specific gravities, one of the liquid in con- 
 tact, the other of the substance immersed. But, on the other 
 hand, these modes require, either directly or indirectly, a simul- 
 taneous reading of the barometer, and also corrections for tempe- 
 rature, in order to realize their full precision ; which has formed 
 hitherto an obstacle to the general introduction of any of them 
 into ordinary laboratories. 
 
 SPECIFIC GRAVITY OF FLUIDS. There are three modes of de- 
 termining the specific gravity of fluids, which take precedence in 
 the following order, viz. : by the stoppered flask, the gravimeter, 
 and hydrometer. The first method yields the greatest accuracy, 
 and is that used in all nice investigations. 
 
 By the Flask. Any small ground stoppered flask or vial will 
 answer for the purpose. It must first be brought to the tempe- 
 rature of 60 F., then accurately weighed, and after the removal 
 of the stopper, filled with distilled water of corresponding tempe- 
 rature. The stopper is then to be inserted, and the water that 
 it displaces wiped from the sides of the vessel, which when dry is 
 again carefully weighed. Its increase of weight expresses that 
 of the bulk of water which it contains, and to save time and 
 trouble, should be marked with a diamond upon the neck of the 
 flask to serve for future experiments. 
 
 Glass flasks of this description are made by the manufacturers 
 especially for this purpose. Their capacities are arranged so as 
 to exactly receive a given quantity of distilled water expressible 
 by weight in round numbers. The sizes vary from 100 to 1000 
 grs., but in each instance they have a diamond scratch on their 
 
140 
 
 SPECIFIC GRAVITY OF FLUIDS. 
 
 Fig. 92. 
 
 necks showing the measure of their contained weight of water. 
 They have been previously described at p. 133, and are repre- 
 sented by Figs. 88, 89. The smaller one is 
 most used because of greater facility in hand- 
 ling. Moreover the quantities of fluid under 
 examination are generally limited, and hence 
 the convenience of a small flask, both on this 
 account, and because it is more easily weighed 
 in a delicate balance. 
 
 For the more volatile liquids, and those emit- 
 ting corrosive vapors, the bottle should be 
 constructed as shown by Fig. 92. A ther- 
 mometer is adjusted to the mouth, and forms 
 the stopper*, and there is an upright, lateral 
 tube, with an accurately-fitting cap. The first 
 enables the operator to take the temperature 
 at the moment of the experiment, and the 
 latter allows room for expansion of the liquid 
 without risk of loss by overrunning or evapo- 
 ration. 
 
 If the chemist prefers purchasing a flask to 
 graduating one himself, it must be verified as 
 above before being used, and if the weight of 
 its contents of water does not correspond with 
 the mark on the neck of the flask, or of the 
 flask and water combined with that of the 
 weight generally accompanying it as a con- 
 venient counterpoise, then the flask is not to 
 be relied on, and should either be corrected or rejected. 
 
 In either case the flask must be thoroughly cleansed, and after 
 each experiment should be repeatedly rinsed with distilled water, 
 so that it may be perfectly clean and dry when wanted for the 
 next operation. In emergencies, the interior may be dried by 
 placing the flask upon the sand-bath ; in this case, however, it 
 will be necessary to allow its temperature to fall again to 62 
 before using it. 
 
 Distilled water at 62 F..is the standard by which to estimate 
 the specific gravity of liquids. To take the density of a liquid, 
 
HYDROMETERS. 141 
 
 equal bulks of it and water are taken at the balance. The flask 
 having been graduated, its weight and that of the bulk of its con- 
 tents of water are already known ; it is, therefore, only necessary 
 to fill it with the liquid under examination at 62 F., to the mark 
 upon its neck, and after inserting the stopper, carefully weigh it. 
 Divide the weight thus found by the weight of the water (as in- 
 dicated on the flask) and you obtain the specific gravity of the 
 liquid. For example : 
 
 Grains. 
 
 The clean and dry flask weighs 400 
 
 Do. do. filled with pure water, at 62 . . . 900 
 
 Deduct the first from the latter and you obtain the weight of 
 the water 500. Supposing, then, that the same bulk of the 
 liquid weighs 412 grains, then 412 4- 500 = 0-824, its specific 
 gravity. 
 
 If the capacity of the flask is 1000 grains of water, and one 
 of that size, may well be used, when the stock of the liquid 
 under examination is not limited, the process is still easier. It 
 is then only necessary to fill it with the fluid and weigh it. 
 The weight obtained expresses its specific gravity ; thus, taking 
 mercury for example, a bulk of that metal equal to the bulk of 
 1000 grains of water, is 13,500 grains, and, therefore, these 
 latter numbers express its density, jcare being observed to advance 
 the decimal point three figures to the left, if the water is taken 
 as 1 instead of 1-000. 
 
 The vessel must, previous to weighing, be invariably wiped 
 dry exteriorly with a linen cloth, and to avoid any communica- 
 tion of heat from the hands, they should be gloved. 
 
 For determining the density of very minute quantities of rare 
 liquids, it will be necessary to have the aforementioned bottles of 
 miniature dimension, or else to replace them by glass bulbs. 
 
 If the fluid is volatile and readily vaporizable, it should, in 
 being raised to the proper temperature, be heated over a spirit 
 lamp, in a test tube ; taking care to keep the finger over its 
 mouth, during the heating and cooling, so as to prevent its being 
 unclosed. 
 
 By the 0-ravimeter. The density of fluids, whether heavier 
 
142 GRAVIMETERS. 
 
 or lighter than water, may be very conveniently and precisely 
 ascertained by the hydrostatic balance or any delicate beam, one 
 of whose arms is furnished with a metallic ball of 
 Fig. 93. known weight, and so connected as to be plunged 
 into the fluid in question. (See Fig. 93.) In the 
 laboratory of this University, this ball is pear- 
 shaped, of brass, heavily gilt to prevent any che- 
 mical action of the liquid upon it, and attached 
 by the finest platinum wire, the weight of which, 
 per inch, is also ascertained. It is manifest 
 that the absolute weight and the volume of any 
 body being constant, the apparent diminution of 
 weight it sustains, upon being immersed in any fluid, becomes 
 less, i. e., the counterpoise required becomes greater, just as the 
 density of the circumambient fluid diminishes ; and that in coun- 
 terpoising such a body, the ball, for instance, just spoken of, im- 
 mersed successively in fluids of different densities, we are obtain- 
 ing the weights of identical volumes of the fluids respectively, 
 and if one of those fluids be water, the technical specific gravities 
 of all the others. 
 
 The application of these principles, and the convenience of the 
 method itself, will be better seen by an actual numerical example 
 of determining the specific gravity of sperm oil. In this, the 
 temperature at the beginning and end of the observations was 
 constant at 64-5 F. ; the barometer stand 29-95 inches, so little 
 differing from the standard as not to be worth noting for correc- 
 tion. The counterpoise to the ball in air was 172-60 grains ; in 
 water, 118-70 grains; in the oil, 125-19 grains. The respective 
 differences between the first and the last two, viz., 53-90 grains 
 and 47-41 grains, give at once the ratio of the specific gravity of 
 the water to that of the oil, as 1 : 0-87959, which, if the circum- 
 tances in the cases of the two fluids were the same, would be 
 the final result. In point of fact, however, the circumstances 
 were not the same ; for the immersion of the platinum wire, 
 which weighed 0-047 grains per inch, was in the water 0-5 inch, 
 and in the oil 0-3 inch ; leaving 0-2 inch of wire, corresponding 
 to 0-0094 grains in absolute weight, less in the oil than in the 
 water. This surplus weight, of course, had to be borne by the 
 counterpoise, which it increased by its own amount ; leaving out 
 
GRAVIMETERF. 143 
 
 of the view the remote correction for the different displacement 
 by the constant mass of the platinum of varying volumes of water 
 and oil. It is, therefore, to be subtracted from the oil counter- 
 poise, or, what is the same, added at once to the 47*41 grains 
 loss of weight in oil ; making 47'4194 grains to be divided by 
 53-9 grains, the loss in water, and resulting in a quotient of 
 0-87977, the specific gravity of oil at 64-5 F., that of water, at 
 the same temperature, being considered unity. 
 
 But water is systematically unity only at its maximum density, 
 say 40 F., and oil increases in density 0-000423 for every de- 
 gree downward, at least to that temperature, and probably still 
 lower, until near its freezing-point. If, therefore, oil be taken 
 for unity at 40 F., its proportionate density at 64'5 F. will be 
 1 _ (0-000423 X 64-5 40) = 0-98964. That of water at 
 64-5 F., may be ascertained with sufficient precision from the 
 table just now given, by taking proportional parts between the 
 temperatures and densities there given. Thus, the difference 
 between 60 and 65 is 5, of which the difference between 65 
 and 64-5 is the tenth part ; also, the difference between the spe- 
 cific gravity corresponding, or 0-99937 and 0-99899 is 0-00038, 
 of which the proportional tenth part is 0-000038, or, say 0-00004 
 to be added to 0-99899, making the density of water at 64-5 = 
 0-99903. The final density of oil, then, at 40 F., will be to the 
 density at 64*5 F., in the inverse ratio of these proportionate 
 numbers; or fffgf 0-87977 = 0-88812, the ultimate specific 
 gravity of oil compared with water as !, both being at the tem- 
 perature of 40 F. Such is the mode of applying the reductions 
 in question, which belong universally to all methods of determin- 
 ing specific gravities. 
 
 By Nicholson s Areometer. " The specific gravity of liquids 
 may also be determined by Nicholson's areometer, Fig. 90. As 
 the instrument always sinks so far that its weight, added to the 
 weight upon the plate, is equal to the mass of liquid displaced, 
 we may, by the aid of this instrument, ascertain how much a 
 definite volume of water weighs. It is necessary, however, to 
 know the weight of the instrument itself. Suppose this weight 
 to be n, we must lay on some additional weight to make the in- 
 strument sink to D ; if we designate this addition by a, then is 
 n + a the weight of water displaced. 
 
144 HYDROMETERS. 
 
 " If we immerse the instrument in another liquid, we must lay 
 on another weight b in the place of a, to make the whole sink to 
 D ; b will be greater than a if the liquid be denser, and less than 
 a if it be lighter than water. The weight of the liquid displaced 
 is n + b ; but its volume is exactly as great as the volume of the 
 mass of water, whose weight is n -f a, because the areometer has 
 sunk equally deep in both cases. 
 
 " Suppose the instrument weigh 70 grains, we must add 20 
 grains to make it sink in water, and 1-37, that it may sink to the 
 point / in spirits of wine ; then the specific gravity of spirits of 
 
 . . 70 -f 1-37 n 7QO 
 
 wme M 7ir+^o = ' 793 - 
 
 By the Hydrometer. Hydrometers do not give very accurate 
 results, but they are convenient when time is an object, and no 
 great precision is requisite. Their action is based upon the 
 hydrostatic law, " that a floating body displaces its own weight 
 of the liquid in which it swims.' 1 
 
 The instrument consists of a glass stem A, with an air-bulb, 
 B, beneath, properly ballasted with mercury or shot, I). The 
 depth to which the hydrometer will sink in a liquid is proportioned 
 to its rarity, for the denser the liquid, the less of it will be displaced. 
 A properly graduated scale inserted within the stem or spindle, 
 Fig. 94. Fig. 95. allows the appreciation of the density of a 
 liquid by the greater or less depth to which 
 it sinks therein. The form of this instrument 
 is shown by Figs. 94, 95. They are con- 
 structed with different scales, according as 
 they are intended for liquids rarer or denser 
 than water. The scales for those which are 
 rare run from zero (at the bottom of the 
 stem) upwards. The graduation of the scale 
 for liquids denser than water is reversed. 
 
 Areometers are variously graduated for 
 different liquids, thus 
 
 Those for ether mark upwards from 10 to 50 
 
 " " spirits " u 10 to SO 
 
 CJ1, * gait* * downwards" to 40 
 
 -*. u acids ** ?>.*>- -* Oto75 
 * " syrups tf " " to 36 
 
HYDROMETERS. 
 
 145 
 
 The following table shows the specific gravity numbers corre- 
 sponding with Baume's areometric degrees : 
 
 LIQUIDS DENSEH THAN WATER. 
 
 LESS DENSE THAN WATER. 
 
 09 
 
 
 
 
 . 
 
 . 
 
 
 4 
 
 , 
 
 , 
 
 
 
 c ~" 
 
 i *j 
 
 .-*j 
 
 
 
 = Z? 
 
 s 
 
 U- Z? 
 
 
 
 J? 
 
 1 
 
 II 
 
 bo 
 
 i 
 
 rt 
 
 WO 
 
 1 
 
 I] 
 
 tBO 
 
 
 
 Q 
 
 n 
 
 OJO 
 
 bio 
 
 Q 
 
 Is 
 
 
 
 1 -0000 
 
 26 
 
 1-2063 
 
 52 
 
 5200 
 
 10 
 
 1 -0000 
 
 36 
 
 0-8488 
 
 1 
 
 1-0066 
 
 27 
 
 1-2160 
 
 53 
 
 5353 
 
 ''41 
 
 0-9932 
 
 37 
 
 0-8439 
 
 2 
 
 1-0133 
 
 28 
 
 1-2258 
 
 54 
 
 5510 
 
 12 
 
 0-9865 
 
 38 
 
 0-8391 
 
 3 
 
 1-0201 
 
 29 
 
 1-2358 
 
 55 
 
 5671 
 
 13 
 
 0-9799 
 
 39 
 
 8343 
 
 4 
 
 1-0270 
 
 30 
 
 1-2459 
 
 56 
 
 5833 
 
 14 
 
 9733 
 
 40 
 
 0-8295 
 
 5 
 
 1-0340 
 
 31 
 
 1-2562 
 
 57 
 
 6000 
 
 15 
 
 0-9669 
 
 41 
 
 0-8249 
 
 6 
 
 1-0411 
 
 32 
 
 1-2667 
 
 58 
 
 6170 
 
 16 
 
 0-9605 
 
 42 
 
 0-8202 
 
 7 
 
 1-0483 
 
 33 
 
 1-2773 
 
 59 
 
 6344 
 
 17 
 
 0-9542 
 
 43 
 
 0-8156 
 
 8 
 
 1-0556 
 
 34 
 
 1-2881 
 
 60 
 
 6522 
 
 18 
 
 0-9480 
 
 44 
 
 0-8111 
 
 9- 
 
 1-0630 
 
 35 
 
 1-2992 
 
 61 
 
 6705 
 
 19 
 
 0-9420 
 
 45 
 
 0-8066 
 
 10 
 
 1-0704 
 
 36 
 
 1-3103 
 
 62 
 
 6889 
 
 20 
 
 0-9359 
 
 46 
 
 0-8022 
 
 11 
 
 1-0780 
 
 37 
 
 1-3217 
 
 63 
 
 7079 
 
 21 
 
 0-9300 
 
 47 
 
 0-7978 
 
 12 
 
 0857 
 
 38 
 
 1-3333 
 
 64 
 
 7273 
 
 22 
 
 0-9241 
 
 48 
 
 0-7935 
 
 13 
 
 0935 
 
 39 
 
 1-3451 
 
 65 
 
 7471 
 
 23 
 
 0-9183 
 
 49 
 
 0-7892 
 
 14 
 
 1014 
 
 40 
 
 1-3571 
 
 66 
 
 7674 
 
 24 
 
 0-9125 
 
 50 
 
 0-7840 
 
 15 
 
 1095 
 
 41 
 
 1-3694 
 
 67 
 
 7882 
 
 25 
 
 9068 
 
 51 
 
 0-7807 
 
 16 
 
 1176 
 
 42 
 
 1-3818 
 
 ~fe8~" 
 
 1-8095 
 
 26 
 
 0-9012 
 
 52 
 
 0-7766 
 
 17 
 
 1259 
 
 43 
 
 1-3945 
 
 69 
 
 1-8313 
 
 27 
 
 0-8957 
 
 53 
 
 0-7725 
 
 18 
 
 1343 
 
 44 
 
 1-4074 
 
 70 
 
 1-8537 
 
 28 
 
 0-8902 
 
 54 
 
 0-7684 
 
 19 
 
 1-1428 
 
 45 
 
 1-4206 
 
 71 
 
 1-8765 
 
 29* 
 
 0-S848 
 
 55 
 
 0-7643 
 
 20 
 
 1-1515 
 
 46 
 
 1-4339 
 
 72 
 
 1-9000 
 
 30 
 
 0-8795 
 
 56 
 
 0-7604 
 
 21 
 
 1-1603 
 
 47 
 
 1-4476 
 
 73 
 
 1-9241 
 
 31 
 
 08742 
 
 57 
 
 0-7356 
 
 22 
 
 1-1692 
 
 48 
 
 1-4615 
 
 74 
 
 1-9487 
 
 32 
 
 0-8690 
 
 58 
 
 0-7526 
 
 23 
 
 1-1783 
 
 49 
 
 1-4758 
 
 75 
 
 1-9740 
 
 33 
 
 0-8639 
 
 59 
 
 0-7487 
 
 24 
 
 1-1875 
 
 50 
 
 1-4902 
 
 76 
 
 2-0000 
 
 34 
 
 0-8588 
 
 60 
 
 0-7449 
 
 25 
 
 1-1968 
 
 51 
 
 1-4951 
 
 
 
 35 
 
 0-8538 
 
 61 
 
 0-7411 
 
 The hydrometer is used with a tall glass jar (Fig. 
 96), which serves as a recipient for the liquid to be 
 tested. After having perfectly cleansed it of grease 
 and dirt with a cloth, it is to be placed in the jar, and 
 the liquor, first brought to 62 F., added. When it 
 becomes stationary, note the degree at which it stands. 
 For verification, raise it an inch or more out of the 
 liquid, and then let it gradually sink back again. If 
 it reaches the same point as before, the first observa- 
 tion was correct. In reading the divisions on the 
 scale, do not take that line where the liquid rises in 
 wetting the stem of the instrument, but note it at the 
 
 10 
 
 Fig. 96. 
 
146 
 
 HYDROMETERS. 
 
 Fig. 97. 
 
 real level, which is the curvature pro- 
 duced by the ascending motion of the 
 liquid against the sides of the spindle. 
 
 Hydrometers graduated by Baumk's 
 process are generally used. 
 
 By Ham's Method. This requires 
 the use of a special apparatus, by means 
 of which the air is made to take the 
 place of the balance. It is said to yield 
 accurate results with great promptness. 
 It consists of two glass tubes, A and B, 
 Fig. 97, 20 to 24 inches long, and with 
 bores of one-fourth to three-eighths of 
 an inch diameter. A semicircular brass 
 tube and cock C connect them at the 
 top ; and their lower ends, which are 
 left open, dip into two glass vessels or 
 beakers D E, one of which is to contain 
 distilled water, and the other the liquid 
 under examination. These latter are 
 supported by stands kept in adjustment 
 by the milled-headed screws F G, and 
 the bracket and nuts H. The scale I I 
 is divided into two hundred parts. By 
 increasing the number of divisions or 
 degrees to 2000 the instrument may be 
 rendered still more exact. 
 
 Distilled water being poured into one 
 of the beakers, and the liquid to be 
 tested in the other, air is to be drawn 
 from the tubes by attaching a syringe 
 to the cock C, until the lightest fluid is 
 nearly at the top of one of the tubes. 
 The surfaces of the two fluids in the 
 vessels D and E are then equalized, or 
 brought to a a by raising or depressing 
 the stands by means of the screws, as 
 may be required. The heights of the 
 fluids in their respective tubes will im- 
 
SPECIFIC GRAVITY OF GASES. 
 
 147 
 
 mediately show their relative densities, convertible into water at 
 1000 by simple proportion. 
 
 The liquids should be at 60 F., or some uniform tempera- 
 ture approximating that point, at the time of the experiment. 
 
 SPECIFIC GRAVITY OF GASES. The extreme lightness of gases 
 and vapors renders it inconvenient to compare their weight with 
 that of an equal bulk of water, and consequently air is taken as 
 the standard. 
 
 The mode of taking these specific gravities is thus concisely 
 and clearly described by Parnell: " From the careful experiments 
 of Dr. Prout, it appears that 100 cubic inches of atmospheric air 
 deprived of carbonic acid and aqueous vapor weigh 31-0117 
 grains, at 30 inches of the barometer, and at the temperature 
 of 60 F. ; from which observation it is easy to calculate the abso- 
 lute weight of any bulk of a gas from its specific gravity. Thus 
 the specific gravity of chlorine is found to be 2*47 ; to find how 
 much 100 cubic inches of that gas weigh at mean temperature 
 and pressure, we make use of the proportion, 
 
 As 1 :2-47:: 3T01 : 76-59; 
 
 therefore 100 cubic inches of chlorine weigh 76'59 grains. 
 
 The simplest method of obtaining the specific gravity of a 
 gas is the following : The object is to ascertain the weight of a 
 bulk of gas equal to the bulk of a known weight of air. For this 
 purpose, a light glass globe, furnished with a stop- 
 cock, is very accurately weighed, when full of air; 
 then exhausted of its air, by connecting it with an 
 air-pump, and weighed in the vacuous state. The 
 weight of the air withdrawn by the exhaustion is 
 thus ascertained. The globe, still vacuous, is con- 
 nected with a jar containing the gas (Fig. 98) 
 which is to be weighed, at the water or mercurial 
 trough ; the jar having a stop-cock at its top, 
 into which the stop-cock of the globe can be 
 screwed air-tight. On gently opening both stop- 
 cocks, a quantity of gas rushes from the jar into 
 the exhausted globe, equal in bulk to the air with- 
 drawn by the exhaustion, if the surface of the liquid 
 within the jar be brought to the level of that without in the 
 
 Fig. 98. 
 
148 SPECIFIC GRAVITY OF GASES. 
 
 trough, and the temperature of the air and the barometric pres- 
 sure have not varied during the experiment. The stop-cock being 
 closed, the globe is detached from the jar, and weighed. The 
 difference between its weight when containing the gas, and when 
 vacuous, is the weight of a bulk of the gas equal to the bulk 
 of air whose place it occupies, the weight of which has already 
 been determined. 
 
 Suppose the globe to lose 10-33 grains by exhaustion of air, 
 and, when exhausted, to gain 15*78 grains by admitting carbonic 
 acid gas ; then, assuming 1* as the density of air, we have the 
 proportion, 
 
 As 10-33 : 15-78 :: 1 : 1-527; 
 
 the specific gravity of carbonic acid gas is, therefore, 1'527. 
 
 Although thus simple in principle, the operation in its de- 
 tails is one of extreme delicacy. From the facility with which 
 gases undergo a change in their bulk through variations of tem- 
 perature and pressure, it is obvious that if the temperature and 
 barometric pressure vary during the course of the experiment, 
 corrections must be made. As an illustration of the necessary 
 corrections, suppose the bulk of air to weigh 12 grains at the 
 temperature of 60 F., and under a pressure of 30 inches bar. ; 
 and the same bulk of the gas whose density is required to weigh 
 20 grains, but at the temperature of 50 F., and under a pressure 
 of 28 inches bar. The points to be determined here are two : 
 
 1. Considering the volume of the air withdrawn and the gas 
 admitted as !, at the observed temperatures and pressures, what 
 would be the volume of the gas at the temperature and pressure 
 at which the air was weighed ? 
 
 And, 2, having obtained that volume, what is the corre- 
 sponding increase or reduction in the weight of the gas ? 
 
 Performed according to rules which are given in the note 
 below,* the results of these calculations are as follows : 
 
 * " 1. For Changes in Bulk by Pressure. The volume which a gas should pos- 
 sess at one pressure may be calculated from its known volume at another pressure, 
 by the use of the following proportion : As the pressure to which the gas is to be 
 corrected is to the observed pressure, so is the observed volume to the volume re- 
 quired. In the example in the -text (6), the pressure to which the gas is to be 
 reduced is 30 inches, the observed pressure 28 inches, and the volume is 1-019. 
 Then, as 30 : 28 : : 1-019 : 0-951. 
 
 U 2. For Changes in Bulk by Temperature. From the very recent experiments 
 
SPECIFIC GRAVITY OF GASES. 149 
 
 (a) A volume of gas equal to ! at 50 F. is equal to 1'019 
 
 at 60 F. 
 
 (b) A volume of gas equal to 1*019 at 28 inches of the baro- 
 
 meter is equal to 0-951 at thirty inches. 
 A volume of the gas, therefore, r equal to 0-951 weighs 20 
 grains ; a volume of air equal to ! at the same temperature and 
 pressure weighing 12 grains. Then, if 0-951 vol. weighs 20 
 grains, 1 vol. should weigh 21-03 grains ; and 
 
 As 12 : 1 :: 21-03: V75; 
 
 1-75 is, therefore, the density required. 
 
 The state of dryness of a gas is another circumstance which 
 interferes with its volume ; for which reason, due care should be 
 taken to insure either the perfect dryness of the gas, or its com- 
 plete saturation with moisture. In the latter case, the tempera- 
 ture must be noticed, and the observed volume reduced according 
 to the proportion of aqueous vapor capable of existing in the gas 
 at the observed temperature. The proportions of vapor by vo- 
 lume contained in one vol. of the saturated gas for temperatures 
 between 40 and 80 F. are expressed in the table at page 127. 
 A cubic inch .of aqueous vapor corrected to the temperature of 
 60, and at a pressure of 30 inches, weighs 0*1929 grains. 
 
 The preceding method of obtaining the density of a gas still 
 requires a slight correction from another circumstance, when the 
 temperature and pressure differ considerably at the time of weigh- 
 ing the air and at the time of weighing the gas ; but one so trifling 
 that it may, in general, be neglected. The necessity of this cor- 
 
 of M. Regnault, it appears that a volume of gas expands by heat ^ of its bulk 
 for each degree Fahrenheit. Hence, the volume of a gas at F. being 1, at any 
 
 higher temperature it is found by the formtila 1 -\ -- emp ' . The determination 
 
 459 
 
 of the volume of a gas at one temperature from its known volume at another tem- 
 perature may be attained by the following formula : Let t be the temperature 
 Fahrenheit at which the volume of the gas is observed ; t r the temperature Fah- 
 renheit to which the volume of the gas is to be reduced; x the observed volume 
 at t ; and xf the volume at t' required ; 
 
 "3. It is frequently necessary to combine corrections both for temperature and 
 pressure. In such a case, as in the example in the text, the reduction of volume is 
 first made for temperature, and that corrected volume is afterwards reduced ac- 
 cording to the pressure. 
 
150 SPECIFIC GRAVITY OF VAPORS. 
 
 rection arises from the impossibility of obtaining a perfect vacuum 
 in the globe ; and the remaining small quantity of air may oc- 
 cupy a different space when weighed with the gas, to that which 
 it occupied when the globe was weighed with air ; and conse- 
 quently the bulk of the gas admitted into the globe is not the 
 same as the bulk of the air withdrawn. If the amount of rare- 
 faction of the air in the exhausted flask is observed, by means of 
 a barometer gauge attached to the air-pump, the amount of the 
 remaining air may be calculated when the weight of the quantity 
 withdrawn is ascertained ; then the alteration to which it would 
 be subject in bulk by changes of temperature and pressure may 
 also be estimated, and a due allowance made on the bulk of the 
 gas admitted into the globe." 
 
 When the gas is corrosive in its action, as in the case of chlo- 
 rine, the balloon with its metallic cock must be replaced by a 
 glass flask, with a nicely-fitting ground stopper. This flask is to 
 be adjusted to a drying-tube connected with the vessel in which 
 the chlorine is generated. The bent end of the drying-tube 
 entering the flask should reach to its bottom. The disengaged 
 gas, in passing through the tube, parts with its moisture, and 
 reaching the flask descends to the bottom, and displaces the air, 
 which is expelled through the interstices at the mouth around the 
 tube. When the chlorine itself begins to escape, it is evidence 
 that all the air has been displaced, and the flask is then to be 
 slowly and gently detached from the apparatus and hermetically 
 closed with its ground stopper. 
 
 Fig. 99. 
 
 SPECIFIC GRAVITY OF VAPORS. The following method, devised 
 
SPECIFIC GRAVITY OF VAPORS. 
 
 151 
 
 by Dumas, is applicable to all substances vaporizing, without de- 
 composition, at temperatures less than the fusing-point of hard 
 glass. 
 
 Take a glass globe of about 12 to 16 oz. capacity, with a long 
 slender neck, wash it with distilled water, and carefully dry it, 
 either by slight warmth or by means of the exhausting syringe 
 and a tube filled with chloride of calcium. (Fig. 99.) After the 
 balloon is perfectly dry, its neck is to be drawn out to a narrow 
 tube, 6 or 8 inches long, and bent nearly at a right angle, as 
 shown at a, Fig. 100. The tip is then to be removed with a file, 
 
 Fig. 100. 
 
 and the mouth of the tube rounded (not closed) over the blow- 
 pipe flame. The globe full of air is now weighed, with great 
 precision, and afterwards warmed to expel a portion of its air. 
 This done, and the temperature and barometric pressure having 
 been observed, its beak is immediately dipped into the liquid or 
 melted* solid matter, and as the air within contracts by the cool- 
 ing of the bulb, which may be hastened by dropping ether on its 
 exterior, the fluid is drawn up. When the requisite quantity, 
 say 100 to 150 grains, has entered, the globe is at once enclosed 
 in a wire basket 5, Fig. 100, and introduced into a cast iron kettle 
 containing water for the bath, when the temperature is not to 
 
 * If the solid body is not fusible, a given weight of it is introduced into the globe, 
 previously dried. The neck is then drawn out, the end removed and placed in 
 the balance. By deducting its weight from that of the whole balloon, you obtain 
 the weight of the balloon full of air. 
 
152 SPECIFIC GRAVITY OF VAPORS. 
 
 exceed 212 F. Solution of chloride of calcium must be used 
 for temperatures near 250, neat's-foot oil when 300 is required, 
 and metal baths for higher degrees. The wooden support e, to 
 an arm of which is suspended the thermometer c, keeps the globe 
 firmly fixed in the bath. 
 
 The bath is brought to ebullition, and as soon as it rises above 
 the boiling-point of the substance, a jet of vapor escapes through 
 the tube, and as soon as it ceases, the point is quickly sealed up 
 over the blow-pipe flame, observing at the same time the tem- 
 perature of the bath and the barometric pressure. 
 
 The globe thus closed is then withdrawn from the bath, washed, 
 dried, and again weighed. 
 
 To determine the capacity of the balloon, its tube is dipped 
 into mercury, and its point broken under the surface of the 
 metal, which immediately rushes in and fills the vacuum caused 
 by the condensation of the vapor, and should occupy the whole 
 interior. It is evident that the volume of mercury represents 
 the volume of the vapor at the noted temperature, and this 
 volume is determined by transferring the mercury to a graduated 
 tube, and marking the number of cubic inches or centimetres 
 which it occupies. 
 
 We thus have all the data necessary for calculating the specific 
 gravity of the vapor, having determined, experimentally, 
 " 1. The weight of the globe and air at ordinary temperature 
 
 and pressure ; 
 
 " 2. The weight of the globe and vapor filling it at the tempera- 
 ture of the bath, and under ordinary pressure ; and, 
 " 3. The capacity of the globe. 
 
 " Haying these results, we obtain by calculation, 
 " 1. The weight of the empty globe (by knowing the capacity of 
 
 the globe, the weight of the air filling it can be calculated, 
 
 which, deducted from the weight of the globe and air, leaves 
 
 the weight of the globe when vacuous) ; 
 " 2. The weight of vapor filling the globe at the temperature of 
 
 the bath (by deducting the weight of the empty globe from the 
 
 weight of the globe and vapor) ; and, 
 " 3. The weight of air filling the globe at the temperature of the 
 
 bath, and at the pressure at which the globe was sealed* with 
 
 the vapor. 
 
SPECIFIC GRAVITY OF VAPORS. 153 
 
 " The last calculation is made according to rules given in the 
 note, pp. 147 and 148 ; having performed which, the density of 
 the vapor required is obtained by the simple proportion, As the 
 weight of air filling the globe at the temperature of the bath is to 
 the weight of vapor filling the globe at the same temperature, so 
 is 1 to the density required." 
 
 It is necessary to remark, that in the instances of organic sub- 
 stances which are sensitive to the decomposing influence of the 
 air at the temperature to which their vapors must be heated, in 
 order to obtain constant densities, the glass globe should be filled 
 with carbonic acid gas previous to heating the bath. The mani- 
 pulations, thereafter, are as already directed. 
 
 The following table of the densities of a large number of sub- 
 stances, and for which we are indebted to Th. J. Herapath 
 (Chemist, vol. 4), will be found very convenient for reference. 
 It comprises the most reliable results ; and in instances of doubt 
 or discrepancy, conflicting numbers are also given, with a note of 
 interrogation affixed to the most questionable. The * attached to 
 certain names is intended to indicate that the authority cited is 
 not responsible for the numbers, as they were merely quoted from 
 those writers. 
 
154 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 CO 
 
 o 
 S 
 
 CQ 
 
 
 
 CO 
 
 1 
 
 
 t^rtT*< 
 i ii iO^ 
 
 r-ioioopocvjpcnc'-p^ocp 
 
 . - 
 
 -- 
 
 
 o -- 
 
 S& 
 
 oO 
 
 (NO 
 
 X 2 
 
 > y> co m >o co 
 
 pi^i^i^oocS ptNco-^^^HppcnoippoopQooo 
 c<j co o o 1-1 i-i -^ o o o o o ^-< co co ^ ^-i ^ ^ ^-i o ^ ^-i ^ i- ^-i ^-i -^ 
 
 ^ r^ 
 
 lls^ 
 
 Eeo 8^ 
 
 
 
 i M 
 
 I il 3 
 
 CS CJ <U 
 
 Sou 
 
TABLE OF SPECIFIC GRAVITIES. 
 
 155 
 
 ffi m oj CQ 
 
 f- 00 CQ 
 
 O O O"i ^ 
 
 ^^69 
 
 **' 'lls|| -I?* 
 *"-' "oliis"'" 
 
 O ~ O O 
 
 .-. . r" --i -.-.-. . -.-.-.--. TJ D 9^C^^'9 ( ?' c ? :>< ? > T' J ^" t ^"9 < ?^9^ 3 ? 
 
 C^Mf^OCOCNCO^MOO^^^rtOOOO^CQOO^I^COCOCOCO^ic^^C^O* 
 
 03-0 
 
 S S 
 
 si 
 
 1.1 
 
 288 
 
 laiiis 
 
 o^ C3 r 3 &s 
 
 .<> 
 
 . 
 
 .- 
 
 ^3 J3 X3 O) .S 
 E.S S E 
 
 ^J i fc* ^ 
 
 S E E E 
 
 Q . ' 
 
 
 i- 
 
 O 
 
 -i ^ J2 o .2 
 
 K ^ o - 
 ~ a ">, 
 
 3= ^.r-3 1 
 
 .Sl Ss 
 
 c c 
 
 1 1 I'll 
 
156 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 i i CT> n i i to to r- to cy> 
 
 eg ' 6^ ~ 97- c* 4 
 
 " "wo'-o^^ ooo" 
 
 *i Or~*-O*OO --*-o 
 
 CO CO Tf <N CO M 
 
 . 
 
 cu O C- 
 
 *- rt ^- 
 
 . -2 
 
 . 
 
 ^ ho. 2 cu. 3 5 JS- 
 2s- P. >< M -, ^ 
 
 03 03 03 
 
 c-5 -o- 
 
 ig. 
 
 il 
 
 != E"0 
 
 
 cys CT> 
 
 COCT) <N 
 OOO 
 
 o r 
 
 (N^-( 
 
 2 .52. 
 
 ' 
 
 a c c c a 
 
 . 
 
TABLE OF SPECIFIC GRAVITIES. 
 
 157 
 
 H3* Q.*. (= o3 wl-5 
 
 c * 5 > 9 ss = fc 
 
 
 
 11*1: 
 
 S 
 
 01= g. 
 
 5 SO? B- 
 
 
 
 00 ^ 
 
 o o 
 
 CQ 
 
 o 
 
 :/s.-= t i 
 
 3 -* ' * 
 
 *r i g : 
 
 ss II a 
 
 OH OH Cob- 
 
 's 
 
 ._r * -- ;a 
 
 s? | -gg-S^a ?:-. 
 
 2 S <=" . " a 
 
 51? 11 3"Soc 
 
 .S o 
 CO 
 
 II 
 
 "5 J= 
 
 - . ~ Sc 5 e 1 
 
 Caj_ '=00. - .- 3 ^ x-T-S 
 ' ^' 
 
 
 *=l 
 
 C . C 
 
 
 
 Jlj 
 
 l|,llll^=y^l^ll : 
 
 -o- 
 
 o <N o c eo n n ao o cj 
 
 00 
 
 teas 
 
 i: Jr a ^ 
 
 3 
 
 CS 3 
 
 c 
 o 
 
 03 OH 
 
158 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 -T3 e 
 
 Ti 
 
 g* 
 
 Hffi 
 
 tCOHQ 
 
 s 
 
 o .0 o 
 
 2 ^ ^ Tf oo 
 
 o co m o m 
 
 
 CQCQ 
 
 CQCQ03CQ 
 
 s s 
 
 S2S2 
 
 CQCQ 05 CQ 
 
 CQ 
 
 P3 CQ CQ CQ CQ CQ CQ 
 
 J l*s filial gl^ 1 
 
 CBJ3 .JC-2 eo o>. o . ^ J3 
 
 KH^^HoiKcccQaJcscaQ- H 
 
 c^ "S ' 
 
 CO * * * C^) C9 O"i O ^ * 
 
 2 g P2SS s s 
 
 
 -5 
 
 Pnfr.car-t.c-i 
 
 J= C N G. c"o*- 
 
 5 2S-2S S8 
 
 ^MCQWQiffiP 
 
 2 
 
 ^ 
 
 <NO}.-it^N<N<NmOO 
 
 
 W 
 
 cq5 
 
 
 
 
 . 
 
 llil 
 
 S OOO 
 
 WCCPQCQ 
 
 . '8 > 
 18, 
 
 OO 
 
 CQCQ 
 
 E 
 
 OCOOOu, 
 
 pq 00 PQ M 03 CQ 
 
TABLE OF SPECIFIC GRAVITIES. 159 
 
 ..: 
 
 ' 
 
 - 
 
 Hg^-SS :5 
 
 OdoaPE-oipq 
 
 -ii I& 
 
 co cscscocsco cscscBcsco 'cococscoco 
 
 U 00000 00000 0000000000 
 
 
 :s i tir' 
 
 E- oo-HoHffi &&> WWcaHcoWa3 02 tCcQE^^m^ ffi 
 
 fc 
 
 f . GO <o eo i i o ** 
 
 * i . * S ?S 
 
 3 ' t -'B * * '* * <N ^^.(N 
 
 O O O O O O 
 
 
 i -I 
 
 ,r o? no 
 
 . 6 
 
 g'g 'Si ? 2's 
 
 -5 5c^ 
 
 CBC9 COCO CO COCO 00 
 
 DqqQKpQCQoq cqpq OO OO O OO O 
 
160 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 ** N S 
 
 s^itS 
 
 -0~ 5** 
 
 B 
 
 .2 * 
 
 *L 
 
 * S 
 
 >> w 
 
 cg^ 
 
 j=^s ja 
 HH o- 
 
 J 
 
 9 
 ' o 
 in f ^ 
 
 111 
 
 uoo 
 
 n 
 
 'i.I 
 
 oo 
 
 a. '-w 
 
 : I" I 
 
 ,= 
 o 
 
 ojaTlf Q).S"o'?'3 " *^ 
 
 &u sslo 
 
 5^S IS gS^E-S 
 
 _c ^r -- c c 5 c * = - : - 
 
 ooo" " oo ooooo 
 
 * - 
 
 S .8 S 
 
 * . 
 
 2S w 
 
 O 0> W O) C 
 
 .}%i*-m = -ssiSc 
 
 . 
 
 I- 1 e i V :aTr2 . 
 
 w 2 ' 
 
 ?1 
 
 'S ' 
 
 tc 
 
 05 ~ >- 
 
 
 QJ CLi 
 
 uo 
 
TABLE OF SPECIFIC GRAVITIES. 
 
 161 
 
 capL,5ttEHSit-'S3&ipqo pqeucQOQcL,WH 
 
 r-> 
 
 O O 
 
 ""co-Hr^^ 
 
 S 21 
 
 fi 
 
 oo 
 
 E E 
 ooo 
 OOU 
 
 r 
 8- s 
 
 o 
 O 
 
 
 a 
 
 a- Q 
 
 2 ? 
 
 3 
 
 <N 6 
 
 * 
 
 f > 
 
 - 
 
 S -rT ^ JB -y 
 
 -. =8 
 
 : 31 I 
 
 11 
 
162 TABLE OF SPECIFIC GRAVITIES. 
 
 2=-p 
 
 f s5 iii 
 
 "S S a a' 
 
 co 
 
 
 
 o - o 2 w o o 
 
 5O*' e8 00 *-* J ^^O*- > O *- -*-> 
 
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 OPu feua^^^EHQqKH iJS co So . HcnoJO>H O 
 
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TABLE OF SPECIFIC GRAVITIES. 
 
 163 
 
 - "C ^ X * * *-* QJ >- QJ * Q> 
 
 S afi 
 
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 O O O JS 33 3 
 
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 1 1 r o s 
 
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 5 - 
 
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 -2aiOO 03*2. 
 
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 o-o-'C 
 
164 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 
 
 1 
 
 s _. ^ j= 
 
 . <1 . ,r3 . . S-d'- ' 
 
 " 'c'S ' o 1 2i"S a'Scrf^S -1 g 
 
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 ^S '?? S rT g t^S 
 
 <j 
 
 
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 ^C C^ fcO ^* O^CTiiOO^OO^O 
 
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TABLE OF SPECIFIC GRAVITIES. 
 
 165 
 
 j 
 
 a 
 
 1 1 1 a . 
 l I Is** lal 
 
 Z--C 3 --G -co 
 
 o 
 
 -'s ! 
 
 1.1 1 
 
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 o a S gj 
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 O O 00* 
 
 "a ^ S c o5 
 
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 ^ -SJ-I 111 5 ! 
 
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 OiOOOOOOOOOO t^^^TjiOn<NiOOOOC<(<NniC(NC^C^CQ 
 
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 222 
 PQ ca pq 
 
 OO 
 
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166 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 B B B&arrid4 
 
 B 
 
 a 
 
 C3 
 
 HO 
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 C3 
 
 cs a 
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 j-l-rrf 
 
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TABLE OF SPECIFIC GRAVITIES. 
 
 167 
 
 Jl VV A JlLtl^i ^M 
 
 = 9 = = 5 .-3 . S s2_. 3_.-5 2... . J S^G S.ts 
 
 o 
 
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 S5 S 
 
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 II 5 
 
 So o oo 6 
 
 AfS 
 
 sa-s 5.1, 
 
168 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 m*t" 
 
 
 i! 
 
 00 
 
 .8 . 
 
 P,**oco:oc5**o2 o o en o o en 
 ~ ^ ^ IT o TT o TJ ~ 10 t- o i^ p op p g^ 
 
 
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 ^ ,. *-(^^o- o ** nrj --2 c * c 
 
 ^ -o SS"S' 
 
 o 3 
 
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 CQQQCQQH 
 
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 CO 
 
 Z oo 
 
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 co o 
 
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 cocvjcoooo fi -i 
 
 co 
 
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 09 . 
 
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 t o | c-= g "3 =-^ ; 
 
 oo ooooo ooooo'o 
 
TABLE OF SPECIFIC GRAVITIES. 
 
 169 
 
 O 
 
 co o 
 
 O^ O 
 
 oo c$ncooo*-t^oc-jookneo'*ooa-><r>ocoo>-- <c 
 cV* co co co w co <N OD 4c co co 6 o co o <N CQ co (N co w <N o IN 
 
 S a 
 
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 T s .2 
 
 S(3 CO 
 
 a ffi 
 
 ffiffiE 
 
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 050)050) Q5OOOOO 
 
 EEKffi ffiffitCEKE 
 
 "? J S-StS-n^ S 
 
 8 O * O & fi 'f O 
 
 
 
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 E'i J 
 
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 CO 00 QO 
 
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 CO 
 
 <N O ^H CM N M 
 
 9 g 
 
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 O "O m C -fl * 
 
 ,6^3 o 9 w ^-2 
 
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 S S S 
 
 333 
 
 OC3 
 
 o 
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 >, 3 3 >, 
 
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170 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 
 .c.. 
 
 
 
 
 
 ~ e " 
 
 c J 
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 * - 23 g 3 . . s .2 
 
 CO CT> -CO O <0 31 O CO 
 
 '* .*. -g,-* ?> 9 
 
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 i^H rt 00 CO -^H ^i OOOOO 
 
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 r r o * CQ <a 
 
 ?1U 111 s? ' ' *s ' ' 
 
 C oOn -co 03-C o w _T 
 
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TABLE OF SPECIFIC GRAVITIES. 
 
 171 
 
 11 
 
 . > 
 
 c d 
 
 ** 
 
 sn -> 
 SP 5- 
 
 -G 3 O > O 
 
 So" 
 
 fO <> 
 1 " H O 
 
 222 
 
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 NH? ip *.,*.! 
 
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 S 
 
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 B 
 
 ^-e"s 
 cj Cu GO 
 
 
 
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172 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 J2 
 
 3 
 
 5 1 
 
 12 2 j 
 
 . .-g-Hg- 
 
 . . 
 
 * - = 
 
 ~ 3 O 
 
 c c 
 
 c 2 * 6 
 
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 tiOin ' 
 
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 I.S Is 
 
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 jj 
 
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 * -a -2 ^ 
 
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 ^^O O fc" 1 03 CQ ^ P-i CQ Ct| ftrf ti CLi 1^ tJ^ an O DH ^ 33 CU 
 
 
 
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 h34< 
 
TABLE OF SPECIFIC GRAVITIES. 
 
 173 
 
 
 ... i 
 rti 
 
 "O 13 tJ 
 
 * il C C * 
 
 Kir! *. 5 G T3 c -d d 
 
 2->>i- >hnO ^ b*- i. o 
 
 
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 O 00 O O W OO O T* TO ~ O O 00 O 
 
 oo cin^Diooc^o>nriQO<x)c<( -' 
 
 o.ss : : 
 
 tls 
 
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 13 S cs 
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 l^Ot^^>-<Oy3>O 
 
 pc^ooooprr'n 
 
 CQ 4 C* M (A ** T 
 
 1 
 
 .os-e 
 
 QJ-C!*.- 
 
 C S 
 
 111 
 
 ' es-Q o^S' 
 
 c * 
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174 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 JS 
 
 |; = 
 C 
 
 OH 
 TJ 
 
 QJ 
 
 d d 8 1 
 
 set I -Si IllJil|li 
 = = *S|" I s .S-Sl Elsie's * 
 
 JS = 
 
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 QOOfiO(M<MOOi i i ii (Oi ifHC<JO< i I (MtOtOtOtO~' 
 
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 r ifcum- 
 
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 5*1 
 
 
 
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 r-i rj< oo 1 s - o 6 "i < i> j> OD Os oo OQ 
 
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 III-- Jill 
 
 O Q^ <U 0^ O 0} 03 
 
TABLE OF SPECIFIC GRAVITIES. 
 
 175 
 
 ocnooobobdoiooGb.dbobobobo>hobdooooooo 
 
 2 
 
 Ci oo oo t^ 
 
 
 
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 >o % 
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 O> < 
 
 -"* 3 o o 
 
 i i ^o Q 
 
 S -* 
 
 8-S 
 
 85 I 
 
 rl 
 
 M O 
 
 f 
 
176 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 o^: o 
 
 ^,0 ^ 
 
 <* % 
 
 "o ^ 
 
 O 
 
 CO CN CO Tf 
 <>> 00 ?> Oi 
 O CQ CO CJ 
 
 4fcos^< ; ib^-i- : -iT' : -ico4j<^-iAH 
 
 
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 oS 
 
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 s "is 
 
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 >,Sjs S^S^s 
 
 -j _c ^^ S3 ^ m CC >- C- - 
 
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 G 
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 ^ ;:^^6i6b"b" 9rrrsagc*j:^,v:r*r 'P'? 3 
 
 o i i oo <-*! i ^^r-i-i o o^^vo^oi^-r-t^t^'O'O '-<' loo^cvc^ot^- oo 
 
 liil 
 
 O -C 3-5 
 OH & tfj/2 
 
 *'o 
 
 '.i 
 
 s- 1 
 
 
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 TABLE OF SPECIFIC GRAVITIES. 177 
 
 ' 
 1 
 
 si-.il ^^ 5 sl II iiitlvfiiiiiiiirllig 
 
 OCsi" U j 1 * K^<3 2 O C 3 
 
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 "'ll 5 ' -a" ""-Si 
 
 ^^^ i- l's 
 
 12 
 
178 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 I 
 
 p 
 
 < 
 
 ft III'' *. .fill 
 
 If ||ilr^||lil^jiiiiriji||ii1|yi 
 
 co DioscL-wS o jBpiCtaoaSKHE-'ft ( G3S3SnSfe t 3oJiSflQSq 
 
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TABLE OF SPECIFIC GRAVITIES. 
 
 179 
 
 ir^i 
 
 J &2 
 
 :3S-g 
 
 cctncaoj 
 
 
 Q 
 
 
 
 
 
 
 
 
 *4-3 
 
 * 
 
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 ubstanc 
 
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 I ST55 
 
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 C'_Q * UCQJ^O ' qj C-- " 
 
 "t'lH a, - -~ - w *- ^5 5 OT 
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 - a- a, ^ cuo-ft-ft-ft-ft-- ft- ft- o-o- 
 
 
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 _o^-J 
 
 
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 c 01 (D -; 
 
 Ills 
 
 i- v. --Z w 
 
 caccpqca 
 
 P^ P^ fL, CU fL, PH PH O, 
 
 : 
 
 fefefefefefeOife 
 
180 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 Authority. 
 
 o o ja 
 
 "3 "5 "3 
 
 O O _ - 
 
 i-s i-s - - t-> - - 
 
 c c c 
 
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 Karsten. 
 
 1 
 
 cs 
 
 Playfair and Joule. 
 Filhol. 
 
 Anthon. 
 Karsten. 
 
 *3 
 O 
 
 'I 
 
 Gray.* 
 Thomson. 
 
 Mitscherlich. 
 
 3 
 O 
 
 Ml 
 
 IKopp. 
 Playfair and Joule. 
 
 1 
 
 C8 
 
 s 
 
 
 
 
 
 
 
 
 
 o 
 
 
 
 
 
 
 
 
 
 
 
 
 9) 
 
 CO 'CO '<N 
 
 O t *^oc^Tt*iriocoooo^* 
 S r-* o <3 <j o y>op 9* o ft S 
 
 000 
 CO 00 O 
 
 >o o> 
 
 >o '-p 
 
 OQ C<( 
 
 t.0 
 
 
 
 
 
 d\( 
 
 <N W 
 
 rf< ^ 
 ^ C3 
 
 ra oo 
 
 Cv( CM 
 
 CO W 
 
 oo >o ^r 
 
 o 
 
 ' CO ' 
 C CO O * 
 
 10 ^o i cc 
 
 I- 
 
 C^ 
 
 
 
 
 
 Substances.. 
 
 ^/V-N 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 * ** - - 
 
 2 -1 111; :i 
 
 1- . l*-ie&2 
 
 8 r- s -a 5-g 2 ' -1 S 
 o * H t i:- c 
 
 g 3 w^^'5 8:3 
 
 i 
 
 c 
 Pw 
 
 4-oxalate, 
 biphosphate, 
 racemate, 
 
 biracemate, . 
 sulphate, 
 
 : 
 
 C 
 C3 
 
 1 g 
 
 rt 
 j; 
 
 --. 
 "s " 
 
 CO 
 
 !S 
 
 tl, 
 
 IS 
 
 soda-tartrate, 
 
 bitartrate, 
 Potasses, liquor, L. Ph., 
 Potassium, chloride cryste 
 arihyc 
 
 Authority. 
 
 ill ml iiiii 
 
 ca33:acQa:c2E- | G^E- | d 
 
 Stromeyer. 
 Thomson. 
 Berzelius. 
 
 Breithaupt. 
 Karsten. 
 
 Ginelin. 
 
 
 >, 
 
 O) 
 
 1" 
 1 
 
 *_ 
 
 o 
 
 3 ., .. 
 
 >^ - _ *. 
 
 *-^ 8^.^ _-^ 
 
 ^S~ _g -p2fi 
 
 |S S? S^ 
 
 S Pu ^ Ct. P X H 03 
 
 _OJ _OJ 
 3 "3 
 O O 
 -> i-s 
 
 g -g 
 
 f 3 * 
 
 : H^t 
 
 ^^ jS 
 
 QCuUPQPu 
 
 b 
 
 C3 
 >, 
 
 '3 
 1 
 
 
 
 
 w 
 
 
 
 
 
 g 
 
 - 
 
 . 
 
 
 o 
 
 en 
 
 0^ 
 
 en 
 
 CO 
 
 oo 
 
 
 g 
 
 
 
 o 
 ocsj.VjC^o-jdoocooQoot^c^ 
 
 J-- ^ 00 
 
 
 
 
 co en 
 
 o b 
 Co Co 
 
 01 
 
 c") 
 ^} 
 
 * GO 
 N <N 
 
 O <~D 
 
 0^ Tf 
 
 ^ (N w 
 
 o o 
 
 CO (N 
 
 ^co 
 
 S 
 
 : 
 
 O O * >C OC OO CN> 
 ^2 O O O O O CO 
 
 ^,-,l~000<N^<N0 
 
 w 
 
 ^~wc* 
 
 ^^ 
 
 Substances. 
 
 ~^ 
 
 .. 
 
 S 
 
 
 
 
 
 
 
 >> 
 
 0) 
 
 - > 
 
 
 cJlS c" 
 
 
 
 
 i"i 
 
 c 
 
 c 
 
 QJ 
 
 ' >> 
 
 "3 j= ^ 
 
 1 
 O 
 
 PH 
 
 Potassa-fusa, 
 Potassa, carbonate, an 
 
 
 sal 
 so 
 bicarbonate, 
 
 chlorate, . 
 
 -ja 3 -O'- 
 er w e" c - o ^ 2 
 
 - -I 92 Wo^S'S 
 
 SS| 2'^^^^S 
 
 J .'f c 
 
 03.S. C -= 
 
 rt e a.r 
 j= ^r e to 
 
 _r 
 ee 
 
 pL,a,Pn PmX, Pu, PL, PM 0, PH CH Pu, PL, 
 
 
 
 PMpL, 
 
 o o 
 
 PuP-, 
 
TABLE OF SPECIFIC GRAVITIES. 181 
 
 Authority. 
 
 bb 
 
 <D 
 & 
 
 W . w S C . 
 jj. 3 . W CB O ^ ' C 
 
 >' """ ^ # ^ ^ > 
 2 o "o .cs-Ct-j-s-Cgj'ca 
 
 1 c 
 
 111 C V Ic Vc*|lc 1 
 
 h 
 
 
 3 
 
 isity at 60 
 
 sr o 
 
 oS S2 
 
 ' o S3 
 
 rt p "" 
 o " """ " ""* 
 
 C" ** O O 
 
 . *^;-^.** - as 
 
 OO Oi^OOOQiTiO^. C^t > -O--^COQOOOC^ f -O'Tf l OO^ 
 
 J 
 
 ^^^(^QCJic^i^-cbi^cst^c^o 
 
 ti _, 00 ODOOOOOO fNOCNOO^ iO"OO 
 
 
 eoc4ctoovomooHC4C4 
 
 
 
 
 
 
 
 
 
 ;c 
 
 
 o 
 o 
 
 ' ','*'t' 
 ' 1 1 
 
 to o 
 
 J: -S 
 
 'S ' ; g i E ' e j. -g 
 
 B 
 
 ^3 
 
 a 
 
 
 OOOO O O s < - 
 
 "-r c c w S) cj~^ *- 
 
 !-.- ill 23 l| : Hllo|iHl 
 
 Authority. 
 
 g> 
 
 
 
 c 
 n . c 
 c .i: c >, r* c 
 S iS S -2rr-S c 
 
 E? -d 
 
 .'^ . *.^2 
 c < J2 m # c c-a: . c . c .; n 
 
 S j^lS risg^8Sii|8sB8 
 
 g. >,o; <u .E* -o 2 2 = <u o =- c 2 S c >, 
 
 S- r|S:6S5{)'3eJS'gSo,Ha 3 
 
 -G >i: :5 (uca>;.2.-;:3.= '-o ._c5-c^cc-Gt." 
 
 H oScc^E^cQ^acnH^O w^w^E-o 
 
 fe 
 
 1 
 
 3 
 >, 
 
 1 
 n 
 
 a . o"o 
 10 ^ "* " w 
 
 S S ^'S?99r??? 
 
 o 
 
 -co o ^ -OTT -o .I^.o.to 
 oo o -i cocn^oo^OTj* 
 
 C5rj< COOOOOMt^^OO^ 
 ' (N? 1 * V O . <^> ^ '^-*C71 ^ ^ 
 O^ O O OO O O 4*< ** O O 
 *"O '*- ** o *" "^ 
 
 t^- CO C^ ^ I C^ O ^^ CO OO"^CO^CsiQO t^* O O O t* i^ 
 
 
 -i WC^WCOCOCv} CstW 
 
 CO(NC*CN r*<Tt<-*0 (MCOCC. OQ-.j.^TfOOt-COCO 
 
 
 ~~? 
 
 
 
 rf 
 
 
 
 -H J^ 
 
 
 
 a o 
 w w 
 
 
 s 
 
 
 ^ ."2 S 
 
 S E- . - -5 
 
 O 
 
 1 
 
 i 
 
 ^ o ^o^ = f 
 
 o 5 .2 w-g . 
 
 B 2 
 
 3 WC 
 
 'S o 2 - 
 
 W ^ en ^ 
 
 a '. *' 
 o o o 
 
 a s c . oT (jT . .t; 
 J . . ^H 1 g| 2i| 2 " |. 
 
 PI lli'i sSSIfilM?**.' 
 
 X *3 fl a 0.30 c-NoCrtssoo- o c - 
 
 C3C30)O<U~ Cws<:iOt.>-fc.i. L. i. - 
 2ti fc.MW 3333>,>>>^>,>, >, >, 
 
182 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 Authority. 
 
 * d *_ 
 
 Stromeyer. 
 Cresy.* 
 
 Thomson. 
 Vernon. 
 Karsten. 
 Macaire Princep. 
 
 Moselev.* 
 
 1 I 
 
 Q ^ 
 
 'O t_ c* ^ rJ ' ^ r-* C 
 
 c c .<a^ c *. c c ^^ c -! 
 
 # "3c3 -Ov-.tJ33O -C* S ^ 3 O"3>>a> 
 
 Density at 60 F. 
 
 1 
 o 
 
 0) 
 
 -i 
 
 GO to 
 
 5 < 
 
 o *- 
 do in ~ 
 
 
 if ' ' 
 
 "9* T O O 00 
 
 i"" r- .u co eo oo o? o 
 
 <^> -9 " ' ' -4(.4< > 
 o^2 o ^r ^oo<^ 
 o t> *^ t~-in~'*~'o 
 
 CnO OC<)CMCOTf<OOOC'C<OCT5Tt<O^-.MO <J ^O^OW 4 -'OOO 
 
 CO CO C<J CO 
 
 (N - CO 
 
 CO^C^O.-COCOCOCOCQ^CNCNM^^^^^^M^O* 
 
 Substances. 
 
 
 
 
 Sapphire, . 
 Oriental, 
 
 cT 
 co 
 
 
 
 3 
 
 ."o . . g . 
 
 ^ Ji 1 
 
 M 
 
 
 .! 11 i ,. 
 
 PQ Q j- 
 
 (D 
 
 *- "-H Cj) ^ Q> V- ^ 
 
 _C X 
 
 -c o "c 
 
 IJI 
 
 : |||| 
 
 62 2 S . -S .E S| 
 ^'M -^'-5 ef.H- .= .2 c , &0 
 J^a)^~o^-^G c--c- i) o T 
 J"o oo o^ ^^ * ^- & 13-3 
 oooo oaja) a> ^r_a 
 coco coco mm mm m mm 
 
 Authority 
 
 ll.l 
 
 11 
 
 JC 
 
 O 
 
 1 . 
 
 2 S g - - 
 
 ^ 03 >_ 
 
 B 
 
 O f-G 
 CB * i i ^ * * 
 
 1 -='^- g*>, il|a .2 g 
 
 cc*. o 3 13 * . c C J^ P b 9 w tn 
 
 l!MI! : IISllj : l!ifliij 
 
 IN 
 
 rt 
 > 
 
 a 
 
 1 
 
 
 
 
 
 CO 00 
 
 
 
 
 GO *Ti O O CO 
 
 "P fr* ^-( ^1 *p 
 
 CO 
 
 p o '-c 
 
 fill 
 
 ?G|oS 
 
 " S 22 o- 
 
 cr> ^"^ r-ico-HQO *" -^ 
 
 w ^-" 
 
 1 O CO CO ^ 
 
 
 Substances. 
 
 
 
 
 
 Resins, tacamahac, 
 Rhodalite, . 
 Rhodochrome, . 
 
 
 
 
 'o > 
 
 "5-S <u 
 'o o o 
 
 55 
 
 Rochelle-salt, 
 Rosemarine, 
 Ruby, Brazilian 
 ballas, . 
 Oriental, 
 
 * 2 
 
 ^S ...cs .O.N .0 
 
 a 3 - 'E o>" rt c r*' i : S 
 
 .5 "OG W C3 <U - 05-C 
 
 2- 'viiTii ^5.-=.i 
 
 ,a) ? " S S ,E. 1^ W - 5-^ 
 
 g~^r^OMnJbc* oooo>^n3 i- 
 
 cicc! ciKcococo mmmmm m mm 
 
TABLE OF SPECIFIC GRAVITIES. 
 
 183 
 
 
 
 s 
 
 .2 ^ 2 
 
 
 
 3 
 
 3 3 : s : 
 
 
 
 O 
 
 o o o 
 
 b 
 
 * 
 
 "W 
 
 a -o t3 
 
 
 
 " - *>> * ' 
 
 C 
 
 C u ^ C C 
 
 i 
 
 ^* " C * ^0) 
 
 .b. 
 
 c o.S: W)*- c M.ir E ^ o tj 
 
 
 ' ^"5 3^ * 5 ~ ~H ~c o > 
 
 -2 ^ 
 
 -^2.S-a^ 2-^S ^ a." "3^ 5*S 
 
 
 2i E M S^-GcsSfSlaS 
 
 O O c/2 Q tD E 1 1^ 3 it< Q C5 
 
 a] 
 
 ailll ill Illll' ll 
 
 h 
 
 
 
 ' o ' ' 
 
 o 
 
 
 
 
 
 
 5o ioS Tf 
 
 j> 
 
 . . .&i ,g . . -::.> * 
 
 a 
 
 co co 4* co 
 
 
 
 
 o 
 
 3 
 
 ^ .j o 
 
 1 
 
 co o o ** o -H 'tc-omoooc 
 
 T^ O QO O Tj< l^^C^OOCQOO 
 
 > O 
 
 SB 5 i 1 ES 2 ? 1 i f 
 
 
 
 
 
 
 
 
 - 
 
 
 OD* 
 
 
 
 
 I 
 
 
 v ^ 
 
 J 
 
 
 
 s"5L 
 
 o 
 
 = ~ w '^ ' 
 
 
 
 
 'w> s -1 S 
 
 CD ., O ' 
 
 ^ 
 
 - ~ -r _ ^ - o. o 
 
 g 3 5 ^ 
 
 
 
 2 Q) 
 
 . n = cs 2 <u 
 
 s 
 72 
 
 ,'" ^ -5 S c "S r ~ = 
 
 ~'Hc""o2c )c:: - a " a:: c 
 ]_T3 5 o.g .ca o = >> o u 
 
 arsenia 
 biborat 
 
 - - - S" i|s ".^ 
 " " |" - | g-Js js|: 
 
 
 ""S " fcn ^ a, O. csT 
 
 
 
 
 SEEE^JS 1 
 
 
 
 c c c 
 
 o o o 
 
 en d tfl w 
 
 E S E 
 
 o > o o 
 
 _. ^QJ.co !. 5 
 fe^ OH 03 i3~~ 
 
 0*5. ^ 
 
 I r- >^ ^ * ^ "~" 
 .~ C3 S = 
 
 CO 
 
 r-l CTS 
 
 + -O ' O 
 
 OO CO *"COOOOCO'^J>-OOOI^C^'- H ^OOOOCO 
 
 ^p^5 ^^t^j^^^^ip^O O-^--C^OcpCOO^O5COOpCOip^(Bipio' < 
 
 5 ih 4f 10 r^ >o i"-- j> i^- co 4j< r~ oo >o ih >o ts i"-- o 60 >o ih co co co 
 
 ^ c o 
 
 (.0 00 g^ 
 >O O iO 
 N 0^,^^ 
 
 CO CO CO CO CO CO O 
 
 o 2 -S 
 E s '= 
 
 3 cT S 
 
 - 
 
 _ s.sts . - C- 
 
 bi : : : o_. 
 
 Q ^ O ~ CS 
 
 5 S'o'G.S 
 
 -a ^- 
 
 If* 
 
 c x a 
 
184 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 k, 
 
 "B 
 
 o 
 
 ^3 
 3 
 ^ 
 
 # 
 ._! * 
 
 V: - = 11 j| 
 
 N 
 
 '3 
 
 s 1 
 
 = -" S. co * 
 
 : sslosis Is 1 1 |iS J2l'l:'^ sil 
 
 
 JEEHS 
 
 OCQ^JHGQ E^H cocoNQQE-HKNJ &.E-QS 
 
 h 
 
 
 
 
 
 fe . 
 
 J2 CO 
 
 T* 4 "* "* 3 co ^ 
 
 a 
 X 
 
 
 
 2o " JoC^ |1 ^o 
 
 3 
 
 <u 
 
 ?2Sc{53^C:S25I 
 
 SoooSooY^SSSSoSc33SSooSoo-So 
 
 o 
 
 oooocococo 
 
 O^M^r^OOCOO- li-^J-t-CNOM^^^^^^-W^WOJ 
 
 
 en 
 
 
 
 C3 
 
 J3 
 
 " 
 
 
 
 
 j 
 
 ,!.... 
 
 . 'g t 3 . 
 
 
 S 
 i 
 
 
 0) <U 
 
 J 
 
 
 f "S jg ' . |^ 
 
 (W 
 
 1 1 1" : 
 
 - "H" ^ '"'c- " j"o 
 w o" .'5 -^"T 5 -"":5 c"o o bfl " 
 
 I s 111 3 lli-^r^yiilTlh s l- : : 
 
 ca C3C3C3 tucu!u4J^^a>aio<ucu rti ~* 
 
 
 co* en co* 
 
 CO COCOCO COCOCOCO COCOCOCOCOCO CO CO 
 
 Authority. 
 
 o> _ 
 
 "p "a 
 o o 
 i-i -j 
 
 c . c 
 
 c * c a 
 
 ^iZ-OQME-'Qi- 
 
 o 
 "3 - 
 
 o 
 I-J 
 
 * n' 
 
 , i i ill ^ g . g . is- ! a I s 
 
 hL B C B .?* 7;;Q.Omjno^ S <u - - "5 ^S^- >: 
 b o c O >- be CL.S S -*B 5 . O I " -S 3013" a 
 sTijro^.JH c ca o ca C J3 O ai^G_a >~ 
 ^^-t^LnJr^ fD ^ ^ Lin t2s <! P!H E" 1 ^ M 03 E- H O 
 
 fc 
 
 
 
 1 
 
 
 "^^^ o <J= T "P ^oj 
 
 
 >-, 
 
 i 
 
 
 
 IlSllllr- 
 
 'Of. CO n '(MCO COy; 
 
 0-oon2 -ooo ^ 22 oo o 
 
 p 
 
 <NC*~^-~-<N 
 
 CQ^M^CNCvJCNW^MM^^CONCNCOWOWCO^MCOCO O 
 
 
 
 _ 
 
 
 
 2 
 
 
 
 3 , g 
 
 y 
 
 -O W 
 
 
 Substanc( 
 
 1 S 8 
 
 3 
 O.^ 
 
 J-- 5 "f I" 
 
 i 2 
 
 eo" 
 
 ' ' . j ' . ^ ^ ' ' ' . ' --tj 
 
 f i ; ll : : : : : : iff ; ~*j -I 'illj 
 
 12* ' 2 "ll||gl^ ^ 
 
 
 1 
 
 co co co w " co"co"^co co co 
 
TABLE OF SPECIFIC GRAVITIES. 185 
 
 c 
 
 S^^?a-:5:-^cu:- c2M~ 
 
 o c 
 ~ c 
 
 s 
 
 a . .c . c 
 
 T} e 'e o ^"* e e > o t* e >> O 
 
 & 
 
 TJ ', 
 
 oo Q >n o o 
 
 
 S c 
 
 COCO COCOCOCOCO 
 
 2r : :::::::- II , S>S 8 & 
 
 . 
 
 i-Erii nifi! 
 
 Or^bjc-H r* cd^-^HDi^^oi E- Suciu E- S>HtfH 
 
 o S S 
 
 - e - .g ..... 
 
 2 .1 
 
 C ' CO 
 
 si ' I 
 
 -5 - . -be*: 2 -^ 
 _o ^ -" $ S.E-^c 
 
 a "^ ^ 2 v2 c" ji"^ .5 ilp. Ji'O-'c'^'^S & 2^6 "S~ "-^ ^"^ 
 
 1 I 3^ C^"" 1 C3CJ"CJO O OP OO^W hJ^jSj^Q^ G-CL, 
 o 
 c v 
 
 C 
 
 rzz o -. - - ^ ^ w '^''*** **' 
 coco " 
 
186 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 Authority. 
 
 c c . 
 
 O >> 0> 
 
 *. * a 1 
 
 ^ c c 
 ..-2 ^ *. .. 'S * 
 
 CQ 2 H 23 O O r ' Di E" 1 ^ CQ ttJ CfiJ h-3 Q 
 
 bp 
 
 La 
 
 .2 
 *q 
 
 * "O * 
 
 c ra C w s i c 
 
 VljS|g-sg 
 
 5 : 1*073 o 1 J 1 
 O H ^ H 03 r- 1 02 H 
 
 fe 
 
 
 
 
 1 
 
 S 
 _^ 
 
 1 
 
 00 -H 
 <N t- 
 
 So^go 
 
 o o o /- 
 
 *- ** " co 
 
 O^COjOCTiOOOfMCOO 2Ot^>00>OOOT^ 
 
 * S 
 
 . . .^ . 
 
 -LeSLo g 
 
 
 (NCNWOrft- 
 
 CM ^ 5 rj- 
 
 <M M cn-^ co 
 
 
 
 
 
 
 
 I'M 
 
 . J> 
 
 
 
 
 "^ -g^- 
 
 u 2 ^ 
 
 
 
 
 0) 
 
 
 t O 01 . 
 
 o M ^o . 2 
 
 SQ ... 
 
 Substanc 
 
 "O 
 
 a "'5 
 
 3 ~=~ 
 
 o_H - c c 
 < s * cs __co 
 
 -- S^^ ^-| 
 
 1 . . slfcS* 28 * . Ill 
 
 SPof cT Sgcg- S^"- 
 .2 2 ^o .a c"o g 
 
 11 |-| 1 |'|l 
 
 _Q O 
 00- 
 
 >_ >- n 
 -o-o o 
 
 ^^ o .2 
 
 g^ -*S % . 
 
 ?ifiii.il 
 
 ai.2ooo = 3 
 __<u^:-Gj=j3^:-CJ3 
 
 Authority. 
 
 03 
 
 3 
 o 
 
 Is 
 
 2 S 
 1 1 
 
 3 
 S JJ -o^tr' ^ .- ^ 1 
 .^cj !,; 5 o I ^VIS S 
 
 O^CQ^tiCD^SjSQ Sc3^r"tCfflO^ 
 
 * * r* 
 
 a s^ Js" *>,"1)1 E> 3* 
 
 h 
 
 
 
 o 
 
 
 Density at 60 
 
 CTi 
 
 CO 
 
 <T> iO CJ ^ 
 
 en ooo Sj 
 
 rt^ o - 
 
 ^ 2 lcr^^^^^^oo^-oaoSoS 
 
 in *c 
 
 <!o co 
 
 '. T* T*" . ". T" . . _1_ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 * 
 
 <-T <*-" 
 
 . 
 
 "o " S ^ 
 
 c 
 
 Substanc 
 
 1" 
 
 1 ' &' 
 
 i. - 1- g 
 
 fcb 2 
 
 C3 
 
 M * 4 
 
 .... . .il:l.||^i. 
 
 : i; :::: 'll I'] *SlS' 
 
 3 3 
 
 _= J3 
 a. a. 
 
 ,~ 3 
 
 - P 
 
 l^- ' ! 
 S* . . ; * 
 
 5 4> I 
 
 1 -5-S2" -f| 
 j== g g'S- o 5" 
 
 D 03 J- 05 " C C 
 
 
 02 
 
 O2 CO 
 
 j^ W2 & Oi CO CO 
 
TABLE OF SPECIFIC GRAVITIES. 
 
 187 
 
 ^ 
 
 c 2^ 
 
 IE"? 
 
 J= 0) O 
 
 E-Eci 
 
 a C 
 
 . cs u 
 
 II" 
 
 x J 
 
 1*8 
 
 o-- 
 
 il 
 
 w E 
 
 V ccT^l&g,, I 3 .-. ,.| 
 
 4l:IfcjMlS.f j ..jg-S g-g 
 
 &V=Crf B E S.S w 3 0<3<C .2 
 
 B K/ 0> C3 ~ O fc. -- .O^;j3-C.-u 
 
 W^Q^M ^pOSSU~E-tfWPH 
 
 cr 3 > c 
 o o 2 S 
 
 QJ fc- >-. 
 
 coOnOco 
 
 3 
 
 S3 .2 
 
 3 y 
 
 _r i. y 
 
 00 J 
 
 ^^ 
 
 o> ca 
 > 
 
 le 
 
 II 
 
 o 
 
 go 
 
 a sss 
 
 * 
 
 s 
 
 to 
 
 o t c " o ,1. ,!_, O 
 
 c g 
 
 *- 
 
 (N " 
 
 
 
 
 
 o 
 
 go 2 2 
 
 
 s 
 
 n 
 
 ^ O Oi 
 ir: ^ <* i^* C} co O co O 
 
 oo " '- coor^ooo 2o*" 
 
 CN i t C^ C^ i ^-i rr G"i CO OOOO OOO 
 
 S CT> -< O 
 
 oo o m *- 
 
 i CO CO 
 
 9999 
 
 
 ^^,^^,00^0 0*<N 
 
 v^V-^ 
 
 
 
 
 
 
 
 
 
 
 o"o 15 
 
 J3 
 
 rt 
 >g( Pi 
 
 O C-' 
 
 a^" ^^WEJ 
 
 li^sii 
 
 Ills 111 
 
 s ,op 
 
 COC^OfNOCO^O ^J^- 
 O CO VO 
 
 CO rr 
 
 o o 
 
 00 00 
 
 ^-( rll CO 'i <b -O 
 
 *- - vo 
 
 ? oo cr> to o ' oo 01 -H i ys 2 ** &> * 
 
 CO^CCc<r>Tl<iCfMC-)OOCx>>.-. ClrfCO'O *-" t^ * 
 
 G}<OCOCNOO-I~OO 
 
 a,oo^^oc,ooo^o^oliHI 
 
 lOtNOCOCO^CO-^COCOCOCOC^CO^HC^CO-^-i-T}" 
 
 I ^1 
 
 G 'C X v. 
 
 2" ^ S" 
 
 s -gg. 
 
 <y 
 
 2 RS 
 
 O. O. w 
 
 s 
 
 if 
 
 - - , , r 
 
188 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 .* c C w . B 
 
 >,* . O >> ~ >. 3 >.-O>> 
 
 O 
 
 S^, 
 
 -2 
 
 "oj * 
 
 O J <. o SJ - - 
 
 Sp " SP " 
 
 - 
 
 00 4 ~ CO ?- <- ft 
 
 o 
 
 a SI 
 
 2S-2- 5.r 5 ^ o *-s 
 
 C-=JS o = *^^^ 
 -- -^E 20 ^ 23 
 
 2 IS 
 
 ' i* 
 
 O O 
 
 ^- - x-. 
 
 "jj 
 
 # <jl3 
 b 
 
 K : l|ilsllJl- 
 
OF SPECIFIC GRAVITIES. 189 
 
 fe> 
 
 c 
 o ^ 
 
 
 1 
 
 JS c . ^ = * c . c ,-j, 
 
 *.c *d 
 
 g 
 
 
 Or- 
 
 3 
 < 
 
 B i^fJ'-PlsL lll*i~_D 
 
 ? !*>.! |. 
 
 
 E" 1 -c E j 2 o gji'jjjij ^ 
 
 IS o jr j= 
 
 
 ^ r~ l Ov5Od---' i^l r^ tE O ~" * P i M r i 
 
 <^g^,Qf_^22 
 
 
 r~ ~^ 
 
 
 fc 
 
 
 
 & 
 
 J-J 10 
 
 
 
 
 OJ ^ 
 
 *^ 
 
 s 
 
 C0_ o ' 
 
 QO -tO 
 
 >, 
 
 O co O 
 
 co o co 
 
 2 
 
 <L 
 
 
 OTO^P-.O, - o 
 
 to j^ b o o 01 c* 
 
 q 
 
 OOOOOOOOOOOCOCOCOO^^COOOOOOOO^ 
 
 CO CN CO 1-1 *<* CO CO 
 
 
 
 
 
 
 
 
 c oT 
 g^s" ^ S 
 
 
 <5 
 
 fe ^ 5 jr o ^ "a. ^-a" 
 2??-^ ' . 1 V jf !i 
 
 c 
 u 
 
 5 
 
 <S'&^,f|jJ .S ^ - 8j ^'S 
 
 
 In 
 
 
 o 
 
 i 
 
 O' = " l"llD(|S^ i - -% ' 
 
 ^ 'to 
 
 
 \ tiT ^ c ^. c3 
 
 H C2 2 
 
 " - "if B -s. 
 
 - I O 0) 
 
 1 r- E.H S K' cc S H E- 1 E- , A.. 
 
 .j= S . 
 
 02 3 
 '5*3 C O" 
 
 . S 
 
 .o 
 
 S o 
 
 . . . 
 
 lrl I IE ii r .'. 
 
 * S co to - <n 
 
 - - * cs-o-o-a 
 
190 
 
 TABLE OF SPECIFIC GRAVITIES. 
 
 . c o 
 co co 
 <rj -^ 
 
 ' <T5 M 
 O O 
 
 4> >p oo "sp f~- o <*c <^ ro co co > 
 
 i 
 
 ! 
 B 
 
 I oT 
 ^ 
 
 ,- a . 
 
 " S * ^ * - 
 
 <'e c^ ' QJ 
 
 o"S fi2'2 2 3 jj'-.S: 5 
 
 N cs: cs: 
 
 JS 
 
 i 
 
 
 
 
 I ' 
 
 5 
 < 
 
 fc 
 
 o o _. 
 
 . co (N O >r 
 Q 
 
 o 
 
 1 ' '-J 
 5 ' ' - ? 4 ' I" 
 
 ( s . s ! L s 
 
 2 
 
 5^ : - : : - - ^- - ^ 73 - 
 
 i2 O a ra 2 
 
 cT 
 
 B V . k 
 
TABLE OF SPECIFIC GRAVITIES. 191 
 
 CHEMICAL TABLES, 
 
 NOTES on the TABLE of DENSITIES. 
 
 ACETIC ACID. Specific gravity is not a certain criterion of the (Strength of 
 acetic acid, when the latter contains more than about 34 per cent, of water. 
 Mollerat. 
 
 The acetometer of the 1 Messrs. Taylor has for its basis the strength of 
 proof acid (Pr. v.), called by the manufacturer No. 24. 
 
 Table, by the Messrs. Taylor, showing the proportion of real acid per cent, 
 at different densities : 
 Pr. V. 1-0085, 5<> ; 1'017, 10 ; 1-0257, 15g ; 1-032, 20 j ; 1-047, 30g ; 1-058, 40g. 
 
 When acetic acid is converted into acetate of lime, the decimal fraction of 
 the density is very near doubled ; thus, 1 009 in pure acetic acid becomes 
 T018 in acetate of lime. (See Viriegar.) 
 
 AETHER. Table, showing the specific gravity of mixtures of alcohol and ether ; 
 
 by Dalton. Pure ether, 0'72(?) ; 90+10, 732 ; 80+20, 0:744 ; 70+30, 0'756 ; 
 
 60+40, 0-768; 50+50, 0'780 ; 40+60, 0'792 ; 30+70, 0'804 ; 20+80, 0-816; 
 
 1G+RO, 0-826 ; 0+100, 83 (Spirit). 
 
 ALCOHOL. For tables of the density of various mixtures of alcohol and water, 
 
 see " Brande's Manual," " Ure's Dictionary," and other works. 
 ALLOYS. Alloys which possess a density greater than the mean of their consti- 
 tuents: 
 
 Gold with antimony, bismuth, cobalt, tin, or zinc; silver with antimony, 
 bismuth, lead, tin, or zinc ; lead with antimony ; platinum with molybdenum j 
 palladium with bismuth; copper with bismuth, palladium, tin, or zinc. 
 Alloys which possess a density less than the mean of their constituents : 
 Gold with copper, iron, lead, iridium, nickel, or silver; silver wiih copper 
 or lead; iron with antimony, bismuih, or lead; tin and antimony, lead, or 
 palladium, nickel, and arsenic ; zinc and antimony. Thtnard. 
 AMMONIA. See " Tables," by Ure, Dalton, Davy, &c. 
 
 " Ure's Table," is generally considered to be the most correct. 
 BARLEY. If not more than five "pickles" (or grains) per hundred float, when 
 unmalted barley is thrown into water, it is considered by tradesmen to be a 
 good sample of grain; if more, the contrary. After malting, the grain be- 
 comes specifically lighter, and when thrown into water, will float in a longi- 
 tudinal position ; in good malt, only about five pickles per hundred will sink ; 
 grain that has been partially malted will remain perpendicularly suspended 
 in the water. 
 
 BEER. The rule employed by Mr. Warington for converting the saccharometric 
 indication (by Richardson's instrument) of the wort into real specific gravity, 
 is as follows: Divide the saccharometer indication by 360, and then add one. 
 Example 
 
 36-4-360+1 "CO =1-1 sp.gr. 
 
 Richardson's saccharometer indicates by how many pounds a barrel of wort 
 of a certain density is heavier than a barrel of pure water (viz., 360 Ibs.) To 
 convert saccharometric indication into real gravity, add the number indicated 
 (say x) to 360, and make the following simple calculation : 
 
 360 : 360+a: : : ] I : true density. 
 
 The scale of Dicas's instrument is nearly as 5 to 2 of Richardson's ; i. e. 
 80 by the latter are about equal to 200 by the former. 
 
 Allan's saccharometer indicates the true specific gravity. 
 
 BLOOD. The density of the blood, and of the serum of the blood, is increased 
 in plethora, cholera, &c., and diminished during pregnancy, and in pneumo- 
 nia, bronchitis, pleuritis, tubercular phthisis, fever (?), and chlorosis. 
 THE EARTH. The density of the earth is supposed to increase in an arithme- 
 tical progression at the rate of about '38 for every 100 miles, as we penetrate 
 through the exterior crust towards the centre. 
 
102 TABLE OF SPECIFIC GRAVITIES. 
 
 GAS. A diffusion experiment affords the elements for calculating the specific gra- 
 vity of a gas. 
 
 , A x a 
 The specific gravity = ( ~~ j 
 
 Where G is the measure of gas submitted to diffusion, and A the measure of 
 return air. Edinb. Phil. Trans. XII, 222. 
 
 One hundred cubic inches of dry air, at 29'92 inches Bar., weigh 32'5SS64 
 grs. at 32 F., and 30-82926 grs. at 60 Y.Eegnaull. 
 
 GLASS. The density of annealed glass is greater than that of the unannealed. 
 The phenomena of devitrification are always accompanied by an increase in 
 density; thus, soda glass being =2-485, the devitrified glass is=2'503. 
 Spliltgerber. 
 
 HYDROCHLORIC ACID. Sue tables by Davy, Thomson, Ure, Kirwan, and 
 Dalton. Ure's results are considered the most accurate. 
 
 HYDROCYANIC ACID. 0'957, 16 ; 0'9?68, 10'6g; 0'9815, 9'lg; 0'9S4, 8g ; 
 0-987, 7'3; 0'989, 6'4o ; 0'99, 5'8 ; 0'9923, 5'0 ; 0'994, 4g ; 0-9958, 3 ; 
 0-9974, 2 ; 0'9979, 1'6. Dr. Ure. 
 
 MAGNESIA (SULPHATE OF). For a table, by Anthon, see Gmelin's Hand- 
 book (English trans.) 
 
 NITRIC ACID. Tables by Ure, Thomson, Kirwan, and Dalton, are contained 
 in most of the manuals. Ure's table appears to 'be the most correct. 
 
 OILS (FIXED). The zero of the scale in the so-called Elaeometer is placed 
 where the instrument would float in pure oil of poppy seeds; the space be- 
 tween this point and that which marks the density of pure olive oil is gene- 
 rally divided into 50 degrees. The density of pure almond oil is about equal 
 to 38 or 38i degrees by this scale. The Oleometer of M. Laurot is so gradu- 
 ated as to sink to zero in pure colza oil (heated to 212 F.) ; to 210 in rape- 
 seed oil ; to 124 in poppy oil ; to 83 in fish oil ; and to 136 in oil of hemp- 
 seed. 
 
 PHOSPHORIC ACID. Sp. gr. 1-85, 50<> anhyd. acid : 1-6, 40g ; 1-39, 30. g ; 1'23, 
 200 ; 1-1, lOg. Dalton. 
 
 POTASH. For tables showing the proportion of caustic potash, and hydrate of 
 potash, contained in lyes of different strength, see the works of Ure, Brande, 
 Gmelin, &,c. Ure's table appears to be the most accurate. 
 
 POTASH (CARBONATE OF). For table, by Tiinnermann, see works of 
 Brande, Gmelin, &c 
 
 POTASH (CHROMATE OF). S.G. 1-28, 50g ; 1'21, 338 ; M8, 250 ; M5, 20|> . 
 1-12, 160.; Ml, 140.; 1-1, 12". Dr. Ure. 
 
 PYROXYLIC SPIRIT For table, see Ure's Dictionary of Arts, &c. 
 
 ROOT-CROPS. The relative densities of different roots or tubers, are'stated by 
 
 Mr. Hyett, to be as follows: 
 Turnips : Pomeranian globe, 889 ; Green round, 905 ; Border imperial, 932 ; 
 
 average, 908-57. 
 Swedes: Purple -topped, 949; Green-topped, 952; Skirving's, 972; 
 
 average, 957 67. 
 Mangold-wurzel : Long-red, 995 - 25 ; Red-globe, 1005'7; Yellow-globe, 
 
 1014-6; average, 1005-18. 
 Potatoes. Rohan, 1081 to 1089'95 ; Purples, 1091 to 1102; Welsh-kidney, 
 
 1 107 to 1 108 ; average, 1096'49. 
 
 The specific gravity of small roots appears generally to exceed that of large 
 roots. Mr. Hyett says, " That the determination of the densities of root- 
 crops, affords an easy though rough method of estimating their relative 
 powers of nourishment. "(?) 
 
 SODA. For tables, by Richter and Tiinnermann, of the proportion of hydrate of 
 soda and anhydrous soda, contained in lyes of different densities, see the 
 works of Gmelin, Brande, Ure, &c. 
 
 The following table is by Dalton, and shows the percentage of NaO. 
 
 Sp. G. 1-85, 63-60; l-72,53'8g; 1'63, 46'6-g ; 1 -56,41-20; 1'5, 36'8Q ; T47, 
 340; 1-44,310; 1-40, 29o ; . 1-36, 2 6g ; 1'32, 23 {f ; 1'29, 19g ; 1'23, 160; M8, 
 13 ; 1-12, 90.; 1-06,4-70. 
 
 SODA (CARBONATE OF). For table, see Gmelin's Handbook. 
 SODA (NITRATE OF). See Richter's tables ; Stoichiometrie 3'164. 
 SODA (SULPHATE OF). See Brandes and Gruner, Br. Arch. 22-148. 
 

 TABLE OP SPECIFIC GRAVITIES. 193 
 
 SODIUM (CHLORIDE OF). The proportions of salt in solutions of different 
 
 densities, at 62 F M is shown below. 
 S.G. 1-0283, l-24th; 1'0275, l-25th ; 1'027, l-26th ; 1'0267, l-27th ; 1'025, 
 
 l-28th; 1-0233, l-30th; 1-0185, l-39th; 1'0133, l-44th ; T0105, l-56th ; 
 
 1-004, l-108th; 1'0023, l-162d. 
 
 [Calculated by Mr. Kirwan, from Watson's results.] 
 
 SUGAR. According to Dr. Ure, if the decimal part of the number representing the 
 specific gravity of syrup, be multiplied by 26, the product will denote very 
 nearly the quantity of sugar per gallon in pounds weight, at the given sp. gr. 
 
 Table, by Dr. Ure, showing the percentage of sugar, in saccharine solutions 
 of different densities : 
 Sp. Gr. 1-326, 666660 sugar ; 1-231, 5Qo ; M777, 400 ; M44, 33'333<> ; M34, 
 
 31-25; 1-125, 29-412; Mil 26'316o ; MC45, 25g; 1'0905,> 21'74g ; l'C82, 
 
 20g . 1-0635, 16-6660 ; 1-Q5, 12-5$ ; 1-0395, 10g. 
 For more extensive tables, see the different chemical manuals ; also, Evan's, 
 
 Porter's, and Dutrone's works on the Sugar Manufacture. 
 At 1-342, syrup of the cane contains 70$ of sugar ; at the same density syrup 
 
 of starch sugar contains 75^ per cent. Vre. 
 
 For a table of the densities of alcoholic solutions of sugar, see Ure's Diction- 
 ary of Arts, Manufactures, &c. 
 
 SULPHURIC ACID. For tables, by Parkes, Ure, Bineau, &c., see Ure's Dic- 
 tionary, Grnelin's Handbook, Parnell's Applied Chemistry, and other 
 manuals. 
 Bineau's table is said to be the most correct, but as the results are calculated 
 
 to 32 F., Ure's table is the one most commonly accepted. 
 
 URINE. To determine the proportion of solid matters in urine, multiply the differ- 
 ence between the density of the urine and that of water by 2'58 (Dr. Henry), 
 or by 2'33 (according to Christison),the product shows the quantity of solid 
 matters in 1000 grs. of urine. Thus, giving a urine of T004 sp. gr. : 1004 
 1000=4, which, multiplied by 2'58, gives 10'32 as the weight in grains of 
 solids in 1000 grs. of urine. According to Becquerel, the proportion of sugar 
 in a specimen of diabetic urine may be ascertained by using the factor 1'65 as 
 above. Millon says, that " the second and third figures after the point (in the 
 density) express with tolerable exactness the quantity of urea in 1000 parts of 
 the urine. Thus, urine of T011 contains about 11 parts in 1000 of urea. In 
 the urine of animals and pathological urines, however, M. Millon admits that 
 this correspondence is no longer observed. The density of the urine is gene- 
 rally below the normal standard in Diabetes insipidus(\'QQ3 to 1*005 Percy), 
 hysteria, Bright's disease (?), chlorosis, and jaundice (?); and above, in Dia- 
 betes mellitus (1"032 to 1'048), erysipelas, fever, bronchitis, haemoptysis, and 
 other inflammatory diseases. It is generally higher in the afternoon (1 '023 to 
 1-028) than in the forenoon (1'017 to 1*022), evening (1'019 to 1'028), or night, 
 (1-012 to 1-025.) 
 
 VINEGAR. Vinegar of malt, of a density of 1'014, becomes only 1 '023 when con- 
 verted into acetate of lime ; "005 of its density is due to mucilaginous matter. 
 Ure. 
 
 WATER. The temperature at which pure water attains its greatest density, ao- 
 cording to different observers, is as follows : 
 
 38 F., Dalton; 38'75, Stampfer ; 38'8, Eumford ; 38'804, Munch; 
 39o, Sir C. BlagdenGilpin; 39' 101, Playfair andVowZe; 39'176, Despretz; 
 39-38, Hiillstrom ; 39'5, Hope : 40, Lefebvre Gineau ; 41, Deluc. 
 
 Despretz's determination is generally believed to be the most correct. 
 
 Sea-water (from the Southern Ocean), according to Bladh, attains its 
 maximum density at 36*59 F. 
 
 WOODS. The densities given in the table have reference to the dry and well- 
 seasoned woods, in their natural condition. 
 
 The true specific gravities of these woods (i. e. when the air in the inter- 
 stices of the wood has been expelled) are, according to Count Rumford, as 
 follows : 
 
 Birch, 1-4848; beech, 1-5284; elm, 1'5186; fir, 1-4621; lime, 1'4846; 
 maple, 1-4599; oak, 1-5344; poplar, 1'4854. 
 
 13 
 
194 
 
 MEASURING OF FLUIDS. 
 
 Fig. 101. 
 
 Fig. 102. 
 
 CHAPTER IX. 
 
 MEASURES AND MEASURING. 
 
 Measuring of Fluids. When great accuracy is required in 
 the estimation of fluids, their weight is determined; but in ordi- 
 nary operations, the amount of their volume is obtained by the 
 employment of vessels purposely prepared and graduated with 
 care and precision. 
 
 These vessels, or graduates as they are called, are generally 
 of two forms, those for the larger operations being cylindrical, 
 as shown by Fig. 101. This shape combines both strength and 
 convenience. For the smaller (ounce or drachm) graduates the 
 conical form, Fig. 102, is preferable, as giving greater facility, by 
 its smaller surfaces, for accurately estimating minute volumes. 
 
 Graduation. For the large 
 measures, the imperial pint is 
 the usual integer. To graduate 
 a vessel to this extent, take a 
 glass balloon, counterbalance it, 
 and weigh therein accurately 
 one pint imperial, 34-659 cubic 
 inches (8750 grs.), of distilled 
 water, at the temperature of 
 62 F., and at 30 inches of ba- 
 rometric pressure. After the vessel has remained 
 undisturbed upon a level shelf, sufficiently long 
 for its contents to acquire a smooth steady sur- 
 face, scratch upon the neck the exact line to 
 which the liquid rises. The narrower the neck of the flask the 
 greater the facility in noting this point without liability of error. 
 This weighed quantity of water is then to be transferred to the 
 proof glass, under process, of form as shown in Fig. 101. After 
 the water has settled, and presents a smooth calm surface, its 
 level is to be scratched accurately upon the exterior of the 
 glass, either with a diamond-point or a sharp file. A reli- 
 able pint measure is thus obtained, to graduate which into 
 its subdivisions of ounces and drachms, it is only necessary to 
 
GRADUATION OF VESSELS. 195 
 
 take the weights of these fractions of the pint, and proceed in 
 manner as above directed. So likewise, the vessel can be gra- 
 duated to pint divisions, in number as many as its capacity will 
 admit, by multiplying the weights of water, and adding them 
 to those previously measured, noting the level of each with the 
 diamond. 
 
 The imperial pint is larger than the wine pint of 16 fluid- 
 ounces, in the ratio of 6 to 5, and, therefore, its subdivisions must 
 number 20, and severally of 1-73296 cubic inches capacity. This 
 makes a discrepancy, the inconvenience of which can be remedied 
 by having a second scale upon the same glass, showing their rela- 
 tive values. The only disadvantage is the trouble of a second 
 graduation, which is, however, compensated for in the conveni- 
 ence of the first scale, each division of which, unlike the fluid- 
 ounce of the wine pint, represents a fluid-ounce exactly, weighing 
 one ounce avoirdupois of distilled water=437'5 grains. 
 
 The plan of graduating the pint, itself estimated as above, into 
 its subdivisions by apportioning its height into the requisite num- 
 ber of equal parts, by means of a rule, will only answer for ves- 
 sels of uniform diameter throughout, and which are only intended 
 for the grosser operations of measuring. 
 
 Those graduates, which are intended for nice purposes, should 
 also have a third scale graduated in cubic inches. The cubic 
 inch equals 252-468 grains of distilled water, at temperature and 
 pressure the same as above, and a measure or bottle of this ca- 
 pacity should be prepared and kept ready for use. As there is 
 sufficient room upon the glass for all these scales without the 
 necessity of crowding them together, there should be an equal 
 interval between them. 
 
 To graduate a vessel to the litre of the French standard, sub- 
 stitute 1 kilogramme for the 8750 grains distilled water, and 
 proceed as above, making the subdivisions pro rata. 
 
 The graduates and cubic inch bottles are less to be relied on 
 when purchased than when carefully graduated by the operator 
 himself, and they should never be used in important experiments 
 without having been previously verified. 
 
 For the graduation of the ounce and drachm measures, and, 
 indeed, all vessels of small diameters and capacities, such as 
 tubes and the like, the divisions of which must necessarily for 
 
196 GRADUATION OP VESSELS. 
 
 want of space closely approximate to each other, mercury is much 
 preferable to water. Mercury gives a more level and distindt 
 surface than water, and not being attracted by the sides of the 
 vessel, allows a greater accuracy in making the subdivisions, 
 especially in very narrow tubes. The addition of one grain of 
 lead to every 4000 grains of quicksilver flattens the surface, 
 and greatly facilitates the reading of thfe level ; but it must be 
 otherwise pure and free from dross and film. A cubic inch of pure 
 mercury, according to Faraday, weighs 3425*35 grains, at 62 F. 
 
 There should be a series of these graduated glasses, ranging 
 from a double pint down to a drachm. 
 
 For the tubes and other vessels used in analytic research, the 
 decimal divisions are both convenient and necessary. If a cubic 
 inch is to be divided into tenths and hundredths, the former are 
 graduated by the space occupied in the tube by the one-tenths 
 (342*50 grs.) of a cubical inch of mercury, and each tenth divi- 
 sion coincident with the level of the metal within, is marked upon 
 the scale with the file or writing diamond. So also, in like man- 
 ner, are the hundredths graduated by substituting 34-25 grs. 
 (the hundredth of a cubic inch at 62) for the 342-50 grs. mercury. 
 
 To give a clear idea of the mode of preparing a measure with 
 mercury, let us suppose that a tube is to be graduated to cubic 
 centimetres of the French standard. In the first place, a 
 narrow strip of white paper, with a line ruled down its centre, is 
 to be pasted lengthwise upon the side of the glass to be gradu- 
 ated, the length of the paper of course corresponding with the 
 height of the glass. 13-59 grammes of mercury are next to be 
 accurately weighed out, and this quantity, which represents a 
 cubic centimetre, is to be poured into the tube, held vertically by 
 a support similar to A, in Fig. 115. After the vessel has stood 
 long enough for the liquid to become quiet and assume a smooth 
 surface, its level is noted down, and its corresponding height 
 marked with ink upon the paper slip. The space which this 
 bulk of quicksilver occupies in the tube equals a cubic centimetre, 
 and when accurately noted, may serve as a standard for the gra- 
 duation of vessels of larger capacity ; for these cubic centimetral 
 divisions can be multiplied, merely by multiplying this given bulk 
 of mercury, and noting and marking upon the paper the level of 
 each addition as its surface becomes smooth. Ten times the 
 
GRADUATION OF TUBES. 197 
 
 i * 
 
 above weight of mercury gives a decimetral division, and one- 
 tenth of it a millimetral division, and thus we have an easy mode 
 of enlarging or diminishing the subdivisions of the scale. The 
 ink marks are subsequently sunk into the glass with the diamond 
 or file, or, still better, by the action of fluoric acid, as will be 
 described directly. 
 
 By having the tubes accurately graduated so that their divi- 
 sions exactly correspond with the weights of the balance, we 
 acquire the convenience of calculating at once the weight of gases 
 from their measured volume. 
 
 The plan of consecutive weighings, involves a good deal of 
 trouble and labor where large vessels are being prepared, and 
 hence, in such cases, the convenience of this mode of multiplying 
 the divisions by an accurately adjusted measure. 
 
 In marking the scale, let those lines designating the tenths ex- 
 tend in width a little beyond those denoting the twentieths, and 
 these latter, in their turn, a little beyond those expressing the 
 hundredths. Fig. 101 represents a graduated glass with a pro- 
 perly written scale, upon which the tenths are shown by figures. 
 
 As these glasses are to be standard graduates for a variety of 
 purposes in the laboratory, the scale should be indelible, or 
 etched upon the glass. For this purpose the paper scale must be 
 covered with a thin transparent film of melted white wax. When 
 the wax has cooled and hardened, the lines and figures are graved 
 out of the paper with a sharp-pointed style or burin, and the ex- 
 posed surfaces of the glass subjected to the action of fluohydric 
 acid, as directed at p. 79. This done, and the wax scraped off, 
 the etched portions show out distinctly, and are better defined 
 than if they had been scratched, as is sometimes done, with the 
 diamond-point or file. 
 
 Be careful that the subdivisions conform accurately among 
 themselves, and in the aggregate precisely with their integer. 
 The volumes, as expressed by the lines on the scale, should also 
 exactly agree with their corresponding weights, for upon these 
 conditions depends the accuracy of results. 
 
 Tubes for eudiometry, Fig. 103, and proof-glasses for alkali- 
 metry, Fig. 104, and all other vessels used in chemical operations 
 for measuring, are graduated in like manner. The bell glasses 
 (Fig. 85) for which and all large vessels, water is preferable, 
 
198 
 
 GRADUATED VESSELS. 
 
 should be graduated into double cubic centimetres, so that every 
 divisional line may correspond to two centimetres ; and the tubes 
 into double cubic millimetres, so that every line may correspond 
 to two cubic millimetres. 
 
 Fig. 103. 
 
 Fig. 104. 
 
 Fig. 105. 
 
 Dr. Henry proposes, as a quick and accurate method of gradu- 
 ating tubes for eudiometry, &c., to have a standard tube, 0-08 of 
 an inch in diameter, and carefully divided into 10 equal 
 p ar t s? O f 10 grains of mercury (60 F.) capacity each. 
 This tube (Fig. 105) is a graduated pipette, fitted with 
 a stop-cock and air-screw to promote its efficiency. It 
 serves to measure or weigh out a standard measure of 
 mercury in successive tenths or hundredths, as may be 
 required, and according as it may be graduated. 
 
 The vessels should be of clear glass. The tubes must 
 be thick, and strong enough to support the weight of 
 their full contents of mercury. For the convenience of 
 closing their mouths with glass disks, their ends may be 
 ground flat and even. 
 
 In all operations of graduation, the waste of mercury 
 is avoided by working over a porcelain plate, or, what is 
 better, the mercury trough, Fig. 115. The metal may 
 be conveyed to the vessels in the pipette, Fig. 107, 
 which enables the addition or removal of minute por- 
 tions, as the case may require. 
 
GRADUATED VESSELS. 
 
 199 
 
 The requirements of the laboratory call for an assorted stock 
 of graduated tubes and proof-glasses, varying in diameter from a 
 quarter to two inches. 
 
 Below is a useful table, showing the value of the measures of 
 capacity in cubic inches, grains, and as compared with apothe- 
 caries' measure. 
 
 
 
 Grains of dis- 
 
 Apothecaries' 
 
 
 Cubic inches. 
 
 tilled water. 
 
 measure. 
 
 Imperial gallon, . 
 
 277-274 
 
 70000 
 
 9-966 -f- 
 
 Imperial pint, . " 
 
 34-65925 
 
 8750 
 
 
 Imperial fluidounce, 
 
 1-7329625 
 
 437-5 
 
 
 The old wine pint, 
 
 28-8827 
 
 7291-666 
 
 16 fl. oz. . 
 
 Old fluidounce, 
 
 1-805169 
 
 455-73 
 
 8 drachms. 
 
 Cubic inch, ' -v'. *. 
 
 1- 
 
 252-458 
 
 
 Litre, . 
 
 61-02525 
 
 15406-312 
 
 2-1135 pints. 
 
 Decilitre, . . .-'. 
 
 6-10252 
 
 1540631 
 
 3-3816 fl. oz. 
 
 Centilitre, . . . >/ 
 
 0-61025 
 
 154-063 
 
 2-7053 fl. drachms. 
 
 Millilitre, . , ?f ""''*' 
 
 0-06102 
 
 15-406 
 
 16-2318 minims. 
 
 Pipettes. These are tubes for measuring liquids in drops, and 
 consist wholly of glass, blown after either of the forms shown by 
 Figs. 106, 109. The lower and capillary end of the pipette being 
 
 placed in the liquid, is to be closed at the upper 
 ^ lg ' 106 ' end by the thumb, as soon as the liquid in the Fig ' 107> 
 bore has reached the level of that in the con- 
 taining vessel. It is next brought immediately 
 over thfc receiving vessel in which it is to be 
 wholly or partly emptied, when the thumb is 
 alternately raised and lowered until a sufficient 
 number of drops has been forced out by atmo- 
 spheric pressure to make up the volume or 
 weight required, as the case may be. If the bore is 
 too large, the liquid will run out in a thin stream, 
 instead of drops. As the liquid rises in the bore of the 
 pipette in proportion to the pressure of the external 
 liquid, the deeper it is plunged into the containing 
 vessel the greater the amount it will draw up. 
 
 The flow of the liquid is completely under the control 
 of the operator, it being only necessary to press down 
 the thumb upon the mouth, to stop, completely, the dropping 
 from the lower end. The above patterns are designed for very 
 small operations. To be convenient for large quantities of li- 
 
200 
 
 PIPETTES. 
 
 . 108. 
 
 quid, they should be blown from a tube ten inches long, and with 
 an inch bulb above the centre, 
 as shown by Fig. 108, so as to Fig - m 
 form a reservoir. 
 
 This pipette may be filled by 
 applying the mouth to the upper 
 end, and sucking in the liquid ; 
 but the method is disagreeable to 
 the operator when acid or other 
 noxious fumes are natural to the 
 liquid, and moreover it intro- 
 duces moisture. The better plan, 
 in such cases, is to make the 
 pipette by drawing out the lower 
 end of a tube to a capillary 
 opening, and widening the upper, 
 and then stretching a piece of 
 india-rubber cloth tightly over 
 the top, as shown by Fig. 109 ; or, more easily 
 still, covering the bulb-pipette, at its top, with a 
 caoutchouc ball. By compressing the bottle with 
 the hand, or pressing against the india-rubber 
 cover with the thumb, the air within the implement is partially 
 forced out, and the liquid into 
 which the pipettes are plunged 
 immediately runs in to fill its 
 place. The india-rubber having 
 then regained its original state 
 of distension by means of the up- 
 ward pressure of the atmosphere, 
 retains the liquid so completely 
 that not a drop drains off until 
 expelled by again pressing the bag or cover. 
 
 Another form of implement for measuring drops of 
 liquid is Schuster's alkalimeter, shown by Fig. 110. 
 It is a glass bottle, of 1 oz. capacity, with a ground 
 stopper, from which the liquid issues dropwise, when 
 the admission of air is properly adjusted by means of 
 the stopper, which should, for that purpose, be held loosely in its 
 place, and not lifted entirely out. 
 
 Fig. 110. 
 
GRADUATED PIPETTES. 
 
 201 
 
 Fig. 112. 
 
 Graduated pipettes are also used for dropping definite quantities, 
 with great precision. One, with caoutchouc cover, is very intelligi- 
 bly represented by Fig. 111. Another form, and that which is much 
 used in volumetric analysis, is shown by Fig. 112. It is known as 
 Mohr's Dropping-tube, and consists of a glass tube drawn out to 
 a capillary opening at the lower 
 end, and graduated into 100 Fig - 113> 
 or divisions. To the capillary 
 orifice a short piece of vulcan- 
 ized india-rubber tubing is at- 
 tached, and in the lower end of 
 this, again, is inserted a short 
 conical piece of glass tubing, 
 which forms the spout through 
 which the liquid is to flow. 
 Clasping the india-rubber neck 
 is a bent wire, which so com- 
 presses it as to make a water- 
 tight joint; when, however, the 
 grasp is relaxed by pressing the 
 projecting ends of the wires be- 
 tween the thumb and fingers, 
 the liquid flows through the 
 neck dropwise, in slow or quick 
 succession, according as the 
 pressure is gentle or strong, the flow being 
 controlled by this means. 
 
 Some chemists prefer to use syringes 
 for measuring liquids in drops, and these 
 
 instruments are of glass, and as presented by Fig. 113. The 
 liquid is drawn into them by immersing the lower end in the con- 
 taining vessel and raising the piston. On pressing the top of 
 the piston with the thumb, the liquid is driven out again, in 
 quantity proportional to the force employed, a gentle depression 
 expelling it dropwise and slowly. The stratum of air between 
 the piston and surface of the liquid, as represented in the draw- 
 ing, assists the action. 
 
 When the barrel of the syringe is graduated, like that shown 
 in the figure which exhibits Alsop's minimeter, it allows the 
 
202 
 
 MEASUREMENT OF GASES. 
 
 Fig. 114. 
 
 transfer of a given quantity of liquid from one vessel to another 
 at a single operation. To this end, it is only necessary to adjust 
 the motion of the piston, so as to exactly draw in the required 
 measure ; and if an excess should be accidentally taken up, to 
 gently depress the piston until it is expelled and the barrel is 
 filled only to the proper degree or division. 
 
 MEASUREMENT OF GASES.* In measuring a required 
 volume of any gas, a graduated tube, like the one shown 
 in Fig. 114, is first filled with mercury or water, as the 
 case may be, in the pneumatic trough, and placed upon 
 the shelf. When the tube is too slender to sustain itself 
 in an upright position, it is then convenient to use the 
 clamp and support A, Fig. 115. If the mouth of the 
 receptacle of the gas is wide, it is necessary, before trans- 
 ferring to the graduating tube, to place a small funnel in 
 its submerged end, so that the ascending bubbles may be 
 received upon a larger surface. By giving the reservoir, 
 generally a bell glass, a slightly inclined position, so that 
 the edge of its mouth may reach under the funnel, the 
 transfer is made easily and without loss. As soon as 
 the requisite quantity has been transferred, the connection must 
 
 be broken, and both the 
 bell and tube made to 
 resume their former po- 
 sitions on the shelf. 
 (See Transfer of Cras- 
 es.) The tube is then 
 to be depressed in the 
 trough until the metal, 
 inside and outside, is at 
 the same level. This 
 mode subjects the gas 
 only to atmospheric 
 pressure, but the tube 
 must be held by a cork- 
 lined clamp, as in Fig. 
 
 Fig. 115. 
 
 * See Regnault's Chemistry, and article EUDIOMETER in Handworterbuch der 
 Chemie. The latter explains the details of Bunsen's method for graduating tubes 
 and measuring gases. 
 
MEASUREMENT OF GASES. 203 
 
 115, or linen holder, and not in the naked hand, the warmth of 
 which, by expanding the gas, would be a source of error. 
 
 It is very difficult to transfer a quantity of gas exactly corre- 
 sponding with a division of the tube at one trial several attempts 
 are requisite, except in cases of consummate manipulation. It is 
 perhaps better to transfer the last portions from a small tube. 
 The gas passing through very slowly and in fine bubbles can, by 
 this arrangement, be stopped off as soon as the volume which has 
 entered accords with the division indicated. When more than 
 sufficient has been transferred, place the first finger upon the 
 mouth of the tube so as to leave a partial opening, and incline it 
 sufficiently to allow the exit of the redundant gas. Examine anew 
 the contained volume, and if it is still in excess, repeat this ope- 
 ration until the level of the liquid reaches the proper height. 
 
 To insure accuracy in the comparison of volumes of different 
 gases, they must necessarily be measured at the same temperature 
 and under the same pressure. The proof-glasses in which they 
 are estimated, should be kept out of the influence of unequal 
 warmth during the process, for the action of heat upon the volume 
 of gases is a cause of considerable error. 
 
 In order to determine with precision the exact height which 
 the water or mercury assumes, the vessel should be placed at re- 
 pose upon a level shelf, and the eye directed on a line with the 
 surface of the fluids, and the height read off accordingly. This 
 notation requires some care and precision, for as mercury assumes 
 a convex surface, owing to its own cohesion, and water a concave 
 one, because of the attraction for the walls of the tube, especially 
 in narrow cylinders, the curve thus occasioned presents an impedi- 
 ment to the ready determination of the exact level. To provide 
 against the action of the heat of the body, it is better to read at 
 a distance of several yards, through a spy-glass. 
 
 "When water is the confining fluid, read the real surface in the 
 middle of the dark zone formed by the water around the inner 
 walls of the tube ; on the other hand, when mercury is used, 
 "place the real surface in a line drawn exactly in the centre 
 between the highest point of the surface of the mercury and the 
 points at which the latter is in actual contact with the walls of 
 the tube." 
 
 In either case the temperature of the fluid and gas should be 
 
204 MEASUREMENT OF GASES. 
 
 uniform. When the bulk of the containing fluid is sufficient to 
 allow the entire immersion of the cylinder, this is easily effected ; 
 otherwise, it becomes necessary to equalize the temperature of 
 the surrounding air, by keeping the cylinder exposed to both, in 
 order to determine accurately the degree of the scale at which 
 the mercury or water stands. 
 
 Another important matter, as before mentioned, in the com- 
 parison of volumes of different gases, is the necessity of uniform 
 pressure, in their measurement. If the level of the containing 
 fluid within and without the cylinder exactly corresponds, the 
 pressure upon it is directly shown by the barometer. A higher 
 level, internally, indicates less pressure, and vice versa: when 
 the fluid stands higher outside of the cylinder than within it, the 
 level may be restored by raising the tube ; in the opposite case, 
 by depressing the tube. These operations of adjusting the level 
 are 1 more difficult when mercury is the containing fluid. In 
 operations occupying much time, the barometer should be fre- 
 quently consulted, so as to guard against any alteration sufficient 
 to impair the results. 
 
 Ker's tube, constructed for 
 the measurement of gas at the 
 time of its disengagement, is 
 shown by Fig. 116. The branch 
 a, ten inches in length, glass 
 stoppered and graduated to two 
 cubic inches, is the recipient of 
 the gas disengaged from the 
 
 material in the bulb c, by the action of a reagent introduced in 
 the other branch 6. The gas collecting in a is there measured 
 by the scale, previous to being transferred for examination. 
 
MEASUREMENT OF TEMPERATURE. 
 
 205 
 
 CHAPTER X. 
 
 MEASUREMENT OF TEMPERATURE. 
 
 TEMPERATURE is estimated by means of two instruments, the 
 pyrometer and thermometer, the action of which is based upon 
 the relative expansibility of bodies under the influence of heat 
 and cold. They do not therefore indicate the amount of heat 
 contained in the body, but only the comparative temperature of 
 two or more bodies. 
 
 The Pyrometer. This instrument is rarely used in the ordi- 
 nary operations of the laboratory, it being only applicable to the 
 measurement of heats more intense than can be borne by thermo- 
 meters. Pyrometers are constructed of solid substances, though 
 gaseous bodies, on account of their sensitiveness to heat or cold 
 and greater uniformity of expansion, would be preferable. Wedg- 
 wood's Pyrometer is the oldest invention, but Daniell's instru- 
 ment is the most approved, and by skilful management may be 
 made to give accurate indications. Its principal application is in 
 furnace operations. In assaying, where the required tempera- 
 ture varies with the metal under process, it is particularly avail- 
 Fig. 117. 
 
 able in determining the heat of the furnace ; for much of the 
 accuracy of the assay depends upon the temperature at which it 
 is made. Fig. 117 represents the apparatus. 
 
206 THE PYROMETER. 
 
 " It consists of two parts, which may be distinguished as the 
 register 1, and the scale 2. The register A, is a solid bar of 
 blacklead earthenware highly baked. In this a hole a a, is 
 drilled, into which a bar of any metal, six inches long, may be 
 dropped, and which will then rest upon its solid end. A cylin- 
 drical piece of porcelain c, called the index, is then placed upon 
 the top of the bar, and confined in its place by a ring or strap of 
 platinum d, passing round the top of the register, which is partly 
 cut away at the top, and tightened by a wedge of porcelain e. 
 When such an arrangement is exposed to high temperature, it is 
 obvious that the expansion of the metallic bar will force the index 
 forward to the amount of the excess of its expansion over that of 
 the blacklead, and that when again cooled it will be left at the 
 point of greatest elongation. What is now required, is the 
 measurement of the distance which the index has been thrust 
 forward from its first position, and this, though in any case but 
 small, may be effected with great precision by means of the 
 scale." 
 
 " This is independent of the register, and consists of two rules 
 of brass,// and #, accurately joined together at a right angle by 
 their edges, and fitting square upon the two sides of the black- 
 lead bar. At one end of this double rule, a small plate of brass 
 A, projects at a right angle, which may be brought down upon 
 the shoulder of the register formed by the notch cut away for the 
 reception of the index. A movable arm D is attached to this 
 frame, turning at its fixed extremity on a centre i 9 and at its 
 other carrying the arc of a circle, whose radius is exactly five 
 inches, accurately divided into degrees, and thirds of a degree. 
 Upon this arm, at the centre of the circle &, another lighter arm 
 c, is made to turn, one end of which carries a nonius H with it, 
 which moves upon the face of the arc, and subdivides the for- 
 mer graduation into minutes of a degree ; the other end crosses 
 the centre and terminates in an obtuse steel point m, turned in- 
 wards at a right angle. 
 
 " When an observation is to be made, a bar of platinum or 
 malleable iron is placed in the cavity of the register ; the index 
 is to be pressed down upon it, and firmly fixed in its place by 
 the platinum strap and porcelain wedge. The scale is then to be 
 applied by carefully adjusting the brass rule to the sides of the 
 
THERMOMETERS. 207 
 
 register, and fixing it by pressing the cross-piece upon the 
 shoulder, and placing the movable arm so that the steel part of 
 the radius may drop into a small cavity made for its reception, 
 and coinciding with the axis of the metallic bar. The minute of 
 the degree must then be noted which the nonius indicates upon 
 the arc. A similar observation must be made after the register 
 has been exposed to the increased temperature which it is de- 
 signed to measure, and again cooled, and it will be found that 
 the nonius has been moved forward a certain number of degrees 
 or minutes. The scale of this pyrometer is readily connected 
 with that of the thermometer by immersing the register in boil- 
 ing mercury, whose temperature is as constant as that of boiling 
 water, and has been accurately determined by the thermometer. 
 The amount of expansion for a known number of degrees is thus 
 determined, and the value of all other expansions may be con- 
 sidered as proportionate." 
 
 " The following is a list of the melting-points of some of the 
 metals, and it is obvious that in an assay of each particular 
 metal, the temperature employed must exceed by a considerable 
 number of degrees its melting-point. The table is, therefore, 
 very useful. 
 
 Fahrenheit 
 
 Tin melts at . . .'.' . .. v .; . '. 422 
 
 Bismuth, , ' .' - ^ > ^ , ^ ^ 407 
 
 Lead, . _ . '.;' .. ' . ' .. % ' '. -. 612 
 
 Zinc, t. - . . . ' . .- ; jj 773 
 
 Cadmium, . \ ,. , . + t '. ' ,. \ . 442 
 
 Silver, . 7 . * . . I860 
 
 Copper, ; * v. - * ' . -'- 'yV 1996 
 
 Gold, . :. ; . .* Y . ,] 2016 
 
 Cast iron, . ' . ' . .^', V . 2786 
 
 Cobalt and nickel rather less fusible than iron." 
 
 Daniell. 
 
 Thermometers. A thermometer consists of a graduated cylin- 
 drical stem, with a uniform capillary bore, having one of its ends 
 blown into a bulb and filled with mercury or alcohol, and the 
 other hermetically closed, the space above the column of fluid 
 being a vacuum, or as nearly as possible devoid of air. 
 
 Mercury, on account of its greater equability of expansion, 
 and of its boiling-point being as high as 650 F., is more avail- 
 able in the construction of thermometers for measuring tempera- 
 
208 
 
 MEASUREMENT OF TEMPERATURE. 
 
 tures exceeding that of boiling water (212 F.) Alcohol, on the 
 other hand, by reason of its eminent property of dilatation is 
 more applicable for determining temperatures lower than the 
 freezing-point of mercury, its point of congelation being as far 
 down as 90 F. 
 
 The two points of graduation are the freezing and boiling 
 points of water, the interval between each being differently appor- 
 tioned, according as the scale of Fahrenheit, Celsius, or Reaumur 
 (the three most in use) is employed. 
 
 Fahrenheit's scale ranges from 32 to 212 ; that of Celsius 
 (centigrade) from to 100 ; Reaumur's from to 80. The 
 first is most popular in England and in this country ; the second 
 in France, and the third in Russia, Spain, and part of Germany. 
 The scale of Fahrenheit has its zero at 32 below the freezing- 
 point of water, and the other two exactly at that point. There- 
 fore, in comparing the degrees of the former with those of the 
 
 Fahrenheit's 
 Scale. 
 
 Fig. 118. 
 
 Centi?rade 
 Scale. 
 
 Reaumur's 
 Scale. 
 
 212 
 
 192 
 
 152 
 
 152 
 
 112 
 
 S2 
 
 72 
 
 52 
 
 32 . 
 
 100 
 
 80 
 
 60 
 
 40 
 
 20 
 
 
 
 latter, the negative or those below zero have a prefix of the 
 minus ( ) sign, and the positive or those above, the plus (-f ) 
 
THERMOMETERS. 209 
 
 sign. The diagram (Fig. 118) will present the relative position 
 of the corresponding degrees of the three scales. 
 
 The following rules will be found convenient for translating 
 the degrees of one scale into those of another : 
 
 1. To reduce Centigrade degrees to those of Fahrenheit, 
 multiply by 9, and divide by 5, and to the quotient add 32, that 
 is, 
 
 Cent X 9 + 32 = Fahr. 
 5 
 
 2. To reduce Fahrenheit's degrees to Centigrade : 
 
 y 
 
 8. To reduce Reaumur's to Fahrenheit's : 
 
 4. To convert Fahrenheit's to Reaumur's : 
 
 Fahr. 32 X 4 
 - g - = Reaumur. 
 
 A slender stem and precise uniformity of bore are indispensable 
 to the accuracy of a thermometer. The tube must also be en- 
 tirely void of air, as is known when, on being inverted, the con- 
 tained mercury makes a free and rapid descent. Moreover, the 
 graduation of the scale must be verified, and to do this, the bulb 
 is immersed in a mixture of salt and snow to test the accuracy of 
 its freezing degree, and afterwards in boiling water (under the 
 ordinary pressure of the atmosphere) to observe its boiling-point. 
 If in either case when the fluid becomes stationary, after suffi- 
 cient delay for the bulb to accquire the temperature of the bath, 
 it corresponds with the degree marked upon the scale, its gradua- 
 tion as regards the freezing and boiling points is correct. To 
 determine the exactness of the intermediate space, the length of 
 the interval is measured with a pair of compasses, and it is then 
 easy to ascertain by means of an accurate ruler, if the divisions 
 accord with each other, and in the aggregate with the total length 
 of the scale. 
 
 For measuring temperatures higher than 580 F., the top of 
 the thermometer should be unsealed and the mercury exposed to 
 
 14 
 
210 
 
 MEASUREMENT OF TEMPERATURE. 
 
 Fig. 119. the pressure of the atmosphere, for 
 if hermetically closed, it will boil at 
 that point and burst the tube. 
 
 The tube, as before said, should 
 be as slender as possible, and not too 
 long, otherwise in testing shallow 
 solutions in ebullition, that part of 
 the stem which is above the liquor 
 is exposed to the heat of the rising 
 vapor, and as the expansion to mer- 
 cury within would be thus estimated 
 with that of the contents of the bulb, 
 the only part heated at the time of 
 graduation, incorrect conclusions 
 would be drawn. 
 
 In ascertaining the condition of a 
 liquid with regard to heat or cold, 
 the thermometer is gradually intro- 
 duced into it, moved around it seve- 
 ral times so as to produce an equable 
 diffusion of temperature, and after 
 the mercury has become stationary 
 at a certain point, the degree coinci- 
 dent with that point is noted down 
 as the temperature. 
 
 The scales of thermometers are 
 most generally graduated upon a 
 wooden slip or support, to which the 
 stem is secured by clamps and 
 screws. In such case, the scale is 
 hinged, so as to afford convenience 
 in the use of the thermometer for 
 taking the boiling-point of solutions 
 without injury to the scale. 
 
 Thermometers for chemical pur- 
 poses should be wholly of glass and 
 cylindrical, as that form is most con- 
 venient for passing through tubulures; 
 and, moreover, the scales should be 
 
 Fig. 120. 
 
THERMOMETERS. 211 
 
 indestructible. The annexed drawings present one (Fig. 119) 
 with Celsius's scale etched on the outside by fluorine, and another 
 (Fig. 120) with a black letter enamelled, Fahrenheit, scale en- 
 closed in the tube. 
 
 The scales of the mercurial thermometers are made to range 
 as high as 600 F., and for convenience are sometimes graduated 
 on one side of the stem with the Centigrade and on the other 
 with the Fahrenheit scale. Fahrenheit's degrees being small, 
 have the advantage over the others of not giving fractional parts, 
 which are inconvenient in calculation. The laboratory should 
 be supplied with two or more of these implements. 
 
 Air thermometers are sometimes used, and though very deli- 
 cate, are less convenient than those of mercury and alcohol, and 
 liable to objections which do not attach to the latter. 
 
 Leslie's differential thermometer, Fig. 121, which is a modifi- 
 cation of the air thermometer, is now frequent- 
 ly used in researches for determining very 
 small differences in temperature. It consists 
 of a U tube with a hollow bulb blown at each 
 end and closed, so that the fluid within (sul- 
 phuric acid) colored with carmine to render 
 it more visible, is entirely free from external 
 atmospheric pressure. This instrument does 
 not exhibit a change of temperature except by 
 the difference between the elasticity of the air 
 in the two bulbs, and therefore indicates only 
 such temperatures as affect one bulb and not 
 the other. When both bulbs are of equal temperature, the liquid 
 within remains stationary ; but so soon as one becomes warmer 
 than the other the fluid recedes to the opposite bulb, and the 
 scale attached to one of the legs is so graduated as to measure 
 the comparative degree of heat thus occasioned. 
 
 Melloni's thermo-multiplicator (Muller, p. 541), is another in- 
 strument for the indication of changes of temperature. 
 
 Another convenient instrument, especially in meteorological 
 observations, is the thermometrograph. It is so constructed as 
 to register the maximum and minimum temperatures occurring 
 during an interval, and hence the presence of the operator is not 
 necessary to note them at the moment of their occurrence. 
 
212 
 
 MEASUREMENT OF TEMPERATURE. 
 
 The apparatus which is shown in Fig. 122, consists of a mer- 
 curial and a spirit thermometer placed horizontally and parallel 
 to each other. A steel pin enclosed in the tube of the former is 
 pushed before the column of mercury when the metal in the bulb 
 
 Fig. 122. 
 
 expands, but remains fixed when it again recedes on cooling, and 
 thus indicates at that point the maximum temperature which has 
 occurred during any interval. 
 
 The corresponding rod, enclosed in the tube of the spirit 
 thermometer, of glass, colored to render it more visible, is not 
 advanced by the expansion of the spirit, but retreats with the 
 column as it contracts to the last point reached by it, and thus 
 registers the minimum of temperature during a certain time, at 
 the degree coincident with its inner end. 
 
 When this instrument is to be used, it must be inclined in such 
 a position as to allow the steel rod to descend to the column of 
 mercury, and the glass rod to the end of the spirituous column. 
 The arrangement of the bulbs in opposite positions is with a view 
 to this object. After the rods have reached their proper situa- 
 tions, we may, by placing the instrument horizontally any morn- 
 ing or evening, obtain at the end of the following 24 hours, the 
 maximum and minimum temperature of that interval. 
 
 There are some very excellent remarks by Regnault upon the 
 relative advantages of the different modes of measuring tempera- 
 ture, to which the student may advantageously refer. 
 
 The translation of his several papers on the subject, is to be 
 found in the Franklin Institute Journal for 1848. 
 
 The following table shows the corresponding degrees of Fahren- 
 heit's, Reaumur's, and the Centigrade thermometers. 
 
THERMOMETRICAL EQUIVALENTS. 
 
 213 
 
 !* 
 
 Reaumur. 
 
 C 'O 
 
 iu a 
 O , 
 
 Fahren- 
 heit. 
 
 1 
 
 .i w 
 
 I! 
 
 Fahren- 
 heit. 
 
 Reaumur. 
 
 i| 
 
 <3& 
 
 Fahren- 
 heit. 
 
 Reaumur. 
 
 ii 
 
 U& 
 
 * 
 
 600 
 
 52-4 
 
 315-5 
 
 569 
 
 238-6 
 
 298-3 
 
 539 
 
 2253 
 
 281 6 
 
 508 
 
 211-5 
 
 264-4 
 
 599 
 
 52 
 
 315 
 
 568-4 
 
 238-4 
 
 298 
 
 538-2 
 
 225 
 
 281-2 
 
 507-2 
 
 211-2 
 
 264 
 
 598 
 
 51-5 
 
 314-4 
 
 568 
 
 238-2 
 
 297-7 
 
 538 
 
 224-9 
 
 281-1 
 
 507 
 
 211-1 
 
 2638 
 
 567-2 
 
 51-2 
 
 314 
 
 567-5 
 
 238 
 
 297-5 
 
 537-8 
 
 224-8 
 
 281 
 
 506-7 
 
 211 
 
 263-7 
 
 597 
 
 51-1 
 
 3138 
 
 567 
 
 237-7 
 
 297-2 
 
 537 
 
 224-4 
 
 280-5 
 
 506 
 
 2106 
 
 263-3 
 
 596-7 
 
 51 
 
 313-7 
 
 566-6 
 
 237-6 
 
 297 
 
 536 
 
 224 
 
 280 
 
 505-4 
 
 210-4 
 
 263 
 
 596 
 
 50-3 
 
 3133 
 
 566 
 
 237-3 
 
 296-6 
 
 535 
 
 2235 
 
 279-4 
 
 505 
 
 210-2 
 
 2627 
 
 595-4 
 
 250-4 
 
 313 
 
 565-2 
 
 237 
 
 296-2 
 
 534-2 
 
 223-2 
 
 279 
 
 504-5 
 
 210 
 
 262-5 
 
 595 
 
 '50-2 
 
 3127 
 
 565 
 
 236-9 
 
 296-1 
 
 534 
 
 223-1 
 
 278*8 
 
 504 
 
 209-7 
 
 262-2 
 
 594-5 
 
 250 
 
 312-5 
 
 564-8 
 
 236-8 
 
 296 
 
 533-7 
 
 223 
 
 278-7 
 
 503-6 
 
 209-6 
 
 262 
 
 594 
 
 249-7 
 
 312-2 
 
 564 
 
 236-4 
 
 295-5 
 
 533 
 
 222-6 
 
 278-3 
 
 503 
 
 209-3 
 
 261-6 
 
 593-6 
 
 2496 
 
 312 
 
 563 
 
 236 
 
 295 
 
 532-4 
 
 222-4 
 
 278 
 
 502-2 
 
 209 
 
 261-2 
 
 593 
 
 49-3 
 
 311*6 
 
 562 
 
 235-5 
 
 294-4 
 
 532 
 
 222-2 
 
 277-7 
 
 502 
 
 2089 
 
 261-1 
 
 592-2 
 
 249 
 
 311-2 
 
 561-2 
 
 2352 
 
 294 
 
 531-5 
 
 222 
 
 2775 
 
 501-8 
 
 208-8 
 
 261 
 
 592 
 
 248-9 
 
 311-1 
 
 561 
 
 235 1 
 
 293-8 
 
 531 
 
 221-7 
 
 277-2 
 
 501 
 
 208-4 
 
 260-5 
 
 59T8 
 
 248-8 
 
 311 
 
 560-7 
 
 235 
 
 293-7 
 
 5306 
 
 221-6 
 
 277 
 
 500 
 
 208 
 
 260 
 
 591 
 
 248-4 
 
 310-5 
 
 560 
 
 234-6 
 
 293 3 
 
 530 
 
 221-3 
 
 2766 
 
 499 
 
 207-5 
 
 259-4 
 
 590 
 
 248 
 
 310 
 
 559-4 
 
 2344 
 
 293 
 
 529-2 
 
 221 
 
 276-2 
 
 498-2 
 
 207-2 
 
 259 
 
 589 
 
 247-5 
 
 309-4 
 
 559 
 
 234-2 
 
 292-7 
 
 529 
 
 220-9 
 
 276 1 
 
 498 
 
 207-1 
 
 258-8 
 
 588-2 
 
 247-2 
 
 309 
 
 558 5 
 
 234 
 
 292-5 
 
 528-8 
 
 2208 
 
 276 
 
 497-7 
 
 207 
 
 2587 
 
 588 
 
 247-1 
 
 308-8 
 
 558 
 
 233-7 
 
 2922 
 
 528 
 
 220-4 
 
 275-5 
 
 497 
 
 206-6 
 
 2583 
 
 587-7 
 
 247 
 
 308-7 
 
 557-6 
 
 233-6 
 
 292 
 
 527 
 
 220 
 
 275 
 
 496-4 
 
 206-4 
 
 258 
 
 587 
 
 246-6 
 
 308-3 
 
 557 
 
 233-3 
 
 291-6 
 
 526 
 
 219-5 
 
 274-4 
 
 496 
 
 2062 
 
 257-7 
 
 586-4 
 
 246-4 
 
 308 
 
 556-2 
 
 233 
 
 291 2 
 
 5'52 
 
 219-2 
 
 274 
 
 495-5 
 
 206 
 
 257-5 
 
 586 
 
 246-2 
 
 307-7 
 
 556 
 
 2329 
 
 291-1 
 
 525 
 
 219-1 
 
 273-8 
 
 495 
 
 205-7 
 
 257-2 
 
 585-5 
 
 246 
 
 307-5 
 
 5558 
 
 2328 
 
 291 
 
 524-7 
 
 219 
 
 273-7 
 
 494-6 
 
 205-6 
 
 257 
 
 585 
 
 245-7 
 
 307-2 
 
 555 
 
 232-4 
 
 290-5 
 
 524 
 
 218-6 
 
 273-3 
 
 494 
 
 205-3 
 
 256-6 
 
 584-6 
 
 245-6 
 
 307 
 
 554 
 
 232 
 
 290 
 
 523-4 
 
 218-4 
 
 273 
 
 493-2 
 
 205 
 
 256-2 
 
 584 
 
 245-3 
 
 306-6 
 
 553 
 
 231-5 
 
 289-4 
 
 523 
 
 218-2 
 
 272-7 
 
 493 
 
 204-9 
 
 256-1 
 
 583-2 
 
 245 
 
 306-2 
 
 5522 
 
 231-2 
 
 289 
 
 522-5 
 
 218 
 
 272-5 
 
 492-8 
 
 204-8 
 
 256 
 
 583 
 
 244-9 
 
 306-1 
 
 552 
 
 231-1 
 
 288-8 
 
 522 
 
 217-7 
 
 272-2 
 
 492 
 
 204-4 
 
 255-5 
 
 582-8 
 
 244-8 
 
 306 
 
 651-7 
 
 231 
 
 288-7 
 
 521 6 
 
 217-6 
 
 272 
 
 491 
 
 204 
 
 255 
 
 582 
 
 244-4 
 
 305-5 
 
 551 
 
 230-6 
 
 288-3 
 
 521 
 
 217-3 
 
 271-6 
 
 490 
 
 2035 
 
 254-4 
 
 581 
 
 244 
 
 305 
 
 550-4 
 
 230-4 
 
 288 
 
 520-2 
 
 217 
 
 271-2 
 
 489-2 
 
 203-2 
 
 254 
 
 580 
 
 243-5 
 
 304-4 
 
 550 
 
 2302 
 
 287-7 
 
 520 
 
 216-9 
 
 271-1 
 
 489 
 
 203-1 
 
 253-8 
 
 579-2 
 
 243-2 
 
 304 
 
 549-5 
 
 230 
 
 287-5 
 
 519-8 
 
 216-8 
 
 271 
 
 488-7 
 
 203 
 
 253-7 
 
 579 
 
 243-1 
 
 303-8 
 
 549 
 
 229-7 
 
 287-2 
 
 519 
 
 216-4 
 
 270-5 
 
 488 
 
 202-6 
 
 253-3 
 
 578-7 
 
 243 
 
 303-7 
 
 548-6 
 
 229-6 
 
 287 
 
 518 
 
 216 
 
 270 
 
 487-4 
 
 202-4 
 
 253 
 
 578 
 
 242-6 
 
 303-3 
 
 548 
 
 229-3 
 
 286-6 
 
 517 
 
 215-5 
 
 269-4 
 
 487 
 
 202-2 
 
 252-7 
 
 577-4 
 
 242-4 
 
 303 
 
 547-2 
 
 229 
 
 286-2 
 
 516-2 
 
 215-2 
 
 269 
 
 486-5 
 
 202 
 
 252-5 
 
 577 
 
 242-2 
 
 302-7 
 
 547 
 
 2289 
 
 286 1 
 
 516 
 
 215-1 
 
 268-8 
 
 486 
 
 201-7 
 
 252-2 
 
 576-5 
 
 242 
 
 302-5 
 
 546-8 
 
 228-8 
 
 286 
 
 515-7 
 
 215 
 
 268-7 
 
 485-6 
 
 201-6 
 
 252 
 
 576 
 
 241-7 
 
 302-2 
 
 546 
 
 228-4 
 
 2855 
 
 515 
 
 214-6 
 
 268-3 
 
 485 
 
 201-3 
 
 251-6 
 
 575-6 
 
 241-6 
 
 302 
 
 545 
 
 228 
 
 285 
 
 514-4 
 
 214-4 
 
 268 
 
 484-2 
 
 201 
 
 251-2 
 
 575 
 
 241-3 
 
 301-6 
 
 544 
 
 227-5 
 
 284-4 
 
 514 
 
 214-2 
 
 267-7 
 
 484 
 
 200-9 
 
 251-1 
 
 574-2 
 
 241 
 
 301-2 
 
 543-2 
 
 227-2 
 
 284 
 
 513 5 
 
 214 
 
 267-5 
 
 483-8 
 
 200-8 
 
 251 
 
 574 
 
 240-9 
 
 301-1 
 
 543 
 
 227-1 
 
 283-8 
 
 513 
 
 213-7 
 
 267-2 
 
 483 
 
 200-4 
 
 250-5 
 
 573-8 
 
 2408 
 
 301 
 
 542-7 
 
 227 
 
 283-7 
 
 512-6 
 
 213-6 
 
 267 
 
 482 
 
 200 
 
 250 
 
 573 
 
 2404 
 
 300-5 
 
 542 
 
 2266 
 
 283-3 
 
 512 
 
 213-3 
 
 266-6 
 
 481 
 
 199-5 
 
 249-4 
 
 572 
 
 240 
 
 300 
 
 541-4 
 
 226-4 
 
 283 
 
 511-2 
 
 213 
 
 266-2 
 
 480-2 
 
 199-2 
 
 249 
 
 571 
 
 239-5 
 
 299-4 
 
 541 
 
 226-2 
 
 282-7 
 
 511 
 
 212-9 
 
 266-1 
 
 480 
 
 199-1 
 
 248-8 
 
 570-2 
 
 2392 
 
 299 
 
 5405 
 
 226 
 
 282-5 
 
 I510-8 
 
 2128 
 
 266 
 
 479-7 
 
 199 
 
 248-7 
 
 570 
 
 239-1 
 
 298-8 
 
 540 
 
 2257 
 
 282-2 
 
 ^510 
 
 212-4 
 
 265-5 
 
 479 
 
 198-6 
 
 248-3 
 
 569-7 
 
 239 
 
 298-7 
 
 539-6 
 
 2256 
 
 282 
 
 |509 
 
 212 
 
 265 
 
 478-4 
 
 198-4 
 
 248 
 
214 
 
 THERMOMETRICAL EQUIVALENTS. 
 
 S -: 
 
 13 
 
 3 
 
 H 
 
 o & 
 
 s, 
 
 p 
 
 Reaumur. 
 
 11 
 
 o S> 
 
 L 
 
 -G 
 
 x 
 
 Reaumur. 
 
 11 
 
 O be 
 
 Fahren- 
 heit. 
 
 Reaumur. 
 
 A 
 
 II 
 
 478 
 
 198-2 
 
 247-7 
 
 448-2 
 
 185 
 
 231-2 
 
 418 
 
 171-5 
 
 214-4 
 
 388-4 
 
 158-4 
 
 198 
 
 477-5 
 
 198 
 
 2475 
 
 448 
 
 184-9 
 
 231-1 
 
 417-2 
 
 171-2 
 
 214 
 
 388 
 
 158-2 
 
 197-7 
 
 477 
 
 197-7 
 
 247-2 
 
 447-8 
 
 184-8 
 
 231 
 
 417 
 
 171-1 
 
 213-8 
 
 387-5 
 
 158 
 
 197-5 
 
 476-6 
 
 1976 
 
 247 
 
 447 
 
 184-4 
 
 230-5 
 
 416-7 
 
 171 
 
 213-7 
 
 387 
 
 157-7 
 
 197-2 
 
 476 
 
 197-3 
 
 246-6 
 
 446 
 
 184 
 
 230 
 
 416 
 
 170-6 
 
 213-3 
 
 386-6 
 
 157-6 
 
 197 
 
 4752 
 
 197 
 
 2462 
 
 445 
 
 183-5 
 
 229-4 
 
 4154 
 
 170-4 
 
 213 
 
 386 
 
 157-3 
 
 196-6 
 
 475 
 
 1969 
 
 246-1 
 
 444-2 
 
 183-2 
 
 229 
 
 415 
 
 170-2 
 
 212-7 
 
 385-2 
 
 157 
 
 196-2 
 
 474-8 
 
 1968 
 
 246 
 
 444 
 
 183-1 
 
 228-8 
 
 414-5 
 
 170 
 
 212-5 
 
 385 
 
 1569 
 
 196-1 
 
 474 
 
 196-4 
 
 245-5 
 
 443-7 
 
 183 
 
 228-7 
 
 414 
 
 169-7 
 
 212-2 
 
 384-8 
 
 156-8 
 
 196 
 
 473 
 
 196 
 
 245 
 
 443 
 
 182-6 
 
 228-3 
 
 4136 
 
 169-6 
 
 212 
 
 384 
 
 156-4 
 
 195-5 
 
 472 
 
 195-5 
 
 244-4 
 
 442-4 
 
 182-4 
 
 228 
 
 413 
 
 169-3 
 
 211-6 
 
 383 
 
 156 
 
 195 
 
 471-2 
 
 195-2 
 
 244 
 
 442 
 
 182-2 
 
 227-7 
 
 412-2 
 
 169 
 
 211-2 
 
 382 
 
 155-5 
 
 194-4 
 
 471 
 
 195-1 
 
 243-8 
 
 441-5 
 
 182 
 
 227-5 
 
 412 
 
 168-9 
 
 211-1 
 
 381-2 
 
 155-2 
 
 194 
 
 470-7 
 
 195 
 
 243-7 
 
 441 
 
 181-7 
 
 227-2 
 
 411-8 
 
 168-8 
 
 211 
 
 381 
 
 155-1 
 
 193-8 
 
 470 
 
 194-6 
 
 243-3 
 
 440-6 
 
 181-6 
 
 227 
 
 411 
 
 168-4 
 
 210-5 
 
 380-7 
 
 155 
 
 193-7 
 
 469-4 
 
 194-4 
 
 243 
 
 440 
 
 181-3 
 
 226-6 
 
 410 
 
 168 
 
 210 
 
 380 
 
 154-6 
 
 193-3 
 
 469 
 
 194-2 
 
 242-7 
 
 439-2 
 
 181 
 
 2262 
 
 409 
 
 167-5 
 
 209-4 
 
 379-4 
 
 154-4 
 
 193 
 
 468-5 
 
 194 
 
 242-5 
 
 439 
 
 180-9 
 
 226-1 
 
 408-2 
 
 167-2 
 
 209 
 
 379 
 
 154-2 
 
 192-7 
 
 468 
 
 193-7 
 
 242-2 
 
 438-8 
 
 180-8 
 
 226 
 
 408 
 
 167-1 
 
 208-8 
 
 378-5 
 
 154 
 
 192-5 
 
 467-6 
 
 193-6 
 
 242 
 
 438 
 
 1804 
 
 225-5 
 
 407-7 
 
 167 
 
 2087 
 
 378 
 
 153-7 
 
 192-2 
 
 467 
 
 193-3 
 
 241-6 
 
 437 
 
 180 
 
 225 
 
 407 
 
 166-6 
 
 208-3 
 
 377-6 
 
 153-6 
 
 192 
 
 466-2 
 
 193 
 
 241-2 
 
 436 
 
 179-5 
 
 224-4 
 
 406-4 
 
 166-4 
 
 208 
 
 377 
 
 1533 
 
 191-6 
 
 466 
 
 192-9 
 
 241-1 
 
 435-2 
 
 1792 
 
 224 
 
 406 
 
 166-2 
 
 207-7 
 
 376-2 
 
 153 
 
 191-2 
 
 465-8 
 
 192-8 
 
 241 
 
 435 
 
 179-1 
 
 223-8 
 
 405-5 
 
 166 
 
 207-5 
 
 376 
 
 1529 
 
 191-1 
 
 465 
 
 192-4 
 
 240-5 
 
 434-7 
 
 179 
 
 223-7 
 
 405 
 
 1657 
 
 207 2 
 
 375-8 
 
 152-8 
 
 191 
 
 464 
 
 192 
 
 240 
 
 434 
 
 178-6 
 
 223-3 
 
 4046 
 
 1656 
 
 207 
 
 375 
 
 152-4 
 
 190-5 
 
 463 
 
 191-5 
 
 239-4 
 
 433-4 
 
 178-4 
 
 223 
 
 404 
 
 165-3 
 
 206-6 
 
 374 
 
 152 
 
 190 
 
 462-2 
 
 191-2 
 
 239 
 
 433 
 
 178-2 
 
 222-7 
 
 403-2 
 
 165 
 
 2062 
 
 373 
 
 151 5 
 
 189-4 
 
 462 
 
 191-1 
 
 238-8 
 
 432-5 
 
 178 
 
 222-5 
 
 403 
 
 164-9 
 
 206-1 
 
 372-2 
 
 151-2 
 
 189 
 
 461-7 
 
 191 
 
 238-7 
 
 432 
 
 177-7 
 
 222-2 
 
 402-8 
 
 164-8 
 
 206 
 
 372 
 
 151-1 
 
 188-8 
 
 461 
 
 190-6 
 
 2383 
 
 431-6 
 
 177-6 
 
 222 
 
 402 
 
 164-4 
 
 205-5 
 
 371-7 
 
 151 
 
 188-7* 
 
 460-4 
 
 190-4 
 
 238 
 
 431 
 
 177-3 
 
 221 6 
 
 401 
 
 164 
 
 205 
 
 371 
 
 150-6 
 
 188-3 
 
 460 
 
 190-2 
 
 237-7 
 
 430-2 
 
 177 
 
 221-2 
 
 400 
 
 163-5 
 
 204-4 
 
 370-4 
 
 150-4 
 
 188 
 
 459-5 
 
 190 
 
 237-5 
 
 430 
 
 1769 
 
 221-1 
 
 399-2 
 
 163-2 
 
 204 
 
 370 
 
 1 50-2 
 
 187-7 
 
 459 
 
 189-7 
 
 237-2 
 
 429-8 
 
 1768 
 
 221 
 
 399 
 
 163-1 
 
 203-8 
 
 3695 
 
 150 
 
 187-5 
 
 4586 
 
 189-6 
 
 237 
 
 429 
 
 176-4 
 
 220 5 
 
 398-7 
 
 163 
 
 203 7 
 
 369 
 
 1497 
 
 187-2 
 
 458 
 
 189-3 
 
 236-6 
 
 428 
 
 176 
 
 220 
 
 398 
 
 162-6 
 
 2033 
 
 368-6 
 
 149-6 
 
 187 
 
 457-2 
 
 189 
 
 2362 
 
 427 
 
 1755 
 
 219-4 
 
 397-4 
 
 162-4 
 
 203 
 
 368 
 
 149-3 
 
 1866 
 
 457 
 
 188-9 
 
 236-1 
 
 426-2 
 
 175-2 
 
 219 
 
 397 
 
 1622 
 
 202-7 
 
 367-2 
 
 149 
 
 186-2 
 
 4568 
 
 88-8 
 
 236 
 
 426 
 
 1751 
 
 218-8 
 
 396-5 
 
 162 
 
 202-5 
 
 367 
 
 148-9 
 
 186-1 
 
 456 
 
 88-4 
 
 235-5 
 
 4257 
 
 175 
 
 218-7 
 
 396 
 
 161-7 
 
 202-2 
 
 3668 
 
 148-8 
 
 186 
 
 455 
 
 88 
 
 235 
 
 425 
 
 174-6 
 
 218-3 
 
 3956 
 
 161 6 
 
 202 
 
 366 
 
 148-4 
 
 185-5 
 
 454 
 
 87-5 
 
 234-4 
 
 424-4 
 
 174-4 
 
 218 
 
 395 
 
 161 3 
 
 201-6 
 
 365 
 
 148 
 
 185 
 
 453-2 
 
 87-2 
 
 234 
 
 424 
 
 174-2 
 
 217-7 
 
 394-2 
 
 161 
 
 201-2 
 
 364 
 
 147-5 
 
 184-4 
 
 453 
 
 87-1 
 
 233-8 
 
 423-5 
 
 174 
 
 217-5 
 
 394 
 
 160-9 
 
 201-1 
 
 3632 
 
 147-2 
 
 184 
 
 452-7 
 
 87 
 
 233-7 
 
 423 
 
 173-7 
 
 217-2 
 
 393-8 
 
 160-8 
 
 201 
 
 363 
 
 147-1 
 
 183-8 
 
 452 
 
 86-6 
 
 2333 
 
 422-6 
 
 173 6 
 
 217 
 
 393 
 
 1604 
 
 2005 
 
 362-7 
 
 147 
 
 183-7 
 
 451-4 
 
 86-4 
 
 233 
 
 422 
 
 173-3 
 
 2166 
 
 392 
 
 160 
 
 200 
 
 362 
 
 1466 
 
 183-3 
 
 451 
 
 86-2 
 
 232-7 
 
 421-2 
 
 173 
 
 216-2 
 
 391 
 
 159-5 
 
 99-4 
 
 361-4 
 
 146-4 
 
 183 
 
 450-5 
 
 86 
 
 232-5 
 
 421 
 
 172-9 
 
 216-1 
 
 390-2 
 
 159-2 
 
 99 
 
 361 
 
 146-2 
 
 182-7 
 
 450 
 
 857 
 
 32-2 
 
 420-8 
 
 172-8 216 
 
 390 
 
 59-1 
 
 988 
 
 360-5 
 
 146 
 
 182-5 
 
 449-6 
 
 856 
 
 232 
 
 420 
 
 172-4 
 
 215-5 
 
 389-7 
 
 159 
 
 98-7 
 
 360 
 
 1457 
 
 182-2 
 
 449 
 
 85-3 
 
 231-6 
 
 419 
 
 72 
 
 215 
 
 389 
 
 1586 
 
 198-3 
 
 3596 
 
 145-6 
 
 182 
 
THERMOMETRICAL EQUIVALENTS. 
 
 215 
 
 fa 
 
 p 
 
 Reaumur. 
 
 "I* 
 
 Sg 
 
 U so 
 
 P 
 
 Reaumur. 
 
 . 5 
 
 11 
 
 A 
 
 u S 
 11 
 
 M 
 
 Reaumur. 
 
 11 
 
 u 
 
 t.2 
 
 I 1 
 
 Reaumur. 
 
 11 
 
 tt> 
 
 359 
 
 1453 
 
 181 6 
 
 329 
 
 132 
 
 165 
 
 299 
 
 118-6 
 
 148-3 
 
 269-6 
 
 105-6 
 
 132 
 
 358-2 
 
 145 
 
 181-2 
 
 328 
 
 131-5 
 
 164-4 
 
 298-4 
 
 118-4 
 
 148 
 
 269 
 
 1053 
 
 131-6 
 
 358 
 
 144-9 
 
 181-1 
 
 327-2 
 
 131-2 
 
 164 
 
 298 
 
 1182 
 
 147-7 
 
 268-2 
 
 105 
 
 131-2 
 
 3578 
 
 144-8 
 
 181 
 
 327 
 
 131 1 
 
 163-9 
 
 297-5 
 
 118 
 
 147-5 
 
 268 
 
 104 8 
 
 131-1 
 
 357 
 
 144-4 
 
 180-5 
 
 326-7 
 
 131 
 
 163-7 
 
 297 
 
 117-7 
 
 1472 
 
 267-8 
 
 104-8 
 
 131 
 
 356 
 
 144 
 
 180 
 
 326 
 
 130-6 
 
 163-3 
 
 2966 
 
 1176 
 
 147 
 
 267 
 
 104-4 
 
 130-5 
 
 355 
 
 143-5 
 
 1794 
 
 325-4 
 
 130-4 
 
 163 
 
 296 
 
 117-3 
 
 1466 
 
 266 
 
 104 
 
 130 
 
 354-2 
 
 143-2 
 
 179 
 
 325 
 
 130-2 
 
 162-7 
 
 295-2 
 
 117 
 
 1462 
 
 265 
 
 103 5 
 
 129-4 
 
 354 
 
 143 1 
 
 178-8 
 
 324-5 
 
 130 
 
 162-5 
 
 295 
 
 1169 
 
 146-1 
 
 264-2 
 
 1032 
 
 129 
 
 353-7 
 
 143 
 
 1787 
 
 324 
 
 129-7 
 
 162-2 
 
 2948 
 
 1168 
 
 146 
 
 264 
 
 103-1 
 
 128-9 
 
 353 
 
 142 6 
 
 178-3 
 
 323-6 
 
 129-6 
 
 162 
 
 294 
 
 116-4 
 
 145-5 
 
 263-7 
 
 103 
 
 128-7 
 
 352-4 
 
 142-4 
 
 178 
 
 323 
 
 129-3 
 
 161-6 
 
 293 
 
 116 
 
 145 
 
 263 
 
 102-6 
 
 1283 
 
 352 
 
 1422 
 
 177-7 
 
 322-2 
 
 129 
 
 161 2 
 
 292 
 
 115-5 
 
 144-4 
 
 262-4 
 
 102-4 
 
 128 
 
 351-5 
 
 142 
 
 177-5 
 
 322 
 
 1288 
 
 161-1 
 
 291 2 
 
 1152 
 
 144 
 
 262 
 
 102-2 
 
 127-7 
 
 351 
 
 141 8 
 
 177-2 
 
 321-8 
 
 1288 
 
 161 
 
 291 
 
 115-1 
 
 143-8 
 
 261-5 
 
 102 
 
 127 5 
 
 350-6 
 
 141-6 
 
 177 
 
 321 
 
 128-4 
 
 1605 
 
 290-7 
 
 115 
 
 1437 
 
 261 
 
 101-7 
 
 127-2 
 
 350 
 
 141-3 
 
 176-6 
 
 320 
 
 128 
 
 160 
 
 290 
 
 1146 
 
 143-3 
 
 260-6 
 
 101-6 
 
 127 
 
 349-21141 
 
 176-2 
 
 319 
 
 127-5 
 
 159-4 
 
 289-4 
 
 1144 
 
 143 
 
 260 
 
 101-3 
 
 1266 
 
 349 
 
 140-9 
 
 176-1 
 
 ^18-2 
 
 127-2 
 
 159 
 
 289 
 
 1142 
 
 1427 
 
 259-2 
 
 101 
 
 1262 
 
 348-8 
 
 140-8 
 
 176 
 
 318 
 
 127-1 
 
 158-8 
 
 288-5 
 
 114 
 
 142-5 
 
 259 
 
 100-8 
 
 126-1 
 
 348 
 
 1404 
 
 175-5 
 
 317-7 
 
 127 
 
 158-7 
 
 288 
 
 113-7 
 
 1422 
 
 258-8 
 
 1008 
 
 126 
 
 347 
 
 140 
 
 175 
 
 317 
 
 126-6 
 
 1583 
 
 287-6 
 
 1136 
 
 142 
 
 258 
 
 100-4 
 
 125-5 
 
 346 
 
 139-5 
 
 174-4 
 
 316-4 
 
 1264 
 
 158 
 
 287 
 
 113-3 
 
 141-6 
 
 257 
 
 100 
 
 125 
 
 3452 
 
 1392 
 
 174 
 
 316 
 
 1262 
 
 1577 
 
 286-2 
 
 113 
 
 141-2 
 
 256 
 
 99-5 
 
 124-4 
 
 345 
 
 139 1 
 
 173-8 
 
 3155 
 
 126 
 
 157-5 
 
 286 
 
 1128 
 
 141-1 
 
 255-2 
 
 99-2 
 
 124 
 
 344-7 
 
 139 
 
 173-7 
 
 315 
 
 125-7 
 
 157-2 
 
 2858 
 
 1128 
 
 141 
 
 255 
 
 99-1 
 
 1238 
 
 344 
 
 138-6 
 
 1733 
 
 314-6 
 
 125-6 
 
 157 
 
 285 
 
 1124 
 
 1405 
 
 254-7 
 
 99 
 
 123-7 
 
 3434 
 
 1384 
 
 173 
 
 314 
 
 125-3 
 
 156-6 
 
 284 
 
 112 
 
 140 
 
 254 
 
 98-6 
 
 123-3 
 
 343 
 
 1382 
 
 172-7 
 
 3132 
 
 125 
 
 156-2 
 
 283 
 
 111-5 
 
 1394 
 
 2534 
 
 98-4 
 
 123 
 
 342-5 
 
 138 
 
 172-5 
 
 313 
 
 1248 
 
 156-1 
 
 282-2 
 
 111-2 
 
 139 
 
 253 
 
 98-2 
 
 122-7 
 
 342 
 
 137-7 
 
 1722 
 
 3128 
 
 124-8 
 
 156 
 
 282 
 
 111-1 
 
 1389 
 
 2525 
 
 98 
 
 122-5 
 
 341 6 
 
 137-6 
 
 172 
 
 3*12 
 
 124 5 
 
 155-5 
 
 281-7 
 
 111 
 
 138-7 
 
 252 
 
 97-9 
 
 122-2 
 
 341 
 
 137-3 
 
 171-6 
 
 311 
 
 124 
 
 155 
 
 281 
 
 110-6 
 
 1383 
 
 251-6 
 
 97-6 
 
 122 
 
 340-2 
 
 137 
 
 171-2 
 
 310 
 
 123-5 
 
 1544 
 
 280-4 
 
 110-4 
 
 138 
 
 251 
 
 97-3 
 
 121-6 
 
 340 
 
 1369 
 
 171-1 
 
 309-2 
 
 1232 
 
 154 
 
 280 
 
 110-2 
 
 137-7 
 
 250-2 
 
 97 
 
 121 2 
 
 339-8 
 
 1368 
 
 171 
 
 309 
 
 123-1 
 
 1538 
 
 279-5 
 
 110 
 
 137-5 
 
 250 
 
 96-9 
 
 121-1 
 
 339 
 
 136-4 
 
 170-5 
 
 3087 
 
 123 
 
 1537 
 
 279 
 
 1097 
 
 137-2 
 
 249-8 
 
 968 
 
 121 
 
 338 
 
 136 
 
 170 
 
 308 
 
 1226 
 
 153-3 
 
 278-6 
 
 109-6 
 
 137 
 
 249 
 
 96-4 
 
 120-5 
 
 337 
 
 1355 
 
 169-4 
 
 307-4 
 
 122-4 
 
 153 
 
 278 
 
 1093 
 
 136-6 
 
 248 
 
 96 
 
 120 
 
 336-2 
 
 135-2 
 
 169 
 
 307 
 
 122 2 
 
 152-7 
 
 277-2 
 
 109 
 
 136-2 
 
 247 
 
 95 5 
 
 119-4 
 
 336 
 
 135-1 
 
 168-8 
 
 306-5 
 
 122 
 
 152-5 
 
 277 
 
 108-8 
 
 136-1 
 
 246-2 
 
 95-2 
 
 119 
 
 335-7 
 
 135 
 
 168-7 
 
 306 
 
 121-7 
 
 152-2 
 
 276-8 
 
 108-8 
 
 136 
 
 246 
 
 95 1 
 
 118-9 
 
 335 
 
 134-6 
 
 1683 
 
 305-6 
 
 121 6 
 
 152 
 
 276 
 
 1084 
 
 135-5 
 
 2457 
 
 95 
 
 118-7 
 
 334-4 
 
 134-4 
 
 168 
 
 305 
 
 121-3 
 
 151-6 
 
 275 
 
 108 
 
 135 
 
 245 
 
 946 
 
 118-3 
 
 334 
 
 134-2 
 
 167-7 
 
 304-2 
 
 121 
 
 151 2 
 
 274 
 
 107-5 
 
 134-4 
 
 244-4 
 
 94-4 
 
 118 
 
 333-5 
 
 134 
 
 167-5 
 
 304 
 
 120-9 
 
 151-1 
 
 2732 
 
 1072 
 
 134 
 
 244 
 
 94-2 
 
 117-8 
 
 333 
 
 133-7 
 
 1672 
 
 3038 
 
 1208 
 
 151 
 
 273 
 
 107 1 
 
 1338 
 
 243-5 
 
 94 
 
 117-5 
 
 332-6 
 
 133-6 
 
 167 
 
 303 
 
 120-4 
 
 150-5 
 
 2727 
 
 107 
 
 1337 
 
 243 
 
 938 
 
 117-2 
 
 332 
 
 133-3 
 
 1666 
 
 302 
 
 120 
 
 150 
 
 272 
 
 106-6 
 
 1333 
 
 2426 
 
 936 
 
 117 
 
 331-2 
 
 133 
 
 166-2 
 
 301 
 
 119-5 
 
 149-4 
 
 271-4 
 
 106 4 
 
 133 
 
 242 
 
 93-3 
 
 1166 
 
 331 
 
 1329 
 
 166-1 
 
 300-2 
 
 119-2 
 
 149 
 
 271 
 
 1062 
 
 132-7 
 
 241-2 
 
 93 
 
 1162 
 
 3308 
 
 132-8 
 
 166 
 
 300 
 
 119-1 
 
 148 : 9 
 
 2705 
 
 106 
 
 1325 
 
 241 
 
 92-9 
 
 1161 
 
 330 
 
 132-4 
 
 165-5 
 
 2997 
 
 119 
 
 148-7 
 
 270 
 
 1057 
 
 132-2 
 
 2408 
 
 92-8 
 
 116 
 
216 
 
 
 THBRMOMETRICAL EQUIVALENTS. 
 
 Fahren- 
 heit. 
 
 1 
 
 II 
 
 Fahren- 
 heit. 
 
 Reaumur. 
 
 It 
 
 1* 
 
 Reaumur. 
 
 1! 
 
 o &> 
 
 Fahren- 
 heit. 
 
 Reaumur. 
 
 it 
 
 240 
 
 924 
 
 115-5 
 
 209-7 
 
 79 
 
 987 
 
 180 
 
 657 
 
 82-2 
 
 1508 
 
 52-8 
 
 66 
 
 239 
 
 92 
 
 115 
 
 209 
 
 78-6 
 
 983 
 
 1796 
 
 65-6 
 
 82 
 
 150 
 
 52-4 
 
 65-5 
 
 238 
 
 915 
 
 114-4 
 
 208-4 
 
 78-4 
 
 98-0 
 
 179 
 
 653 
 
 81-6 
 
 149 
 
 52 
 
 65 
 
 237-2 
 
 912 
 
 114 
 
 208 
 
 78-2 
 
 978 
 
 178-2 
 
 65 
 
 81-2 
 
 148 
 
 51-5 
 
 64-4 
 
 237 
 
 91 1 
 
 113-9 
 
 207-5 
 
 78 
 
 975 
 
 178 
 
 64-9 
 
 81-1 
 
 147-2 
 
 51-2 
 
 64 
 
 236-7 
 
 91 
 
 113-7 
 
 207 
 
 77-7 
 
 97 2 
 
 177-8 
 
 64-8 
 
 81 
 
 147 
 
 51-1 
 
 63-9 
 
 236 
 
 903 
 
 113-3, 
 
 206-6 
 
 77-6 
 
 97 
 
 177 
 
 64-4 
 
 80 5 
 
 146-7 
 
 51 
 
 63-7 
 
 235-4 
 
 90-4 
 
 113 
 
 206 
 
 77-3 
 
 96-6 
 
 176 
 
 64 
 
 80 
 
 146 
 
 506 
 
 63-3 
 
 235 
 
 902 
 
 112-7 
 
 205-2 
 
 77 
 
 96 2 
 
 175 
 
 63-5 
 
 79-4 
 
 145-4 
 
 50'4 
 
 63 
 
 234-5 
 
 90 
 
 112-5 
 
 205 
 
 76-9 
 
 96-1 
 
 174-2 
 
 632 
 
 79 
 
 145 
 
 50-2 
 
 62-7 
 
 234 
 
 89-7 
 
 1122 
 
 2048 
 
 768 
 
 96 
 
 174 
 
 63-1 
 
 788 
 
 144-5 
 
 50 
 
 62-5 
 
 2336 
 
 896 
 
 112 
 
 204 
 
 76-4 
 
 95 5 
 
 1737 
 
 63 
 
 78-7 
 
 144 
 
 497 
 
 622 
 
 233 
 
 89-3 
 
 111-6 
 
 203 
 
 76 
 
 95 
 
 173 
 
 62-6 
 
 78-3 
 
 143-6 
 
 496 
 
 62 
 
 2322 
 
 89 
 
 111-2 
 
 202 
 
 75-5 
 
 94-4 
 
 172-4 
 
 62-4 
 
 78 
 
 143 
 
 493 
 
 61-6 
 
 232 
 
 88-9 
 
 nri 
 
 201-2 
 
 75-2 
 
 94 
 
 172 
 
 62-2 
 
 77-7 
 
 142-2 
 
 49 
 
 61-2 
 
 2318 
 
 88-8 
 
 111 
 
 201 
 
 75-1 
 
 93-9 
 
 171-5 
 
 62 
 
 77-5 
 
 142 
 
 48-9 
 
 61-1 
 
 231 
 
 88-4 
 
 110-5 
 
 200-7 
 
 75 
 
 93-7 
 
 171 
 
 61-7 
 
 77-2 
 
 141-8 
 
 488 
 
 61 
 
 230 
 
 88 
 
 110 
 
 200 
 
 74-6 
 
 93-3 
 
 170-6 
 
 61-6 
 
 77 
 
 141 
 
 48-4 
 
 60-5 
 
 229 
 
 87-5 
 
 109-4 
 
 199-4 
 
 74-4 
 
 93 
 
 170 
 
 613 
 
 76-6 
 
 140 
 
 48 
 
 60 
 
 228-2 
 
 87-2 
 
 109 
 
 199 
 
 74-2 
 
 927 
 
 169 2 
 
 61 
 
 762 
 
 139 
 
 47 5 
 
 59-4 
 
 228 
 
 87-1 
 
 108-9 
 
 198-5 
 
 74 
 
 92-5 
 
 169 
 
 60-8 
 
 76-1 
 
 1382 
 
 47-2 
 
 59 
 
 2277 
 
 87 
 
 108-7 
 
 198 
 
 737 
 
 922 
 
 168-8 
 
 60-8 
 
 76 
 
 138 
 
 47-1 
 
 58-8 
 
 227 
 
 86-6 
 
 1083 
 
 197-6 
 
 73-6 
 
 92 
 
 168 
 
 604 
 
 75-5 
 
 137-7 
 
 47 
 
 58-7 
 
 2264 
 
 86-4 
 
 108 
 
 197 
 
 73-3 
 
 91 6 
 
 167 
 
 60 
 
 75 
 
 137 
 
 46-6 
 
 58-3 
 
 226 
 
 86-2 
 
 107-8 
 
 196-2 
 
 73 
 
 91-2 
 
 166 
 
 595 
 
 74-4 
 
 136-4 
 
 46-4 
 
 58 
 
 225-5 
 
 86 
 
 107-5 
 
 196 
 
 72-8 
 
 91-1 
 
 165-2 
 
 59-2 
 
 74 
 
 136 
 
 46-2 
 
 57-7 
 
 225 
 
 85-7 
 
 107-2 
 
 195-8 
 
 72-8 
 
 91 
 
 165 
 
 59-1 
 
 739 
 
 135-5 
 
 46 
 
 57-5 
 
 224-6 
 
 85-6 
 
 107 
 
 195 
 
 72-4 
 
 90-5 
 
 164-7 
 
 59 
 
 73-7 
 
 135 
 
 45-8 
 
 57-2 
 
 224 
 
 85-3 
 
 106-6 
 
 194 
 
 72 
 
 90 
 
 164 
 
 586 
 
 73-3 
 
 134-6 
 
 45 6 
 
 57 
 
 223-2 
 
 85 
 
 1062 
 
 193 
 
 71-5 
 
 89-4 
 
 163-4 
 
 58-4 
 
 73 
 
 134 
 
 45-3 
 
 56-6 
 
 223 
 
 84-9 
 
 106-1 
 
 192-2 
 
 71 2 
 
 89 
 
 163 
 
 58-2 
 
 72-7 
 
 133-2 
 
 45 
 
 56-2 
 
 2228 
 
 84-8 
 
 106 
 
 192 
 
 71-1 
 
 88-8 
 
 162 5 
 
 58 
 
 72-5 
 
 133 
 
 44-9 
 
 56-1 
 
 222 
 
 84-4 
 
 105-5 
 
 191-7 
 
 71 
 
 88-7 
 
 162 
 
 577 
 
 72-2 
 
 132-8 
 
 44-8 
 
 56 
 
 221 
 
 84 
 
 105 
 
 191 
 
 70-6 
 
 88 3 
 
 161 6 
 
 57-6 
 
 72 
 
 132 
 
 44-5 
 
 55-5 
 
 220 
 
 83-5 
 
 104-4 
 
 190-4 
 
 704 
 
 88 
 
 161 
 
 57-3 
 
 71-6 
 
 131 
 
 44 
 
 55 
 
 219-2 
 
 83-2 
 
 104 
 
 190 
 
 70-2 
 
 878 
 
 160-2 
 
 57 
 
 71-2 
 
 130 
 
 435 
 
 54-4 
 
 219 
 
 83 1 
 
 103 9 
 
 189-5 
 
 70 
 
 87 5 
 
 160 
 
 56-8 
 
 71-1 
 
 129-2 
 
 43-2 
 
 54 
 
 218-7 
 
 83 
 
 103-7 
 
 189 
 
 69-7 
 
 87-2 
 
 159-8 
 
 56-8 
 
 71 
 
 129 
 
 43-1 
 
 53-9 
 
 218 
 
 826 
 
 103-3 
 
 188-6 
 
 69-6 
 
 87 
 
 159 
 
 564 
 
 70-5 
 
 128-7 
 
 43 
 
 53-7 
 
 217-4 
 
 82-4 
 
 103 
 
 188 
 
 69-3 
 
 86-6 
 
 158 
 
 56 
 
 70 
 
 128 
 
 426 
 
 53-3 
 
 217 
 
 82-2 
 
 102-7 
 
 187-2 
 
 69 
 
 86-2 
 
 157 
 
 55-5 
 
 69-4 
 
 127-4 
 
 42-4 
 
 53 
 
 216-5 
 
 82 
 
 102-5 
 
 187 
 
 68-9 
 
 86-1 
 
 1562 
 
 55-2 
 
 69 
 
 127 
 
 422 
 
 52-7 
 
 216 
 
 8T7 
 
 102-2 
 
 1868 
 
 68-8 
 
 86 
 
 156 
 
 55 1 
 
 68-9 
 
 126-5 
 
 42 
 
 52-5 
 
 2156 
 
 81-6 
 
 102 
 
 186 
 
 68-4 
 
 85-5 
 
 155-7 
 
 55 
 
 68-7 
 
 126 
 
 41-8 
 
 522 
 
 215 
 
 81-3 
 
 1016 
 
 185 
 
 68 
 
 85 
 
 155 
 
 546 
 
 68-3 
 
 1256 
 
 41 6 
 
 52 
 
 214-2 
 
 81 
 
 10T2 
 
 184 
 
 67-5 
 
 84-4 
 
 154-4 
 
 544 
 
 68 
 
 125 
 
 41 3 
 
 51-6 
 
 214 
 
 80-9 
 
 101-1 
 
 183-2 
 
 67.2 
 
 84 
 
 154 
 
 54-2 
 
 67-7 
 
 1242 
 
 41 
 
 51-2 
 
 2138 
 
 80-8 
 
 101 
 
 183 
 
 67-1 
 
 839 
 
 153-5 
 
 54 
 
 67-5 
 
 124 
 
 40-9 
 
 51-1 
 
 213 
 
 80-4 
 
 100-5 
 
 182-7 
 
 67 
 
 83-7 
 
 153 
 
 53-7 
 
 67-2 
 
 1238 
 
 40-8 
 
 51 
 
 212 
 
 80 
 
 100 
 
 182 
 
 66-6 
 
 83-3 
 
 152-6 
 
 53-6 
 
 67 
 
 123 
 
 40-4 
 
 50-5 
 
 211 
 
 79-5 
 
 99-4 
 
 181-4 
 
 66-4 
 
 83 
 
 152 
 
 53-3 
 
 666 
 
 122 
 
 40 
 
 50 
 
 210-2 
 
 79-2 
 
 99 
 
 181 
 
 66-2 
 
 82-7 
 
 151.2 
 
 53 
 
 66-2 
 
 121 
 
 39-5 
 
 49-4 
 
 210 
 
 79-1 
 
 98-9 
 
 180-5 
 
 66 
 
 825 
 
 151 
 
 529 
 
 66-1 
 
 120-2 
 
 39-2 
 
 49 
 
THERMOMETRICAL EQUIVALENTS. 
 
 217 
 
 Reaumur. 
 
 ii 
 
 u & 
 
 Si 
 
 fa 
 
 Reaumur. 
 
 ll 
 
 k 
 jP 
 
 Reaumur; 
 
 ii 
 
 Fahren- 
 heit. 
 
 Reaumur. 
 
 i| 
 
 s 
 
 39-1 
 
 48-9 
 
 90-5 
 
 26 
 
 32-5 
 
 61 
 
 129 
 
 16 1 
 
 302 
 
 0-8 
 
 i 
 
 39 
 
 48-7 
 
 90 
 
 25-7 
 
 32-2 
 
 60-8 
 
 128 
 
 16 
 
 30 
 
 0-9 
 
 1-1 
 
 38-6 
 
 48-3 
 
 896 
 
 25-6 
 
 32 
 
 60 
 
 12-4 
 
 15-5 
 
 29-7 
 
 1 
 
 12 
 
 38-4 
 
 48 
 
 89 
 
 253 
 
 31 6 
 
 59 
 
 12 
 
 . 15 
 
 29 
 
 1-3 
 
 1-6 
 
 38-2 
 
 47-7 
 
 88-2 
 
 25 
 
 31-2 
 
 58 
 
 11-5 
 
 14-4 
 
 28-4 
 
 1-6 
 
 2 
 
 38 
 
 47-5 
 
 88 
 
 24-9 
 
 31-1 
 
 57-2 
 
 11-2 
 
 14 
 
 28 
 
 1-7 
 
 2-2 
 
 37-7 
 
 47-2 
 
 87-8 
 
 24-8 
 
 31 
 
 57 
 
 11-1 
 
 138 
 
 27-5 
 
 2 
 
 2-5 
 
 37 6 
 
 47 
 
 87 
 
 244 
 
 305 
 
 56-7 
 
 11 
 
 13-7 
 
 27 
 
 2-2 
 
 2-7 
 
 37-3 
 
 46-6 
 
 86 
 
 24 
 
 30 
 
 56 
 
 106 
 
 133 
 
 26-6 
 
 2-4 
 
 3 
 
 37 
 
 46-2 
 
 85 
 
 23-5 
 
 294 
 
 554 
 
 10-4 
 
 13 
 
 26 
 
 26 
 
 3-3 
 
 36-9 
 
 46-1 
 
 84-2 
 
 232 
 
 29 
 
 55 
 
 102 
 
 12'7 
 
 25-2 
 
 3 
 
 3-7 
 
 36-8 
 
 46 
 
 84 
 
 23-1 
 
 28-9 
 
 54-5 
 
 10 
 
 12-5 
 
 25 
 
 3-1 
 
 3-8 
 
 36'4 
 
 45-5 
 
 83-7 
 
 23 
 
 287 
 
 54 
 
 9-7 
 
 122 
 
 24-8 
 
 32 
 
 4 
 
 36 
 
 45 
 
 83 
 
 22-6 
 
 28-3 
 
 53-6 
 
 9-6 
 
 12 
 
 24 
 
 35 
 
 4-4 
 
 355 
 
 44-4 
 
 82-4 
 
 22-4 
 
 28 
 
 53 . 
 
 9-3 
 
 11-6 
 
 23 
 
 4 
 
 5 
 
 35-2 
 
 44 
 
 82 
 
 222 
 
 277 
 
 52-2 
 
 9 
 
 11-2 
 
 22 
 
 4-4 
 
 5-5 
 
 35-1 
 
 43-9 
 
 81-5 
 
 22 
 
 27 5 
 
 52 
 
 89 
 
 11-1 
 
 21-2 
 
 4-8 
 
 6 
 
 35 
 
 43-7 
 
 81 
 
 21-7 
 
 272 
 
 51-8 
 
 8-8 
 
 11 
 
 21 
 
 4-9 
 
 6-1 
 
 34-6 
 
 433 
 
 80-6 
 
 216 
 
 27 
 
 51 
 
 8-4 
 
 10-5 
 
 20-7 
 
 5 
 
 6'2 
 
 34-4 
 
 43 
 
 80 
 
 21-3 
 
 26-6 
 
 50 
 
 8 
 
 10 
 
 20 
 
 5-3 
 
 6-6 
 
 34-2 
 
 427 
 
 792 
 
 21 
 
 262 
 
 49 
 
 75 
 
 9-4 
 
 19-4 
 
 56 
 
 7 
 
 34 
 
 42-5 
 
 79 
 
 20-9 
 
 26-1 
 
 48-2 
 
 7-2 
 
 9 
 
 19 
 
 5-7 
 
 7-2 
 
 33-8 
 
 42-2 
 
 78-8 
 
 20-8 
 
 26 
 
 48 
 
 7-1 
 
 89 
 
 18-5 
 
 6 
 
 7-5 
 
 33-6 
 
 42 
 
 78 
 
 20-4 
 
 25-5 
 
 47-7 
 
 7 
 
 8-7 
 
 18 
 
 62 
 
 7-7 
 
 33-3 
 
 41 6 
 
 77 
 
 20 
 
 25 
 
 47 
 
 66 
 
 8-3 
 
 17-6 
 
 6-4 
 
 8 
 
 33 
 
 41-2 
 
 76 
 
 19-5 
 
 24-4 
 
 46-4 
 
 6-4 
 
 8 
 
 17 
 
 6-6 
 
 8-3 
 
 32-9 
 
 41-1 
 
 75-2 
 
 19-2 
 
 24 
 
 46 
 
 6-2 
 
 7-7 
 
 16-2 
 
 7 
 
 8-7 
 
 328 
 
 41 
 
 75 
 
 19-1 
 
 23-8 
 
 45-5 
 
 6 
 
 7-5 
 
 16 
 
 7-1 
 
 89 
 
 32'4 
 
 40-5 
 
 ? 74-7 
 
 19 
 
 23-7 
 
 45 
 
 57 
 
 7-2 
 
 158 
 
 7-2 
 
 9 
 
 32 
 
 40 
 
 74 
 
 18-6 
 
 233 
 
 44-6 
 
 57 
 
 7 
 
 15 
 
 75 
 
 94 
 
 31-5 
 
 39-4 
 
 73-4 
 
 18-4 
 
 23 
 
 44 
 
 53 
 
 66 
 
 14 
 
 8 
 
 10 
 
 31-2 
 
 39 
 
 73 
 
 18-2 
 
 22-7 
 
 43-2 
 
 5 
 
 62 
 
 13 
 
 8-4 
 
 10-5 
 
 3T1 
 
 38-9 
 
 72-5 
 
 18 
 
 22-5 
 
 43 
 
 4-9 
 
 6-1 
 
 12-2 
 
 8-8 
 
 11 
 
 31 
 
 38-7 
 
 72 
 
 17-7 
 
 22-2 
 
 428 
 
 4-8 
 
 6 
 
 12 
 
 8.9 
 
 11 1 
 
 30'6 
 
 38'3 
 
 71-6 
 
 176 
 
 22 
 
 42 
 
 4-4 
 
 5-5 
 
 11-7 
 
 9 
 
 11-2 
 
 30-4 
 
 38 
 
 71 
 
 17-3 
 
 216 
 
 41 
 
 4 
 
 5 
 
 11 
 
 9-3 
 
 11 6 
 
 30'2l 37-7 
 
 70-2 
 
 17 
 
 21-2 
 
 40 
 
 35 
 
 44 
 
 10-4 
 
 9-6 
 
 12 
 
 30 
 
 37-5 
 
 70 
 
 169 
 
 21-1 
 
 39-2 
 
 3-2 
 
 4 
 
 10 
 
 9-7 
 
 12-2 
 
 29-7 
 
 372 
 
 69-8 
 
 168 
 
 21 
 
 39 
 
 3-1 
 
 39 
 
 9-5 
 
 10 
 
 125 
 
 29-6 
 
 37 
 
 69 
 
 16-4 
 
 20-5 
 
 38-7 
 
 3 
 
 3-7 
 
 9 
 
 10-2 
 
 12-7 
 
 29 3 
 
 36-6 
 
 68 
 
 16 
 
 20 
 
 38 
 
 2-6 
 
 33 
 
 86 
 
 104 
 
 13 
 
 29 
 
 36-2 
 
 67 
 
 15'5 
 
 19-4 
 
 .37-4 
 
 2-4 
 
 3 
 
 8 
 
 10-6 
 
 133 
 
 28-9 
 
 36 1 
 
 66-2 
 
 15-2 
 
 19 
 
 37 
 
 2-2 
 
 '2-7 
 
 7-2 
 
 11 
 
 13-7 
 
 28-8 
 
 36 
 
 66 
 
 15-1 
 
 18-8 
 
 36-5 
 
 2 
 
 2-5 
 
 7 
 
 11-1 
 
 13-9 
 
 28-4 
 
 35-5 
 
 65-7 
 
 15 
 
 187 
 
 36 
 
 1-7 
 
 2-2 
 
 6-8 
 
 11-2 
 
 14 
 
 28 
 
 35 
 
 65 
 
 14-6 
 
 18-3 
 
 35-6 
 
 1-6 
 
 2 
 
 6 
 
 11-5 
 
 14-4 
 
 27-5 
 
 34-4 
 
 64-4 
 
 14-4 
 
 18 
 
 35 
 
 13 
 
 16 
 
 5 
 
 12 
 
 15 
 
 272 
 
 34 
 
 64 
 
 14-2 
 
 17-7 
 
 34-2 
 
 1 
 
 1-2 
 
 4 
 
 12-4 
 
 15-5 
 
 27-1 
 
 339 
 
 63 5 
 
 14 
 
 17-5 
 
 34 
 
 0-9 
 
 ri 
 
 32 
 
 128 
 
 16 
 
 27 
 
 337 
 
 63 
 
 13-7 
 
 17-2 
 
 33-8 
 
 0-8 
 
 1 
 
 3 
 
 12-9 
 
 161 
 
 26-6 
 
 333 
 
 62-6 
 
 136 
 
 17 
 
 33 
 
 0-4 
 
 0-5 
 
 2-7 
 
 13 
 
 16-2 
 
 26-4 
 
 33 
 
 62 
 
 13-3 
 
 166 
 
 32 
 
 
 
 
 
 2 
 
 133 
 
 16-6 
 
 26-2 
 
 327 
 
 6T2 
 
 13 
 
 16-2 
 
 31 
 
 0-4 
 
 0-5 
 
 1-4 
 
 13-6 
 
 17 
 
218 
 
 SOURCES AND MANAGEMENT OF HEAT. 
 
 Fahren- 
 heit. 
 
 Reaumur. 
 
 .i 
 
 11 
 
 O ti) 
 
 a . 
 
 " ~ 
 
 i j 
 
 Reaumur. 
 
 1! 
 
 O SD 
 
 Fahren- 
 heit. 
 
 Reaumur. 
 
 11 
 
 O bo 
 
 d . 
 
 J= "*> 
 T 
 
 Reaumur. 
 
 3j 
 
 SI 
 
 1 
 
 13-7 
 
 17-2 
 
 9-4 
 
 18-4 
 
 23 
 
 20 
 
 23-1 
 
 28-9 
 
 30 
 
 27-5 
 
 344 
 
 05 
 
 14 
 
 17-5 
 
 10 
 
 18-6 
 
 23-3 
 
 20-2 
 
 232 
 
 29 
 
 31 
 
 28 
 
 35 
 
 
 
 14-2 
 
 17-7 
 
 10-7 
 
 19 
 
 23-7 
 
 21 
 
 23-5 
 
 29-4 
 
 32 
 
 28-4 
 
 -35-5 
 
 0-4 
 
 14-4 
 
 18 
 
 11 
 
 -19-1 
 
 23-8 
 
 22 
 
 24 
 
 30 
 
 32-8 
 
 28-8 
 
 36 
 
 1 
 
 146 
 
 18-3 
 
 11-2 
 
 19-2 
 
 24 
 
 23 
 
 24-4 
 
 30-5 
 
 33 
 
 28-9 
 
 36-1 
 
 1-7 
 
 15 
 
 18-7 
 
 12 
 
 195 
 
 24-4 
 
 23-8 
 
 248 
 
 31 
 
 33-2 
 
 29 
 
 36-2 
 
 2 
 
 15 1 
 
 18-9 
 
 13 
 
 20 
 
 25 
 
 24 
 
 24-9 
 
 31-1 
 
 34 
 
 29-3 
 
 366 
 
 2-2 
 
 15-2 
 
 19 
 
 14 
 
 20-4 
 
 25-5 
 
 24-2 
 
 25 
 
 31-2 
 
 34-6 
 
 29-6 
 
 37 
 
 3 
 
 155 
 
 194 
 
 14-8 
 
 208 
 
 26 
 
 25 
 
 253 
 
 31-6 
 
 35 
 
 29-7 
 
 37-2 
 
 4 
 
 16 
 
 20 
 
 15 
 
 209 
 
 261 
 
 256 
 
 256 
 
 32 
 
 355 
 
 30 
 
 37-5 
 
 5 
 
 164 
 
 205 
 
 15-2 
 
 21 
 
 -26-2 
 
 26 
 
 25-7 
 
 322 
 
 36 
 
 302 
 
 37-7 
 
 5-8 
 
 16-8 
 
 21 
 
 16 
 
 21-3 
 
 26-6 
 
 26-5 
 
 26 
 
 32-5 
 
 36-4 
 
 30-4 
 
 38 
 
 6 
 
 168 
 
 21 1 
 
 16-6 
 
 21-6 
 
 27 
 
 27 
 
 262 
 
 32-7 
 
 37 
 
 30-6 
 
 38'3 
 
 6-2 
 
 17 
 
 21-2 
 
 17 
 
 21-7 
 
 27-2 
 
 274 
 
 26-4 
 
 33 
 
 37-7 
 
 31 
 
 38-7 
 
 7 
 
 17-3 
 
 21-6 
 
 17-5 
 
 22 
 
 27-5 
 
 28 
 
 266 
 
 33-3 
 
 38 
 
 31-1 
 
 38-9 
 
 7-6 
 
 17-6 
 
 22 
 
 18 
 
 22-2 
 
 27-7 
 
 28-7 
 
 27 
 
 33-7 
 
 38-2 
 
 31-2 
 
 39 
 
 8 
 
 17-7 
 
 22-2 
 
 184 
 
 22-4 
 
 28 
 
 29 
 
 -27-1 
 
 338 
 
 39 
 
 31 5 
 
 39-4 
 
 8-5 
 
 18 
 
 22-5 
 
 19 
 
 226 
 
 28-3 
 
 29-2 
 
 27-2 
 
 34 
 
 40 
 
 32 
 
 40 
 
 9 
 
 182 
 
 22-7 
 
 19-7 
 
 23 
 
 28-7 
 
 
 
 
 
 
 
 CHAPTER XL 
 
 SOURCES AND MANAGEMENT OP HEAT. 
 
 HEAT plays an important part in changing the state and pro- 
 perties of bodies, and we, therefore, devote a chapter to the 
 various modes of applying that agent in chemical operations. 
 The processes dependent upon its action are, principally, FUSION, 
 IGNITION, CALCINATION, INCINERATION, ROASTING, DEFLAGRA- 
 TION, REDUCTION, CUPELLATION, SUBLIMATION, DISTILLATION, 
 DIGESTION, DECOCTION, BOILING, SOLUTION, EVAPORATION, 
 CRYSTALLIZATION, and DESICCATION. 
 
 FURNACES. Laboratory furnaces differ in construction accord- 
 ing to the uses for which they are designed. The main parts of 
 every furnace are the body in which the heat is produced, the 
 grate or bars upon which the fuel rests, the ash pan for receiving 
 the residue, and smoke-pipe for conducting off the gaseous pro- 
 ducts of combustion. 
 
 Most laboratories at the present day have a stationary wind or 
 
FURNACES. 
 
 219 
 
 air furnace set in brickwork. Being applicable only for crucible 
 operations, its usefulness is limited. In private experimental 
 laboratories, the gas sand-bath, explained at p. 66, and one of 
 the portable furnaces about to be mentioned, would be far more 
 efficient and convenient. The object should be to select such an 
 arrangement as will admit of the greatest extent of application, 
 and, therefore, a public institution with the jack, Fig. 14, will 
 only need, besides, a Barren's table, a small charcoal furnace, and 
 the usual gas lamps, to be amply provided for the accomplish- 
 ment of any furnace experiments. Still, for the sake of giving 
 completeness to our work, we proceed to describe the common 
 form of a, 
 
 Wind Furnace. This is a close furnace, in which the draught 
 of the chimney urges the fire, instead of a bellows, as in blast 
 furnaces. Fig. 123 shows a vertical section. The body A, may 
 
 Fig. 123. 
 
 have its interior square or circular, though the latter form is 
 most convenient and economical for fuel, and should abut against 
 a high chimney. The ash-pit B is separated from the body of 
 the furnace by movable, cast-iron, bars, which form a support for 
 
220 
 
 FURNACES. 
 
 Fig. 124. 
 
 the fire-brick on which the crucibles rest, as well as for the coal 
 used in heating them. The lateral flue, connecting with the 
 chimney C, should be short and contracted at the throat, so as 
 to promote the perfect combustion of the gases before they pass 
 off, and thus economize heat as well as increase the draught. It 
 must also be fitted with a damper. All the interior of the fur- 
 nace must be lined with tile or brick made of refractory clay ; 
 and the ash-pit should have tubes leading from the outside of the 
 apartment, for supplying currents of air to the burning fire, and 
 augmenting the heat. The mouth of the furnace, which is the 
 opening for the introduction of fuel and the crucibles, may be a 
 sliding door of cast-iron, lined internally with a soap-stone slab, 
 as a protection against the fire, as shown at 
 a, or it may be hung to the chimney wall by 
 chains working on pulleys, so as to move ver- 
 tically instead of horizontally. An opening 
 in the centre, fitted with a soap-stone plug, 
 serves for observing the progress of the ope- 
 ration as may be desirable. The cast-iron 
 hood D, over the furnace, is to avert the pro- 
 gress of uprising sparks, dust, &c., and carry 
 them off, through a valve, into the chimney. The dimensions of 
 the pot may be 10-12 inches diameter, and 20-24 inches height 
 
 from the grate-bars up- 
 
 Fig.125. Fig. 126. wardg< The grate . barg 
 
 should be set three-fourth 
 inches apart ; and the 
 chimney-flue should run 
 to a height of about 30 
 feet. 
 
 It is useless to multiply 
 furnaces in a small labo- 
 ratory, for they occupy 
 room which may be want- 
 ing for other purposes, and, therefore, a selection should be made 
 of one which in its arrangement is applicable to all the necessities 
 of the chemist. One of either, with a small charcoal furnace, 
 Fig. 124, such as may be bought at any crockery shop, for table 
 use, will comprise all that is required of this sort of apparatus. 
 
LUHME'S UNIVERSAL FURNACE. 
 
 221 
 
 Universal Furnace. Figs. 125, 126, exhibit this furnace, the 
 cylindrical form of which is to be preferred on account of its 
 producing a higher heat with less fuel than any other. It is of 
 strong plate-iron, and lined in the body and dome with refractory 
 fire-clay. Its dimensions are twenty-four inches in height, and 
 nine inches in diameter. The body, , >, e, d, is capped with a 
 ring of the same circumference as the clay cylinder beneath. 
 The doors are shown at g and h. The circular openings, #, x, 
 opposite to each other, are for the passage of tubes, and when 
 out of use can be closed by the plugs accompanying the furnace 
 for that purpose. The interior of the furnace, as seen from above, 
 is shown by Fig. 127. The knobs, e, e, e, projecting inwardly, 
 serve as supports for vessels which are smaller than the mouth of 
 
 Fig. 127. 
 
 Fig. 128. 
 
 Fig. 129. 
 
 the furnace, whilst the iron juts, d, d, c?, directed outwardly, are 
 rests for the larger,* this arrangement being necessary, in both in- 
 stances, to the perfection of the draught. The iron jacket, Fig. 
 128, adapted to the opening, a d, Fig. 125, forms a support for 
 
 Fig. 130. 
 
 Fig. 131. 
 
 the double sand-bath, Fig. 129, for retorts, and other glass 
 vessels. The slope on the side of the sand-bath is for the exit of 
 
222 
 
 KENT S UNIVERSAL FURNACE. 
 
 the neck of the retort ; and the circular openings, k, k, 7c, &, Fig. 
 130, are fitted with covers, by which to augment or decrease the 
 draught, as may be required. 
 
 A supplementary sand-bath, Fig. 131, is made with a broad 
 extent of surface for digestions, evaporations, &c. 
 
 The dome, Fig. 132, confers the powers of a wind furnace 
 when high heat is required. As this chimney becomes too hot to 
 be handled, it is removed when heated with suitable tongs, the 
 form of which is shown in Fig. 133. 
 
 Kent's universal furnace, which is an improvement upon the 
 above, is shown by Fig. 134. The body is fourteen inches high, 
 by seven inches in diameter, and in material and general con- 
 struction is similar to the one just described. There are six 
 doors : one at the base for the admission of air, another in the 
 middle for the entrance of the fuel and for the reception of the 
 muffle used in cupellation. The door in the dome is for the pur- 
 pose of feeding the fire in crucible operations ; and that in the 
 
 Fig. 132. 
 
 Fig. 134. 
 
 Fig. 133. 
 
 side, at the top, for the reception of the neck of a retort, or of a 
 sand-bath. There are two lateral openings, opposite to each 
 
EVAPORATING AND REVERBERATORY FURNACES. 223 
 
 other, for the passage of tubes, or of an iron bar as a support to 
 the rear end of a muffle. 
 
 The two circular openings, by which it is coupled with the pipes 
 connecting it with the laboratory flue, are closed by movable 
 plugs. In crucible operations, the smoke-pipe should lead from 
 the top opening, and in evaporations, from the aperture in the 
 back. The openings in the flue must be above the level of the 
 furnace. 
 
 An opening at the base is for the introduction of the mouth of 
 a bellows, by which it may be converted into a blast furnace. 
 This implement may be used in the following manner : 
 
 1. As an evaporating and calcining furnace. As very high 
 heat is seldom required for evaporations, the body of the furnace 
 alone answers every purpose. For small operations, or when but 
 a small fire is required, its capacity may be diminished by in- 
 serting an inner cylinder of baked clay. To increase the 
 draught, all the doors should be closed, and to augment still 
 further the heat, as is necessary in the calcination of certain sub- 
 stances, the dome and chimney may be used. In this latter case, 
 by means of the door in the middle, the progress of the operation 
 may be examined without removing the chimney dome, or cooling 
 the interior of the furnace. 
 
 The sand and other baths, which have their places upon the 
 top of this furnace; serve for digestions, evaporations, &c., in 
 vessels which require the abatement and equalization of the heat 
 by intermedia. 
 
 2. As a reverberator^/ furnace. This kind of furnace is 
 adapted to operations demanding a high temperature, as in the 
 heating of crucibles, tubes, &c., and also in sublimation and simi- 
 lar processes requiring the application of a steady heat to all 
 portions of the vessel, rather than a very great heat to any one 
 part of it. 
 
 The furnace is rendered reverberatory by the use of the dome, 
 which allows the vessel to be entirely surrounded by flame, and 
 reflects back the heat upon and around its whole surface, and 
 thus by equalizing the temperature, prevents the condensation of 
 vapors in the upper parts, an important object in distilling from 
 beaked vessels. 
 
 Coke or charcoal is the fuel generally used, the latter being pre- 
 
224 WIND AND BLAST FURNACES. 
 
 ferable for a furnace of small dimensions ; and the draught may 
 be increased by lengthening the chimney. 
 
 The crucible, or vessel, must be placed in the centre, supported 
 upon half of a fire-brick, in such a situation that the cold air 
 ascending through the grate may not prevent the heating of its 
 bottom. The fire is then kindled and maintained by fresh sup- 
 plies of fuel, which are added carefully so that they may not, 
 whilst cold, come in contact with the hot vessel and occasion its 
 fracture. 
 
 3. As a wind furnace. Wind furnaces are used for the 
 vitrification of mixtures, reduction and fusion of metals, and 
 for other operations requiring a prolonged elevation of tempera- 
 ture. 
 
 The combustion is urged by the draught of a flue, and the 
 degree of heat within the furnace depends upon the size and 
 height of the chimney into which the flue passes. The intensity 
 of the heat is increased by so proportioning the dimensions of the 
 furnace and the chimney that their diameters are equal, and 
 the height of the latter twenty to thirty times the diameter of 
 the former. 
 
 The furnace may be converted into a wind furnace by putting 
 on the dome, closing all the openings, and giving a free access 
 of air to the grating through a pipe attached to the circular 
 nozzle in the hearth space, and leading into one of the flues of 
 the laboratory chimney. The smoke-pipe may lead into the 
 same flue, and both should be fitted with dampers for the regula- 
 tion of the draught. 
 
 4. As a blastfurnace. Blast furnaces are serviceable for ex- 
 peditiously producing a great intensity of heat, and are used for 
 fusions and other operations which require more power than that 
 of the wind furnace. 
 
 The combustion is urged by a current of air forced through a 
 pair of double bellows, the nozzle of which leads into the circular 
 opening near the base of either of the aforenamed furnaces. The 
 connection should be tightly adjusted with LUTE, so as to prevent 
 any escape of air. The arrangement otherwise is exactly the 
 same as for the wind furnace. 
 
 In blowing the blast, let the stream of air entering the furnace 
 be small at first, and be gradually increased as the temperature 
 
ASSAY OR CUPEL FURNACE. ^ 225 
 
 becomes higher. The maximum heat can be hastened by weight- 
 ing down the bellows, and thus augmenting the force of the 
 blast. 
 
 Sefstrom's (Berzelius, vol. 8), and Aikin's (Faraday, p. 95), 
 blast furnaces are said to give heat sufficient to melt felspar. 
 
 The blast may be furnished to the preceding furnaces from the 
 pneumatic table, Fig. 45, through a flexible leaden pipe, connected 
 at either end by means of coupling-screws. As the lead pipe 
 might be softened by a too great proximity to the heated fur- 
 nace, the opening in the ash pit of the latter to which the former 
 is to be attached, should be fitted with about two feet of iron gas 
 pipe, so as to prevent direct contact. 
 
 5. As an assay or cupel furnace. The same arrangement 
 which is directed for a reverberatory 
 will convert it into a cupel furnace; the Fig. 135. 
 
 only additional requisite being a muffle, /*+ 
 Fig. 135, for the reception of the cupels ( 
 in assaying operations. 
 
 A very convenient and more efficient furnace for CUPELLATION 
 is shown by Figs. 136, 137. 
 
 It is made of refractory fire clay, and hooped with strong iron 
 bands fastened together by screws, in order that it may better 
 withstand the high temperature to which it is subjected. 
 
 A, A', is the ash-pan, of diameter sufficient for the reception of 
 the body of the furnace B B'. The door c, is for the exit of the 
 cinders, and the ingress of the air. The larger opening D', in the 
 body of the furnace, is for the introduction of the muffle, and a 
 corresponding one D, opposite, for a prism-shaped support of 
 baked clay for maintaining the muffle in a horizontal position. 
 The mouth-piece, supported by a small platform, affords the 
 facility of admitting or preventing the access of air to the inte- 
 rior of the muffle. 
 
 There are other openings throughout the circumference of the 
 body immediately above the grate, for increasing the draught 
 when necessary. 
 
 In the part of the dome E is a door for the introduction of the 
 fuel. The two openings e e are for the introduction of a poker to 
 arrange the fire. 
 
 15 
 
226 
 
 BARRON S FURNACE. 
 
 At the top of the furnace is a dome G G, to which is adapted a 
 sheet-iron pipe for increasing the draught. 
 
 Fig. 136. 
 
 Fig. 137. 
 
 A sliding door H, and a small circular gallery i i, as a sup- 
 port for heated coals, afford additional means of increasing the 
 draught. 
 
 Barrens Furnace. By far the most convenient and generally 
 useful furnace is that known as Barron's Wind-Chest Table and 
 Blowpipe, a portable apparatus of simple construction. It is not 
 only readily manageable, and economical as to fuel, but works 
 with great efficiency, being applicable for all the purposes of 
 melting, fluxing, forging, annealing, and dry assaying. 
 
 It consists of a table with a cast-iron top, beneath which are a 
 wind-chest and bellows, as shown by Plate 3. Rising from the 
 wind-chest and protruding through the top of the table are mov- 
 able blow-pipe jets, which convey the blast to the furnaces, of 
 which there are four sizes, the smaller being capable of melting 
 4 to 8 ounces of gold, and the larger fifty times that weight. 
 

 
 
 - : 
 
 

LIEBIG S FURNACE. 
 
 227 
 
 The crucibles to be heated are placed in the furnace in the usual 
 manner, and the furnace itself is placed on the table top, which 
 forms a convenient support, so that its air-tubes at the base will 
 be immediately in front of the nozzle of the blow-pipe. The 
 bellows is worked by a treadle, which is adjusted so as to produce 
 a steady and easily controllable blast. Melting operations re- 
 quire from 5 to 20 minutes, according to the quantity of material 
 under process. The arrangement of the furnace for assaying, 
 annealing, or forging, is after the usual manner. By substituting 
 an oil or grease lamp for the furnace, the apparatus becomes a 
 powerful soldering blow-pipe. 
 
 Liebig's Furnace for Organic Analysis. This is a small sheet- 
 iron furnace, with movable partitions and screen, in which the 
 
 Fig. 138. 
 
 combustion of organic bodies is effected by a charcoal fire. Fig. 
 138 shows its interior. Fig. 139 gives a side view of the furnace, 
 
 Fig. 139. 
 
 Fig. 140. Fig. 141. 
 
 containing a combustion-tube under process connected with orga- 
 nic analysis. It is twenty-four inches in length, three inches in 
 height, and three inches in width at the bottom, diverging to four 
 inches at the top. The combustion-tube a passes through a circu- 
 lar opening in the closed end of the furnace, 
 and rests upon sheet-iron supports, Fig. 
 140. The grate consists of a series of slits 
 at the bottom of the furnace, which are 
 distant from each other about half an inch. 
 The sheet-iron screens, Fig. 141, are used to confine the fire to 
 certain parts of the tube. 
 
 W 
 
228 MANAGEMENT OF FURNACES. 
 
 The furnace is used upon the table, and should rest upon a 
 stone of length nearly equal to its own. 
 
 Management of Furnaces. All furnace operations should be 
 conducted under a stationary hood, so that the carbonic acid and 
 other noxious exhalations may have an escape from the labora- 
 tory, and the sparks and heated air emitted, be prevented from 
 endangering the comfort and safety of the apartment. 
 
 If the furnace is without feet, it should rest upon a stone block, 
 and never directly upon the floor or the top of the table, for its 
 heated bottom may occasion a conflagration. 
 
 Coal, coke, and charcoal are the fuel most used. Coal is the 
 least available, for it contains sulphur, and yields a large amount 
 of ash and clinker, which choke the grating, and it should never, 
 therefore, be used in the blast furnace. 
 
 Coke and charcoal, separately and combined, are used for all 
 the furnace operations, the former being preferable for assays at 
 a high temperature. Weight for weight, their amount of heat is 
 nearly equal, but the greater density of the coke enables it to 
 give more, bulk for bulk, by ten per cent. Charcoal ignites most 
 readily, but coke is more durable. Moreover, when of good 
 quality and free from sulphurous and earthy matter, it gives but 
 little ash or clinker. By mixing the two together, the good 
 qualities of both are obtained ; but charcoal alone is preferable for 
 heating glass and porcelain vessels. Before using the coke or 
 charcoal, care must be taken that it has been freed from dust and 
 dirt by sieving, and that the pieces are about the size of a walnut, 
 so that they may pack away neither too loosely nor too compactly. 
 All of the fuel should be kept in a dry place, for the vapor 
 arising from wet coal and condensing upon the surface of fra- 
 gile vessels which are being heated, will be apt to cause their 
 fracture. 
 
 The crucibles should be placed in the centre of the furnace, 
 upon a support, which may be a piece of 
 
 Fig. 142. Fig. 143. / - . ] . *2 V 
 
 fire-brick or a cast-iron trivet, as shown 
 by Fig. 142. This support answers also 
 for stone-ware retorts ; but a preferable 
 form for this purpose is the crow's-foot, 
 Fig. 143. The size of these latter imple- 
 ments is regulated by the proportions of the vessels which they 
 support. 
 
THE FURNITURE OF FURNACES. 
 
 229 
 
 .Fig. 144. 
 
 For supporting basins and flasks over the evaporating furnace, 
 an iron trellis of strong wire, Fig. 144, 
 is necessary. A series of these iron 
 trellises, of different sized meshes, will be 
 found convenient for adapting the heat 
 to glass vessels, tubes, &c. 
 
 In placing the vessels in the fire or in 
 the sand-bath, they must be made to 
 stand firmly, and as near to the centre as 
 possible, so that they may be equally 
 heated all around. To prevent damage 
 to them by a too sudden rise of temperature, the fire must be 
 urged gradually, and when the operations are finished, they 
 should be left to cool with the furnace, or, if taken out, be trans- 
 ferred to a cool sand-bath, so that their refrigeration may not be 
 so sudden as to cause fracture. 
 
 When the vessel, to be heated over the naked fire, is of less 
 diameter than the mouth of the furnace, this latter may be pro- 
 portionably lessened by means of a suitably adapted flat iron ring. 
 These rings, Figs. 145, 146, are also useful when it is required to 
 
 Fig. 145. 
 
 Fig. 146. 
 
 concentrate the heat of the furnace in the centre of the vessel, 
 and therefore it is advisable to have a series of them, the centre 
 openings of which should decrease gradually so as to render them 
 convenient for all sized vessels. , . 
 
 Before commencing operations the furnace must be entirely 
 freed from ashes and 
 clinker, and the coal 
 placed around the ves- 
 sel in layers. When a 
 fresh supply of fuel is 
 requisite, it may be 
 added through the door- 
 
230 
 
 LAMPS. 
 
 14b - 
 
 way made for the pur- 
 pose. The auxiliary ap- 
 paratus of a furnace, 
 other than that already 
 mentioned, are an ordi- 
 nary iron poker for clearing the grate ; and several pairs of tongs. 
 One of these latter, for adding lumps of coal to the fire, should 
 have the form shown by Fig. 147. Those for managing the 
 crucible in the furnace and for removing it whilst hot, may be 
 of either of the patterns presented by Figs. 148, 149. 
 
 Fig. 149. 
 
 LAMPS. Lamps are convenient and economical substitutes for 
 furnaces in table operations. Being less cumbersome and more 
 cleanly than the latter, they are readily manageable and always 
 ready for use ; and they also afford the means of more rapidly 
 multiplying results. 
 
 The amount of heat to be obtained by these instruments de- 
 pends upon their size and arrangement. A properly constructed 
 lamp may be made subservient to all the requirements of the 
 nicer heating operations of the laboratory, from gentle digestion 
 or evaporation to those processes which require a very high de- 
 gree of heat. 
 
 The heating power of the flame is most active immediately be- 
 neath its summit, and the vessel should be gradually brought 
 into direct contact with that portion. The vessel should be 
 heated more gradually in proportion to the thickness. When 
 thick glass or porcelain or other fragile bad-conducting material 
 is suddenly heated, the heated part expands while the rest does 
 not, and this unequal tension of two adjacent parts causes the 
 cracking or fracture of the vessel. There is, therefore, a great 
 advantage in employing glass or porcelain vessels of thin struc- 
 ture, for the heat being rapidly conducted through them, the lia- 
 bility of fracture is diminished. As strength is, however, often 
 required and thicker vessels must be used, the above principles 
 
LAMPS. 231 
 
 of expansion and conduction must be remembered when they are 
 employed. 
 
 In order to apply a small fire to a large surface, the heat may 
 be diffused by setting the vessel in a SAND or WATER BATH, or, 
 which is convenient and more cleanly, a plate of sheet metal or 
 wire gauze may be placed between the vessel and the fire. It is 
 safer not to allow the vessel to touch the plate or gauze. Iron 
 or brass gauze may be used, although fine copper gauze is pre- 
 ferable, because more durable. 
 
 The combustible or fuel most commonly used in chemical lamps 
 is alcohol, though pyroxylic spirit and lamp oil are occasionally 
 employed. 
 
 Alcohol flame gives no smoke or unpleasant odor, the product 
 of combustion being only carbonic acid and water ; while lamp 
 oil, especially where the supply of oil to the wick is insufficient, 
 produces a black carbonaceous deposit upon the bottom of the 
 vessel which occasions a loss of heat by radiation. 
 
 The alcohol flame moreover does not have the same injurious 
 effect upon bodies in contact with it as the oil flame with its sooty 
 deposit; nor does it hide from view the contents of test-tubes, 
 retorts, and other vessels, by blackening the glass. 
 
 A strong heart may be obtained from alcohol, but in tedious 
 processes, which require a long-continued uniformity of tempera- 
 ture, the lest lamp oil, or better, olive oil, should be used, such, for 
 example, as experiments with the mouth blow-pipe. 
 
 Pyroxylic spirit is much less objectionable than lamp oil, and, 
 according to Bolley, nine-fourteenths cheaper than alcohol in 
 heating capacity. The many other advantages of the latter, 
 however, give it the preference over all other combustibles as fuel 
 for chemical lamps. It should be of about the sp. gr. of 0-85. 
 Lamps burning, should always be extinguished before having the 
 supply of fuel renewed, so as to prevent liability of explosion. 
 The spirit is then gradually introduced from the tubed bottle, 
 Fig. 55, p. 83, until the reservoir is nearly full. This mode pre- 
 vents its running out, and diminishes the risk of overflow from 
 too large a stream. When the lamp is not in use, the wick should 
 always be covered with the extinguisher to prevent loss by evapo- 
 ration. 
 
232 
 
 GLASS SPIRIT LAMP. 
 
 Fig. 151. 
 
 The tongs accompanying these lamps are a pair of 
 surgeon's forceps, of such a form as shown by Fig. 
 150. As they are liable to become oxidized by con- 
 stant exposure, it is better to have their prongs 
 plated with platinum. This precaution lessens the 
 liability of debasing the contents of crucibles with 
 iron oxide which may become detached when they are 
 handled with rusty tongs. 
 
 We proceed to speak of such lamps as are suitable to labora- 
 tory purposes. 
 
 Glass, Spirit, Lamp. This is a small glass lamp, like the 
 one shown in Fig. 151. The body is the 
 reservoir for the alcohol. To the neck 
 b is adjusted a copper circular shield c, 
 with a tube in its centre for the passage 
 of the wick, which should be of cotton, 
 and similar to that used for tallow 
 candles. The shield should rest upon, 
 rather than within the neck, otherwise 
 its expansion by the heat may cause the 
 breakage of the glass. A minute opening drilled in the shield is 
 also requisite for the escape of vapor in case the alcohol should 
 become heated. The glass cap a, ground interiorly, so as to fit 
 hermetically to the neck of the lamp when not in use, prevents 
 the evaporation of the alcohol, and the consequent impregnation 
 of the wick with water, which renders its relighting difficult. 
 
 Fig. 152. 
 
 Fig. 153. 
 
 The lamp must, however, be invariably extinguished before 
 putting on the cap. 
 
 These lamps are useful for heating small apparatus, such as 
 
BERZELIUS'S LAMP. 
 
 233 
 
 test-tubes, Figs. 152, 153, and reduction-tubes, and for larger 
 vessels which require only a gentle heat, as shown in Fig. 154. 
 They are generally supplied with spirit through the mouth occu- 
 
 Fig. 104. 
 
 pied by the wick-holder. A much safer and more convenient 
 mode would be to pour it through a channel in the shoulder ; and 
 lamps are now being made with this provision, as shown in the 
 drawing which illustrates Bunsen's mode of igniting filters. The 
 heating power of the lamp may be greatly augmented by the 
 use of a small conical chimney, made of sheet-mica or copper. It 
 may rest upon the shoulder of the lamp ; but to permit access of 
 air must be perforated at the base with large holes, or else raised 
 on feet. 
 
 Berzeliuss Lamp. Fig. 40 at page 64 represents this lamp 
 with the improvements recommended by Mitscherlich and Liebig. 
 It should be made of thick sheet copper or brass, and brazed 
 instead of being soldered together. Its form is that of an Argand 
 lamp, with a circular body or reservoir^, Fig. 155, which receives 
 its fuel through the stoppered opening r. The mechanism con- 
 tained in the framework s, and communicating with the cylinder 
 , allows the elevation or depression of the wick at will. The only 
 communication between this portion of the lamp and the reser- 
 voir is by a small tube through which the alcohol is supplied to 
 the wick. The chimney u may be movable and adapted to a 
 
234 
 
 CRUCIBLE JACKET. 
 
 flattened socket soldered to the side of the inner circumference 
 of the reservoir, or else be hinged in the same position, so that it 
 
 Fig. 156. 
 
 may be thrown back when the lamp is to be lighted or trimmed. 
 Surmounting the chimney is a crucible jacket h with a handle q 
 adapted to the socket or thumb-screw. The crucible, with its 
 movable cover d, Fig. 156, is placed in the centre of the sheet- 
 iron jacket, upon supports, so as to receive 
 the full force of the flame. It is designed 
 to protect the crucible from all air save 
 that which passes up the chimney. The 
 whole arrangement is shown by Fig. 156, 
 c being the chimney of the spirit lamp, 
 and the arrows showing the direction of 
 the flanre, which passes unobstructed up- 
 ward. All atmospheric air save that 
 which passes up the chimney being ex- 
 cluded, the heating power of the lamp is 
 greatly increased. 
 The lamp, as seen by the figures, is mounted upon a fork t, 
 
LAMP SUPPORT. 
 
 235 
 
 which slides upon the upright of the support b. This upright is 
 a smooth wrought-iron or brass rod, screw cut at its lower end, 
 and firmly fastened to the walnut foot b by means of a nut. The 
 foot serves as a ballast, and at the same time as a bed for a large 
 capsule, which is a convenient receptacle for any matter which 
 may be accidentally spilled from the heating vessel. The pan p 
 is intended for the same purpose when the support is occupied on 
 either side. There are other appliances which add to the conve- 
 nience of this lamp. They consist of thumb-screws and sockets 
 d ef for holding the iron wire rings m I i k. These rings, vary- 
 ing in diameter, serve as supports for the vessels employed, and 
 to steady those which are tall, like the flask shown in the figure, 
 a clamp / is requisite. The thumb-screw, to which the rings are 
 attached, slide upon the upright rod, and allow the elevation or 
 depression of the heating vessel at will. The iron plate sand- 
 bath n is very useful for digestions in beaker glasses, which will 
 not safely bear direct contact with the flame. 
 
 The fittings of this and all other chemical lamps should com- 
 bine lightness with strength, so as to avoid the dissipation of too 
 much heat by excess of metal. 
 
 Fig. 157 exhibits a lamp support not very dissimilar to the 
 preceding, buf with a cast-iron triangular foot 6, of weight suffi- 
 cient to prevent the lamp from being upset by the superposition 
 of heavy vessels. The iron triangle d is a 
 very convenient substitute for the ring when 
 a crucible is to be heated, as that shape aifords 
 a better support. The rod a of brass or 
 iron is from twenty to twenty-four inches in 
 length. The fork g for the lamp, and the 
 rings, are all adapted to the thumb-screws 
 which hold them steadily until they are to be 
 replaced by others of different form or size 
 for different and larger vessels. 
 
 A very convenient modification of Berze- 
 lius's lamp for boiling in large vessels is shown 
 by Fig. 158. It is supported by three feet 
 of solid brass. Adjusted to its wooden handle 
 is a brass crook for supporting the necks of 
 beaked vessels, retorts, and the like. This crook can be lowered 
 
 Fig. 157. 
 
236 
 
 LUHME'S LAMP. 
 
 or elevated at will by means of the thumb-screw by which it is 
 fastened. Two rings accompany it, one, of open work, for the 
 support of capsules, broad and round bottomed vessels ; and the 
 
 other calendered with fine holes, for the distribution of the heat 
 
 to flat-bottomed glass vessels. 
 
 This is a powerful lamp, and is more convenient for large vessels 
 than the lamp mounted as before de- 
 scribed. Luhme", who first recommended 
 this form, also advises that there be no 
 direct communication between the re- 
 servoir and the circular space containing 
 the wick, because such an arrangement is 
 prornotive of accidents. When the lamp 
 has burned for a length of time and 
 nearly all the alcohol is consumed, the 
 reservoir becomes filled with vaporized 
 spirit, which may explode when it is relit 
 after being refilled. All this is prevented 
 by forming the connection by means of 
 a tube. The Berzelius lamps of recent 
 manufacture are made with this improve- 
 ment. 
 
 Either of these lamps, and all others 
 
 in which spirit is consumed, must be provided with a metallic ex- 
 
THE RUSSIAN LAMP. 
 
 237 
 
 tingulsher to protect the wick and prevent evaporation of the 
 alcohol. 
 
 Roses Lamp. This lamp, Fig. 159, also constructed upon the 
 principle of the Argand burner, gives an intense heat. It pos- 
 sesses the advantage recommended by Luhme" of having the re- 
 servoir at a distance from the burner, so that the spirit remains 
 unheated during the longest operations. The wick is regulated 
 by a rack and pinion as in the Berzelius lamps, and its mode of 
 management is precisely the same. 
 
 The Russian Lamp. This apparatus, Fig. 160, affords a 
 very powerful heat in a few minutes. It consists of a strong 
 double brass cylinder or box, the interior arrangement of which 
 is shown by the dotted lines in the cut. A piece of tube termi- 
 nating in a jet passes from the exterior to the interior chamber, 
 rising nearly to the top of the former. The fuel is supplied 
 through the aperture , closed with a cork, and not with a brass 
 cap. The lamp is known to be fully charged when the spirit 
 begins to flow from the jet. The inner chamber is then to be 
 filled with the same spirit to within half an inch of the apex of 
 the jet. The ignited spirit in the inner chamber heats that in 
 the outer, and causes it to boil, the pressure of the vapor forces 
 the boiling spirit through the jet in a powerful stream, which of 
 course becomes immediately inflamed, and acts as an energetic 
 blast, producing heat enough to ignite a platinum crucible, placed 
 above it, to whiteness. The triangle which supports the crucible 
 must be of platinum, and the ring upon which the triangle rests 
 of very stout iron wire in order to resist the fusing effect of the 
 
 By enclosing the crucible in a Fi s- 16 - 
 
 jacket (Fig. 156), for which the 
 rim of the lamp will form a suffi- 
 cient support, the action of the 
 blast is greatly expedited as well 
 as augmented. 
 
 There are certain precautions 
 necessary in the use of this 
 lamp, to guard the operator 
 against accidents. Before in- 
 troducing the alcohol, it is proper to be assured that the jet is 
 
238 
 
 DEVILLE'S BLAST LAMP. 
 
 free from impediment by blowing through it. The cork stopper 
 b must be put in somewhat loosely, so that it may offer no resist- 
 ance should a stoppage occur during the operation. For still 
 greater safety, that part of the lamp should be turned from to- 
 wards the experimenter. 
 
 Pyroxylic spirit is the fuel recommended ; and it is said that a 
 lamp of this construction, 3J inches in height, 3J inches in dia- 
 meter, will burn with a charge of four ounces of spirit for thirty 
 minutes, which is long enough for most fluxions with carbonated 
 alkali. 
 
 Hart's gas furnace, hereafter described, is intended by the 
 inventor as a substitute for the Russia lamp. 
 
 Devilles Blast Lamp. This implement, the invention of St. 
 Clair Deville, is designed for producing high temperatures with 
 the use of alcohol, wood spirit, kerosene, camphene, and similar 
 fluids, as fuel. Those hydro-carburets which have the lowest 
 boiling-point and give the densest vapors, afford the greatest heat. 
 The lamp is applicable for fusions, fluxing, and ignitions, and a 
 few seconds only are necessary to raise the heat equal to that of 
 melting iron. 
 
 Fig. 161 is a drawing of the apparatus. " It consists of a 
 reservoir F, with three tubulures above, 
 T t t f . By means of the blast of a blow- 
 pipe table, the air is injected into F 
 through the tube v, which is inserted in 
 T. The tubulure t carries the vertical 
 tube o, which has a stop-cock at R, and 
 divides above into the two arms b b', 
 which pass into a metallic box u, and 
 terminate in its upper part with open ex- 
 tremities cut off obliquely. The box u 
 contains the burning fluid e partly filling 
 it ; and it connects with a reservoir by ", 
 which -is kept at a constant level. The 
 centre of this box is a cylindrical tube, 
 closed below, through which passes the blow-pipe e> a continua- 
 tion of the tube ', the left tubulure (in the figure) of the flask F. 
 The tube which is at the middle of the box u, and envelopes the 
 blow-pipe c, has several small holes u u communicating with the 
 empty (or upper) part of the box u. 
 
 Fig. 161 
 
NUNN'S BLAST LAMP. 239 
 
 " Above the blowpipe, and resting in a furrow in the top of the 
 box u, there is a copper cup K, pierced at the centre with a hole 
 for the passage of the jet of vapor which escapes from the holes 
 u u u, after the bellows are put in action. 
 
 " To prevent the burning fluid from becoming too much heated 
 there is a trough s containing water. Before lighting the lamp, 
 the fluid in L is heated till the water in the trough boils ; then 
 the bellows are made to act, and the jet of vapor is lighted ; after 
 which the heat disengaged by the lamp is sufficient to continue 
 the vaporization of the fluid. 
 
 " Above the box L there is a chimney A having a series of 
 holes around near its bottom for drawing in air on the flame of 
 the apparatus." 
 
 Nunris Blast Lamp. In this apparatus, steam is made to 
 accomplish the purpose of a blow-pipe table in a very simple and 
 efficient manner. The fuel may be either alcohol, oil, or tallow, 
 but each requires its peculiar burner. 
 
 The boiler is constructed after the manner of a still-body, and 
 with a glass tube running up its external side to indicate the 
 level of the water in the interior. Descending from about two 
 inches above the boiler, and down through the top to within an 
 inch of the bottom, is a supply-pipe. The pipe is close to the 
 internal side of the boiler, and terminates at its outer projection 
 with a stop-cock attachment, to which is coupled a piece of vul- 
 canized india-rubber tubing. A safety-valve and steam-pipe 
 complete the arrangement. 
 
 The boiler being filled with water to half its capacity is then 
 heated to boiling under a regulated pressure, and loss by evapo- 
 ration supplied by a slight and continuous stream of fresh water 
 admitted through the supply-pipe. The steam is then let through 
 the pipe, and directed into the centre of the flame of the heating 
 medium. 
 
 When alcohol, naphtha, or other volatile liquids are used, the 
 jet is continued sufficiently long to volatilize a portion of the fuel, 
 before the latter is ignited. Then after the vapor is ignited, the 
 steam is again let in, and the current maintained as long as is 
 required. It is necessary that the burner should be constantly 
 above the boiler, else the steadiness of the blast will be embar- 
 rassed by accumulation of condensed steam. In an oil flame, the 
 jet of steam is made to issue from the centre of the wick. \ 
 
240 THE TABLE GAS LAMP. 
 
 Gas may also be used with this apparatus even more advanta- 
 geously than oil or alcohol ; it being only necessary to employ a 
 burner like those adapted to compound blow-pipes, and admitting 
 steam through one nozzle and gas through the other. 
 
 The Table G-as Laryp. Gas is by far the most economical 
 source of heat, being always ready for use, easily manageable, 
 and cleanly. It already replaces coal furnaces in the nicer 
 ignitions, fusions, &c. As the implements connected with its use 
 become perfected in detail, it will supersede all other means of 
 applying heat in a large majority of laboratory operations. It 
 may be conveniently led to any part of the laboratory through 
 flexible caoutchouc tubes, for which purpose one end of these 
 latter is fitted with a brass nozzle for adjustment to a gallows 
 screw at the mouth of the gas tube-feeder pending over the ope- 
 rating table. The other end terminates in either an Argand, 
 single jet, or other suitable burner, according to the purpose for 
 which the flame is to be applied. 
 
 A single jet answers very well for the small gas stands ; but for 
 use with the blow-pipe table, an Argand burner is necessary. 
 
 The gas lamp, Figs. 41, 42, which has been fully described at 
 pp. 64, 66, supersedes all other heating apparatus for table ope- 
 rations. Crucibles, capsules, and retorts, are alike readily heated 
 by it, and .even distillations on a large scale may be successfully 
 performed. To effect the latter object, the upper half of a black 
 lead or clay crucible may be placed around the lamp, provided 
 with an opening on one side for the beak of a retort to pass out. 
 The lower half of the crucible, with its bottom broken off, is then 
 inverted over the whole, and the hole at the top loosely covered 
 to allow the escape of the products of combustion. By this ar- 
 rangement, the heat of the flame reverberates through the dome, 
 and increases the effect to such a degree that several pounds of 
 mercury may be distilled at once from the red oxide. 
 
 Ga's being in general use in the large cities and towns, an 
 ample supply can be obtained from the works established for its 
 manufacture and distribution. But, in the country and thinly 
 inhabited districts which are not thus favored, the consumer must 
 depend upon private means for this convenient and economical 
 heating as well as illuminating agent. Upon a limited, but suffi- 
 cient scale, for the purposes of a small laboratory, it may be made 
 
GAS FROM GREASE. 241 
 
 from grease with a portable and inexpensive apparatus, devised 
 by Kent, and shown in the annexed drawing. 
 
 Fig. 162. 
 
 The material to be used is the refuse fat of the kitchen, a 
 gallon of which, Jn its melted state, will yield 100 cubic feet of 
 oil gas, sufficient to feed a bat-wing burner for upwards of seventy 
 hours. 
 
 It consists of a wrought iron retort, thirteen inches high and 
 six inches in diameter, with a large opening at the top for the 
 passage of lumps of coke with which it is to be three-fourths 
 filled. The coke is used to increase the extent of the heating 
 surface so as to facilitate and hasten the generation of the gas. 
 
 The retort fe to be heated to low redness, but no higher, other- 
 wise the gas becomes decarbonized. The oil is supplied to the 
 retort in a thin but constant stream from the funnel, through a 
 small hole in the key of the stop-cock. The retort is connected 
 by an iron tube with a copper reservoir immersed in cold water, 
 for the purpose of cooling the gas. and collecting a portion of un- 
 decomposed oil which passes over. An additional receiver renders 
 this apparatus applicable to the purposes of illumination or 
 heating. All the pipes and appliances for either are furnished 
 
 16 
 
242 GAS FROM ROSIN. 
 
 with the apparatus by the manufacturer, to order. The retort 
 requires to be occasionally cleansed, but at no other time has it 
 to be necessarily opened. 
 
 Large vulcanized india-rubber bags make excellent gasometers 
 for small quantities of gas ; but for 100 cubic feet, it will be 
 better to have a sheet-iron bell well payed over, internally and 
 exteriorly, with plumbago paint. The cistern for its reception can 
 be sunk in the yard, and for the above quantity its dimensions 
 must be 6J feet diameter and 4J feet depth. 
 
 Gas is by far the most economical source of heat, being pow- 
 erful, always ready for use, readily manageable, and cleanly. 
 For all the nicer ignitions, fluxions, and fusions it replaces the 
 furnace, which is less convenient, and requires tenfold the time 
 for its action. In five minutes, by the aid of the table blow-pipe, 
 Fig. 45, and appropriate burners, we can often satisfactorily com- 
 plete processes which with a furnace would require an hour. 
 This saving of time and fatigue is an important consideration 
 when the operations are to be multiplied or rapidly repeated. By 
 "driving a current of air obliquely and somewhat downward 
 through the Argand burner, the process of cupellation may be 
 accurately performed on three hundred grains of lead." 
 
 Gas may also be made, readily and economically, from rosin 
 or rosin oil. A very convenient arrangement for the purpose is 
 that exhibited by the following drawing, and known as the "Mary- 
 land Co.'s Portable Gas Apparatus." One, costing $350, com- 
 plete, including expense of transportation and erection within a 
 reasonable distance from the manufactory, will produce and store, 
 in three hours, 300 cubic feet of gas, at a total expense of 50 to 
 75 cents, only 3 gallons of rosin oil and twelve cents worth of 
 anthracite coal being consumed in the operation. Moreover, very 
 little labor or attention is required ; and as each burner needs 
 but two cubic feet of gas per hour, the product of a single dis- 
 tillation will be amply sufficient to feed five burners for four 
 hours, nightly, during a whole week. Machines of larger capacity 
 cost in proportion. 
 
 The apparatus, being of simple construction, is very manage- 
 able. It consists of 
 
 " 1st. An oil can or reservoir, * A/ for the raw material. 
 
MANUFACTURE OF GAS. 
 
 243 
 
 "2d. A stove, 'B,' in which is set the retort or Generating 
 Apparatus. 
 
 Fig. 163. 
 
 "3d. A siphon box or condensing box ' C.' 
 
 "4th. The water-tank < D.' 
 
 " 5th. The gas-holder, i E,' which hangs into the water of the 
 tank like an inverted tumbler. 
 
 "The reservoir is a simple cylindrical vessel, containing the 
 oil from which the gas is generated. The retort is an iron hollow 
 cylinder, with a spheroidal bottom and flat cover, bolted and 
 screwed to a projecting rim. The stove containing the retort is 
 of sheet or cast iron, arranged upon the most approved plans to 
 economize the heat. The siphon box, or condenser is a cast iron 
 vessel, with a movable lid bolted and screwed upon it. This is 
 divided into compartments and half filled with water, with a 
 siphon attached, so as to keep the water at all times to its proper 
 level. The water-tank, in which the gasometer floats, is made 
 of wood or iron, and placed upon the surface of the graund, or 
 which is better, sunk to the level of the water. The gas-holder 
 is of sheet iron, suspended upon fixed pulleys, and forms the re- 
 ceiver for the gas, when generated and ready for consumption. 
 The reservoir communicates with the retort by a feed-pipe, or by 
 a feed-pipe and cock, through a siphon screwed into the cover of 
 the retort. 
 
244 MANUFACTURE OF GAS. 
 
 " This siphon connects with a tube suspended perpendicularly 
 in the middle of the retort, pierced with small holes in its lower 
 end. Through this feed-pipe and siphon, the liquid passes into 
 the tube thus suspended, and by the small holes at the end of the 
 tube becomes dispersed upon the bottom and sides of the retort. 
 
 " The working of the machine and management of it requires 
 no more than ordinary skill, and may be safely intrusted to a 
 domestic. A fire is made in the stove as in an ordinary furnace, 
 and the retort is heated to a bright cherry-red heat. The cock 
 is then opened to allow the oil to pass in through the pipes from 
 the reservoir, upon the heated sides and bottom of the retort, 
 where it is instantaneously converted into gas. 
 
 " Ascending from this decomposing chamber, the gas is forced 
 through a superstratum of chemical substances, suspended upon 
 an iron grating, for its purification, into a vacant upper chamber, 
 and thence it is conducted by an iron pipe into the condensing box. 
 This iron pipe passing through the cover of the condensing box 
 descends below and discharges the gas into the water of the con- 
 densing box. Thence it rises into the vacant chamber above 
 the water, which, becoming filled, forces the gas again into the 
 water under one of the several compartments above referred to, 
 into a second chamber, and then on through consecutive baths 
 before it finds its exit from the last of the series of consecutive 
 chambers. 
 
 " This exit is through a pipe which communicates from the 
 condenser with the water-tank into which it enters, and passing 
 through the water above, again descends, and discharges the gas 
 into the water for its last bath, thence it rises into the vacant 
 chamber of the gasometer ready for use. Connected with the 
 siphon of the condenser is a small covered vessel, which receives 
 the impurities washed from the gas in its passage through the 
 baths. The machine as above described, occupies a space of 
 eight feet by twelve, and in height thirteen feet, with the tank 
 upon the ground. If the tank be sunk, then the height will be 
 but seven feet. 
 
 " The material used is an oil from rosin, though not what is 
 generally understood as rosin oil. It is an earlier, cheaper, and 
 better product of colophony, decomposable at a lower, and there- 
 fore more economical degree of heat." 
 
MANUFACTURE OF GAS. 
 
 245 
 
 The supply of this material is inexhaustible, and any antici- 
 pated demand can scarcely enhance the price, which is now 12J 
 cents per gallon. Each gallon of the raw material may be safely 
 estimated to make one hundred cubic feet of gas. 
 
 When gas is used it is only necessary to bring the Argand 
 burner, Fig. 46, over the jet 3, Fig. 45, and to depress it so 
 
 Fig. 164. 
 
 much that its orifice may extend a short way into the flame for 
 heating a vessel of small surface, Fig. 164, and still further for 
 vessels of greater superficies. The gas being turned on and in- 
 flamed, the treadle is then worked with the foot, slowly at first, 
 until the current of air thus forced up through the tube changes 
 the white and quiet flame into one of a pale reddish tint and 
 ragged outline. If too much air be driven through, the flame 
 becomes bluish, and the heat becomes less intense. 
 
 When a lamp is used, it is necessary that it should have a cir- 
 cular Argand burner, which is to be placed over the jet 3, in such 
 a position that the orifice of the latter projects through the centre 
 of the burner, just beyond the top of the wick. The length of the 
 flame being proportional to the elevation of the wick, the latter 
 must be adjusted accordingly by the screw and rack before being 
 ignited. The flame being of the proper height, the treadle 4, 
 
246 
 
 GAS FURNACES. 
 
 Fig. 165. 
 
 Fig. 45, is to be worked at first slowly, for the heat must be 
 gradually applied, and then more rapidly by increasing the 
 motion of the foot until the blast produces a buzzing sound, when 
 the impulse is continued or moderated as the case may require. 
 
 The crucible to be heated is placed upon a wire triangle, rest- 
 ing upon a ring of an upright support, as shown in the figure, 
 and is placed over the FLAME, so that it may be surrounded by 
 the upper or hotter portion (BLOW-PIPE). If the flame is smoky, 
 and deposits carbon on the side of the crucible, the blast must be 
 increased or the flame lowered. 
 
 The operation being finished, the covered crucible is left to cool 
 before being opened. 
 
 Beetle's G-as Furnace. This apparatus, Fig. 165, gives a heat 
 of sufficient power to fuse a silicate with 
 carbonate of soda in a few minutes. It is 
 made very much in the form of an ordi- 
 nary gas stove, but with a movable door, 
 having a gateway to afford a view of the 
 interior, as may be necessary to observe 
 the progress of the operation. The body 
 of the stove, a gas and air-chamber , 
 should be 10 to 12 inches high and 3 to 4 
 inches in diameter. The tube b conveys 
 the gas to the chamber, where, becoming 
 mixed with air, it then passes upward 
 through the meshes of the wire gauze dia- 
 phragm <?, where it is ignited and allowed 
 to burn. The circumference of the rim, 
 just above the diaphragm, is pierced with 
 holes for the free admission of air to the 
 burning flame. The support for the cru- 
 cibles consists of iron pieces projecting 
 from a broad iron ring e, made to fit the 
 furnace. These latter parts being movable, they may be re- 
 placed by others adapted to the various sizes of crucibles. 
 
 Hoffman's G-as Furnace. This arrangement, shown by the 
 accompanying drawings, Figs. 166 and 167, is designed as a sub- 
 stitute for Liebig's Charcoal Furnace, in Organic Analysis, and 
 
GAS FURNACES. 
 
 247 
 
 for heating long tubes in a horizontal position. Its advantages 
 over coal fire are so obvious that we will not enumerate them ; 
 for though faulty in some respects, it is still a very efficient 
 
 Fig. 166. 
 
 implement, which gives a strong heat, and with the means of 
 accurately regulating it, according to the requirements of the 
 process. As in other gas furnaces, the gas is burned after having 
 become mixed with sufficient air to produce, in its combustion, 
 the maximum of heating power. We are indebted to Liebig's 
 Hand-Book of Organic Analysis for our drawings and description. 
 The furnace A, made of wrought-iron plate, consists of three 
 separate compartments A, i, &, which are supported by a stout 
 iron stand I m. Of these three compartments, the two first h and 
 i are simply rectangular boxes of iron, open at the bottom and 
 covered at the top with wire gauze, and supplied by horizontal 
 perforated gas pipes w, n, Fig. 167. The last compartment k 
 differs from the preceding in being subdivided into four smaller 
 chambers by three diaphragms 0, p, q, the gas being supplied 
 by two pipes instead of one. The lower pipe r r is a counter- 
 part of the gas-pipe w, w, of the other compartments. On the 
 other hand, the upper pipe s, , supplies the gas to two rows of 
 fine vertical tubes, similar to those in Leslie's burner, the ex- 
 tremities of which project through the wire gauze cover of the 
 compartment, as seen in Fig. 167. Each pipe is provided with 
 
248 
 
 GAS FURNACES. 
 
 Fig. 167. 
 
 air-tight pistons, by which 
 the heat is entirely under 
 the control of the operator. 
 A frame x, above the wire 
 gauze, as shown by Fig. 167, 
 supports the tube contain- 
 ing the matters to be heat- 
 ed ; and in the same draw- 
 ing, there is a view of one 
 of the side pieces #, fast- 
 ened to the frame by tongues 
 z, in such a manner as to 
 form a dome for reflecting the heat downwards upon the combus- 
 tion-tube. 
 
 To afford an intelligent expression of the manner in which this 
 furnace operates, we present a view of it, Fig. 168, as arranged 
 for performing combustion in an organic analysis in a mixed at- 
 mosphere of air and oxygen. 
 
 A is the furnace, fed with the gas, through tubes a, 5, c, d, 
 which are fitted with stop-cocks e, f. The combustion-tube, con- 
 taining the matters to be heated, and supported in the usual 
 manner, as shown at $r, communicates, in the usual manner, with 
 a chloride of calcium tube B, a bulb apparatus c, and a U tube D, 
 for solid potassa. In the rear is a series of tubes containing 
 hygroscopic substances, for abstracting carbonic acid and moisture 
 from the air and oxygen, as they pass from the gasometers H, I, 
 into the combustion-tube. Of this series, E contains solid potassa, 
 and F pumice-stone impregnated with sulphuric acid. There is a 
 third piece or bottle G, containing oil of vitriol, and which serves 
 the double purpose of a bubble-gauge for measuring the rapidity 
 of the current. 
 
 The joints being all tight, gas is then let on through the flexi- 
 ble tube d to the lower gas-pipe r r, and the piston u pushed so 
 far from the inlet as to supply the gas to the chamber 0, I (Fig. 
 166) only, whilst it is excluded from the other chambers. The 
 air-flame thus obtained keeps the rear end of the combustion-tube 
 at a dull red heat. The cock c is next opened, so as to admit a 
 small quantity of gas into the upper gas-pipe s 8, and the piston 
 at the same time drawn so far from the inlet as to confine the gas 
 
GAS FURNACES. 
 
 249 
 
 to a very few of the little tubes, at the extremity of which more 
 
 Fig. 168. 
 
 points of flame are thus produced. Succeeding portions of the 
 
250 GAS FURNACES. 
 
 tube are heated at the proper periods by gradually pushing in 
 the piston u of the lower tube, and supplying gas to all the 
 chambers of the compartment Jc, until the whole length of the 
 tube is exposed to a uniform air-flame. 
 
 This arrangement affords great facility in heating tubes, with 
 the least possible expenditure of labor and time, as well as of 
 money ; for the cost of the gas consumed is very trifling, and the 
 heating-tubes are rarely injured or broken, provided sufficient care 
 has been observed to heat it gradually in the first part of the ope- 
 ration. As a great security against cracking the tubes, the gas 
 should be first lighted below the wire gauze and extinguished 
 after the furnace has acquired warmth. It is then to be imme- 
 diately lighted again above the gauze. 
 
 The wire gauze becomes choked by use, and requires to be 
 frequently renewed ; on which account the furnace is constructed 
 so that this repair may be easily made by the operator, without 
 the assistance of a gas-fitter. 
 
 The apparatus being arranged into three divisions is adapted 
 for operations with short tubes as well as with those of medium 
 and greater length. 
 
 Hart's Gf-as Furnace. This is a modification of Nunn's Blast 
 Lamp, in which the combined action of a steam jet and a gas 
 flame is made an effective means of producing heat sufficient for 
 all the ordinary operations performed in platinum crucibles. It 
 is simple and inexpensive, and works very much like a Russia 
 lamp, so that it requires very little watching. 
 
 The apparatus is formed of a round copper basin a, five inches 
 in diameter, and fitted by brazing with a close circular top of the 
 
 same metal. Rising through 
 the centre of this top is a 
 small copper tube 6, serving 
 as the jet. It is inserted 
 in an elbow-joint c, to which 
 is attached, laterally, a short 
 piece of gas tube d. There 
 
 is another tube opening at e, for the admission of water. To set 
 the furnace in operation, it is only necessary to fill the basin a 
 half full of water, and after having corked the tube b tightly, to 
 place it on the ring of a retort-stand over a gas flame. In the 
 
COMPOUND BLOW-PIPE. 251 
 
 mean time, a flexible tube attachment is made at d, for the pur- 
 pose of supplying gas from one of the laboratory burners. As 
 soon as the water boils and steam begins to issue through the jet, 
 the gas is turned on and lit at c. The flame produced is a hot blue 
 brush ; and care must be observed to rightly proportion the size 
 of the flame and pressure of the steam current, so as to obtain its 
 maximum of heat, and prevent the former from being extinguished 
 by the power of the blast. The jet must be always kept free, and 
 to this end should be probed with a pin immediately before use. 
 
 Compound Blow-Pipe. This apparatus, known as Hare's 
 oxyhydrogen blow-pipe, is used for the fusion of such refractory 
 but fusible substances as resist the highest power of the furnace. 
 Its action is based upon the intense heat produced by the ignition 
 of combined oxygen and hydrogen gases, and is fully explained 
 under the head of BLOW-PIPE in Booth's Encyclopaedia of Che- 
 mistry. Explanatory drawings of one of these implements, 
 adapted for large operations in the arts, are to be seen in Apple- 
 ton's Dictionary of Mechanics and Engineering, vol. i, p. 107. 
 Our remarks will refer to economical forms of the apparatus, 
 suitable for laboratory purposes. 
 
 Fig. 170 exhibits Kent's pattern. It consists of two vulcanized 
 
 Fig. 170. 
 
 india-rubber bags or reservoirs, of twenty gallons or greater 
 capacity. These bags are very flexible, strong, and portable ; 
 
252 COMPOUND BLOW-PIPE. 
 
 one of the above size, when empty, occupying but a very limited 
 space. They are filled, the one with oxygen, and the other with 
 hydrogen gas, each being fitted with a connecting screw and 
 etop-cock, by which they can be adjusted directly to the genera- 
 ting apparatus, as shown by:Fig. 171, or with a gasometer, when 
 
 Fig. 171. 
 
 they are to be charged. The communication between the bags and 
 the jet-pipe above the table is by means of the flexible india-rub- 
 ber or lead tubes, coupled by gallows screws, Fig. 171. The 
 jets are so divided within the pipe that the gases enter at oppo- 
 site ends, and consequently are not mixed until they meet at the 
 arm of the jet, which is so arranged that it can be raised or 
 lowered on an ordinary retort stand. By this arrangement, 
 which is a convenient modification of the old double-jet, a jet of 
 oxygen passes through the centre of a circular flame of hydrogen, 
 the mixture and consequent explosion of gases being avoided. 
 
 The gradual efflux of the gas from the reservoirs is effected by 
 superposed weights, a much more convenient mode than that of 
 hydrostatic pressure, which is requisite when metallic reservoirs 
 are used. 
 
 The two gases are very readily prepared. The whole appara- 
 tus for oxygen is shown in Fig. 171. The retort, a thin copper 
 flask, is connected with a brass cap and neck by a gallows screw. 
 
 Four ounces of good chlorate of potassa, and one ounce of per- 
 oxide of manganese are mixed together and placed in the retort, 
 the cap screwed down, and the joints luted with pipe-clay. The 
 heat of a Berzelius lamp, applied as shown in the figure, drives 
 over ten gallons of pure oxygen in fifteen minutes. 
 
GENERATION OF HYDROGEN GAS. 253 
 
 The lamp may be removed as soon as the gas begins to be 
 generated and pass over freely, as sufficient heat will be retained 
 for the completion of the operation. The caput mortuum of 
 chloride of potassium and oxide of manganese remaining in the 
 retort can readily be removed by water. 
 
 Hydrogen can still more readily be obtained from a self-regu- 
 lating reservoir. Fig. 172 exhibits the apparatus as made by 
 
 Fig. 172. 
 
 Kent. The copper cylinder which he uses is replaced in other 
 similar instruments by glass. It consists of a japanned copper 
 cylinder, 9 inches high, and 6 inches diameter, with a cover and 
 bell attached. 
 
 Within the bell hangs a basket of copper wire, which is to be 
 filled with about f Ib. of zinc, in lumps. The outer cylinder is 
 to contain 6 Ibs. of cold diluted sulphuric acid, made with 1 
 part acid to 4 of water. 
 
 In the upper part of the bell is a division, forming a recep- 
 tacle for a strong solution of potash, 2 f . 3 of which are put into 
 it through the opening in the top, which is then to be tightly 
 stopped. 
 
 The apparatus being adjusted, and the stop-cocks opened, the 
 dilute acid rises in contact with the zinc, and generates hydro- 
 gen gas, which, being forced through the potassa solutions, be- 
 comes washed previous to its exit from the stop-cock into the 
 bag. An hour suffices to generate twenty gallons of gas ; and, 
 when it is desired to arrest the operation, close the stop-cock so 
 as to produce an accumulation of gas in the bell, and thus dis- 
 
254 
 
 DRUMMOND LIGHT. 
 
 place the acid. The action may be renewed at any time by open- 
 ing the cock. 
 
 Accompanying this apparatus, as shown by separate figures in 
 the cut, are two convenient addenda for other purposes ; one a 
 jet, with platina sponge and fixtures, for producing an instanta- 
 neous light, and the other for bending glass tubes, &c. They 
 are both readily attached to the stop-cock by their screws. In 
 the first case, the gas is projected against the platina sponge, and 
 becoming immediately ignited affords a ready means of lighting 
 a taper. The sponge, when not in use, should be kept covered 
 and dry. 
 
 The oxyhydrogen blow-pipe is put into operation by first charg- 
 ing the bags with gases, placing on their weights, letting on the 
 hydrogen, igniting it, and passing a jet of oxygen through the 
 flame directed upon the substance under process. This substance 
 should rest upon charcoal or fire-brick, and in a cavity drilled for 
 the purpose, so as to prevent its being blown away by the force 
 of the blast. For the same reason, when the substance is in 
 powder, it is necessary to moisten it with water, and compress it 
 in the cavity. The charcoal rest is very conveniently supported 
 
 Fig. 173. 
 
 Fig. 174. 
 
 upon one of the sliding rings (Fig. 173), which allows the facility 
 of bringing it near to the orifice of the pipe where the combustion 
 takes place. 
 
 The heat thus produced is very intense, and melts platinum 
 
RITCHIE'S COMPOUND BLOW-PIPE. 
 
 255 
 
 readily. Coal or illuminating gas may be substituted for the 
 hydrogen. 
 
 When this apparatus is used for the purposes of illumination, 
 as in the production of the Drummond light, which is produced 
 by the action of its flame upon a cylinder of lime, the nozzle of 
 the blow-pipe must be pointed upwards, so that the flame may 
 have full play upon the incandescent earth. 
 
 Another form of compound blow-pipe, as made by Ritchie, is 
 shown in the annexed figure. 
 
 Fig. 175. 
 
 The gas-holders are a pair of metallic vessels placed upon a 
 framework which moves on castors. These vessels consist seve- 
 rally of an outer bell and inner cylinder, the latter being sus- 
 pended in the former by counterpoise weights concealed in the 
 posts of the stand. Self-adjustment is thus secured in propor- 
 tion as gas enters or passes out of the gasometer, and very little 
 water need be used. 
 
 The drawings show the'two gasometers attached as a compound 
 blow-pipe, with all its necessary appurtenances, tubes, stop-cocks, 
 

 256 
 
 TATE'S COMPOUND BLOW-PIPE. 
 
 Fig. 176. 
 
 flexible hose with jets and adjustable holder. As each, however, 
 has its distinct inlet-pipe, screw-plug, &c., they may be used 
 separately for other purposes. 
 
 Tate has proposed a form much simpler and more economical 
 than either of the preceding. It moreover answers the double 
 purpose of an oxyhydrogen blow-pipe and gas-holder. It consists 
 of a receiver r, Fig. 176, with a shelf s, adjustable to b by a screw 
 connection. Like other gasometers it is provided with stop-cocks 
 e, e. The inlet-pipe is at p, and the jet at g. At the thick part 
 h of this jet there is a wire gauze diaphragm. When the appa- 
 ratus is to be used as a blow-pipe, the receiver must be filled with 
 water to d, and the mouth b closed with a tight cork ; after which 
 a gas-bag containing a mixture of oxygen and hydrogen is con- 
 nected by a flexible tube attachment 
 to a bent metal pipe Jc, n, passing 
 into the interior of the receiver. 
 When pressure is then applied to the 
 bag a current of mixed gases passes 
 out and upwards through the water 
 into the tubular portion d, b, of two 
 inches height, and f inches internal 
 diameter. Thence it passes through 
 the jet upon the opening of the cock 
 thereof, and may be ignited as it 
 issues. There is perfect safety in the 
 arrangement, for, if by chance, the 
 flame in the jet should rush back, any 
 explosion that it might produce would 
 be trifling and restricted to the small 
 volume of gas in d, 6, as the water in 
 r prevents communication with the gases in the bag reservoir. 
 
 To convert the apparatus into a gas-holder, it is only necessary 
 to remove the jet or shut off communication with it by closing 
 the cock e, screwing on the shelf at &, and replacing the flexible 
 tube and gas-bag by the funnel/, v. The inlet p is then opened 
 for the admission of gas from a flask or generator. Pressure is 
 applied by a column of water descending through /, v ; and the 
 outlet for the gas is at *, e. 
 
LAMPS. 257 
 
 Sonnenschein 8 Blast-Lamp. Ritchie has introduced another 
 form of compound blow-pipe, which occupies no more room than 
 a Berzelius lamp, and is both convenient and efficient for blowing 
 glass and heating crucibles to a high temperature. It differs in 
 construction from the preceding, but assimilates to them in prin- 
 ciple, the heating medium being the flame produced by combustion 
 of a mixture of atmospheric air and illuminating gas. The whole 
 arrangement is shown by Fig. 177, and consists of an upright 
 
 Fig. 177. 
 
 stand A, steadied by a heavy foot, and upon which slides the brass 
 lamp B by its bulb , fitted with a binding-screw x, for adjusting 
 it upon the rod at any required height. Projecting from this 
 bulb are two opposite branches, the one at the left having a stop- 
 cock 5, with a screw-end c for the adjustment of a flexible tube #, 
 connected by a gallows screw with the table or building gas-pipe. 
 The right branch is^rather more compli- 
 cated in structure, and consists of two 
 parts, one of which, e /, is fixed hori- 
 zontally in the ball e, while the other, 
 h ra, is appended to it by two movable 
 joints, so as to impart both a horizontal and vertical motion, and 
 thus afford the convenience of giving the jet any desired bearing. 
 The tube h ra, is concentric, as shown nearly in full size by Fig. 
 178, so that the gas passes forward uninterruptedly through e^ g, 
 h, and between the tubes to the point of issue m, where it is met 
 
 17 
 

 258 
 
 LAMPS. 
 
 by a current of air emerging from the smaller centre tube, -which 
 is distinct from the outer, and communicates with the ball ?, and 
 thence by a flexible tube i with a bellows or blast-table. The 
 inner tube is a quarter inch shorter than the outer one, and ends 
 in a pointed jet, so that the admixture of gas and air takes place 
 just behind the point at which they are ignited. This precaution 
 prevents accident from explosions. To give the apparatus its 
 maximum force the air may be heated as it passes forward by 
 merely placing a spirit lamp under the ball I. A veritable hot 
 blast is thus produced. 
 
 The above lamp is also made after a modified pattern, so as to 
 bring into service, simultaneously, an assemblage of jets. The 
 drawing below, Fig. 179, explains the arrangement, which rests 
 
 Fig. 179. 
 
 upon the top of a blow-pipe or blast-table, from which rises an 
 air-pipe i. The gas connection is made by means of the flexible 
 pipe , and each jet being concentric, the gases only mix at the 
 points of issue, as in the apparatus before described. This com- 
 bination of jets produces a heat of great intensity. 
 
SUPPORTS TRIANGLES. 
 
 259 
 
 When crucibles are under process with this apparatus, they 
 should be firmly secured upon the supports, and placed either 
 above or below the jet. For ordinary purposes the breath will 
 answer the place of a bellows. 
 
 Supports. In lamp, table furnace, and blow-pipe operations, 
 vessels are maintained in a required position by supports, differ- 
 ing in material and construction with the uses for which they are 
 destined. 
 
 A very simple and economical support is shown in Figs. 173 
 and 174, the only difference between the two being in the shape 
 of the foot, one being rectangular and the other round. It con- 
 sists of an upright iron rod, from 20 to 24 inches long, arid about 
 J of an inch or more in diameter, screwed into a cast-iron foot, 
 and fastened beneath by a nut. The three projecting-rings, of 
 iron wire, 2, 3, and 4 inches in diameter, are held by thumb- 
 screws, which permit their elevation or depression at will. 
 
 For the larger stands the thumb-screw is of iron, and of the 
 form exhibited in Fig. 164 and Figs. 180, 182, b. It is made with 
 
 Fig. 180. 
 
 two holes, at right angles to each other, and two screws, one for 
 the reception of the iron upright, and the other for the handle of 
 the ring, which can readily be detached and replaced by another 
 of different size. This form of screw and socket prevents the 
 necessity and expense of having the rings attached to the screws. 
 One of these screws will answer for a series of rings, and the 
 latter being of iron wire, the operator can 
 readily form them himself of any required 
 shape. With this arrangement, and a 
 series of different-sized rings, the support 
 is convenient for all its purposes without 
 the expense of a socket for each ring. 
 When the rings are too large for the ves- 
 sels to be heated, their diameters may be 
 
 Fis. 181. 
 
260 
 
 THE UNIVERSAL SUPPORT. 
 
 Fig. 182. 
 
 diminished by means of stiff wire triangles, Fig. 181, called 
 trivets. They are- particularly useful for the support of small 
 crucibles, as is shown in Fig. 41, p. 64. There should be a 
 number of them of different sizes. 
 
 Fig. 182 exhibits what is called the " universal support." The 
 
 foot is of cast iron, and the toes 
 twelve inches apart. The up- 
 right rod is of iron, 36 inches 
 long, and -| in diameter. It is 
 substantially made, for the sup- 
 port of heavy capsules, retorts, 
 &c. The thumb-screw and 
 sockets b are of solid brass or 
 iron. A brass vice, 6 inches 
 long, and 1J inches wide, lined 
 in its mouth with buckskin, is 
 shown at g. It is fitted by the 
 arm / to the hole c, and serves 
 for the support of heavy retorts 
 and other beaked vessels, as 
 shown in the figure. Three solid 
 
 brass rings, of from 4 to 7 inches diameter, accompany this stand, 
 and are held in the socket d by the thumb-screw a. As the arm 
 of each of these rings is adapted to the socket, one may replace 
 the other when it is desired to change the size. 
 
 Wooden supports adapted for tube arrangements, made of box- 
 wood or hickory, and lined with cork or buckskin at the parts 
 intended for grasping, are also convenient and necessary pieces 
 
 Fig. 183. 
 
 Fig. 184. 
 
 Fig. 185. 
 
 of apparatus. They consist of foot, rod, and nut, similar to the 
 iron supports. Their other parts are a wooden vice (Gay- 
 Lussac's), Fig. 183, for supporting the necks of retorts and other 
 
WOODEN SUPPORTS. 
 
 261 
 
 beaked vessels ; Gahn's cylinder-holder, Fig. 184, for experiments 
 with gases ; and a wooden ring, Fig. 183, as a rest for inverted 
 
 Fig. 186. 
 
 Fig. 187. 
 
 flasks. Figs. 186, 187 exhibit an upright retort clamp with a 
 movable joint and wooden screw, by which it can be raised or 
 lowered at pleasure. The stand or lower portion is similar in 
 
 *Fig. 188. 
 
 Fig. 189. 
 
 construction to D E, Fig. 191. Another form of vertical holder 
 for supporting horizontal tubes, &c., is shown by Fig. 186. 
 
9 
 
 262 
 
 WOODEN SUPPORTS. 
 
 Fig. 188 represents another support, with two sliding arms, the 
 upper one of which is a funnel-stand, and the lower a tube or 
 retort-holder. The funnel supports of the upper arm are adjusted 
 thereto by means of wooden thumb-screws, and may be removed 
 at pleasure. These are less convenient than the single filter- 
 stands, Figs. 189 and 190, though they have the advantage of 
 
 Fig. 190. 
 
 Fig. 191. 
 
 allowing several simultaneous filtrations upon one arm, and thus 
 a single stand may do the service of three or four, according to 
 the length of the arm. The uprights of these supports should be 
 screw-cut at the lower end, and fastened to their pedestals by 
 means of nuts, which retain them in place more firmly than any 
 other mode. 
 
 A form of stand, known as Berzelius's table support, is shown 
 by Fig. 191. It is of hard wood, and consists of a loaded foot D, 
 supporting a flat disk A, which, by means of its leg and the 
 thumb-screw E, can be raised or lowered to any desired height. 
 This is a very convenient rest for a small lamp or furnace, or for 
 recipients in distillations, when it is required to raise either above 
 the level of the operating-table. When in this or other cases 
 the surface of the supported vessel is round, it is safer to steady 
 it upon a braided straw ring, Fig. 192, interposed between its 
 bottom and the disk. 
 
TUBE AND BULB RESTS. 
 
 263 
 
 Fig. 192. 
 
 For supporting tubes and other vessels horizon- 
 tally, the disk may be replaced by the brass crook, 
 as shown in Fig. 193 ; and for globular vessels and 
 flasks by the wooden tripod, Fig. 194, or, still 
 better, a wooden bowl. Each of these pieces is 
 adapted to the stand D, and one may replace the other when 
 necessary, the screw allowing them to be raised and steadily 
 maintained at the required height. The height of this instru- 
 ment, when drawn out to its full length, is twenty inches. 
 
 Fig. 194. 
 
 Fig. 195. 
 
 As a support for large evaporating vessels over furnaces, an 
 iron tripod, Fig. 195, is very convenient. 
 
 The test-tube stand or rack, which is the only support that 
 remains to be mentioned, has been alluded to before, p. 63, Fig. 
 39. A smaller one for table use is shown in Fig. 196. It con- 
 sists of two narrow uprights, say ten inches high, of thin poplar 
 wood, which are braced together by three shelves. These shelves 
 are perforated throughout their length with auger-holes for the 
 reception of the test-tubes. The smaller and shorter tubes occupy 
 the upper range ; the interval between 
 which and the middle shelf should be 
 less by an inch than that between it 
 and the lower. 
 
 The manifold uses of the aforemen- 
 tioned instruments will be more fully 
 explained when we refer to manipula- 
 tions for which they are applicable. 
 At present, a familiar idea may be 
 obtained by reference to Figs. 152, 154, 155, and to the cut 
 
 Fig. 196. 
 
264 
 
 BATHS. 
 
 below, in which several of them, as applied in operations, are 
 included. 
 
 Fig. 197. 
 
 CHAPTER XII. 
 
 BATHS. 
 
 CUE remarks in this chapter will refer to the means by which 
 the fire heat is moderated and diffused, before being applied to the 
 containing vessels of substances under process. These means 
 consist of baths, which are called vapor, water, saline, metallic, 
 oil, or sand, according to the nature of the interposed bodies em- 
 ployed. 
 
 The object of an intermedium is to prevent a too rapid appli- 
 cation of heat, and to give greater uniformity of temperature. 
 Inequality and too sudden application of heat being thus provided 
 against, the fracture of vessels and ejection of their contents, and 
 many inconveniencies attending other modes of applying heat, are 
 avoided. 
 
 Baths are very convenient for heating substances which re- 
 quire a constant and somewhat permanent elevation of tempera- 
 
CONSTRUCTION OF BATHS. 265 
 
 ture, and which might undergo decomposition over the naked 
 fire. The temperature to be obtained, is, however, only limited, 
 but by a proper management of the fire any degree of heat, up to 
 the maximum amount which the intermedium is capable of re- 
 ceiving from the means employed, can be obtained. 
 
 Baths consist of two vessels of different diameters, and they may 
 be either of metal, stoneware, or porcelain. The outer jacket 
 receives the intermediary body, and the inner one the substance 
 to be heated. As generally constructed, baths are made with 
 but one jacket, the aperture or mouth being of diameter cor- 
 responding with that of the heating vessel which is to be placed 
 over it. This arrangement obviates the necessity of an inner 
 jacket, and also of the transfer of the substance which is being 
 heated. 
 
 Baths are useful in operating upon organic and other bodies 
 easily alterable by heat. They are also convenient for deter- 
 mining the melting-point of those substances which are fusible at 
 or below the degree of heat which can be imparted to the liquid 
 or vapor of the bath : that temperature being made known by 
 immersing a thermometer at the commencement of the fusion and 
 noting the degree. 
 
 In the fluid baths the thermometer may be permanently fixed 
 by means of *a perforated cork, closing a circular aperture in the 
 lid. Fig. 120, with the scale upon the stem, exhibits the most 
 suitable form of the instrument for this purpose. The difference 
 in temperature between the bath and the heating substance^ 
 which is sometimes very considerable, especially when porcelain 
 or glass is used, may be diminished by keeping the bath always 
 covered. If the vessels have smooth surfaces, the heat obtained 
 previous to ebullition is much higher than in the opposite case. 
 While the bath is in use, care must be taken that the amount of 
 the liquid in the outer vessel remains as nearly as possible the 
 same throughout the process, and the loss from evaporation or 
 exit of vapor should be replaced by frequent but gradual additions 
 of the same fluid. 
 
 Steam-bath. This apparatus forming a fixture of the labora- 
 tory has been fully described at p. 46, D and B, Fig. 18, and is 
 very serviceable in extracting vegetable matters, and for rapid 
 
' ' Vf 
 266 STEAM-BATH WATER-BATH. 
 
 evaporations at temperatures below the heat of direct fire. It is 
 also a convenient arrangement for heating those substances which 
 would be alike injured by direct contact with steam. It affords 
 a temperature of fully 212 F. when used without pressure as at 
 D. When, however, the steam is employed under pressure, as is 
 provided for in B, a temperature of 240 F. can be obtained with 
 ten pounds to the inch. With five pounds pressure the tempera- 
 ture will be 226 F. 
 
 For very small operations, the apparatus of Dr. Ure, Fig. 198, 
 
 is an excellent contrivance. "It 
 Flg * 198 ' consists of a tin box, about 18 
 
 inches long by 12 broad and 6 
 deep. The bottom is hollowed 
 a little by the hammer towards 
 its centre, in which a round hole 
 is cut, of five or six inches in 
 diameter. Into this a tin tube, 
 three or four inches long, is sol- 
 dered. This tube is made to fit 
 
 tightly into the mouth of a common tea-kettle, which has a 
 movable handle. The top of the box has a number of circular 
 holes cut in it, of different diameters, into which evaporating cap- 
 sules of platinum, glass, or porcelain are placed. When the 
 kettle, filled with water and with its nozzle corked, is set on a 
 stove, the vapor playing on the bottom of the capsules heats them 
 to any required temperature, and being itself continually con- 
 densed, it runs back into the kettle to be raised again in cease- 
 less cohobation. With a shade above to screen the vapor-chest 
 from soot, the kettle may be placed over a common fire. The 
 orifices not in use are closed with tin lids. In drying precipi- 
 tates, the tube of a glass funnel may be corked and placed with 
 its filter directly into the opening of a proper size. For drying 
 red cabbage, violet petals, &c., a tin tray is provided, which fits 
 close to the top of the box within the rim which goes about 
 it. The round orifices are left open when this tray is applied." 
 
 Water-lath. The water-bath is used for heating substances at 
 temperatures within that of boiling water. It is very available 
 where bodies easily decomposable by high temperatures are to be. 
 
CONSTRUCTION OF WATER-BATH. 267 
 
 heated, and is also useful for the gradual exhaustion of vegetable 
 and other substances which only give up their soluble matter after 
 long contact with the warm solvent liquid. They also serve to 
 complete evaporations to dryness, which, though commenced on 
 the sand-bath, require at the end a more intense heat. Though 
 seldom employed for the purpose of reducing the temperature 
 very low, it may, by proper management, be made to yield any 
 intermediate temperature from 32 to 212 F. 
 
 Every water and liquid bath, whatever its form and the pur- 
 pose to which it is to be applied, should be so constructed that 
 the vaporized portions can, if necessary, be confined within the 
 vessel and prevented from escaping by other outlets than the 
 safety valve. As proximity of the escaping vapor might be in- 
 jurious to the substance under process, the escape-pipe should 
 have its exit six or eight inches distant from the sides of the 
 vessel. 
 
 Any two vessels of different diameters, one within the other, 
 may form a water-bath, provided the intervening space at the 
 bottom and sides is sufficient to contain the requisite amount 
 of water. Straw at the bottom and sides is an excellent means 
 of steadying the inner vessel and preventing direct contact of its 
 surface with the more highly heated bottom of the outer vessel, a, 
 result which'would cause the temperature of the inner vessel to 
 be raised above that of the surrounding water. 
 
 Fig. 199. 
 
 A regularly constructed water-bath of convenient form is shown 
 in Fig. 199. "A is a vessel containing the water, a the inner 
 
268 CONSTRUCTION OF WATER-BATH. 
 
 flange for the support of the evaporating dish B, or different cir- 
 cular rings when smaller dishes are employed, d is a tube fur- 
 nished with a stop-cock for the escape of the steam, which, in 
 some cases, requires to be carried still farther off by an additional 
 tube attached to it. The whole apparatus may be heated either 
 by a gas stove or on a charcoal furnace. The water-bath is filled 
 about half full with water. It will be seen that water-baths with 
 cover act more on the principle of steam-baths as soon as the 
 quantity of water which they contain is small. Care must be 
 taken always to replenish the evaporating water by adding fresh, 
 otherwise not only the experiment may be ruined, but the bath 
 itself become seriously injured." 
 
 Large tin cups make excellent water-baths for flasks and tall 
 vessels. The bottom of the flasks may rest upon small straw 
 rings which prevent contact with the heated tin, and serve also to 
 steady them. The holes in the lid for the protrusion of the necks 
 of the flasks also assist in this latter respect. 
 
 A very convenient little bath for small ope- 
 rations, is shown in Fig. 200. It consists of 
 a copper capsule #, with a ledge around its in- 
 terior circumference as a rest or support for the 
 vessel to be heated. In order that it may be 
 applicable to capsules of various sizes, its top is 
 fitted with a series of thick flat copper rings, 
 which afford the power of decreasing the diameter of the outer 
 capsule to suit that of the vessel to be heated. 
 
 The whole diameter of the outer vessel is about 7 inches, and 
 when all the rings are placed upon the top the opening in the 
 centre is about 1 inch, but by withdrawing one at a time the size 
 of the mouth can be increased gradually from 1 to 6J inches, and 
 adapted to any vessel of intermediate size. It would be well to 
 have a small tube projecting from the side, so as to answer at the 
 same time the purpose of a handle, and of an exit pipe for the 
 waste vapor. 
 
 This apparatus, as is seen in the figure, is mounted upon a 
 tripod 5, a convenient support when the small spirit-lamp is used 
 to heat the water. When a stronger heat is required, it can be 
 detached and mounted upon a larger support, and placed over 
 
SALINE BATHS. 
 
 269 
 
 Fig. 201. 
 
 Fig. 202. 
 
 the gas or Berzelius lamp. Fig. 201 represents the apparatus 
 without the tripod and with handles. 
 
 A porcelain or tin plate placed upon 
 the top of this bath renders it very con- 
 venient for drying small filters, precipi- 
 tates, &c. By increasing the circumfer- 
 ence of the bath so that it may have a 
 broad top, and by piercing the latter with 
 circular holes of various diameters, we 
 obtain a means of heating several capsules of different sizes at the 
 same time. 
 
 For holding test tubes in upright position, either in sand or 
 water-bath, a support of the form shown by 
 Fig. 202 will be found both convenient and 
 serviceable. 
 
 The still, Figs. 18, 25, without its head, 
 makes an excellent water-bath for large 
 operations. 
 
 Saline baths. The substitution of saline 
 solutions for water aifords a means of ob- 
 taining temperatures higher than the boil- 
 ing-point of that liquid. This kind of bath 
 is very useful for digestions and many 
 other operations. The saturation of the 
 water with salts raises its point of ebulli- 
 tion, but in practice it is necessary to use weaker solutions, other- 
 wise the evaporation of the water would be continually causing 
 the deposition of the salt and the solidification of the liquid to 
 the great inconvenience of the experimenter. 
 
 The following table exhibits the boiling-points of the saturated 
 solution of the salts most generally employed for this purpose. 
 
 BOILING-POINTS OF SATURATED SOLUTIONS, 
 
 Alum, 
 
 Muriate of ammonia, 
 Oxalate of ammonia, 
 Tartrate of ammonia, 
 Chloride of barium, 
 Nitrate of baryta, 
 Acetate of copper, 
 
 220 
 
 237 
 
 218 
 
 230 
 
 220 
 
 214 
 
 214 
 
 Sulphate of copper, . 216 
 
 Acetate of lead, . .212 
 
 Chloride of calcium, . 355 
 
 Sulphate of magnesia, . . 222 
 
 Cream of tartar, . , 214 
 
 Chloride of sodium, . . 227 
 
 Tartrate of potassa, ''*.'=* 224 
 
270 METALLIC AND OIL BATHS. 
 
 Sulphate of soda, . . 213 C 
 
 Nitrate lime, ". - . 303 
 
 Carbonate of potassa, . . 275 
 
 Chloride of zinc, . ' . 320 
 
 Rochelle salt, . . . 246 
 
 Sulphate of nickel, . 235 
 
 Chlorate of potassa, . .219 
 
 Nitrate of potassa, . . 238 
 
 Quadroxalate of potassa, . 220 
 
 Acetate of soda, .:?, f V- '3 256 
 
 Nitrate of soda, ' ,. . 249 
 
 Biborate of soda, . ,. 222 
 
 Carbonate of soda, . . . 220 
 
 Phosphate of soda, . . 222 
 
 Nitrate of strontia, }'**-* . 224 
 
 Sulphate of zinc, . ,^| 220 
 
 Boracic aaid, . . .218 
 
 Chloride of zinc is available at temperatures below 320 F., at 
 which degree it gives off fumes of chlorhydric acid and becomes 
 unsuitable as a medium for the communication of heat. A layer 
 of oil retards the evaporation of the water and promotes the ele- 
 vation of the temperature of the solution. 
 
 The selection of the salt for the bath must be with regard to 
 economy and the nature of the material of the vessels. Corrosive 
 solutions should only be used in those vessels upon which they are 
 without action. The construction of the bath is similar to that 
 shown in Fig. 199. 
 
 Metallic Baths. These baths are only convenient for small 
 operations, because of the difficulty of supporting the weight of 
 a large amount of metal, and of keeping the heating vessels im- 
 mersed in it. They furnish temperatures higher than either of 
 the preceding, and for greater safety must be heated in cast-iron 
 vessels of form suitable to the experiment. 
 
 Mercury would be a convenient menstruum, if it was lighter 
 and emitted, when highly heated, less noxious fumes. On these 
 accounts it is but rarely used, and only in test tubes for heating 
 still smaller tubes. The fusible alloy, composed of eight parts 
 of bismuth, five of lead, and three of tin, forms an excellent 
 metallic bath. It melts below 212 F., and affords very high 
 temperatures, for though it oxidizes upon the surface as its tem- 
 perature is increased, it will bear a white heat without emitting 
 vapors. Tin melting at 441 F. and lead at 609 F., are both 
 available for a temperature above their fusing-points. 
 
 Oil Baths. Oils in ebullition throw off a very disagreeable 
 vapor, but are otherwise convenient for furnishing temperatures 
 corresponding with and below their boiling-point. Care should 
 be taken not to apply heat sufficient for their decomposition. 
 Even at low temperatures they have the advantage over water, 
 
THE MODE OF PRODUCING LOW TEMPERATURES. 271 
 
 of losing less by evaporation and of affording facility in regula- 
 ting the temperature. The oil should, before its transfer to the 
 bath, be heated in an iron capsule for several hours, to expel 
 moisture. The bath consists of a porcelain lined or metallic 
 jacket, of construction exactly similar to that of the water-bath. 
 It affords a temperature of 570 F. A THERMOMETER is neces- 
 sary for noting the temperature of the bath, to which end its 
 bulb must be kept immersed in the oil. 
 
 Sand-bath. This bath is of more general application for labo- 
 ratory purposes than either of the others. Its different forms and 
 their appropriate uses have already been fully described at pp. 30, 
 33, 40, 66, Figs. 9, 11 } 17, 43. Sand is used because it is a better 
 resistant of sudden changes of temperature, and affords a uniform 
 heat, greater or less, as may be required, than that of the water- 
 baths. Magnesia and ashes are sometimes substituted, but they 
 are too apt to be driven about by slight currents of air ; the 
 former is only used as a bed for platinum or porcelain crucibles, 
 which are to be enclosed in Hessian crucibles and ignited. 
 
 A sand-bath may be readily constructed by filling an iron pot 
 with sand and placing it upon the charcoal furnace, Fig. 124, or 
 upon the top of the stove which heats the apartment, or over a 
 gas burner. It is then ready to receive glass or porcelain vessels 
 in which the processes of evaporation, digestion, or distillation 
 may be carried on. Care must be observed, in heating the sand, 
 not to let it exceed the required degree, for otherwise time will 
 be lost in waiting for its fall, as it cools very slowly. 
 
 CHAPTER XIII. 
 
 THE MODE OF PRODUCING LOW TEMPERATURES. 
 
 THERE are many chemical processes requiring the application 
 of low temperatures ; and, therefore, it is a duty of this work to 
 teach the means of producing cold artificially. It is accomplished 
 by means of freezing mixtures, which are formed of substances 
 
272 THE MODE OF PRODUCING LOW TEMPERATURES. 
 
 having a tendency to liquefy in water or other fluid. The ab- 
 sorption of heat, by the freezing mixture, from the body under 
 process, produces a depression of temperature in the latter, vary- 
 ing as to degree with the nature and proportions of the mixed 
 ingredients. This depression of temperature is incident to the 
 disaggregation of the salt or other matter, and its transition 
 from the solid to the liquid state. The heat thus transferred is 
 regarded as a species of latent heat of fusion of the salt, differing 
 measurably from the latent heat of igneous fusion, and has been 
 termed by Regnault "the latent heat of solution of a salt." 
 
 Ice and salt, for example, when mixed together, produce a cold 
 of 6, owing to the rapid melting of the ice and the subsequent 
 solution of the salt in the cold water: the depression of tempera- 
 ture, in this instance, being due both to the latent heat of solu- 
 tion of the salt and the latent heat of fusion of the ice. 
 
 Freezing or cooling mixtures are necessary for determining the 
 congealing point of fluid substances ; and for this purpose they 
 must surround the vessels containing the latter. When the two 
 have remained sufficiently long in contact to produce the desired 
 result, the temperature of the fluid, at the moment of transition, 
 must be noted by a thermometer, which should be placed in it at 
 the commencement of the experiment. Another thermometer 
 must be simultaneously placed in the freezing mixture, to give 
 assurance that the internal and external temperature are uniform, 
 otherwise the fluid may congeal on the walls of the containing 
 vessel before the interior of the mass has fallen to the proper 
 temperature. 
 
 The ingredients composing them should be previously pulve- 
 rized, and then mixed together without unnecessary delay. 
 
 In very small operations, the vessels to be cooled are refrige- 
 rated by keeping the surfaces moistened with ether, which, vola- 
 tilizing rapidly, abstracts and carries off a large amount of heat. 
 
 Freezing mixtures afford the facility of making ice at all sea- 
 sons ; and a convenient apparatus for this purpose, as well as for 
 cooling bottles and similar vessels, is the so-called " Family Ice- 
 box," represented by the annexed drawings. 
 
 It is composed of a hollow cylinder c, for receiving the refri- 
 gerating vessel I, containing the water to be frozen. Another 
 cylindrical vessel A, with a close bottom, sets in the freezing 
 
THE MODE OF PRODUCING LOW TEMPERATURES. 
 
 273 
 
 mixture, and being fitted with suitable projections, and turned by 
 the winch-handle, agitates the mixture, and maintains a thorough 
 contact of the refrigerating body with the inner and outer vessels. 
 If the hollow vessel be filled with water, the latter freezes like 
 the surrounding water. The space I, and also the cover D of the 
 
 Fig. 203. 
 
 inner cylinder A, are enveloped with raw cotton, which, as a bad 
 conductor, intercepts the heat of the circumambient air. The 
 freezing mixture should be added in three separate portions, to 
 insure its maximum efficiency, and the resulting liquid from each 
 drawn off into the lower vessel v through a lever-cock, before 
 the application of the succeeding portion. The cold water flowing 
 into the receiver v renders the latter a convenient cooling vessel 
 for liquids contained in bottles. Thirty to forty minutes suffice 
 for making a cylinder of ice. 
 
 The following tables by Walker and Karsten present formulae 
 for a variety of freezing mixtures, with the degree of cold which 
 they produce, severally, annexed. 
 
 18 
 
274 
 
 FREEZING MIXTURES. 
 
 TABLE I. Consisting of Frigorific Mixtures, composed of Ice, with Chemical Salts 
 
 and Aoids. 
 
 Thermometer sinks. 
 
 . 2 parts 1 r to _5 c 
 
 . 1 " J 
 
 Mixtures. 
 
 f Snow or pounded ice, 
 1 Muriate of soda, 
 
 ( Snow or pounded ice, . 5 
 
 < Muriate of soda, . . 2 
 
 I Muriate of ammonia, . 1 
 
 f Snow or pounded ice, . 24 
 
 J Muriate of soda, . .10 
 
 j Muriate of ammonia, . 5 
 
 t Nitrate of potash, . . 5 
 
 f Snow or pounded ice, . 12 
 
 I Muriate of soda, . . 5 
 
 (Nitrate of ammonia, . . 5 
 
 f Snow, . ; * . 3 
 
 1 Diluted sulphuric acid,* . 2 
 
 fSnow, . .. . . .8 
 
 | Muriatic acid (concentrated), 5 
 
 D 
 I 
 
 S^ 
 
 to 12 
 
 to 18 
 
 to 25 
 
 ?From +32 to 23 
 I From +32 to 27 
 | From +32 to 30 
 | From +32 to 40 
 I From -f 32 to 50 
 From +32 to 51 
 
 55 
 
 59 
 
 62 
 
 72 
 
 82 
 
 83 
 
 f Snow, .... 7 
 
 1 Concentrated nitrous acid, . 4 
 
 f Snow, .''.- . ' .; . 4 
 
 ( Muriate of lime, . . 5 
 
 (Snow, .... 2 
 
 I Crystallized muriate of lime, 3 
 
 (Snow, ..... 3 
 
 (Potash, .... 4 
 N.B. The reason for the omissions in the last column of this table is, the ther- 
 mometer sinking in these mixtures to the degree mentioned in the preceding 
 column, and never lower, whatever may be the temperature of the materials at 
 mixing. 
 
 TABLE II. Consisting of Frigorific Mixtures, having the power of generating or 
 creating Cold, without the aid of Ice, sufficient for all useful and philosophical 
 purposes, in any part of the world at any season. 
 
 Degree of cold 
 produced. 
 
 40 
 
 Thermometer sinks. 
 
 5 parts. 
 
 5 
 
 16 
 
 5 
 
 5 
 
 8 
 
 [ From + 50 to +10 
 
 From +50 to +4 
 
 Mixtures. 
 
 ( Muriate of ammonia, . 
 \ Nitrate of potash, 
 I Water, . 
 f Muriate of ammonia, 
 j Nitrate of potash, 
 j Sulphate of soda, 
 I Water, . . . .16- 
 
 f Nitrate of ammonia, . . 1 
 
 (Water, .... 1 
 
 f Nitrate of ammonia, . . 1 
 I Carbonate of soda, . . 1 
 
 ( Water, . . . . 1 J 
 
 * Strong acid 2 parts; water or snow 1 part, by weight. 
 
 46 
 
 j From +50 to +4 . 46 
 
 From 4-50 to 7 
 
FREEZING MIXTURES. 
 
 275 
 
 | From -f 50 to 3 . 53 
 
 Mixtures. Thermometer sinks. 
 
 ( Sulphate of soda, . 
 ( Diluted nitrous acid,* 
 f Sulphate of soda, . 
 J Muriate of ammonia, 
 j Nitrate of potash, . 
 I Diluted nitrous acid, . 
 f Sulphate of soda, . 
 < Nitrate of ammonia, . 
 I Diluted nitrous acid, . 
 f Phosphate of soda, . 
 1 Diluted nitrous acid, . 
 (" Phosphate of soda, . 
 X Nitrate of ammonia, . 
 I Diluted nitrous acid, . 
 f Sulphate of soda, . 
 (. Muriatic acid, . . 
 f Sulphate of soda, . 
 ( Diluted sulphuric acid,f 
 
 N. B. If the materials are mixed at a warmer temperature than 
 in the table, the efiect will be proportionately greater; thus, if the 
 of these mixtures be made when the air is -f- 85, it will sink the . 
 
 Degree of cold 
 produced. 
 
 3 parts. 
 
 2 " 
 
 6 " 
 
 4 
 
 2 
 
 4 
 
 6 
 
 5 
 
 4 
 
 9 
 
 4 
 
 9 
 
 6 
 
 4 
 
 8 
 
 5 
 
 5 
 
 4 
 
 60 
 
 64 
 
 62 
 
 . 71 
 
 50 
 
 47 
 
 that expressed 
 most powerful 
 thermometer to 
 
 TABLE III. Consisting of Frigorific Mixtures selected from the foregoing tables 
 and combined so as to increase or extend Cold to the extremest degrees. 
 
 [-From +50 to 10 
 
 From +50 to 14 
 I From +50 to 12 
 
 I From +50 to 21 
 
 1 From +50 to 
 1 From 4 50 to 4. 3 
 
 Thermometer sinks. 
 
 5 parts. 1 
 
 > From to 34 
 
 ^Mixtures. 
 
 f Phosphate of soda, . 
 j Nitrate of ammonia, . 
 I Diluted nitrous acid, . 
 ( Phosphate of soda, . 
 } Nitrate of ammonia, . 
 I- Diluted mixed acids, . 
 ( Snow, . . . 
 ( Diluted nitrous acid, . 
 
 SSnow, ," '.*'''.' 
 Diluted sulphuric acid, 
 Diluted nitrous acid, . 
 (Snow, ... 
 I Diluted sulphuric acid, 
 f Snow, . . , , . 
 \ Muriate of lime, . 
 ( Snow, . . : - 
 ( Muriate of lime, . 
 fSnow, .... 2 
 ( Muriate of lime, . . 3 
 
 * Fuming nitrous acid, 2 parts ; water 1 part, by weight, 
 t Equal weights of strong acid and water. 
 
 From 34 to 50 
 
 From to 46 . 
 
 V From 10 to 56 
 
 j From 20 to 60 
 
 1 From +20 to 48 
 
 From 4-10 to 54 
 
 From 1 5 to 68 
 
 Degree of cold 
 produced. 
 
 34 
 
 16 
 
 46 
 46 
 
 40 
 68 
 64 
 
276 FREEZING MIXTURES. 
 
 Mixtures. Thermometer sinks. 
 
 5 Snow ' ..-. lpart '}FromOto-66 , 66 
 
 < Crystallized muriate of lime, 2 
 
 J SnOW ' ' ' . ' 1 " } From -40 to -73, 33 
 
 C Crystallized muriate of lime, 3 
 
 P n W ', \ ' M' 'in } From -68 to -91, 23 
 c Diluted sulphuric acid, . 10^ u J 
 
 Remarks. The above artificial processes for the production of cold are more 
 effective when the ingredients are first cooled by immersion in other freezing 
 mixtures. In this way Mr. Walker succeeded in producing a cold equal to 100 
 below the zero of Fahrenheit, or 132 below the freezing-point of water. 
 
 The materials in the first column are to be cooled, previously to mixing, to the 
 temperature required, by mixtures taken from either of the preceding tables. 
 
 The following table by Karsten, shows the diminution of temperature in degrees 
 Fah., where 1 pt. of salt is dissolved in 4 pts. water. 
 
 Salts. Degrees of cold. 
 
 Nitrate of lead, 3'4 
 
 " baryta, 3-8 
 
 Common salt, 3'8 
 
 Sulphate of copper, . 4-0 
 
 " potassa, 5-2 
 
 " zinc, 5-6 
 
 " magnesia, 8'1 
 
 Muriate of baryta, . . 8'1 
 
 Sulphate of soda, 14'6 
 
 Nitrate of soda, .. 17-0 
 
 " potassa, 19-1 
 
 Chloride of potassium, 2T3 
 
 Nitrate of ammonia, 25*4 
 
 Muriate of ammonia, 2 7- 3 
 
 The following table, also by Karsten, shows the degrees of cold produced by 
 dissolving 1 pt. of a salt in 4 pts. of a saturated solution of another salt : 
 
 Salts. Sat. solution of. Degrees of cold. 
 
 Sal ammoniac, . . Common salt, . . . . 15 1 
 
 " . . Saltpetre, . . . . 22-7 
 
 Saltpetre, ... Sal ammoniac, . . . 17-5 
 
 " ... Common salt, .... 16-9 
 
 " ... Nitrate of soda, . . . 12-7 
 
 " ... baryta, . . . 17-5 
 
 ... " lead, . . . 17-1 
 
 Glauber's salt, . . Common salt, . . . . 8- 5 
 
 Common salt, . . Blue vitriol, .... 7*4 
 
 Nitrate of soda, . . Sal ammoniac, v . . ' . . 16-4 
 
 " . . Saltpetre, . ' ^ , . . 16-6 
 
FUSION. 277 
 
 Salts. 
 
 Sat. solution of. 
 
 Degrees of cold. 
 
 Nitrate of soda, . 
 
 Common salt, . 
 
 . 
 
 14-0 
 
 41 (C 
 
 Muriate of baryta, . 
 
 . 
 
 14-9 
 
 (C U 
 
 Nitrate of lead, ' . 
 
 . 
 
 14-4 
 
 Nitrate of baryta, 
 
 Saltpetre, 
 
 . 
 
 1-35 
 
 Sulphate of zinc, 
 
 .;.>-. Sulphate of potassa, 
 
 . 
 
 3-1 
 
 The following table, by Karsten, of 1 pt. salt in 4 pts. of a saturated solution 
 shows an increase of temperature : 
 
 Salts. Sat. solution of. Degrees of heat. 
 
 Common salt, . . Sal ammoniac, . . . 8-2 
 
 " " Glauber's salt, . \ 3 ' 10 
 
 " " Y/ '* Saltpetre, .' '/* : . 'V 1-35 
 
 " " ; .-' Nitrate of soda, , ' f< '/<' 6-8 
 
 Muriate of baryta, . " " ... 1-15 
 
 By mingling solid lead amalgam with solid bismuth amalgam, whereby they 
 become liquid, Orioli obtained 39-6 of cold. Dobereiner mixed 204 pts. lead 
 amalgam (103 lead -f- 101 mercury) with 172 pts. bismuth amalgam (71 bismuth 
 -|- 101 mercury), and obtained a diminution of from 68 to 30-2; and by adding 
 to the same 202 pts. more of mercury, the temperature fell to 17-6. By dissolving 
 the powders of 59 pts. tin. 103-5 pts. lead, and 182 pts. bismuth, in 808 pts. mer- 
 cury, the thermometer falls from 63-5 to 14. 
 
 CHAPTER XIV. 
 
 FUSION. 
 
 THE liquefaction of bodies by heat, a preliminary step to many 
 processes, is termed fusion. Igneous fusion applies to the melting 
 of anhydrous substances, and aqueous fusion to the liquefaction 
 of a salt in its water of crystallization. 
 
 The modes of performing the process, and the material and 
 form of the apparatus employed, vary with the nature of the 
 substance to be acted upon. The chief point to be attended to is 
 the selection of such containing vessels as are not injuriously 
 affected by the fused substances, and which do not themselves 
 react upon their contents. 
 
 The implements for fusion are called crucibles, the smaller of 
 which, for the less refractory substances, may be heated over the 
 GAS or SPIRIT LAMP. To effect the liquefaction of bodies diffi- 
 
278 CRUCIBLES. 
 
 cultly fusible, or of large quantities of matter, a FURNACE is 
 requisite. 
 
 The size of the crucible should be proportional to the quantity 
 of matter to be heated in it. It is best that its capacity should 
 be no greater than sufficient for the contained substance with 
 enough margin to allow for swelling or foaming. 
 
 CRUCIBLES. A crucible, to be available for any and every 
 operation, should possess the quality of compactness, in order to 
 resist the corrosive action of fused substances, the permeability 
 of gases and liquids, the fusing power of intense heat, and the 
 tendency to fracture by sudden changes of temperature. 
 
 It is impossible to combine all these requisites in any one kind 
 of crucible. 
 
 The materials of which crucibles are formed are either pure 
 clay, or clay mixed with charcoal, quartz, graphite, or coke, to 
 render it more refractory. Black lead, porcelain, silver, and pla- 
 tinum, have each and all their appropriate application. 
 
 Clay Crucible&.-r-The Hessian and French crucibles are those 
 
 Fig. 204. f tn i s description, which are most used. The 
 Hessian, so called from the place of their manu- 
 facture in Germany, are either in the form of 
 a tapering cylinder or triangular, and are that 
 kind of crucible most commonly found in our drug 
 shops. They are met with in nests of a half dozen 
 or more, gradually increasing in size from the 
 smallest (of an ounce) to the largest, of pint or quart capacity. 
 
 They are grayish yellow or whitish, rough to the touch, and 
 should give a clear ring when held by the bottom and sounded on 
 the sides. Being hard and impermeable, they are very useful 
 for rough fusions ; but the silica which they contain renders them 
 unfit for metallic oxides, with which at high heat it combines. 
 
 The Hessian crucibles require careful usage, as they are liable 
 to be fractured by even slight changes of temperature. There- 
 fore, notwithstanding their great cheapness, the London or French 
 crucibles are more preferable for nice operations. 
 
 The Loridon crucibles are very refractory, regularly formed, 
 with smooth surfaces, and will endure a very high heat. 
 
 The French crucibles, Fig. 205, which are manufactured by 
 
1 
 
 PORCELAIN CRUCIBLES. 279 
 
 Beaufaye, of Paris, are said to be far superior to Fig. 205. 
 either of the preceding. They are whitish, well 
 shaped, and smooth throughout, and being nearly 
 free from oxide of iron, and less rich in silica, are 
 applicable for the fusion of nearly all substances 
 except certain salts, which, owing to the porosity of 
 the crucible material, are readily absorbed. 
 
 Being capable of supporting extreme heat as well 
 as sudden changes of temperature, they are very useful for the 
 reduction of oxides and fusion of metals. Borax, glass, and 
 similar substances, remain perfectly colorless when melted in 
 these crucibles. 
 
 The mixture of graphite or coke with the clay, which is found 
 in those of Austin's make, renders them capable of better sup- 
 porting the softening influence of the wind furnace and with- 
 standing the most sudden changes of temperature, but the pro- 
 portion of the latter must not exceed 33 per cent., otherwise 
 its combustion by the fire will leave the crucible porous and 
 fragile. 
 
 As metallic oxides are reducible when hot, by contact with 
 carbonaceous matter, these crucibles, when used for heating those 
 substances, should be lined with a thick coat of clay paste and 
 dried. 
 
 Charcoal is the only proper fuel for earthen crucibles, as coke 
 is apt to form scoriae, which attach to the crucible and impede 
 the draught. 
 
 Black Lead Crucibles. Blue Pots. Black lead or plumbago, 
 when mixed with one-fourth of its weight of refractory clay, 
 becomes capable of supporting intense heat and sudden changes 
 of temperature. The chief use of crucibles made of this sub- 
 stance is in metallurgy, for the purposes of which their smooth 
 surface admirably adapts them. They are not sufficiently com- 
 pact for the fusion of salts. 
 
 Porcelain Crucibles. Crucibles of this material are very neat 
 implements, but by reason of their incapability of resisting even 
 slight changes of temperature, are only used for purposes to which 
 those of more refractory material are for other reasons not 
 adapted. For heating over the lamp they must be small and 
 thin. In analytic and nice operations they replace platinum in 
 
280 
 
 PORCELAIN CRUCIBLES. 
 
 many processes in which the contents act upon that metal, for 
 example, in igniting plumbic precipitates, melting metallic oxides 
 with sulphobases, preparing enamels, and heating metallic oxides, 
 which are reduced easily in contact with platinum. 
 
 The crucibles, Figs. 206, 207, used directly over the lamp, 
 should never exceed an ounce or two in 
 capacity, for even with the most careful 
 management it will be difficult to cool 
 one of larger size gradually enough to 
 prevent its breaking. Berzelius recom- 
 mends their insertion in platinum cru- 
 cibles as a means of diminishing their 
 fragility. The French porcelain being 
 very thin and light, and a better supporter of sudden changes of 
 heat, is preferable to the Berlin for small crucibles. 
 
 The impermeability and cleanliness of these crucibles, render 
 them very convenient for the fusion of certain nice substances, 
 such as nitrate of silver, potassa, &c., in large quantities, and as 
 it is impracticable to have a very large platinum crucible in 
 private laboratories, one of porcelain is substituted. These large 
 crucibles, made with covers, may be of either of the forms, Figs. 
 208, 209, 210, and of Berlin porcelain, which is similar to Wedg- 
 wood-ware, and heavier and cheaper than the French. 
 
 Fig. 208. 
 
 Fig. 209. 
 
 Fig. 210. 
 
 Fig. 211. 
 
 The large crucibles, varying in size from two to six inches in 
 height, and from one to four inches in diameter, may be entirely 
 biscuit, or else glazed only internally, and if heated over the fire 
 require to be enclosed in a refractory fire-clay case, as shown in 
 Fig. 211. This case is equally useful for platinum or silver cru- 
 cibles (Figs. 214, 215), as it gives them a proper elevation above 
 the grate, and prevents contact with the coals. 
 
IRON AND SILVER CRUCIBLES. 281 
 
 For the heating of more readily fusible substances they may 
 be imbedded in a sand-bath and heated up gradually. If allowed 
 to remain in the bath until it has cooled, the liability of fracture 
 from sudden refrigeration will be diminished. 
 
 Some of the crucibles have duplicate covers, one of which is 
 perforated and used to facilitate the escape of the gaseous matter 
 generated during certain processes. 
 
 Metallic Crucibles. Cast and plate iron, silver, and platinum, 
 are all used as materials for crucibles. 
 
 Iron Crucibles. For the fusion of silicates and certain sele- 
 niurets, sulphurets, and other substances, iron crucibles are very 
 convenient. An exterior coating of clay is requisite to protect 
 them from the oxidizing action of the air, to which they are sub- 
 jected at high temperatures. The same object may be effected 
 by inserting them in clay crucibles. When, however, the heating 
 is not of long duration nor intense, they may be used naked. 
 
 Those of wrought iron, Fig. 212, are struck up from a single 
 piece of thick sheet metal. 
 
 Fig. 212. Fig. 213. 
 
 Cast-iron crucibles, Fig. 213, are cheaper, and equally as good 
 as wrought iron for medium temperatures, but they must be 
 turned smooth interiorly. 
 
 As some of the constituents of stove coal exert a chemical 
 action upon metal, the only proper fuel is charcoal, when furnaces 
 are used for heating the crucibles. 
 
 Silver Crucibles. Silver crucibles are but rarely used, save 
 for the fusion of potassa, soda, and for the preparation of caustic 
 baryta from the nitrate. For most operations they are well 
 replaced by platinum. For acid substances their use is improper. 
 The spirit or gas lamp is the heating apparatus, but the heat must 
 
282 PLATINUM CRUCIBLES. 
 
 not be too high nor of too long duration, for the silver is apt to 
 become brittle in spots as it assumes a crystalline form under the 
 influence of long-continued red heat. 
 
 Platinum Crucibles. Platinum crucibles are of more general 
 application than those of any other material. They are very 
 tough and infusible at any heat that can be obtained from the 
 gas or spirit lamp, the almost exclusive means employed for that 
 purpose. As they are liable to become rough at high furnace 
 temperatures, they should, when exposed to such influences, be 
 inserted in an earthen crucible, and surrounded by a bed of 
 magnesia. 
 
 Their strong resistance to the action of chemical reagents ren- 
 p. y 214 ders them indispensable in many opera- 
 
 tions, which it would be difficult other- 
 wise to perform. They vary in size 
 from a fluid-drachm to three or more 
 
 _i L fluid ounces capacity, the latter being 
 
 as large as is necessary for any purpose 
 in a private laboratory. Their form is shown in Figs. 214, 215. 
 The crucibles intended to be heated over the lamp must be of 
 very thin metal, so that they can be weighed, as is often neces- 
 sary, in a delicate balance. To give strength, however, the 
 bottom must be thicker than the sides. Two of the smaller 
 size will be found more useful than one of the larger. In analysis 
 a half ounce crucible is indispensable for the IGNITION of filters. 
 The cover is, as seen in the figure, slightly convex exteriorly, 
 and ledged around the circumference : this form is convenient 
 when the vessel is to be entirely closed when heated ; but in cer- 
 tain operations in the wet way it is reversed, so that the convex 
 side may rest inwardly and return any particles of its contents 
 that may be projected upwards, by a too sudden or intense eleva- 
 tion of temperature. The pin running through its centre is the 
 knob by which it is handled, when cold with the fingers, and when 
 hot with the tongs, Figs. 149, 150. 
 
 Platinum crucibles are also made with covers, in the shape of 
 capsules, as shown by Fig. 215. They are very convenient for 
 small evaporations, and are at the same time made to fit closely 
 or loosely to the body of the crucible, as may be desired. 
 
 Unless the crucibles are made of perfectly pure metal, and are 
 
THE CONSTRUCTION OF CRUCIBLES. 283 
 
 hammered out instead of being turned, their F . 215 
 
 power of enduring strong heats and resisting 
 the action of chemical reagents will be im- 
 paired. The blisters and flaws which appear, 
 after use, are owing to impurity and bad work- 
 manship, and are to be removed by the force 
 of a small hammer. 
 
 When the crucible becomes cracked or per- 
 forated, it can be repaired by welding on a 
 layer of platinum sponge, but it is far better 
 to have it melted up and remodelled by a manufacturer. 
 
 Boiling or hot water loosens adherent saline matters, and fused 
 borax or muriatic acid will remove all stains which do not disap- 
 pear by rubbing with sand or pumice-stone. The use of sharp- 
 pointed instruments will be apt to injure the crucible. 
 
 The experimenter himself can, in any emergency, readily form 
 a crucible out of platinum foil by shaping it with the thumb or a 
 small hammer, in a hemispherical cavity made for the purpose, 
 in a wooden block. 
 
 Berzelius ( Traite de Chimie, vol. viii) gives the following in- 
 structions as to the manner of using platinum crucibles. 
 
 " Dry fusion should never be effected in platinum crucibles : 
 1st. Caustic 'alkalies, nitrates of lime, baryta, or strontia, and 
 alkaline nitrates, always attack the platinum. Alkaline sulphu- 
 rets or sulphates with charcoal are still more injurious. Metals, 
 when heated to their melting-points, alloy with it, and hence 
 lead, tin, antimony, &c., should never be even moderately heated 
 in it. Even their oxides, especially those of copper, lead, bis- 
 muth, and nickel, reduce at a high heat by contact with platinum, 
 particularly if charcoal is present, the two former at a lower 
 temperature than the latter. Gold, silver, copper, and others, 
 can be reddened, but not melted in platinum. Phosphorus or 
 phosphoric acid and carbon readily attack it. Sulphate of lead 
 may be burned off in it with care, but for the chloride, porcelain 
 should be used. 
 
 " Silica may be ignited in platinum, but it combines with sili- 
 cium at a heat beyond redness, and therefore they should always 
 be encased when heated in the fire, otherwise, if in contact, it 
 will abstract it from the coals. 
 
284 DIRECTIONS FOR HEATING CRUCIBLES. 
 
 " Nearly all liquids may be heated in platinum, except they 
 contain chlorine, bromine, iodine, or nitro-muriatic acid. 
 
 " For the fixed alkalies, gold is preferable to either silver or 
 platinum, upon which they have a more or less corrosive action." 
 
 Directions for Heating Crucibles. All the larger and coarser 
 crucibles are heated in FURNACES. Their proper position is an 
 upright one in the centre of the grate, upon a slight elevation. 
 They should be warmed before being placed in the furnace, so as 
 to prevent liability to crack by sudden heating. Ignited coals 
 are then placed at the bottom of the grate and covered with al- 
 ternate layers of unlit coke and charcoal, of nut size, until the 
 crucible is surrounded up to the level of its top with fuel. When 
 the crucible is to be strongly heated, it should be covered and the 
 fuel heaped over its top. In all cases the fire must be gradually 
 raised and steadily kept up, and the furnace only opened when 
 fresh additions of coal are necessary, as it is important that there 
 shall be no variation of temperature in its interior. The dura- 
 tion of the process, and the degree of heat employed, must de- 
 pend upon the nature of the substance under process. 
 
 After the completion of the operation, the crucible should be 
 allowed to cool with the furnace, or if taken out immediately, 
 placed upon a brick or bed of warm sand, otherwise a too sudden 
 change of temperature will cause its fracture. The furnace 
 tongs, Fig. 148, are conveniently shaped for this purpose. 
 
 As it is occasionally necessary to poke the fire in order that 
 the fuel may settle previous to fresh additions, it will be well to 
 give the crucible a firm position upon a stand for the purpose, 
 the half of a fire-brick, for instance, so that in the settling of the 
 coal, there may be no risk of its being upset. When by intense 
 heat its bottom has become welded to the brick, the latter can 
 very readily be detached by a gentle tap of the poker. 
 
 Most of the common crucibles serve only for a single ope- 
 ration. 
 
 Covers may be made by inverting a smaller crucible over the 
 top; or better, by making a dough of Stourbridge clay, and 
 luting it on. The crucible, in the latter case, must not be heated 
 until the cover has dried. These lids have a tendency to retard 
 volatilization, and are necessary to prevent the entrance of fall- 
 ing particles of coal and ashes. For the escape of gaseous 
 
FUSION OF SUBSTANCES UNALTERABLE BY HEAT OR AIR. 285 
 
 matter a small perforation in the centre of the cover is necessary, 
 but in intensely hot fusions all other openings must be closed with 
 
 LUTE. 
 
 The smaller metallic crucibles are almost exclusively heated 
 over LAMPS. They are supported upon wrought iron rings, 
 Figs. 179, 180, the diameter of which may be reduced when 
 necessary, by the use of the wire triangles, Fig. 181, of the re- 
 quired size. 
 
 If the crucibles are very small they may be heated by the 
 mouth blow-pipe. For the larger an Argand, spirit, or gas lamp, 
 Fig. 165, is needed. To hasten the process or to increase the 
 temperature, the table blow-pipe, Figs. 45, 164, is convenient, as 
 it gives a powerful blast. 
 
 The use of the jacket, Fig. 156, is an additional means of still 
 further economizing and increasing the power of the flame. It 
 also diminishes the loss of heat from the crucible by radiation, 
 especially when the latter is covered. In charging the crucibles, 
 the contents should be concentrated into as small a space as pos- 
 sible, and any adherent particles should be brushed from the 
 sides with a feather. When the crucibles are emptied of their 
 fused contents, the melted matter may be made to flow upon a 
 smooth and clean slab of marble, iron, or other proper material, 
 great care being taken that it does not come in contact with 
 any moisture or damp substance. 
 
 Fusion of Substances unalterable by Heat or Air. This class 
 comprises a very large number of substances, among which are 
 the noble metals, &c. The crucible employed should be kept 
 covered as well whilst cooling as heating, and the refrigeration 
 must be gradual, or the molten matter may spirt. There are 
 other metals again, for instance, zinc, lead, tin, antimony, and 
 bismuth, which, at high temperatures, oxidize 'readily upon ex- 
 posure. In such cases it is well, in addition to keeping the 
 vessel closed, to cover the fluid mass with a layer of powdered 
 charcoal. 
 
 When a metal is in process of fusion it is imprudent to make 
 fresh additions without having first heated the material to be 
 added, for the sudden entrance of cold or damp matter into the 
 hot fluid mass will cause the ejection of particles, and perhaps 
 serious inconvenience. 
 
286 FUSION OF SUBSTANCES ALTERABLE BY HEAT OR AIR. 
 
 In the manufacture of alloys the metals should be well incor- 
 porated by occasional stirring. When iron, and indeed manga- 
 nese, cobalt, nickel, and chrome, are being exposed to high degrees 
 of heat, the crucibles must be free from carbonaceous matter, 
 otherwise a combination may ensue at high temperatures. 
 
 Fusion of Substances alterable by Heat. For the treatment 
 of substances which melt below 212 F., the water-bath is conve- 
 nient. The fusion of substances, such as wax, resin, and fat, 
 immiscible with that liquid, may be facilitated by the direct ap- 
 plication of boiling water, as they can be readily removed from 
 the surface, to which they rise, with a ladle or syphon whilst hot, 
 or in a mass if allowed to cool. 
 
 Substances requiring a temperature at or below 550 for their 
 fusion, may be melted in an oil-bath. 
 
 Alloys containing volatile metals should be heated as quickly 
 as possible. 
 
 Certain substances which volatilize at low temperatures re- 
 quire to be fused in closed vessels. Iodine and arsenic are 
 examples. 
 
 A tube of glass, porcelain, or metal, according to the nature 
 of the substance, is the best form of apparatus for this purpose. 
 It should be rounded at one end, and after the introduction of 
 the substance, closed at the other over the blow-pipe. The tube 
 must be heated throughout its length. 
 
 Fusion of Bodies alterable by Air. This class of substances 
 is melted in seclusion, the air being shut out by means of an 
 intermedium of liquid, powder, or fusible matter. Thus potas- 
 sium is liquefied under naphtha, phosphorus under water, and 
 certain other substances in powdered charcoal. 
 
 The covers of the crucibles in these cases must be tightly luted, 
 so that all openings may be closed. 
 
 Fusion of difficultly fusible Substances. All substances which 
 resist the fusing power of furnaces, are to be subjected to the 
 more intense action of the HYDRO-OXYGEN BLOW-PIPE, or Bun- 
 sen's battery. One or other of these latter means will prove 
 effective, in all possible cases. 
 
 Fusing-points. The usual mode of determining the point at 
 which a substance fuses, is to place a thermometer in it whilst 
 fluid, and note the degree at which solidification ensues. There 
 
IGNITION OF FILTERS. 287 
 
 are, however, according to Brodie (Mechanic's Magazine, 1854), 
 some substances whose points of fusion so closely approximate 
 the degree at which they assume allatropic conditions, that they 
 require a modification of the above plan, for such change of state 
 is always accompanied with evolution or absorption of heat. In 
 these cases the substance is to be divided into small particles, 
 placed in a thin glass tube, when its melting-point is below that 
 of glass, and immersed in a bath of boiling dilute sulphuric acid 
 or other suitable liquid. At the moment the contents of the tube 
 melts, the temperature of the bath is to be noted by a thermo- 
 meter, and recorded as the fusing-point of the substance under 
 experiment. 
 
 CHAPTER XV. 
 
 IGNITION. 
 
 SUBSTANCES frequently require to be ignited to redness, either 
 as the sole process of their preparation, or as a preliminary step 
 to subsequent operations. 
 
 Ignition of Filters. In analyses, the filters containing the in- 
 soluble or precipitated substances which are to be estimated are 
 ignited or "burned off," to expel carbonaceous and volatile 
 matters before being weighed. The implements for this purpose 
 are porcelain or platinum crucibles, either having their appro- 
 priate applications. 
 
 As it is necessary that the filter should be wholly or partially 
 dry, it must be carefully removed from the funnel, so as not to 
 lose a particle of its contents, compressed between the folds of 
 bibulous paper, and, further, dried in a capsule over a sand or 
 water bath, or in a drying stove (DESICCATION), at a temperature 
 of about 200 F. or less. The dried filter and contents are then 
 to be transferred to the crucible, which must be previously weighed. 
 The transfer must be made without the loss of the least particle, 
 and for this purpose the crucible may be placed upon a sheet of 
 glazed white paper, so that any particles that accidentally fall in 
 the act of emptying the filter may be preserved. The filter, 
 after having been freed as much as possible from the adherent 
 
288 IGNITION OF FILTERS. 
 
 precipitate by gently rubbing the sides together between the 
 thumb and forefinger, is finally placed in the crucible with its 
 contents being folded loosely and laid at the top. The force used 
 for this purpose must not be sufficient to abrade the paper, other- 
 wise the matter will reach the fingers, and a loss thus be occa- 
 sioned by adherence. The crucible is then heated cautiously and 
 gradually over the spirit or gas lamp, Fig. 141, the flame of 
 which may be urged by the blast. For the first few moments the 
 vessel should remain covered, for fear of loss by decrepitation, but 
 as soon as it becomes red hot the lid may be wholly or partially 
 removed, and the crucible inclined, as at Fig. 216. This position 
 promotes free draught and the complete and rapid 
 Fig. 216. incineration of the filter. This being done, the cover 
 is replaced, the crucible allowed to cool, and then 
 weighed. The weight of the crucible and that of 
 the ashes of the filter, which latter has been pre- 
 viously determined by the incineration of filters of different sizes, 
 deducted from the total weight, gives the weight of the ignited 
 precipitate. 
 
 The above directions apply to precipitates which are not alter- 
 able by being burned with the filter. When, however, the matter 
 is preserved free of ashes for use or further examination, or is 
 liable to be reduced or otherwise changed by the carbon of the 
 filter, the latter and its contents must be ignited separately. In 
 
 Fig. 217. 
 
 such cases, the drying of the filter and the detaching of its con- 
 tents are accomplished as already explained. The contents are 
 
IGNITION OF FILTERS. 289 
 
 heated in a platinum crucible as usual, but the empty filter, after 
 having been freed as much as possible from adhering particles of 
 the dry contents, is incinerated in another way, originally sug- 
 gested by Bunsen. The necessary manipulation consists in 
 placing the filter upon a sheet of white paper, doubling over its 
 circumference first at the sides and then at the ends, so as to 
 guard against the possibility of any loss of matter, and finally 
 rolling it up into a tight cylinder. This cylinder is next 
 tightly wrapped with one end of a platinum wire, and held over 
 the flame of an alcohol lamp, as shown by the drawing, until the 
 filter has become thoroughly incinerated. The original volume 
 of the filter having, of course, largely contracted, from loss of 
 matter by the heating, it will easily fall from its position in the 
 platinum wire-coil holder, when the latter is held over the crucible 
 or its capsule cover, accordingly as it may be desirable to weigh 
 the filter ash portion and the pure precipitate jointly or sepa- 
 rately. 
 
 The greatest possible care must be observed in analytical ex- 
 periments to prevent the least loss of the precipitate. The cru- 
 cible must, moreover, in all cases, be cooled under a bell wherein 
 is a vessel containing some hygroscopic substance, so as to pro- 
 vide against error from absorption of moisture previous to the 
 weighing. 
 
 When substances are to be ignited for the determination of 
 their hygroscopic, volatile, or organic matter, heat should be very 
 gradually applied, without the blast, and to a limited degree. In 
 these instances, the crucible should be weighed first, so that the 
 loss sustained by a given weight of its contents, during ignition, 
 may be ascertained in one weighing, merely by subtracting the 
 weight of the crucible and contents after ignition from the com- 
 bined weight of the two before the same process. The loss gives 
 the amount of volatile matter. 
 
 In analyses of coals, the moisture can be determined by heat- 
 ing the crucible in a hot sand-bath, or very gently over a low 
 flame. After the loss thus occasioned is determined by weighing, 
 the amount of carbon may be ascertained by subjecting the cru- 
 cible and contents to a much higher heat. 
 
 When substances are to be exposed to heat, the crucible and 
 contents must likewise be weighed separately before ignition. 
 
290 IGNITION WITH FLUXES. 
 
 The loss of weigtit gives the amount of volatile matter driven- off. 
 The ignited matter can then be removed from the crucible by hot 
 water alone or acidulated. 
 
 Scoriae may be removed from platinum crucibles- by covering 
 them with a paste of borax and carbonate of soda, heating them 
 to redness, and when cold, dissolving out the saline matter with 
 boiling water. A repetition of the process is necessary to 
 brighten the crucible perfectly if it had been very dirty. 
 
 Ignition of Bodies in Vapors. If it be desired to heat a fixed, 
 substance in the vapor of any body, which is solid or liquid at 
 ordinary temperatures, the latter may be put into a tube closed 
 at one end, or into a small flask with a long neck, and then be 
 heated until it is wholly vaporized. The substance is to be 
 introduced into the tube, and heated in the vapor at any desired 
 temperature. Thus, to show the affinity of sulphur for copper, 
 the former is heated until its vapor fills the whole flask, when 
 slips of copper foil let down into it immediately ignite on com- 
 bining with the sulphur. When a tube is used it may be held in 
 any inclined position, but a flask should be nearly vertical. 
 
 Ignition with Fluxes. Fluxes are certain substances, usually 
 saline, mixed with other bodies in order to promote their fusion 
 or decomposition by heat, and to render them more soluble in 
 water and acids. All ignitions with fluxes in experimental ope- 
 rations are performed in crucibles over the spirit-lamp or furnace 
 fire, and for the fluxions of those substances in which there is no 
 reducible metallic oxide, platinum is by far the best material. 
 
 The process is particularly useful in analysis of the sulphurets, 
 of alkaline earths, of many silicates, and other obstinate com- 
 pounds, and also in metallic operations. 
 
 The principal objects of fluxing are : 
 
 " 1. To cause the fusion of a body, either difficultly fusible, or 
 infusible by itself. 
 
 " 2. To fuse foreign substances mixed with a metal, in order to 
 separate the latter by its difference of specific gravity. 
 
 " 3. To destroy a compound into which an oxide enters, and 
 which prevents the oxide being reduced by charcoal. The sili- 
 cate of zinc, for instance, yields no metallic zinc with charcoal, 
 unless it be mixed with a flux capable of combining with the 
 silica. 
 
IGNITION WITH FLUXES. 291 
 
 "4. To prevent the formation of certain alloys, and conse- 
 quently the combination of some metals with others, as in the 
 case of a mixture of the oxides of manganese and iron with a 
 suitable flux, the iron is obtained in a state of purity, whereas if 
 no flux had been added, an alloy would have been obtained. 
 Gold and silver can be separated from many other metals by 
 means of a flux. 
 
 " 5. To scorify some of the metals contained in the substance 
 to be assayed, and obtain the others alloyed with a metal con- 
 tained in the flux, as gold or silver with lead. 
 
 " 6. And lastly, a flux may be employed to obtain a single 
 button of metal, which otherwise would be obtained in globules." 
 
 Fluxes, as well as the substances to be fluxed, must be reduced 
 to the finest state of comminution previous to mixture. 
 
 When the mixture is of a frothing nature, it is best to add it 
 to the crucible piecemeal, and to heat it gradually, so as to save 
 the loss caused by ejection of particles. After the whole has 
 been placed in the crucible^ the heat may be raised and main- 
 tained until perfect fusion and the completion of the process. 
 
 The mixing of the charge is done with glass rods or platinum 
 wires, and the containing crucible must be of sufficient capacity 
 to prevent loss by the ejection of particles. The flux should be 
 rather in excess. In the fluxing of substances which evolve gases, 
 the cover of the crucible should be laid on loosely ; but in those 
 experiments requiring the use of a furnace, the crucible must be 
 close and tight. The Russian or other similar lamp will produce 
 sufficient heat for ordinary fluxions ; and Barren's furnace will 
 serve for the more refractory. When a platinum crucible is 
 heated in a blast or common furnace, it should be imbedded in a 
 Hessian or iron crucible lined with magnesia, otherwise it will be 
 damaged. 
 
 Fluxes are divided into non-metallic and metallic fluxes. 
 
 NON-METALLIC FLUXES. (Berthier, Ussaispar la voie Seclie.} 
 Silica is employed frequently to cause the fusion of some 
 gangues in assays made at an elevated temperature. Silica com- 
 bines with all the bases, and forms with them bodies termed 
 silicates, which are more or less fusible. 
 
 Lime, Magnesia, and Alumina. It is known that no simple 
 silicate is readily fusible, so that lime, magnesia, or alumina are 
 
292 NON-METALLIC FLUXES. 
 
 employed, according to circumstances, to reduce a simple silicate 
 to such a condition that it will readily fuse in an assay furnace. 
 Sometimes, to attain this end, it is requisite to use all the above- 
 mentioned earths, for experience has proved that, as a general 
 thing, a mixed or double silicate fuses more readily and flows 
 freer than a simple silicate. 
 
 Baryta. Hydrate of baryta fuses at a low red heat, and with- 
 out loss of its water of crystallization, and for the first reason is 
 preferable to either the carbonate or nitrate. It is used in silver 
 or platinum crucibles, and when silicates are to be tested for 
 alkalies. The silicates of baryta, however, fuse with difficulty, 
 and are sluggish. 
 
 Glass is a very useful flux in certain iron assays. The kind 
 employed must not contain lead. 
 
 Boracie Acid. The native boracic acid, after fusion and pul- 
 verization, is to be employed whenever the use of this acid is 
 indicated. It ought to be kept in well-stoppered bottles. 
 
 Boracic acid has the property of forming with silica and all 
 the bases very fusible compounds, and is from this cause a very 
 universal flux. Nevertheless, there is an inconvenience attached 
 to its use ; it is very volatile, so that sometimes the greater part 
 employed in an assay sublimes before it has had time to perform 
 its office. 
 
 Borax (Biborate of Soda) is an excellent and nearly universal 
 flux, because it has the property of forming, like boracic acid, 
 fusible compounds with silica and nearly all the bases, and is pre- 
 ferable to that acid because it is much less volatile. 
 
 It may be used at a high or low temperature. In the first 
 case, it is employed in the assay of gold and silver, because it 
 fuses and combines with most metallic oxides, or in obtaining a 
 regulus, that is to say, to separate the metals, their arseniurets 
 and sulphurets, from any stony matter with which they may be 
 mixed, because this salt is neither oxidizing nor desulphurizing. 
 In the second place, it is employed in the assay of iron and tin 
 ores, as in the presence of charcoal it retains but traces of their 
 oxides, and, indeed, much less than generally remains with the 
 silicates. 
 
 When borax is heated it fuses in its water of crystallization, 
 and undergoes an enormous increase of volume ; at a higher tern- 
 
NON-METALLIC FLUXES. 293 
 
 perature, it fuses and forms a transparent glass, which becomes 
 dull on the surface by exposure to air. Only the fused vitrified 
 borax ought to be used in assays. It must be reduced to powder, 
 and kept in well-closed vessels. 
 
 Fluor Spar (Fluoride of Calcium) is rarely employed in as- 
 says, but in certain cases is an excellent flux, especially where 
 sulphates are present, with many of which it forms very fusible 
 compounds. The best proportions are about equal equivalents 
 of the spar and the anhydrous sulphates of alkali, lime, and oxide 
 of lead; but for the sulphate of baryta, two eqs. of the spar for 
 one eq. of the sulphate. 
 
 It likewise assists in fluxing silicates, partly by direct union 
 with them, and partly by yielding fluosilicic gas, and leaving lime 
 to unite with silica. 
 
 Carbonate of Potasli and Carbonate of Soda. It has been 
 already proved that they possess oxidizing and desulphurizing 
 power ; they will now be considered as fluxes. 
 
 They are decomposed in the dry way by silica and the silicates, 
 with the separation of carbonic acid. The presence of charcoal 
 much facilitates this decomposition. 
 
 The silicates of potassa and soda fuse readily and flow freely. 
 
 They form fusible compounds with the greater part of the 
 metallic oxides*; in these combinations the oxide replaces a cer- 
 tain quantity of carbonic acid ; but these compounds are not 
 stable, they are decomposed by carbon, which reduces the oxide, 
 or by water, which dissolves the alkali. 
 
 On account of their great fusibility, the alkaline carbonates 
 can retain in suspension, without losing their fluidity, a large 
 proportion of pulverized infusible substances, as an earth, char- 
 coal, &c. 
 
 The alkaline carbonates ought to be deprived of their water 
 of crystallization for assaying purposes ; in fact, it would be 
 better to fuse them before use. They must, in all cases, be kept 
 in well-stoppered vessels. 
 
 They may be used indifferently, but carbonate of soda is to be 
 preferred, as it does not deliquesce. 
 
 A mixture of both is far preferable to either alone, and, more- 
 over, requires a lower heat for its fusion. The proper propor- 
 tions are ten parts of effloresced carbonate of soda and thirteen 
 
294 BLACK FLUX AND ITS EQUIVALENTS. 
 
 parts of dry carbonate of potassa. The two are to be intimately 
 incorporated by trituration, and the mixture kept in stoppered 
 bottles. This flux is the one of most general application. 
 
 The alkaline carbonates of commerce always contain sulphates 
 and chlorides. In ordinary cases, this causes no inconvenience, 
 but there are circumstances under which the presence of sulphuric 
 acid would be injurious. 
 
 Carbonate of potash can readily be procured free from sulphate 
 and chloride by means of nitre and charcoal, as follows : Pul- 
 verize roughly 6 parts of pure nitre, and mix them with 1 part of 
 charcoal ; then project the mixture spoonful by spoonful into a 
 red-hot iron crucible. The projection of each spoonful is accom- 
 panied by a vivid deflagration, and carbonate of potash is found 
 in a fused state at the bottom of the crucible ; it must be pul- 
 verized, separated from excess of charcoal, and kept in a dry state 
 for use. 
 
 Carbonate of soda may be obtained in much the same way, by 
 substituting nitrate of soda for nitrate of potash ; or by repeatedly 
 crystallizing the carbonate of commerce. 
 
 Nitrate of Potash. The presence of silica or silicates much 
 assists its decomposition. It is used as an oxidizing agent, the 
 potash resulting from its decomposition acting as flux. To pre- 
 vent violent action and ejection of particles of matter, its addition 
 to the crucible must be careful and gradual. Nitre is also em- 
 ployed in some instances as a substitute for nitrate of ammonia 
 for effecting the rapid and perfect combustion of organic sub- 
 stances. 
 
 Common Salt (Chloride of Sodium) was much recommended 
 by the older assayers, either mixed with flux, or a certain quan- 
 tity placed above it, for the purpose of preserving the substances 
 beneath from the action of the atmosphere, or to temper the ac- 
 tion of such bodies as cause much intumescence. It is very useful 
 in lead assays. When it is used, it must be previously pounded 
 and heated to dull redness in a crucible to prevent its decrepi- 
 tation. 
 
 Black Flux and its Equivalents. Black flux is both a reduc- 
 ing and a fusing agent. It is a mixture of carbonate of potash 
 and charcoal in a minute state of division. It is much employed, 
 and very serviceable. It is prepared by mixing 2 parts of argol 
 
POTASSA SALTS. 295 
 
 with 1 part of nitre, placing the mixture in an iron vessel and 
 setting it on fire by a burning coal or red-hot rod. When the 
 combustion is finished, the substance is pulverized and sifted 
 whilst jet hot, and kept in well-stoppered jars, as it rapidly ab- 
 sorbs moisture from the atmosphere. 
 
 Black flux is much used in lead and copper assays ; but as it 
 swells greatly at the commencement of the operation, the cruci- 
 ble must not be more than two-thirds full. , 
 
 It can be readily imagined that, as it fuses and reduces at the 
 same time, the relative proportions of alkali, carbonate, and 
 charcoal ought to vary according to the nature of the substance 
 acted upon ; and it is often expedient to employ the greatest pos- 
 sible proportion of alkali to obtain the largest yield of metal. 
 Black flux may be obtained richer in carbon by mixing 1 part of 
 nitre with 2J or three parts of argol. 
 
 Common black flux contains 5 per cent, of charcoal. The 
 flux prepared with 2J of tartar or argol to 1 of nitre, contains 
 8 per cent., and that with 3 contains 12 per cent, of charcoal. 
 
 Black flux can be replaced by anhydrous or dry carbonate of 
 soda mixed with some reducing agent. When charcoal is em- 
 ployed it must be reduced to a^very fine powder ; in fact, it ought 
 to be levigated. 
 
 The three following fluxes are very useful : 
 
 .Carbonate of Soda, . . < .94 88 816 
 Charcoal, 6 12 184 
 
 The second is very nearly equivalent to sodium and carbonic 
 acid, and the third to sodium and carbonic oxide ; but it must be 
 observed, that whatever precautions be taken, these mixtures 
 never become so liquid as black flux, because the charcoal tends 
 very much to separate and rise to the surface. 
 
 Instead of charcoal, it is preferable to use sugar or starch to 
 make a flux equivalent to black flux with carbonate of soda ; the 
 mixture must be made most intimately. 
 
 Cream of tartar, carbonized by a semi-combustion until it is 
 reduced to half its weight, is a very good substitute for black 
 flux : it contains about 10 per cent, of charcoal. 
 
 Argol (Cream of Tartar, Bitartrate of Pot ass a). When bi- 
 tartrate of potassa is heated in a covered crucible, a rapid de- 
 composition takes place, accompanied by a disengagement of in- 
 
296 WHITE OR MOTTLED SOAP. 
 
 flammable gases ; the substance agglomerates, but without fusing 
 or boiling up. The residue is black, blebby, and friable, and 
 contains 15 per cent, of carbon when produced from rough tartar 
 or argol, and 7 per cent, from cream of tartar. 
 
 These reagents produce the same effects as black flux, and 
 possess more reducing power, because they contain more com- 
 bustible matter; but this is an inconvenience, because the excess 
 prevents their entering into full fusion when the substance to be 
 assayed requires but a small proportion of a reducing agent. 
 They can be used with success in assays requiring much carbona- 
 ceous matter. 
 
 JSisulphate of Potassa is a convenient flux for several mine- 
 rals, such as for those highly aluminous (Rose), for chromic and 
 other similar ores (Booth}. 
 
 Salt of Sorrel (Binoxalate of Potassa), when heated, is decom- 
 posed. It decrepitates feebly, and during its decomposition is 
 covered with a blue flame ; it at first softens, and when fully 
 fused, is wholly converted into carbonate. When the oxalate is 
 very pure, the resulting carbonate is perfectly white and free 
 from charcoal ; but very often it is spotted with blackish marks. 
 It has no very great reducing power. 
 
 Cyanide of Potassium acts powerfully both as a reducing and 
 desulphurizing reagent, and is a very useful flux in small assays. 
 According to Liebig it has the advantage over the potassa salts 
 with vegetable acids, of not carbonizing the metal, for the salt 
 changes at the expense of the metallic oxide into cyanate of 
 potassa. If the metallic oxide predominates, the rest will be re- 
 duced by the cyanic acid without separation of carbon. 
 
 White, or Mottled Soap is a compound of soda with a fat acid. 
 When heated in close vessels it fuses, boiling up considerably, 
 and during its decomposition gives off smoke and combustible 
 gases, and leaves a residue composed of carbonate of soda with 
 about 5 per cent, of charcoal. Of all reducing agents soap ab- 
 sorbs the greatest quantity of oxygen, and as the residue of its 
 decomposition by heat affords but little charcoal, it has the pro- 
 perty of forming very fluid slags. Nevertheless, it is rarely em- 
 ployed, because certain inconveniences outweigh its advantages. 
 These inconveniences are, its bubbling up and its extreme light- 
 ness. It also requires to be rasped, in order to mix it perfectly 
 
LITHARGE GLASS. 297 
 
 with the substances it is to decompose, and it then occupies a 
 very large volume, and requires correspondingly large crucibles. 
 There are nevertheless cases where it may be used with advantage 
 by mixing it with other fluxes. 
 
 All those fluxes containing alkaline and carbonaceous sub- 
 stances are reducing and desulphurizing, besides acting as fluxes, 
 properly so called ; they also produce another effect which it is 
 useful to know, viz. : they have the property of introducing a 
 certain quantity of potassium or sodium into the reduced metal. 
 This was first pointed out by M. Vauquelin.* He found that 
 when oxide of antimony, bismuth, or lead was fused with an 
 excess of tartar, the resulting metals possessed some peculiar 
 characters, which they owed to the presence of several per cent, 
 of potassium. 
 
 METALLIC FLUXES. Litharge and Ceruse. These bodies 
 always act as fluxes, but at the same time often produce an alloy 
 with the metal contained in the ore to be assayed. Ceruse pro- 
 duces the same fluxing effect as litharge. The litharge is the 
 better flux, and is very useful in a great number of assays. 
 
 It fuses readily with the oxides of iron, copper, bismuth, an- 
 timony, and arsenic, sulphate of lead and the silicates, in the 
 proportion of 2 to 5 parts of litharge to 1 part of the substance 
 to be fluxed ; other oxides require a larger amount of litharge. 
 Its action is that of promoting fusion, reducing an oxide, and de- 
 sulphurizing a sulphuret. 
 
 Glass of Lead (Silicate of Lead}. The silicates of lead are 
 preferable to litharge in the treatment of substances containing 
 no silica, or which contain earths or oxides not capable of forming 
 a compound with the oxide of lead, excepting by the aid of silica. 
 It may be made by fusing 1 part of sand with 4 parts of litharge ; 
 if required more fusible, a larger proportion of litharge must be 
 added. 
 
 Borates of Lead. The borates of lead are better fluxes than 
 the silicates when the substance to be assayed contains free 
 earths ; but in order to prevent them swelling up much when 
 fused, they must contain an excess of oxide of lead. The borate 
 of lead containing *9056 of oxide of lead, and *0944 of boracic 
 
 * Annales des Mines. 
 
298 CALCINATION. 
 
 acid, is very good. Instead of borate of lead, a mixture of fused 
 borax and litharge may be employed ; it is equally serviceable. 
 
 Sulphate of Lead is decomposed by all silicious matters and 
 by lime, so that when these substances are present litharge is 
 produced, which fluxes them. 
 
 Oxide of Copper is rarely used as a flux for oxidated matters, 
 but is sometimes employed in the assays of gold and zinc to form 
 an alloy with those metals. In this case a reducing flux must be 
 mixed with the oxide. Metallic copper may be used, but is not 
 so useful, as it cannot be so intimately mixed with the assay. 
 
 Oxides of Iron are good fluxes for the silicates. They are, 
 however, rarely employed for that purpose ; they are more often 
 used to introduce metallic iron into an alloy to collect an infusible 
 or nearly infusible metal, by alloying it with iron, such as man- 
 ganese, tungsten, or molybdenum. 
 
 CALCINATION. The separation (in a dry way) of volatile from 
 fixed matter, by heat, is termed calcination. The process is ap- 
 plicable 
 
 To the expulsion of water from salts, minerals, coals, and other 
 substances. 
 
 " " carbonic acid from certain carbonates. 
 
 " " arsenic and sulphur from cobalt, nickel, and 
 
 other sulphuretted compounds. 
 
 " " bituminous matter from coals, and certain 
 
 minerals and ores. 
 To the ignition of quartz and silicious minerals to promote their 
 
 disintegration. 
 For the purpose of expelling the combined water of argillaceous 
 
 minerals, and of thus rendering them more obstinate to the 
 
 solvent action of acids and reagents. 
 
 If the substance under process is organic, its calcination in a 
 close vessel by a medium heat usually effects only partial decom- 
 position, the gaseous matter generated escaping through inter- 
 stices, and the fixed components remaining with a portion of un- 
 altered carbon. Performed in this manner, the process takes the 
 name of coking, familiar instances of which are the formation of 
 coke by distilling coal in closed retorts, the manufacture of char- 
 coal from wood, and of bone black from bones. 
 
 By increasing the temperature and admitting the air, the whole 
 
BOASTING. 299 
 
 of the alterable and volatile matter is expelled, the fixed matter 
 remaining as ashes. The process is then styled incineration, 
 and in this way the coke, charcoal, and ivory black, obtained as 
 above directed, may be entirely reduced to their incombustible 
 portions or ashes. 
 
 Calcination is effected in platinum spoons or crucibles, in deli- 
 cate experiments, over a spirit-lamp ; but in large operations a 
 furnace is required, and the containing vessels are crucibles, of 
 either metal or earthenware, according to the nature of the sub- 
 stance to be heated, though the latter are often unsuitable for 
 temperatures above a red heat. 
 
 When the operation is finished, the crucible should be taken 
 from the fire and allowed to cool gradually. The cover is then 
 to be lifted off, and the contents taken out with a spatula, and 
 the portions adhering to the sides removed with a feather. 
 
 If the substance undergoing calcination is fusible, it is neces- 
 sary, when quantities are to be ascertained, to weigh both the 
 crucible and contents before ignition, so that the amount of vola- 
 tile matter driven off may be expressed by thevweight lost in 
 heating. Water alone, or acidulated, with the aid of heat, gene- 
 rally removes the calcined matter from the crucible. 
 
 A body decrepitating by heat should be powdered before being 
 subjected to the process of calcination, and the temperature 
 should be raised slowly and gradually, otherwise when the cru- 
 cible is not covered, a loss [may result from the ejection of 
 particles. 
 
 To avoid contact with the generated vapors or with the atmo- 
 sphere, which to some substances act as reducing agents, the 
 crucible should in such cases be covered, and, if tightly luted, per- 
 forated with one or more small holes for the escape of vapor. 
 
 ROASTING. This process, as generally understood, is a kind of 
 calcination to which many ores are submitted before their final 
 reduction to the metallic state, for the purpose of expelling ingre- 
 dients which would either delay that process or be injurious to 
 the metal when extracted. In this way, water, carbonic acid, 
 sulphur, selenium, arsenic, and sometimes other substances, are 
 driven off from the ores containing them. The term is also ap- 
 plied to other processes, among the most important of which is 
 that of the exposure to heat and air, by which metals become 
 
300 DEFLAGRATION. 
 
 altered in composition. Thus, copper becomes oxidized, and 
 antimony and arsenic acidified by union with oxygen. 
 
 Roasting is always effected in broad, shallow open vessels, so 
 that the air may have free access ; and in order to promote the 
 absorption of oxygen or the escape of the volatile substance, the 
 surface of the body to be heated should be increased by previous 
 pulverization, and it should be constantly stirred during the ope- 
 ration, so as to present as many points of contact as possible. 
 The most suitable vessel is a baked earthenware saucer or cap- 
 sule placed in a muffle or upon the bars of a calcining furnace. 
 Sometimes a crucible is used, and then the position of the vessel 
 in the furnace should be slightly inclined on one side. In either 
 case the vessels should be heated to dull redness previous to 
 receiving their charge. 
 
 That species of roasting termed deflagration is effected by 
 rapidly heating the substance to be oxidized, together with some 
 additional body as an oxidizing agent, as a nitrate or chlorate, 
 for instance. The powdered mixture is added portionwise to the 
 crucible previously heated, and maintained at redness during the 
 operation. The vivid and sudden combustion which ensues modi- 
 fies the composition of the original substance, and increases its 
 amount of oxygen at the expense of the addendum. Thus, for 
 instance, sulphuret of arsenic is deflagrated with nitre, to produce 
 arseniate of potassa, titanium; and certain other metals to be 
 transformed into oxides. 
 
 Deflagration is also used as a means of detecting the presence 
 of nitric or chloric acids. For this purpose the suspected sub- 
 stance is to be heated with cyanide of potassium, in a small pla- 
 tinum spoon. If deflagration ensues, it is a test of the presence 
 of one of them, or a compound of one of them. 
 
 The crucibles may be of clay or metal, according to the nature 
 of the substance to be heated. The roasting of substances for 
 the expulsion of organic matter may be effected in platinum ves- 
 sels, provided the heat is not carried sufficiently high to produce 
 fusion of the substance being roasted. 
 
 The heat must, at first, be very gradually applied, and at no 
 time be made great enough to fuse or agglutinate the material, 
 otherwise the process will have to be suspended in order to re- 
 pulverize the matter. Proper care at the commencement will 
 
REDUCTION. 301 
 
 obviate the necessity of this additional trouble. When the heat 
 has been cautiously raised to redness and all liability of fusion is 
 over, the fire may be urged to the production of a yellowish red 
 or even white heat, so that the expulsion of volatile matter may 
 be complete. 
 
 Roasting operations which disengage deleterious or disagree- 
 able fumes should be carried on in the open air or under a hood, 
 and when the volatile matters are valuable, they may be condensed 
 as directed in DISTILLATION and SUBLIMATION. 
 
 Decrepitation, which frequently occurs and occasions loss by 
 ejection of particles of the mixture, is owing to the sudden va- 
 porization of the water of crystallization, or water mechanically 
 confined, which in finding vent scatters the confining substance 
 with a crackling noise. To prevent this loss, the crucible should 
 be loosely covered until decrepitation ceases. 
 
 REDUCTION. This operation illustrates the use of tubes in ex- 
 periments requiring the application of high heat. It is employed 
 for the separation of metallic bases from any bodies with which 
 they are combined ; but is generally confined to the extraction 
 from an oxide that being the kind of combination most com- 
 monly met with. The combined action of heat and certain re- 
 agents is required to effect this result, the temperature varying 
 with the nature of the substance to be reduced. , - 
 
 The most usual reducing agents are charcoal and hydrogen 
 gas. Tallow, oil, and resin are sometimes used, but being easily 
 decomposed they are dissipated before entire reduction has oc- 
 curred. Sugar and starch are also occasionally employed. 
 We shall, however, confine our remarks to the two principal 
 articles. 
 
 Reduction ly Charcoal. Charcoal is used for this purpose in 
 two ways, either in powder and directly mixed with the substance, 
 or as a lining coat to the crucible in which the reduction is ac- 
 complished. The first mode is objectionable, because the excess 
 of coal which is required to be used interferes with the agglomera- 
 tion of the particles of reduced metal. Whenever it is adopted, 
 the quantity of coal-dust to be added, which must be sufficient to 
 transform all the oxygen of the oxide into carbonic acid, can be 
 determined by calculation. This amount is then mixed thoroughly 
 with the Oxide previously powdered, and is transferred to a cru- 
 
302 REDUCTION. 
 
 cible, taking care to place the charge in the centre, and to cover 
 the contents with a layer of the dust. The whole is then to be 
 subjected to the heat of a furnace, assisted if necessary, by a blast, 
 The reduction in this way, the most convenient for large quan- 
 tities, is rapid and complete, but the metallic residue is often 
 mixed with coal-dust. 
 
 In general, the mere contact of carbon is sufficient to effect re- 
 duction, and consequently the inconvenience of the above plan 
 may be avoided by the use of a brasque or crucible lined inte- 
 riorly with charcoal. An earthen crucible is very readily 
 brasqued as follows : A mixture of three parts of charcoal-dust, 
 and two parts of powdered clay, is mixed with water and kneaded 
 into a plastic dough. The bottom of the crucible is then covered 
 with this dough, and a wooden cylindrical core of diameter equal 
 to that required for the cavity, is inserted in the centre and sur- 
 rounded with more of the same dough, which is compressed with 
 the fingers at each addition so as to make the whole as compact 
 as possible. The core is then to be carefully withdrawn, and the 
 crucible placed aside to dry. A platinum crucible, which is as 
 applicable as clay for certain operations, can be brasqued in the 
 same way. Some operators use the coal-dust without clay, and 
 moisten it with water or oil. The crucibles should be free from 
 external fissures to prevent access of air, and must always be 
 covered when heated. The reduction by this plan is slower than 
 by the first mode, and requires a higher temperature, but the 
 metal as procured is cleaner. 
 
 The powdered oxide is placed in the cavity in sufficient quan- 
 tity to fill it, then compressed with the fingers and covered with 
 a layer of coal-dust. The cover being luted upon the crucible 
 the whole is to be heated in a blast furnace. The reduction pro-, 
 ceeds from the surface, that part of the oxide next to the char- 
 coal being first acted upon. The time required depends upon 
 the nature of the oxide, the degree of temperature, and the 
 quantity under process ; sometimes, particularly when the metals 
 are very fusible, the reduced particles collect in a clean lump at 
 the bottom of the crucible, and are easily removable when cold, 
 with the finger or spatula. Others again, more refractory, form 
 a very friable lump of metallic powder. 
 
 Reduction ly Hydrogen. This mode, which is much used in 
 
REDUCTION APPARATUS. 
 
 303 
 
 analyses, consists in passing a current of hydrogen gas over the 
 metallic oxides heated to redness in a glass, or better, porcelain 
 tube, and is equally applicable to some chlorides and other com- 
 pounds. The arrangement of the requisite apparatus is shown 
 in Fig. 218. A is a flask for the disengagement of hydrogen 
 
 Fig. 218. 
 
 gas, by the action of dilute sulphuric acid upon zinc, the fun- 
 nelled tube a being for the ingress of the acid. The disengage- 
 ment tube b is bent at right angles and bulbed midway in its 
 horizontal arm. The bulb is to be furnished with a plug of raw 
 cotton for the condensation and retention of any aqueous vapor 
 that may pass over. This tube is joined hermetically to another 
 short tube c by means of an india-rubber connection.* The 
 
 * The use of india-rubber as a material for forming flexible joints is one of the 
 most important aids in chemical manipulation. Its property of readily uniting at 
 freshly cut surfaces, its flexibility, its ready and close adhesion to surfaces, and 
 power of resisting the action of corrosive vapors, except those of chlorine, sulphuric 
 and nitric acids, and a few others, render it peculiarly excellent for many mechani- 
 cal purposes of the laboratory. Tubes of any shape and size, according to the 
 form and dimensions of the parts of apparatus to be connected, are to be fashioned 
 out of it with almost equal facility. For the transmission of corrosive vapors or 
 gases they should have an outer layer, the seam in which must be directly oppo- 
 site to that in the tube which it invests, so as to insure perfect tightness. Prof. 
 Booth uses the india-rubber pipe, made by Goodyear, as conduits for steam in boil- 
 ing corrosive liquids by that agent, and gives it consistence with flexible lead pipe, 
 which he covers externally and internally. A better framework would be a spiral 
 
30i GAS-BAGS. 
 
 connecting tube is made of sheet caoutchouc, about one-twelfth of 
 
 an inch in thickness. A piece of 
 Flg - 219> the required length of the tube and 
 
 twice the intended width is cut out 
 and wrapped around a cylindrical 
 glass rod d, Fig. 219, of diameter 
 very nearly as great as that for the 
 tube to be formed. The ends are 
 then brought closely together by 
 compression between the thumb and 
 
 fingers as at &, and the excess removed, close to the surface of 
 the rod, with a pair of clean sharp scissors. The freshly cut 
 edges being further pinched together throughout the length of 
 the tube, form a close, air-tight, scarcely perceptible joint. The 
 rod is then to be withdrawn, and the tube thus formed carefully 
 drawn over the end of one of the glass tubes to be connected, so 
 as to form an extension for the reception of the end of the other. 
 The two ends should approach each other almost to contact, a 
 minute interval being necessary to afford the requisite flexibility. 
 This junction-pipe is fastened to the surface of the tube by fine 
 twine wrapped or tied around each of its ends, as shown at rr ? 
 Fig. 218. 
 
 The gas-bottle thus fitted is connected, by means of a per- 
 
 coil of wire. The tubing made of canvas imbued with caoutchouc is less durable, 
 and does not admit of such general application. 
 
 Before forming the tube above mentioned, it is better to warm the caoutchouc, 
 by which its flexibility is increased and its cut surface made to adhere more 
 readily and closely. The scissors cut more freely when previously moistened. 
 These flexible joints not only relieve the apparatus of stiffness and consequent 
 liability to fracture, but enable the operator to adjust it more rapidly and satisfac- 
 torily than he could possibly do without them. A little practice upon shreds will 
 give great proficiency in the art of forming india-rubber tubes arid joints. 
 
 India-rubber for this purpose is now made by Goodyear, New York, who sells 
 it in sheets of various sizes. Ready-made tubing of various bores is also furnished 
 by the same manufacturer. Gas bags are likewise made of caoutchouc. The 
 larger sizes, pp. 170, 172, are to be procured from the manufacturer. Smaller 
 ones, for nice purposes, may be readily made from the rubber bottles of the shops. 
 One of uniform thickness, and as free as possible from indentations and imper- 
 fections, is softened in boiling water or by exposure for several days to contact 
 with ether, and then adjusted upon a stop-cock with a syringe attached. The air 
 must next be injected slowly, so that the expansion of the bag may be gradual and 
 uniform throughout all its parts ; or the bag may very conveniently be blown out 
 with the mouth. 
 
REDUCTION BY HYDROGEN. 
 
 305 
 
 forated cork with the drying-tube d, filled with lumps of dried 
 chloride of calcium. At the opposite end of the drying-tube e, 
 is another tube with a bulb blown in its centre, for the reception 
 of the substance to be reduced, and in which it is heated by the 
 flame of a spirit-lamp. This tube, like the other, is annexed by 
 elastic joints to the short tube connected with the desiccating- 
 tube through a perforated cork. 
 
 This plan, first proposed by Berzelius, was used by him in the 
 synthesis of water, binoxide of copper being the substance em- 
 ployed to abstract the hydrogen, its oxygen forming water there- 
 with. 
 
 A modification of the foregoing apparatus is shown by Fig. 220, 
 
 which exhibits a closed crucible of platinum, as the receiver, in 
 place of a glass bulb, it being necessary, in certain instances, to 
 exclude the direct contact of air during and immediately after 
 the heating. 
 
 Hydrogen is a powerful reducing agent, and leaves the metal 
 absolutely pure. At a red or white heat, its action will reduce 
 the oxides of lead, bismuth, copper, antimony, zinc, iron, cobalt, 
 nickel, tungsten, molybdenum, and uranium. 
 
 The heat should not be applied to the bulb until it is entirely 
 freed from air, which may be done by allowing the hydrogen to 
 pass over some minutes previously. A disregard of this precau- 
 tion may cause an explosion from the combustion of a mixture of 
 hydrogen and atmospheric air. 
 
 The above apparatus answers very well for decomposing me- 
 tallic sulphurets by chlorine. It is also applicable for heating 
 solids in gases, and serves for the preparation of chloride of sul- 
 
 20 
 
306 REDUCTION BY CARBONIC OXIDE. 
 
 phur, of phosphorus, and of many other volatile chlorides. For 
 this purpose it is only necessary to replace the flask A by other 
 suitable generating vessels, and the extreme end of the exit tube 
 by a tubulated retort with its beak bent downwards and leading 
 into the recipient, kept cool by a frigorific mixture. 
 
 The tubes for these purposes must be of hard glass and entirely 
 free from lead, and not exceeding a third of an inch in width. 
 The bulbs should be of 1 J inch diameter. The chlorcalcium tube 
 may be three-fourths of an inch wide. >,, 
 
 There are other modes of reduction, of less general application, 
 however, than the preceding. Metals may be precipitated in a 
 free state, in some instances, from solutions, by presenting bodies 
 for which their oxygen has a stronger affinity ; thus, for example, 
 protosulphate of iron precipitates metallic gold; phosphorous 
 acid, mercury ; and formic acid or formate of soda, both of these 
 metals, and also silver and platinum, if the liquids containing 
 them in solution are boiled. So also one metal may reduce 
 another if the affinity of the first for oxygen is greater than that 
 of the last. Thus metallic copper throws down mercury, silver, 
 and arsenic, from their solutions, and iron precipitates copper. 
 
 Metals are also reduced by galvanic action, practical illustra- 
 tions of which are seen in the galvanoplastic art. All oxides 
 which resist the combined action of heat and charcoal or hydrogen, 
 are reduced by the agency of galvanism. 
 
 Reduction by Carbonic Oxide. Another convenient agent of 
 reduction, employed in the same manner as hydrogen, is carbonic 
 oxide, made on a small scale by the action of oil of vitriol on 
 oxalic acid, and separation of the carbonic acid produced at the 
 same time, by milk of lime. It readily reduces the metallic 
 oxides of nickel, iron, zinc, that of lead at a very low tempera- 
 ture, and that of copper below a red heat. For heating in manu- 
 facturing processes, it is made by regulating the admission of air 
 to a deep bed of ignited anthracite or other coals, and driving a 
 blast of air horizontally through the gas as it issues from the ,fire, 
 all other access of air being prevented. It has in this manner 
 been applied to reheating and puddling furnaces. Carbonic 
 oxide is doubtless the great reducing agent in large metallurgic 
 operations. 
 
 Roasting and Reduction in Tubes. In very delicate experi- 
 
ROASTING AND REDUCTION IX TUBES. 
 
 307 
 
 ments, and particularly when the volatile matter expelled by the 
 heat is to be collected for examination, roasting and reduction 
 are effected in small glass tubes closed at one end. The glass 
 must be white, difficultly fusible, and free from lead. The sub- 
 stance is placed in the lower or closed end of the tube, which is 
 then inclined and heated over the spirit-lamp, as shown in Fig. 
 229. In this way sulphur and arsenic may be sublimed from 
 certain of their compounds, and mercury from less volatile metals. 
 By leaving the tube open at both ends so as to allow free access 
 of air, many volatile bodies are oxidized, and collect, on congela- 
 tion, in the upper part of the vessel. Those tubes, with a bulb 
 blown at their lower end, as shown at 1, 5, in Fig. 221, are most 
 applicable for decrepitating substances. 
 
 Fig. 221. 
 
 J 4 
 
 ^} 5 
 
 The above drawing exhibits the several forms of tubes used for 
 the reduction of metals, and particularly the separation of ar- 
 senic and mercury from more fixed matter. Any of these forms, 
 or even a small test-tube 4, will answer. Berzelius prefers the 
 shape of 1 ; Rose that of 2 ; Liebig that of 3 ; and Clarke that 
 of 5. 
 
 The letters a b c in 2, and b in 3, indicate the position of the 
 substance to be roasted together with its reducing agent, and d 
 and a in 2 and 3, the rings of condensed volatile matter sub- 
 limed by the heat. Berzelius and Rose's, and Liebig's tubes are 
 three inches in length ; Clarke's two inches. Their diameters vary 
 
308 
 
 PORCELAIN AND METALLIC TUBES. 
 
 from one-sixteenth to one-fourth of an inch, according to the 
 amount of substance to be heated. 
 
 Combustion in Grlass Tubes. The tube which contains the 
 substance to be heated, should be made of hard and refractory 
 glass entirely free from lead. Its position in the furnace is 
 shown by Fig. 139, which has already been fully explained. 
 When it is designed to apply a very intense heat to the tube, the 
 latter should be enveloped in a jacket, to prevent its bursting or 
 blowing out in places. This jacket is a strong iron plate mould, 
 with a lining of plaster of Paris. It is shown in two half por- 
 tions, as well as closed, by the annexed figure. 
 
 Fig. 222. 
 
 
 The two semi-cylinders are bound into one by iron wedge fas- 
 tenings ; and throughout the circumference it is perforated with 
 holes. Plaster of Paris having been made into stiff paste, with 
 a little water and cow's hair, each half of the mould is then filled 
 with it ; the combustion-tube next imbedded in one of them, and 
 when the plaster begins to set, the other is placed on top, and 
 the two fastened together. When the plaster has hardened, it is 
 ready to be heated ; but the heat must be gradual at the early 
 part of the operation. 
 
 Porcelain and Metallic Tubes. For the reduction of some 
 oxides by contact with gases at furnace temperature, for the 
 decomposition of certain organic matters, such as oils, &c., and 
 for effecting many combinations of gases with solids, the glass 
 tubes are replaced by those of porcelain, iron, or platinum. 
 
 Porcelain tubing should be selected with care. It should be 
 
PORCELAIN AND METALLIC TUBES. 309 
 
 straight, perfectly cylindrical, free from defects, glazed inter- 
 nally, and as thin as possible. These tubes are adjusted in man- 
 ner as directed for those of glass, and heated over the furnace, 
 Fig. 126 ; but as they are not refractory, care must be taken in 
 heating them. It is advisable to give them an exterior coating 
 of fire lute, and then dry them. The fire should be ignited, and 
 all moisture expelled from the charcoal before they are placed in 
 the furnace, otherwise their fracture may result. It is indispen- 
 sable, too, that the heat shall be carefully managed, and after 
 the completion of the process, the tube must not be removed 
 from the furnace until it has entirely but gradually cooled. 
 
 Iron tubes are used for the decomposition of water, potassa, 
 and for other operations to which those of glass and porcelain are 
 not adapted, by reason of inability to withstand high heat. Gas 
 tubing is the most economical, and can be had of all lengths and 
 diameters. These also should be covered exteriorly with luting 
 so as to prevent the oxidation of the iron by the fire. 
 
 Metallic tubes of small size may be heated over the furnaces, 
 Fig. 139, but those of larger dimensions require the use of the 
 furnace, Fig. 126. The circular openings x, x, in each side, are 
 especially for the passage of a tube. The grate should be ele- 
 vated, so that the fire may entirely surround it. 
 
 Metallic tubes are adjusted to generating and other apparatus 
 by means of metallic couplings, gallows screws, or, in some cases, 
 by fire lute. This latter does not make a secure or tight joint, 
 and is only used in the absence of more convenient means. The 
 ends of the tube should project far enough beyond the sides of 
 the furnace to allow their refrigeration when necessary. The 
 gas may be introduced directly from the generating vessel, or 
 from a caoutchouc bag or gasometer, merely by adjusting the 
 end of the tube with the mouth or outlet by a suitable coupling. 
 The resultant product may, in like manner, be collected by simi- 
 lar adaptations to the other end. 
 
 Fragments of flint or coils of iron or of platinum wire, placed 
 within the tube, increase the points of contact of the contained 
 matter and greatly promote its heating. 
 
 As short tubes are occasionally used for effecting the combina- 
 tion of substances alterable by exposure in a hot state, they 
 
310 CUPELLATION. 
 
 should, for such purposes, be fitted at the ends with screw plugs, 
 to prevent access of air. 
 
 Platinum tubes are only used on rare occasions for particular 
 .purposes, to which those of glass, porcelain, or iron, are inap- 
 plicable, ^v^- 
 
 ^'V J& '''/'. ' ' M "? 
 
 CHAPTER XVI. 
 
 CUPELLATION. 
 
 GOLD and silver are assayed by the agency of heat and litharge 
 in shallow, slightly conical crucibles, Fig. 223, called cupels. 
 
 Fig. 223. 
 _M Bf 
 
 a. SL H. 
 
 This process separates these metals from any debasing admixture; 
 for, when the alloy is heated together with litharge, all but the 
 precious metals are oxidized ; and the oxides thus formed, to- 
 gether with the semi-vitreous litharge, are absorbed by the cupel, 
 whilst the nobler metal remains as a button of absolute purity. 
 
 Cupels. These small crucibles are generally made of bone- 
 ash, because that material fulfils better than any other the neces- 
 sary requirements. It is resistant to the action of the fused 
 oxides of lead and bismuth, and by its porosity facilitates the 
 penetration of the oxides, and at the same time is, when made 
 into shape, strong enough to bear handling without fracture. 
 The cupels used at the United States Mint are made in a matrix 
 of If inches diameter. The semicircular cavity is two-fifths of an 
 inch deep in the centre. This size, however, can be varied and 
 they may be made smaller or larger according to the quantity of 
 matter to be operated upon. Their mode of manufacture is as 
 follows : Take bones or bone-black and calcine them in an open 
 crucible until the expulsion of all animal and carbonaceous 
 matter, which is known by the residue assuming a whitish ap- 
 pearance. Empty the cooled contents of the crucible into clean 
 water, and give it repeated washings in fresh waters to remove 
 all soluble matter; filter and dry. The dried matter is pure 
 
CUPELS. 311 
 
 phosphate of lime with a minute portion of partially decomposed 
 carbonate. 
 
 Make the powder, calcined and purified as directed above, into 
 a paste with water or preferably with beer (Mitchell), in the pro- 
 portion of 4 Ibs. of bone ash to half a pound of beer. The above 
 mixture is just sufficiently moist to adhere strongly when well 
 pressed, but not so moist as to adhere to the finger or the mould 
 employed to fashion the cupels. The mould, Fig. 224, of polished 
 iron consists of two pieces, one a ring having a conical opening ; 
 the other, a pestle having a hemispherical end fitting 
 the larger opening of the ring. In order to mould 
 the cupels, proceed as follows : Fill the ring with 
 the composition, then place the pestle upon it, and 
 press down as much as possible. By this means, 
 the moistened bone-ash will become hardened, and 
 take the form of the pestle ; and the latter must then 
 be struck on the head with a heavy mallet, to insure 
 greater consolidation of the cupel. It is then to be turned lightly 
 round, so as to smooth the inner surface of the cupel, and with- 
 drawn ; after which the cupel must be removed from the mould 
 by a gentle pressure on the narrowest end. When in this state, 
 the cupel must be dried gently by a stove \ and lastly, heated in 
 a muffle, to expel all moisture. It is then ready for use. 
 
 There are two or three points to be observed in manufacturing 
 the best cupels. Firstly, the powdered bone-ash must be of a 
 certain degree of fineness ; secondly, the paste must be neither 
 too soft nor too dry ; and thirdly, the pressure must be made 
 with a certain degree of force. A coarse powder, only slightly 
 moistened and compressed, furnishes cupels which are very 
 porous, and break on the least pressure, and which allow small 
 globules of metal to enter into their pores, the most serious in- 
 convenience of all. 
 
 When, on the contrary, the powder is very fine, the paste very 
 moist and compressed very strongly, the cupels have much soli- 
 dity, and are not very porous, the fine metal cannot penetrate 
 them, and the operation proceeds very slowly ; besides, the assay 
 is likely to become dulled and incapable of proceeding without 
 a much higher degree of temperature being employed. (Ber- 
 thier.} 
 
312 MUFFLES. 
 
 The Process of Oupellation. In order to protect the cupel 
 from contact with the fire, and at the same time allow a free 
 access of the air, it is when heing heated placed in a muffle. The 
 muffle is a refractory vessel of baked fire clay, Fig. 225, arched 
 above, flat-bottomed, and pierced near its 
 base with small lateral openings for the 
 passage of the heat. Excepting these 
 
 I x-^ ^~-<.^-^ \^ apertures, and that at the front for the 
 introduction of the cupels and inspection of 
 the process, the muffle is entirely closed. Its dimensions depend 
 upon the size of the cupel and of the furnace in which it is to be 
 heated. 
 
 Its position in the furnace (D, Fig. 1ST), must be exactly level, 
 and to protect it from the corrosive effects of volatilized oxides, 
 it may be payed over with a thin paste of bone-ashes. The muffle 
 being properly arranged in the furnace, and held firmly in its 
 place by lute, the cupels are then introduced, and the fuel (char- 
 coal) ignited. The lead must be 
 Flg- 226> perfectly pure. It can be reduced, 
 
 for this purpose, from refined li- 
 tharge. " When the cupels have 
 Fig 227. been exposed for half an hour, and 
 
 have become white by heat, the 
 lead is put into them by means of 
 the tongs, Fig. 226, and as soon 
 
 as this becomes thoroughly red and circulating, as it is called, 
 the metal to be assayed, wrapped in a small piece of paper, is 
 added, and the fire kept up strongly until the metal enters the 
 lead and circulates well, when the heat may be slightly dimi- 
 nished, and so regulated that the assay shall appear convex and 
 ardent, while the cupel is less red, that the undulations shall 
 circulate in all directions, and that the middle of the metal shall 
 appear smooth, surrounded with a small circle of litharge, which 
 is being continually absorbed by the cupel. This treatment 
 must be continued until the metal becomes bright and shining, or 
 is said to i lighten ; after which, certain prismatic colors, or rain- 
 bow hues, suddenly flash across the globules, and undulate and 
 cross each other, and the latter metal soon appears very brilliant 
 and clear, and at length becomes fixed and solid. This is called 
 
CUPELLATION IN TAYLOR'S MUFFLE. 313 
 
 the ' brightening, and shows that the separation is ended. In 
 conducting this process, all the materials used must be accurately 
 weighed, especially the weight of the alloy before cupellation, 
 and the resulting button of pure metal. The difference gives the 
 quantity of alloy." 
 
 When the operation is completed, the cupel is to be withdrawn 
 from the fire, and allowed to cool, and the metallic button then 
 removed with the pincers. If the assay is a good one, it will 
 detach easily. The button should be round and brilliant upon 
 its upper surface, but rough and striated at the bottom. If its 
 surface is dull and flat, too much heat has been employed ; on the 
 contrary, when it is spongy, adheres tenaciously to the cupel, 
 and contains scales of litharge, there has been a deficiency of 
 heat, and the fire must be again urged, and the flowing of the 
 metal promoted, by adding to the cupel a little powdered char- 
 coal. Complete fusion is indispensable to the success of the ope- 
 ration. If too much lead has been added, the cupel is allowed 
 to cool, the button carefully separated, so as to be free from adhe- 
 rent particles of ash, and transferred to a fresh cupel and the 
 process continued. In experienced hands, the pneumatic blast, 
 p. 169, may be made to replace the furnace in the process of 
 cupellation. 
 
 Cupellation* in Taylor s Muffle. Mr. T. Taylor (Memoirs of 
 Chem. Soc. vol. iii. p. 316), claims for his new form of muffle 
 the following advantages: "1st. Crucibles may be maintained 
 at a much higher temperature than can be readily obtained when 
 the ordinary muffle is used, while the degree of heat and the 
 quantity of air admitted may be regulated with the greatest 
 nicety. 2d. Owing to the greater draught of air, the oxidation 
 of the lead (in the process of cupellation) is more quickly effected ; 
 and lastly, by looking through an opening in the furnace cover, 
 the operation may be watched from first to last. 
 
 " Two black lead crucibles of the same size are ground flat, so 
 that when applied one to the other they may stand steady. An 
 oblong or semicircular notch is cut out of the mouth of one of the 
 crucibles, and a hole is also drilled through its bottom. This 
 crucible, when placed on the top of the other, constitutes the 
 muffle, and of course resembles in shape a skittle. To cupel 
 with this apparatus, the lower crucible is nearly filled with clean 
 
314 SUBLIMATION DISTILLATION. 
 
 sand, set upon the bars of the grate in the centre of the furnace, 
 and brought to a low red heat. The cupel containing the lead of 
 the alloy is then placed upon the sand and immediately covered 
 by the crucible, taking care that the notch in its side shall be 
 opposite to, and correspond with, the furnace door ; more fuel is 
 added, during which it is well to cover the hole in the top of the 
 muffle with a crucible lid, in order to prevent the admission of 
 dirt. When the muffle has become throughout of a bright red 
 heat, the furnace door is thrown open, and the ignited fuel gently 
 moved aside so as to permit a view of the side-opening in the 
 muffle. The current of air which is thus established through the 
 muffle instantly causes rapid oxidation of the lead, and this may 
 be regulated at pleasure by closing the door more or less. If 
 from the fuel falling down, any difficulty should be experienced 
 in maintaining a free passage for the air, a portion of a porce- 
 lain tube, or a gun-barrel, may be passed through the furnace 
 door to within an inch of the muffle ; but this proceeding is gene- 
 rally rendered quite unnecessary, by taking care to place some 
 large pieces of coke immediately round the door of the furnace." 
 
 CHAPTER XVII. 
 
 SUBLIMATION DISTILLATION. 
 
 WHEN simple or compound bodies which are either wholly or 
 in part capable of assuming the aeriform state are subjected to 
 heat, they or their most volatile constituents, upon reaching the 
 required temperature, rise in the form of vapor. If these vapors, 
 in their transit, are intercepted by a surface of a lower tempera- 
 ture, they condense and take a solid or liquid form, according to 
 their nature. If the product is a solid, it is termed sublimate, 
 and the process by which it is obtained is SUBLIMATION; if it is 
 liquid or gas, it takes the name of distillate, and the operation 
 which yields it that of DISTILLATION. 
 
 Both of these processes are indispensably useful in chemistry, 
 for they afford the facility of taking advantage of the unequal 
 volatility of bodies for their separation. 
 
SUBLIMATION. 315 
 
 As instances of sublimation, we have calomel and corrosive 
 sublimate made by heating equivalent proportions of sulphate of 
 mercury and common salt ; benzoic acid evolved from the gum ; 
 pure indigo from the commercial article, and camphor from the 
 crude material. Iodine is sublimed to free it from impurities ; 
 biniodide of mercury to convert it into crystals ; naphthalin to 
 free it from empyreumatic matter, and succinic acid to separate 
 water. 
 
 In like manner, multitudes of instances of the importance of 
 distillation, in the everyday-processes of the chemist and the manu- 
 facturer, might be adduced. It is employed in the separation and 
 rectification of alcohol, the preparation of the ethers, of many 
 mineral and vegetable acids, and of a very great number of other 
 chemical products. 
 
 SUBLIMATION. 
 
 The implements of sublimation are manifold, and vary in size 
 and construction with the quantity of the substance to be heated, 
 the nature, degree of volatility, and the affinity of the subliming 
 body for the oxygen of the atmosphere. 
 
 There are certain rules to be observed in order to a successful 
 execution of the process ; but whatever the apparatus, its arrange- 
 ment and management must be such that there shall be no 
 diminution of the temperature of the vaporized matter until it 
 reaches the recipient in which it is. to be refrigerated and con- 
 densed. 
 
 The covers of flat subliming vessels and the recipients or 
 condensing portions of those of other shapes, must invariably be. 
 out of and above the fire, and exposed to the cooling influence of 
 air. When the sublimed particles are very volatile, it will even 
 be necessary to promote their condensation by covering the 
 recipient with rags, which are to be kept constantly wet with 
 cold water or some other refrigerant. 
 
 The usual mode of heating subliming vessels is by the sand- 
 bath, but for some substances requiring a very high temperature 
 for their volatilization, direct fire is necessary. For small expe- 
 riments, the lamp will be most convenient; but in large opera- 
 tions, the furnace must be used. 
 
 In order to prevent explosion, the small opening in the top, 
 
316 SUBLIMATION IN TUBES. 
 
 at the centre of the refrigerant, must be only closed with a plug 
 of raw cotton, and should be freed from obstruction by occa- 
 sional poking with a wire. When the escape of vapor through 
 this hole is^ rapid, the heat is too high and must be diminished 
 immediately. 
 
 After the completion of the operation, the apparatus must be 
 left to cool before it is opened or the recipient removed. 
 
 The necessary breaking of close vessels for the removal of the 
 contents, renders their use expensive ; whenever, therefore, the 
 nature of the substance will permit, an alembic with detached 
 head should be preferred. Such vessels are more economical and 
 easy of management, but generally require that their joints be 
 made impermeable by luting. 
 
 Sublimation in Tubes. Sublimation is very available in 
 analyses for detecting the presence of minute quantities of vola- 
 tile metals, acids, and other substances, the implement for the 
 purpose being a small tube of such form as is shown in Figs. 221, 
 228. After the introduction of the substance, previously pow- 
 dered and dried, the tube is drawn out at its open end to a fine 
 orifice, and the lower part heated gradually over the flame of a 
 spirit lamp (Fig. 228). The volatilized portion will be condensed 
 
 upon the sides of the upper and 
 cooler parts. By dividing the 
 tube with a file, the sublimate 
 can be exposed for microscopic 
 examination or removed for fur- 
 ther assays under the blow-pipe. 
 The tubes for sublimation may 
 be from 4 to 8 inches in length, 
 and from an eighth to half an 
 inch in diameter, according to 
 
 the quantity of the matter to be sublimed, and the required deli- 
 cacy of the operation. 
 
 Berzelius uses a tube entirely open at the upper end for those 
 sublimations in which there are two volatile products, of which 
 one is to be drawn off entirely in the form of gas by the absorp- 
 tion of oxygen from the atmosphere, and recognized by its odor, 
 and the other condensed in the upper part of the tube ; as, for 
 example, a mixture of sulphur and selenium. 
 
SUBLIMATION IN FLASKS. 
 
 317 
 
 Fig. 229. 
 
 Faraday gives the form of a tube apparatus (Fig. 229) for 
 condensing heavy vapors or easily fusible 
 substances, as naphthaline, iodine, &c. 
 The bent tube b is of a diameter only large 
 enough to allow its free passage over the 
 subliming tube a. The upper part of the 
 middle portion of the tube may be kept 
 cool by paper or cloth wrappers moistened with water, in order 
 to promote the condensation of the sublimed matter. The heat 
 of the spirit-lamp is sufficient for these small operations, and the 
 apparatus, as adjusted, may be properly maintained by the 
 upright clamp, Fig. 186. 
 
 Sublimation in Flasks. Florence or sweet oil flasks are well 
 adapted to purposes of sublimation on account of their cheapness, 
 uniformity of thickness, and power of resisting high heats. 
 Having received their charge they are to be imbedded in a sand- 
 bath to a depth above the level of the contents, and heat is to be 
 applied gradually until the proper temperature is arrived at. 
 The position of the flask should be inclined, so that its neck may 
 lead directly into the recipient, as shown at Fig. 230. In this 
 manner, considerable quantities of matter may be operated upon 
 even at high temperatures, the glass bearing a red heat without 
 injury. Another mode of arranging a flask for this process is to 
 connect its neck, in the manner of a hood, with a long bent tube 
 
 Fig. 230. 
 
 Fig. 231. 
 
 leading into the refrigerant and recipient, as shown in Fig. 231. 
 The inconvenience of this arrangement is the condensation of the 
 gaseous matter in the tube, the obstruction from which may, 
 without great care, cause the explosion of the flask. 
 
 Flat bottomed flasks of thin German glass are sometimes used, 
 
318 
 
 SUBLIMATION IN RETORTS. 
 
 Fig. 232. 
 
 but they are more expensive than oil flasks. 
 Their position in the sand-bath is upright, 
 and the flange around their necks acts as a 
 support for an inverted globular flask 
 which serves as a recipient. This arrange- 
 ment, shown in Fig. 232, is admirable for 
 the sublimation of substances, the volatile 
 products of which are so aggregated as to 
 form what are called flowers. 
 
 Sublimation in Retorts. Glass retorts 
 are more expensive and less convenient 
 than flasks, except for the sublimation of 
 very volatile matters. They are arranged 
 as shown by Fig. 238, the beak, like the 
 neck of the flask, leading into a wide- 
 mouthed receiver. The alembic, Fig. 233, is frequently substi- 
 tuted for retorts, and is more convenient, as its head being de- 
 tached from the body allows the more easy removal of the 
 sublimed product. 
 
 Fig. 233. 
 
 Fig. 234. 
 
 Earthenware retorts with loose heads, Fig. 234, to be fastened 
 by pins and lute, are employed for sublimations requiring high 
 temperatures. 
 
 Sublimation in Crucibles. The crucible for this purpose may 
 be of clay, platinum, or iron, according to the nature of the sub- 
 stance to be heated. It is first coated with a layer of refractory 
 
SUBLIMATION IN SHALLOW VESSELS. 319 
 
 clay paste, and when this is dry, placed over a furnace fire. An 
 inverted crucible of the same size with a small hole in its top, is 
 then placed over as a recipient of the vaporized particles. The 
 top crucible must be above and out of the fire. When the opera- 
 tion is finished, and the apparatus has cooled, the top may be 
 removed and the crucible emptied of its contents. 
 
 Sublimation in Shallow Vessels. In the treatment of sub- 
 stances which sublime at a low heat, a plate or capsule resting 
 upon hot sand and surmounted by a glass funnel or a cone of 
 glazed paper, as a condenser and recipient, answers every pur- 
 pose, particularly in the sublimation of organic substances. The 
 top of the funnel and cone should be drawn. out to a small open- 
 ing, and when the operation is finished the contents of the refri- 
 gerant may be removed by a feather. 
 
 When iron capsules are used, as is often necessary in sublima- 
 tions requiring high heat, they should be lined with a thick dough 
 of fire clay. Capsules with flat bottoms and of thick sheet iron 
 are most appropriate. Their dimensions may be six inches in 
 diameter, and J to 1 inch in depth. The top B must be of earthen^ 
 ware and detached. The arrange- 
 ment is shown in Fig. 235. This Fi s- 235 - 
 implement requires a furnace heat. ^ -~^ B 
 The cover should be tightly ce- ^ /' ^"^^~~~^ U 
 rnented with fire lute, and when 
 
 the whole has cooled, the cover may be taken off and the adhe- 
 rent mass of sublimate removed with a spatula. The small cone 
 c is to be kept over the hole in the cover to arrest any escaping 
 vapors. When it is necessary to probe the cavity, it may be 
 temporarily removed with the tongs. 
 A diaphragm of porous white paper Flg- 236< . 
 
 will arrest the passage of any empy- 
 reumatic matter, and pass the subli- 
 mate free from color. 
 
 Two very concave watch-glasses, 
 placed the one upon the other with 
 their convex surfaces outward, make 
 a very neat subliming apparatus for 
 minute quantities of rare matter. 
 
 Flat vessels, with tall conical caps, Fig. 236, are also made of 
 biscuit and earthenware for subliming operations. 
 
320 
 
 IIYDRO-SUBLIMATIOX. 
 
 Ures Apparatus. This is a very convenient arrangement, 
 Fig. 237, consisting of two metallic, glass, or porcelain 
 Fig. 237. ygggeig. The lower one is the recipient of the matter 
 to be sublimed, and the upper #, which is the larger, 
 covers the former, and is to be filled with cold water, 
 to be replaced as fast as it evaporates. When the pro- 
 cess is completed, the sublimed matter can be removed 
 from the exterior of the cover. 
 
 Henry's Apparatus for Hydro- Sublimation. This arrange- 
 ment, shown in Fig. 238, has been proved by experience to be 
 
 * ,* Fig. 238. 
 
 practically useful. It is employed in manufacturing laboratories 
 for the sublimation of calomel, but is equally applicable for other 
 substances ; and, by lessening the dimensions of the several pieces, 
 may be made very convenient for experimental purposes. 
 
 It consists of a large globular glass vessel a, with a long 
 straight neck, and two short, lateral tubulures of equal width. 
 For manufacturing purposes the globe must be of stoneware, and 
 of two or more gallons capacity. In either case it rests upon 
 the ledge of a blue stone-ware cylinder A, containing sufficient 
 water to close the neck of the globe, which dips lightly into it. 
 One of the tubulures receives the neck of the retort 6, and the 
 other that of the still, Fig. 25, which furnishes the steam, or, 
 what is better, a conduit pipe from the generator, Fig. 13 or 14. 
 The retort 6, of earthenware, or iron, coated interiorly with fire 
 clay, is for the evolution of the calomel or sublimate in vapors. 
 It is wholly enclosed in the furnace, and its very short neck passes 
 
HYDRO-SUBLIMATION. 
 
 321 
 
 Fig. 239. 
 
 immediately from it into the globe a, so as to prevent the con- 
 densation of the sublimate in the neck and upper portion. The 
 joints should be tightly luted. The success of the operation de- 
 pends mainly upon a proper management of the fire and supply 
 of aqueous vapor. The heat should be just sufficient to drive 
 over the sublimate slowly, and the steam should be supplied in 
 large excess, and simultaneously with the appearance of the 
 vaporized solid. For this purpose the steam-conduit must be 
 fitted with a cock for the regulation of the flow of its contents of 
 vapor. As soon as the sublimed mole- 
 cules come in contact with the aqueous 
 vapor, they are condensed in the globe a, 
 and precipitate as powder (p. 100) into h. 
 
 By increasing the size of the globe 
 a, threefold, diminishing the orifice of 
 its neck by means of a small glass 
 tube passing through a perforated cork, 
 and by omitting the tubulure on the other 
 side, the steam may be dispensed with 
 for the sublimations of volatile solids into 
 flowers. The neck in this case must point 
 upwards. 
 
 For experimental operations, a small earthenware retort and 
 
 Fig. 240. 
 
 glass globe will answer every purpose. The steam can be sup- 
 
 21 
 
322 DISTILLATION. 
 
 plied from the copper washing bottle, Fig. 240, by substituting 
 for the spirting tube d, a flexible leaden pipe <?, which is to be 
 connected with the neck of the flask by a coupling-screw a. The 
 gas or spirit lamp will furnish ample heat for the generation of 
 steam in this apparatus. 
 
 DISTILLATION. 
 
 A process by which substances are heated for the separation 
 of a volatile from a more fixed portion. The apparatus for the 
 purpose consists of a close vessel in which the heating takes 
 place, a refrigerant for the condensation of volatilized particles, 
 and a recipient for the retention of the product ; the two latter 
 purposes being often, however, fulfilled by the same vessel. 
 When this product condenses as a fluid, the process takes the 
 name of liquid distillation, and if as a gas, of gaseous distilla- 
 tion. The subjection of a body to very high heat, for the pur- 
 pose of decomposing it and receiving the generated products, is 
 called dry or destructive distillation. In SUBLIMATION, which 
 may be styled solid distillation, the volatilized matter is received 
 and condensed in one vessel without the necessity of an interme- 
 diate refrigerant. 
 
 The process of distillation is one of the most indispensable in 
 chemical investigation, as by its aid we can not only separate 
 liquids of different volatility, but also collect new volatile pro- 
 ducts which may result from the decomposition of single or mixed 
 substances. As instances of its valuable use, we can by its aid 
 separate the essential oil and volatile constituents of plants and 
 of other materials, recover alcohol, ether, or any valuable vola- 
 tile liquid, from solutions in which they are solvents, refine a 
 liquid from its fixed impurities, free it from fixed matter which 
 it may have in solution, and, aided by an absorbent material, 
 remove any contained water. Moreover, it allows the collection, 
 either free or in solution, of gases generated by chemical re- 
 action. .^ 
 
 The Still. The still is the common implement used in large 
 operations of liquid distillation. It is generally made of copper, 
 and is tinned internally. A convenient form has already been 
 fully described at page 52. The following figure exhibits 
 another of handsomer appearance, but constructed upon similar 
 
THE STILL. 
 
 323 
 
 principles. It is mounted in brickwork, but can as readily and 
 with as good results, have its position in the more economical iron 
 cylinder, Fig. 24. 
 
 Fig. 241. 
 
 By way of illustrating the necessary manipulations, we will 
 describe the different steps of the operation as commonly per- 
 formed. 
 
 The substance to be distilled is placed in the body A, the 
 pewter or tinned^ copper head c, is luted on and adjusted to the 
 pewter worm B, and the fire is lighted in the furnace. To insure 
 facility of management, the several parts of the arrangement 
 should be made to fit accurately to each other. As the heat 
 increases, the contents of the body or cucurbit begin to boil, and 
 that portion volatilizable at the temperature of the applied heat 
 mounts in vapor to the head or capital c, there partially con- 
 denses, runs into the beak or neck D, and ultimately into the 
 spiral worm E B, where, together with any uncondensed vapor, it is 
 liquefied and cooled by the surrounding water previous to its exit 
 into the recipient P, which may be an open pan if the product is 
 not volatile, and a glass bottle or carboy if it is. The cooler 
 I j K L, in which the worm is immersed, consists of a wooden 
 cistern filled with water, which requires to be constantly cool, 
 and therefore must be frequently renewed. For this purpose, 
 there is a conduit N M attached, which receives cold water from 
 the hydrant pipe R, and conveys it in a constant stream to the 
 bottom of the cistern, so that it may displace the heated water, 
 
324 
 
 THE COOLER. 
 
 which has become lighter by expansion, through the lateral out- 
 let at the top. This water, already heated, can be more econo- 
 mically used for making distilled water than when cold, as it 
 takes less fire to boil it when transferred to the still. If the 
 cistern is kept clean, it makes an excellent reservoir for the 
 supply of hot water to the laboratory, as the still is frequently in 
 use for making distilled water, and for other purposes. 
 
 When fresh additions of liquid are to be made they can be 
 poured through the tubulure A. This saves the trouble of taking 
 off the head of the apparatus, which need only be removed after 
 the completion of the operation for the purpose of cleaning the 
 still and its parts. As the residuum is, in many instances, as 
 much the object of the process as the distillate, it must, when 
 such is the case, be carefully removed from the still, and trans- 
 ferred to a suitable vessel for preservation or further reaction. 
 
 The size of the still varies with the amount of material to 
 be operated upon. For the ordinary purposes of the labora- 
 tory it need not exceed fifteen gallons capacity. It must be 
 proportioned so as to have as much heating surface as possible, 
 while, at the same time, its height is sufficient for the foaming 
 and frothing of its contents without danger of their boiling over 
 into the neck. 
 
 We have described a spiral worm, because that is the usual 
 form of refrigerants, an important point 
 in the construction of which is to pro- 
 vide as much cooling surface, and conse- 
 quently as great a length of pipe as pos- 
 sible in a small space. Schrader's con- 
 denser, Fig. 242, which is preferred by 
 some manufacturers, because more easily 
 cleaned, consists of a metallic ball, the 
 upper part of which projects above the 
 water contained in the cooler. From the 
 lower side of this ball three straight tubes 
 proceed, and conduct the vaporized par- 
 ticles downwards into the exit tube with 
 which they connect. The exit tube is 
 closed at its upper end with a cock, and 
 open at the other for the escape of the condensed liquid. Gedda's 
 
 Fig. 242. 
 
DISTILLATION IN RETORTS. 325 
 
 condenser, already given at p. 48, is still more convenient than 
 either of the two preceding. 
 
 Whatever the form of the refrigerant, its mode of action is the 
 same. It is constructed so as to facilitate as much as possible 
 the perfect and rapid condensation of the enclosed vapors. The 
 greater the amount of surface which it presents to the water, the 
 more effectual its action ; for the sooner the heat, absorbed by the 
 distillate in assuming the gaseous form, is abstracted by the sur- 
 rounding water, the more rapidly it becomes condensed and 
 cooled. The condensation may be hastened by surrounding the 
 recipients with a frigorific mixture, which, if the vessel be of 
 glass, must be at first applied gradually, lest its too sudden cool- 
 ing causes its fracture. 
 
 Volatile liquids are distilled by the heat of BATHS ; and for 
 those liquids which corrode metals, a stoneware still must be 
 used. 
 
 Distillation in Retorts. Retorts are egg-shaped vessels, an- 
 swering a more convenient purpose than the still in the nicer 
 distillatory operations. They are mostly of glass, but for some 
 processes those of porcelain, earthen and stoneware, platinum 
 and iron, are necessary. Retorts are also used in technical ope- 
 rations, and the laboratory should be supplied with a series 
 ranging from those of a half ounce up to several gallons capa- 
 city. Glass retorts should be made of hard, white glass, free 
 from lead. Those of German crown-glass are very thin, but of 
 uniform thickness and of sufficient strength, and moreover with- 
 stand both high temperatures and the corrosive action of acids 
 and alkalies. The surface must be perfectly smooth and free 
 from blur or striae. 
 
 Some judgment is required in the selection of retorts. One 
 properly constructed is exhibited in Eig. 243. It is seen that 
 the neck proceeds laterally from the summit of the body, forming 
 a wide tube at its origin, which tapers gradually into a narrow 
 beak. The arch of the retort should be so fashioned as to 
 reverberate any particles of boiling matter that may spirt up- 
 wards against it, and thus prevent their overflow into the beak. 
 A large neck facilitates the process, because it allows more room 
 for the accumulation of vaporized matter, and presents a propor- 
 tionally less surface to the cooling influence of the atmosphere. 
 
326 
 
 DISTILLATION IN RETORTS. 
 
 It is very essential that the curve between the neck and the 
 body #, Fig. 243, should be so formed as to make the straight 
 line a b form an obtuse angle, with the dotted line b a. If, on 
 the contrary, it is made as shown by Fig. 244, which presents the 
 
 Fig. 243. 
 
 Fig. '244. 
 
 Fig. 245. 
 
 usual form of those sold in the shops, the vapors, condensing in 
 the arch as far as the dotted line a 6, fall back again into the 
 body, whilst, in Fig. 243, the dividing line, from which the dis- 
 tillate commences to flow, is much nearer to the body. So that 
 a retort like Fig. 243, will distil twice as rapidly as another 
 similar to Fig. 244, which, however, when it has the form shown 
 by the dotted lines c d a, becomes equally convenient. 
 
 The pear-shaped retort, Fig. 248, being deeper in the body 
 or bulb, is better fitted for distilling volatile substances, and 
 others which foam and swell upon being heated. The globular 
 form, Fig. 245, presents less depth, but more heating surface, 
 and is, therefore, better adapted to those liquids which boil 
 quietly and distil more slowly. 
 
 A great improvement to the plain retort, is the addition of a 
 glass stoppered tubulure to the neck, as at Fig. 245. The tubu- 
 lure should have its position exactly as shown in the cut, so that 
 the vapors condensing about it may flow back. Tubulated retorts 
 are preferable, because they are more readily cleansed and 
 charged than those of plain shape ; moreover, they admit of fresh 
 
DISTILLATION IX RETORTS. 
 
 327 
 
 additions to their contents without the necessity of disturbing 
 the arrangement. 
 
 The vessels into which the distillate from the retorts passes are 
 technically termed receivers. Fig. 246. They should be of glass, 
 except in a few special cases, and always free from lead ; care 
 being observed, at the same time, to select those which, while 
 thick enough for strength, will be sufficiently thin to bear sudden 
 changes of temperature. The usual shape is that of a globe with 
 
 Fig. 246. 
 
 a neck, widening gradually towards the mouth, for the reception 
 of the tapering ends of the retorts. 
 
 To render them available for connection with other apparatus 
 besides the retort, as shown by A, Fig. 246, they are often fitted 
 
 Fip. 247. 
 
 with tubulures. In rare cases, the long neck tube is replaced by 
 a tubulure. The interior of the tubulures should be perfectly 
 
328 
 
 DISTILLATION IN RETORTS. 
 
 round and smooth, so that corks may be tightly fitted in them 
 according to necessity. 
 
 If the distillation is to be urged over an Argand lamp, the 
 neck of the receiver to be attached to the retort should be long, 
 and the connection made by inserting the beak of the latter in 
 its mouth. Fig. 247, and by rendering the joint air-tight with a 
 wrapper of india-rubber cloth, as shown at R in the figure. The 
 funnel D is charged with water, which flows in a thin stream, 
 regulated by the cock in the barrel, upon the receiver, covered 
 with sponge or bibulous rags, and resting in a capsule c. 
 
 If the retort is to be heated in a furnace, the junction of the 
 beak with the tubulure of the receiver is tightened by means of a 
 perforated cork through which the beak passes, and sealed, if 
 necessary, by a coating of flaxseed and whiting lute, as shown 
 at R, Fig. 248. The receiver B, resting upon a straw ring in 
 
 Fig. 248. 
 
 a wooden pail, is cooled by a stream of water from the hydrant 
 pipe ij which, as it becomes warm, flows off into the funnel d 
 leading into the drain. 
 
 In order to increase the surface of the beak, and consequently 
 
 249. 
 
 to facilitate the liquefaction of the vapors passing through it into 
 the receiver, there is often placed between the beak of the retort 
 
 
DISTILLATION IN RETORTS. 
 
 329 
 
 and the tubulure of the receivers, but connected with both, an 
 adapter, Fig. 249. This is a pointed conical tube of white glass, 
 free from lead, which, when leading from a condenser to a bottle, 
 
 Fig. 250. 
 
 takes a bent form, as shown at A in the same figure. Fig. 251 
 exhibits a complete arrangement of a distillatory apparatus, com- 
 bining a tubulated retort with an s tube, an adapter, a recipient 
 placed in a vessel with a constant stream of cold water flowing 
 into it, and a syphon-tube with a second receiver. The curved 
 adapter is needed where the receiver rests vertically instead of 
 horizontally. 
 
 As it is requisite frequently, in distilling volatile liquids, to 
 have a larger extent of cooling surface than is presented by the 
 globular receiver, another form has been devised by Liebig, which 
 is very convenient. It consists of a glass tube , 25 to 30 inches 
 long and two inch bore, connected with the beak of the retort, 
 and running through a sheet brass cylinder ft, of 20 inches in 
 length and two or more inches diameter. The metal tube is 
 closed at each end with perforated corks, through which the glass 
 rod passes, and is held in a central position. A constant stream 
 of cold water, supplied through the funnel-tube <?, passes into the 
 cylinder, surrounds the glass tube, condenses the vapor therein 
 contained, and, becoming warm, passes out through the exit pipe 
 d, to give place to cooler water. The figure below exhibits one 
 
330 
 
 DISTILLATION IN TUBES. 
 Fig. 251. 
 
 mounted upon an iron stand, with joint and sliding rod ; from 
 which, for small operations, it may be detached and supported 
 by a wooden clamp. 
 
 Fig. 252. 
 
 For micro-chemical distillations, the necessary apparatus may 
 be formed of glass tubes blown into proper shape over the blow- 
 pipe table. Fig. 252 exhibits Clarke's tube retort and receiver : 
 a the retort, of an ounce capacity ; b the receiver, 8 by three 
 
PLATINUM RETORTS. 331 
 
 X 
 
 quarter inches, and c the distilled liquor. The junction of the 
 retort and receiver (d) should be hermetical. 
 
 Plain bulbs a, and tubulated , Fig. 253, are other forms : 
 the tube b of the latter serves for the 
 suction of the liquor to be heated, and 
 may afterwards be sealed in the flame of 
 a spirit-lamp. 
 
 The means of heating these small ves- 
 sels, are the small spirit-lamps, Figs. 151, 
 152, except when it is required to modify 
 the heat by the intervention of a sand- 
 bath, which requires a larger lamp. The 
 clamp supports, p. 186, heretofore described, are of very great 
 convenience in the adjustment of these tube arrangements. 
 
 A simpler form of tube retort is shown in Fig. 254. It is 
 
 Fig. 254. 
 
 readily made by closing a tube at one end and bending it in a 
 zigzag direction, as represented in the drawing. The liquid to 
 be distilled is at #, and the recipient at b. To render it appli- 
 cable to the generation and collection of gases, the tube may be 
 drawn out at its open end and bent downwards, if necessary, to 
 reach the receiver, 
 
 Platinum Retorts. The size of these vessels varies from a 
 quart down to an ounce, these capacities being 
 adapted to all the purposes of an analytic Fig. 255. 
 
 and pharmaceutic laboratory. The usual 
 form is shown in Fig. 255. The body a is 
 nothing more than a stout crucible with a 
 thick rim d. The head b, with the helm <?, 
 should be hammered from one piece, or else 
 very closely welded together, and it should be 
 ground at its rim so as to fit perfectly to the mouth of the still. 
 
 Platinum stills are very useful for destructive distillation, for 
 determining the amount of matter, if any, lost by substances at 
 
332 
 
 IRON RETORTS. 
 
 a red heat, for the distillation of matters not readily volatilized, 
 of those which corrode glass, &c., and consequently as a substi- 
 tute for lead in the preparation of fluohydric acid. 
 
 Those of a large size should be fitted with handles, so as to 
 diminish their liability to defacement by transfer from place to 
 place. When heated over charcoal, they should be well payed 
 over with an external coating of fire-clay paste. Otherwise, the 
 directions for using the platinum still are the same as those 
 given for the crucible at p. 283. The gas or spirit lamp will 
 furnish the amount of heat required for most operations. 
 
 Iron Retorts. All iron retorts may be of cast metal. A 
 very neat form for small operations is 
 shown by Fig. 256. A simpler and more 
 economical apparatus is a mercury flask, 
 with an iron gas tube or gun barrel 
 screwed into the top, and reaching nearly 
 to the bottom, and another tube bent 
 downwards. This arrangement, well 
 
 fitted for distilling dry substances which require a high heat, 
 may be modified by removing the centre pipe and inserting a 
 screw-plug, and thus be made well adapted to the distillation of 
 mercury. For distilling naphtha, caoutchicine, and similar sub- 
 stances, the usual form of a glass retort is sometimes preferred. 
 
 Fig. 257. 
 
 Fig. 256. 
 
 Fig. 257 exhibits an iron crucible retort, with a cover, which 
 is held close to the body by means of a clamp, when the retort 
 is in operation. A bent gas-tube carries off the distillate into a 
 receiver. 
 
 Plate iron retorts, sometimes used for the generation of gases 
 
GENERAL RULES FOR DISTILLATION. 333 
 
 by high heat, are referred to in the distillation of volatile sub- 
 stances. 
 
 All of these iron retorts are heated in furnaces. When not 
 in use, they should be greased to prevent oxidation, and should 
 be kept stoppered. One per cent, of platinum, it is said, renders 
 iron resistant to acid and corrosive liquids. 
 
 Porcelain Retorts. These implements, of shape similar to 
 those of glass, are only used for dry distillations ; but being 
 fragile, require to be very carefully heated. Being opaque, they 
 have not the advantage of glass, which allows the inspection of 
 the contents of the vessel. 
 
 Earthenware and Stone Retorts. The application of this ware 
 to the purposes of distillation is very limited. To render it im- 
 permeable by gases, the retorts should be wet with a solution of 
 borax, or else payed over with a coating of paste made from 9 
 parts of clay and 1 part of powdered borax, and then heated to 
 fusion and gradually cooled. The usual form is that of the glass 
 retorts. 
 
 Q-eneral Rules for Distillation. In the distillation of sub- 
 stances which require a high heat, the vessel may be placed over 
 the naked fire. If it is a metallic still, the cylinder, Fig. 24, 
 affords every convenience for heating by this method. The uni- 
 versal furnace, Fig. 134, is the proper heating implement for 
 earthen and metallic retorts ; and the spirit or gas lamp for those 
 of glass and porcelain. When the nature of the process requires 
 a modification of the heat, it can be accomplished by means of 
 intermediate BATHS, which will furnish any temperature required 
 up to the boiling-point of the medium employed. 
 
 Glass and porcelain retorts should, if possible, never be heated 
 over the naked fire, because of their great liability to fracture. 
 The impossibility of maintaining a uniform heat is a serious 
 objection to this mode, for the ebullition, though rapid, is not 
 uniform. When it is necessary to use the naked fire for glass 
 and porcelain retorts, the same directions are applicable to their 
 management as to that of earthen or metallic retorts, though in 
 the use of the latter less care is requisite. The proper position 
 of the retort is in the centre of the furnace, Fig. 238, upon a 
 crow-foot or support, Fig. 43, resting on the grate. The retort 
 
334 GENERAL RULES FOR DISTILLATION. 
 
 having been previously charged, its beak is then adapted to the 
 receiver, and the joints closed by lute. A very small fire is then 
 ignited and increased as the retort has become warm, till it 
 reaches to within a line or two of the level of the contained 
 liquid. If the coals project beyond this point, the surface of the 
 dry or upper part of the retort acquires a temperature so much 
 higher than that of the substance which is being heated, that the 
 difference may cause its fracture when particles are projected 
 against it. A certain degree of heat in the upper part of the 
 vessel is, however, necessary, so that the opposite condition the 
 condensation of vapor in it, may not occur ; and where the retort 
 is heated unequally, it is sometimes necessary to place over it the 
 dome of the furnace. For the same reason, also, when a retort 
 is heated over a spirit or gas lamp, or by any other way in which 
 the upper portion is exposed, that part should be covered with a 
 dome. Fig. 258 exhibits such a one of earthenware for large 
 retorts. A cone of pasteboard, Fig. 259, will answer better for 
 
 Fig. 258. Fig. 259. 
 
 smaller vessels. The notch in the front allows its adaptation to 
 the neck ; but while adjusted so as to effectually protect the upper 
 part of the retort from contact with air, it must be supported in 
 such a manner that its weight, when great, shall not endanger 
 the safety of the retort. 
 
 The addition of the fuel should be gradual, so that the fire 
 may be only sufficient to gently boil the contained liquid. The 
 coals should be first ignited to expel moisture ; and when the 
 operation is nearly completed, the fire must be skilfully managed. 
 For greater safety, the glass retorts should always be coated ex- 
 teriorly with a paste of refractory clay, or enveloped at the 
 lower part with wire gauze. 
 
DISTILLATION OF LIQUIDS. 335 
 
 When the Argand or gas lamp is used as the means of heating^ 
 the retort need only be arranged upon a support and brought 
 over the flame, which is to be applied gradually at first, and 
 slowly elevated until the glass has become heated throughout. 
 To diffuse the heat and prevent the direct contact 
 of the flame, the ring of the support upon which Fig - 26 - 
 the retort rests, should have a wire gauze bowl, 
 Fig. 260, for the holder. 
 
 Fig. 248 exhibits a retort properly located in a 
 SAND-BATH, this being the mode of heating retorts 
 for the distillation of volatile liquids, such as ethers and the like. 
 The advantage of the sand-bath over the naked fire for heating 
 glass retorts, particularly those of large size, is that it imparts a 
 more uniform degree of heat, and prevents the possibility of 
 fracture from sudden changes of temperature. The sand should 
 be fine, and the layer, upon which the bottom of the retort rests, 
 about an inch or two deep, according to the size of the retort. 
 The sand surrounding the retort should only reach to the level 
 of the contained liquid, and should be removed gradually as it 
 evaporates. 
 
 To prevent condensation in the top, the upper portion of the 
 retort may sometimes be advantageously covered with a woollen 
 cloth. 
 
 When the operation is performed with a view to separate two 
 liquids which boil at different temperatures, the retort must be 
 either set in a bath which does not exceed the temperature at 
 which the more volatile liquid escapes ; or else, when otherwise 
 heated, the temperature must be regulated by a glass thermo- 
 meter, Fig. 120, entering the retort through its tubulure, and 
 adjusted by a perforated cork. 
 
 When the boiling-points of different liquids are nearly equal, 
 the density of one of them may sometimes be increased by the 
 addition of some soluble matter, which, if both liquids are to be 
 saved, can afterwards be readily removed. 
 
 Too sudden ebullition must, in all cases, be avoided, and the 
 fire should be gradually increased, whether the heating vessel be 
 of glass or metal. The only exceptions to this rule occur in the 
 use of water or saline baths. 
 
 DISTILLATION OF LIQUIDS. The STILL is the most convenient 
 
336 
 
 DISTILLATION OF LIQUIDS. 
 
 implement for the distillation of large quantities of material. 
 Retorts are more applicable to nicer operations. 
 
 The arrangement of a retort for the process of distillation is 
 very analogous to that of a still. The body is the recipient of 
 matter to be heated, and is the portion to* which heat is applied ; 
 the beak is the condenser, and the glass receiver, the recipient of 
 the distillate. The exit nozzle fitting upon the end of the worm 
 and leading into the recipient, should never project so far as to 
 dip into the distillate. If a globular receiver is not at hand, an 
 ordinary glass bottle for retort distillations, or a carboy for those 
 in the still, are excellent substitutes, as it is very easy to make 
 the connection by using a curved adapter, Fig. 249, and adjust- 
 ing it to the mouth of the receiver, as in all other cases, through 
 a perforated cork. 
 
 Sometimes the receivers themselves are drawn out at the neck 
 into a tube which enters a flask, as at Fig. 260, or else the tubu- 
 lure is fitted with a perforated cork for the passage of a tube, 
 which answers as well the purpose of a conduit. The flask 
 
 Fig. 261. 
 
 Fig. 262. 
 
 which receives this tube is also fitted with a perforated cork, 
 through which passes another tube c, Fig. 261, for the escape of 
 uncondensed vapors. 
 
 The refrigeration of the receiver is readily accomplished by 
 either of the arrangements shown at Figs. 247, 248, 250. 
 
 The uncondensed gases are allowed exit through a small glass 
 tube, adapted to the tubulure in the top of the receiver, and lead- 
 ing upwards under a hood, or else downwards into a bottle of 
 some fluid, which absorbs them, and thus prevents the contami- 
 nation of the atmosphere. 
 
DISTILLATION OF LIQUIDS. 337 
 
 It is of great importance that the vessels in use for distillation 
 should always be free from foreign substances ; and both the re- 
 tort, still, adapter, and worm, immediately after each process, 
 should be cleansed by repeated rinsings with water, so that they 
 may be clean and ready for the next operation. 
 
 As the ebullition of certain liquids is attended with foaming 
 and spirting, it is necessary to break the force of these sudden 
 eruptions of vapor, by some mechanical means. This can be 
 effected often by the addition of platinum scraps to corrosive 
 liquids, and of fragments of glass to those which boil at low tem- 
 peratures and are without action upon that substance. This pre- 
 caution prevents damage to the vessel, and allows the boiling to 
 proceed tranquilly. The use of the water bath obviates the 
 necessity of this preventive, and is almost indispensable in the 
 distillation of liquids holding in solution certain vegetable princi- 
 ples, which are sensitive to the decomposing influence of heat. 
 
 In distilling oil of vitriol in a glass retort, the deposition of 
 sulphate of lead endangers the safety of 
 the retort, and the purity of the distillate, Fig ' 263 ' 
 
 by an explosive ebullition. To avoid this 
 difficulty, Berzelius sets the retort one- 
 third into the truncated cone of sheet 
 iron, Fig. 263, strews sand around the 
 edge of the cone, surrounds it with brick, 
 and hangs a flat cone of sheet iron about 
 
 a half inch above the retort. The retort is half filled with acid, 
 and coals placed on the cone inside the bricks. Another method 
 of Berzelius is to precipitate the lead salt by dilution with water, 
 to concentrate the acid in a platinum capsule, and, finally, to 
 distil in a dome-topped furnace, a quiet distillation being pro- 
 moted by the introduction of platinum wire into the retort. 
 
 If the retort is tubulated, there is no difficulty in charging it 
 neatly, because its contents can be added, without danger of 
 spilling, through a wide-barrelled funnel ; but when plain, it is 
 necessary, in order to prevent the adherence of particles to the 
 sides of the beak, to stand it on end, as shown in Fig. 264, and to 
 fill it through the neck by means of a straight funnel-tube with 
 its barrel reaching to the bottom. 
 
 The matters, if solid, should always be bruised or triturated to 
 
 22 
 
338 
 
 DISTILLATION OF LIQUIDS. 
 
 Fig. 264. 
 
 powder and added portionwise. In this way the neck of the 
 retort is kept clean. 
 
 The joints of retorts and glass distillatory vessels may be luted 
 with strips of muslin soaked in a solution of bone 
 glue. Those of metallic vessels, with a dough 
 of whiting and flaxseed meal, which, when dry, 
 may be rendered still more impermeable, by a 
 covering of muslin, prepared as above, with bone 
 glue. When one vessel is adapted to the other 
 by means of perforated corks, these latter should 
 be payed over with wax or more economically 
 with the flaxseed or whiting dough. If the dis- 
 tillate decomposes organic matter, the use of 
 corks, flaxseed, and similar means, must be 
 avoided, and the joints made tight by using ap- 
 paratus, the connecting parts of which are nicely 
 adapted to each other by ground joints. 
 
 All matters which readily generate very volatile products 
 should be distilled over BATHS, of which those made of liquids 
 are to be preferred. It is very easy to arrange 
 the retort in a suitable vessel, by resting it upon 
 a braided straw ring, Fig. 265, and steadying 
 its neck in a clamp support. The beak of the 
 retort should also be elongated by attaching it 
 to a Liebig condenser, Fig. 267, so as to extend the cooling sur- 
 face. If the distillate is readily condensable, the receiver may 
 
 Fig. 266. 
 
 Fig. 265. 
 
 be kept sufficiently cold by a bath of cold water, as shown in 
 Figs. 250, 266 ; otherwise the use of FRIGORIFIC MIXTURES 
 
DISTILLATION OF LIQUIDS. 
 
 339 
 
 becomes necessary. The mixture should entirely surround the 
 recipient, and as it becomes warm or liquefies, new portions must 
 be added. If ice or other solid is used, the syphon in position, 
 as shown at 6, Fig. 266, will keep the pail constantly free from 
 the liquefied excess. 
 
 The proper arrangement of an apparatus with Liebig's con- 
 denser, is shown in Fig. 267. 
 
 Fig. 267. 
 
 In the distillation, particularly of essences and oils, the mate- 
 rial, if it is ligneous, must be soaked, previous to its transfer to 
 the still, in which it should be made to rest upon a cullendered 
 diaphragm, Figs. 22, 27, to prevent contact with the heated 
 bottom of the vessel. A proper vehicle is then added, and the 
 operation continued by the application of heat. The water, or 
 other liquid, and volatile matter are vaporized, and the two be- 
 coming involved pass over together. When these two products 
 differ in density, as is commonly the case, a very convenient 
 means of separating them as they pass 
 over, is afforded by the Florentine re- 
 ceiver, shown in Fig. 268. A is the 
 body of the recipient, and D its mouth 
 through which the distillate enters. 
 The tubulure B is for the reception of 
 the beak (a curved glass tube), c. As 
 soon as the condensed distillate reaches 
 the receiver, the lighter body rises to the top, and there retains 
 its position, and when the contained amount of the two fluids 
 
 Fig. 268. 
 
340 
 
 DISTILLATION OF GASES. 
 
 Fig. 269. 
 
 reaches the level of the mouth of the beak, the one which is most 
 dense runs off. The level being kept thus constant, the lower 
 stratum of fluid is separated from the upper as fast as any distil- 
 late comes over, leaving the lighter liquid to be emptied from the 
 receiver after the completion of the process. 
 
 If the heavier product is the object of the distillation, as is 
 sometimes the case, then the form of the reci- 
 pient may be with advantage varied, as shown 
 in Fig. 269. The stop-cock in the barrel 
 allows its separation and discharge from the 
 lighter body as soon as a sufficient quantity 
 has subsided. 
 
 When volatile oils and some other bodies 
 are obtained by the above process, the water 
 which is generally employed as the vehicle, 
 and which is separated as we have described, 
 should be reserved, for being already more or 
 less charged with volatile matter, it may be 
 economically used in redistilling the same 
 material, in case it should yield its product 
 reluctantly. This repeated distillation of the 
 . distillate over the same material is termed 
 
 Cohobation, and is resorted to necessarily, in many instances, that 
 the material may be entirely exhausted of its volatile matter. 
 
 Rectification is the redistillation of the distillate, either alone 
 or with some absorbent material to free it from water, acid, or 
 other impurity. 
 
 DISTILLATION OF GASES. The term distillation cannot, in 
 all instances, be applied with entire precision to the processes 
 concerned in the manufacture of gases. But, as gaseous bodies, 
 when intended to be retained, are usually prepared by modes pre- 
 cisely similar to those employed in liquid distillation, it has been 
 thought proper to introduce their consideration in this place. 
 
 The generation and distillation of gases are generally made 
 simultaneous operations. As their elasticity is such as to prevent 
 condensation by ordinary means, they are either collected in 
 solution with water, or other fluid, or in their gaseous state in 
 gasometers. The arrangement of the required apparatus, though 
 
DISTILLATION OP GASES. 
 
 341 
 
 bearing analogy to that for ordinary distillations, differs in many 
 little but material points. 
 
 If the gas is readily evolved without the aid of heat, as in the 
 case of hydrogen, carbonic acid, sulphuretted hydrogen, &c., the 
 generator may be a simple flask A, Fig. 270. This flask is the 
 
 Fig. 270. 
 
 recipient of the material from which the gas is to be eliminated. 
 The funnel-tube B, reaching nearly to its bottom, is the inlet of 
 the acid, or other reagent, by which the action is to be produced, 
 and the bent tube c is for the exit of the disengaged gas. An 
 ordinary wide-mouth green glass bottle will answer the purpose 
 excellently in most cases, as exhibited in Fig. 271, which shows 
 an apparatus of this kind for passing gas through liquids, when 
 its absorption is required, as in the precipitation of solutions in 
 analysis. When the generator is to be connected with a com- 
 bustion or DESICCATION tube, as at Fig. 218, the bent tube can be 
 removed. In this instance, and, indeed, with better results in all 
 cases, the angular tube should be blown with a bulb in its centre 
 for the reception of a plug of raw cotton, which intercepts the 
 passage of liquid, and solid particles of foreign matters. 
 
 The exit tube is frequently divided into two pieces, and con- 
 nected together by a piece of india-rubber tubing, as shown by 
 Fig. 271. A flexible joint, B, is thus formed, and affords the con- 
 venience of giving the tube any required direction. 
 " When, in particular instances, it is inexpedient to use the 
 
342 
 
 DISTILLATION OF GASES. 
 
 funnel-tube, the generating bottle or flask may have the form 
 presented by Fig. 272, which shows the exit tube issuing from a 
 tubulure in one entire length, with two angular bends. 
 
 Fig. 271. 
 
 Fig. 272. 
 
 For certain operations, the bottle and delivery-tube are in one 
 piece, the part A, or mouth, forming the funnel tube ; B the 
 flask portion or generating chamber ; and c the exit tube. This 
 
 Fig. 273. 
 
 Fig. 274. 
 
 arrangement is adapted to experiments with corrosive gases, 
 which act upon artificial joints and loosen them. When made of 
 diminutive size, and with a long exit tube, as shown by Figs. 274, 
 275, they are very convenient for small experiments and testing, 
 such as passing gas into test-tubes and the like. 
 
 The usual form of funnel-tubes is as shown by B, Fig. 270, which 
 consists of a straight tube surmounted by a funnel. This funnel 
 
DISTILLATION OF GASES. 
 
 43 
 
 Fig. 276. 
 
 is sometimes made as at Fig. 299. To save the necessity of 
 boring separate holes in the cork for the funnel and the exit or 
 delivery-tube, Vogel combines the two in one piece, as seen at 
 Fig. 276. The main stem is an ordinary funnel-tube e d, to 
 which is joined a short piece of wider tube a 5, with 
 a lateral branch f g o. The tube a b being fitted 
 to the cork of the generating flask, so that, when 
 in place, it may reach the bottom of that vessel, is 
 then ready to receive the acid through the funnel. 
 The gas disengaged flows out through a b and its 
 continuation f g o, thence it may be led into any 
 course by a tube connecting with o, by a flexible 
 india-rubber attachment. 
 
 The perforations in the cork must be only large 
 enough for the transit of the tubes, and the joints 
 must be perfectly tight. To render the cork itself 
 impermeable, sealing-wax should cover both of its 
 surfaces. This arrangement of the tubes obviates 
 all liability of explosion. If condensation takes 
 place in the interior of the generating vessel, the 
 resistance from the funnel-tube being more feeble than tjiat op- 
 posed by the water of the trough or receiving vessel, the air 
 enters. So also, if from any cause the passage of the gas through 
 the exit tube should be obstructed, its pressure upon the liquid 
 in the generator forces it upwards through the funnel-tube, so 
 that it may escape instead of being allowed to accumulate until 
 explosion takes place. 
 
 When it is desirable to have the gas free from impurity, an 
 indispensable consideration if it is to be used in analyses, it 
 should, previous to its entrance, be passed 
 through a small quantity of water, or 
 other fluid, which will dissolve out or 
 chemically attract such foreign matter as 
 might have an injurious effect upon the 
 liquid to be acted upon. A suitable ar- 
 rangement for such purposes, and one 
 well adapted to the generation of sulphu- 
 retted hydrogen gas, is shown in Fig. 
 277 ; A is the bottle containing the proto- 
 
 Fig. 277. 
 
344 
 
 DISTILLATION OF GASES. 
 
 sulphuret of iron, water, and sulphuric acid, and provided with 
 funnel and disengagement-tubes as usual, the latter plunging in 
 the water of a smaller bottle B, from which a disengagement-tube 
 D, nearly as high as that of the bottle A, issues, so as to lead the gas 
 disengaged into a beaker or other vessel containing the liquor to 
 be operated upon ; but the first disengagement-tube c is in two 
 pieces, united by india-rubber, and the bottles A, B, are connected 
 together by a strong band of sulphurized india-rubber j or of gutta- 
 percha G, so that the two bottles may be lifted at once as if they 
 were in one, wedges of cork E E being forced between the two 
 
 Fig. 278. 
 
 bottles, so as to keep the strip of india-rubber G and the tube c 
 properly adjusted. Fig. 278 exhibits the apparatus with stiff 
 tubes, and a short vial, as the intermediate vessel. 
 
 Fig. 279. 
 
 When heat is required to cause or to promote the elimination 
 of a gas, the generating vessels may be either tubes, flasks, or 
 retorts. 
 
 The facility with which glass tubes may be fashioned over the 
 
TEST-TUBE. 
 
 345 
 
 blowpipe flame into any desired shape, renders them particu- 
 larly applicable to small operations. Fig. 279 exhibits a tube- 
 apparatus for the distillation of hydrobromic acid. It consists of 
 a glass tube A B, to which is adapted a disengagement-tube con- 
 veying the gas under the bell c, filled with mercury. The bromine 
 is placed at A, and at B are small particles of moist phosphorus 
 intermixed with bruised glass. Gentle heat being applied at A, 
 the vaporized bromine reacts upon the phosphorus and water, 
 producing phosphorous acid, and disengaging hydrobromic acid 
 gas, which passes over into the bell-receiver and displaces the 
 mercury. 
 
 A test-tube, Fig. 280, fitted with a bent tube, serves very con- 
 Fig. 280. 
 
 Fig. 281. 
 
 veniently for generating small quantities of gas for analytic or 
 even experimental purposes. Any other forms that may be 
 needed will be suggested by the requirements of the process or 
 the ingenuity of the operator, and can readily be fashioned after 
 the instructions given upon GLASSBLOWING. 
 
 Another very convenient form of tube generator is that known 
 as Marsh's Arsenic Apparatus, Fig. 281. It consists 
 of an elbowed tube of Bohemian glass, fitted with a 
 stop-cock and jet, the whole to be supported by a 
 suitable stand or pedestal. The length of the tube 
 may be sixteen inches, and its width three-fourths of 
 an inch. 
 
 The elbow being charged with some pieces of puri- 
 fied zinc, the liquid containing the suspected com- 
 pound is acidulated with oil of vitriol, and poured 
 into the long leg. The arsenical combination becomes decom- 
 posed by the nascent hydrogen generated by the action of the 
 sulphuric acid upon the zinc and water, and makes its exit through 
 
34(5 
 
 FLORENCE FLASK. 
 
 Fig. 282. 
 
 the cock at the short arm, as arseniuretted hydrogen, which may 
 be recognized, when ignited, by its bluish-white flame, and the 
 appearance of the deposit upon a porcelain plate held over it. 
 The stop-cock allows the facility of regulating or stopping off the 
 supply of gas when required. 
 
 Next to the tubes, a Florence flask is the most economical 
 
 vessel for conducting small opera- 
 tions. Fig. 282 exhibits one under- 
 going the process of being heated by 
 a small spirit-lamp. The tripod 
 upon which the flask rests, is sur- 
 rounded by a tin plate screen of a 
 foot in height, to confine the heat of 
 the lamp. The exit tube conveys 
 the gas into the beaker glass c, 
 which contains the solution to be 
 saturated. Flasks of very thin glass, 
 and made uniform throughout, are 
 blown expressly for this purpose. The exit tube is bent so 
 that it may be used with bell glasses over a pneumatic trough, as 
 in Fig. 279. 
 
 Retorts are only convenient when large quantities of material 
 are to be operated upon. For those processes which require high 
 furnace temperatures a metallic retort is needed. Fig. 282 ex- 
 Fig. 283. 
 
 hibits one of iron, and another form has already been presented 
 at Fig. 256. It is fitted with a very convenient coupling or 
 
KEMP'S GENERATING JAR. 
 
 347 
 
 gallows screw, by which the neck may be connected with flexible 
 lead or other exit pipes. The accompanying circular plate, in 
 two pieces, serves both as a cover to the furnace and as a support 
 for the neck of the retort to retain it in place. 
 
 The requirements of the laboratory are such, in respect to sul- 
 phuretted hydrogen and pure hydrogen gases, as to render neces- 
 sary some convenient means for obtaining a constant supply of 
 them, at any and all times, without the trouble and delay of ar- 
 ranging an apparatus in every instance. To this end several 
 apparatus have been contrived, and we have already described 
 one at p. 343. Another, known as Kemp's Generating Jar, is 
 shown by Fig. 284. It consists, simply, of a tall glass jar A, 
 
 Fig. 284. 
 
 with a lateral tubulure near the top. Surmounting the top is a 
 glass plate cover, bored in the centre, and ground on the under 
 surface so as to form a close joint with the ledge of the jar. 
 Through the centre hole passes a copper wire, to the end of 
 which is suspended an earthenware basin or basket D. This 
 wire is held in position by a cork tightly adjusted in the centre 
 hole. The basket is the recipient of the zinc, sulphuret of iron, 
 or other solid matter, to be used for generating the gas. E is a 
 tube fitted to the lateral tubulure, and containing water for wash- 
 ing the gas in its transit to the delivery-tube F. This latter is 
 connected with the former by means of a flexible caoutchouc tube. 
 
348 
 
 HYDROGEN GAS APPARATUS. 
 
 The jar is kept filled with acid liquor to the height shown by the 
 shaded part of the drawing, and when gas is needed, the cullen- 
 dered basin D is to be pushed down into the acid by depressing 
 the wire c, and kept immersed as long as a flow of gas is required. 
 The evolution of gas may be discontinued at will, merely by 
 raising the wire so as to draw the basin out of the liquor. If a 
 rapid generation of gas is desired, it may be fully immersed below 
 the surface, but not too deeply, for the acid liquor is weaker in 
 the lower strata, after it has acted sufficiently long on the solid 
 to convert a portion of it into a dense solution. A partial im- 
 mersion, on the other hand, produces a gentle evolution of gas. 
 Another apparatus, for the same purpose as the foregoing, but 
 on a more extended scale, is that recently devised by Fresenius, 
 for disengaging sulphuretted hydrogen gas, and illustrated by the 
 accompanying drawing. It is always ready for use, at a great 
 
 Fig. 285. 
 
 saving of material, and yet yields, from a single charge, a supply 
 of gas sufficient for a month's service, with the least possible dis- 
 agreeable odor. 
 
 It consists of two lead cylinders # , >, e, d, e, /, g, A, Fig. 285, 
 of equal size, all their joints being soldered with pure lead. Their 
 diameter is 12 inches, and their height 13 inches. Resting upon 
 
HYDROGEN GAS APPARATUS. 349 
 
 leaden feet, about 1J to 2 inches above the bottom, is a per- 
 forated leaden shelf i. An opening k, of about three inches 
 diameter, and closed by a ground glass stopper, serves as the 
 entrance for the sulphuret of iron from which the gas is to be 
 generated. The glass stopper is screwed down with a greased 
 leather washer between the two surfaces. An opening, for run- 
 ning off the residual sulphate of iron liquor, is shown at s. 
 
 " It may be seen in the section, A, that it is placed at a 
 somewhat deeper part of the bottom g, h ; the diameter of this 
 opening is 1^ inches. It is closed by means of a thick, ground, 
 leaden stopper, pressed down upon its mouth by a screw. The 
 arrangement of the filling tube m is sufficiently evident from the 
 drawing, as is likewise that of the tube d, h, which is destined to 
 convey the acid from the upper into the lower vessel, and from 
 this into the former. It will be noticed that it extends into the 
 deepened part of the bottom $r, h, but does not actually touch. 
 The tube c, e, is closed at the top, and, therefore, does not com- 
 municate in any way with the upper vessel. It is intended to 
 convey off the gas disengaged in e, /, g, h, and with that view is 
 furnished with a lateral tube 0, which can be closed by the cock 
 n. The use of the tube p will be seen below. The tube q is 
 closed at both ends, and serves only as a support. These tubes 
 are all of a half inch internal diameter, and should not be too 
 thin in substance. When the apparatus is to be filled it is done 
 in the following manner : about seven and a half pounds of melted 
 sulphuret of iron, in small fragments, are introduced through the 
 opening &, so as to rest upon the perforated shelf i, when k is 
 carefully closed, ?, of course, being likewise closed. 
 
 The cock u is then closed, and a, 6, c, d, filled with dilute sul- 
 phuric acid, by pouring through the funnel first one and one half 
 gallons of water, and then thirty fluid ounces of concentrated 
 sulphuric acid. The air contained in a, b, c, d, escapes mean- 
 while through the tube jt?, even when it is connected with the 
 bottles r, s, t. When now the cock n is opened, as well as one 
 of the cocks u, the acid flows through the tube d, h, into the 
 vessel e,f, g, h. At first air escapes from the tube o, and then 
 sulphuretted hydrogen, as soon as the acid comes in contact with 
 the sulphuret of iron ; after a time all the air is driven out. As 
 seen in B, the tube o is bent and carried along horizontally. 
 
350 COLLECTION OF GASES. 
 
 To it are attached as many ordinary brass cocks M, u, as may be 
 desired. They are connected with washing bottles in the manner 
 represented, by means of a piece of vulcanized caoutchouc tube. 
 When the cock u is opened, as well as the cock n, a stream of 
 gas, of any desired amount, is obtained, which continues per- 
 fectly uniform for days. When the cocks w, U, are closed, the 
 gas disengaged in e, /, g, A, presses the acid upwards through 
 the tube A, d ; and when the sulphuret of iron is no longer im- 
 mersed in the acid the action ceases. This, however, does not 
 take place instantaneously, for there is always some acid left 
 adhering to the sulphuret, and small fragments of the latter fall 
 through the holes of the shelf, and maintain the action for a 
 certain time. Since the gas can no longer escape through 0, it 
 presses the liquid in b d upwards, bubbles up through the acid 
 contained in fl, b, <?, d, and escapes through p. In order to pre- 
 vent this gas from being lost and contaminating the air, the 
 bottles r, s, , are attached ; r contains cotton-wool, which sup- 
 plies the place of water in an ordinary washing bottle, as water 
 would readily run back into the apparatus ; s and t are charged 
 with solution of ammonia in such quantity as to be entirely con- 
 tained by either bottle ; for as the stream of gas is here inter- 
 mittent, the liquid may be forced backwards and forwards from 
 one bottle to the other. A constant supply of sulphuret of am- 
 monia is thus obtained as a by-product. When at last the disen- 
 gagement of gas ceases, the acid has been all consumed, but not 
 the sulphuret, which is equivalent to double the above quantity 
 of acid. It is therefore necessary to run off the solution of sul- 
 phate of iron. This is done in the following manner : All the 
 cocks u are closed, n left open, and a dish placed under Z, which 
 is opened, and then one of the cocks u opened. As soon as the 
 air enters, the liquid runs off rapidly, and when it is all removed, 
 the edges of the opening I are washed with water ; it is again 
 closed, and another quantity of acid added as before. It is not 
 advisable to use stronger acid, for in that case the sulphate of 
 iron would crystallize. The brass cocks do not suffer at all from 
 the sulphuretted hydrogen, and the apparatus answers all reason- 
 able expectations." 
 
 Collection of G-ases. Gases are either collected in the aeri- 
 form state or else in solution. When generated extemporaneously, 
 
COLLECTION OF OASES. 351 
 
 merely as precipitants of some solution, they are passed through 
 the liquid contained in a beaker glass, as at Fig. 282, and Fig. 
 277, a tightly stretched paper cover being in general all that is 
 required to confine the unabsorbed excess in the vessel. 
 
 If a liquid, as well as a gaseous product, is generated simul- 
 taneously, then the arrangement of the apparatus may be as 
 shown in Fig. 286. The use of this may be well illustrated by a 
 
 Fig. 286. 
 
 reference to the manufacture of nitrous oxide gas. The nitrate 
 of ammonia, the material from which it is generated, is placed in 
 the retort, the beak of which is adjusted by means of a perforated 
 cork, to the tubulure of a globular receiver A. This receiver in its 
 turn is connected by bent glass tubes, rendered flexible by a 
 caoutchouc joint, with a Wolffe's bottle B. The latter, deriving 
 its name from that of the inventor, consists of a bottle, the size 
 of which may vary with the extent of the operation, having in 
 this instance three tubulures, each of which is fitted with a per- 
 forated cork for the passage of glass tubes. The first tube 0, 
 Fig. 286, conducts the gas from the receiver, and the central tube 
 acts as a safety valve. The gas cannot escape through it, but 
 should condensation ensue within the bottle, the external air 
 rushes in and prevents the liquid from running over into the 
 recipient or next bottle, if there are two connected, by reason of 
 absorption. The third tube d is the exit tube for conveying the 
 gas directly into the recipient, which in this case is a caoutchouc 
 bag e. 
 
 The retort, receiver, and Wolffe's bottle having been connected 
 
352 COLLECTION OF GASES. 
 
 together, and the joints hermetically closed, heat is then gradu- 
 ally applied by means of the spirit Argand lamp. The eliminated 
 gas passes over into the receiver, there deposits the aqueous 
 vapor with which it is involved, and continues on to the Wolffe's 
 bottle containing water, in its transit through which it parts with 
 the rest of its aqueous vapor, and its other impurities, and ulti- 
 mately reaches the exit tube d. If the gas is to be received into 
 caoutchouc bags, Figs. 171, 286, and pages 252, 351, for inha- 
 lation or other purposes, the connection may be made directly, 
 as seen in the figure, by means of a gallows screw, which allows 
 an empty bag to replace another, as may be necessary. If the 
 bags are intended as reservoirs for the preservation of the gas, 
 their necks are fitted with gallows screw stop-cocks and connect- 
 ing nipples. 
 
 If the gas is to be conducted into a Pepy's gasometer, as at 
 Fig. 301, or under a bell-glass over a pneumatic trough, as at 
 Fig. 294, then instead of the stop-cock there must be a flexible 
 bent tube, of shape similar to that attached to the Fig. 271, 
 adapted to the third tubulure of the bottles. 
 
 Lead pipe of a small bore may be used as a conduit when the 
 generated gas is not corrosive, but india-rubber tube is prefer- 
 able. The gallows screw then becomes the proper mode of con- 
 nection. 
 
 To favor the condensation of the aqueous impurity of the gas, 
 the globular receiver should be kept cool during the distillation. 
 'So also the Wolfie's bottle must be surrounded by water, or a 
 cooling mixture, when the gas is very volatile, otherwise the 
 elevation of temperature, which generally occurs, may cause its 
 dissipation. 
 
 When two or more gases are generated simultaneously, they 
 may be separated by the presence in the receiver of an appropri- 
 ate liquid, which is a solvent of one, but not of the other of them. 
 Thus oxygen may be freed from carbonic acid by passing the 
 mixture through a solution of caustic potassa, which absorbing 
 the acid becomes carbonated, and allows the transit of the puri- 
 fied oxygen. This mode is adapted for this and other purposes 
 in organic analysis, the requisite apparatus being a five-bulbed 
 white glass receiver of the form shown by Figs. 287, 288. Its ar- 
 rangement for the purpose is given in Fig. 139, a being the com- 
 
COLLECTION OF GASES. 353 
 
 bustion-tube, in which the substance to be analyzed is introduced 
 after its mixture with oxide of copper or chromate of lead, from 
 
 Fi *- 287 - Fig. 288. 
 
 which it obtains the oxygen necessary for its combustion. The 
 figure represents the tube in its position, during the analysis, in 
 the trough-shaped furnace of sheet-iron, in which it is heated by 
 being surrounded with ignited charcoal. By means of a per- 
 forated cork, the combustion-tube is connected with the tube in 
 which the water produced by the combustion is condensed. It is 
 filled with chloride of calcium, in order to absorb all the vapors 
 from the carbonic acid, which passes through it into the appa- 
 ratus m r p, through which it would be forced, were it not 
 absorbed by the solution of caustic potassa contained in the lower 
 bulbs. After the completion of the combustion, the carbonic 
 acid which remains in the combustion-tube is extracted from it, 
 by breaking off its pointed extremity and applying suction to the 
 other end of the potassa apparatus at p, by which air is drawn 
 through the whole apparatus, and the carbonic acid absorbed by 
 its passage through the solution in the potassa bulbs. The weight 
 of the water and the carbonic acid, is obtained by weighing the 
 chloride of calcium tube and the potassa apparatus before and 
 after the combustion. For this purpose, each may be conve- 
 niently suspended to the supplementary pan, Fig. 76, of the 
 analytic balance, p. 112. 
 
 Another form of receiver, for similar operations to the pre- 
 ceding, is shown by the annexed drawing. 
 
 23 
 
354 
 
 GENERATION AND ABSORPTION OF GASES. 
 
 These two operations illustrate the generation of gases by 
 destructive distillation ; but the receivers which are used in them, 
 are equally applicable for the collection of gases generated in 
 
 Fig. 289. 
 
 the cold ; the object of the bulbs being to present a larger extent 
 of liquid surface to the gas. Fig. 288 illustrates the manner in 
 which these bulb-receivers may be filled with absorbent liquor 
 without inconvenience to the operator. The lower end being 
 placed in the liquid, and the upper connected by a cork to a bent 
 tube, suction is then applied to the latter by the mouth until suf- 
 ficient liquid is drawn in, after which the suction-tube is discon- 
 nected. 
 
 In the instance we have been referring to, the Wolffe's bottle 
 is used for the purpose of retaining watery vapor or other impu- 
 rities in its contained fluid. Its most common employment, 
 however, is when the gas itself is intended to be preserved in 
 solution in water or other fluid. For this purpose, the number 
 of Wolffe's bottles is often increased to three or more, which are 
 connected together by tubes with flexible joints. In this manner, 
 any gas that has remained unabsorbed by the liquid in the first 
 bottle, is successively exposed to the dissolving influence of that 
 in the others, until it becomes entirely liquefied. The Wolffe's 
 bottles, the form of which is sufficiently explained by the drawing, 
 may, in many cases, be well replaced by wide-mouthed jars or 
 bottles, with two or three perforations in their corks, and which 
 may be made to answer all the purposes of the more expensive 
 apparatus. 
 
GENERATION AND ABSORPTION OF GASES. 355 
 
 Fig. 290 represents an apparatus for the generation and ab- 
 sorption of gas ; a being the heating vessel, the contents of which 
 
 Fig. 290. 
 
 should fill only half its capacity, so that they may not, upon too 
 sudden reaction, run over into the recipient; b the recipient, either 
 for the condensation of aqueous vapor, or the abstraction of 
 impurity by a contained liquid, and the three Wolffe's bottles, 
 half filled with water, the receptacles of the eliminated gas. As 
 the volume of the liquid in the Wolffe's bottles increases propor- 
 tionably to the amount of gas received and dissolved, they should 
 not be more than half filled at the commencement. So also the 
 intermediate receiver should have but a very shallow depth of 
 liquid, else it will take up gas as well as the impurities, and thus 
 cause a loss. The water in the first bottle is the first to become 
 saturated, and all the gas which is not absorbed passes over into 
 the second and third bottles, through the delivery-tubes and tran- 
 sit-tubes 5, a. This arrangement is that usually adapted for the 
 distillation of acid, ammoniacal, and other gases, which are con- 
 densed by solution. 
 
 The tubes must be adjusted to the tubulures by corks (see 
 Chap. XXXI), in such an exact manner as to form an air-tight 
 joint ; and the connections of the glass tubes should be flexible, 
 and formed of india-rubber tube. The tubes c passing down 
 through the centre of the corks and ending at d, just below the 
 
356 
 
 ABSORPTION OF GAS. 
 
 level of the liquid in the bottles, serve for admission of air, when 
 from any cause the internal pressure may become diminished, and 
 are thus a safeguard against the liquid running back by the force 
 of external atmospheric pressure, from the last bottle to the third, 
 second, first, and even to the flask. This diminution of external 
 pressure sometimes proceeds from a prompt absorption of the 
 gas, a sudden stoppage in the delivery of it, or a depression of 
 the temperature in the generating flask. 
 
 When necessary, any other liquid may be made to replace the 
 water in the bottles. For example, aqua ammonise when it is 
 desired to make a chloride or carbonate of that base, and lime 
 milk for the solution of chlorine, &c. &c. 
 
 The inconvenience and delay in arranging a series of Wolffe's 
 bottles for distillation, from the trouble of nicely adjusting the 
 tubes and corks to the tubulures, induced Letorel to suggest 
 a more expedient substitute, which is particularly serviceable in 
 those operations which would be destructive of the cork-fittings 
 of the Wolffe's apparatus. The connections are formed by water- 
 joints, and the apparatus, comprising three glass cylinders, is re- 
 presented, in vertical sections, by the three diagrams following : 
 
 Fig. 291. 
 
 Fig. 292. 
 
 " The outer and inner cylinders A, B, have, severally, three 
 grooves perpendicular to their base, and at corresponding points 
 of their circumference, but in opposite directions. The inter- 
 mediate cylinder c is plain, and is inserted within A over B. The 
 liquid used to shut off communication with the exterior air is 
 placed in the outer cylinder, and the liquid to be brought in con- 
 
ABSORPTION OF GAS. 
 
 357 
 
 tact with the gas is placed in the inner vessel. The gas is con- 
 ducted into B by the bent tube E, and the unabsorbed portion 
 escapes by the tube F. Both these tubes fit in the pairs of oppo- 
 site grooves. The third pair of grooves is for a safety-tube, Fig. 
 
 Fig. 294. 
 
 293, if requisite. The mode of connecting a series of these ves- 
 sels will be sufficiently evident from the wood-cut. This arrange- 
 ment may likewise be employed for generating gases, as shown in 
 
 Fig. 295. 
 
 Figs 294 and 295. The liquid used for the hydraulic joint must 
 be adapted to the nature of the operation. In the preparation of 
 
358 WOLFFE'S BOTTLES. 
 
 carbonic acid or the bicarbonates, water will answer. For other 
 purposes, mercury, solutions of chloride of calcium, of caustic 
 alkali, &c., may be used. The cylinder c must be loaded with a 
 sheet of lead in order to keep it steady." 
 
 For micro-distillations, the Wolffe's bottle may consist of a 
 U-shaped tube, bent as seen in Fig. 296. These condensers can be 
 formed into a series by means of corks and bent tubes, as shown 
 
 Fig. 296. Fig. 297. 
 
 by Fig. 297. They are very convenient for minute experiment, 
 and admit of the use of either liquid or solids, as agents for ab- 
 sorbing gases. The condensing material occupies the bend B, c, 
 D, if liquid, as indicated by the shaded portion. In the use of a 
 solid absorbent, it should nearly fill both legs of the tube. Very 
 small and little bottlings, with two and three tubulures, are also 
 used for delicate operations. 
 
 When the gas is to be generated by reaction of liquid upon a 
 solid, the latter must be put into the flask before the stopper and 
 tube are adjusted. The liquid can then be added through the s 
 tube, as often as it is required to continue the disengagement. If 
 the gas is heavier than the solvent liquid, the disengagement-tube 
 need dip but slightly beneath its level ; and vice versd. 
 
 There are several points to be remembered in the generation 
 and collection of gases. 
 
 1. All gases owe their existence as such to a certain elasticity, 
 by reason of which they press upon the sides of the vessels in 
 which they are enclosed. 
 
 2. The tension or elastic force of a gas is proportional to its 
 quantity : it augments with the temperature, and decreases by 
 refrigeration. 
 
 3. The atmosphere weighs upon all bodies, its pressure being 
 

 SAFETY-TUBES. 
 
 359 
 
 Fig. 298. 
 
 usually equal to the weight of a column of water 34 feet high, or 
 of a column of mercury 30 inches. 
 
 4. That liquids (in equilibrium) press equally in all directions. 
 
 These facts, therefore, render necessary the use of the safety- 
 tubes <?, c, c, Fig. 290, and Welters tube, Figs. 298, 299. 
 
 Safety Tubes. When, in the course of distillation, a momen- 
 tary suspension of the heat or generat- 
 ing impulse causes a partial vacuum in 
 the heating vessel, the liquid into which 
 the disengagement-tube dips is forced 
 by the pressure of the atmosphere into 
 its bore, and ultimately into the vessel 
 itself. 
 
 This entrance of liquid into the 
 generating vessel may result also from 
 its sudden cooling, by the entrance of 
 cold water, or by other means. 
 
 The results of this absorption are 
 sometimes the fracture of the vessel, 
 
 and more frequently irreparable injury to its contents. To 
 obviate these inconveniences, we use a safety-tube, the usual 
 forms of which are shown by Figs. 250, 298, 299. The first, 
 which is called an s tube from its similarity to that 
 letter, is most used, but either of them may be em- 
 ployed in the following manner. If the generating 
 vessel has only one aperture, its cork, having been 
 tightly fitted and rendered impermeable by coatings 
 of sealing-wax or other cement on its upper and 
 lower sides, is then to be perforated with two holes, 
 one for the transit of the s tube, and the other for 
 that of the exit tube. The tubes being tightly ad- 
 justed in the holes, as shown in Fig. 298, and the cork 
 fitted to the mouth of the generating flask, a quantity 
 of water or sometimes of other liquids, as mercury, is 
 poured into the s tube. When, during the process, 
 the level is stationary in the bulb B, and in the part A of the tube, 
 the apparatus is hermetically closed. If, however, a condensa- 
 tion of vapor takes place in the interior of the flask, the external 
 pressure of the atmosphere weighs alike upon the liquid F of the 
 
 Fie. 299. 
 

 360 GASOMETERS. 
 
 trough, and that in the s tube ; but as the latter offers the least 
 resistance, the air first makes its contained fluid advance towards 
 the flask, and then enters in bubbles into it, thus preventing the 
 absorption of liquid from the trough or receiver. 
 
 If mercury is used, its relative density to water must be re- 
 membered, and the column of metal in the curve should be as 
 low as possible. As a column of mercury requires one of water 
 nearly fourteen times its height for its support, it follows that if 
 the former is too high, the gas passes back more rapidly into the 
 recipient during condensation from the disengagement-tube than 
 the air traverses the metallic mass in the s tube. Mercury is 
 used when the Wolffe's series comprises a number of bottles ; so 
 that the opposing force of the contained liquid may not be suffi- 
 cient to cause the disengagement of the gas through the s instead 
 of the exit tube. When operating with a mercurial trough, the 
 s tube, Fig. 299, without a bulb, is used. The quantity of metal 
 which it should receive must, however, be such that the pressure 
 of the gas will meet with as strong a resistance from it as the 
 liquid in the trough. When flasks are replaced by retorts, the 
 latter should be tubulated, so that the safety-tube may be adapted 
 to its tubulure by means of a perforated cork. 
 
 If the retorts are necessarily plain, as in certain distillations by 
 furnace heats, then the safety-tube can be attached to the dis- 
 engagement-tube E, Fig. 307, over the blowpipe flame. The 
 liquid is introduced at H i. This kind of tube, known as Welter's, 
 is very fragile, and requires careful management and handling. 
 
 Gasometers. When the eliminated gas is to be preserved free 
 from air, in large quantities, for laboratory purposes or transpor- 
 
 is. 300. 
 
 tation, it is received in gasometers. Gas bags, made of caoutchouc, 
 are very convenient for storing gas for use, and have already 
 
PEPY'S GASOMETER. 
 
 361 
 
 been mentioned at p. 251. The annexed drawing presents the 
 apparatus separately. It is placed between two hinged boards, 
 with a hole in the centre of the joint for the passage of the neck 
 of the bag and its cock, by which it is coupled with the gene- 
 rating apparatus, as seen at Fig. 171. The upper board is fitted 
 with a groove for the reception of a heavy iron upright, which 
 constitutes the pressure by which gas is drawn from the bag as 
 may be wanted. 
 
 Pepy's Gasometer. The most convenient gas-holder is that 
 known as Pepy's, Fig. 301. It consists of a japanned zinc hollow 
 
 Fig. 301. 
 
 
 i ! 
 ^ 1 1 
 
 
 
 ii 
 
 
 h 
 
 1 1 
 ii 
 a MI 
 
 
 
 ll 
 II 
 II 
 
 
 
 ii 
 
 ^ 
 
 L 
 
 V Y \ 
 
 cylinder 16 by 12 inches, surmounted by a trough b of 9 by 12 
 inches, making the total height of the apparatus, including that 
 of the supports, three feet. Near the base of the cylinder is a 
 lateral gulley, placed obliquely, and cut with a thread to receive a 
 screw plug, which closes it hermetically. 
 
 The tube d, supporting the centres of the vessels, and fitted 
 with a cock, allows a communication between the reservoir and 
 trough. A second tube * c i, at the side, also fitted with a cock, 
 passes from the upper cylinder into the lower, and descends, as 
 shown by the dotted lines, to within a few lines of the' bottom. 
 The stem e is merely a support, and serves no other purposes. 
 The coupling and stop-cock in the side near the top serve for 
 connection with a jet, or for fitting on a bag or bladder. The 
 
362 PEPY'S GASOMETER. 
 
 glass gauge Jc, graduated into cubic inches, is adjusted firmly and 
 hermetically by means of sockets at the top and bottom of the 
 cylinder, and serves to indicate the level of the internal water. 
 To prevent fracture, it is embedded in a framework of the same 
 metal as the gas-holder. 
 
 The manner of using the apparatus is as follows : close the 
 mouth #, and fill the reservoir with water. For this purpose the 
 water is poured into the trough 5, and allowed to run down 
 through the opened tubes d and c. The cock / being also opened, 
 the confined air escapes as the water enters, and in proportion 
 as the reservoir a is filled, the water rises in the tube k, and 
 hence the latter will indicate when it is full. As soon as this 
 occurs, and water runs through the pipe /, the cock of the latter 
 must be closed, and the residual air allowed to escape through 
 the still open tube d. If, upon gently shaking the vessel, no 
 more bubbles appear, then all the cocks are to be closed, and the 
 apparatus mounted over a tub, of diameter some six inches or 
 more greater than that of the gasometer, and the gullet g is then 
 opened. As the highest part of the edge of the inner aperture 
 of this gullet is lower than the lowest part of the edge of the 
 outer aperture, by a half inch or more, the water cannot escape, 
 unless the air simultaneously finds access, inwards, from above, 
 by leak-holes or otherwise. If, after the gush of a small portion 
 when the plug is first removed, there should be any further 
 leakage, it will be indicated by the gauge-tube. 
 
 All being tight, the beak of the retort, or end of the conduit- 
 tube of the generating vessel, is introduced into the gullet, as 
 shown at A, Fig. 302. The eliminating gas entering the receiver, 
 displaces the water, which escapes at #, and falls into the pail 
 beneath. As soon as the vessel is full, which will be known by 
 the examination of the gauge, or when a sufficient quantity has 
 been collected, the disengaging-tube or beak is withdrawn, and 
 the gullet closed with the plug. 
 
 If it is desired to fill a gas-bag from the reservoir, it must be 
 fitted with an appropriate cock and nipple for connecting with 
 the coupling cock /, and the pressure of the water with which the 
 trough b has been partially filled, should be made to act upon 
 the gas by opening the cock c. So also when the gas is to be 
 transvased into bell-glasses, these latter are filled with water to 
 
MERCURIAL GASOMETER. 363 
 
 displace all air, inverted, and then brought directly over the 
 opened tube d, as shown in Fig. 302. As the water enters from 
 the trough through the tube <?, gas escapes into the jar by the 
 exit pipe d. When the vessel is filled, communication must be 
 shut off by closing the cocks. 
 
 When a greater pressure is required than can be given by 
 the water contained in the trough, it 
 can be obtained by means of a long- Fig. 303. 
 
 barrelled funnel 0, Fig. 304. When 
 this is screwed by its threaded nipple p, 
 into the socket s, Fig. 302, and filled 
 with water, there is a pressure of nearly 
 six feet. By abridging the length of 
 
 the barrel to q, the pressure is diminished to a little less than 
 four feet. When two of these gasometers, filled the one with 
 oxygen and the other with hydrogen, are united by means of a 
 double jet, Fig. 303, connected by its branches a b with the cocks 
 f of the reservoir, they form what is called the hydro-oxygen or 
 COMPOUND BLOWPIPE described at p. 170. 
 
 Mercurial Gasometer. When the eliminated gas is soluble in 
 water, or altered by contact with that liquid, it may with pro- 
 priety be collected over mercury. For this purpose Pepy has 
 contrived the arrangement shown in Fig. 305, which obviates the 
 expense and inconvenience of filling the cistern with mercury. 
 It is made of iron, and consists of a bell A A B B, which has a 
 cock c at its summit, and which is immersed in a cylindrical iron 
 cistern M N o p. This cistern is the reservoir for the mercury, 
 but in order that as little as possible may be used, an iron core 
 D E occupies its centre, and allows an interval between it and the 
 sides of the cistern only sufficient for the jar and mercury to 
 make it tight. A glass tube a b cemented tightly to the top of 
 this inner cylinder, traverses it and serves as a conduit of the 
 gas into the bell, which is maintained in a vertical position by a 
 movable elbow adjusted to the frame of the apparatus. 
 
 A cock c is adjusted to the tube a b, and puts it in communi- 
 cation with the eprouvette or small inverted bell F, placed upon 
 a dish containing mercury. 
 
 In using this gasometer, the cavity M N P is filled with 
 mercury, the cocks c and c are opened, and after the bell has 
 
364 
 
 MERCURIAL GASOMETER. 
 
 been pressed down to its full extent in the metal, the cock c is 
 closed. 
 
 The disengagement-tube is then introduced under the mouth 
 of the eprouvette, and the generation of the gas proceeded with. 
 
 Fig. 304. 
 3. 
 
 Fig. 305. 
 
 Each bubble as it enters the bell elevates it proportionately ; and 
 when it has received a quantity equivalent to the volume of the 
 capacity of the tube and of the eprouvette, the cock c is to be 
 opened again and the bell depressed. The greater part of the 
 gas which has entered, and the air with which it is mixed, is thus 
 forced to escape. A repetition of this manoeuvre two or three 
 times will insure the entire expulsion of the air ; when the por- 
 tions of gas given off can be collected and preserved for use. 
 When the bell is full, the cock c is to be closed and the retort J 
 removed. 
 
 To transvase any portion of the gas that may be wanted for 
 use, it is only necessary to put the tubulure c in communication 
 with the vessel in which it is to be received, by opening the cock, 
 and then to depress the bell in the mercury. 
 
PNEUMATIC TROUGHS. 
 
 365 
 
 Fig. 306. 
 
 A scale graduated upon the side of the bell will allow an esti- 
 mation of the volume expended. 
 
 Devilles Gasometer. Thia apparatus, constructed upon the 
 same principle as Harriot's vase, is most used in organic analysis. 
 Fig. 306 exhibits the arrangement. A A is a tubulated bottle 
 filled with water ; and a a a is 
 the tube for disengaging the 
 gas from the generator. Each 
 bubble of gas displaces an equal 
 volume of water, which is con- 
 ducted off by means of the 
 syphon b b b, and the process 
 should be continued until the 
 expulsion of all the water, save 
 just enough to fully close the 
 orifices of the tube. 
 
 When the gas is to be dis- 
 engaged for use, fill the funnel 
 E with water, and open the cock 
 f. The pressure of the water 
 descending into the flask forces 
 the gas into the tube i i. 
 
 A flexible tube H I can then 
 
 be adapted to the orifice of the vessel into which the gas is to be 
 introduced. 
 
 This gasometer is especially employed for holding oxygen to 
 be passed over oxide of copper in tubes, after organic analysis ; 
 and to remove all carbonic acid that it may contain, it is passed 
 through a flask containing an aqueous solution of caustic potassa. 
 
 The small bottle c contains the concentrated sulphuric acid, 
 and the tube u potassa in one branch, and chloride of calcium in 
 the other. 
 
 If the oxygen is kept in this holder for too long a time, it 
 becomes altered and contaminated with atmospheric air. 
 
 PNEUMATIC TROUGHS. In most manipulations with gases, 
 particularly when they are required for immediate use or for 
 temporary purposes, they are collected over the pneumatic 
 trough. As the bell glasses into which they are to be received 
 must first be freed from contained air, it is necessary to immerse 
 
WATER TROUGH. 
 
 them in an appropriate liquid. Water and mercury are the two 
 fluids almost universally employed, the first being used for all 
 those gases which are not soluble in it, and for some which are 
 only so in a slight degree, and the latter for those which are 
 absorbed by water, and which exert no chemical action upon the 
 mercury. Hence the distinctive terms, water and mercurial 
 trough. 
 
 Water Trough. A wooden pail, square or oval, with a little 
 management, can be converted into a most convenient water 
 
 trough, G, Fig. 307. It should be of capacity sufficient to allow the 
 thorough immersion of bells of any size required for experiment. 
 One of a foot in depth, sixteen inches in length, and ten inches 
 in width, will be very suitable, a vessel G of this size fulfilling 
 almost all the requirements of an experimental laboratory. Near 
 to the top, in the interior, should be lateral flanges for the sup- 
 port of a sliding shelf a. This sliding shelf should have sufficient 
 surface for the support of several bells or jars, F, at a time, and 
 may extend over half of the trough. It is perforated with holes 
 for the reception of the beak of the disengaging 
 vessel, as seen at 5, Fig. 306. 
 
 A very convenient water-bath for the collec- 
 tion of gases may be formed of a deep earthen- 
 ware dish, or other vessel in common use, by the 
 addition of the bee-hive shelf, Fig. 308. This 
 shelf, generally made of porcelain, is a substitute for the shelf of 
 a regular trough, and serves for the support of the bell glasses or 
 
 Fig. 308. 
 
BELL GLASSES GAS JARS. 367 
 
 other receivers. It may be two inches in diameter and one inch 
 high, for a dish one foot wide and two inches deep, and propor- 
 tionally larger for one of greater dimensions. The disengage- 
 ment-tube enters the semicircular opening at the base, and 
 delivers the gas into the receiver by its curved end protruding 
 through the hole in the centre. Part of a loaded wooden box, 
 a metallic support, or other extemporaneous arrangement, may, 
 in many cases, be so adjusted to take the place of the common, 
 or the bee-hive shelf, and to answer every useful purpose. 
 
 It is indispensable that the trough should be made thoroughly 
 water-tight, and should be well hooped. For further protection, 
 it might be covered over with several coats of paint. Leakage 
 being thus provided against, the vessel may be used upon either 
 the operating or centre table. The stop-cock near the bottom 
 allows the exit of the water when it has become dirty, acidified,- 
 or otherwise unfit for use. 
 
 The level of the contained water must always be half an inch 
 or more above the top of the shelf. When the bell is to be 
 charged, it is first completely immersed in the water, so as to 
 expel all contained air, then taken up by the knob, raised to a 
 vertical position, and carefully slid along with its mouth in the 
 water to the shelf, and placed immediately over the hole through 
 which the disengagement-tube enters. As the gas bubbles up 
 into the bell, the water is displaced, and when it is filled, it can, 
 if necessary, be drawn aside and replaced by another. So the 
 process is continued until all the gas generated has been col- 
 lected in bells. 
 
 As the first bubbles of gas eliminated are contaminated with 
 air, they should be rejected ; consequently the beak of the dis- 
 engagement-tube ought not to be brought under the bell receiver 
 until the gas commences to pass over freely. 
 
 Bell Glasses G-as Jars or Eeceivers.The arrangement of an 
 experimental laboratory is incomplete without a series of bell 
 glasses, varying in size from a gill upwards to one gallon. They 
 should be of glass, preferably of white glass free from lead, and 
 made so as to combine strength and neatness, and should have 
 a knob at the summit for convenience of handling. The rim 
 of the mouth must be ground perfectly smooth and level, so 
 that when resting upon an unground glass disk or an even-hot- 
 
368 
 
 BELL GLASSES GAS JARS. 
 
 tomed plate, the joint may be tight. Fig. 309 exhibits a plain 
 jar for ordinary uses ; and Fig. 310 a similar implement tubu- 
 
 Fis. 309. 
 
 Fig. 310. 
 
 Fiz. 311. 
 
 lated at its summit, and closed with a glass stopper. This open- 
 ing not only allows the facility of forming connections with other 
 apparatus, but also that of filling it readily with liquid merely by 
 depressing it, while unstopped, vertically in the water trough. 
 The air escapes through the tubulure in proportion to the rise of 
 fluid in the receiver, which when full is to be stoppered and placed 
 upon the shelf to receive the gas. Sometimes the tubulures are 
 fitted with stop-cocks, as seen at Fig. 311, which 'add to the con- 
 venience of the jars in many operations, and particularly when it 
 is desired to pass a measured quantity of gas from the receiver 
 
 Fig. 312. 
 
 Fig. 313. 
 
 into another vessel attached as heretofore described at p. 147. 
 For this purpose the bell must also be graduated as seen in Fig. 
 312. Fig. 313 presents a graduated bell-tube. 
 
THE MERCURY TROUGH. 369 
 
 If the vessel into which the gas is to be received is a bladder 
 instead of a glass bell, it must be fitted with a coupling cock, 
 freed from air as much as possible by compression with the hands, 
 then connected with air-pump or syringe, and completely exhausted 
 by suction. The cock is then closed, the bladder detached from 
 the syringe, and adapted by its coupling to the cock of the bell. 
 Communication being opened, the gas passes into the bladder 
 Upon the depression of the jar. 
 
 By grinding the surface of the ledge very accurately, and fit- 
 ting the mouth of the bell with a ground glass disk, which, by 
 the intervention of a little grease, may form an air-tight joint, 
 gases may be retained unaltered for a limited period. The 
 syringe, Fig. 47, is made so that it may be used both vertically 
 and horizontally. 
 
 The Mercury Trough. The high cost of mercury renders 
 necessary an economical construc- 
 tion of the trough in which it is Fig - 314 ' 
 
 kept. Fig. 314 exhibits one of 
 convenient form. It consists of 
 a well-japanned cast-iron trough, 
 twelve inches long, seven inches 
 wide, and two inches deep. The 
 bottom, towards the side, is sunk 
 throughout its length into a well 
 two inches wide and one and three- 
 quarter inches deep, and is ex- 
 panded at its end into a circular 
 cavity. This cavity allows of the 
 immersion of the tubes or bells in 
 
 a moderate depth of mercury without the expense of filling the 
 whole trough being incurred ; and the circular end being larger 
 than the other portion of the canal, allows the use of receivers of 
 from two to three inches in diameter. 
 
 When this cavity is not in use and the mercury required to fill 
 it is needed in the other part of the trough, it is closed with an 
 exactly fitting iron plug which accompanies the vessel for this 
 purpose. 
 
 The trough is placed upon the operating-table, and is manipu- 
 lated with in the same manner as the water trough. For the 
 
 24 
 
370 
 
 THE MERCURY TROUGH. 
 
 convenience of supporting tubes in a vertical position, there is an 
 
 accompanying clamp with 
 sliding rod, which is 
 
 Fig. 3 15. 
 
 at- 
 
 tached to the side. 
 
 The small mercurial 
 trough of porcelain, Figs. 
 315, 317, very useful in or- 
 ganic analysis, contains usu- 
 ally from ten to twelve 
 pounds, and serves also very 
 conveniently for experi- 
 ments upon a small scale. 
 
 Smaller sizes, of about four pounds capacity, are made after the 
 pattern, Fig. 316. 
 
 Fig. 318 exhibits a cylindrical glass trough, 
 which is used with tubes in organic analysis. 
 It is of glass, fifteen and a half inches high, 
 and is widened at the top. The drawing 
 represents the introduction of lye into a graduated tube by means 
 
 Fig. 316: 
 
 Fig. 317. 
 
 Fig. 318. 
 
 Fig. 319. 
 
 of the pipette, Fig. 319, over a column of mercury. The tip of the 
 
THE MERCURY TROUGH. 371 
 
 pipette is curved so as to facilitate its entrance under the mouth 
 of the tube. This plan is adopted sometimes in lieu of that given 
 at p. 353, for the separation of two gases, by presenting to both 
 a third substance for which either of them has an affinity. 
 
 Griffin's trough, which is designed for working with long tubes 
 and the least possible quantity of mercury, has the form of the 
 annexed drawings, the lower one of which presents a sectional 
 view. 
 
 Fi ? . 320. 
 
 It has a permanent bee-hive shelf a a for supporting tubes in 
 the act of being filled with gas, and a space, which allows liquids 
 to be passed in a small tube, through the mercury, to the gas. 
 
 Mercury troughs are generally made of iron, stoneware, or 
 porcelain ; but we prefer them of some hard and very smooth 
 wood. The root of the apple-tree fulfils all the requirements ; 
 and a carver will fashion a neat, durable, and cleanly trough 
 from a single piece. It is, however, advisable to have the upper 
 part of the sides made of thick glass plate, set firmly in grooves 
 by means of cement. This arrangement permits the level of the 
 metal in the tube to be seen at the lowest points. 
 
 In the course of time the mercury of the trough becomes de- 
 based by use, either with water, metals, or suspended matters. 
 The water being specifically lighter, may very readily be removed 
 by spreading sheets of bibulous paper on the surface of the mer- 
 cury, and renewing them as fast as they become saturated. The 
 metals are separable by distillation, the mercury passing over 
 pure into the recipient. 
 
372 TRANSFER OF GASES. 
 
 If the impurities are merely coarse suspended particles, as of 
 metallic oxides, straining, by compression with the hands, through 
 a chamois leather bag, will retain them, and even most amal- 
 gams, while the mercury passes through the pores entirely or 
 almost pure. 
 
 Gases Collected over Air. Although chlorine can, for tempo- 
 rary purposes, be collected over hot water in which it is not 
 dissolved, that body, as well as iodhydric and bromhydric acids, 
 and certain other gases which are soluble in water, or which 
 attack mercury, are sometimes collected in receivers or bottles 
 filled with air. 
 
 If the gas is lighter than air, the end of the disengagement- 
 tube should reach to the upper part of the inverted vessel. As 
 the gas enters, the air is displaced and goes out below, and the 
 jar is known to be full when the gas also escapes. The jar must 
 then be slowly and carefully removed, so that the vacuum left by 
 the withdrawal of the tube, may be completely supplied by the 
 gas simultaneously entering, and its mouth be closed with a plate 
 of ground glass, cork, piece of caoutchouc, or other suitable 
 means. 
 
 When the gas is heavier than air, as is the case with chlorine, 
 the disengagement-tube should enter to the bottom of the re- 
 ceiver, the mouth of which should be closely covered with a paste- 
 board disk. When the gas begins to escape at the mouth, the 
 jar is full, and, after being closed with a ground glass plate or 
 other stopper, carefully removed aside. 
 
 Transfer of Grases. It is frequently necessary to transfer 
 portions of gas from a large vessel to a smaller one for the pur- 
 poses of experiment or MEASUREMENT. 1 Having already given 
 
 1 As the volume of gas confined in tubes, or other vessels, over mercury or 
 water varies according to the pressure of the surrounding atmosphere, it becomes 
 necessary in experiments on gases to observe the barometric pressure, or the height 
 of the mercurial column in the barometer, at the time the volume of the gas is 
 observed. Every laboratory ought, therefore, to be provided with a barometer, 
 which should either be a good syphon-barometer or a cistern-barometer, in which 
 the mercury of the cistern may be brought to the same level before observing the 
 height of the column. The latter is generally read off in a scale divided into 
 inches, tenths, and hundreds of inches. As the height of the mercurial column 
 varies according to the temperature, a correction must be made for the tempera- 
 ture of the mercury in the barometer, which, for this purpose, is furnished with a 
 thermometer to be observed at the same time. 
 
TRANSFER OP GASES. 
 
 373 
 
 the mode of transferring from a gasometer, we will now speak of 
 transvasement over troughs. 
 
 If the jar or reservoir of gas is still upon the shelf of the pneu- 
 matic trough, the smaller vessel, which is to receive a portion of 
 its contents, is to be entirely immersed in the fluid of the trough, 
 and, whilst full, conveyed bottom downwards to the shelf, and 
 there placed so that it will project over the edge of about a third 
 of its diameter. The reservoir is then brought forward, and the 
 mouths of the two put in connection, as shown in Fig. 321, by 
 
 Fig. 321. 
 
 inclining the reservoir so that their edges may be in contact: 
 the gas then passes up in bubbles, and by a little dexterity the 
 rapidity of its flow can be easily regulated. 
 
 At pages 126, 202, and 203, we have already given directions 
 for the transfer of gases into tubes and globular vessels. 
 
 Bladders are filled from the cocked receivers, Fig. 312, aa 
 directed at p. 368. Bladders are cleansed by ablution in weak 
 potash lye, subsequent washings in fresh water and drying. 
 The caoutchouc bags, mentioned at p. 304, are, however, pre- 
 ferable. 
 
 When the filled receiver is to be removed from the trough for 
 further essays with gas, it should be gently slid off the shelf into 
 a flat-bottomed plate containing just enough water or mercury to 
 seal the mouth. 
 
 Distillation ly Steam. Steam is a most convenient as well as 
 efficient means of distillation in a large number of cases. For 
 example, in the distillation of essential oils, and similar volatile 
 
374 DISTILLATION IN VACUO. 
 
 substances, separable from fixed matter by a heat of 212 to 
 230 F. The application of the steam must be direct, and pro- 
 vision for its use in this manner has been made at A in our design 
 of the steam series, Fig. 18. The solid matters rest in the body 
 of the vessel upon a perforated lining or diaphragm, and the 
 steam is led into the interior through a pipe ending in a cullen- 
 der, so as to cause its diffusion throughout the mass. To prevent 
 loss of heat by radiation, the sides of the containing vessel should 
 be wrapped in woollen. As the volatile substance is eliminated 
 from its fixed associates, it becomes involved with the arising 
 steam, and passes over into the condenser, and ultimately into 
 the receiver, where the two form distinct layers according to their 
 differing densities ; and the water, or condensed steam, may be 
 thus separated from the valuable product, as directed at p. 340. 
 
 By passing the steam through hot tubes before its admission 
 into the still or other containing vessel, it may be superheated 
 to a very high degree, and in this state becomes a powerful de- 
 composing agent ; and consequently useful for those distillations 
 in which the required distillate is to be formed from the decom- 
 position of the original matter under process. The matters 
 treated in this way are generally contained in metallic vessels 
 and tubes capable of resisting a certain amount of pressure. The 
 superheated steam is led directly into and through them ; so that 
 the distillate becomes incorporated with the aqueous vapors, and 
 passes out with the latter into the condenser and receiver. 
 
 DISTILLATION IN VACUO. This kind of distillation is resorted 
 to for the production or purification of many volatile matters 
 which are alterable in the air or in aqueous vapor. Retorts 
 drawn out at their beak into a very narrow opening, or glass 
 tubes, fashioned over the blowpipe flame to suit the process, are 
 the vessels commonly employed. After the vessel is charged, 
 heat is applied to the bulb portion, and as soon as it becomes 
 filled with vapor and all air is expelled, the tube should be heated 
 over a lamp. After the annealing of the closed end, it, being 
 intended for the reception of the distillate, should be exposed to 
 the influence of cold while the process is being conducted. If 
 the retort is used, the receiver with which it is connected must 
 be warmed over the sand-bath, and in delicate experiments ex- 
 hausted by means of the syringe, Fig. 99, or air-pump, Fig. 47. 
 
DRY OR DESTRUCTIVE DISTILLATION. 
 
 375 
 
 Fig. 322. 
 
 Dry or Destructive Distillation. This kind of distillation has 
 a more general application to solids than liquids ; but, in either 
 case, the substances under treatment are highly heated, in close 
 vessels, until decomposition en- 
 sues, for the sake of the pro- 
 ducts thus generated. These 
 products are mostly the distil- 
 late, which is either gaseous or 
 liquid, or both simultaneously; 
 but in rare instances, the resi- 
 duum in the retort is the de- 
 sirable matter. The operation 
 is practised for the decomposi- 
 tion of certain kinds of bodies, 
 particularly those of organic 
 nature. The new compounds are formed by an interchange of 
 the ultimate components of the original body under the influence 
 of heat. The process for organic analysis is a veritable destruc- 
 tive distillation, and has already been described at p. 247. The 
 tubes for this and similar experiments being long, require the 
 use of the gas furnace, Fig. 166, for heating them. The product 
 in that case being gaseous, is either absorbed by a suitable liquid, 
 as shown by Fig. 139, or received over mercury, as seen in the 
 annexed drawing. 
 
 Fig. 323. 
 
 When the distillate is both gaseous and liquid at the same time, 
 the generating apparatus must have two receiving vessels con- 
 nected with it, one adapted to the absorption of the gas, and the 
 other for the condensation of the liquid. 
 
 The vessels in which dry distillation is performed are mostly 
 
376 DRY OR DESTRUCTIVE DISTILLATION. 
 
 of iron, and occasionally of porcelain and earthenware ; but, in 
 either case, the covers must be movable for convenience of remov- 
 ing the residuum, which, being very often dry and hard, adheres to 
 the bottom of the retort with great tenacity. Earthenware and 
 porcelain retorts are only used in very exact experiments, for 
 which those of metal are not well adapted. Those of porcelain 
 are expensive and very fragile ; while the earthenware retorts, 
 though much less costly, are only less apt to crack during the 
 heating. The usual form is seen at Fig. 322, which shows the 
 head detached from the body. The two are cemented together 
 by lute, when under process, so as to form a steam-tight joint. 
 
 Iron retorts have already been de- 
 Fig. 324. scribed at p. 332, and another form is 
 now presented in Fig. 324, which shows 
 one with its head fitted to the body by 
 ground joints, and held securely in place 
 by a clamp and screw. 
 
 As examples of the effect of dry distil- 
 lation upon certain substances, citric acid 
 may be converted by it into carbonic acid 
 and oxide, acetone, aconitic acid, and 
 water; fatty bodies modified into new 
 substances ; and resins transformed into 
 oily liquids and gaseous carbohydrogens. 
 In the dry distillation of nitrogenized bodies, the resultant 
 products are complex, and contain nitrogen, ammonia, cyanogen, 
 &c. For instance, indigo yields carbonate and prussiate of am- 
 monia and kyanole. 
 
 In the arts, the dry distillation of wood furnishes charcoal, 
 pyroligneous acid, pyroxylic spirit, creasote and tar; and that of 
 bituminous coal and fat, illuminating gas. 
 
 The employment of close vessels in distillations is becoming 
 very general for certain classes of experiments. They present 
 the great advantage of excluding the air from the interior ; and 
 afford the means of exciting reaction in substances which would 
 otherwise vaporize, and escape under atmospheric pressure. 
 Moreover, the internal pressure thus created, is a condition 
 which favors the action of the heat in augmenting the affinities 
 
HEATING IN CLOSE VESSELS. 377 
 
 of the elements of the substance under process of destructive 
 distillation. 
 
 Berthelot's suggestions (Journ. Pharm. et Chim. XXIII), in 
 regard to the proper mode of managing close vessels, in heating 
 operations, are so full of serviceable instruction, that we annex 
 an abstract. 
 
 For temperatures below 212 F., the containing vessels may- 
 be heated by water-bath, which should be covered to prevent the 
 spattering of the boiling water. For 212 F. to 750 F., the 
 heating medium must be an oil-bath in a close vessel, the neces- 
 sary precautions being observed to prevent explosions by the 
 ignition of the boiling oil or its vapor. To this end the boiler 
 should not be filled to more than .half its depth with oil, and 
 should rest by a flange upon its circumference, and midway from 
 the bottom upon the top of a strong and close chamber, surmount- 
 ing a furnace, the fire-hole of which must have its entrance upon 
 the outside of the apartment. The fire-grate should be about 23 
 inches from the bottom of the boiler. The boiler itself should be 
 about 2J feet in height and slightly conical, and should be enve- 
 loped with a brickwork casing, so as to shut off all communication 
 between it and the fire, except by means of the furnace part. To 
 indicate the temperature of the oil, a long thermometer is ad- 
 justed in a hole in the top. For heating, glass tubes should be 
 confined in iron tubes, closed at one end by hammering, and at 
 the other with a screw plug ; this arrangement prevents the spat- 
 tering of the oil in the event of the glass tube breaking, though 
 in some rare cases, as in the heating of alcohol to 750, the ex- 
 plosion of the glass tube is so violent as even to break the iron 
 envelop, and the inflammable gases thus projected through the 
 heated oil are liable to take fire. When such a contingency is to 
 be apprehended, the iron tube should also be enveloped in a tight 
 sheet-iron muff, for the purpose of confining the inflammable gases 
 in case of accident. The whole is then immersed perpendicularly 
 in the bath, so that its entire length may be covered during the 
 heating. The oil for the bath should be prepared by boiling it in 
 the open air until it has acquired an almost solid consistence 
 when cold. In this state it can be heated to above 680 without 
 sensible ebullition. After having been used continuously for 
 
378 HEATING IN CLOSE VESSELS. 
 
 several days, the oil is then able to bear from 750 to 850 with- 
 out boiling, and will resist decomposition up to a dull red heat. 
 
 Experience is the best guide for the regulation of the tempe- 
 rature of the bath; but care must be taken not to allow any 
 sensible variation. The contents of the containing vessels acquire 
 the temperature of the bath in an hour, provided the latter has 
 been kept, all the time, at a fixed temperature. 
 
 For heating to redness, Liebig's furnace, Fig. 139, or Hoff- 
 man's furnace, Fig. 166, must be used ; but it will be necessary 
 to place the tubes in the centre of a larger sheet-iron tube, so as 
 to intercept the contact of the flame with the glass. When glass 
 flasks are used as the containing vessels they should be sealed by 
 closing the mouth over a blast lamp; but as these vessels are not 
 capable of resisting a pressure of more than three or four atmo- 
 spheres, tubes are preferable, and almost exclusively used. The 
 glass material of which they are made should be very refractory, 
 free from lead, and insensible to the action of chemical agents. 
 That kind of tube used for organic analyses will be very suitable, 
 provided it is sufficiently thick. The thickest resist the tension 
 of water (steam) up to 520, and that of spirits of turpentine as 
 high as 680 F. ; or, in other words, they will stand a pressure 
 of 50 to 60 atmospheres. 
 
 When extreme temperatures are required, it is not necessary 
 to resort to tubes of other and more resistant material than glass, 
 for those of the latter can be made available by proper manage- 
 ment. To this end, the substances to be acted upon are inclosed 
 in a tube of about four-tenths of an inch in diameter, which, in 
 its turn, is placed in an outer tube containing a liquid less vola- 
 tile than those in the inner tube, and of such a nature as will not 
 cause the explosion of the enveloping tube, but only counteract, 
 by its tension, a part of the internal pressure of the inner tube. 
 Alcohol and ether may be thus heated to 680 by using essence 
 of turpentine as the liquid in the exterior tube. 
 
 In preparing the tube, the end should be closed in the flame 
 without the use of a blowpipe ; and subsequently annealed. After 
 cooling, the solid reagent, if such is to be used, must then be intro- 
 duced, and the other end carefully drawn out to a point. Great care 
 must be taken in this manipulation to preserve, in the different 
 parts of the tube, the original proportion of internal diameter and 
 
HEATING IN CLOSE VESSELS. 379 
 
 thickness; for it is especially upon this mutual ratio, and not 
 upon the absolute thickness, that the power of resistance depends. 
 When the tube is cool, the liquids are then introduced, and the 
 point sealed in the flame of the lamp. The point of closure must 
 be very fine, as in the disengagement of gases it allows the open- 
 ing of tubes without explosion. 
 
 If the action of the air is to be avoided, before sealing the 
 tube, the latter must receive an atmosphere of carbonic acid or 
 hydrogen, and this is furnished from a generator, Fig. 172, the 
 delivery-tube of which connects with its point. After letting in a 
 continuous current for 8 or 10 minutes, the operation is com- 
 pleted. 
 
 The quantity of liquid to be introduced into the tube varies 
 with the degree of heat to which it is to be carried ; they may be 
 filled to two-thirds their capacity with liquids which are to be 
 heated from 650 to 750. In all cases they are set perpendicu- 
 larly in the bath, and so as to be entirely covered by the oil. 
 
 Tubes which are to be heated to redness must have a length of 20 
 to 24 inches ; and the charge of liquid introduced into them may 
 be 1 to 1J per cent, of their capacity. When gases are to be 
 subjected to treatment, the tube is drawn out, so as to present a 
 very slender neck, with a funnel-shaped mouth, filled over mer- 
 cury, and dexterously sealed at the neck by drawing off the fun- 
 nel-mouth over the lamp. 
 
 When the tube has been sufficiently heated, it is to be taken 
 from the bath and opened, but as it may contain gases in such a 
 quantity and under such a pressure as may produce explosion 
 upon the least shock, great care is necessary to prevent accidents. 
 
 If the generation of a permanent gas, during the reaction, is 
 anticipated, the tube must be inclosed in several successive enve- 
 lops of sheet-iron, and so secured at both ends that only the tip 
 of the drawn-out end shall project. After the heating, and when 
 the bath is cooled completely, the screw-nut is removed from the 
 iron tube, and the latter slightly inclined, so as to allow the glass 
 tube to fall out gently upon a cloth. 
 
 If it is not desired to study the gaseous products of the ope- 
 ration, the tube is then wrapped around with three or four folds 
 of the towel, so as to leave only the point projecting, which is 
 then clipped off with a pair of pincers. If the effervescence 
 
380 LUTES. 
 
 produced by the disengaged gas is excessive, and causes loss of 
 liquid, then the lower end may be broken over a beaker glass. 
 
 In certain cases, it is necessary that this manipulation should 
 be practised at a little distance to avoid personal injury; for 
 example, in heating to redness tubes containing one-fifth their 
 volume of hydrochloric ether in contact with hydriodate of am- 
 monia, the resulting gases are sometimes so abundant that it is 
 impossible to open the tube without explosion, and in such case, 
 if the solid products are the only ones required, then the tube 
 may be wrapped completely up in a cloth and thrown on the 
 floor. The solid bodies will be found in the cloth mixed with the 
 fragments of glass. , 
 
 If the gases are the required products, then the tube must be 
 quickly passed up into an inverted receiver or tube, filled with 
 mercury, and its point broken against the interior of the top. 
 The receiver should be held at an inclination of thirty degrees, 
 and in such a manner as to protect the person in case of explo- 
 sion. For greater safety, it is advisable to envelop the receiver 
 in a sheet-iron casing. 
 
 The disengaged gases should be studied immediately, as they 
 may, in some instances, undergo rapid changes over mercury, by 
 the loss of one or more of their components. As an instance, 
 Berthelot observes, that a mixture of hydrogen and carbonic acid 
 lost all of the hydrogen, even with two intervening fluid strata, 
 one of spirits of turpentine of four-tenths of an inch thickness, 
 and the other of mercury fifteen times as deep. 
 
 CHAPTER XVIII. 
 
 LUTES. 
 
 IN all combinations of two or more pieces of apparatus or 
 parts of them, there is a necessity, in chemical operations gene- 
 rally, of some means of hermetically closing the interstices of 
 their joints so as to protect the inclosure from all outward com- 
 munication. This is particularly requisite in SUBLIMATION, DIS- 
 TILLATION, and other heating operations, and indeed in all expe- 
 
CAOUTCHOUC, BLADDER, FLAXSBED LUTES. 381 
 
 riments with gases and liquids, wherever it is desired to confine 
 the volatilized particles within the vessels and to prevent their 
 escape into the atmosphere and consequent loss. 
 
 To accomplish these ends we make use of lutes, which must 
 vary in composition and mode of application with the material 
 and construction of the apparatus, the temperature at which it is 
 to be heated, and the nature of the generated products. 
 
 Caoutchouc. This substance, in sheets, is particularly useful 
 for forming flexible tubes by which joints may not only be ren- 
 dered hermetical but also flexible. For delicate apparatus it is 
 particularly applicable even at high temperatures. The tubes are 
 made as directed at p. 304, and tied above and below the joint 
 as at x, Fig. 218. Sometimes india-rubber is replaced by mus- 
 lin, payed over after its adjustment around the joints with a 
 paste made by the mixture of caoutchouc and spirits of tur- 
 pentine. 
 
 Bladder. Bladder well cleansed and divided into strips an- 
 swers very well to a limited extent. For example, when moist- 
 ened and coated with white of egg or solution of bone-glue or of 
 isinglass, it forms an excellent covering for the joints of retorts, 
 tubes, and the like, to the surfaces of which it adheres tenaciously. 
 When, however, the contained ingredients generate corrosive 
 vapors, and so rapidly as to strain the apparatus, the bladder is 
 unserviceable. 
 
 Flaxseed Lute. Flaxseed meal mixed to the consistence of a 
 paste with water, milk, lime-water, or starch paste. This lute is 
 very manageable and impermeable, but does not withstand a heat 
 greater than about 500. 
 
 If just the sufficient quantity of water be added to quicklime 
 to reduce it to a dry powder, and the two mixed well and rapidly 
 with white of egg diluted with its own volume of water, and the 
 mixture spread immediately upon strips of linen and applied to 
 the part, which is then sprinkled with quicklime, a good cement 
 is made. Instead of white of egg, lime and cheese may be used, 
 or lime with weak glue-water or blood. This lute dries very 
 rapidly, becoming very hard, and adhering strongly to the glass, 
 but its great inconvenience is the want of flexibility. 
 
 In spirituous distillations, the joints of the apparatus may be 
 closed very readily and effectually by a stiff paste of equal 
 
382 LIME, PLASTIC, RESINOUS LUTES. 
 
 weights of whiting and flaxseed meal, mixed with water. We 
 Lave found this lute invaluable notwithstanding its want of flexi- 
 bility. It is the most easily made and most cleanly of all lutes, 
 and when the pressure of the contained vapor, is considerable, it 
 can be covered with strips of bladder soaked in solution of bone- 
 glue, which will prevent all leakage. 
 
 Lime and Bone-G-lue. Freshly slacked lime made into a 
 thick paste with a strong solution of bone-glue, makes an adhe- 
 sive lute very applicable for closing the joints of vessels which 
 are to be subjected to high heats ; as, for example, those in which 
 the distillation of lime and sal ammoniac is conducted for the 
 production of gaseous ammonia. 
 
 Plaster of Paris. Calcined gypsum made into a paste with 
 glue or starch water, answers the same purposes as the above. 
 When covered with strips of bladder it is rendered entirely im- 
 permeable by gases. A coating of oil or of a mixture of oil and 
 wax has the same effect as the bladder, and the lute will then 
 stand a dull red heat. 
 
 Plastic lute is made by dissolving melted caoutchouc in hot 
 linseed oil, adding finely powdered pipe-clay and kneading the 
 whole together into a homogeneous mass. The longer it is 
 kneaded the better is its quality, and to prevent its hardening 
 the caoutchouc should not be in deficient proportion. If it should 
 become hard by keeping, it may be softened by kneading with a 
 little spirits of turpentine. 
 
 This lute closes the joints without hardening, and can be re- 
 moved at any time during the operation, to allow a change in the 
 position of the parts of the apparatus. 
 
 For the distillation of acids or other corrosive vapors, it is very 
 applicable. 
 
 Soft cement is prepared by fusing yellow wax with half its 
 weight of crude turpentine and a little Venetian red, in order to 
 color it. It is very flexible,, and takes any desired form under 
 the pressure of the fingers. It is extremely useful at common 
 temperatures for tightening tubes in cork, and as a coating for 
 rendering corks impermeable to gases. 
 
 Resinous, or hard cement, is made by fusing together at the 
 lowest possible temperature, 1 part of yellow wax and 5 or 6 of 
 resin, and then adding gradually 1 part of red ochre, or finely 
 
IRON AND FIRE LUTES. 383 
 
 powdered brickdust (plaster of Paris succeeds very well), and 
 then raising the temperature to 212 at least, until no more 
 froth arises, or agitation takes place, and stirring it continually 
 until cold. This cement is employed in a hot state, and is very 
 much used for fixing brass caps, &c., to air-jars, and as an im- 
 permeable coating for the interior of wooden vessels. 
 
 Lute for joining Glass and Steel A saturated solution of 
 mastic in alcohol, mixed with a solution of isinglass in dilute 
 spirits, to which is added a small portion of galbanum or ammo- 
 niac, is an excellent cement for joining glass to glass, or glass to 
 steel. The mixture must be kept in a well-stopped bottle, and 
 be always warmed previous to use. 
 
 Lute for joining Crucibles. A mixture of fine clay and ground 
 bricks kneaded into a paste with water, holding in solution one- 
 tenth of borax, answers admirably for luting the joints of super- 
 posed crucibles. An excellent lute for this purpose and also for 
 metallic subliming vessels, is finely powdered Stourbridge clay, 
 containing a little sal enixum, and made into a stiff paste with 
 water. 
 
 Iron Cement. This mixture is used for making permanent 
 joints generally between surfaces of iron. Clean iron borings or 
 turnings are to be slightly pounded so as to be broken, but not 
 pulverized ; the result is to be sifted coarsely, mixed with pow- 
 dered sal ammoniac and sulphur, and enough water to moisten 
 the whole slightly. The proportions are, 1 sulphur, 2 sal ammo- 
 niac, and 80 iron. No more should be mixed than can be used 
 at one time. 
 
 lire Lute. The best fire lute is that employed by Mr. Parker, 
 and is composed of good clay 2 parts, sharp washed sand 8 parts, 
 horse-dung 1 part. These materials are to be intimately mixed ; 
 and afterwards the whole is to be thoroughly tempered, like 
 mortar. Mr. Watt's fire lute is an excellent one, but is more 
 expensive. It is made of finely powdered Cornish (porcelain) 
 clay, mixed to the consistence of thick paint, with a solution of 
 borax, in the proportion of two ounces of borax to a pint of hot 
 water. 
 
 Fat lute is prepared by mixing dry clay, in a fine powder, with 
 drying oil, so that the mixture may form a ductile paste. It 
 should be kept under cover, preferably in a greased bladder. 
 
384 LUTE FOR COATING FIRE VESSELS. 
 
 When this paste is used, the part to which it is applied ought to 
 be very clean and dry, otherwise it will not adhere. This lute is 
 adhesive, and stands a pretty high heat, but requires to be fast- 
 ened down with strips of bladder. Its greatest disadvantage is 
 the difficulty of stopping holes which may be blown through it by 
 escaping vapor. 
 
 Lead and Oil Lute. Red lead mixed with boiled linseed oil 
 is excellent for sealing the joints of steam- vessels. It hardens 
 readily and bears a high heat. 
 
 Lute for coating Fire Vessels. Faraday gives the following 
 directions for luting iron, glass, or earthenware retorts, tubes, &c., 
 for furnace operations. When the lute has to withstand a very 
 high temperature, it should consist of the best Stourbridge clay, 
 which is to be made into a paste, varying in thickness according 
 to the judgment of the operator. The paste should be beaten until 
 it is perfectly ductile and uniform, and a portion should then be 
 flattened out into a cake of the required thickness, and of such a 
 size as shall be most manageable with the vessel to be coated. 
 If the vessel be a retort or flask, it should be placed in the middle 
 of the cake, and the edges of the latter raised on all sides, and 
 gradually moulded and applied to the glass ; if it be a tube, it 
 should be laid on one edge of the plate, and then applied by roll- 
 ing the tube forward. In all cases, the surface to be coated should 
 be rubbed over with a piece of the lute dipped in water, for the 
 purpose of slightly moistening and leaving a little of the earth 
 upon it ; if any part of the surface becomes dry before the lute 
 is applied, it should be re-moistened. The lute should be pressed 
 and rubbed down upon the glass, successively from the part where 
 the contact was first made to the edges, until all air bubbles are 
 excluded, and an intimate adhesion effected. When one cake of 
 lute has been applied, and is not large enough to cover the whole 
 required surface, another must be adapted in a similar manner. 
 Great care must be taken in joining the edges, for which purpose 
 it is better to make them thin by pressure, and also somewhat 
 irregular in form, and if at all dry, they should be moistened with 
 a little soft lute. The general thickness may be about one-quar- 
 ter to one-third of an inch. 
 
 Being thus luted, the vessels are afterwards to be placed in 
 a warm situation, over the sand-bath or near the ash-pit, or in 
 
MODE OF APPLYING LUTES. 385 
 
 the sun's rays. They should not be allowed to dry rapidly or 
 irregularly, and should be moved now and then to change their 
 positions. 
 
 To prevent cracking during desiccation, and the consequent 
 separation of the coat from the vessel, some chemists recommend 
 the introduction of fibrous substances into the lute, so as mecha- 
 nically to increase the tenacity of its parts. Horse-dung, chopped 
 hay and straw, horse and cow hair, and tow cut short, are amongst 
 the number. When they are used, they should be added in small 
 quantity, and it is generally necessary to add more water than 
 with simple lute, and employ more labor to insure a uniform 
 mixture. It is best to mix the chopped material with the clay 
 before the water is put to it, and upon adding the latter, to effect 
 the mixture, at first by stirring up the mass lightly with a pointed 
 stick or fork ; it will then be found easy, by a little management, 
 to obtain a good mixture without making it very moist. 
 
 The luting ought to be made as dry as possible, consistent with 
 facility in working it. The more wet it is, the more liable to 
 crack in drying, and vice versd. 
 
 Mr. Willis recommends, when earthenware retorts, &c., are to 
 be rendered impervious to air, the following coating. One ounce 
 of borax is to be dissolved in half a pint of boiling water, and 
 as much slacked lime added as will make a thin paste. This 
 composition is to be spread over the vessel with a brush, and 
 when dry, a coating of slacked lime and linseed oil is to be ap- 
 plied. This will dry sufficiently in a day or two, and is then fit 
 for use. 
 
 Cement for Labels. Gum tragacanth boiled with hot water 
 makes the most adhesive paste for securing labels upon glass or 
 other smooth surfaces. The addition of a few drops of acetic 
 acid retards its decomposition and keeps it unaltered for a long 
 time. By moistening the labels with a very weak alcoholic solu- 
 tion of corrosive sublimate, before pasting them on the bottles, 
 they are rendered proof against the obliterating action of mould 
 and dampness. 
 
 Mode of applying Lutes. Lutes are applied whilst soft, being 
 adjusted to the joints by the hand. As they become dry, occa- 
 sional compression by the fingers is necessary to render them 
 compact. So also when any leaks occur they must be closed 
 
 25 
 
386 THE BAROMETER. 
 
 with fresh portions of lute smeared over and pressed in by the 
 end of the thumb. When bladder or muslin is to be pasted over 
 lute, the joint made with the latter must first have dried. 
 
 When the operation is finished, and the apparatus is to be dis- 
 connected, the lute must be removed first with the hands. If, as 
 is often the case in the use of hard lutes in fire processes, they 
 adhere tenaciously, then the use of a knife, or when the vessels 
 are metallic, a chisel becomes necessary. 
 
 CHAPTER XIX. 
 
 THE BAROMETER. 
 
 THE Barometer, so important in its discovery as marking a 
 great epoch in the history of science, has not become less so in 
 its subsequent varied applications as an indispensable instrument 
 for physical research. Not to speak here of its use in meteo- 
 rology for indicating the changes that are occurring, periodically 
 or irregularly, in the weight of our atmosphere, or of its employ- 
 ment in geography for determining expeditiously and with rea- 
 sonable accuracy differences of level between different points of 
 the earth's surface, the demand for its appliance in the labora- 
 tory is almost ceaseless. Not a weighing can be made, at least 
 where the aim is minute precision, of solid bodies, without its ob- 
 servation, unless (what is rarely the case) the object to be weighed 
 and the weights themselves are of the same material, or have the 
 same specific gravity; while in the measurement of gaseous 
 bodies, whose volume, at any moment, evidently is regulated by 
 the pressure of the atmospheric medium which circumscribes 
 them,jts readings have to be continually combined with what- 
 ever other observations that have been made, in order to educe 
 the proper arithmetical result. 
 
 With such frequency of necessary and varied appliance, there 
 might be expected (as is in fact realized) a corresponding variety 
 in the arrangements, both formal and substantial, of the instru- 
 ment itself; all subject, however, to one essential condition, viz., 
 the establishment and maintenance of a perfect vacuum in some 
 part of the apparatus. Besides this indispensable condition there 
 
WHEEL-BAROMETER. 387 
 
 are others, too, of greater or less generality, which have also to 
 be considered ; such as the precision with which the zero of the 
 scale can be ascertained, the permanence of such zero, the sym- 
 pathy between the scale itself and the material movement in the 
 apparatus which it is intended to measure, the openness of said 
 scale, or the minuteness with which its readings can be made, &c. 
 There will be occasion to indicate these conditions more expressly 
 in the account, which is of sufficient interest to be given here, 
 briefly, of the main modifications which the instrument has suc- 
 cessively and at divers times undergone. 
 
 All these modifications may, for convenience in description, be 
 grouped into two divisions consisting, 1st, of Stationary Baro- 
 meters ; and, 2d, of Barometers which are intended to be port- 
 able. These last, because of the geographical use which stimu- 
 lated their device, are ordinarily termed Twowntaw-barometers ; 
 and by the former are meant such as not being devised for 
 transportation require a special caution in being moved from 
 place to place, and a treatment afterwards more or less equiva- 
 lent to the pains which were requisite in their being first set up. 
 In other respects, as, for instance, in regard to the conditions 
 which have been just spoken of, there is no generic difference 
 between them, only that while the mountain-barometers can fulfil 
 at all times the functions of the stationary ones, the converse 
 does not hold good. Hence, except for purposes of ornament or 
 amusement, and for aims which may be called extra-technical, 
 stationary barometers are now rarely constructed. But whenever 
 or however constructed, they consist essentially of a glass tube, 
 closed at one end, set vertically, with the closed end uppermost, 
 and containing some fluid mercury, sulphuric acid, water, &c., 
 the height of the column of which will be, of course, inversely 
 as its specific gravity, in order to be in equilibrium with the pres- 
 sure of the atmosphere ; and their distinctive characteristic is the 
 permanent aperture of the lower end of the tube, and the direct 
 contact of the fluid column there with the external air. 
 
 Of this class the wheel-barometer may serve as a type. 
 
 Wheel-Barometer. -This is the instrument most generally pro- 
 cured when the object is to have an amusing weather-glass ; and 
 its construction can be readily understood from the adjoining 
 sketch, Fig. 325, in which the dotted lines show the tube turned 
 
888 WHEEL-BAROMETER. 
 
 up into a short syphon, through whose permanent aperture a float 
 
 enters and rests on the mercury sur- 
 face, counterpoised so as to yield to or 
 follow that surface, by a weight the 
 connecting-string of which passes over 
 a pulley, as seen also in dotted lines. 
 The arbor of this pulley passes hori- 
 zontally to the outside of the casing, 
 and there is fitted with an index as 
 shown, which index revolves to the 
 left hand or to the right, according as 
 the surface of the mercury in the 
 syphon rises or falls, and points out 
 on the graduated circle around it the 
 proportionate extent of such rise or fall. As the aggregate 
 weight of the float and counterpoise is very small, and might not 
 create friction enough to prevent the string connecting them from 
 slipping on the pulley, it is usual to sever said string, and attach 
 its ends to the pulley, which is turned with a double groove. The 
 diameter of this pulley is most conveniently made such that a 
 half revolution shall correspond to the range that is exhibited on 
 the dial. When the range takes in the whole circumference of 
 the dial-plate, of course a whole revolution of the pulley becomes 
 necessary, and the string is better unsevered. It is plain that in 
 this arrangement of two columns, the vertical movement of either 
 is but half of what it would be in a single one ; and in so far the 
 scale, were it a vertical one, would be only half as serviceable ; 
 but this can be counteracted to any extent, and is so in a greatly 
 multiplied proportion by the reading being circumferential. 
 Wheel-work is sometimes attached to the pulley-arbor, by which 
 minute readings can be made still more sensible. 
 
 But, with all this, the friction of the apparatus, and the diffi- 
 culty of boiling the mercury in the tube, without which ebullition, 
 the freedom of the column from air and the perfection of the 
 vacuum above can never be obtained, have consigned this form to 
 uses where accuracy is not aimed at, and for a laboratory imple- 
 ment it is altogether unsuitable. 
 
 Barometers of the other kind, whose unsealed extremity yet 
 admits of being cut off at discretion from connection with the ex- 
 
NEWMAN'S BAROMETER. 389 
 
 ternal air, may be divided into two classes, viz., cistern and 
 syphon barometers. In the first, the original single tube, which 
 with Toricelli or Pascal plunged its open extremity into a wide 
 cup or bowl of quicksilver, has its own cup or cistern permanently 
 attached to it, protected from fracture by suitable precautions to 
 support and strengthen it. 
 
 Newmans Barometer. In some kinds, as in the barometer of 
 Newman, the cistern is made of iron, and the passage for air, 
 from the outside to the inside, is effected by means of a screw- 
 plug, which is removable at pleasure. When this is open, the 
 pressure maintains the mercurial column at a corresponding 
 height, which is read off with the aid of a vernier from the en- 
 closing brass tube ; if this pressure increases the column rises ; if 
 it diminishes the column falls. In either case, it is clear that the 
 displacements in the tube correspond to inversely proportionate 
 displacements in the cistern, by which the level of the fluid there 
 is raised or depressed ; by which it differs from what was assumed 
 in the laying off of the scale as its starting-point or normal-zero, 
 and by which there is, to the extent of difference in question, an 
 error in the apparent height of the column. As this normal-zero 
 mark, as well as the mercury surface in the cistern, are no longer 
 visible after the instrument has been put together, the correction 
 of this error has to be found in a previous comparison made by 
 the maker, and furnished with or recorded on the instrument, of 
 the relative capacities of the tube and of the cistern. If the tube 
 and cistern were alike perfectly cylindrical, it would be sufficient 
 for ascertaining this correction to know their diameters respec- 
 tively, to the squares of which the displacements would be in- 
 versely proportionate. Thus, if the tube was 0-25 inch bore, 
 and the cistern 2-5 inches diameter, or 10 times as great, then 
 a fall of 1 inch in the tube would be compensated by a rise of 
 0-01 inch in the cistern, or, in general, the rise in the cistern 
 would be T $5 of the fall in the tube, and vice versd. But, as this 
 regularity of shape is rarely or never existing, the usual mode is 
 to fill the entire tube, or a known length of it, with mercury, and 
 then extravasating it into the cistern, to measure the difference 
 of level which has been produced by the addition. So, if 30 
 inches length of tube is found to contain a quantity of mercury 
 enough to raise, when poured into the cistern, the previous sur- 
 
390 NEWMAN'S BAROMETER. 
 
 face by 0-3 inches, the technical correction for capacity of cistern 
 is T ^ (as before) of the difference between any actual reading 
 and the reading of the column originally, when, in the construc- 
 tion of the instrument, the zero of the scale was adjusted to the 
 surface of the mercury in the cistern. This last-named reading 
 is by artists called the neutral point, and is stated along with 
 the correction for capacity. It follows from the very epithet 
 neutral, as well as from what has been said just now, that the 
 application of the capacity-correction, i. e. whether additively or 
 subtractively, depends upon which side of the neutral point the 
 surface in the cistern, at the epoch of the actual reading, may 
 happen to be, t. e. whether above or below. If the actual read- 
 ing is greater than that for the neutral point, then the cistern- 
 surface must be below said point, and the correction for capacity 
 is additive, and vice versd. 
 
 Thus, for example, the correction for cistern- capacity in a 
 given case was 47, and the stand of the neutral point was 30-180 
 inches. Upon one occasion the reading of the column was found 
 to be 30-526 inches. Of course, the ascent in the tube had been 
 (30-526 30-180 =) 0-346 inch; and the corresponding depres- 
 sion in the cistern had become ( =) 0-008 inch, which, 
 
 because of its sign, is additive, and, therefore (30-526 + 0-008 =) 
 30-534 is the reading that would have been shown, if, by any 
 contrivance, the cistern-surface could have been maintained at 
 the zero of the scale. So, again, with the same barometer oc- 
 curred an apparent stand of 29-742 inches, showing a descent in 
 the tube of (29-742 30-180 =) 0-438, and a corresponding 
 
 rise in the cistern of = 0-011 inch, which, because 
 
 41 
 
 of its sign, is subtractive, and the true reading would have been 
 (29-742 0-011 =) 29-731 inches, could the zero have remained 
 as at first. - ; * : 
 
 The cumbrousness of this correction, and the possibility of 
 error from confusing the signs, and adding where one ought to 
 subtract, or vice versd, stimulated devices for maintaining the 
 zero so as to dispense with the necessity of any correction. The 
 readiest suggestion was to make the bottom of the cistern mov- 
 able, so as to be able always to restore the surface there to the 
 
TROUGHTON'S BAROMETER. 
 
 391 
 
 Fig. 326. 
 
 original zero from which the graduation started. Of course, the 
 surface in the tube would, in such case, undergo an equable dis- 
 placement, and there the apparent reading became normal and 
 true. 
 
 One of the modes of effecting this is that proposed and executed 
 by Mr. Troughton some seventy years since, and, in fact, prece- 
 ding by nearly half that period the iron cisterned barometers of 
 Newman, which have been just now spoken of. The details of 
 Troughton's arrangement will be easily understood from the ad- 
 joining sketch; and they have so far approved themselves in 
 practice as to be substantially and with but slight variations in 
 form perpetuated to the present day in England and America. 
 
 Troughton's Barometer. The sketch of this instrument, Fig. 
 326, is restricted to the lower part of the apparatus, and is in- 
 tended to show within a glass cylinder, 
 of about 2-5 inches in diameter, and as 
 much in height, whose bottom of buck- 
 skin, cemented on to the rim, and still 
 farther supported there by a brass ring 
 that is screwed up tight by the outer 
 brass casing, enables it to hold the mer- 
 cury. The top is of wood or iron, also 
 leathered, through which the tube plunges 
 into the mercury; and appropriate shoul- 
 der-pieces serve both to steady the tube 
 and to receive and bear the outside brass 
 cylinder that encompasses and protects 
 the tube. The cistern thus furnished is 
 enclosed in a brass cylinder, in the base 
 of which works vertically a screw termi- 
 nated above in a suitable disk, that holds 
 and can be made to press against the lea- 
 ther bottom, and thus enlarge or diminish 
 the capacity of the cistern. This outside 
 brass cistern cover is not everywhere continuous ; but about one- 
 fifth of the height from the top has two opposite horizontal slits 
 cut in it about 0-25 inch wide, thus allowing one to see through 
 the glass the surface of the mercury, and the stem of the tube 
 when the screw is lowered. The upper edge of these slits is the 
 
392 TROUGHTON'S BAROMETER. 
 
 zero of the graduation and the normal level of the surface in the 
 cistern ; and to this edge, the eye being applied at the same level 
 and receiving the light through from the opposite side, the sur- 
 face of the mercury is lifted by working the screw until the line 
 of light thus received becomes the least possible, or until the 
 slightest further turn of the screw would shut it out entirely. 
 This phenomenon of the minimum visibile, or the least line of 
 light, is the test of the zero also equally when the mechanical 
 adjustments happen to be made in the contrary direction, and 
 the screw to be lowered instead of raised. 
 
 As to the upper part of the Troughton barometer, it may be 
 said that the glass tube is sheltered by a brass one rather larger 
 than itself; which brass tube is continuous for about half the 
 height, and for the remainder is slotted on both sides opposite, 
 so as to expose to view the mercurial column and the tube to near 
 its very top. On one edge of one of these slots the graduation 
 is made, its zero being the edge of the slit in the cistern before- 
 mentioned, its actual division commencing at about 15 inches, being 
 continued generally up to 31 inches, and its subdivisions capable 
 of being read to ^\ Q or sometimes y^^ of an inch, by means of 
 a vernier, which is inscribed on a smaller brass tube that moves 
 inside of the slotted one, and is so rebutted as to present the 
 vernier always to the graduation. The motion of this sliding- 
 tube, through spaces of one-tenth of an inch and upwards, is by 
 hand ; its smaller motions are regulated by a screw which works 
 vertically downwards in the very top of the brass casing, and by 
 means of which the lower edge of the sliding-tube can be brought 
 into optical contact with the meniscus or upper convex surface of 
 the mercury in the tube. This contact is effected in the same 
 way as that practised for the adjustment of zero, viz., the screw- 
 ing down until the line of light between the mercury-surface, 
 which coincides with the beginning of the vernier and the sliding- 
 edge, is the least possible. 
 
 "When the instrument is intended to be transported from place 
 to place, the function of the lower screw is then to force the column 
 up to the top of the tube, which is ordinarily visible, or rather 
 in order to avoid all strain and consequent fracture very near to 
 the ton. The sharp click that is made when after such screwing 
 
TROUGHTON'S BAROMETER. 393 
 
 up is done, the instrument is reversed, and the cistern held upper- 
 most, is evidence that the column is not unduly pressed. 
 
 This method of reading by an adjustable surface from a per- 
 manent and visible zero, has, from its facility and real merit, 
 obtained wide acceptation ; and many instruments are made which 
 have this feature, though very few other of the Troughton ar- 
 rangement. In those, the cistern is ordinarily made of wood into 
 the long slits or windows, in whose sides narrow pieces of glass 
 are cemented to allow the transmission of light ; the bottom is of 
 leather as before ; the screw works in the same manner ; the zero 
 of the scale is defined by the edges of the slit in the enclosing 
 brass case similarly. But the case to protect the tube is wood ; 
 and the scale is a flat slip of brass fastened against the jamb, 
 which is produced by cutting away, for a height of twelve or 
 fifteen inches from the top, about the third part of the matter of 
 the wooden cylinder, so as to show the tube on one side. The 
 reading is made by a vernier slide, worked by hand upon the slip 
 aforesaid, and having a curved lateral index that embraces a part 
 of the tube, and may be adjusted to the meniscus of the column. 
 Tube, and slide, and hollow, are all covered, when desirable, by a 
 portion of brass tubing, nearly a semicircle in section, which 
 works round horizontally, and screens, or at pleasure reveals, 
 what is within. These barometers are hung by a ring at the top 
 of the wooden case to some convenient support ; while, in the 
 Troughton arrangement, the suspension is by a collar and trun- 
 nions, placed about midway of the length, and resting in gimbals 
 that are set in the head of the tripod, which, when the instru- 
 ment is dismounted and reversed, serves for its packing-case. 
 
 This method of adjustment to zero, however, has not been so 
 favorably received by the Continental artists, who prefer the 
 mode adopted by Fortin. In this the glass cistern is much more 
 revealed than in the Troughton arrangement, in order to have 
 illumination enough to see the mercury-surface, and also an ivory 
 point which projects vertically downwards from the top of the 
 cistern. Otherwise, the arrangements are similar to what has 
 been described ; the bag is screwed up, and the cistern surface 
 displaced, until the direct image of the ivory pointer and its 
 image reflected from the mercury-surface just meet apex to 
 
394 
 
 HASSLER S BAROMETER. 
 
 Fig. 327. 
 
 apex. When this optical contact is made, the ivory point, whose 
 very terminus is in the plane of the zero of the graduation, just 
 touches without piercing the mercury-surface, and the scale is 
 properly adjusted to be read. 
 
 Hasslers Barometer. Mr. Hassler devised, some twenty years 
 ago, for use in the United States Coast Survey, something quite 
 different from all the types that have been indicated. In this, 
 the principal parts, the tube and the scale, are no longer attached 
 but separated, and the cistern, which may 
 be any convenient vessel that will hold 
 mercury, is also separate, and may be ap- 
 plied, during cessation of its functions here, 
 to various other uses or purposes to which 
 it may be fitted or convertible. The ad- 
 joining sketch of the suspensory and upper 
 part of the apparatus, Fig. 327, will render 
 the following brief description sufficiently 
 intelligible. The tube there is a naked 
 tube containing mercury. At its upper 
 end, a metallic ferrule embraces it, with a 
 curved piece of wire fastened to its basket 
 handlewise, and allowing it to be suspended 
 on a hook. To the lower end of the tube 
 is cemented a steel ferrule, with two pro- 
 jecting prongs or arms diametrically oppo- 
 site, over which slips, through guide-holes, 
 a steel plate having a leather cushion on 
 one side of the diameter to fit the end of 
 the tube. When this plate is pushed down, 
 two slots in the arms allow a key or wedge 
 to be slipped through, the pressure of which 
 forces the plate and cushion sufficiently 
 home to retain the mercury. This plate is 
 so pushed home and keyed when the tube is prepared for trans- 
 portation ; when it is set up for observation, of course, the key is 
 taken out, and the plate removed. The scale is a curved slip of 
 brass, ordinarily divided from 25 to 31 inches, and with a vernier 
 that reads down to yj^ of an inch, properly fastened to a light 
 steel rod, whose lower end is the zero of the graduation, and is 
 
HASSLER'S BAROMETER. 395 
 
 intended to be in contact with the cistern surface. The upper 
 end of the rod is tapped with a screw, which is intended to pass 
 through an oblong hole in a bracket, as seen in the sketch, and 
 to be retained on the other side by a nut. Another similar hole 
 in the same bracket is for a hook to support the barometer-tube, 
 which hook is likewise held and its motion regulated by a nut 
 above. The rectangularity of the hole, which corresponds to a 
 flattening of the sides of the screw, is intended to prevent the 
 turning of the whole apparatus when the nut is worked. At the 
 zero end of the steel rod, and at some prescribed distance above 
 the very zero (in fact, 0'5 inch), a mark is found going round 
 the rod ; to which mark it is intended, by working the nut before 
 spoken of, to adjust the fiducial edge of an ivory float (of exactly 
 the same height from its base to said fiducial edge as the pre- 
 scribed distance aforesaid), so that when the edge and the mark 
 correspond, the base of the float and the end of the rod are 
 exactly on the same level, both in contact with the mercury-sur- 
 face, and said surface, therefore, at the zero of the scale. 
 
 In the use of this form of instrument, supposing it just taken 
 out of its packing-case, and with the open end outwards, the first 
 thing is to withdraw the key that holds the plate ; then to remove 
 the plate ; then to pour a little clear mercury from the vessel used 
 as the cistern (and which is assumed as having been previously 
 filled from the travelling flask or otherwise) into the tube, which 
 is held a little inclined from the perpendicular at first in order to 
 let the new mercury wash off, as it were, any oxide or amalgam 
 that may have been formed, and which washing may be caught 
 either in the cistern or in some separate vessel ; then, when the 
 tube is quite full, to close it with the end of the middle finger so 
 as to prevent the escape of mercury, and, so closed, to invert the 
 tube and plunge its end in the cistern, withdrawing the finger 
 under the mercury cautiously so as to moderate the descent of 
 the column in the tube. Then the basket-handle ring is sus- 
 pended on the hook before-mentioned, and the tube is ready to 
 be measured. For this measurement, the scale is next applied 
 by slipping the ivory float over the lower end of the steel rod, 
 passing its lapped end through the appropriate opening in the 
 bracket, catching it there with the nut, and working the nut up 
 or down until the mark on the lower end corresponds with the 
 
396 ALEXANDER'S BAROMETER. 
 
 fiducial edge of the float. The distance apart of the holes in the 
 bracket, and the width of the graduated curved plate, are such 
 and so proportioned that when the tube and rod have been fast- 
 ened in the position indicated, the curved index projecting, as 
 seen from the vernier plate, embraces without touching the tube, 
 and can be readily brought, by means of the vernier-rack, to a 
 due coincidence with the top of the column, and the reading of 
 the scale then made. When the instrument is to be taken down, 
 the various motions that have been described have to be made in 
 a reversed order. For ascertaining the temperature of the mer- 
 cury a loose thermometer is either stood in the cistern, if the 
 sides of that vessel are high enough to retain it, or is hung from 
 the bracket by a suitable string or wire that allows it to plunge 
 properly into the cistern. This method of ascertaining the tem- 
 perature is a normal peculiarity in this arrangement, as will be 
 spoken of more particularly presently when the correction for 
 temperature comes to be discussed. 
 
 Alexander's Barometer. The same mode of applying the 
 thermometer is found in another arrangement by J. H. Alex- 
 ander, which presents some other peculiarities that appear to 
 have recommended it to frequent employment. This, like the 
 former, consists of a naked tube, whose open 
 Fig- 328. en( ^ terminated with a slip of platinum welded 
 
 on the inside for a purpose that will be pre- 
 sently spoken of in relation to deterioration 
 of barometers, bears also a sort of flat cistern 
 -|/ which is permanently full of mercury, and 
 
 5jJJ" which is shown in the adjoining Fig. 328. 
 This cistern is formed as follows : First, a 
 collar of iron is cemented on the outside of the tube near its ex- 
 tremity, to which is screwed permanently a bell-shaped dish of 
 iron open at bottom. The bottom is then closed by a sheet 
 of Russia iron thinned by hammering and then annealed until it 
 has become extremely flexible, which is cut round to fit on a 
 rebate within the dish, and is then firmly held there by a ring 
 of iron which screws inside of the dish and up to the rebate. A 
 hole which has been drilled horizontally, Fig. 329, into the side 
 of the dish, is closed by a screw-plug, which admits of removal 
 at discretion, and which, when removed, allows the mercury to 
 
ALEXANDER'S BAROMETER. 397 
 
 flow inward or outward of the dish. The object of all this appa- 
 ratus is to have both the dish and the tube quite full of mercury 
 when the instrument is not up for use ; and 
 the elastic bottom is intended to provide for Fig - 329 - 
 
 the expansions and contractions which take 
 place upon change of temperature, to which 
 the mass is always more or less subject. The 
 diameter of the bottom, therefore, is propor- 
 tioned to the capacity of the tube and dish in 
 such sort that the known elasticity of the 
 sheet is capable of adapting it in close contact with the mercury 
 within through a range of 60 on each side of the normal tem- 
 perature, which may be taken at from 60 to 62 Fahr. Such 
 close contact may be expected to be favorable for the exclusion 
 of air. 
 
 At any convenient point, say within a half inch of the dish, 
 the zero of the graduation is marked on the tube, upon which 
 also the division of the graduation is marked from 25 inches up- 
 wards to 31 inches for every one-tenth. A loose vernier made 
 of pearl (both for its transparency and ease of motion), and made 
 to hug the tube closely by a circular steel spring, subdivides the 
 graduation to 7 J n of an inch, which is supposed to be minute, all 
 things considered, as there is any necessity for. The closed end 
 of the tube, which is shrunk and then swelled in the process of 
 sealing, receives, when the instrument is set up, and is embraced 
 by a steel collar capable of being drawn tight by a screw, and 
 having a sort of basket-handle, as in the Hassler barometer, a 
 suitable iron bracket, with a hook and nut for Fi 33Q 
 
 elevating or depressing the tube when sus- 
 pended, and with a gimlet screw that serves 
 for either extempore or permanent fastening 
 of the bracket, provides the means of support both for the tube 
 and for the thermometer, as in the former case ; and finally, an 
 ivory float, shaped like a hat without a crown, and which is to be 
 slid over the tube before the collar is put on, and whose base 
 must correspond to the zero of graduation, completes the means 
 of adjustment, Fig. 331. In order to effect this correspondence, 
 another mark has been also placed upon the tube a certain dis- 
 
398 
 
 ALEXANDER S BAROMETER. 
 
 Fig. 331, 
 
 tance, say a half inch above zero, exactly equal to which distance 
 is made the height of the float before-mentioned from its base to 
 its fiducial edge. Of course, when said 
 fiducial edge is adjusted to the mark in 
 question, the base of the float is at zero. 
 And as this base is in contact with the sur- 
 face of the mercury in the outer cistern or 
 cup, the same adjustment determines the 
 mercury-surface as being at zero likewise. 
 When the instrument is to be set up, 
 and is just taken out of its packing-case 
 (which is a wooden sheath suitably lined), 
 with the cistern end uppermost, it is in- 
 verted, and held at an angle of about 50 
 with the horizon, its cistern is plunged 
 above the zero mark into a convenient cup, 
 or basin, or outer cistern, containing mer- 
 cury. The screw-plug is then extracted 
 under the mercury by means of an appro- 
 priate hook, Fig. 332, in order to avoid 
 soiling the metal by touching with the 
 fingers ; and the outward flow of the column 
 and its descent regulated by carefully 
 raising the tube to the vertical. The float 
 is then slid over the tube; the collar 
 screwed on ; its basket-handle caught by the hook in the bracket 
 previously fastened at a proper height above the cup ; the vernier 
 applied ; the thermometer immersed in the mer- 
 
 Fie 332 
 
 cury of the cup ; and after five minutes, to allow 
 P I QC3 of its assuming the temperature of the fluid, the 
 column is ready to be measured. 
 
 When the instrument is to be taken down, the same steps are 
 gone through in a reversed order ; the chief caution necessary 
 being to see that the tube is quite full to the very top (as it 
 always becomes at the suitable inclination) before the screw-plug 
 is inserted, and to insert said plug while the aperture for it is 
 beneath the surface of the mercury. 
 
 Such are the principal modifications of cistern barometers 
 requisite to be mentioned. Of the other groups, the syphon- 
 
GAY-LUSSAC'S BAROMETER. - 399 
 
 barometers, a sufficient type may be found in the only one that 
 will be described, viz., Gay-Lussac's Barometer. 
 
 Cray Lussac's Barometer. Of this form of instrument, dis- 
 embarrassed of its casing, the adjoining sketch -will give a satis- 
 factory illustration ; where it is seen to be composed of two pieces 
 of an ordinary barometer-tube, together surpassing 33 or 34 
 inches, and connected by a re-curved piece of glass tube with a 
 very small bore, the object of which is, by increasing the 
 friction as well as diminishing the mass of the column, 
 to dimmish also the strain or shock that would follow 
 every brusque movement. The instrument originally is 
 supplied with mercury, rather more than enough to fill 
 the upper large tube and the capillary-tube, including 
 its bend. When the instrument is reversed with said 
 bend uppermost, the mercury fills the bend itself en- 
 tirely, thus excluding the entrance of air, and the sur- 
 plus metal drops into the end of the tube near o ; at 
 which place there exists a small orifice for the admission 
 of the atmosphere to press on the column, and even for 
 additions of mercury if desirable, but too small and in- 
 troverted to allow the escape of the fluid from within in 
 any of the reversals which the instrument may undergo. 
 The sketch, Fig. 333, shows the apparatus in its direct 
 position, when the column in the upper tube will have 
 fallen to say s, and will stand in the lower one at say t. 
 It is evident that the vertical distance between the surfaces at these 
 two points is the height of the column of mercury which equili- 
 briates the pressure of the atmosphere. To measure this there are 
 various ways, as well when the necessary graduation was in- 
 scribed as at first upon the glass as when it is marked on the 
 other brass tube, which embraces and protects it. The most 
 usual is to take a zero midway between the two surfaces, as at z, 
 and to graduate upwards and downwards from that origin. A 
 movable vernier is attached to each scale, which is adjustable to 
 the surfaces respectively, and subdivides the direct readings : the 
 sum of the two readings is the height of the column sought. 
 
 The instrument is enclosed, together with a thermometer lying 
 along the limb s z (or sometimes the thermometer is unattached), 
 in a brass tube, which is slotted for some distance along both 
 limbs to allow the surfaces to be seen by transmitted light, which 
 
400 MORLAND'S DIAGONAL BAROMETER. 
 
 slots are coverable with a portion of another tube moving hori- 
 zontally, and serving as a screen, as in the instance of the wooden- 
 cisterned and cased barometers spoken of just now. So ar- 
 ranged, it is ordinarily capable of enduring all careful transpor- 
 tation and even ruder treatment, and forms one of the neatest 
 and most convenient portable barometers. In a laboratory, how- 
 ever, where this feature is not essential, one of its necessary 
 defects become more conspicuous, viz., that it requires two 
 readings, and thus doubles the time and trouble of observation. 
 
 If but one arm were read, it is obvious that the scale would 
 indicate but one-half of the change of level which may have taken 
 place from one epoch of observation to another ; for of the total 
 actual movement of the equilibriating column, equal parts, 
 whether of elevation or depression, will be borne in just recipro- 
 cal senses by the columns in the two limbs. And in so far the 
 errors of reading, whatever they might be, would be multiplied. 
 The chances of such multiplication are diminished upon the 
 double reading, if we suppose that the errors are liable to occur 
 in the same way, as is most likely. If such supposition is not 
 correct, then the error of reading will be of course multiplied. 
 
 Such errors, which are always possible, partly from the nature 
 of the apparatus and partly from a personal proclivity varying 
 both in its direction and its amount of the observer, are always 
 to be guarded against ; and this aim has led to sundry devices for 
 enlarging the scale, and thus virtually dividing its errors. The 
 wheel-barometer, which has already been mentioned, is one such 
 device ; where a range of one inch, for instance, in the vertical 
 column is multiplied, as it were, in the revolution of the index 
 over a circumference of eighteen inches. A similar contrivance, 
 applicable to the syphon barometer,'is, instead of letting the float- 
 string be connected with a pulley to attach it to the short arm of 
 a balanced lever, whose other arm may bear any assignable pro- 
 portion in length to said short arm, and the circular scale tra- 
 velled over by the extremity of which will be, of course, expanded 
 in the same proportion. 
 
 Morlond^ Diagonal Barometer. Another contrivance for the 
 same purpose is the so-called diagonal barometer of Morland, in 
 which the upper part of the tube instead of continuing vertically 
 is inclined to the horizon at any angle, and the scale is applied 
 
MORLAND'S DIAGONAL BAROMETER. 401 
 
 to the inclined limb. It is clear that the tube must be made 
 longer than the ordinary vertical one, in the ratio of the angles 
 of inclination, and that the divisions of the inclined scale will be 
 to the normal ones of the vertical scale in the proportion of the 
 cotangent of those angles respectively to radius. Another 
 method is that exhibited in the rectangular barometer, as it is 
 termed, where the mechanical arrangement is in some sense 
 the converse of the last, viz., the open end of the tube is bent for 
 an indefinite extent at right angles to the vertical. But here the 
 multiplication of the reading is in the ratio of the square of the 
 bore of the vertical and horizontal tubes respectively ; and the- 
 disparity of bore is either produced by enlarging considerably the 
 vertical bore through the range of its possible variation, or by 
 diminishing the bore of the horizontal tube until it becomes even 
 capillary. If, for instance, the vertical bore be 040 inch, while 
 the horizontal is 0*05 inch, it follows that the longitudinal spaces 
 to contain equal quantities of mercury must be 64 times as great 
 in the latter as in the former. Of course the scale is multiplied 
 in the same ratio. In this arrangement, the smaller the calibre 
 and the more the tube is kept perfectly horizontal, the less occa- 
 sion there is for a cistern ; the pressure of the atmosphere upon 
 the face of the mercury at the open end being always sufficient 
 to prevent any extravasation. Such extravasation will not take 
 place even with the swelled vertical bore, under ordinary circum- 
 stances. 
 
 This principle of varying the bore of the tube, so as to produce 
 motion through unequal lineal spaces, coupled with another of 
 using fluids in conjunction with mercury of vastly inferior specific 
 gravity, water, tartrate of potassa in solution, petroleum, &c., 
 has been very fruitful in suggesting modifications for expanding 
 the scale ; and the names of eminent geometers, such as Des 
 Cartes, Huggens, and Hooke, are still connected with arrange- 
 ments to this end, upon which they exercised no inconsiderable 
 ingenuity in invention or improvement. But the description of 
 these is unnecessary here; for at the period of their suggestion 
 the application of the barometer, as an instrument of research, 
 was limited and partial, and its destiny but vaguely anticipated, 
 so that a cumbrousness, which would now be found intolerable, 
 was then but an inconsiderable defect, while the very amplifica- 
 
 26 
 
402 ABIE'S SYMPIESOMETER. 
 
 tion of scale by the means resorted to, though there was nothing 
 left to be desired as to minuteness of reading, introduced errors 
 of another a-nd more radical kind, of which there was at that 
 earlier period no suspicion. 
 
 Water Barometer. How far certain modern arrangements 
 with the same aim are to be classed in the same category can 
 only be judged of negatively, in consequence of their limited ac- 
 ceptation. So, for instance, the great water barometer, erected 
 some twenty years since for the Royal Society of London by Mr. 
 Daniell, remains yet, as far as known, unimitated. The extreme 
 mobility of the fluid used in this, and the magnitude of its scale, 
 more than thirteen times that of a mercury column, render 
 its oscillations as frequent as every successive breath of air and 
 as capricious ; while the evaporation going on from its surface no 
 doubt fills with an atmosphere, though of low tension, the space 
 that ought to be a perfect vacuum. So, too, the sulphuric acid 
 barometer first constructed many years since, and recently re- 
 peated in an apparatus at the Smithsonian Institute. 
 
 The difficulties which have attended attempts to expand the 
 scale of the barometer in using mercury or lighter fluids, as well 
 as some other practical defects, have led to the employment, or 
 more correctly, the suggestion of substitute apparatus, in which 
 the object has been more or less met by what may be termed in- 
 direct methods. Among these may be mentioned 
 
 Adies Sympiesometer. This was principally intended to re- 
 place the ordinary barometer at sea, where the sudden and violent 
 motions of the vessel render the oscillations of an ordinary mer- 
 curial barometer either incapable of being read at all, or not very 
 reliable. These motions, therefore, are sought to be counteracted 
 in such a column by strangulating the tube in some convenient 
 place or places, or zig-zagging it, or twisting it in a spiral after 
 the manner of Passement. But, although the movement of the 
 column may be thus retarded, so as to insure the safety of the 
 instrument and the capacity of its being read, this gain is at the 
 expense of its permanent delicacy and susceptibility to minute 
 atmospheric variations in opposite senses. The aim of the sym- 
 piesometer is to cure this last defect also. The instrument itself 
 is bulbed at both ends and syphoned, with the lower bulb open to 
 the atmosphere. The upper bulb is filled with pure hydrogen ; 
 
ANEROID BAROMETER. 403 
 
 the lower one in part, as well as a portion of the upright tube 
 connecting them, with almond oil colored with alkanet root. It 
 is obvious that as the pressure of the atmosphere upon the oil 
 changes, so, inversely, will the normal volume of the enclosed 
 gas, whose limit is indicated by the surface of the oil column, 
 expand or contract ; and that the measure of compression of the 
 gas is thus indirectly a measure of the pressure of the atmosphere. 
 Hence the name, meaning literally "compression-measurers," 
 which has been given to it. The instrument itself is graduated 
 upon comparison with a mercurial barometer supposed to be ac- 
 curate ; and both are so suitably connected with an air-pump as 
 to make an artificial stand in the latter of successively 26, 27, 
 28, &c., inches, and the cotemporaneous stand of the oil-column 
 is marked on the sympiesometer-scale as corresponding inches 
 respectively. These spaces are then subdivided into T -J C , which, 
 of course, correspond to O'Ol inch on the ordinary mercurial 
 scale. Further, the volume of the enclosed gas is affected not 
 only by the atmospheric pressure, but also by changes of tempe- 
 rature. To save the necessity of calculating a correction on that 
 account an ingenious contrivance has been arranged, whereby the 
 inches-scale of the column slides with a rack worked by an out- 
 side knob along a fixed scale marked for degrees, counting from 
 above downwards. An ordinary thermometer is set in the frame 
 alongside of the oil-tube, and in observing the instrument, a zero 
 or index-mark upon the sliding-scale is made to coincide with the 
 identical degree on the fixed scale which is shown upon the ther- 
 mometer: the reading of the oil-column upon the sliding-scale is 
 the barometric reading required, reduced to the uniform tempe- 
 rature (32 or 62 F.), which may have been adopted for the 
 calculation of the correction. 
 
 There is no doubt of the sensibility of this apparatus to very 
 minute changes in atmospheric pressure ; but in consequence of 
 the liability of the gas to absorption by the oil, it is not so cer- 
 tain that the indications remain perfectly uniform during a long 
 period, or that they are permanently accurate. 
 
 Aneroid Barometer. This sympiesometric principle has been 
 also applied to another class of devices, known as aneroid or 
 fluidless barometers. The first suggestion of such device was 
 about a century ago by Mr. Zeiher, who prepared a hollow cylin- 
 
404 ANEROID BAROMETER. 
 
 der, completely freed from air, with two movable ends kept apart 
 by a light spring, which yields as the atmospheric pressure in- 
 creases, and recovers as that pressure diminishes. This is virtu- 
 ally weighing the atmosphere by a steel yard, whose unavoidable 
 friction would always be a function of the apparent reading; and 
 it seems to have been viewed in that light, and to have remained, 
 on this or some other account, a mere suggestion for another half 
 century, when Mr. Conte' took it up afresh, and actually caused 
 it to be executed, a form which he denominated a vacuum vase. 
 This was a lenticular vase, whose sides below of iron or copper, 
 above of thin sheet-steel, were kept apart by a series of springs. 
 From this vase the air was exhausted, and the vessel soldered up 
 air-tight. The whole weight of the atmosphere then falls 'upon 
 the flexible steel arch ; and as the resistance of the springs was 
 assumed constant, this cover-plate rises or falls as the atmospheric 
 weight varies. These variations are shown by means of an index 
 which vibrates upon a suitable dial-plate. But no provision was 
 made in this for the mechanical effects of change of temperature 
 in altering the resistance of the springs, as well as the proportion 
 of the parts that were concerned in the motion of the index, and 
 the irregularities from this cause forced the ingenious inventor 
 himself to acknowledge the insufficiency of the apparatus. 
 
 But, nearly a half century afterwards, another Frenchman, 
 M. Vidi, contrived and announced an instrument to which he 
 gave specifically the epithet aneroid, which was just now used 
 here as generic; and in which, by making the sides of the vacuum 
 vase not arched but corrugated, and by introducing within it a 
 permanent gas instead of metallic springs, and by connecting its 
 movement with springs outside, a compensation, in some degree, 
 is demonstrably afforded for variations of temperature. Thus, 
 although under an increased temperature, the capacity of the 
 vacuum vase tends to be itself increased, and so by expanding to 
 cause the index to move in a, corresponding direction, the dimi- 
 nution of elasticity, both in the sides of the vase and in the spiral 
 spring seen in the sketch, allows the pressure of the atmosphere 
 to be more effective, so that, in point of fact, the index would 
 move in the opposite direction, were it not checked by the in- 
 creased tension of the contained gas. This gas tension, then, 
 between the two opposing results of increased capacity of vase 
 
ANEROID BAROMETER. 
 
 405 
 
 (and thus a lifting of the levers), and of diminished elasticity of 
 springs (and thus their depression), is left to hold the balance, 
 and in its proper apportionment to cause an independent result, 
 which is strictly symmetrical with the variations of temperature 
 to which it is subjected. It is in this way, at least, that the 
 principal manufacturer of the instruments, Mr. Dent, accounts 
 
 Fig. 334. 
 
 for the regularity with which an aneroid once adjusted follows the 
 corrected readings of a mercurial barometer. 
 
 Fig. 335. 
 
 The annexed figures 334, 335, and 336, give an outside sketch 
 
406 
 
 BOURDON S BAROMETER. 
 
 of a ground projection and a perspective view of the interior of 
 the apparatus ; in which D shows the vacuum- vase, c the lever, 
 which, resting on the fulcrum B at one end, and on the spiral 
 spring S at the other, and keyed at K to the shaft that moves 
 with the motion of the vacuum-vase, communicates that motion 
 
 Fig. 336. 
 
 through the vertical rod 1, the arbor-levers and bow-piece 2, 3, 
 4, the horizontal rod and chain to the arbor of the index. This 
 arbor is kept lively, and the faculty of contrary motion in the 
 index maintained by a flat spiral spring, which is seen attached. 
 The readings of the instrument are adjusted to those of a mercu- 
 rial barometer by means of a screw, which is at the centre of the 
 back of the case, and by the motion of which the index also can 
 be moved. Of the two hands seen on the dial, the steel one is 
 the cursive index; the gilt one is only a register-hand, adjustable 
 by the nut on the outside of the glass, and set at any time to 
 correspond with the cursive, shows, at any other period, the vari- 
 ation that may have taken place in the pressure. 
 
 Finally, in regard to the reliability of this apparatus, it must 
 be said that, in spite of the correctness of its theory, and the 
 very ingenious manner in which the mechanical developments 
 have been contrived, it is hardly to be accepted as under all 
 circumstances an invariable substitute for the mercurial column. 
 
 Bourdon's Barometer. The metallic barometer of Bourdon is 
 
REGISTER BAROMETERS. 407 
 
 an aneroid arranged upon a somewhat different mechanical prin- 
 ciple. Instead of the vacuum-vase being a flat cylinder, working 
 by its face as in Vidi's, it is a horse-shoe hollow lenticule, the 
 changes of atmospheric pressure upon which cause the ends or 
 heels of the horse-shoe to approach or recede from one another. 
 These approaches and recessions, themselves very minute, are 
 multiplied by connecting-rods that work a winch-lever, whose 
 shaft is the arbor of a segment of a toothed wheel working into 
 a pinion set on the index arbor. 
 
 Wollaston and Regnault's Barometer. The thermo-barometer 
 of Wollaston, first suggested by Fahrenheit more than a century 
 and a quarter ago, and recently improved by Regnault, and from 
 its presumed special adaptation to the measurement of heights, 
 called the Hypsometric (or height-measuring) Barometer, acts 
 in a still more indirect manner, and furnishes indications that are 
 only hypothetically convertible into equivalents of a mercurial 
 column. It consists of a thermometer with a very open scale 
 (degrees divided to tenths or still lower) which is suitably exposed 
 to the vapor of boiling water, the vessel and lamp for which form 
 part of the apparatus. The thermometer shows, of course, the 
 temperature of the vapor which is formed, and is supposed to 
 show its temperature at the crisis of boiling, when its tension is 
 exactly equal to the atmospheric pressure. If this is so, and if 
 the tension of vapor at varying temperatures were accurately 
 known, or even uniformly stated, by different experimentalists or 
 theorists, and if the observation were momentaneous, or at least 
 but brief, the instrument would be a commendable and valuable 
 one. Actually, however, it is not, in these regards, suitable for 
 use in the laboratory, and, therefore, need not be farther de- 
 scribed here. 
 
 For the laboratory, an apparatus that would record successive 
 variations in atmospheric pressure would be exceedingly useful ; 
 and devices in this -aim have been occasionally tried, under the 
 name of 
 
 Register Barometers. But the friction occurring upon the 
 apparently necessary mechanical arrangements is so great as 
 seriously to impair the delicacy of the instrument, and to prevent 
 the reliable use of any of the contrivances which have been, up 
 
408 CONSTRUCTION OF BAROMETERS. 
 
 to this time, suggested, and whose description may therefore be 
 
 After this account of different forms of barometer, which all 
 require, more or less, the co-operation of a professional artist, it 
 will be well to explain how the experimentalist or student in the 
 laboratory may construct for himself an apparatus, which, with 
 only reasonable skill in manipulation, and ordinary good fortune, 
 will be capable of furnishing results as reliable and convenient as 
 any of the more elaborate arrangements which have been spoken 
 of. For this, a tube is to be selected (and, if possible, from 
 among such as have still both ends sealed), from 0*25 to 0-38 
 inch bore, as uniform in size, and as free from strise, and as thin 
 in the material as may be, and to be cut off (according to the 
 methods described for cutting glass tubes) to a length of 33 or 
 34 inches. The open end is then to be ground off square upon 
 an emery plate. About an inch or an inch and a half from the 
 open end, a suitable mark is to be made with a fine file, to serve 
 as a zero, from which, with a beam compass or an accurate fidu- 
 cial-edged scale, a space of 27 inches is to be laid off towards the 
 sealed end (care being taken to lay the line as nearly in the axis 
 of the bore as possible), and to be continued inch by inch up to 
 31 inches ; which inch divisions are then to be subdivided from a 
 scale, as mentioned, into tenths. For making these divisions ac- 
 curately, it is best to coat the part of the tube where they are to 
 fall with a thin layer of beeswax, or a strip of tissue or other 
 thin paper may be laid along the line, and cemented to the 
 tube with lip-glue. Upon the tube so prepared, the divisions in 
 question are first transferred with a pencil, and then cut into the 
 glass, either with a writing-diamond or a dentist's file. Either of 
 these implements will encounter no difficulty in any tube likely 
 to be selected. The tube so graduated is then to be carefully 
 wiped out by means of a screw ramrod, wrapped with dry, clean, 
 old linen, and all specks and adhering filaments are to be re- 
 moved. 
 
 Clean, fresh mercury will then be taken and sifted into the 
 tube against the side of the glass, so as to cause as little spatter- 
 ing and entanglement of air as may be, through a paper funnel 
 of the usual shape, and of a reasonably fine orifice, to a height of 
 5 or 6 inches above the sealed end ; which mercury is then to be 
 

 CONSTRUCTION OP BAROMETERS. 409 
 
 boiled in the tube itself over a charcoal fire, or better, a gas 
 burner of sufficient length to embrace the whole reach towards 
 the end of the operation. It is hardly necessary to advise that, 
 in order to promote the safety of the tube, it should have been 
 gradually warmed up through its entire length before urging the 
 mercury to ebullition. When all bubbles of air cease to be given 
 off, more mercury, previously heated, is to be similarly sifted in 
 to a height of 15 or 18 inches, and treated like the preceding 
 instalment ; after which a last addition is to be made, filling the 
 tube to (say) 3 inches of the top, or open end, and boiled as 
 before. Care is to be taken that each successive boiling should 
 be initiated below the joint, as it were, of the successive additions 
 to the column, in order to avoid driving any of the entangled air 
 downwards. The ebullition cannot be effected in the last three 
 inches of the tube ; and all that can be done is to sift into that 
 until running over hot mercury, which has been recently boiled 
 in a separate vessel, and to apply below and about the joint as 
 much heat as can be borne without extravasation of the fluid. 
 Placing, then, against the end of the tube, in such a manner as 
 not to cause any violent removals or out-splashings of the mer- 
 cury, the end of the middle finger, covered with a clean buckskin 
 or kid glove, or, still better, such a padded implement as is 
 figured under the preceding description of the Alexander barome- 
 ter, the tube is to be inverted and its end plunged in a porcelain 
 or glass cistern, cup, or basin, which has been previously supplied 
 with a suitable quantity of boiled mercury, whose specific gravity 
 has been ascertained and recorded ; and when raised vertical, 
 the finger or pad to be carefully withdrawn, so as to let down the 
 column easily and without shock. Then, the tube being held by 
 an assistant, sufficient wire or silk cord is to be wrapped, whip- 
 maker fashion, round the sealed end of the tube, to form a loop 
 for suspension, which loop can be hung upon a hook in a conve- 
 nient bracket, made as described for the barometer just men- 
 tioned, or in the absence of such a contrivance on a permanent 
 hook, in which case the adjustment will be made either in moving 
 the cistern itself by wedges under it, or by adding or withdrawing 
 portions of the mercury within. As the barometer is intended to 
 be stationary, this adjustment once made does not require to be 
 often repeated, though it should be verified for every series of ob- 
 
410 
 
 BAROMETERS. 
 
 Fig. 337. 
 
 Fig. 338. 
 
 servations. The easiest way of making such adjustment is by 
 the ivory float already described, the fiducial-edge in the notch 
 of which is to be made to correspond with a mark made on the 
 tube of the same distance from zero as the space between said 
 edge and the base of the float ; the most accurate way is by 
 means of a vertical ivory stiletto, gauged to a certain height on 
 the tube, and attached by a horizontal arm to a metal or ivory 
 collar clamped on the tube after the method of Fortin. 
 
 After this adjustment, made in either way, the column can be 
 read directly to inches and tenths, and lower by estimation. To 
 subdivide accurately and directly resort must be had to a vernier, 
 which may be a thin slip of pearl or ivory, or even paper, on 
 which a space of 0*9 inches, or nine divisions of the scale is, by 
 proportional compasses or by any other satisfactory method, 
 divided into ten equal parts. It is manifest that each one of 
 these parts is j^ of an inch shorter than the scale division ; 
 that if the zero of the vernier corre- 
 sponds with any scale-division, such 
 correspondence cannot occur again 
 until its tenth division ; and that 
 when the zero does not so correspond, 
 the number of the vernier division, 
 which coincides with some scale di- 
 vision, indicates the number of hun- 
 dredths by which the zero happens 
 to deviate and exceed the nearest 
 scale division below it. This will be 
 made plainer by reference to the 
 adjoining cuts, in which vernier and 
 scale are represented in the two po- 
 sitions respectively. In (1) the zero 
 of the vernier divisions is seen to co- 
 incide with 29-5 on the scale ; vern. 
 div. 1 is of course 0*01 in. short of 29*6 ; vern. div. 2 short by 
 0-02 in. of 29-7; vern. div. 3 short by 0-03 in. of 29-8; and so 
 on until vern. div. 9 is short by 0-09 in. of 30'3, and vern. div. 
 10 coincides with 304. Now if, as must be universally attended to, 
 the zero of the vernier is adjusted to the level of the mercury in 
 the tube, position (1) gives a reading for the height of the column 
 
BAROMETERS. 411 
 
 of 29-50 inches. In position (2) the vernier zero presupposed 
 to have been, in like manner, independently adjusted to the mer- 
 cury-level in the tube, does not happen to coincide with any scale 
 division, but lies rather more than midway between 29-5 and 29-6. 
 In order to see by how many hundredths exactly this zero or 
 mercury-level deviates from and transcends 29*5, the observer 
 looks along the scale until he finds a division there coincident 
 with some vernier division ; the number of said vernier division 
 is the number of hundredths in question. It is seen here that 
 division 6 of the vernier coincides with a division (it is immaterial 
 to count which) on the scale, and T 5 is therefore the space by 
 which vern. has passed 29-5, and the proper reading is 29-56 
 inches. If the student is not familiar with vernier reading, and 
 finds a difficulty or want of readiness yet remaining after this 
 attempted explanation, the best method for him is to draw the 
 two scales on separate pieces of paper, so as that one (the vernier) 
 may be applied to and shifted along the other. He cannot fail 
 after a few trials to catch the idea and the knack of this indis- 
 pensable adjunct, the vernier, in measuring spaces that are too 
 minute for direct graduation. 
 
 In the arrangement here given, the reading does not answer 
 for less than hundredths of an inch. Fortunately, a greater 
 minuteness is not requisite in any ordinary physical research ; and 
 if it were, there is room to question its attainability otherwise 
 than as a formal precision not a substantial accuracy. 
 
 A barometer, made and mounted as recommended, will give 
 better than most of the more elaborate instruments all the indi- 
 cations which are presumed to denote that the essential condi- 
 tions of a perfect apparatus have been satisfied. These indications 
 are principally the brilliance of the mercurial column, for the 
 observation of which the naked tube affords the utmost scope 
 possible ; a peculiar hammer or click made by the impact of the 
 mercury column against the sealed end when the instrument, pre- 
 viously stoppered by the pad or the gloved finger, is lifted out of 
 the cistern and gently inverted, which click cannot be produced 
 if there is any appreciable residual air in the space intended to 
 be vacuous ; the adherence of the mercury column to the sealed 
 end when the tube reverts to its erect position, and which some- 
 times requires a considerable concussion to be overcome ; the phe- 
 
412 BAROMETERS. 
 
 nomenon, in the dusk or dark, of luminous green flashes when, 
 the tube being normally suspended and caused to swing through 
 a small arc, the mercury column vibrates within, and electrically 
 excites the tube ; and finally, the manifestation in broad day- 
 light of electric attraction and repulsion, when to the tube so 
 swinging a gold-leaf electrometer is presented. By the preva- 
 lence of all these signs, the vacuum is judged to be more or less 
 perfect ; and when this condition of perfection is attained, all the 
 other details of arrangement are only matters of fancy, conveni- 
 ence, or conservatism. 
 
 This last item, to be sure, viz., the conservation of a vacuum 
 once attained is hardly less interesting than the original attain- 
 ment; and, unfortunately, the deterioration of tolerably good 
 barometers is more frequent, constant, and uniform, than the 
 occurrence of instruments of a higher class. This deterioration, 
 by whatever symptoms manifested, seems to be attributable alto- 
 gether to the action of the atmosphere, as well chemical as 
 mechanical. The first produces an oxidation of the metal in the 
 cistern (supposing the column entirely exempt from contact with 
 air) which does not fail, after a longer or shorter period, under 
 ordinary circumstances, to be propagated upwards in the tube ; 
 the second (under the same supposition) is always active in in- 
 sinuating minute portions of air, favored by every oscillation 
 of the column and the motion of the tube, downward along the 
 outside, and upward along the inside of the tube. If the assump- 
 tion of a perfect vacuum within does not hold in fact, of course 
 the operation, in the first mentioned mode, and possibly also in the 
 second, is proportionally facilitated. It was at one time supposed, 
 upon authority no less high than Davy himself, that atmospheric 
 air was always combined, as it were, vesicularly in every mass of 
 mercury, and that all attempts to expel it by heat or withdraw 
 it by exhaustion would be ineffectual; but the later experimental 
 researches of Daniell have shown that this supposition was an 
 error, and that the attraction between the mercury and the acci- 
 dentally contained air is not difficult to be, by proper means, 
 entirely overcome. The air, then, which deteriorates the vacuum 
 and spoils the column, creeps in from without ; and when it is 
 considered that there is no liquid contact between the metal and 
 the glass, no wetting of the latter by the former, one can 
 
BAROMETERS. 413 
 
 readily see that in the finite space which always thus occurs be- 
 tween the two surfaces at every point of the immersed part of the 
 tube there is ample room for air to insinuate itself between them, 
 and thus to leak into the tube. With respect to oxidations within 
 the tube, which manifest themselves by a loss of brilliance of the 
 column though its smoothness, is still maintained, they may, in 
 some cases, arise from a partial amalgamation with the lead used 
 in the composition of the glass. When there is opportunity for 
 this, the disorder is hopeless, and after it has reached a certain 
 point the barometer is no longer reliable, and the tube should be 
 rejected. But, with respect to leaks occurring round the open 
 end of the tube, the platinum guard spoken of under the Alexan- 
 der barometer, and whose suggestions arose with Mr. Daniell, 
 appears to present a full remedy. The amalgamation which 
 takes place with platinum is very slight and slow, the amal- 
 gam itself of great specific weight ; an air-tight liquid contact is 
 therefore effected along the whole width of the platinum strip, 
 and whatever amalgam may at any time be detached, tends to the 
 bottom of the cistern instead of ascending like the lead amalgam 
 to the surface. 
 
 The opinion just now referred to, of an indestructible combina- 
 tion between mercury and certain finite portions of air, had its 
 influence at the time upon the question of boiling the mercury in 
 the tube, as a means of obtaining a more complete and perma- 
 nent vacuum ; and those who objected to the boiling, on the score 
 of its undoubted trouble and risk, were all the more fortified in 
 their objections by the conviction of its inutility. But the re- 
 searches of Mr. Daniell have almost dispelled such convictions ; 
 while they have also brought to light an important advantage to 
 be derived from boiling, viz., in diminishing the correction that 
 has to be applied for what is technically called Capillarity. This 
 term, although not literally, is yet physically applicable as well to 
 barometer tubes of the largest ordinary bore as to those minutely 
 pierced stems, whose hair-like orifices are properly and strictly 
 to be named capillary, and the correction is necessary in both to 
 compensate for the effect arising from the relative attractions 
 reciprocal between the tube and the enclosed fluid, and existing 
 among the molecules of the fluid themselves. If the physical 
 sum of these attractions respectively be equal (or, to speak geo- 
 
414 . BAROMETRIC CORRECTIONS. 
 
 metrically and with more precision, if the intensity of the attrac- 
 tive force of the matter of the tube is half of that of the fluid) the 
 surface of the column will of course be plane and horizontal, 
 there being no force to solicit it towards any other form. If the 
 attraction of the tube be null or very small compared with that 
 of the fluid, the surface will be convex and nearly hemispherical, 
 its radius of curvature increasing with the tube-attractiveness, 
 while that of the fluid remains constant, until the former element 
 becomes equal to half the latter. From this epoch, which is that 
 of horizontally, if the tube-attractiveness goes on increasing, 
 the surface becomes proportionately concave, and attains hemi- 
 sphericity when the intensities of the respective forces are nume- 
 rically equal. Hence, with mercury, upon which glass exercises 
 little or no force of attraction, the surface of the column is convex, 
 and is depressed, or, as it were, repelled below its proper and 
 otherwise normal level. With water, on the other hand, oils and 
 all liquids which wet glass, the surface is concave, and is elevated 
 above said normal level. 
 
 As the attractions in question are not sensible through spaces 
 which are considerable, and, in point of fact, are inappreciable at 
 appreciable distances, their effect will be proportionate to the 
 diameter of the tube, and when that diameter surpasses (say) 
 0*75 inch it becomes insensible, and the correction unnecessary. 
 But, in any case, if the diameter be assumed uniform (for other- 
 wise there would be successions of varying equilibrium, stable and 
 unstable, in the tube) as well as the quantities of the respective 
 intensities, the amount of the correction is theoretically capable 
 of calculation, and, if suitable experimental data be substituted, 
 of numerical definition. Such definition is to be found in the 
 following table, founded on the formula of Laplace, and the ob- 
 servations of Gay-Lussac and Haiiy, calculated by Bouvard, and 
 here for the first time reduced and interpolated for English mea- 
 sures. 
 
 CORRECTIONS FOR CAPILLARY DEPRESSION IN BAROMETER TUBES. 
 
 TUBE. 
 Bore. Unboiled. Boiled. 
 
 In. In. In. 
 
 0-16 . . 0-080 0-040 
 
 0-18 . . 0-068 0-034 
 
 0-20 0-058 0-029 
 
 TUBE. 
 
 Bore. Unboiled. Boiled. 
 
 In. In. In. 
 
 022 . . 0-050 0-025 
 
 0-24 . . 0-044 0-0-22 
 
 0-2G 0-038 0-019 
 
BAROMETRIC CORRECTIONS. 
 
 415 
 
 Bore. 
 In. 
 
 0-28 
 
 0-30 
 0-32 
 0-34 
 0-36 
 0-38 
 0-40 
 0-42 
 0-44 
 
 
 TUBE. 
 
 
 Unboiled. 
 In. 
 0-034 
 
 Boiled. 
 In. 
 0-017 
 
 Bore. 
 In. 
 
 0-46 
 
 0-030 
 
 0-015 
 
 0-48 
 
 0-026 
 
 0-013 
 
 0-50 
 
 0-023 
 
 00115 
 
 0-52 
 
 0-020 
 
 o-oio 
 
 054 
 
 0-018 
 
 0-009 
 
 0-56 
 
 0-016 
 
 0-008 
 
 0-58 
 
 0-014 
 
 0-007 
 
 0-60 
 
 0-012 
 
 0-006 
 
 
 In. 
 
 0-011 
 
 TUBE. 
 Unboiled. Boiled. 
 
 In. 
 
 00055 
 0-010 0-005 
 
 0-009 
 0-008 
 0-007 
 0-006 
 00055 
 0-005 
 
 0-0045 
 
 0-004 
 
 0-004 
 
 0003 
 
 0003 
 
 0-003 
 
 The 3d and 6th columns of this table are in accordance with 
 Mr. Daniell's observations, which authorize us to conclude that 
 the effect of boiling in the tube is to augment the attraction of 
 the tube for the mercury (probably by causing a more intimate 
 contact), and thus to diminish the correction, as nearly as may 
 be, to one-half of what would be required in unboiled tubes. 
 These last columns, then, are what should be used in the labo- 
 ratory. 
 
 It is hardly necessary to say, that with a syphon-barometer a 
 correction of this kind is not applicable, provided the bore of the 
 two arms be the same. And it is as little proper here to discuss 
 a suggestion which readily follows what has been said, viz., that 
 with a cistern-barometer of the kind recommended just now, it 
 would not be difficult, under given conditions of bore and cistern- 
 diameter, to give such a weight to the float as to correct mecha- 
 nically the capillary depression, or, what is still easier, provided 
 the fact be noted on the instrument to make the corresponding 
 correction, either in the zero of the graduation or in the height 
 between the bore and the fiducial-edge of the float. 
 
 There is another correction which cannot, in the same or any 
 other way, be dispensed with or obviated, and which is necessary 
 to compensate the increased height and expansion of the mercu- 
 rial column by heat, in order, first, for any individual observation 
 to reduce the apparent reading to what it would have been had 
 there been no change in the volume of the mercury, and thus 
 show the height of column which at the normal specific gravity 
 equilibriated the atmosphere ; and secondly, to yield observations 
 which, whether at the same place, but at different temperatures, 
 or at different places either at the same or at different tempera- 
 
416- 
 
 BAROMETRIC CORRECTIONS. 
 
 tures, are thus made fairly comparable. This is best done by a 
 table like the following : 
 
 BAROMETRIC CORRECTIONS FOR TEMPERATURE. 
 
 Therm. 
 Fahr. 
 
 BAROMETRIC COLUMN. 
 
 28 in. 
 
 28-5 
 
 29 in. 
 
 29-5 
 
 30 in. 
 
 30-5 
 
 31 in. 
 
 31-5 
 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 In. 
 
 
 
 0-077 
 
 0-078 
 
 0-080 
 
 0-081 
 
 0-082 
 
 0084 
 
 0-085 
 
 0-086 
 
 5 
 
 0-065 
 
 066 
 
 067 
 
 068 
 
 069 
 
 071 
 
 072 
 
 073 
 
 10 
 
 053 
 
 054 
 
 055 
 
 056 
 
 057 
 
 058 
 
 058 
 
 059 
 
 15 
 
 041 
 
 042 
 
 042 
 
 043 
 
 044 
 
 044 
 
 045 
 
 046 
 
 20 
 
 029 
 
 029 
 
 030 
 
 030 
 
 031 
 
 031 
 
 032 
 
 032 
 
 25 
 
 017 
 
 017 
 
 017 
 
 018 
 
 018 
 
 018 
 
 019 
 
 019 
 
 30 
 
 + 0-005 
 
 0005 
 
 0-005 
 
 0-005 
 
 0-005 
 
 0005 
 
 0-005 
 
 0-005 
 
 35 
 
 0-007 
 
 0-007 
 
 0-007 
 
 0-008 
 
 0-008 
 
 0-008 
 
 0-008 
 
 0-008 
 
 40 
 
 019 
 
 020 
 
 020 
 
 020 
 
 021 
 
 021 
 
 021 
 
 022 
 
 45 
 
 031 
 
 032 
 
 032 
 
 033 
 
 033 
 
 034 
 
 035 
 
 035 
 
 50 
 
 043 
 
 044 
 
 045 
 
 046 
 
 046 
 
 047 
 
 048 
 
 049 
 
 55 
 
 055 
 
 056 
 
 057 
 
 058 
 
 059 
 
 060 
 
 061 
 
 062 
 
 60 
 
 067 
 
 068 
 
 *)70 
 
 071 
 
 072 
 
 073 
 
 074 
 
 076 
 
 65 
 
 079 
 
 081 
 
 082 
 
 083 
 
 085 
 
 086 
 
 088 
 
 089 
 
 70 
 
 091 
 
 093 
 
 094 
 
 096 
 
 098 
 
 099 
 
 101 
 
 103 
 
 75 
 
 103 
 
 105 
 
 107 
 
 109 
 
 111 
 
 112 
 
 114 
 
 116 
 
 80 
 
 115 
 
 117 
 
 119 
 
 121 
 
 123 
 
 126 
 
 128 
 
 130 
 
 85. 
 
 127 
 
 130 
 
 132 
 
 134 
 
 136 
 
 139 
 
 141 
 
 143 
 
 90 
 
 139 
 
 142 
 
 144 
 
 147 
 
 149 
 
 152 
 
 154 
 
 157 
 
 In constructing this table, the melting-point of ice, or 32 
 Fahr., has been taken as a standard of temperature to which the 
 observations are to be reduced. For all temperatures below 32 
 the corrections shown in the table are additive to the actual read- 
 ing ; for all above 32 they are sultr active. The temperatures 
 are given only from 5 to 5 ; for any required, it will be suffi- 
 cient to take proportional parts of the differences between the 
 two corresponding nearest corrections, above and below; for 
 which purpose it is that the quantities are expressed in thou- 
 sandths. Similar proportional parts maybe taken as between the 
 columns nearest above and below to the actual barometric reading; 
 but this is by no means necessary in ordinary cases. The quantities 
 in any column rule for any barometric stand, at or above the cap- 
 tion there, until it attains the next half inch in the adjoining one. 
 Thus, suppose it be required to correct a reading of the baro- 
 meter of 29-75 made at 68 F. Look in the col. of 29-5, the 
 nearest one below, where the corr. for 65 is seen as 0'083 in., 
 while that for 70 is 0-096 in., and the difference between the 
 
SOLUTION. 417 
 
 two quantities is 0-013 in., corresponding to 5. The propor- 
 tional parts, then, for 3 (the diff. between 65 and 68) will be 
 (I. 0-013 =) 0-004 ; and (0-083 + 0-004 =) 0-087 is thus found 
 for the tube correction, and (29-75 0-09 =) 29-66 the corrected 
 reading reduced to 32 F. If it be desired to have the reduction 
 for some other standard than 32, the table will still serve for 
 any case where very minute precision is not required, if used, as 
 it were, by double entry, that is, reducing at first to 32 by sub- 
 tracting, if the temperature is above, and vice versa; and then 
 raising that reduced temperature to the standard in question by 
 reversing the process. So, if it be required to reduce the read- 
 ing given just now to say 62 F., the process has already given 
 29-663 as at 32 ; the correction tabulated for 60 is 0-071, and 
 the proportional part for 2 is (f . 0-012 =) 0-005, making the 
 whole correction 0-076, which, added to 29-663, gives 29-74 as 
 the corrected reading for a temperature of 62. 
 
 CHAPTER XX. 
 
 SOLUTION. 
 
 WHEN a substance added to a liquid is wholly or partially 
 taken up by that liquid, it is said to be soluble therein. The 
 liquid employed is termed the solvent, and its combination with 
 the dissolved particles, a solution ; and if the liquid has exerted 
 its solvent power to the fullest extent, then the solution which it 
 forms is said to be saturated, because it can hold no more. 
 
 The variable degree of solubility in different liquids serves a 
 a distinctive characteristic of bodies, particularly those which are 
 solid. 
 
 Solution is either wholly mechanical, or else chemico-mecha- 
 nical. 1 In the first case, it is a molecular division of a body, or, 
 in other words, a diffusion of its particles in an appropriate liquid 
 without any alteration of its original properties, save as to form 
 
 1 Many chemists contend that " all solution is chemical union f and on this point 
 the reader is referred to a paper, by T. S. Hunt, in Silliman's Journal lor January, 
 
 1855. 
 
 27 
 
418 SOLUTION. 
 
 and cohesion. Thus, for example, an aqueous solution of sugar 
 or salt yields the whole of its charge by EVAPORATION, and one 
 of sulphate of lime by the addition of alcohol, in which it is in- 
 soluble. Ethereal or spirituous solutions deposit their dissolved 
 matter by DISTILLATION or CRYSTALLIZATION; and some other 
 kinds, that of gutta-percha in chloroform, for instance, by PRE- 
 CIPITATION with ether or alcohol. When the dissolved particles 
 are thus recoverable again in an unaltered state, chemically con- 
 sidered, their solution may be styled simple. 
 
 In the second case, chemico-mechanical solution, in contradis- 
 tinction to that which is purely mechanical, is a process requiring 
 the modification of a body by chemical action previous to its 
 solution. Thus, for example, copper, iron, or any other base or 
 acid, insoluble in the ordinary solvents, may be readily taken up 
 by liquid acids or bases. But the liquid holds in solution a newly 
 formed body entirely dissimilar to the original substance in pro- 
 perties, as appears when it is separated. In this, therefore, con- 
 sists the difference between a simple or mechanical and a chemico- 
 mechanical solution. As examples of this latter, iron may be 
 dissolved in dilute sulphuric acid, but in the act is transformed 
 into copperas ; alkalies are taken up by acids, but become 
 altered to salts ; and oil in being dissolved by potassa solution is 
 changed into soap. Hence it is that the chemical reaction is a 
 preliminary step requisite to promote simple solution. The point 
 of saturation in chemical solution is that at which the two bodies, 
 invariably of opposite properties, have combined in proportions 
 adequate to neutralization. 
 
 There are some exceptions to the above, which refer to certain 
 instances in which the acids and alkalies act as mere simple sol- 
 vents, and without changing the original properties of the dis- 
 solved substance. For example, acetic acid dissolves certain 
 phosphates and borates; aqua ammonite takes up carmine; 
 potassa water the hydrated peroxide of tin ; and hydro-sulphuret 
 of ammonia the deutosulphuret of iridium. 
 
 Solution is one of the most important processes in chemistry ; 
 it not only facilitates chemical reaction, but allows the separation 
 of soluble from insoluble bodies, or parts of the same ; and conse- 
 quently the purification of the solution by subsequent FILTRATION, 
 
 EVAPORATION, and CRYSTALLIZATION. 
 
SOLUTION. 419 
 
 As regards the power of dissolving the greatest number of 
 substances, water is the first in the rank of simple solvents, 
 alcohol the next, and ether third. Then follow spirits of turpen- 
 tine, pyroxylic spirit, the volatile and fixed oils, chloroform, ben- 
 zole, and a host of other liquids suitable to particular substances. 
 Of the alkalies, aqua ammonias or potassa are most used; the 
 former preferably, because of its volatility and that of most of 
 its salts. All of the common acids are employed, though some 
 few only are of general application : such as the muriatic, nitric, 
 sulphuric, acetic, and tartaric. 
 
 When the solubility of bodies is spoken of, it is in reference 
 usually to water, that being the standard liquid. In testing the 
 solubility of a substance, it is, therefore, usual to commence with 
 that liquid, and if it fails, to proceed with the next in order ; 
 and always, for reasons below given, trying the experiment at 
 varied temperatures, with gradually increased quantities if ne- 
 cessary. 
 
 A very convenient way of testing the solubility of a substance 
 is by means of a test-tube. If solid, a small portion in powder 
 is to be introduced and covered with distilled water, or the sol- 
 vent to be used, and repeatedly agitated by 
 the hand, the forefinger closing the mouth 
 (Fig. 339) to prevent the escape of particles. 
 If the matter is wholly soluble, there will be 
 no deposit at the bottom of the tube ; if par- 
 tially soluble, the substance will have decreased 
 in bulk ; if totally insoluble, it will occupy 
 the same space as at first. To determine as 
 to the two latter results, a minute portion of 
 the supernatant liquid is decanted and evapo- 
 rated in a small platinum spoon or strip of window-glass over the 
 spirit-lamp (Fig. 151) ; if a residue remains it indicates that mat- 
 ter has been taken up. 
 
 When heat is required, the lamp (as at Fig. 153) affords a 
 convenient means of application. The procedure in such cases 
 is the same as that above directed. 
 
 Volatile matters can in this way be recognized by their odor 
 emitted at boiling temperature, or else by the taste which they 
 impart to the liquid, or by some other characteristic test. 
 
420 MEANS OF FACILITATING SOLUTION. 
 
 The solubility of a solid body may be quantitatively determined 
 by measuring out a given volume of the solvent liquid, and adding 
 to it, while boiling, a weighed portion of the substance in ques- 
 tion. After the liquid has perfectly cooled, it is to be filtered 
 upon a counterpoised filter. The filter, on being perfectly dried 
 in vacuo and weighed, will give the insoluble residue, which, de- 
 ducted from the original weight, leaves figures that express the 
 soluble quantity. 
 
 The solubility of a gas may be ascertained by passing up a 
 given volume of water, or other fluid, the solvent power of which 
 is to be determined, into a graduated tube filled with mercury 
 and inverted, and then introducing similarly measured volumes of 
 the gas. When absorption ceases, by bringing the interior and 
 exterior levels nearly even, allowing for the small column of 
 water, the remaining gas subtracted from the whole amount in- 
 troduced will show how many volumes have been absorbed ; and 
 knowing the relative sp. gr. of the gas and water, the volumes 
 may be calculated to weights. 
 
 1. There are certain conditions which greatly facilitate the 
 solution of substances : 1st, comminution, which increases the 
 extent of surface ; 2d, agitation, which promotes the frequent 
 contact of all parts of the surface with fresh portions of solvents ; 
 3d, the freedom from impurity of both the solvent and body to 
 be dissolved ; 4th, it is also influenced by the quantity and state 
 of dilution of the solvent ; 5th, by the temperature ; 6th, by the 
 mode in which the process is conducted. 
 
 2. Agitation is effected by stirring with glass rods when the 
 containing vessel is open at the top. The rod should be rounded 
 at the end over the blowpipe flame, and to prevent its rolling 
 from the table or top of the vessel upon which it should be placed, 
 may be square instead of cylindrical as is usual. A very conve- 
 nient and effective mode of bringing all portions of the liquid 
 successively in contact with the substance to be dissolved, is to 
 place the latter in a cullendered diaphragm suspended beneath 
 the surface of the liquid. The first stratum of liquid in becoming 
 saturated increases its density, and consequently descends and 
 displaces a lower and fresher portion, which, being in the same 
 way surcharged in its turn, gives way to successive strata, and so 
 the operation continues until the whole of the matter, or so much 
 
SOLUTION OF SOLIDS. 421 
 
 as can be, is taken up. This mode keeps the substance in con- 
 stant contact with new portions of liquid, and is, in fact, a kind of 
 displacement process. 
 
 When flasks or bottles are used the same effect may be pro- 
 duced by repeated shaking. 
 
 TRITURATION in a mortar and alternate decantation and fresh 
 additions of the solvent greatly facilitate the solution of solid 
 substances. 
 
 3. The purity of the solvent is an important consideration, for 
 if it contain foreign matters, they may impart a dissolving power, 
 which is not inherent in the pure liquid, or diminish that already 
 possessed by it. Faraday makes the following excellent remarks 
 upon this subject. 
 
 "It is necessary that the student be on his guard respecting 
 certain variations in the solubility of bodies, arising from the pre- 
 sence of other matters. He will continually find that small 
 portions of substances generally considered as insoluble in water 
 will remain in neutral solutions when some other substance is 
 present, or because of slight mutual decomposition ; and he will 
 also frequently find that matter usually considered as readily 
 soluble, is so with difficulty when in contact with substances with 
 which it is not apparently in combination. Thus water boiled 
 upon muriate of potash and phosphate of baryta will be found to 
 contain more baryta than if boiled alone upon the phosphate ; 
 and, on the contrary, if oxide of iron and alumina be precipitated 
 together from a solution, it will be found much more difficult to 
 dissolve the alumina by solution of potash than if it had been 
 thrown down alone. 
 
 " The alkaline earths are remarkably soluble in solutions of 
 sugar, and also, though to a less degree, in solutions of extractive 
 and other vegetable matters ; hence they are retained in solution 
 at times in very unexpected situations, and might give rise to 
 much uncertainty in the appearances and characters of other 
 substances, unless the experimenter were aware of the general 
 fact. Platina is not itself soluble in nitric acid, even when 
 spongy and in its most comminuted form, but when alloyed in 
 small quantities with metals dissolved by that acid, it becomes 
 soluble with them, and in consequence appears now and then in 
 situations where it is not expected. Tartaric acid or tartrates 
 
422 INFLUENCE OF TEMPERATURE. 
 
 have an extraordinary power in rendering many metallic oxides 
 soluble, which are not so by other acids without it ; and still 
 more in holding them in solution when such substances are added 
 as in ordinary circumstances effect their separation. The oxides 
 of bismuth, antimony, tin, and titanium, are easily dissolved by 
 acids when tartaric acid is present ; and being present, ammonia 
 no longer has the power, upon its addition, of separating the 
 oxides of iron, titanium, manganese, cerium, cobalt, nickel, lead, 
 antimony, and the earths, alumina, magnesia, and yttria, from 
 their solutions, and in certain cases even potash or soda fails so 
 to do. Great advantage may be taken of this property occasion- 
 ally, but sometimes it is equally disadvantageous in preventing 
 the usual action of reagents." 1 
 
 4. In regard to the quantity and state of dilution of a solvent, 
 it must be remembered that some substances require more of it 
 than others for their solution, and that it should be in a greater 
 degree of dilution. Therefore, in examining the solubility of a 
 body always commence with small quantities, and increase both 
 quantity and strength gradually as may be required. 
 
 5. Temperature exerts a considerable influence in the solution 
 of bodies; and though in a few instances, as in the solution of 
 lime, magnesia, and anhydrous sulphate of soda in water, its 
 elevation impairs the power of the solvent, yet as an almost uni- 
 versal rule it facilitates its action. The temperature must be 
 adapted to the nature of the solvent and the substance to be dis- 
 solved, and of the solution formed. 
 
 It may be as well to mention that the caloric rendered latent 
 at the moment of the liquefaction of a solid, which is being dis- 
 solved in a liquid, causes a decrease of temperature. Solution 
 in volatile liquids should be in most cases performed in the cold, 
 and when of small quantities in narrow-necked flasks. 2 If heat 
 is required, especially when the vapors are inflammable, a retort 
 or covered still must be used ; and if the distillate is valuable, a 
 recipient may be annexed to receive as much as comes over. 
 
 * Annales de Chimie, xxiii, 356. 
 
 2 When weighed quantities are to be transferred to a flask or other narrow- 
 mouthed vessel, the use of a barrel will prevent liability of loss. Any particles 
 that may adhere to the side of the funnel can be washed down with portions of 
 solvent. 
 
SOLUTION OF LIQUIDS. 
 
 423 
 
 Fig. 340. 
 
 6. The mode of effecting solution varies with the substance 
 under process : MACERATION, DECOCTION, INFUSION, DIGESTION, 
 BOILING, and DISPLACEMENT, have each and all appropriate 
 application. 
 
 In ordinary solution the solid should be added in portions, and 
 a sufficient interval allowed for the solution of those in the liquid 
 before fresh are added. 
 
 The containing vessels should be those which resist the action 
 of heat, acid, alkalies, and corrosive liquids. 
 
 For solution in the cold, or at slightly warm temperatures, jars 
 of hard German glass, or beaker glasses, Fig. 
 340, are very appropriate vessels. The ma- 
 terial in powder is added to the fluid in the 
 jar, and contact of fresh surfaces promoted 
 by stirring with a glass rod. If the liquid 
 solvent is volatile, a glass-stoppered bottle is 
 a convenient substitute for the jar, agitation 
 being effected by shaking it to and fro. 
 
 Some volatile substances, which are inso- 
 luble in water under ordinary circumstances, 
 are taken up by it in the state of vapor. For this purpose both 
 should be distilled together. 
 
 When solutions, emitting corrosive or disagreeable fumes, are 
 being made in open vessels, the operation should be conducted 
 under a hood, the barrel of which connects with the chimney-flue 
 so as to insure their exit. 
 
 For making saturated solutions of most substances, EBULLI- 
 TION is necessary. For this purpose the solid must be boiled with 
 the solvent until the latter, on cooling, deposits some of its 
 charge. The cooled solution is then to be filtered. 
 
 Metals in their free state are dissolved one in the other by 
 FUSION. 
 
 Solution of Liquids. Agitation of the liquid to be dissolved 
 together with the solvent generally effects solution. If upon 
 repose there are two layers, then all the matter is not taken up, 
 and that portion which represents the solution must be separated, 
 and a fresh quantity of the solvent added. This process is to 
 be repeated until all, or as much as possible, of the liquid is 
 dissolved. 
 
424 SOLUTION OF GASES. 
 
 Solution of Gases. The generation and absorption of gases 
 are generally simultaneous processes, and have been fully treated 
 of at pp. 340-860. When water is used, it must be distilled and 
 boiled, to expel air. Viscid liquids are not less solvent than 
 others, but take up the gas much more slowly. As a general 
 rule, the capacity of a liquid for a gas is proportional to its rarity. 
 (Berzelius.) 
 
 Faraday succeeded (Ann. de Chim. et de Pliys. 3d Series, 
 Vol. 13, p. 121) in liquefying certain gases by the combined aid 
 of pressure and refrigeration, among them olefiant gas, fluosi- 
 licic and hydrochloric acids. Alcohol was partially solidified in 
 the same manner. Hydriodic, hydrobromic, and carbonic acids, 
 sulphuretted hydrogen, and ammonia, assumed well-defined solid 
 forms. 
 
 The author thus speaks for himself: "I sought, in the first 
 place, to obtain a very low temperature, and employed for this 
 purpose Thilorier's bath of solid carbonic acid and ether, placing 
 it, however, under the recipient of an air-pump. The bath vessel 
 was an earthenware dish of four cubic inches capacity, and fitted 
 to a somewhat larger dish, with several folds of dry flannel inter- 
 vening. The mixture lasted for an half hour. By maintaining 
 a constant vacuum, I lowered the temperature to such a degree, 
 that the carbonic acid of the bath was not more volatile than 
 water at the temperature of 86, for the barometer of the air- 
 pump stood at 28*2 inches, the external barometer being at 29-4. 
 
 " This arrangement made, I joined together, by means of corks 
 and stop-cocks, some small glass and copper tubes, so that, with 
 the aid of two pumps, I was able to subject various gases to a 
 pressure of 40 atmospheres, and, at the same time, to submit 
 them to the intense cold obtained under the air-pump, and to 
 examine the resulting effects. As I expected, the cold produced 
 several results which pressure alone would never have done, and 
 principally in the solidification of bodies ordinarily gaseous." 
 
 The two pumps, or condensing syringes, used by Faraday, 
 were fixed to a table, " the first having a piston of an inch dia- 
 meter, and the second one of only half that size ; and both were 
 so associated by a connecting-pipe that the first pipe forced the 
 gas into and through the valves of the second; and then the 
 
SOLUTION OF GASES. 425 
 
 second could be employed to throw forward this gas already con- 
 densed to ten or twenty atmospheres, into its final 
 recipient, the condensing-tube, at a much higher 
 pressure." 
 
 The condensing-tubes were of green bottle glass, 
 being one-sixth to one-fourth of an inch external dia- 
 meter, and from one-forty-second to' one-thirtieth of 
 an inch in thickness. They were of two kinds, about 
 nine and eleven inches in length ; one in form of an 
 inverted syphon, Fig. 341, having the bend cooled 
 by immersion in a cold bath ; and the other, hori- 
 zontal, Fig. 342, having a curve downward, near one 
 end, to be cooled in the same manner. Into the 
 longest leg of the syphon-tube, and the straight part of the hori- 
 zontal-tube, minute pressure-guages were introduced when re- 
 quired. The caps, stop-cocks, and connectors, were attached to 
 
 Fig. 342. 
 
 I 
 
 the tubes by common cement, and the screw joints made tight 
 by leaden washers." 
 
 The following table (from Gray's Pharmacopoeia) of the 
 solubility of some of the salts most in use will be found very 
 convenient. 
 
*''-. -4 
 
 426 
 
 SOLUBILITY OF SALTS. 
 
 THE SOLUBILITY OF SALTS. 
 
 
 Solubility in 100 parts Water 
 
 Solubility in 100 parts 
 
 Name of Salt. 
 
 
 Alcohol 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 ALUMINA. 
 
 
 
 Acetate of . 
 
 Undetermined. 
 
 
 Arseniate of 
 
 Insoluble. 
 
 
 Borate of 
 
 Uncrystallizable. 
 
 
 Camphorate of . 
 
 0-05. 
 
 
 Lactate of . 
 
 Uncrystallizable. 
 
 
 Muriate of 
 
 Very soluble 
 
 100 at 54 i. 
 
 Nitrfcte of . 
 
 Very soluble 
 
 ittW 100 
 
 Oxalate of 
 
 Uncrystallizable, 
 
 2-91 
 
 Phosphate of 
 
 Insoluble. 
 
 
 Seleniateof 
 
 Insoluble. 
 
 
 Sulphate of . 
 
 50. 
 
 
 Sulphate of, and Potash 
 
 5-4, . . 133-33 
 
 
 Sulphate of, and Soda 
 
 100. 
 
 
 Sulphite of * - 
 
 Insoluble. 
 
 
 Tartrate of . 
 
 Uncrystallizable, 
 
 2-91. 
 
 Tartrate of, and Potash 
 
 Uncrystallizable. 
 
 
 Tungstate of , 
 
 Insoluble. 
 
 
 Urate and Lithate of 
 
 Insoluble. 
 
 
 AMMONIA. 
 
 
 
 Acetate of . 
 
 Very soluble, 
 
 Readily soluble. 
 
 Arseniate of 
 
 Soluble. 
 
 
 Binarseniate of 
 
 Soluble. 
 
 
 Arsenite of 
 
 Uncrystallizable. 
 
 
 Benzoate of . 
 
 Soluble. 
 
 
 Boletate of 
 
 38. 
 
 
 
 8i, . ' . 
 
 . ir ?J $ .' 0-416 
 
 Camphorate of . 
 
 1, . < Lj! . 33 
 
 
 Carbonate of (Sesqui) 
 
 33 (Ure). 
 20 (Brands). 
 
 
 Chlorate of 
 
 Very soluble. 
 
 
 Chromate of 
 
 Very soluble. 
 
 
 Citrate of 
 Ferrocyanide of 
 
 Difficultly crystallizable. 
 Very soluble. 
 
 J 
 
 Formate of 
 
 Soluble. 
 
 
 Hydriodate of (or Iodide) 
 of Ammonium) . J 
 
 Very soluble. 
 
 
 Hydrocyanate of 
 
 Soluble. 
 
 
 Hydrosulphuret of 
 Hypophosphiie of . 
 
 Very deliquescent. 
 Soluble and deliquescent. 
 
 
 Hyposulphite of 
 
 Very soluble. 
 
 
 lodate of 
 
 Sparingly soluble. 
 
 
 Lactate of 
 Meconate of 
 
 Uncrystallizable. 
 66. 
 
 
 Molybdate of . 
 
 Soluble. 
 
 
 Muriate of (or Chloride of) 
 Ammonium . J 
 
 36, . . . 100 
 
 f ~ . 7 
 j 7'5 at 80 ( 2 " > '900 
 S 4-75 do. < > '87-2 
 
 
 
 1 1-5 do. ( ) '834 
 
 Nitrate of 
 
 50, . . 100 
 
 . . . 19-16 
 
 Oxalate of . 
 
 4-5 . . 40 84 
 
 
 Phosphate of . 
 
 25 (Brajide). 
 
 

 
 
 SOLUBILITY OF SALTS. 
 
 427 
 
 
 Solubility in 100 parts Water 
 
 Solubility in 100 parts 
 
 Name of Salt. 
 
 
 Alcohol 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 AMMONIA. 
 
 
 
 Biphosphate of 
 Phosphite of 
 
 Less soluble. 
 Very soluble. 
 
 
 Purpurate of 
 
 0066, much more. 
 
 
 Pyrolithate of . 
 
 Soluble. 
 
 
 Suberate of . 
 
 Very soluble. 
 
 . * i 
 
 Succinate of 
 
 Very soluble. 
 
 
 Sulphate of . 
 
 50 (Branded 100 
 
 
 Sulphite of 
 
 100 (Ure). 
 
 
 Tartrate of . 
 
 60-03 . . 304-7 
 
 2-91 
 
 Tungstate of 
 
 Soluble. 
 
 
 ANTIMONY. 
 
 
 
 Acetate of 
 
 Soluble. (Ure.) 
 
 
 Benzoate of . 
 
 Soluble. (Ure.) 
 
 
 Tartrate of 
 
 Very soluble. (Brands.) 
 
 
 Potassio-tartrate of . 
 
 7 . . .50 
 
 
 BISMUTH. 
 
 
 
 Acetate of . . 
 
 Soluble. 
 
 
 Arseniate of . . 
 
 Insoluble. 
 
 J 
 
 Benzoate of. 
 
 Soluble, 
 
 Sparingly. 
 
 Carbonate of, . 
 
 Insoluble. 
 
 
 Chloride of . 
 
 Deliquescent. 
 
 
 Nitrate of 
 
 Decomposed. 
 
 
 Phosphate of 
 Sulphate of 
 
 Soluble. 
 Decomposed. 
 
 
 BARYTA. 
 
 5 at 50, 10 at 212 
 
 
 Acetate of . 
 
 88, . . . % 
 
 
 Antimoniate of . 
 
 Insoluble. 
 
 
 Antimonite of 
 
 Slightly. 
 
 
 Arseniate of 
 
 Insoluble. 
 
 
 Arsenite of . 
 
 Difficultly. 
 
 
 Benzoate of 
 
 Soluble. 
 
 
 Borate of 
 
 Very sparingly. 
 
 
 Camphorate of . 
 Carbonate of 
 
 Very sparingly. 
 Very nearly insoluble. 
 
 
 Chlorate of 
 
 25. 
 
 
 Chromate of 
 Citrate of 
 
 Very sparingly. 
 Difficultly soluble. 
 
 
 Ferrocyanuret of 
 
 0005. . . '01 
 
 
 Hydriodate .of (or Iodide < 
 of Barium) . . | 
 
 Very soluble. 
 
 
 Hydrosulphuret of . 
 Hypophosphite of 
 
 11, . . - 50 
 Very soluble. 
 
 1 
 
 
 lodate of 
 
 33 . .16 
 
 
 Lactate of 
 
 Soluble. 
 
 
 Lithate of . 
 
 Insoluble. 
 
 r\ at 80 .1 g r -900 
 
 Muriate of (or Chloride of 
 
 Qfi.ft 68-5 
 
 (0*9 . aSjJ ; 848 
 
 Barium) (Anhydrous) 
 
 ou o * 
 
 \0-09 .' JOT I -8" 
 
 
 
 f 1 -56 at 80 C 1 9 
 
 
 
 0-43 . p 1 '848 
 
 Muriate of (or Chloride of 
 
 43 (Brande), . 78 
 
 <^ 0-32 . X 6 f '834 
 
 Barium) Cryst. . ; 
 
 
 0-06 . Lj' /2 J 
 
428 
 
 SOLUBILITY OF SALTS. 
 
 
 Solubility in 100 parts Water 
 
 Solubility in 100 parts 
 
 Name of Salt. 
 
 
 Alcohol 
 
 
 at 6j at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 BARYTA. 
 
 5 at 50 10 at 212 
 
 
 r~ ^ 
 Nitrate of . 
 
 $ 8- 18 at 58-9. 
 I 35-18 at 214-97. 
 
 
 Oxalate of 
 
 Nearly insoluble. 
 
 
 Phosphate of 
 
 Insoluble. 
 
 
 Phosphite of . 
 
 025. 
 
 
 Pyrocitrate of 
 
 066, . '02 
 
 
 Sulphate of 
 
 Insoluble. 
 
 
 Sulphite of . 
 
 Insoluble. 
 
 
 Tartrate of 
 
 Slightly. 
 
 
 COBALT. 
 
 
 
 Acetate of . 
 
 Soluble. 
 
 
 Antimoniate of . 
 
 Soluble. 
 
 
 Arseniate of 
 
 Insoluble. 
 
 
 Borate of 
 
 Scarcely. 
 
 
 Carbonate of 
 
 Insoluble. 
 
 
 Lactate of 
 
 026 (V re.) 
 
 
 Muriate, or Chloride of 
 
 Very soluble. 
 
 
 Nitrate of 
 
 Soluble, . 
 
 100 at 54 i. 
 
 Oxalate of . 
 
 Insoluble. 
 
 
 Sulphate of 
 
 4 (Brande), 
 
 Insoluble. 
 
 Tartrate of . 
 
 Soluble. 
 
 
 COPPER 
 
 
 
 Acetate of 
 
 (Ure), . 20 
 
 
 Antimoniate of 
 
 Insoluble. 
 
 
 Arseniate of 
 
 Insoluble. 
 
 -~'\ 
 
 Benzoate of. 
 
 Slightly. 
 
 
 Borate of 
 
 Insoluble. 
 
 
 Carbonate of 
 
 Insoluble. 
 
 
 Chlorate of 
 
 Soluble. 
 
 
 Chromate of 
 
 Insoluble. 
 
 
 Citrate of 
 
 Insoluble. 
 
 
 Ferrocyanide of, 
 
 Insoluble. 
 
 
 Fluoride of 
 
 Soluble. 
 
 
 Formate of , 
 
 12. 
 
 
 Hyposulphite of 
 Muriate, or Chloride of 
 
 Soluble. 
 Soluble, . 
 
 100 at 176. 
 
 Dichloride of 
 
 Nearly insoluble. 
 
 
 Nitrate of . 
 
 Deliquescent. 
 
 
 Oxalate of 
 
 Soluble? 
 
 
 and Ammonia . 
 
 Soluble? 
 
 
 and Potassa 
 
 Soluble ? 
 
 
 and Soda 
 
 Insoluble. 
 
 
 Phosphate of 
 
 Insoluble. 
 
 
 Subnitrate of 
 
 Insoluble. 
 
 - 
 
 Sulphate of 
 
 25, ... . 50 
 
 
 Disulphate of 
 
 Insoluble. 
 
 
 Trisulphate of . 
 
 Insoluble. 
 
 
 Sulphite of Protoxide, 
 Sulphate of, and Potassa 
 
 Insoluble. 
 Soluble. 
 
 
 and Ammonia 
 
 Soluble. 
 
 
 Ammonia Subsulphate 
 Tartrate of, . : j* .' 
 
 66-6. 
 Soluble. 
 
 
 Bitartrate of . 
 
 Less soluble. 
 
 
 Tartrate of, and Potassa 
 
 Soluble 
 
 t:' ' 
 
SOLUBILITY OF SALTS. 
 
 429 
 
 Name of Salt. 
 
 Solubility in 100 parts Water 
 
 Solubility in 100 parts 
 Alcohol 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 GOLD. 
 
 
 
 
 
 
 Perchloride of 
 
 Soluble. 
 
 
 Protochloride of 
 
 Soluble. 
 
 
 IRON. 
 
 
 
 Acetate (Prot.) 
 
 Soluble. 
 
 
 Acetate (Per.) . 
 
 Uncrystallizable. 
 
 
 Antimoniate of 
 
 Insoluble. 
 
 
 Arseniate of (Prot.) 
 
 Insoluble. , > 
 
 
 Arseniate of (Per.) . 
 
 Insoluble. 
 
 
 Benzoate of 
 
 Insoluble. 
 
 
 Borate of 
 
 Insoluble. 
 
 
 Citrate (Proto.) . 
 
 Soluble. 
 
 
 Citrate (Bi-proto.) . 
 Citrate (Per.) . 
 
 Sparingly soluble. 
 Very soluble and un-} 
 ( crystallizable. J 
 
 
 Ferrocyanide(PrussianBlue 
 
 Insoluble. 
 
 
 Fluoride of . 
 
 Insoluble. 
 
 . 
 
 Gallate of Peroxide of . 
 
 Insoluble. 
 
 
 Hyposulphite of 
 
 Soluble. 
 
 
 Lactate of Protox. of . 
 
 Scarcely. 
 
 
 Molybdate of Protox. of . 
 
 Insoluble. 
 
 
 Protochloride of 
 
 Soluble. 
 
 
 Perchloride of 
 Nitrate of Protoxide of 
 Nitrate of Peroxide of 
 
 Very soluble, . 
 Uncrystallizable. 
 Very soluble. 
 
 100 at 176. 
 
 Oxalate of Protoxide of 
 
 Soluble. 
 
 
 Oxalate of Peroxide of 
 
 Scarcely. 
 
 
 Phosphate of 
 
 Insoluble. 
 
 
 Phosphate of Peroxide of . 
 
 Nearly insoluble. 
 
 
 Superphosphate of 
 Succinate of Peroxide of . 
 
 Nearly insoluble. 
 Insoluble. 
 
 
 Sulphate of (Cryst.) 
 Sulphate of (dry) . 
 
 76-238 (Brande), 333'3 
 
 
 Persulphate of . 
 Hyposulphite of 
 
 Uncrystallizable, 
 Uncrystailizable. 
 
 Soluble. 
 
 Persulphate of and Potassa 
 
 Soluble. 
 
 
 Persulphate of and Am-) 
 monia . . . j 
 
 Soluble. 
 
 
 Tartrate (Proto.) of 
 
 0-25 (Dumas). 
 
 
 Tartrate (Per.) of 
 
 Soluble. 
 
 
 Tartrate of and Potassa 
 
 Uncrystallizable, 
 
 Soluble. 
 
 LEAD. 
 
 
 
 A. 
 
 
 
 Acetate (Cryst.) 
 
 27 (BostocJc), . 29 
 
 12'5. (Brande.) 
 
 Acetate (Anhyd.) . 
 Diacetate of 
 
 Soluble.' 
 
 Soluble. 
 
 Antimoniate of 
 
 Insoluble. 
 
 
 Arseniate of 
 
 Insoluble. 
 
 
 Benzoate of 
 
 Insoluble. 
 
 
 Borate of 
 
 Insoluble. 
 
 
 Carbonate of 
 
 Insoluble. 
 
 
 Citrate of 
 
 Nearly insoluble. 
 
 
 Chlorate of . 
 
 Soluble. 
 
 
 Chloride of 
 
 3-33 (Brande), . 4'5 
 
 
 Chloride of (fused). 
 
 
 
 Chromate of 
 
 Insoluble. 
 
 
 Ferrocyanuret of . 
 
 Insoluble. 
 
 
 Gallate of 
 
 Insoluble. 
 
 
 Iodide of 
 
 0-08 . . .0-5 
 
 
 Hyposulphite of 
 
 Soluble. 
 
 
430 
 
 SOLUBILITY OF SALTS. 
 
 
 Solubility in 100 parts Water 
 
 Solubility in 100 parts 
 
 Name of Salt. 
 
 j. 
 
 Alcohol 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 LEAD. 
 
 
 
 Lactate of . 
 
 Soluble. (Ure.) 
 
 
 Superlactate of . 
 
 Soluble. 
 
 
 Malate of 
 
 Scarcely. 
 
 
 Molybdate of . 
 
 Insoluble. 
 
 
 Nitrate of . 
 
 13. 
 
 
 Dinitrate of 
 
 ( Scarcely at 60, but much 
 ( more so at 212. 
 
 
 Oxalateof . 
 
 Insoluble. 
 
 
 Phosphate of 
 
 Insoluble. 
 
 
 Phosphite of 
 Succinate of 
 
 Insoluble. 
 Insoluble. 
 
 
 Sulphate of . 
 Sulphite of 
 
 Not absolutely insoluble. 
 Insoluble. 
 
 
 Tannate of . . . 
 
 Insoluble. 
 
 
 Tartrate of 
 
 Almost insoluble. 
 
 
 and Potassa 
 
 Insoluble. (Berzelius.) 
 
 
 LIME. 
 
 (Kirwan.) 
 
 
 
 
 f2'4 at80fo ."| -900 
 
 Acetate of . 
 
 Soluble, . . ,? ; 
 
 J 4-12 . J f I '848 
 
 
 
 } 4-75 . r\ * f -834 
 
 
 
 (jl-88 . . L2 J '817 
 
 Antimoniateof . 
 
 Insoluble. 
 
 
 Arseniate of 
 
 Insoluble. 
 
 
 Arsenite of 
 
 Difficultly soluble. 
 
 
 Benzoateof. 
 
 Sparingly soluble. 
 
 
 Borate of 
 
 Very difficultly. 
 
 
 Carbonate of (Anhyd.) 
 Chlorate of 
 
 Insoluble. 
 Very soluble, . 
 
 Soluble. 
 
 Chromateof 
 
 Soluble. 
 
 
 Citrate of 
 
 Nearly insoluble. 
 
 
 Fluoride of ... 
 
 Insoluble. 
 
 
 Hypophosphite of 
 
 (Solubility nearly equal 
 ( at ail temperatures. 
 
 
 Hyposulphate of 
 
 40-65. (Brande.) 150 
 
 
 Hyposulphite of 
 
 Very soluble. 
 
 
 lodate of 
 
 20, . . . 100 
 
 
 Iodide of Calcium 
 
 Deliquescent. 
 
 
 Malate of . 
 
 66, . .1-53 
 
 
 Molybdate of . 
 
 Insoluble. 
 
 .''; 
 
 
 f200 at 32. 
 
 
 Muriate (or Chloride of) 
 
 J 400 at 60. 
 
 
 Calcium) . . j 
 
 1 almost any quantity at 
 
 
 
 220. 
 
 
 Nitrate of . 
 
 25, . N|J 
 
 . 161-66 
 
 Oxalate of . . 
 
 Insoluble. 
 
 
 Phosphate of 
 
 Insoluble. 
 
 
 Biphosphate of . 
 
 Soluble. 
 
 
 Subphosphate of 
 
 Almost insoluble. 
 
 
 Succinate of 
 
 Difficultly soluble. 
 
 
 Sulphate of . 
 
 0-301 at 50. 
 
 
 Sulphite of 
 
 12-5. 
 
 
 Tartrate of . 
 
 5 Nearly insoluble at 60, 
 ( but -16 at 212. 
 
 
 Tungstate of . 
 
 Insoluble. 
 
 
 LITHIA. 
 
 
 
 Acetate of . 
 Bicarbonate of . . 
 
 Deliquescent. 
 Slightly soluble. 
 
 . 
 
SOLUBILITY OF SALTS. 
 
 431 
 
 Name of Salt. 
 
 Solubility in 100 parts Water 
 
 Solubiliiy in 100 parts 
 Alcohol 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point? 
 
 LITHIA. 
 
 
 
 Borate of 
 
 Soluble. 
 
 
 Carbonate of 
 
 1, ... 
 
 Insoluble. 
 
 Chloride of Lithium 
 
 Very deliquescent. 
 
 
 Chromate of 
 
 Very soluble. 
 
 
 Citrate of . 
 Nitrate of . 
 Oxalate of . 
 
 Very difficultly soluble. 
 Very deliquescent. 
 Very deliquescent. 
 
 
 Binoxalate of . 
 
 Less soluble. 
 
 
 Phosphate of 
 
 Insoluble. 
 
 
 Sulphate of 
 
 Soluble. 
 
 
 Tartrate of . 
 
 Easily soluble. 
 
 
 and Potassa. 
 
 Easily soluble. 
 
 
 and Soda 
 
 Easily soluble. 
 
 
 MAGNESIA. 
 
 
 
 Acetate of 
 
 Very soluble. 
 
 
 Arseniate of 
 
 Deliquescent. 
 
 
 Arsenite of 
 Benzoate of . 
 
 Difficultly soluble. 
 Soluble. 
 
 
 Borate of 
 
 Insoluble. 
 
 
 Carbonate of 
 
 Very slightly. 
 
 
 Chlorate of 
 
 Very soluble. 
 
 
 
 
 f50, . . 547 
 
 Chloride of Magnesium 
 
 200 (Brande), . 
 
 1 50 at 80 ( Sp. gr. ) .817 
 1 < of > 
 1 21 25 ( Spts. ) -900 
 
 Chromate of 
 
 Very soluble. 
 
 
 Citrate of . 
 
 Difficultly soluble. 
 
 
 Iodide of Magnesium 
 
 Soluble. 
 
 
 Malate of 
 
 3'6 (Brande). 
 
 
 Molybdateof 
 
 6-66 . . 8-35 
 
 ( Nearly insoluble in pure 
 
 Nitrate of 
 
 100, 
 
 ^ alcohol. 
 
 
 
 (11 sp.gr. -840. 
 
 Oxalate of . 
 
 Nearly insoluble. 
 
 
 Phosphate of 
 
 6-66. 
 
 
 and Ammonia 
 Suceinate of 
 
 Sparingly soluble. 
 Uncrystallizable. 
 
 
 Sulphate of (dry) . 
 Sulphate of (cryst.) 
 
 33-192, . . 73-57 
 68-042, . . 15071 
 
 1 at 80. (Kirwan.) 
 
 and Ammonia . 
 
 Soluble. 
 
 
 and Potassa 
 
 Soluble. 
 
 
 and Soda 
 
 33-3. 
 
 
 Sulphite of 
 and Ammonia . 
 
 5. 
 Difficultly soluble. 
 
 
 Tartrate of 
 
 Insoluble. 
 
 
 Tungstate of 
 
 Soluble. 
 
 
 MANGANESE. 
 
 
 
 .A. 
 
 
 
 Acetate of 
 
 3, ... 
 
 Soluble. 
 
 Ammonio-chloride of 
 
 Soluble. 
 
 
 Ammonio-sulphate of . 
 Antimoniate of 
 
 Soluble. 
 Moderately soluble. 
 
 
 Arseniate of . 
 
 Insoluble. 
 
 
 Benzoate of . 
 
 Deliquescent (Brande). 
 
 
 Carbonate of . . 
 
 Insoluble. 
 
 
 Chromate of 
 Nitrate of 
 
 Soluble. 
 Very soluble, 
 
 Soluble. 
 
 Oxalate of . . 
 
 Insoluble. 
 
 
432 
 
 SOLUBILITY OF SALTS. 
 
 
 Solubility in 100 parts Water 
 
 Solubility in 100 parts 
 
 Name of Salt. 
 
 A 
 
 Alcohol 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 MANGANESE. 
 
 
 
 Phosphate of . 
 Succinate of V 
 
 Nearly insoluble. 
 1. (Ure.) 
 
 
 Sulphate of 
 
 31. (Ure.) 
 
 
 
 50. (Brande.) 
 
 
 Hyposulphate of 
 Sulphite of 
 Tungstate of 
 
 Deliquescent. 
 Insoluble. 
 Insoluble. 
 
 
 MERCURY. 
 J^ 
 
 
 
 Acetate of (Prot.) 
 
 016. (Braconnot.) 
 
 
 Acetate of (Per.) . 
 
 Readily soluble. 
 
 
 Arseniate of 
 
 Insoluble. 
 
 
 Benzoate of . 
 
 Insoluble. 
 
 
 Borate of 
 
 Insoluble. 
 
 
 Bichloride of 
 
 6'25 (Brande), 33'3 
 
 42-6, . . 85-2 
 
 
 
 C 10-74 at 50. 
 
 
 
 J Sprts. sp. gr. -915. 
 
 
 
 \ 43-66 at 50. 
 (JSprts. sp. gr. -818. 
 
 Chloride of 
 
 00833 at 212 (Dumas). 
 
 (Graham.) 
 
 Chromate of . . 
 
 Insoluble. 
 
 
 Citrate of 
 
 Insoluble. 
 
 ( > 
 
 Bicyanuret of . -^ 
 
 54 
 
 , 
 
 Fluoride of 
 
 Soluble. 
 
 
 Molybdate of 
 Nitrate (Prot.) . 
 
 Very sparingly. 
 (Soluble and decomposed 
 ( by excess. 
 
 
 Nitrate of (Per.) . 
 
 Do. do. 
 
 
 Oxalate of (Proto.) 
 
 Scarcely. 
 
 
 Oxakteof(Per.) . 
 
 Insoluble. 
 
 
 Sulphate of (Proto.) 
 
 0'20 . . 0'33 
 
 
 Sulphate of (Per.) . 
 
 Decomposed. 
 
 
 Sulphate of (Sub.) " . , 
 
 005 . . 0-33 
 
 
 Tartrate of . 
 
 Insoluble. 
 
 
 and Potassa. 
 
 Soluble. 
 
 
 NICKEL. 
 
 
 
 Acetate of . 
 
 Very soluble. 
 
 
 Arseniate of 
 
 Soluble. (Ure.) 
 
 
 Carbonate of 
 
 Insoluble. 
 
 
 Chloride of 
 
 Soluble in hot water. 
 
 
 Nitrate of Protox. . 
 
 50, ... 
 
 Soluble. 
 
 and Ammonia 
 
 Soluble. 
 
 
 Oxalate of 
 
 Insoluble. 
 
 
 Phosphate of 
 
 Nearly insoluble. 
 
 
 Sulphate of 
 
 33-3, . . 185-71 
 
 
 and Ammonia . 
 
 25. 
 
 
 and Potassa 
 
 11 1. 
 
 
 and Iron 
 
 Soluble.. 
 
 
 Tartrate of . i" 
 
 Very soluble. 
 
 
 PLATINUM. 
 
 
 
 Protochloride ut . ( , 
 
 Soluble, . . ( 
 
 (Easily soluble, also in 
 
 Perchlunue of . , j 
 
 Soluble, . . I 
 
 I Ether. 
 
 Protochloride of . ', 
 and Ammonium i 
 
 Soluble, . , . 
 
 Insoluble. 
 
 and Potassium . 
 
 Soluble, 
 
 Insoluble. 
 
 and Sodium . 
 
 Uncrystallizable, 
 
 Very soluble. 
 
SOLUBILITY OF SALTS. 
 
 433 
 
 
 Solubility in 100 parts Water 
 
 Solubility in 100 parts 
 
 Name of Salt. 
 
 A 
 
 Alcohol 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 PLATINUM. 
 
 
 
 Bichloride of . ) 
 and Ammonium J 
 
 Very sparingly. 
 
 
 and Potassium . 
 
 Very sparingly. 
 
 
 and Sodium . 
 
 Soluble,. 
 
 - Soluble. 
 
 and Barium 
 
 Soluble. 
 
 
 Protonitrate of . 
 
 Soluble. 
 
 
 Pernitrate of 
 
 Soluble. 
 
 
 Protosulphate of 
 
 Soluble. 
 
 
 Persulphate of 
 
 Very soluble, . 
 
 (Very soluble, also in 
 I Ether. 
 
 POTASSA. 
 
 
 
 
 100, 
 
 200 
 
 Ammonia-oxalate of . 
 
 Soluble. 
 
 
 Ammonia-sulphate of 
 
 13. 
 
 
 Ammonia-tartrate of . 
 
 Very soluble. 
 
 
 Antimoniate of 
 
 Slightly. 
 
 
 Antimonite of . 
 
 Soluble. 
 
 
 Arseniate of 
 Binarseniate of . 
 
 Uncrystalli/able, 
 18-86 at 40, 
 
 3-75. 
 Insoluble. 
 
 Arsenite of . 
 
 Uncrystallizable. 
 
 
 Benzoate of 
 
 Very soluble. 
 
 
 Bibenzoate of 
 
 10. 
 
 
 Borate of 
 
 Soluble. 
 
 
 Camphorate of 
 
 1, . . .25 
 
 
 Carbonate of 
 
 100. 
 
 
 Bicarbonate of 
 
 25, . . . 83 
 
 
 Chlorate of 
 
 6-03, 60 at 1881 
 
 
 Chromate 
 
 48, . . extremely. 
 
 Insoluble. 
 
 Bichromate of . 
 
 10, . much more. 
 
 
 Citrate of 
 
 Very soluble. 
 
 
 Columbate of . 
 
 Uncrystallizable. 
 
 
 Ferrocyanide of 
 
 33-3, . . 100 
 
 ' 
 
 Iodide of Potassium 
 
 143 at 65 (G. Lussac]. 
 
 Sparingly. 
 
 lodate of 
 
 7-14 (Brande). 
 
 
 Molybdate of . 
 
 Soluble. 
 
 
 
 
 
 f2'083 '_ 
 
 Chloride of Potassium 
 t 
 
 (29-21 at 66-83) 
 1 59-26 at 229-28 \ 
 
 ) 4-62 at 80 ( o ) -900 
 1 1-66 . . < &? >812 
 
 
 
 LO'38 . . (CC M ) '834 
 
 
 ( 29-31 at 64) 
 
 
 Nitrate of 
 
 ) 236 45 at 207 > 
 (285- at 238) 
 
 2-083 
 
 Oxalate of . 
 
 (50 (Ure). . I 
 )30 (Brande), . ) 
 
 (2-76 at 80 Sp.gr. '900 
 1 1 . of Sprts. '872 
 
 Binoxalate of . 
 
 (10 Brande.) (UrelOO.) 
 
 
 Quadroxalate of 
 Phosphate of . . 
 
 66-66 
 Difficultly soluble. 
 
 -^ 2'91 
 
 Diphosphate of 
 
 Soluble in hot water. 
 
 
 Biphosphate of . 
 Hypophosphite of . 
 
 Hyposulphate of 
 
 Very soluble. 
 Very deliquescent, 
 (Difficultly soluble at 60, 
 \ readily at 212. 
 
 Very soluble. 
 
 Hyposulphite of 
 and Silver 
 
 Deliquescent. 
 Difficultly. 
 
 
 Succinate of 
 
 Very soluble. 
 
 
 Sulphate of 
 
 (10-57 at 54. 
 J2633at2l4 . 
 
 
 Bisulphate of 
 
 ( 50 at 40. 
 1 200 at 220. 
 
 
 
 28 
 
 
434 
 
 SOLUBILITY OF SALTS. 
 
 
 Solubility in 100 parts Water 
 
 Solubility in 100 parts 
 
 Name of Salt. 
 
 A 
 
 Alcohol 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 POTASSA. 
 
 
 
 Sulphite of 
 
 100. 
 
 
 Tartrate of . 
 
 100, 
 
 0-416 
 
 Bitartrate of 
 
 1-05, . . 6-66 
 
 2-91 
 
 Tartrovinate of 
 
 10, . any quantity. 
 
 . 
 
 Tungstate of 
 Nitro-tungstate of . 
 
 Uncrystallizable. 
 (ZTre), 5 
 
 . 
 
 SILVER. 
 
 
 
 Acetate of . 
 
 Very difficultly soluble. 
 
 ' 
 
 Arseniate of 
 
 Insoluble. 
 
 
 Arsenite of . 
 
 Insoluble. 
 
 
 Borate of 
 
 Difficultly soluble. 
 
 
 Chlorate of . 
 
 25 (Chenemx). 
 
 
 Chromate of 
 
 Very slightly. 
 
 
 Citrate of . 
 
 Insoluble. 
 
 
 Molybdate of . 
 
 Insoluble. 
 
 
 Chloride of (Fused) 
 
 Insoluble. 
 
 
 Nitrate of (Cryst.) 
 
 100, . . 200 
 
 25 
 
 Oxalate of . 
 
 Insoluble. 
 
 
 Phosphate of . 
 
 Insoluble. 
 
 
 Succinate of 
 
 Soluble. 
 
 
 Sulphate of 
 
 1-15. 
 
 
 Sulphite of . 
 
 Very little soluble. 
 
 
 Hyposulphite of 
 and Potassa 
 Tartrate of 
 
 Soluble. 
 Difficultly soluble. 
 Soluble. 
 
 
 and Potassa 
 
 Soluble. 
 
 
 SODA. 
 
 
 
 Acetate of . 
 
 35, . . 150 
 
 
 Arseniate of 
 
 (10 (Thompson). 
 {25 (lire-). 
 
 
 Binarseniate of 
 
 Soluble. 
 
 
 and Potassa 
 
 Soluble. 
 
 
 Benzoate of . 
 
 Very soluble. 
 
 
 Biborate of 
 
 8-033, . . 50 
 
 
 Carbonate of 
 
 50, . . 100 
 
 
 Bicarbonate of . 
 
 7-6. 
 
 
 Chlorate of . 
 
 33-3, . 
 
 Sol. in sp. rect. 
 
 Chromate of 
 
 Very soluble, 
 
 Sparingly. 
 
 Citrate of . 
 
 100 or more (Brande). 
 
 
 Iodide of Sodium 
 
 173. 
 
 
 lodate of 
 
 7'3, 
 
 Insoluble. 
 
 Molybdate of . 
 Muriate of (or Chloride of ) 
 Sodium, . . 5 
 
 Soluble. 
 Equally soluble at all) 
 temperatures. (Berz.'i) 
 C 33-3 at 60) n 
 
 (5 -8 at 80 (Sp.gr.) '900 
 { 3'6 . . < of > -872 
 {0'5 . . ( Spts. J -834 
 
 
 100 at 123} Duma *' 
 
 
 
 50 af 60 Berzel. 
 
 C '958 
 
 Nitrate of . 
 
 73 at 32) (Gay 
 < 173 at 212j Lussac). 
 80 at 32 1 
 
 j 10-5 at 80 (Sp.gr.) -900 
 1 6 . . . < Of > '872 
 
 LO-38 . . ( Spts. ) -834 
 
 
 22-7 at 50 i ^ 
 
 
 
 55 at 61 f marx ' 
 
 
 
 J218-5 at 246J 
 
 
 Oxalate of . . .... 
 Phosphate of 
 
 Sparingly soluble. 
 25, . . 50 
 
 
 and Ammonia 
 
 Soluble. 
 
 
 Biphosphate of J . 
 
 Very soluble. 
 
 
 
SOLUBILITY OF SALTS. 
 
 435 
 
 Name of Salt. 
 
 Solubility in 100 parts Water 
 
 Solubility i n 100 parts 
 Alcohol 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 SODA. 
 
 
 
 Hypophosphite of 
 Succinate of 
 
 Very soluble, . 
 Soluble. 
 
 Very soluble. 
 
 Sulphate of (Cryst.) 
 
 C 48-28 at 64. 
 1 322- 12 at 91. 
 
 
 
 ( 16-73 at 64) , n 
 
 
 Sulphate of (dry) . 
 
 Hyposulphate of 
 Bisulphate of 
 
 < 50*65 at 91 > ^ a y 
 (42 -65 at 2 17) Lussac} ' 
 41-6, . . 91 
 50. 
 
 Insoluble. 
 Insoluble. 
 
 Sulphate of, and Ammonia 
 
 Soluble. 
 
 
 Sulphite of . 
 Hyposulphite of 
 Tartrate of . 
 
 25. 
 Deliquescent. . 
 56-37 (Thomson), 
 
 Insoluble. 
 Insoluble. 
 
 and Potassa". 
 
 20. 
 
 
 
 
 'Sol. in sp. rect., but 
 
 Tartrovinate of 
 
 Soluble, . 
 
 sparingly in absolute 
 
 
 
 [ alcohol. 
 
 Tungstate of 
 
 25, . . 50 
 
 
 STRONTIA. 
 
 < 0-625 at 60) (U } 
 
 
 ^/^ 
 
 1*1 Rt 212o ( v^re;. 
 
 
 Hydrate of . 
 Acetate of 
 Arseniate of 
 Arsenite of 
 
 2* . 50 
 Very soluble. 
 Sparingly soluble. 
 Sparingly soluble. 
 
 
 Borate of 
 
 0-76. 
 
 
 Carbonate of 
 
 0-0651 at 212. 
 
 
 Chlorate of 
 
 Very soluble. . 
 
 Soluble. 
 
 Chloride of Strontium . 
 
 50, 
 
 Soluble. 
 
 Chromate of 
 
 Insoluble (Brande). 
 
 
 Citrate of 
 
 Soluble. 
 
 
 Ferrocyanuret of . 
 Iodide of Strontium 
 
 25. 
 
 Soluble. 
 
 
 lodate of 
 
 25. 
 
 
 Nitrate of 
 
 113 
 
 
 Oxalate of . 
 
 0-52 
 
 
 Phosphate of . 
 
 Insoluble. 
 
 
 Phosphite of 
 Hypophosphite of 
 
 Soluble. 
 Very soluble. 
 
 
 Succinate of . . 
 
 Soluble. 
 
 
 Sulphate of 
 Hyposulphite of 
 
 0-026 at 212. 
 20 (Gay Lussac), 
 
 Insoluble. 
 
 Hyposulphate of 
 Tartrate of . 
 
 22-22 . 66 ' 66 
 0-67 at 170o. 
 
 
 TIN. 
 
 
 
 Acetate of 
 
 Soluble. 
 
 
 Arseniate of 
 
 Insoluble. 
 
 
 Borate of 
 Nitrate Proto. of . 
 
 Insoluble. 
 Uncrystallizable. 
 
 
 Nitrate Per. of . 
 
 Scarcely. 
 
 
 Oxalate of . 
 
 Soluble. 
 
 
 Phosphate of . 
 Succinate of 
 Sulphate Proto. of 
 Sulphate Per. of 
 Tartrate of . 
 and Potassa 
 
 Insoluble. 
 Soluble. 
 Crystallizable. 
 Uncrystallizable. 
 Soluble. 
 Very soluble. 
 
 
436 
 
 SOLUBILITY OF SALTS. 
 
 
 Solubility in 100 parts Water 
 
 Solubility in 100 parts 
 
 
 
 Alcohol 
 
 Name of Salt. 
 
 vv 
 
 
 
 at 60 at Boiling-point. 
 
 at 60 at Boiling-point. 
 
 ZINC. 
 
 
 
 w 
 
 
 
 Acetate of 
 
 Very soluble. 
 
 
 Antimoniate of 
 
 Very sparingly. 
 
 
 Borate of 
 
 Insoluble. 
 
 
 Chromate of 
 Citrate of 
 
 Sparingly. 
 Scarcely. 
 
 
 Chlorate of . 
 Chloride of 
 
 Very soluble. 
 Very soluble. . 
 
 100 at 54i. 
 
 Iodide of 
 
 Soluble. 
 
 
 lodate of 
 
 Difficultly soluble. 
 
 
 Lactate of . 
 
 2 (Ure). 
 
 
 Nitrate of 
 
 Deliquescent. 
 
 
 Molybdateof 
 
 Insoluble. 
 
 
 Oxalate of 
 
 Nearly insoluble. 
 
 
 Phosphate of 
 Succinate of 
 
 Uncrystallizable. 
 Soluble. 
 
 
 Sulphate of . 
 
 140 (Dumas). 
 
 
 Sulphite of 
 
 81-81 at 220, . 
 
 Insoluble. 
 
 Hyposulphite of 
 Sulphate of, and Nickel 
 Tartrate of . 
 
 Soluble, . 
 33-33. 
 Difficultly soluble. 
 
 Soluble. 
 
 Tartrovinate of . 
 Trisulphate of 
 
 Soluble, . 
 Soluble. 
 
 Sparingly soluble. 
 
 ACID. 
 
 
 
 Arsenious 
 
 
 
 Vitreous 
 
 1-78 (Graham), 9'68 
 
 
 Opaque 
 
 2'9 (Graham), 11 '47 
 
 
 Benzoic 
 
 50. 
 
 
 Boracic . . . 
 
 3-9, . v 33-3 
 
 20 at 176 (Henry). 
 
 Citric 
 
 13333, . . 200 
 
 Soluble. 
 
 Gallic . 
 
 5, . . 33-33 
 
 
 Oxalic (Cryst.) 
 
 11-5. 
 
 
 Succinate (Cryst.) 
 
 4, . . 33-33 
 
 74 at 176. 
 
 Tartaric 
 
 150 (Brande), 200 
 
 Soluble. 
 
 Brucia 
 
 1177, . . 0-2 
 
 Soluble. 
 
 Cinchonia . 
 Morphia 
 Quinia 
 
 Insoluble, . 0'04 
 Nearly insoluble, 1 
 Nearly insoluble, 0'5 
 
 Partially soluble. 
 Very soluble. 
 
 Strychnia 
 
 0'04 (Graham), 0'15 
 
 $ 5' sp. gr. of spts. 870 
 I (Duflos). 
 
 Camphor 
 
 0229, . 
 
 75 at 176. 
 
 Cane Sugar 
 
 200. 
 
 
MACERATION. INFUSION. 437 
 
 CHAPTER XXI. 
 
 MACERATION INFUSION DECOCTION DIGESTION BOILING 
 DISPLACEMENT. 
 
 MACERATION. The soaking or steeping of a substance in a 
 liquid, at the ordinary temperature, is termed maceration. It is 
 almost exclusively applicable to organic substances, being most 
 frequently resorted to as a means of hastening and facilitating 
 the after-solution of the extractive parts of hard, compact, or 
 impervious wood, roots, stems, and leaves, by the more active 
 methods of DISPLACEMENT or of EBULLITION. It is employed 
 when the soluble principles are alterable by heat ; and is also 
 made use of to effect the solution of a substance containing 
 several principles, the solubility of which varies with the tempe- 
 rature applied, as it leaves those which are not taken up in the 
 cold to be acted upon by the aid of heat in a subsequent opera- 
 tion. Thus, for example, in the treatment of most vegetable 
 substances, starch, which is generally present and is only soluble 
 at the boiling-point of water, will remain untouched, while all 
 other principles soluble without heat can be separated from it. 
 
 The mode of performing the process is merely to place together, 
 in a vessel, the solvent and the substance to 
 be dissolved, and to allow them to remain a 
 longer or shorter time, according to the na- 
 ture of the substance. For ordinary purposes, 
 a loosely covered pan of blue stoneware is 
 very convenient. In delicate operations, a 
 beaker-glass, Fig. 340, or solution jar, Fig. 
 343, is more appropriate. When the solvent 
 is volatile, a wide-mouthed stoppered bottle 
 may be used. 
 
 INFUSION. This process is likewise appli- 
 cable almost solely to organic substances. 
 Instead, however, of the solid remaining in contact for a length 
 of time with the solvent, the latter is first heated to boiling and 
 then poured upon the former. After having cooled, the liquid 
 may be decanted or pressed out. 
 
438 
 
 DECOCTION. 
 
 This mode is used for the exhaustion of flowers, leaves, roots, 
 seeds, and other substances of delicate texture, which are easily 
 penetrable and readily yield their soluble matters ; and especially 
 for the purpose of extracting volatile ingredients. The heat 
 applied to the solvent increases its energy ; but as the material is 
 only in contact for a limited time, the interval between the com- 
 mencement and completion of the operation is not sufficient to 
 affect the material or solution, even though one or more of its 
 components are alterable by heat. 
 
 For small operations, a beaker glass covered with a capsule, or 
 a yellow earthenware stew-pan with lip and. cover, such as can be 
 had at the crockery shops, are admirably adapted. In larger 
 pharmaceutical processes, a special apparatus, Fig. 344, is em- 
 Fig. 344. 
 
 ployed. It is known as Alsop and Squire's Infusion Pot, and 
 consists of three pieces, an outer pitcher form vessel A, an inner 
 perforated bowl B, and a cover c. Its material is generally white 
 stoneware or porcelain, but it may also be made of metal. The 
 inner bowl serves as a support for the solid matters to be infused, 
 and retains them, during the treatment, in constant contact with 
 the liquor in the outer vessel. After the action is completed, it 
 is only necessary to remove the cover and lift out the cullendered 
 bowl; for the infusion is clear and ready for use without the 
 necessity of filtration. 
 
 DECOCTION. This mode of solution, which is so important to 
 the Pharmaceutist, is chiefly employed for the purpose of ex- 
 hausting those vegetable substances, which will not readily yield 
 their soluble matters to water. It is merely an extension of the 
 
SOLUTION BY DIGESTION. 439 
 
 last process, and consists in boiling the material to be dissolved 
 with a hot solvent in a covered vessel, or saucepan, until all 
 soluble matter is taken up. Most volatile matters are expelled 
 by decoction; but those which are insoluble, save by prolonged 
 action of heat, are dissolved or suspended, as it were, by favor of 
 other principles present. 
 
 Decoction is only used with liquid solvents which are not 
 decomposable by heat. 
 
 In all of the preceding processes, as well also in others in 
 which solid vegetable matter is subjected to the solvent action of 
 liquids, the calendered ladle, Fig. 345, of tinned wire, is most 
 
 Fig. 345. 
 
 useful for transferring the residue to the press, for removal of 
 any retained liquid. 
 
 DIGESTION. This mode of solution differs from maceration in 
 requiring the assistance of heat, and consists in exposing a body 
 to the prolonged action of a liquid in a covered vessel, at any 
 temperature between 90 F. and several degrees less than the 
 boiling-point of the solvent. The method of heating varies with 
 circumstances, and can be, by a gentle fire, or by the sand, 
 steam, water, or saline Bath, as the nature of the operation 
 may require. 
 
 In analysis, glass or platinum vessels are used ; but in less im- 
 portant operations, those of other materials are more convenient 
 and economical. 
 
 A very important advantage of digestion is, that it allows the 
 perfect solution of all soluble portions of a substance, without 
 modifying the nature of the solvent. It is especially useful for 
 the decomposition of ores, minerals, and other substances diffi- 
 cultly acted upon by acids or other solvents, and also for effect- 
 ing the synthesis of compounds requiring a long-continued heat. 
 Moreover, it is very available in preparing alcoholic and aqueous 
 solutions, medicinal oils, and other pharmaceutical products. 
 
 In analytic operations, digestion is performed in beaker glasses. 
 
440 
 
 SOLUTION BY DIGESTION. 
 
 Fig. 346. 
 
 These are bell-shaped vessels, Fig. 346, of Bohemian glass, and 
 uniformly thin throughout, so as to support a considerable eleva- 
 tion of temperature. The glass must be well 
 annealed, hard, and free from lead, so as to 
 resist the action of acids. These vessels come 
 in nests of different numbers. Their size 
 varies gradually upwards from an ounce in 
 capacity to a gallon. 
 
 The substance to be acted upon, in a state 
 of fine powder, is transferred to the glass, 
 which must be perfectly clean, and is then 
 mixed with the proper quantity of acid or 
 other liquid by shaking the glass after the addition, or by the 
 use of a glass stirrer, taking care, however, in this last instance, 
 if for analysis, to wash off adhering particles previous to its with- 
 drawal, with a little fresh solvent. The glass is then to be 
 covered with a square of window-glass (free from lead), a porce- 
 lain capsule, or watch-glass, whichever is most convenient, so that 
 the volatilized vapors condensing upon its bottom may fall back 
 again into the vessel. 
 
 If the glass is small, it may be directly heated over the lowered 
 flame of a gas or spirit-lamp, Figs. 40, 41, 
 cautiously and gradually heightened as the 
 glass becomes heated. To modify the action 
 of the flame and diminish the danger of frac- 
 ture of the glass, a fine wire gauze 5, for the 
 diffusion of the heat, may be interposed be- 
 tween its bottom and the flame. Fig. 347 
 represents a digestion in a beaker glass a, 
 over a gas lamp c. For larger vessels a SAND- 
 BATH must be used. 
 
 Thin flat-bottomed flasks, with narrow 
 necks and , smooth tops, Fig. 348, made of 
 hard glass, free from lead, are sold especially 
 for this purpose ; but the common sweet oil 
 or Florence flasks are much more economical 
 and equally convenient for operations adapted to their capacity. 
 
DIGESTION UNDER PRESSURE. 441 
 
 When it is important that not even a drop of substance shall be 
 lost, as in analytic operations, the digesting flask should have the 
 form shown in Fig. 349. The body is pear-shaped, with a flat 
 
 Fig. 348. Fig. 349. 
 
 bottom, and gradually tapers towards the mouth, which is lipped 
 to facilitate the pouring of the contents. 
 
 Digestion on a small scale with inflammable liquids, must 
 always be effected by the sand-bath, so as to avoid danger of 
 explosion from ignition of vaporized particles. The sand-bath 
 may then be heated over the lamp, as at Fig. 155 ; and in large 
 operations by the small charcoal furnace, as at Fig. 124. 
 
 A digestion apparatus, of Berlin porcelain, adapted for a water- 
 bath, is shown in Fig. 350. Its dimensions 
 are 7 inches in height, and 4 inches in dia- 
 meter, the capacity being about 40 ounces. 
 The projection b is a flange for its support 
 in the bath ; a, the socket for a wooden 
 handle, and (?, a section of the cover. 
 These vessels, made also of other sizes, are 
 very convenient in pharmaceutical opera- 
 tions, for the digestion of organic matters, 
 especially those of vegetable origin. 
 
 Digestion under Pressure. The solvent power of water may 
 be greatly increased by presenting it to the substance in the state 
 of vapor. This property affords the advantage of making aqueous 
 solutions of highly obstinate substances. The appropriate appa- 
 ratus is termed a digester. That which Papin used for exhausting 
 bones of their gelatin, Fig. 351, consisted of a strong, cylindrical, 
 iron or copper vessel, with sides sufficiently thick to resist 
 
442 
 
 SOLUTION. 
 
 Fig. 351. 
 
 a considerable degree of pressure. The cover, made to fit 
 closely to the body, is fastened down 
 by a screw s. There are two openings in 
 it, one for the stop-cock c, and the other 
 for the safety-valve v, with its weight 
 I w, by which it can be loaded so as to 
 resist a pressure within of 40 to 50 at- 
 mospheres, if necessary. The arrange- 
 ment of the valve is shown in the broken 
 part of the drawing. The steam accu- 
 mulating in the upper part of the body, 
 when matters are under treatment, being 
 confined by the loaded valve and unable to 
 escape, exerts a great pressure upon the 
 
 liquid mixture beneath, and thus allows it to be raised to a very high 
 degree of heat without boiling. The stop-cock c is convenient as 
 a try-cock, for making examinations during the progress of the 
 experiments. The lever regulates the pressure in proportion to 
 the weight placed upon it. 
 
 In large operations, D'Arcet's apparatus (see Encyclopaedia of 
 
 Fig. 352. Fig. 353. 
 
 Chemistry, article GELATIN) is much used. It is shown in Figs. 
 352 and 353. Our description rjefers to the extraction of gelatin 
 from bones by water in a state of tense vaporization. 
 
D'ARCET'S DIGESTER. 443 
 
 Fig. 352 is a vertical section of the apparatus. A is an 
 hermetically closed cast-iron cylinder, into which the steam is 
 conducted ; a the main steam-pipe ; b a vertical pipe conveying 
 the steam into the cylinder A ; c c hranch-pipes leading the steam 
 to the bottom of the cylinder; d a stop-cock upon the pipe 5, for 
 regulating the entrance of the steam into the interior of the 
 cylinder. (The tubes and the cylinder should be wrapped around 
 with woollens, so as to retain their heat and prevent their cool- 
 ing.) e is the stop-cock for the discharge of the gelatinous solu- 
 tion ; / the cover of the cylinder, which is fastened to the cylin- 
 der, so as to prevent the escape of any of its contents; g a 
 tubulure in the cover for the reception of a thermometer ; h a tub 
 to receive the solution as it is formed ; i a gutter for conveying 
 into another vessel the grease which is run off in the commence- 
 ment of the operation; K another gutter, moving on a pivot, 
 which receives the liquid as it runs from the cock e, and empties 
 it into the tub A, or into the trench i ; I a tube for feeding the 
 interior of the cylinder with fresh water ; m a movable adjust- 
 ment attached to the pipe I for regulating the quantity of water 
 and preventing a too great elevation of temperature in the inte- 
 rior of the apparatus. 
 
 Fig. 353, elevation of the interior basket, made of wire-cloth. 
 This basket, or cage, receives the cleansed and crushed bones, 
 and is enclosed in the cylinder A ; a is the handle with which, by 
 means of a pulley, it is lifted or lowered, to be emptied or charged. 
 Four or more of these machines make a series, and the boiler 
 which feeds them with steam should carry a pressure of 4 Ibs. to 
 the inch. 
 
 When volatile or costly liquids are used as solvents in digest- 
 ing processes, it is necessary, both on the score of economy and 
 of the efficacy of the process, to use certain precautions. In 
 making pharmaceutical preparations with alcohol or ether, for 
 example, it must be remembered that these liquids volatilize by a 
 high heat, and unless the vaporized particles are by a suitable 
 arrangement condensed and returned to renew action upon the 
 substance, the latter will be evaporated to dryness long before 
 sufficient time has elapsed for the completion of its solution. For 
 this purpose an ordinary cooling-worm may be attached, as shown 
 in Fig. 354. The vapors escaping from the digesting vessel a, 
 
444 
 
 SOLUTION. 
 
 are condensed partly in the inclined tube 6, and partly in the 
 worm c, and fall back again into the flask as soon as they become 
 liquefied by the water surrounding the worm. This arrangement 
 allows a prolonged contact of solids and volatile liquids, without 
 loss or alteration of the latter, a very important consideration, 
 as time is an influential adjunct in digestion. 
 
 Fig. 354. 
 
 Fig. 355. 
 
 Mohr improves upon the above apparatus, by giving it the 
 form exhibited in Fig. 355. It consists of a tin plate cylinder 
 A, tubulated at its bottom. Through this tubulure passes a glass 
 
SOLUTION BY BOILING. 
 
 tube 1 1, adjusted by perforated corks to the tubulures of both 
 cylinder and digesting vessel M. The vaporized matter, ascend- 
 ing from the heating vessel M, is cooled by the water in the 
 cylinder, and which surrounds the tube 1 1. The long-barrelled, 
 tin plate funnel T, receives the amount of water freshly added, 
 and conveys it to the bottom to displace that which has become 
 heated, and which by its less density rises to make its escape 
 through the outlet A. 
 
 SOLUTION BY BOILING. This mode is resorted to when a sub- 
 stance can only be exhausted of its soluble portion at the boiling- 
 point of the solvent. The exact point of temperature at which a 
 liquid boils, depends partly upon the amount and fluctuations of 
 pressure, and the nature and construction of the vessel. When 
 the pressure of supernatant vapor is removed by uncovering the 
 vessel, ebullition is facilitated and takes place at lower tempera- 
 tures. Indentation or roughening of the surface of the heating 
 vessel, or any other means by which the heating surface is in- 
 creased, and escape of gaseous matter is promoted, lowers the 
 boiling-point of a liquid. For this latter reason, platinum scraps 
 or pieces of unglazed card, or of cork, pacify turbulent ebullition 
 and render the process tranquil and uniform. 
 
 The heat applied should never exceed the degree at which the 
 solvent boils, especially in metallic vessels, otherwise ebullition 
 is retarded, for beyond a certain temperature a repulsion between 
 the particles of liquid and the metallic surfaces prevents direct 
 contact. 
 
 The kind of apparatus varies with the nature and quantity of 
 material under process. 
 
 Soiling in Tubes. Test-tubes, Fig. 356, are very convenient 
 implements for delicate solutions, assays, and the like, and, there- 
 fore, the laboratory should be supplied with a large assortment, 
 varying from three inches in length and a quarter inch in dia- 
 meter to six inches in length and one inch in diameter. They 
 should be of hard, white German glass, free from lead, with 
 perfectly round bottoms, uniformly thin, so as to withstand heat. 
 The rack, Fig. 39, serves as their support. 
 
 A test-tube should never be charged with more than one-third 
 its capacity of solvent, else there may be loss by ejection from 
 too sudden ebullition; and the solid substance, previously pow- 
 
446 
 
 SOLUTION. 
 
 dered, is not to be added until the liquid is brought to boiling, 
 and then only in small portions at a time. 
 
 To guard against spirting, and to insure a uniform heating, the 
 tube must be gradually heated, not upon its bottom, but near to 
 
 Fig. 357. 
 
 or on the side, as shown in Fig. 35T. It is, as seen, heated 
 over a small lamp, being held in the fingers, -which are pro- 
 tected from contact with the hot glass by a doubled strip of thick 
 
 Fig. 358. 
 
 paper wrapped around the neck of the tube for its support. The 
 spring holder, Fig. 358, consisting of a wooden handle affixed 
 to two flat pieces of sheet-brass, indented at their ends so as to 
 
SOLUTION IN TEST-TUBES. 447 
 
 form a round catch, and tightened or loosened by a slide, would 
 be much more convenient for the purpose. 
 
 The mouth of the tube during heating, or whilst its contents 
 are being shaken, should always be held away from the operator, 
 else ejected matter may endanger his person or dress. 
 
 Faraday gives the following valuable advice as to the use of 
 test-tubes for making solutions with volatile liquids, and under 
 pressure. 
 
 "In consequence of the small diameter, and therefore small 
 sectional area of tubes, they are much stronger relatively to 
 internal pressure than larger vessels, such as flasks of the same 
 thickness. An advantage is thus gained in some cases of solu- 
 tion or digestion in certain fluids, as alcohol, ether, and even 
 water, because it enables the experimenter to subject the sub- 
 stances to temperatures as high as the boiling-points without loss 
 of the fluid, or occasionally to temperatures still higher, the 
 ebullition going on as it were under pressure. This is easily per- 
 formed with alcohol, ether, and similarly volatile fluids, in tubes 
 of four, five, or six inches in length, and of such diameter as to 
 be readily and perfectly closed by the finger. Suppose a tube 
 of this kind, one-third filled with alcohol, and held tightly between 
 the thumb and second finger of the right hand, its orifice being 
 closed by the forefinger of the same hand, Fig. 339. The fore- 
 finger is to be relaxed, and the heat of a spirit-lamp applied until 
 the alcohol begins to boil ; the forefinger is then to be reapplied 
 closely, and it will be found that the flame of the lamp, applied 
 at intervals, is quite sufficient to keep the temperature up to the 
 boiling-point. No alcohol can evaporate, for the finger has power 
 sufficient to retain the vapor even were its force equal to two 
 atmospheres, and the tube itself is also strong enough to resist 
 the same force. 
 
 " This operation is very advantageous when valuable and vola- 
 tile solvents are in use; it is therefore worth while to refer to 
 those points which indicate the state and temperature of the 
 fluid, and which make the practice easy. If the fluid be one 
 which, like alcohol, when at or above its boiling-point is at a 
 temperature inconvenient to the hand, then, if all the common 
 air were allowed to pass out of the tube before closing it, the 
 whole tube would become heated by the vapor rising from the 
 
448 SOLUTION. 
 
 hot liquid beneath, and the fingers would be injured ; but by not 
 allowing all the air to escape, that portion which is retained in 
 the tube is always forced to the top by the successive formation 
 and condensation of the vapor below, and interfering with the 
 passage of the hot vapor to the part which it occupies, it pre- 
 serves that portion of the tube at comparatively low and very 
 bearable temperatures. The part thus retained at a low tempe- 
 rature is proportionate to the quantity of air confined in the tube ; 
 this quantity is usually a proper one if the tube be closed just 
 after the alcohol has begun to boil, and before the upper part of 
 the tube has been heated. If too much air has been expelled, 
 and the tube is found to become hot above, the application of 
 the flame must be suspended a moment or two, the whole suffered 
 to cool below the boiling-point, the tube opened, the upper part 
 cooled slightly by a piece of moist paper or a cold finger, and 
 then the forefinger is to be reapplied to close it as before. 
 
 " The state of the fluid within is in part indicated by the pres- 
 sure of the air or vapor on the finger, the latter being urged 
 away from the tube by a force proportionate to the degree of heat 
 above the boiling-point, and being drawn inwards when the heat 
 is below that point. Generally, therefore, the finger alone will 
 serve to ascertain whether the temperature is above or below the 
 point of ebullition ; but as the force required is, after operating 
 for some time at high pressures, such as to diminish the sensi- 
 bility of the finger to smaller pressures, it sometimes happens 
 that, on lowering the temperature, the period at which it attains 
 that of ebullition in the atmosphere cannot be distinguished. 
 This point is, however, easily recognized by relieving the pres- 
 sure of the finger slightly ; should the quiescent fluid below then 
 burst into ebullition, it is a proof that its temperature is higher 
 than the boiling-point at atmospheric pressure, but should it re- 
 main quiescent until the finger is entirely removed, its tempera- 
 ture will be known to be below that point." 
 
 Boiling in Beaker Glasses and Flasks. These vessels are 
 used when large quantities of liquid are to be operated upon. 
 When the direct heat of the lamp is applied, it should be diffused 
 by the intervention of a wire gauze. The preferable mode of 
 heating is by a highly heated sand-bath. The same remarks as 
 to their material and construction, as given before at p. 271, are 
 
BOILING IN CAPSULES. 
 
 449 
 
 applicable in this instance. They should be loosely covered 
 during the operation, the beaker glasses with capsules, and the 
 mouths of the flasks with watch-glasses. The position of the 
 beaker glass over the lamp is shown at Fig. 347, that of flasks 
 at Fig. 155. Round-bottomed flasks, Figs. 359, 360, 361, are 
 
 Fisr. 3f>9. 
 
 Fig. 360. 
 
 Fig. 361, 
 
 Fig. 362. 
 
 made of different sizes, especially for solutions; but Florence 
 flasks, Fig. 362, which have been rounded on the edges of the 
 mouth over the blowpipe flame, so as to allow the easy en- 
 trance of a loose cork, are equally convenient and less costly. 
 They are thin and uniform throughout, and bear very high tem- 
 peratures without fracture. Annexed are drawings, also, of two 
 wide-mouth boiling flasks, which, like the above, have round 
 bottoms. 
 
 Fig. 363. 
 
 Fig. 364. 
 
 Boiling in Capsules. Solution is made in open vessels when 
 the solvent liquid is not easily vaporizable or alterable by expo- 
 
 X* 
 
450 
 
 SOLUTION BY STEAM. 
 
 sure, or when its loss is of little consequence. The most conve- 
 nient implements for the purpose are porcelain capsules, Figs. 
 365, 366. Those from the French and Royal Prussian factories 
 
 Fig. 365. Fig. 366. 
 
 are far superior to those of any other make. They are strong, 
 yet uniformly thin throughout, and support very high tempera- 
 tures and sudden changes. Being enamelled, they are protected 
 from the action of acids or corrosive liquids, and consequently 
 are of general application. They are sold of all sizes, varying 
 upwards from an ounce to 18 oz. in capacity. The diameter of 
 the smallest is about two inches, and that of the largest 15J 
 inches. The depth should be one-third of the diameter. The 
 smaller sizes come in nests of a half dozen or more. Fig. 365 
 represents one with spreading rim and lip to facilitate pouring. 
 That shown in Fig. 366 has a more hemispherical shape. 
 
 Capsules are almost always heated over the open fire, the spirit 
 or gas lamp furnishing the requisite temperature. Those of 
 smaller size are shown in position upon suitable supports at Fig. 
 154, and z, Fig. 155 ; and for the larger, Luhme"s lamp, Fig. 
 158, answers an admirable purpose. 
 
 The liquid is placed in the capsule before the ignition of the 
 wick, and when it is boiling, the substance to be acted on should 
 be gradually deposited in it in a finely divided state, during con- 
 stant stirring with a glass rod. After all has been added, both 
 ebullition and stirring must be continued until the completion of 
 the process, care being taken to supply the loss of the volatilized 
 portion by fresh additions of the solvents, unless the solution is to 
 be evaporated. 
 
 When the nature of the materials requires the intervention 
 of a medium other than sand to modify the heat, a rare occur- 
 rence when operating in capsules, the latter are heated over 
 baths, as shown at Fig. 200. Capsules or boiling pans of ena- 
 melled ironware or tinned copper are used only in very large 
 operations. 
 
 SOLUTION BY STEAM. When a substance is to be dissolved 
 
SOLUTION BY STEAM. 451 
 
 by steam heat, and the nature of the materials renders the direct 
 application of steam inadmissible, then baths, Fig. 18, come very 
 appropriately into play. 
 
 For aqueous solutions which are greatly facilitated by the 
 immediate action of steam, it is supplied through flexible lead 
 tubes, leading from the generator, Fig. 15, directly into the con- 
 taining vessel. 
 
 For small operations in glass vessels, the copper spritz, Fig. 
 240, half filled with water, and heated over the gas lamp, readily 
 furnishes sufficient steam. 
 
 As boiling by steam is practised in numerous chemical opera- 
 tions, it is proper to introduce some directions pertinent to the 
 subject. 
 
 It is very seldom that the heat required for ordinary labora- 
 tory purposes exceeds that given by five pounds, or at furthest 
 fifteen pounds, above atmospheric pressure, and the fire under 
 the generator and weights upon the safety valve should be regu- 
 lated accordingly. 
 
 If the mixture to be boiled is unalterable by the action of 
 condensed steam, the conduit-pipe may lead directly into it, and 
 to the bottom. 
 
 As the liquid appears to boil before it actually does, the only 
 sure indication of temperature is to be obtained by a thermome- 
 ter, Fig. 119. 
 
 This method, however, causes a great loss of heat and incom- 
 modes the operator, by filling the apartment with clouds of vapor. 
 A loose cover will partially remove these objections. In boiling 
 in this way, care must be taken that the fire does not get low, 
 lest a condensation of the vapor occupying the upper part of the 
 boiler causes a partial vacuum, and the consequent drawing over 
 of part of the liquid from the vat into the boiler. The conduit 
 connected with the feeder should always have a stop-cock near 
 the coupling, which is to be shut off upon the completion of the 
 operation. If the boiler should then happen to be surcharged 
 with steam, it must be blown off through the valve, this being 
 readily accomplished by gradually unloading the lever. 
 
 A far better plan of boiling by steam is to conduct it through 
 a coil of pipe placed at the bottom of the vat, and having an 
 exhausting-pipe leading into the neighboring flue. This mode 
 
452 
 
 SOLUTION BY DISPLACEMENT. 
 
 Fig. 367. 
 
 allows a uniform temperature at any degree, upwards, from 
 that of the atmosphere suitable stop-cocks being attached for 
 that purpose to regulate the supply of steam accordingly. 
 
 In cold weather, and especially when the feeder or conduit are 
 of any length, it will be economical to wrap 
 them with woollen listings or straw, as means 
 of preventing condensation. 
 
 SOLUTION BY DISPLACEMENT. Displace- 
 ment, termed also lixiviation, when applied 
 to the solution of saline substances, is an 
 economical, speedy, and efficient means for 
 the extraction of the soluble portions of woods, 
 leaves, flowers, barks, precipitates, and similar 
 matters, by the infiltration of a liquid solvent 
 through them. This process is equally appli- 
 cable for maceration, infusion, and decoction; 
 for though operating in the cold, it accom- 
 plishes its purpose. 
 
 For delicate operations, and those con- 
 ducted upon a scale of moderate extent, glass 
 vessels may be employed. One of the usual 
 form is shown in Fig. 367. It is made of hard glass, free from 
 Fig. 368. lead, the upper part, or A, being the displacer, and 
 the lower part, B, an ordinary flask, the recipient 
 of the saturated solution. The mouth of the bottle 
 and that portion of the displacer which rests in it 
 should be ground so as to make a close joint. 
 The stopple is for closing the upper vessel when 
 necessary. Dobereiner's modification of the above, 
 but operating upon the same principle, is shown in 
 Fig. 368. To prevent the passage of the material 
 through the barrel of the displacer, it must be loosely 
 closed with a plug of raw cotton as at f, and then 
 adjusted by means of a perforated cork g, with the 
 vertical tubulure of the globular receiver a. The 
 whole apparatus as adjusted is retained in an upright 
 position by a support, the receiver resting upon a braided straw 
 ring. It is then ready to receive its charge. The substance in 
 coarse powder and moistened, occupies the part of the vessel , 
 
SOLUTION BY DISPLACEMENT. 
 
 453 
 
 Fig. 369. 
 
 and the solvent is subsequently added as at d. A partial vacuum 
 being made in the receiver by the evaporation of a few drops of 
 alcohol added through the lateral stoppered tubulure <?, the liquid 
 percolates through the solid mass by the force of atmospheric 
 pressure, and ultimately reaches the receiver saturated with the 
 soluble matter of the material e. 
 
 In order to express clearly the rationale of this process, we 
 will suppose that vegetable matter, a dye-wood for example, in 
 coarse powder, is to undergo exhaustion by this method. It oc- 
 cupies the part e, as before said, and to facilitate the percolation, 
 has been previously moistened with a portion of the solvent. If 
 the substance swells easily it must be packed lightly. Liquid is 
 added, as shown at d, and soon soaks into the mass beneath ; 
 another portion of the solvent is then 
 poured in as before, and takes the 
 same course, displacing the portion 
 before used without mixing with it. 
 These strata of solvent are pressed 
 downwards by successive additions of 
 liquid, and become more and more 
 charged with soluble matter, as they 
 approach the bottom of the mass, until 
 at last they run out into the recipient 
 highly charged, and, in the present in- 
 stance, highly-colored ; the first run- 
 nings being more nearly saturated 
 than those which follow. When by 
 consecutive additions of solvent the 
 material has become exhausted, the 
 liquid passes through the mass and 
 reaches the receiver as tasteless and 
 uncolored as when first poured in. 
 This indicates the completion of the 
 process. 
 
 Robiquet's displacer, which differs 
 somewhat from the preceding, is shown 
 by the annexed drawing, Fig. 369. It consists of 
 ground glass stopper A, and a receiving bottle c. 
 
 The body, m n o p, of the stopper is hollow, and pierced with 
 
 barrel B, a 
 
454 
 
 SOLUTION BY DISPLACEMENT. 
 
 Fip. 370. 
 
 a hole/, of about one-tenth of an inch diameter. There are cor- 
 responding holes also in its bottom e, as well as at d and h of 
 the barrel, and g of the receiver. 
 
 When the stopper is placed in the mouth of the barrel, so that 
 the two holes /and d come together, there is still a communica- 
 tion between the external air and the interior of the barrel, which 
 is further established by bringing the two other openings g and 
 h into coincidence. 
 
 It will be readily seen, therefore, that the internal pressure of 
 the air, and the flow of the percolating liquid, can be regulated 
 at pleasure, merely by turning the barrel more or less, so as to 
 shut or close the opening as may be desired. 
 
 The neck of a retort, with its smaller end adjusted to a wide- 
 mouth bottle by means of a perforated cork, makes an excellent 
 displacing apparatus. 
 
 When the solvent is volatile, in order to prevent loss by eva- 
 poration, the apparatus must have a modified form, as shown in 
 Fig. 370. The displacer is adapted to the 
 centre tubulure of a two-necked Wolfie bottle. 
 As atmospheric pressure is an important agent 
 of this process, it will not do to shut it off by 
 closing the top of the displacer without making 
 some compensating arrangement, and, therefore, 
 a communication between the upper and lower 
 vessel is established by means of a bent tube 
 adjusted in the lateral tubulure of each. In 
 this manner the vessel is completely closed, and 
 vaporization prevented, while the pressure pro- 
 duced is distributed throughout the vessel, and 
 thus rendered uniform. In using the glass dis- 
 placement apparatus first described, this prin- 
 ciple must be recollected ; where a vacuum is not artificially 
 created in the receiver, the ground glass edges of it and the dis- 
 placer should either be permanently separated or occasionally 
 disjointed. 
 
 The stop-cock near the bottom of the receiver allows the with- 
 drawal of the solution as fast as it accumulates, without the 
 necessity of disarranging the apparatus. In experiments upon 
 large quantities of material, and in pharmaceutical operations 
 
SOLUTION BY DISPLACEMENT. 
 
 455 
 
 Fig. 371. 
 
 generally, the displacers employed are made of tinned copper or 
 tinned plate. Those of porcelain, which are now in the market, 
 are much more serviceable, because they are readily cleansed 
 and resist the action of corrosive liquids. Of whatever material 
 they are made, they should be cylindrical and funnel-shaped at 
 the base, and the height should be at least four times the diame- 
 ter, as is shown in Fig. 3T1. At a there is a flange in the interior 
 as a support for the cullendered dia- 
 phragm a b. These diaphragms are re- 
 movable, and for convenience in handling 
 have a knob in the centre. The lower 
 diaphragm is always to be covered with a 
 circle of coarse muslin, for the reception 
 of the material, and to prevent the pas- 
 sage of particles as well as obstruction of 
 the holes. The other diaphragm, fitting 
 loosely to the cylinder, rests upon the 
 top of the powder, and serves for the 
 better distribution of the solvent and for 
 the prevention of the escape of dusty 
 particles, which sometimes occurs if the 
 powder is put in dry. The stop-cock c 
 in the barrel or exit-pipe is useful for 
 regulating the discharge of the liquid. 
 
 The tripod D is the support, and allows 
 the withdrawal of the receiver P, when it is full, and when it is 
 to be replaced by another, without the necessity of disturbing the 
 displacer. 
 
 Payen's is another very convenient form of displacer, in which 
 ether, alcohol, and any other volatile solvent may be kept in con- 
 stant action without exposure to air or loss by evaporation. By 
 its use a great saving of time and labor and solvent is gained. 
 The arrangement is exhibited at Fig. 372. It consists of a glass 
 cylinder B, the funnel of which should reach to the centre of a 
 glass balloon A, beneath the two vessels, being attached by means 
 of a perforated cork. The lateral tube <?, d, opens communication 
 between the lower and upper apartments. As the whole forms 
 a perfectly tight connection, the safety-tube E becomes neces- 
 sary for the regulation of the dilatation and contraction of the 
 vapors. 
 
456 
 
 SOLUTION BY DISPLACEMENT. 
 
 Fig. 372. 
 
 When it is desired to exhaust a vegetable matter with alcohol 
 
 or ether, and at one and the 
 same operation to concentrate 
 the charged solvent, plug the 
 barrel of B with raw cotton, pre- 
 viously moistened with the liquid 
 to be used ; add the powdered 
 material, cover it with a cullen- 
 dered disk, pour on the liquid in 
 quantity sufficient to give a fil- 
 tered solution of half the capa- 
 city of the balloon, and then 
 connect the apparatus. The 
 balloon is now to be placed half 
 its depth in the water-bath H, 
 and the apparatus sustained in 
 a perpendicular position by 
 means of a clamp support. The 
 water-bath is to be closed with 
 a loose cover, and heated as may 
 be required by the small spirit- 
 lamp I. The ether or alcohol 
 which has infiltrated into the 
 balloon thus carried to, and 
 maintained at ebullition, passes 
 off as vapor into the lateral tube, 
 there partially condenses and 
 falls upon the material in the 
 
 cylinder to infiltrate through again. The excess of vapor and of 
 expanded air escapes through the safety-tube ; but a part of the 
 vapor is arrested and condenses in the three bulbs, the first of 
 which immediately empties its liquefied contents into the cylinder 
 to renew its action upon the powder. 
 
 The concentration of the filtered solution is thus continually 
 going on in the balloon, the concurrent distillation returning the 
 evaporated particles to the substances to be exhausted, through 
 the lateral tube <?, d. 
 
 When water is the liquid to be employed, the water-bath must 
 be replaced by a saline or sand-bath, and the spirit-lamp by a 
 furnace. 
 
SOLUTION IN CLOSE VESSELS. 457 
 
 For the solution of difficultly soluble substances, displacement 
 presents many advantages, and amongst others it yields a clear 
 solution, and supersedes the necessity of FILTRATION, which is 
 required for most solutions made by infusion, decoction, and 
 boiling. It is particularly applicable to the purpose of procuring 
 concentrated solutions for EVAPORATION to extracts, as well as 
 for making tinctures, &c. 
 
 The solvent may be acid, alkaline, spirituous, ethereal, or 
 aqueous in its nature, the principle of its action being the same 
 in all cases. When the liquid is corrosive, however, the vessel 
 should not be metallic, but of glass or porcelain, and should be 
 plugged with asbestos instead of cotton. It is immaterial whether 
 the solvent be applied cold or warm, save when the process is 
 resorted to for the separation of substances soluble in cold from 
 those which are only soluble in hot liquids. Except in such cases 
 heat may be used, as it increases the power of the solvent ; and 
 a convenient means of applying it is to encompass the apparatus 
 with a metallic jacket, and supply the intervening chamber thus 
 formed with a current of steam from the generator, Fig. 16. 
 
 There are certain conditions necessary to the success of this 
 operation. The material must be in powder of medium DIVISION ; 
 neither too fine nor too coarse, for in the first case it clogs the 
 cloth and holes of the diaphragm, and, if heavy and compact, 
 retards the percolation of the liquids. On the other hand, when 
 too gross, the transit of the solvent is so rapid that the material 
 is but partially acted upon. When alcohol or ether is used, the 
 powder may be a little finer than for less volatile solvents ; and 
 all powders liable to set, or to become so compact as to prevent 
 the passage of liquid, must previously be mixed with well-washed 
 coarse white sand. This 4 addition remedies the defect and insures 
 the easy passage of the solvent. 
 
 The material, as before recommended, should be moistened 
 with half its weight of the solvent, and left to soak for an hour 
 or more before being placed in the percolator. After having 
 been transferred, it is covered with the diaphragm, and sufficient 
 liquid is poured upon it to cover entirely its surface. As soon as 
 this first portion infiltrates through the mass, another portion is 
 added ; for it is only by keeping the surface covered with solvent 
 that a uniform penetration of all portions of the mass can be 
 
458 
 
 CADET S MODE OF SOLUTION. 
 
 effected. If the liquid passes through very rapidly, the mass is 
 too loose, and must therefore be compressed by pressing upon 
 the diaphragm cover. Or, in order to prolong their contact, the 
 stop-cock c may be nearly closed, so as to allow the exit of only 
 a thin stream. 
 
 When alcohol or other valuable volatile liquid is used, the resi- 
 dual portions may be either extracted by pressure of the mass P, 
 or by displacement with water ; and subsequently, by distillation 
 of the resulting mixture. The general practice, however, in the 
 laboratory is to reserve the last running for the first application 
 to fresh material. 
 
 CADET'S MODE OF SOLUTION. This plan is well adapted to 
 those powders which do not admit of being easily infiltrated. 
 It consists in macerating or infusing the pulverized material 
 with double its weight of cold or hot solvent, and after some 
 time subjecting it to strong pressure. This treatment is to be 
 repeated until the substance ceases to yield soluble matter, and 
 the resulting liquids are then mixed together and filtered. 
 Cadet's mode is used largely for dissolving the tannin from galls 
 with ether. 
 
 A suitable press for this purpose is shown at Figs. 373 and 
 374. All powders which have undergone the process of solution 
 
 Fig. 373. 
 
 Fig. 374. 
 
 n 
 
 in large quantity should be subjected to its action, as a good 
 deal of retained solution may thus be obtained, and consequently 
 saved. 
 
 It is formed of two strong upright stanchions, and two propor- 
 tionably strong cross-pieces, firmly jointed in the side-beams. 
 T.ie upper cross-piece carries a box through which works an ordi- 
 
CADET'S MODE OF SOLUTION. 459 
 
 nary press screw, in the usual manner. Upon the lower cross- 
 piece, is placed a wooden trough, A (Fig. 374), at least two 
 inches deep, and to the front of which is adapted a gutter B, for 
 the conveyance of the liquid, which assembles in the trough, to 
 a vessel E, placed at and beneath its mouth. Upon and within 
 the trough is placed a wrought-iron plate cylinder. This cylin- 
 der is formed of two semi-cylinders joined together. Throughout 
 its height, it is divided off alternately into equal parts by zones 
 or belts. The zones a a are more than an inch broad; the 
 partition 6, &c., four or five inches in width. The top as well as 
 the lower zone is narrow. All the wider divisions are cullendered 
 throughout their circumference with innumerable small holes, 
 through which the liquid is to flow when pressure is applied. 
 All the narrow zones are secured by a strong wrought-iron ring, 
 formed of two pieces working on a hinge adjusted at the back. 
 Upon the front is a movable broach D, which bolts them together, 
 and makes the cylinder compact, so that it can resist the pres- 
 sure applied. When the marc is exhausted, by draining out the 
 broach D, the circumference of the cylinder is loosened or ex- 
 tended, so that its contents can be removed without difficulty, 
 The marc is placed in this cylinder and pressed out by the power 
 of the screw, until no more fluid will exude, even with the force 
 of a man to the lever. The liquid runs into the gutter B and 
 through a sieve, which should be properly placed for the purpose, 
 into the vessel E, and may thence be drawn off after it has 
 settled, into suitable vessels. The residual exhausted powder is, 
 as said above, easily emptied out by loosening and removing the 
 pin D. 
 
 A much more convenient implement than the preceding is the 
 lever press, described in Muspratt's Chemistry, and a perspective 
 view of which is shown by Fig. 375. It consists of two wrought- 
 iron pillars B B, supported in sockets by the cast-iron feet A A. 
 The bed-piece c is also secured to the feet by two perforated ears, 
 and has two intersecting grooves sunk into its surface, as chan- 
 nels for conducting off the expressed liquid. The follower D, 
 corresponding in size with the bed-piece c, is adjusted to the pillars 
 by sliding-ears, and has the rack-bar F fixed in the centre. The 
 gearing is sustained by framework E attached to B B. Motion 
 is effected as follows: The ratchet-wheel G turns upon an axle 
 
460 
 
 CADET S MODE OF SOLUTION. 
 
 having its bearings in the top frame. On the same centre is a 
 fixed pinion of eight teeth, only partially seen in the figure, which 
 
 Fig. 375. 
 
 Fig. 376. 
 
 works in the wheel I, of twenty-four cogs ; and upon the axis of I 
 is another eight-teeth pinion, which acts upon 
 the rack. The lever K is forked at the extre- 
 mity nearest the small winch-handle L, and the 
 terminations of the furcation are received upon 
 the axle G. A pin, near H, is adapted to a small 
 9 hole in the frame, by the insertion of which the 
 ' descent of the lever may be prevented. The 
 matter to be pressed is placed in a shallow, 
 cylindrical box A, of tinned copper, Fig. 376, 
 which rests upon the bed c of the press. To 
 prevent the contents from being pressed against 
 the sides of the cylinder, and thus obstructing the flow of the 
 liquid thence, it is necessary to use a perforated band with per- 
 pendicular ribs on the exterior. Being movable and formed of 
 two parts joined together by a hinge, it can be easily put in 
 proper position around the matters to be pressed (after the latter 
 has been placed in the box), and fastened by means of the pin. 
 The ribs on the outer circumference of this band project against 
 
SOLUTION UNDER PRESSURE OP STEAM. 461 
 
 the inner sides of the box, and form intermediate grooves, through 
 which the expressed liquid, issuing from the holes, can readily 
 pass off into the receiving vessel at the spout beneath. 
 
 To put the press in action, the lever being upheld by the pin 
 at H, the winch-handle is turned to the left, in order to lower the 
 rack and follower, until the latter presses upon the wooden block 
 B, Fig. 376, which caps the material under pressure. The lever 
 is then raised, and the pall allowed to work into the ratchet, 
 which will cause the latter to turn, and produce the descent of 
 the rack. This is repeated, if requisite, until a considerable 
 pressure is obtained ; and should it be desired to go on, the lever 
 is elevated considerably above the horizontal line, and left to 
 follow the consolidation of the contents of the bag. If, however, 
 this is unnecessary, the pin H is inserted, upon which the lever 
 remains. The amount of pressure is also regulated by the dis- 
 posal of the weight M in the various notches of the lever. 
 
 When it is not expedient, as in the case of pulpy and similar 
 matters, to press the substance in the box without first enveloping 
 it in a cloth, it may be wrapped in unbleached Russia canvas ; 
 and the bag-shape bundles thus formed placed in the box, with a 
 stiff plate of tinned copper interposing every two of them. They 
 should be folded so as not to make a thickness of more than an 
 inch. 
 
 As the cloths absorb a considerable quantity of the expressed 
 juice, and occasion loss, the pressing should be accomplished 
 without them in all possible cases. The cloths, used for confining 
 substances from which oily liquid is to be expressed, must be 
 woollen and thick. 
 
 The pressure must be in all cases gradual at the commencement. 
 
 Solution under Pressure of Steam. Figs. 377 and 378 ex- 
 hibit Duvoir's bucking apparatus, which, as modified in the draw- 
 ings, is applicable to the exhaustion of organic matter. B B are 
 the wooden vats lined with lead which receive the material to be 
 displaced ; G G the cullendered diaphragms for its support ; and 
 c c their movable covers counterpoised so as to admit of ready 
 depression or elevation at will. These false bottoms are also 
 movable, so as to afford facility in cleansing the vat, and they 
 should, when in use, be covered with crash cloths to prevent ob- 
 struction of the holes. The tubes D D, communicating with the 
 

 462 
 
 SOLUTION UNDER PRESSURE OF STEAM. 
 
 steam generator, Fig. 16, traverse the centre of the vats, and are 
 surmounted by metallic disks, E E, for the reverberation of the 
 vapor rushing against them. 
 
 Fig. 377. 
 
 Fig. 378. 
 
 The directions for the management of the apparatus are nearly 
 the same as for displacement generally. When the vat has 
 received its charge, the cover is to be lowered and fastened down 
 by clamps, and steam let on by opening the stop-cock of the 
 feeder. As the steam generates, it passes over through the pipe 
 r>, reaches the disk E, and is projected uniformly over the whole 
 surface of the material. The elastic force of the vapor accumu- 
 lating in the upper portion of the vat exerts a pressure upon that 
 portion which has condensed, and forces it downwards through 
 the mass. In its passage it becomes charged with soluble matter 
 and reaches the lower part of the vat K beneath the diaphragm, 
 whence it is drawn off through the cock L, R. 
 
 As a protection against accidents, there should be a safety- 
 valve upon the cover of the vat as well as upon the generator. 
 
 This arrangement would be particularly economical in the arts, 
 for extracting dyewoods and other vegetable substances. 
 
EVAPORATION. EVAPORATING VESSELS. 463 
 
 CHAPTER XXII. 
 
 EVAPORATION. 
 
 WHEN any liquid is heated for the purpose of expelling vapo- 
 rizable matter, and the process is conducted solely with a view 
 to saving its fixed portion, the operation is termed evaporation. 
 It thus far differs from distillation, which has for its object the 
 preservation of the volatilized portion, in most cases, regardless 
 of the solid. By its aid we can decrease the volume of, or con- 
 centrate solutions for crystallization and chemical reaction, expel 
 valueless volatile ingredients from those which are more fixed, 
 obtain dissolved matter in a dry statej- and prepare extracts and 
 other pharmaceutical products. 
 
 Liquids evaporate more or less at all temperatures, those having 
 the lowest boiling-point yielding the most readily ; but there are 
 certain conditions which greatly promote this tendency. It must 
 be remembered, therefore : 
 
 1. That evaporation is more rapid in dry atmospheres, and 
 that consequently the transit of a constant stream of air over the 
 surface of the heated liquid effects a continual removal of each 
 stratum as it becomes saturated with vapor. 
 
 2. That evaporation is confined to the surface, and conse- 
 quently that the breadth of the evaporating vessel must be 
 extended at the expense of its depth. 
 
 3. That heat greatly facilitates evaporation by lessening the 
 cohesive force of the particles of a liquid, and consequently that 
 the evaporating vessel should present a broad heating surface. 
 
 4. That a diminution of the atmospheric pressure also facili- 
 tates evaporation, for the more perfect the vacuum the lower the 
 boiling-point of a liquid. 
 
 Evaporating Vessels. For analytic purposes, capsules are by 
 far the best implements. The capsules should be very thin, 
 nearly flat-bottomed, with steep sides, a spout for pouring, and 
 glazed throughout. Watch-glasses answer for small experiments, 
 but require to be very cautiously heated, as they are readily 
 fractured. 
 
 Beaker glasses are also used for evaporating solutions which 
 
464 
 
 SPONTANEOUS EVAPORATION. 
 
 would lose by being transferred. Broad-niouthed glass flasks 
 are only employed for slow processes with valuable liquids, which 
 are liable to alteration by too much exposure when ebullition is 
 necessaty. They must be made uniformly thin throughout, of 
 hard German glass, free from lead, and with flat-bottoms, to give 
 them a broad heating surface and a steady position in the baths, 
 in which they are generally placed to be heated. Figs. 379 and 
 380 present the usual forms of matrass for evaporations. 
 
 Fig. 379. 
 
 Fig. 380. 
 
 Fig. 381. 
 
 For the larger operations of the chemist or pharmaceutist, 
 vessels (Fig. 381) of copper, tin, ena- 
 melled iron, tinned copper, and for some 
 purposes very large porcelain capsules, 
 are more suitable. 
 
 Retorts are used when the vaporized 
 particles are of sufficient value to be 
 condensed, as in the process of distilla- 
 tion. 
 
 Spontaneous Evaporation. Those liquids which are very vola- 
 tile, or which become altered by heat, are evaporated by mere 
 exposure to the atmosphere at its ordinary temperature. To this 
 end they are poured into broad shallow vessels, and placed aside 
 until the dissipation of all vaporizable matters, or until crystal- 
 lization ; this mode of evaporation being also employed for pro- 
 curing large crystals, which are better defined than those obtained 
 by rapid evaporation. 
 
 The more dry and hot the atmosphere the more rapid is the 
 
EVAPORATION IN VACUO. 465 
 
 evaporation, because its capacity for dissolving moist vapors is 
 much greater at high than low temperatures. In order to main- 
 tain a continued contact of the surface of the liquid with strata 
 of fresh air, the vessel containing it should be placed in a draught, 
 so that those portions of air which become saFurated with vapor 
 may be displaced. The air-chamber of the jack furnishes an 
 efficient means of spontaneous evaporation. 
 
 When the air might act injuriously, and a vacuum is unneces- 
 sary, a substance may be evaporated in another atmosphere, for 
 instance, of hydrogen or carbonic acid. For this purpose, it is 
 only necessary to adjust the disengagement-leg of the apparatus 
 (Fig. 172) to the tubulure of a retort, so that its end may reach 
 nearly to the level of the liquid in the latter. The generated 
 hydrogen passes into the retort heated to the required tempera- 
 ture, and promotes the discharge of the vapors into the recipient 
 attached to the beak of the retort, and fitted with a small tube 
 in its other tubulure for the disengagement of its uncondensed 
 portions. 
 
 For the evaporation of solutions of sulpho-bases, of sulpho- 
 salts, and of all substances readily oxidizable by exposure, this 
 process is better applicable than that with the air-pump, which 
 is apt to be attacked when the eliminated vapors are corrosive. 
 
 This process is much used in CRYSTALLIZATION, for concentra- 
 ting alterable solutions, and drying precipitates. 
 
 Evaporation in Vacuo. We have already referred to the 
 happy influence of diminished atmospheric pressure in facilita- 
 ting evaporation, and shall now speak of the means by which 
 it is accomplished, and the particular instances in which it is 
 employed. 
 
 This mode is resorted to for hastening the evaporation of all 
 liquids at low temperatures, but more especially of those which 
 would be alterable by exposure to air during the process. 
 
 In small experiments, a capped bell glass H, Fig. 47, is used 
 as the confining space. Under this bell is placed the broad, 
 shallow capsule, with its liquid contents, supported upon a 
 wire tripod, resting in a leaden tray containing sulphuric acid, 
 dried chloride of calcium, fused potassa, or some other absorbent 
 material (DESICCATION). The bottom or bed of the bell may be 
 a ground glass plate, and to seal the joints hermetically the rim 
 
 30 
 
466 EVAPORATION IN VACUO. 
 
 of the bell should be greased. Connection being made by means 
 of a suitable pipe, and the stop-cocks between the bell and the 
 syringe, communication is opened and the vessel exhausted of air. 
 The pressure being thus removed, evaporation proceeds rapidly ; 
 and until the absorbent matter becomes saturated with vaporized 
 particles, or the bell filled, there is no impediment. The latter 
 can be partially removed by working the pump at frequent in- 
 tervals. 
 
 When an air-pump is used, the procedure is the same ; but, in 
 either case, the vacuum must be produced gradually, otherwise 
 the sudden ebullition of the liquid may cause ejection of its par- 
 ticles. The better way is to cease pumping as soon as the baro- 
 meter attached to the machine indicates from two to two and a 
 half inches pressure, and to resume the process of exhausting 
 again at intervals of fifteen or thirty minutes. 
 
 Other modes of evaporating in vacuo, as practised in the arts, 
 are fully described in lire's Dictionary of Arts, and under Sugar in 
 the "Encyclopaedia of Chemistry" and " Knapp's Technology" 
 Howard's and Barry's vacuum pans are the most effective imple- 
 ments. The latter, a costly instrument, is applicable in Phar- 
 macy for making extracts upon an extensive scale. It consists 
 of a hemispherical pan with a tightly fitting cover, in the centre 
 of which is a bent tube leading into a copper spheroid of four 
 times the capacity of the pan. This tube is fitted with a stop- 
 cock, which allows a communication, at will, between the spheroid 
 and pan. Another cock, at the opposite end, is made so as to 
 couple with the conduit of the steam generator. 
 
 The liquid to be evaporated is introduced into the basin, which 
 is then to be hermetically closed and placed in a water-bath. 
 The cock connecting with the spheroid being closed, a current of 
 steam is let on, and continued until the entire expulsion of air 
 from the pan ; access of steam is then stopped by closing the 
 cocks, and a sheet of cold water applied to the exterior. A con- 
 densation of vapor ensues, and a partial vacuum is produced. 
 Communication being then opened with the caldron, uniform ex- 
 pansion of the air ensues ; and as the capacity of the spheroid is 
 four times greater than that of the pan, the latter contains only 
 one-fifth of its original amount of air. Several repetitions of this 
 manipulation produce a sufficient vacuum. The water-bath is 
 
EVAPORATION BY HEAT IN OPEN AIR. 467 
 
 then heated until the liquid within the pan commences to boil, as 
 may be seen through the small window left for the purpose, and 
 the cooling of the spheroid continued. When the liquid has 
 reached the required thickness, the operation may be discon- 
 tinued. In this way ebullition proceeds at 100 F., under a 
 pressure sixteen times less than that of air. With an air-syringe 
 attached, for removing the vapor as fast as formed, the power of 
 the apparatus would be greatly increased. 
 
 Evaporation ~by Heat in Open Air. Having already noted 
 the effects of heat in facilitating evaporation, we proceed to make 
 known its modes of application. As the boiling-points of solu- 
 tions differ, so accordingly their evaporations are effected at 
 varying temperatures. For example, aqueous or other solutions 
 of unalterable matter may be evaporated over the fire ; others, 
 which are destructible by heat, require the intervention of BATHS. 
 In whatever mode the operation is performed, the general prin- 
 ciples are the same, and whether the vessel be a porcelain capsule 
 or metallic pan, the greater its width in proportion to its depth 
 the more rapid is the evaporation. Constant agitation with a 
 stirrer is also promotive of the process. 
 
 Evaporation over Water and Saline Baths. When solutions 
 are alterable at a temperature above 212 F., the capsule or 
 containing vessel is heated over the WATER-BATH, Fig. 150. 
 
 If it requires a higher heat, but one not exceeding 300 F., 
 then the water must be replaced by a SALINE-BATH, p. 269. 
 
 Evaporation by Steam. This mode has many advantages over 
 all others, not among the least of which is that with the aid of 
 the generator or jack, Figs. 15 and 17, any number of vessels 
 may be heated simultaneously, and in any part of the laboratory, 
 it being only necessary to have conduits of sufficient length to 
 convey the steam to them, as exemplified by the steam series, 
 Fig. 18. Moreover, convenient stop-cocks allow a regulation of 
 the heat, and consequently all danger of injury to the evapora- 
 ting solution is avoided. By increasing the pressure of the steam 
 the temperature of the solution is also elevated. 
 
 Steam is applied through metallic coils placed at the bottom 
 of the containing vessels, and having an exit-pipe leading into 
 the neighboring flue, or else by means of metallic casings. This 
 latter mode, by far the best, has already been described in detail. 
 
468 EVAPORATION BY HEATED AIR. 
 
 Evaporation over Sand-baths. This mode is much used in 
 analyses and for careful evaporations, requiring temperatures 
 greater than 212, and yet not so high as those given by the 
 naked fire. The position and arrangement of the vessels are as 
 directed under the head of SAND-BATHS. 
 
 Evaporation by Heated Air. This mode is admirably adapted 
 for the inspissation of the natural juices of plants or for pre- 
 paring dry extracts. It is also applicable to the completion of 
 evaporations which have been carried as far as is safe over the 
 naked fire. Porcelain plates or panes of window-glass are the 
 vessels used, and a stove or apartment for their reception, heated 
 from 95 to 110, with a free draught passing through, are the 
 means of obtaining the required temperature. The juice evapo- 
 rates either to thin scales or else to a spongy mass, as in the case 
 of tannin extracted by ether, and as soon as it reaches dryness, 
 the plates or panes are to be withdrawn, and their contents 
 removed with a spatula. 
 
 Marcet, of Geneva, who experimented with water and alcohol, 
 gives the following interesting results of an investigation into 
 the circumstances which promote or prevent the evaporation of 
 liquids. 
 
 1. The temperature of a liquid allowed to evaporate freely in 
 an open vessel is always inferior to that of the surrounding atmo- 
 sphere. The higher the temperature of the atmosphere, the 
 greater is the difference between its temperature and that of the 
 liquid exposed to evaporation. Between 40 and 50 Centigrade, 
 the difference was found to vary from 5 to 7; between 20 and 
 25 it varied from 1J to 1J; at 12 it was 0-8 only, and be- 
 tween 3 and zero about 0-2. The explanation of this result is 
 obvious. The evaporation. of a liquid diminishing with the exter- 
 nal temperature, the cold, which is the consequence of this 
 evaporation, must diminish in the same proportion ; and if it were 
 possible to prevent evaporation altogether, the author presumes 
 that there would be no difference whatever between the tempera- 
 ture of a liquid and that of the surrounding medium. 
 
 2. The temperature of liquids, such as water and alcohol, as 
 well as the rapidity with which they evaporate, varies, all other 
 circumstances remaining the same, according to the nature of the 
 vessel in which these liquids are contained. For instance, the 
 
EVAPORATION BY HEATED AIR. 469 
 
 temperature of the surrounding atmosphere being from 15 to 
 20, water is, on the average, 0-3 warmer in an open metallic 
 vessel than in a similar one of polished porcelain, and 0-2 warmer 
 than in a similar one of glass. It is the same with alcohol. 
 Again, both water and alcohol evaporate more rapidly from a 
 porcelain vessel than from a metallic or glass vessel of precisely 
 the same size. For example, three similar vessels, one of metal, 
 the second of porcelain, and the third of glass, containing each 
 600 grains of water, having taen exposed to evaporation during 
 seven days, the temperature of the surrounding atmosphere vary- 
 ing from 20 to 25, it was found that, at the end of that time, 
 the porcelain vessel had lost 303 grains of its previous weight, 
 the metallic one 277, and the glass vessel 275-5 grains only. 
 The author enters into considerable detail as to the precautions 
 he took to make sure that these differences could not be attributed 
 to any difference in the radiating or conducting powers of the 
 vessels employed. The differences observed in the temperature 
 of liquids, according to the nature of the vessels in which they 
 are contained, depends, no doubt, on the property with which 
 these vessels appear to be endowed of accelerating or delaying 
 evaporation. It is evident that, in each case, the quantity of 
 sensible heat subtracted from the liquid, or, in other words, the 
 diminution of its temperature, must be in proportion to the quan- 
 tity of vapor formed. For instance, the fact that water and 
 alcohol are constantly colder in a porcelain vessel than in a 
 similar vessel of metal or glass, is the natural result of the more 
 rapid evaporation of these liquids from the former of these ves- 
 sels than from the two latter. The reason why a porcelain vessel 
 evaporates more freely than a metallic or glass one is far less 
 evident. The author has proved, by placing an hermetically closed 
 bottle of porcelain, containing water, under the vacuum of the air- 
 pump, that it cannot be owing to any perviousness of the sides of 
 the vessel, as he was at first inclined to suspect. 
 
 3. The influence of the mass or depth of a liquid was next exa- 
 mined. The author's experiments appear to lead to the curious 
 fact, that the rapidity with which any given liquor evaporates 
 depends not only on the extent of its surface, but also, within 
 certain limits, on its depth. He found, for instance, that with 
 two similar cylindrical porcelain vessels containing, the first a 
 
470 EVAPORATION BY HEATED AIR. 
 
 layer of water of one-twelfth of an inch in depth, and the second 
 a layer of half an inch, the evaporation from the latter exceeded 
 that of the former in the proportion of nearly 4 to 3. A similar 
 result was obtained with alcohol. If thin glass vessels were used, 
 the same increase of depth accelerated the evaporation in the 
 proportion of 6 to 5. As the author himself observes, this appa- 
 rent influence of the depth of a liquid on its evaporation may, 
 very possibly, be merely owing to the greater facility with which 
 the different layers are conveyed, the one after the other, to the 
 surface, when the liquid is of a certain depth than when it is quite 
 shallow. 
 
 4. Water containing a solution of salt in about the same pro- 
 portion of sea-water, evaporates less rapidly, and, consequently, 
 produces less cold than the same quantity of distilled water. The 
 higher the temperature of the surrounding atmosphere, the greater 
 the difference between the quantities of salt and fresh water eva- 
 porated in a given time, under similar circumstances. 
 
 5. A given quantity of water, mixed with certain pulverulent 
 substances, such as a siliceous sand, for the particles of which it 
 has but a slight adhesion, evaporates more rapidly than the same 
 quantity of distilled water alone. The fact was ascertained in 
 the following manner : The author having procured two small 
 porcelain vessels exactly of the same size, introduced into one of 
 them 300 grains of distilled water, and into the other a small 
 quantity of siliceous sand, over which 300 grains of water were 
 poured, so as not only to saturate the sand, but also to leave a 
 layer of water of about one-tenth of an inch in thickness over 
 and above its surface. At the end of five days, it was observed 
 that the water standing alone had lost 184 grains of its previous 
 weight, while the water mixed with the sand had lost no less than 
 196 grains. The average difference, resulting from a series of 
 experiments, was 7J per cent, in favor of the more rapid evapo- 
 ration of water mixed with sand compared with that of water 
 standing alone. If the experiment be made with glass or metal- 
 lic vessels, the difference is only about 4J per cent. 
 
 6. The last result which we shall mention, and which may be 
 regarded as a direct consequence of the preceding one, is the 
 following: Water mixed with sand remains habitually at a 
 slightly lower temperature than an equal surface of water stand- 
 
EVAPORATION OVER THE NAKED FIRE. 471 
 
 ing alone. The difference varies to a certain extent according to 
 the nature of the vessels in which the experiment is performed, 
 never, however, exceeding half a degree Centigrade. It is greater 
 when the comparison is made between water and wet sand placed 
 in two similar metallic vessels, than when they are placed in por- 
 celain or glass vessels ; in the latter case it seldom exceeds 0-1 
 to Q'2.Bibliotheque Universelle, 1853. 
 
 Evaporation over the Naked Fire. The tendency of many 
 substances to decomposition over fire, especially organic, even 
 when in solution, renders this mode inapplicable save when the 
 solvent and substance dissolved are both unalterable below the 
 boiling-point of the former. It is resorted to for expediting eva- 
 porations, but otherwise is far more inconvenient than steam, 
 because of its affording less facility for the regulation of the heat 
 and requiring greater attention. The containing vessel should 
 be placed over a furnace of small dimensions, and its contents 
 continually stirred with a porcelain spatula; this precaution 
 preventing decomposition or carbonization, provided the tempe- 
 rature is not allowed to exceed the boiling-point of the solvent. 
 
 In analysis and other processes, the heating implement is 
 generally the gas or spirit-lamp, Figs. 40, 41. The capsule filled 
 to about two-thirds its depth with liquid, being placed in position, 
 the flame is applied gradually and maintained just low enough to 
 prevent ebullition ; and in order to facilitate the process, and at 
 the same time to allay turbulence, it should be frequently stirred 
 with a glass rod. The same directions apply when the operation 
 is performed in a beaker glass, as is done in some analytic expe- 
 riments ; and Fig. 347 shows its position over the lamp. 
 
 A cover of white paper prevents access of dust without retard- 
 ing the process, but care must be taken that the contents of the 
 vessel be not ejected against it, thus causing a loss. 
 
 In evaporating to dryness, towards the end of the process the 
 flame must be so managed as to impart a uniform heat to all 
 parts of the thickened solution. The interposition of a very 
 thin plate of sheet-iron between the flame of the lamp and the 
 bottom of the heating vessel is an additional means of preventing 
 spirting. These precautions and constant stirring will prevent 
 the loss of particles, which is liable to occur upon the disengage- 
 ment of the last portions of liquid. If the liquid drops a powder 
 
472 CRYSTALLIZATION. 
 
 during the operation, the vessel must be inclined; and in order 
 to prevent spirting, heated above the deposit. 
 
 A platinum spatula is a very useful implement for detaching 
 any efflorescent matter which may travel up the sides of the 
 vessel. 
 
 CHAPTER XXIII. 
 
 CRYSTALLIZATION. 
 
 WHEN a body, in the act of passing from a liquid or gaseous to 
 a solid state, arranges itself in symmetrical forms, the process is 
 termed crystallization, and the parts of the body so aggregated 
 are called crystals. 
 
 By this process we can separate crystallizable from amorphous 
 substances dissolved in the same menstrua, purify crystals from 
 foreign and coloring matters, and in qualitative examinations, be 
 enabled to determine the composition of bodies by a reference to 
 the characteristics of figure. 
 
 The modes of crystallization are by FUSION, SUBLIMATION, 
 SOLUTION, and CHEMICAL REACTION. 
 
 Crystallization by Fusion. Sulphur, lead, bismuth, tin, anti- 
 mony, silver, numerous alloys, anhydrous salts, and other fusible 
 substances which are unalterable by heat, are crystallizable by 
 
 FUSION. 
 
 To this end they are melted at the lowest possible temperature, 
 and allowed to cool very gradually. As soon as a crust forms 
 upon the top, which may be readily seen by the surface becoming 
 furrowed, it must be pierced with a rod, and the still fluid por- 
 tion decanted with sufficient dexterity to prevent it from cooling 
 during the process, and at the same time from injuring the 
 crystals coating the interior of the vessel. 
 
 The liquid matter should be placed so as to be free from all 
 vibration. The greater the mass of the material and the more 
 slowly it is cooled, the more voluminous and better defined will 
 be the crystallization. 
 
 Crystallization by Sublimation. Volatile solids, as iodine, 
 
CRYSTALLIZATION FROM SOLUTION. 473 
 
 camphor, several metallic chlorides and mercurial compounds, 
 arsenic, benzoic acid, iodide of lead, &c., when heated as directed 
 in SUBLIMATION, yield vapors which, in cooling, take the form of 
 crystals. 
 
 Crystallization from Solution. When it is desired to obtain 
 a substance in crystals, it must first be liquefied or made into a 
 SOLUTION with an appropriate liquid. If, after making the solu- 
 tion, there be any insoluble residue, it must be separated by 
 FILTRATION ; and subsequently, if the solution is capable of de- 
 colorization by such means, it should be boiled with a small portion 
 of clean bone or ivory black, and again filtered. As it is the 
 almost universal law that heat increases the solvent power of 
 bodies, the solution should generally be made and clarified at the 
 boiling-point, so that the excess of matter taken up at the high 
 temperature may separate on cooling in the form of crystals. 
 
 So long as a solution is dilute it yields no crystals ; these 
 latter are only formed when the containing liquid is supersatu- 
 rated, or, in other words, holds more than it can retain in fluid 
 form ; and, consequently, in diminishing the quantity of the 
 liquid by EVAPORATION, we increase the density of that which 
 remains, and hence, upon cooling, it deposits that excess of the 
 dissolved substance, which it only held by virtue of its compa- 
 ratively high temperature. 
 
 Some substances are so easily soluble, and to such an un- 
 limited extent, that their solutions form crystals immediately 
 upon cooling; others again are taken up with such difficulty, 
 even at high heats, unless in large bulks of liquid, that although 
 exposed to prolonged ebullition, they require to be evaporated in 
 order to separate what has been dissolved. As the mode of 
 evaporating has an important influence upon the form and size 
 of crystals, we give some hints as to the proper manner of per- 
 forming it. 
 
 If large and well-defined crystals are required, the solution 
 should be subjected to spontaneous evaporation, for the more 
 slow and uniform the concentration, the more regular and gradual 
 will be the superposition of material required to make distinct 
 and large crystals. A slight addition of solution of gelatin will, 
 in some instances, it is said, give the crystals the form of plates, 
 as in the case of boracic acid. 
 
474 CRYSTALLIZATION. 
 
 The solution should be removed from the fire as soon as drops, 
 withdrawn by a glass rod and deposited upon a watch-glass or 
 clean spatula, give small crystals upon cooling. If, however, a 
 very dense crystallization is required, the concentration may be 
 continued until a pellicle forms upon the top, but then the solidi- 
 fied masses are confused and less brilliant. These essays indi- 
 cate that the liquid is evaporated to a point at which.it cannot 
 retain all of its soluble matter. The vessels are then placed 
 aside to cool gradually and uniformly, that the excess may crys- 
 tallize out of the liquid. The temperature should be regular, for 
 slight variations may alter the form of the crystals. 
 
 Bodies equally soluble in cold and hot water, as well as those 
 which are deliquescent, require a prolonged evaporation, as they 
 only crystallize from very dense solutions. 
 
 When the liquid is to be converted wholly into solid, then the 
 process is termed granulation, and is practised by concentrating 
 it to a syrupy consistence, removing the vessel from the fire and 
 stirring it constantly until the mass has cooled into granules. 
 This mode is adapted for purifying pearl-ash and converting it 
 into sal tartar, and also for graining brown sugars. 
 
 If the liquid, evaporated as above directed, becomes colored or 
 murky during the process from partial decomposition, it may be 
 treated with bone-black, and again filtered into a capsule, or other 
 vessel, previously warmed by a rinsing with hot water, so as to 
 prevent confused crystallization from sudden contact with its cold 
 surfaces. Blue stoneware capsules are far better than porcelain 
 capsules or glass beakers, as they are not only more durable, but 
 by the roughness of their interior surfaces far more promotive of 
 crystallization. Stone basins for this purpose, called crystallizers, 
 are made of all sizes, in depth greater than in breadth, and with 
 a lip to facilitate the separation of the residual liquid from the 
 crystals. This residual liquid, called the mother water, is usually 
 returned to the evaporating vessel to be further concentrated for 
 the production of a new crop of crystals, particularly if the liquid 
 has been homogeneous. 
 
 The first crop of crystals is generally purer than subsequent 
 ones, but may still not be sufficiently free from foreign salts and 
 other matters, and, therefore, require to be dissolved anew and 
 recrystallized as at first. The pure crystals are drained of their 
 
PURIFICATION OF CRYSTALS. 475 
 
 mother water by inclining the crystallizer over the evaporating 
 vessel long enough to allow all of the fluid to run off at the spout. 
 The crystals are then removed with a spatula and transferred to 
 a drainer, which is generally made of porcelain or earthenware, 
 and after the form of a saucer or funnel, Figs. 382, 383, accord- 
 Fig. 382. 
 
 ing to the quantity and nature of the crystals. Thence, they are 
 subsequently removed to the drying-frame. In the first crystal- 
 lization, the mass of impure crystals is drained upon a filter, 
 and, if necessary to free them from syrupy or dirty liquid, en- 
 closed in a cloth and pressed (Fig. 375). Sometimes, especially 
 when the crystals are no* very soluble, they may be drenched, 
 while upon the filter or drainer, with cold water, which carries 
 away much soluble impurity. This solution, if valuable, may be 
 mixed with the mother waters, and the whole, after being trans- 
 ferred to the evaporating vessel, be concentrated and again crys- 
 tallized. The crop thus obtained is very impure, and requires to 
 be drained on a cloth and pressed, and subjected to as many 
 treatments with bone-black, and renewed crystallizations, as are 
 required to remove all color. It must be remembered, however, 
 that bone-black is only used when the coloring substance is or- 
 ganic, and when the characteristic color of the crystals is light, 
 for it has no blanching action upon either organic or unorganized 
 bodies which are naturally tinted. 
 
 In recrystallizations, only as much water as is necessary to 
 effect solution should be used, so that the mother waters may be 
 as small in quantity as possible. The last mother waters being 
 incapable of yielding any more crystals, may, in some processes, 
 be reserved for other purposes ; as, for instance, making new 
 compounds. Thus, for example, the mother waters of iodide of 
 potassium may be used to precipitate iodide of mercury from the 
 bichloride of that metal, or of lead from the nitrate of lead, and 
 
476 CRYSTALLIZATION. 
 
 those of chloride of barium to obtain carbonate of baryta, upon 
 the addition of carbonate of soda. 
 
 Sometimes, however, crystallization is resorted to for the sepa- 
 ration of one substance mixed with others, which are variably 
 soluble in the same liquid, and which do not crystallize together, 
 but separate from the solvent at different stages of concentration. 
 In such case, the mother waters may contain one or more of the 
 other components of the original substance, and hence are not 
 useful for forming new compounds by PRECIPITATION. After 
 the separation of each to the fullest extent by crystallization, at 
 different temperature, the residue of liquor, unless it be of great 
 value, may be thrown away. 
 
 As before said, gradual evaporation at a uniform temperature, 
 and a perfect repose of the concentrated solution, give the most 
 perfect crystals. S8me solutions, however, crystallize less readily 
 than others, and remain even days and weeks without exhibiting 
 any sign of such tendency. In such cases, it is advisable to 
 agitate the mass slightly, or to stir it gently with a glass rod. 
 This manipulation arouses, as it were, the molecules from their 
 inertia, and frequently determines speedy crystallization. The 
 resulting crystals are generally, however, confused and dimi- 
 nutive. 
 
 To obtain large crystals from a solution which is slow in depo- 
 siting them, it is sometimes proper to add nuclei to the cold 
 solution, these consisting of well-formed large crystals of the 
 same substance. As the solution increases its density by spon- 
 taneous evaporation, the nuclei assume a large size ; but in order 
 that their enlargement may be uniform throughout, they must be 
 turned daily, so that the accumulation of matter may take place 
 on all their surfaces. 
 
 This mode, as practised in the arts, is somewhat modified. 
 The deposition surfaces are increased by inserting in the solution 
 strings as nuclei. When one solution is thus exhausted of its 
 soluble matter, the strings with their surrounding crystals are 
 transferred to as many fresh vats consecutively as are required 
 to give the crystals the proper size. In this manner, blue 
 vitriol, prussiate of potash, tartar emetic, and rock candy are 
 crystallized. 
 
 When the twine loops are replaced by slender twigs or branches 
 
CRYSTALLIZATION BY CHEMICAL REACTION. 477 
 
 of wood, and the crystals are deposited in fine flakes from bulky 
 solutions, the process is termed arborization. 
 
 Examples of arborization, where, however, crystallization is 
 accompanied by chemical or voltaic action, are furnished by the 
 various metallic trees, which are clusters of metallic flakes or 
 crystals precipitated upon the surface of a dissimilar metal sus- 
 pended in their solution. 
 
 Payen has suggested the following method of increasing the 
 size and regularity of the crystals, and especially those obtained 
 from substances soluble with difficulty. 
 
 In the apparatus employed, the liquid circulating through one 
 part dissolves the substance to be crystallized, and deposits it in 
 crystalline forms in another and cooler part. 
 
 " The arrangement consists of a flask or tubulated receiver, 
 surmounted by another similar vessel, the two being adjusted by 
 the necks, and communicating, at the lateral opening, by tubes, 
 the one with the top and the other with the bottom of a vessel 
 placed at some distance. The inverted receivers are both filled 
 with the substance to be dissolved, and the whole of the apparatus 
 with the solvent. Heat, derived from a constant and uniform 
 source, is applied to the receivers, by which a continual circula- 
 tion of the liquid is maintained, and this being saturated in the 
 most heated part of the apparatus is conveyed to the cooler part, 
 where the deposition takes place." 
 
 Crystallization may thus be made to take place slowly and 
 regularly. Payen obtained, by this means and the use of benzole 
 as the solvent, crystals of sulphur one hundred times larger than 
 those formed in the usual way. 
 
 Crystallization by Chemical Reaction. The newly-formed 
 compounds, resulting from chemical reaction, frequently assume 
 the crystalline shape. Thus, for example, antimony roasted 
 in contact with air forms crystals of antimonious acid ; chlorine 
 acting upon phosphorus produces crystals of perchloride of phos- 
 phorus. So, likewise, crystals of bicarbonate of potassa are 
 produced when carbonic acid is passed through a concentrated 
 solution of carbonate of potassa. 
 
 Silver displaced from its solutions by zinc forms a crystalline 
 deposit. Sulphate of lime precipitated by alcohol from its 
 aqueous solution also falls in crystals. Morphia, also, and other 
 
478 DESICCATION. 
 
 crystalline alkaloids, may, in like manner, be precipitated by 
 decomposing their solutions with ammonia. 
 
 CHAPTER XXIV. 
 
 DESICCATION. 
 
 THE desiccation of a substance consists in the expulsion of its 
 "moisture." The term moisture is used only in reference to 
 that variable amount of water, and sometimes, though rarely, of 
 other liquids, which it may have absorbed, or otherwise retained 
 in a state of mechanical union. The combined water, or that of 
 crystallization, of which many bodies are in part constituted, 
 exists in an entirely different form, and is not usually to be ex- 
 pelled when the drying is preliminary to analysis. When, how- 
 ever, it is desired to dehydrate a body entirely, this latter water 
 of combination is also to be dissipated. 
 
 The means of desiccation are various, and differ with the nature 
 of the substance to be dried, its quantity, and alterability by heat 
 and exposure. 
 
 DESICCATION OF SOLIDS. Undecomposable salts and any sub- 
 stances unalterable by air or heat, may be dried by FUSION. If 
 the amount of moisture is to be determined, the crucible and its 
 contents should be weighed before and after the operation, the 
 loss expressing the weight of water expelled. Those bodies, 
 however, which will not bear the heat necessary for fusion, can 
 be desiccated by EVAPORATION to dryness in a capsule, care 
 being taken to renew surfaces by constant stirring. 
 
 Those saline matters which readily yield all their water by 
 exposure may be reduced to powder or effloresced by subjecting 
 them in thin layers to a draught of dry air, which, if necessary, 
 may be moderately heated. For this purpose, as well as for that 
 of drying crystals which do not effloresce, it is necessary, in 
 manufacturing laboratories, to have a special apartment. This 
 room should be smoothly plastered within, and need not be of 
 large size. As a means of ventilation its opposite sides are 
 pierced with small holes, which, to prevent the admission of dirt, 
 
DESICCATION OF SOLIDS. 
 
 479 
 
 are covered with wire gauze. The interior is fitted with trellis 
 shelves for the support of the wooden frames, stretched over with 
 white muslin, and upon which the substance rests between or 
 upon, as may be required, folds of bibulous white paper. The 
 heat is communicated by sheet-iron flues proceeding from a stove 
 placed outside of the enclosure, or by means of steam-pipes fed 
 by the generator, Fig. 15. The temperatures should range from 
 75 to 110 F. 
 
 This apartment is also useful for pharmaceutical purposes, for 
 drying plants, roots, seeds, woods, &c. They may either be sus- 
 pended or spread in thin layers upon frames, and repeatedly 
 turned for the purpose of exposing fresh surfaces. 
 
 The air-chamber, p. 40, may, to a limited extent, be made to 
 replace this apartment, and in an experimental laboratory it is, 
 together with the means mentioned in this chapter, sufficient for 
 all purposes. 
 
 As the salts effloresced as above still retain a little water, they 
 require to be repeatedly pressed between the folds of white paper 
 until dampness ceases to be imparted to them. Sometimes a 
 previous trituration is necessary to facilitate the process. 
 
 Filters containing precipitates, after careful removal from the 
 funnel and compression between the folds of bibulous paper, may 
 be further dried in the same manner. Those, however, which 
 contain the results of analytic experiments require more careful 
 manipulation. For their treatment a copper-plate oven is often 
 used. It consists (Fig. 384) of a brass soldered copper box 7 X 
 
 Fig. 384. 
 
 9 inches, enveloped by a steam-tight jacket, in the door of which 
 are vent-holes for change of air. The water, or the olive oil 
 which is used if the substance requires a heat higher than 212 
 for its desiccation, is poured through the centre aperture at the 
 
480 DESICCATION. 
 
 top, but must not more than half fill the jacket. The lateral 
 opening is for the reception of a thermometer, which is adjusted 
 by means of a perforated cork, for facilitating the regulation of 
 the temperature. ^.^ 
 
 The watch-glasses, plates, or capsules, in which the substances 
 to be dried are placed, rest upon the perforated shelves in the 
 interior. 
 
 The thermometer will indicate with precision the temperature 
 of the bath, and care must be taken that the latter be not 
 allowed to exceed the degree above which the body to be dried 
 decomposes. 
 
 If the substance to be dried is not alterable by temperatures 
 above 212 F. to 300, they may be expeditiously dried in the 
 air-box, Fig. 385, described below, which differs from the preced- 
 
 : ' Fig. 385. 
 
 ing in receiving its heat direct from the flame, and without the 
 intermedium of a bath. It consists of a strong brass box, 6 to 8 
 inches in width and depth, with a corresponding height. In the 
 centre of the top is a circular opening, in which a thermometer is 
 adjusted by means of a cork. A wire stand in the interior serves 
 as a support for the containing vessels, and allows the drying of 
 filters in funnels, when it may be inexpedient to remove them. 
 Circular holes, in the lower and upper parts of the sides, create 
 
DESICCATION BY BATHS. 481 
 
 a circulation of air through the box, and thus promote evapo- 
 ration. 
 
 Rammelsberg's air-bath, Fig. 386, is very similar to the pre- 
 ceding, but allows the use of a tall chimney, 
 which, by determining a powerful draught 
 through the chamber, greatly expedites the 
 drying process. It consists of a cylindrical 
 copper box, six inches high by four inches 
 wide, and has a loose cover, in which is ad- 
 justed a thermometer for regulating the tem- 
 perature. Rising from the cover opposite to 
 the thermometer is the chimney, which should 
 have a height of 9 to 12 inches. One or two 
 circular openings, at the circumference and at 
 the base of the cylinder, are necessary for the 
 admission of air. 
 
 A perforated diaphragm, midway in the 
 interior, serves as a support for the crucibles, 
 watch-glasses, capsules, funnels, and other 
 vessels containing the matters to be dried. 
 
 Kemp's Thermostat. When street gas is used for heating the 
 air-baths, it is apt to give unequal temperatures, owing to the 
 variable pressure upon the service-pipes at different times. To 
 prevent this annoyance, Kemp has devised a most convenient and 
 efficient apparatus, which he properly designates a Thermostat, as 
 it regulates the supply of the gas to the burner, and of course 
 the amount of heat thus applied to the substance under process, 
 thereby insuring a constant temperature for any length of time. 
 
 This simple and ingenious apparatus will be found serviceable 
 for all operations requiring a prolonged temperature of great uni- 
 formity. The author used it successfully in promoting tedious 
 fermentations, artificial incubation, and for obtaining products of 
 the decomposition of organic bodies at fixed temperatures. The 
 use of mercury renders it available only for temperatures below 
 the boiling-point of that metal ; but by making the instrument 
 of iron and substituting fusible alloys for mercury, it becomes 
 applicable for higher degrees. 
 
 The instrument itself, shown in the following drawing, consists 
 of an air-thermometer B A of glass, and containing mercury in 
 
 31 
 
482 
 
 KEMP'S THERMOSTAT. 
 
 the lower part of the bulb A, and a portion of the stem B. A 
 tube of smaller diameter, as seen in the figure, passes down the 
 axis of the tube B, the annular space being made air-tight by a 
 
 ./'J..V'*" J ' 1 Fig. 387. 
 
 small brass stuffing-box B, which enables it to be retained at any 
 required elevation. An air-tight connection is made at c with a 
 piece of flexible caoutchouc tube, communicating with the service- 
 pipe by means of a gallows-screw. The gas entering through 
 this channel passes into the long stem of the thermometer, and 
 thence to the burner D. 
 
 In using the instrument, the bulb A must be immersed in the 
 water-bath with the substance under examination, if that means 
 of heating is employed ; and, in the case of an air-bath or hot 
 press, it must be placed in immediate vicinity of the substance, 
 so as to produce an equilibrium of temperature between the air 
 in the bulb and the surrounding atmosphere. 
 
 The inventor thus explains its mode of operation. Supposing, 
 for example, that it is required to keep an object at a tempera- 
 ture of 100 F., then the bulb of the instrument being placed 
 
 - 
 
KEMP'S THERMOSTAT. 488 
 
 contiguous to the object, a free supply of gas is allowed to flow 
 through the burner, and a flame ignited. The heat soon begins 
 to act upon the air in the bulb, causing it to expand and force 
 the mercury up the stem B ; and when it is found, by the use of 
 a common thermometer, that the heat has risen to the required 
 degree, the inner and smaller tube is to be pushed down until its 
 lower extremity reaches below the surface of the mercury. This 
 would, of course, cause the flame to be extinguished ; but, as the 
 preventive of this occurrence, a small hole is bored through the 
 inner tube above the extremity, to permit the transit of a small 
 quantity of gas to the burner. As the passage of the gas is now 
 interrupted, the source of heat is withdrawn, and the cooling in- 
 fluence of the surrounding air then causes the air contained in A 
 to contract, and the mercury in B to sink, and leave the end of 
 the internal tube uncovered. A free channel for the gas is thus 
 opened, so that, as combustion proceeds, the temperature would 
 again rise and cut off the supply ; but, in a short time, these two 
 opposing forces reach an equilibrium, and scarcely any variation 
 in the size of the flame occurs. To insure perfect contact of the 
 end of the inner tube with the mercury, the former, to the extent 
 of a half inch, is made of platinum, and amalgamated by dipping 
 it into a liquid amalgam of sodium and mercury. 
 
 Westly proposes to improve Kemp's instrument by cutting or 
 grinding off the inner tube c on one side, so as to form a long, 
 narrow slit in place of the small hole. This modification prevents 
 the sudden jerks with which the aperture otherwise opens and 
 closes. 
 
 If the extremity of the inner tube be formed into a cone, like 
 an inverted funnel, and then a portion of the side cut off, the area 
 of the aperture for the passage of the gas will form a parabola, 
 or hyperbola, as required, by which the flow of gas may be regu- 
 lated with great precision to the desired temperature, and in any 
 ratio that is needed. To insure metallic contact with the mer- 
 cury, the interior of the tube may be, for a short length, electro- 
 typed with platinum. 
 
 According to Wetherill, a glass tube may be made to replace 
 that of platinum by drawing it out at the end in such a manner 
 that the tip, to the length of three-quarters of an inch, shall have 
 a diameter of one-sixteenth of an inch. The quarter inch of the 
 
484 
 
 WETHERILL'S THERMOSTAT. 
 
 end immediately behind the tip is carefully filed down with an 
 angular file, so as to produce a fine slit. By this slight modifica- 
 tion, the extremity of the tube comes in the centre of the rising 
 column of mercury, which closes it accurately. 
 
 The drawing presents Wetherill's adaptation of the thermostat 
 to an air-bath ; the tube being shown at 2 in full size. The hole 
 a, through which the gas passes to the burner when the extremity 
 Js closed, must be only large enough to admit sufficient gas to 
 prevent the extinction of the light. The burner employed is in 
 the form of a cross, and consists of two pieces of brass tube closed 
 at the end, and united by brazing in such a manner as to leave a 
 free communication throughout the bores. The holes for the 
 exit of the gas are drilled into the upper surface with a needle. 
 A leaden weight E, cast at the centre of the cross, serves to give 
 steadiness to the burner, and at the same time sufficient elevation 
 to promote draught of air beneath. The air-bath rests upon a 
 box of four inches height, which encloses the burner; and a 
 movable opening gives access to the interior, as may be necessary ? 
 to light or examine the flame. 
 
 "Fig. 388 represents an arrangement for drying substances in 
 
 Fig. 388. 
 
 Fig. 389. 
 
 a, current of dry air produced by the efflux of water. For this 
 purpose a known weight of the substance is in- 
 troduced into the small bent glass tube (Fig. 
 389), which has also been weighed ; the body 
 of this tube being then plunged into a copper 
 water-bath 5, charged with a saturated solu- 
 tion of common salt, it is kept in its place by 
 
 a cover furnished with two apertures for the arms of the drying- 
 
DESICCATION OP EASILY ALTERABLE SUBSTANCES. 485 
 
 tube ; the wider arm is united by means of bent tubes and a 
 caoutchouc connector with the U-shaped tube, and containing 
 fragments of chloride of calcium, and the narrow end is con- 
 nected with a bent tube, which passes through the cork of the 
 bottle A nearly down to its bottom. This cork must fit the bottle 
 perfectly air-tight, and all the joints and connections of the whole 
 apparatus must be perfect. The bottle A is filled with water, 
 which, on turning the stop-cock s, flows out in a small stream, its 
 place being supplied by the air drawn through c, and which 
 becomes dried during its passage through the chloride of calcium, 
 tube b. The bath is charged with water, a saturated solution of 
 common salt, or of chloride of calcium, according to the degree 
 of heat required, and it is kept boiling by means of a spirit or 
 gas lamp placed underneath." 
 
 Desiccation of easily Alterable Substances. It has already 
 been said that the power of absorbing and retaining moisture 
 varies in different bodies. This property renders the use of 
 those which have it in the greatest degree available for the drying 
 of others which are deficient in it. The substances subjected to 
 this mode of drying are mostly organic bodies, and those readily 
 alterable by heat or exposure, but which yield their moisture 
 much below 212 F. 
 
 A very simple method of accomplishing this kind of desiccation 
 is to suspend the substance in a beaker glass 
 b, over a large volume of sulphuric acid 0, 
 Fig. 390. The rim of the glass is ground for 
 the purpose of making a tight joint with the 
 ground-glass plate cover d, which has a hole 
 in the centre for the support of a cork, with 
 the tray and wires e suspended to it. Upon 
 this tray rests the watch-glass or capsule c, 
 which contains the substance under process. 
 The rim should be greased previous to placing 
 the cover upon it, so as to render the connection air-tight. 
 
 The sulphuric acid absorbs the moisture as fast as it arises 
 from the substances, and thus maintains constant dryness of the 
 internal atmosphere. When the substance has ceased to lose 
 weight, the operation is finished. 
 
486 DESICCATION OF EASILY ALTERABLE SUBSTANCES. 
 
 Another arrangement for the same purpose consists of a large 
 bell glass, fitting accurately upon a ground-glass plate or bed. 
 Within is a shallow saucer 6, containing dry chloride of calcium, 
 strong sulphuric acid, or other highly absorbent material, and 
 over it a perforated glass support , upon which rest the capsules, 
 crucibles, beaker, watch-glass, or other containing vessels. Fig. 
 391 exhibits the whole arrangement. The rim of the bell, as also 
 
 Fig. 391. 
 
 that part of the plate which it touches, are to be greased, in order 
 to make the joint hermetical. The material thus exposed to dry 
 air continues to lose moisture until all has been expelled, or until 
 the absorbent matter has become saturated; in such case the 
 latter must be replaced with a fresh quantity. 
 
 By substituting the bed of an air-pump for the glass disk as a 
 support for the other parts of the apparatus, otherwise arranged 
 exactly as above described and shown in the figure, and increasing 
 the evaporation by exhausting the air, desiccation proceeds much 
 more rapidly and effectually. A partial vacuum being thus pro- 
 duced the drying substance liberates its aqueous vapor freely, 
 new portions being given off as soon as those which preceded 
 them are condensed by the absorbent in the saucer, which is 
 usually, in these cases, fused chloride of calcium or strong sul- 
 phuric acid, those agents absorbing watery vapors perhaps to a 
 greater extent than any other. The process is thus continued 
 until complete desiccation of the substance and saturation of the 
 absorbent material ensue, the latter being renewed as often as 
 may be necessary. 
 
DESICCATION IN VACUO, 
 
 487 
 
 Fig. 392. 
 
 If the eliminated vapors are corrosive, it is advisable to modify 
 the arrangement, so that they may be neutralized as fast as gene- 
 rated, otherwise the metallic surfaces of the air-pump will be 
 injured. A suitable apparatus is shown in Fig. 392. It is an 
 inverted bell glass, fitted at its neck with a 
 stop-cock, by which it connects with a tube 
 containing pumice-stone impregnated with 
 acid or alkali, according to the nature of the 
 vapors to be absorbed. The substance to 
 be dried and the absorbent or hygroscopic 
 body are arranged within the bell in the 
 usual manner. The latter is then greased 
 at its edges, hermetically covered with a 
 ground-glass plate, and exhausted of air by 
 a syringe coupled with the further end of the drying or chlorcal- 
 cium tube e. 
 
 By having a bed of ground-glass instead of metal, and de- 
 tached from the pump or syringe, and made to communicate with 
 it by flexible lead pipe and gallows-screws only when exhaustion 
 is required, an apparatus is made, which, as represented in Fig. 
 391, becomes available for all the purposes of evaporation and 
 desiccation. 
 
 Another mode of drying alterable and fixed substances in vacuo 
 is shown by the arrangement, Fig. 393, which effects a repeated 
 change of air. It consists of a copper cylinder box, soldered 
 
 Fig. 393. 
 
 with brass, having two apertures in its top, one, g, for the re- 
 ception of a thermometer by which to regulate the temperature, 
 and the other for a glass tube e, the recipient of the substance to 
 
488 DESICCATION OF LIQUIDS. 
 
 be dried. This tube is connected by means of a smaller glass 
 tube i, tightly adjusted in perforated corks with the chloride of 
 calcium tube d, and thence also with the exhausting syringe 5. 
 Heat being applied to the bath by means of a small furnace or 
 gas lamp, a partial vacuum, is then produced by several strokes 
 of the syringe piston. In a few moments air is to be admitted 
 through the cocks c and a, and this exhaustion and airing is to 
 be repeated at occasional intervals, the air in its transit being 
 deprived of all moisture by the chloride of calcium. When it is 
 desired to replace atmospheric air by carbonic acid, hydrogen, or 
 other gas, it may be introduced by connecting the gasometer, 
 containing the required gas, by suitable couplings with the same 
 apparatus. 
 
 DESICCATION OF LIQUIDS. Desiccation properly means the 
 freeing of a body, capable of existing in a dry state, from acci- 
 dental moisture. But, for the sake of uniformity of description, 
 we have applied the term also to the separation, from fluids, of 
 water, which is the ordinary source of moisture. This is usually 
 done by the agitation with the liquid of some absorbent material, 
 which either unites with the water, forming a stratum of different 
 density capable of being separated by filtration or decantation ; 
 or else combines with it so firmly that the fluid, which is usually 
 more volatile, can be separated by distillation. 
 
 Thus alcohol and other spirits are rectified by distillation over 
 carbonate of potassa, chloride of calcium, or free lime, it being 
 only necessary to stop the process as soon as the liquid comes 
 over slowly, which indicates that all the pure spirit has passed. 
 Agitation of ether with any of the same absorbents produces 
 similar results. 
 
 For analytic purposes, and in minute experiments, accidental 
 moisture may be expelled from liquids less volatile, by exposing 
 them in open vessels under the receiver of an air-pump, as de- 
 scribed for solids in the preceding paragraphs. 
 
 DESICCATION OF GASES. Nearly all gases in the course of 
 elimination become involved with more or less moisture, from 
 which it is frequently desirable to separate them previous to their 
 application to chemical reaction. For this purpose they are 
 passed over some highly absorbent material, such as dried chloride 
 of calcium, quicklime, or sulphuric acid. 
 
DESICCATION OF GASES. 439 
 
 The simplest arrangement for the purpose is given at Fig. 218 
 which exhbits a straight tube d d, containing the dried chloride' 
 of calcium, adapted at one end by means of a perforated cork 
 with the gas generator A, and at the other, in like manner, with 
 a disengagement-tube ee . The gas in its transit through the 
 chlorcalcium tube is relieved of its moisture. This tube varies in 
 me from half to one inch diameter, and eight to twelve inches 
 length, according to the quantity of gas to be desiccated. The 
 chloride of calcium can be replaced by quicklime, potassa or 
 pumice-stone impregnated with sulphuric acid, as the nature of 
 the gas may require ; but in either case the solid material should 
 be m small lumps. The water formed during the process collects 
 in this tube. 
 
 Liebig uses the drying-tube of such a form as is shown at Fig. 
 394. It differs from the above in having a bulb, and in being 
 
 Fig. 394. 
 
 drawn out at one end to a fine 'tube, thus leaving but one aper- 
 ture to be corked. Lumps of absorbent matter are placed in the 
 bulb, and coarse powder of the same substance in the long part, 
 each end of which is very loosely plugged with raw cotton to 
 prevent the exit of particles. 
 
 For small operations, the bent form, Fig. 395, is most conve- 
 nient, as it is easily adjusted to the mouth of 
 the bottle without the necessity of multiply- Fig. 395. 
 
 ing joints. The bulbs, in these two latter Qhaaa 
 tubes, serve also as wells for the reception of f 
 the condensed vapor. 
 
 Dumas's vertical drying-tube, designed for the desiccation of 
 large quantities of very moist gas, is so constructed that the con- 
 densed vapor instead of remaining in contact with the pumice, 
 and thus impairing its absorbent power, will be deposited in the 
 lower part. The tube leading from the generating vessel is 
 adapted by means of a perforated cork to a lateral tubulure 
 at the base. The disengagement-tube is similarly adapted to 
 the top. 
 
 The selection of the drying, or hygroscopic material, must, as 
 
 
490 DESICCATION OF GASES. 
 
 before said, be made with a regard to the nature of the gas ; thus, 
 for example, quicklime should never, for obvious reasons, be used 
 for desiccating chlorine, or other gases which combine with it 
 chemically ; for the drying of nearly all such gases an acid body 
 may be employed, and pumice-stone, in lumps of about the size 
 of half of a pea, impregnated with sulphuric acid, is very service- 
 able, as it presents a large extent of surface. For this purpose, 
 however, the pumice must be freed from all the chlorides which 
 it contains, otherwise the sulphuric acid will disengage muriatic 
 acid, possibly to the great detriment of the gas which is under- 
 going drying. The best way is to pulverize and moisten it with 
 sulphuric acid, and subject it to calcination in a crucible. When, 
 after constant stirring, it ceases to disengage acid vapors, the 
 operation is finished. 
 
 Anhydrous phosphoric acid is also occasionally employed as a 
 drier, but only in very nice experiments. It is mixed with clean 
 asbestos, which occupies the same position in the tube as any of 
 the other absorbents. 
 
 As a means of perfect desiccation it is often required to com- 
 bine the absorbent powers of two different materials in one appa- 
 ratus, and for this purpose the U-form of drying-tube is most 
 convenient. It presents a large extent of surface in a limited 
 space. There is, however, a disadvantage in arranging and 
 adjusting its parts firmly together, and also in the necessity of 
 occasionally renewing the hygroscopic substance more frequently 
 than in the straight tubes. 
 
 Fig. 396 exhibits a proper arrangement of the U-tubes for the 
 
 Fig. 396. 
 
 desiccation of gas. By this mode the gas may be introduced 
 directly from the generating vessel, as shown at Fig. 218, or from 
 
PRECIPITATION. 491 
 
 a gas bag or gasometer as seen in the preceding drawing. The 
 latter communicates with a pair of U-shaped glass tubes, which 
 are connected together by means of bent tubes, perforated corks, 
 and flexible india-rubber joints. In one of their legs is placed 
 dried chloride of calcium, and in the opposite one asbestos, or 
 lumps of pumice-stone, impregnated with sulphuric acid. The 
 reservoir on the top of the gasometer being filled with water, and 
 its pressure applied by opening the cocks, a stream of gas is 
 gradually expelled, and in its transit through the tubes is freed 
 from its moisture by the absorbents. 
 
 CHAPTER XXV. 
 
 PRECIPITATION. 
 
 THIS process is employed for the immediate separation of a 
 body in the solid state, both from mechanico-chemical and simple 
 solutions. The reagent, which is used to produce the action, is 
 termed the precipitant, and the resulting deposit the precipitate. 
 
 Bodies, in some instances, may be precipitated unaltered, but 
 in most cases, being the result of chemical reaction, are modified 
 or entirely changed in their nature. Thus, for example, sulphate 
 of lime may be precipitated from its simple aqueous solution by 
 alcohol ; this latter, by union with the water, forming a liquid 
 in which that salt is insoluble. For like reasons, the resins are 
 precipitated from alcoholic solutions by water ; and gutta-percha 
 from solution in chloroform by ether. If, however, carbonate 
 of soda or other soluble carbonate is substituted for the alcohol, 
 in the instance of sulphate of lime, then the original combina- 
 tion is broken up by the action of double elective affinity, an 
 exchange of bases taking place, and insoluble carbonate of lime 
 precipitating instead of the unaltered sulphate, as in the instance 
 with alcohol. So, also, an analogous result would ensue by virtue 
 of simple elective affinity if soda is used instead of the carbonate, 
 the lime then partially falling in a free state, having been de- 
 prived of its sulphuric acid by the caustic alkali. 
 
 The consistence of the precipitate and its form and color vary 
 with the nature of the solutions, and the rapidity with which it 
 
492 PRECIPITATION. 
 
 is produced. These distinctive features serve as characteristics 
 by which, in analysis, the presence of certain bodies is deter- 
 mined. 
 
 The precipitate is differently termed according to its appear- 
 ance. It is flocculent when it falls in small flakes or flocculse, 
 like those produced by ammonia in solutions of peroxide of iron ; 
 pulverulent, when in fine powder and compact, like the sulphates 
 of lead or of baryta ; granular, if deposited in minute irregular 
 molecules ; crystalline, when it subsides in minute crystals, as the 
 bitartrate of potassa, sulphates of silver and of lime ; curdy, when 
 cheesy, like that thrown down by chloride of sodium from nitrate 
 of silver, and gelatinous, when of the consistence of jelly, as 
 alumina freshly separated from alum by carbonate of potassa. 
 Precipitating Vessels. The most convenient vessels, used in 
 analysis, are beaker glasses, or wide-mouth 
 Fig. 397. flasks, the latter being used only when the 
 
 process is to be practised upon the boiling 
 liquid. When solutions are precipitated, 
 especially for the purpose of collecting the 
 precipitates, the form of the vessel may be 
 that of the one in the drawing, Fig. 397, 
 which insures the subsidence of all the deposit, 
 and prevents particles from adhering to the 
 sides. They may be of glass or blue stoneware, according to 
 the amount of liquid under process. 
 
 In chemical investigations, test-tubes are the most convenient 
 implements. They permit the operator to use minute quantities, 
 and they are readily heated and shaken. As a precipitate is, in 
 some instances, not perceptible for some hours, especially in dilute 
 solutions, sufficient time should be allowed to elapse before de- 
 ciding upon the reaction of a precipitant upon a solution. 
 
 Directions for Precipitating. Both the material and reagent 
 must be in solution and separately clarified by filtration before 
 being commingled, otherwise the suspended matters will subside 
 with the precipitate. As heat generally promotes the reaction 
 and the subsidence of the precipitate, the solution should, in such 
 cases, be warmed, or even made hot, and the reagent cautiously 
 added during continual stirring with a glass rod, so that all parts 
 of the liquid may be brought in contact. The vessel is then set 
 
DECANTATION FILTRATION. 493 
 
 aside upon a sand-bath, or in a warm place, until the deposition 
 of the precipitate has left the supernatant liquor clear. A few 
 more drops of precipitant are then added, and, if all the matter 
 has been thrown down, they will produce neither precipitate nor 
 cloudiness ; but if a portion still remains in solution, still more of 
 the reagent must be added. The addition of the reagent or pre- 
 cipitant must be gradual, for besides the waste of material and 
 inconvenience of washing it out, an excess, in certain instances, 
 redissolves the precipitate. As soon as a drop or two of reagent 
 ceases to give cloudiness or precipitate in its descent through the 
 supernatant liquid of the settled solution, its addition must be 
 discontinued and the vessel placed aside, and, after sufficient 
 repose, subjected to DECANTATION or FILTRATION to separate the 
 solid from the liquid portion, the latter of which is also usually 
 to be reserved in analysis or when it is of value, as it may con- 
 tain other newly-formed compounds dissolved in the menstruum 
 employed. 
 
 When the precipitate about to be formed is somewhat soluble 
 in the liquid of the original solution, the amount of that liquid 
 must be diminished by evaporation, and the precipitation effected 
 in a concentrated solution ; for example, in the reaction of solu- 
 tions of strontia with sulphuric acid or soluble sulphates. 
 
 Metals may be precipitated from their solution by other metals 
 having a greater affinity for oxygen than is possessed by those in 
 combination ; thus copper may be precipitated from its sulphate 
 by iron, lead from the nitrate by zinc, and silver, arsenic, and 
 mercury, from their solutions by copper. A slight acidulation 
 of the liquid facilitates the process, and the metallic strips used 
 as reagents must be clean and bright. 
 
 Metals are also precipitated by voltaic action, a familiar in- 
 stance of which is the art of plating by GALVANISM. 
 
 CHAPTER XXVI. 
 
 DECANTATION FILTRATION. 
 
 Precipitates, which are substances deposited by any means 
 from liquids in which they have been dissolved or chemically 
 
494 . POURING. 
 
 combined, may be separated either by decantation or filtration. 
 The first mode is applicable to those solids which are of much 
 greater density than the menstrua containing them, and which 
 readily and rapidly subside, forming heavy compact deposits. In 
 delicate experiments, however, and in all cases where the liquid 
 is turbid and deposits its suspended matter reluctantly, the latter 
 plan is the most appropriate. 
 
 Besides being a process subsequent to PRECIPITATION, for the 
 separation of the clear supernatant liquor from the subsident 
 matter, decantation is also useful in LEVIGATION. For WASHING 
 precipitates, which require a large amount of water, or frequent 
 renewals of the wash waters, it is much more convenient than 
 filtration. This latter mode, however, must, as before said, be 
 always adhered to in analyses, and when the precipitate is light 
 and apt to be disturbed during decantation. 
 
 Decantation from small vessels in nice experiments is practised 
 by gently inclining the vessel, whether it be a capsule, as at Fig. 
 398, or a beaker glass, Fig. 399, and allowing the liquid to run 
 
 Fig. 398. Fig. 399. 
 
 down in a continuous stream along a glass rod placed against its 
 rim or edge. This operation of pouring requires a degree of 
 dexterity which is indispensable in analytic operations in order 
 to avoid loss of material. The exact position of the rod is shown 
 in the figures. When the pouring is completed, the rod should 
 be tilted upwards for a moment, so as to prevent the loss of ad- 
 herent drops, and immediately returned to the vessel, the edge 
 of which should be slightly greased so as to effectually prevent 
 any particle of liquid from passing over. These precautions are 
 only necessary in the decantation and filtration of liquids, during 
 analytic processes ; so much care being unnecessary in less im- 
 
Fig. 400. 
 
 SYPHONS. 495 
 
 portant manipulations, as it is of little consequence if the liquid 
 does carry over a little of the precipitate or suffers a slight loss. 
 If the bulk of liquid is very small, it may be removed with 
 pipettes, Figs. 106, 109, p. 199; for larger quantities a syphon is 
 requisite. This implement may be of glass or lead tubes, the 
 former being cleanly and of more general application than the 
 latter. The shapes given in the drawings refer to those of either 
 material, 
 
 Syphons. The most simple form of syphon, Fig. 400, is 
 similar to an inverted V, with its opposite 
 branches of unequal length. The long leg 
 may be from 12 to 20 inches in length, the 
 shorter one proportionably less. The clear 
 diameter is from an eighth to a half inch, 
 according to the extent of the operation. 
 
 This syphon is inserted and filled with 
 water or any other liquid which is without 
 action upon that in the vessel ; the mouth of 
 the longer leg is then closed with the finger, 
 and the shorter branch introduced, mouth 
 downwards, into the liquid to be decanted, 
 until it nearly reaches to the level of the pre- 
 cipitate without disturbing it. Upon remov- 
 ing the finger, the liquid runs out in a con- 
 tinuous stream, and may be almost wholly drawn off by slightly 
 inclining the vessel. 
 
 The rationale of the operation is as follows : When the short 
 leg of the syphon is dipped into water the liquid mounts into the 
 tube as high as the surface of that which is in the containing 
 vessel. Now, the weight of the atmosphere bears equally upon 
 the surface of that in the vessel and in the syphon, but if the 
 elastic force of the internal air is removed or diminished by suc- 
 tion with the mouth at the other end, or by having previously 
 filled the syphon with water, the liquid runs over, and as the 
 weight of the column of water in the long leg is greater than 
 that in the short one, the flow will be continuous while the mouth 
 of the short leg is immersed in liquid, for no air can enter to pro- 
 duce an interruption. 
 
 If the liquid is not injurious or unpleasant to the taste, the 
 
496 
 
 SYPHONS. 
 
 Fig. 401. 
 
 syphon may be inserted in the liquid without previous filling, 
 suction with the mouth at the long end drawing it over. 
 
 For the decantation of caustic liquids the syphon is furnished 
 with a lateral tube, as shown in Fig. 401, 
 which serves as a protection to the mouth. 
 Its application is similar to that of the one 
 described above (p. 495) ; the short leg 
 is dipped into the liquid to be decanted, 
 the lower end closed with the finger, and 
 suction practised at the orifice of the sup- 
 plementary tube until the air is removed 
 and the liquid runs over and almost reaches 
 the mouth, when the decantation goes on 
 continuously after the withdrawal of the 
 mouth and finger. 
 
 The annexed drawing, Fig. 402, exhibits 
 these syphons in operation. 
 
 A length of cotton wick doubled in 
 syphon form, and having its short end immersed in the liquid, 
 also acts as a syphon, but is much slower in its operation. 
 
 Fig. 402. 
 
 s Q 
 
 Fig. 403. 
 
 Coffee's syphon, Figs. 403, 404, which may be made of either 
 glass or metal, after the forms presented by the drawings, are 
 much more convenient than either of the preceding patterns, as 
 they deliver the clear liquid without the least inconvenience to 
 the operator. 
 
SYPHONS. 
 
 497 
 
 It is made to work by closing the cock, compressing the india- 
 rubber ball, which forms a cap to the lateral tube, and quickly 
 immersing the short leg in the liquid to be drawn off. The hand 
 being removed from the ball causes the latter to resume its shape, 
 and, consequently, a partial vacuum in the tube, which is imme- 
 
 Fig. 404. 
 
 diately supplied by the liquid running up to fill it, under the 
 outward pressure of the air, as far as the bend, and therefore 
 when the cock is opened, it drops by the force of gravitation, and 
 flows off in a continuous stream, as long as the mouth of the short 
 leg is covered by it. 
 
 The use of the syphon allows the separation of the liquid with- 
 out disturbance of the settled matter, but as the latter still retains 
 more or less fluid which cannot be separated in this way, it may 
 be thrown upon a filter, and, in large operations, even subjected 
 to pressure in cloths, as directed at p. 460. 
 
 FILTRATION. The mode most commonly resorted to, for sepa- 
 rating solid substances from liquids in which they are suspended, 
 is that of filtration, and it is also occasionally but rarely used 
 for the purpose of disuniting liquids. The process consists in 
 passing the mixture through suitable media of sufficient porosity 
 to allow the transit of the liquid portions while they intercept 
 
 32 
 
498 FILTRATION THROUGH PAPER. 
 
 any solid particles. For the separation of liquids the texture of 
 the medium must be such that it is penetrable by or attractive of 
 the one, but impervious to the other, of them, as it is upon this 
 that the success of the operation depends ; thus, for example, 
 moistened paper will allow the passage of water, but not of oil. 
 
 Paper, brown muslin, linen, crash, woollen and canton flannel, 
 felt, raw cotton, sand, asbestos, crushed quartz, bone-black, each 
 and all have their appropriate application as media, and when 
 thus used are all styled filters or strainers ; the first title being 
 almost exclusively applied to those of paper supported upon 
 funnels, while the latter is limited to the other textures or bodies 
 which are either suspended upon frames for pharmaceutical ope- 
 rations or deposited in proper vessels. 
 
 This process is of equal importance in chemical and pharma- 
 ceutical operations. In analysis it enables us to separate preci- 
 pitates or insoluble residue from liquids, and to obtain each free 
 from particles of the other, an indispensable condition where 
 both are to be further acted upon for obtaining accurate results; 
 while, in ordinary operations, we can by its aid free liquids from 
 dirt and other foreign matters, and render them transparent. 
 
 FILTRATION THROUGH PAPER. Paper is more generally used, 
 particularly in delicate experiments, than any other medium. It 
 is advisable always to use that which is white, 1 for it contains no 
 coloring matter to deteriorate the liquid which traverses it. 
 Moreover, it should be free from saline impurities which are 
 soluble in acid or alkaline liquids, otherwise the accuracy of 
 analytic results may be materially interfered with. 
 
 The laboratory should be provided with two qualities of paper, 
 one of fine quality for nice investigations, and another somewhat 
 inferior for the less important processes. There are certain 
 conditions requisite in both kinds. They should be unsized, 
 yet strong, and while sufficiently porous to allow the ready pas- 
 sage of the liquid, compact enough in texture to retain all the 
 solid portions'. 
 
 " German filtering paper" answers very well for all general 
 purposes ; but for analytic investigations that known as " Swe- 
 
 1 A porous kind of thick brown paper is made from a mixture of woollen and 
 other rags for filtering tinctures and the coarser liquids of an aqueous or spirituous 
 
 nature. 
 
FILTRATION THROUGH PAPER. 
 
 499 
 
 d sh fUenng paper best. Being made expressly for the pur- 
 pose and of purified rags, it is free from lime, copper, and salts, 
 winch have to be removed from other paper by treatment with 
 pure hydrochloric acid and repeated rinsings in distilled water 
 before it becomes fit for such uses. 
 
 The Swedish paper is whiter and thinner than the German 
 and is made with great care; and leaves by incineration only 
 ***** of its weight of ashes, an important point in analyses where 
 the amount and nature of the ashes left by the paper require to 
 be considered. 
 
 The paper drawer should be kept always supplied with a stock 
 of filters of all the required sizes. The use of the Swedish paper 
 should be limited to the filtration of finely divided precipitates. 
 The greater porosity of the German renders it more applicable 
 for rapid filtration, and as it is much less expensive, all large 
 filters should be formed of it. 
 
 The filters must be circular, and cut by tin patterns, which 
 should consist of different sizes of 2J, 3, 3}, 4J, 6, 7J, 9, and 
 12 inches in diameter. This mode of cutting different sized filters 
 from one sheet of paper is economical, and saves the waste which 
 would be occasioned by indiscriminate use of the paper, while 
 many serious delays may be prevented by having a supply always 
 at hand. 
 
 The ashes of the piece of Swedish filter of each size must be 
 determined by incinerating one and accurately weighing the resi- 
 due, and engraving its weight upon the tin pattern by which it 
 is formed. Thus, in analyses, we can know by reference to the 
 figures the amount of fixed matter (ash) in each particular size. 
 
 The supports for these circular filters, folded into conical form 
 as hereafter directed, are funnels, which vary in material and 
 form according to the nature of the operation. They may be 
 of glass, porcelain, or stoneware. The first, free from lead, are 
 of almost general application for analytic purposes, and the latter 
 two for pharmaceutical. Funnels of metal are seldom required 
 in the laboratory, a very few instances only demanding the use 
 of lead or platinum. 
 
 The glass funnels should be made with straight sides, inclining 
 to an angle of about 60. This shape, Fig. 405, is indispensable 
 for the smaller funnels used in analyses, as it forms in its inte- 
 
500 FUNNELS. 
 
 rior a true cone, which allows the admission of a larger amount 
 of liquid in a small space. The pint funnels, and those of still 
 larger size, may have an inclination of ten 
 Fi g- 405 - degrees less, but if their section has not 
 
 nearly the form of an equilateral triangle, 
 the filters fit badly and work imperfectly. 
 The funnel should be slightly round at the 
 shoulder a, where the apex of the conical 
 filter rests ; and, moreover, the end of the 
 barrel c ought to be cut at an angle of 30, 
 so as to present an oblique termination, as 
 these points promote filtration. 
 
 The laboratory must be supplied with a 
 
 series of funnels, ranging as follows, 1, 1}, 2, 2J, 3J, 4J, 5J, and 
 6J inches in the greatest diameter of the body 5. Of the smaller 
 sizes, it will be well to have duplicates or triplicates as they are 
 the most frequently employed. The stock is not complete with- 
 out one or two miniature funnels of thin glass for filtering into 
 test-tubes in qualitative investigations ; and one or two of con- 
 venient size with long barrels c, for charging retorts and deep 
 vessels. 
 
 Sometimes the glass funnels are ground at the rim, so as to be 
 tightly closed by a glass disk, but being ex- 
 Fig. 406. pensive, they are only used in rare instances. 
 Funnels are sometimes made of porcelain 
 with longitudinal ribs in the interior of the 
 body, as shown at Fig. 406, for preventing 
 the adhesion of the filter to the sides in the 
 filtration of large quantities of bulky precipi- 
 tates. The object is, however, not effected 
 by th-ese means, for the paper sinks into the 
 channels and adheres to the surface, and still 
 retards the passage of the liquid. A better way will be to use 
 the plaited filters, Fig. 416. 
 
 Funnels are also made of porcelain, and more seldom of stone- 
 ware. They are less fragile, and more applicable to the filtration 
 of very acid and corrosive liquids, and some other few purposes, 
 than those of glass ; but those of porcelain are not less costly. 
 The form of those usually found in the market are shown in the 
 
FUNNELS. 
 
 501 
 
 annexed drawing. They are all glazed throughout and made 
 very strong, and those used for transferring liquids from one 
 vessel to another have the convenience of handles. In this 
 respect they are preferable to the glass vessels, which by fre- 
 quent rough handling are more apt to be broken. Fig. 407 ex- 
 hibits the form used for acids, and Fig. 408 the same funnel 
 ribbed in its interior. Figs. 409 and 410 present the less conve< 
 
 Fig. 407. 
 
 Fig. 408. 
 
 Fig. 409. 
 
 nient globular shape. Those shown at Figs. 411 and 412, cul- 
 lendered at the base, are the most convenient of all, being very 
 useful for draining crystals, for the filtration of viscous solutions 
 through cloth filters, and for small operations of lixiviation. 
 
 Separating Funnels. In addition to the above there are two 
 other kinds of funnels used for separating liquids which have no 
 
 Fig. 413. 
 
 Fig. 414. 
 
 chemical affinity, and differ in 
 
 stop-cocks in their barrels, as shown in F.gs. 413 and 414; and 
 
502 
 
 FILTERS FOLDED AND INTRODUCED IN FUNNELS. 
 
 one is stoppered also at the top to prevent evaporation when vola- 
 tile liquids are under process. 
 
 The mixed liquids of oil and water, or ether and water, for in- 
 stance, are poured in the mouth, and after sufficient repose for 
 the deposition of the heavier of the two, it can be drawn off by 
 opening the stop-cock, which may be immediately closed as soon 
 as all has passed. The lighter liquid which is thus retained may 
 afterwards be transferred in the same way to another bottle. 
 
 Filters Folded and introduced into Funnels. Two kinds of 
 filters are generally employed, the plain, Fig. 415, and the plaited, 
 Fig. 416. The former are used in analyses and whenever the 
 
 Fig. 415. 
 
 Fig. 416. 
 
 suspended or precipitated matters of a liquid are to be preserved. 
 It is almost impossible to entirely remove the solid matter from 
 the folds of a plaited filter, consequently such are chiefly appli- 
 cable for the filtration of bulky precipitates from large quantities 
 of liquid. This mode of folding a filter prevents its close adhe- 
 sion to the glass, and greatly expedites the process by increasing 
 the surface, and by allowing a bubble of air to ascend in the fold 
 every time that a drop of liquid descends from the filter. 
 
 The plain filters are folded as follows : 
 
 " When a filtration is to be performed, one of these circular 
 
 Fig. 418. 
 
 papers of the proper size is selected (Fig. 417), and then doubled 
 

 PLAIN AND PLAITED FUNNELS. 
 
 503 
 
 over one of its diameters (a b, Figs. 41T and 418), and then over 
 the radius ( e e, Figs. 418 and 419) perpendicular to the first dia- 
 meter, so as to form a quadrant. One of the folds is then opened, 
 
 Fig. 419. Fig. 420. Fig. 481. 
 
 ' 
 
 forming a hollow cone, as represented in Fig. 421, which will fit 
 accurately in the funnel, if the sides of the latter form an angle 
 of 60. If the angle be greater or smaller, it is necessary to 
 double the filter the second time over another radius (<?/, Figs. 
 417 and 420), not perpendicular to the first diameter, and then 
 open the large or small fold (a cf 9 orbcf 9 Fig. 420) according 
 to the angle of the funnel, and this repeated until a coincidence 
 of the filter with the inside of the funnel is effected." 
 
 To form the plaited filter, take a square of paper and fold it 
 diagonally, as in Fig. 422 ; turn A upon B to obtain the crease E, 
 and open it ; then double A upon E in the same direction, to make 
 the plait F, and double the plait A back upon F, so as to form the 
 crease G, and holding this plait between the fingers make the fold 
 between F and D. Divide the spaces between E B and B D in the 
 same manner. 
 
 The filters, as above made, after having their folds opened, as 
 at Figs. 415 and 416, are placed in the funnels, and so adjusted 
 as to fit nicely to the sides. In order to secure an uninterrupted 
 flow of the liquid, and to prevent the breaking of the filter, the 
 apex must not extend too far into the barrel of the funnel. 
 Moreover, the filter should be a little smaller than the funnel, for 
 
504 
 
 SUPPORTS FOR FUNNELS. 
 
 if it reaches to the rim, evaporation of the liquid ensues from the 
 edges, and thus, in analyses, may be a source of error. 
 
 The proper position of the plain filter in the funnel is shown at 
 Fig. 424, and that of a plaited one at Fig. 423. 
 
 In using large funnels the filter maybe supported by a plug 
 of raw cotton placed in the barrel at its junction with the body. 
 
 Fig. 423. 
 
 Fig. 424. 
 
 The usual support for funnels is the convenient portable stand, 
 Fig. 424. It consists of a wooden upright >, screwed into a 
 wooden bed-plate. The arm a, which it carries, has a circular 
 aperture sloping inwardly and downwards, which supports the 
 funnel steadily in its place. The screw c allows the elevation or 
 depression of this arm at will, as the height of the receiving- 
 vessel beneath may require. 
 
 When the funnel is used for transferring or filtering liquids 
 into narrow-mouthed vessels, its barrel may be supported by 
 their neck ; but in order to secure a free passage of air, it should 
 be fluted externally, or else have a chip or two placed between it 
 and the inner sides of the neck, otherwise the confined air will 
 retard the process, and possibly force the filtered liquid, with a 
 hissing sound, up and over the sides and mouth of the bottle. 
 
 After having adjusted the filter to the funnel, the latter is 
 placed in the stand, so that its barrel may rest against the inner 
 wall of the receiving-vessel beneath. This position allows the 
 falling fluid to trickle quietly down the sides, and prevents the 
 

 SUPPORTS FOR FUNNELS. 505 
 
 splashing which would occur if it fell directly upon the surface of 
 the liquid, and also obviates the necessity of sinking the harrel 
 far into the receiver. 
 
 The filtering apparatus having been thus arranged, the filter 
 is to be moistened with distilled water from the bottle (Fig. 355) 
 or when the nature of the process requires, with a portion of the 
 solvent liquid, and the excess allowed to trickle through, rather 
 than be emptied out by inverting the funnel. This previous 
 soaking of the filter greatly facilitates the operation, for dry 
 paper absorbs water directly, and in the case of a turbid solution, 
 while becoming more impervious to the suspended particles than 
 it would be if the liquid which contains them were allowed to 
 penetrate at once into the filter, it gives also a more ready pas- 
 sage to the clear fluid. The edges of the containing vessel are 
 now to be slightly greased in one spot, so that in pouring there 
 may be no adhesion of drops or trickling over the sides. It is 
 then grasped by the right hand and brought over the funnel, 
 while the left hand holds the glass rod at a right angle against 
 the edge of the glass, as shown at Fig. 425. The end of this rod 
 
 Fig. 425. 
 
 should merely reach the filter without touching it, for fear of 
 abrasion ; and the liquid should be allowed to flow down its length 
 in a gentle stream at first against the sides, and as the precipi- 
 tate accumulates it may be allowed to fall in the centre, as there 
 is then less risk of splashing. The filter should never be entirely 
 filled, and as it often requires many pourings to pass the whole 
 of the liquid, great care must be taken in returning the rod t 
 vessel that nothing be lost. The last particles maybe rinsed 
 from the vessel and rod by the jet of the spritz bottle A 
 
506 
 
 THE SPRITZ. 
 
 426), by inclining both to the positions shown in the drawing 
 below. If any remaining particles still obstinately adhere to the 
 
 Fig. 426. . 
 
 sides of the glass, or of the rod, they must be loosened by the 
 feather end of a goosequill, and then washed out as before by 
 the jet of the spritz. When all the liquid has passed through, the 
 precipitate must be washed down from the sides of the filter by 
 the force of the jet of water from the spritz. 
 
 The spritz, or washing-bottle, consists of a twelve ounce vial, 
 
 Fig 427. 
 
 to the mouth of which is adapted, by means of a perforated cork, 
 a glass tube, drawn out at its upper end as shown in Fig. 427, 
 Fig. 428. which represents at the same 
 
 time its exact dimensions. The 
 bottle is rather more than half 
 filled with water, and by blow- 
 ing into it through the tube the 
 air is compressed, and when the 
 bottle is quickly inverted it 
 forces out the water through 
 the orifice in a strong jet, which 
 may be directed to any desired 
 point. The bottle, complete, is 
 exhibited at Fig. 428. For 
 washing out beaker glasses, or other deep vessels, a curved jet 
 

 WASHING BOTTLES. 597 
 
 is more convenient, and is seen at A, Fig. 426. An india-rubber 
 ball may replace the bottle, it being only necessary to fit the 
 tube in the neck, and tighten the joint with a twine wrapping. 
 This instrument is managed as directed for the pipette, p. 200. 
 
 When hot water is required, the bottle should be 
 of copper, tinned on the inside, of at least a pint 
 capacity, and of the form presented by Fig. 429. 
 It is heated as directed at p. 231, Fig. 185, and 
 to prevent burning of the hand, is fitted with a 
 non-conducting handle. Upon inversion of the 
 bottle, the water is driven through the tube d in 
 a strong jet by the elastic force of the confined 
 vapor. 
 
 In dusty apartments, both funnel and receiving-vessels should 
 be kept covered by circular or square pieces of window-glass. 
 The one over the receiver should have an opening in the side for 
 the passage of the barrel or tube of the funnel. 
 
 The receivers are most generally beaker glasses, but capsules, 
 flasks, and narrow-necked bottles are all made 
 use of. The above precautions refer espe- Fig.430. 
 
 cially to filiations in analytic operations. CH^H^-^ 
 In larger operations the manipulation is not, \ / 
 necessarily, so strict, and when the dimen- 
 sions of the containing vessel will not admit of convenient hand- 
 ling, its contents may be conveyed to the filter by ladlesful in the 
 small porcelain dipper, Fig. 430. The ladle, during the inter- 
 vals of the transfers, must rest in a plate, and not be placed any- 
 where in the dust. 
 
 In order to expedite the process, the liquid, as a general rule, 
 should be allowed sufficient repose previous to filtration, to de- 
 posit if possible all its suspended matter, and the clear superna- 
 tant portion should be passed through first. The subsident 
 matter being added last, is filtered, as it were, alone, and offers 
 no impediment by obstructing the pores of the filter to the 
 passage of the liquid portion, as it would if mixed with it. As 
 an exception to this rule, certain precipitates which are curdy, 
 gelatinous, flocculent, or crystalline, may be filtered immediately 
 after their formation. As warmth usually expedites the process, 
 nearly all liquids, when circumstances permit, should be filtered 
 whilst hot. 
 

 508 
 
 FILTRATION PROMOTED BY WARMTH. 
 
 Below is a drawing of an apparatus, Fig. 431, convenient for 
 keeping liquids warm during the operation, and known as Hare's 
 filter-bath. It consists of an oval copper jacket, flat at top and 
 bottom, with two conical apertures through its body. The cone, 
 with its expanded part directed downwards, is a sort of chimney, 
 under which a spirit-lamp is placed to heat the water in the bath, 
 and the other is a bed for the funnel. To prevent ignition of the 
 vapors when inflammable liquids are under process, there is a 
 partition beneath. 
 
 Fig. 431. 
 
 Fig. 432. 
 
 This apparatus is particularly applicable for the filtration of 
 oils and viscous liquids. For small operations, such as ana- 
 lytical experiments, it may be conveniently replaced by a very 
 simple arrangement, suggested by Normandy. It consists of a 
 common glass flask two-thirds full of water, and connected by a 
 leaden pipe with a circular dish, having a rim in the interior for 
 the support of a bell glass with an open mouth. The beaker 
 which receives the filtrate is placed upon a stand in the centre 
 of the dish, and above it is the paper filter supported in a pla- 
 tinum ring, as seen in the drawing, Fig. 432. 
 
 Heat being applied to the flask, steam is soon generated, and, 
 passing into the bell, eventually escapes through the mouth. 
 The filter being thus constantly surrounded by an atmosphere of 
 hot vapor, not only delivers its filtrate clear and rapidly, but 
 also free from the action of atmospheric air. 
 
FILTRATION THROUGH CLOTHS. 509 
 
 For filiations of heavy precipitates, or a large amount of 
 liquid, it is advisable to ue the filter doubled, or even trebled, as 
 it will be thus enabled to resist a very heavy weight. This pre- 
 caution is necessary also when the liquid runs through a single 
 paper turbid. When only the first runnings are turbid, a single 
 filter will answer for small experiments, but the liquid must be 
 repassed through the same medium. 
 
 FILTRATION THROUGH CLOTHS. In large operations, or when 
 the solid matter to be separated is too heavy, or would corrode 
 or clog the pores of paper, the latter is replaced by cloth. The 
 kinds of cloth vary, and each of those already mentioned has its 
 appropriate application. The texture of the medium must be 
 adapted to the consistence of the liquid ; for example, flannel or 
 felt may be used for filtering mucilaginous, saccharine, and 
 slightly acidulous solutions ; twilled cotton or canton flannel for 
 oils ; linen and muslin for tinctures, vegetable juices, and dilute 
 alkaline lyes. Sieves of bolting cloth are occasionally used for 
 filtering liquids from very fine or flocculent matters. 
 
 Filters made of the materials above-mentioned, and which take 
 the name of strainers, instead of 
 being used like those of paper, are Flg 433< 
 
 suspended upon square frames 
 formed of four pieces of lath, as 
 shown at Fig. 433. These frames, 
 of which there should be several 
 sizes, must be strongly jointed, and 
 should have inserted upon their 
 upper surfaces a number of rectan- 
 tangular hooks, similar to those 
 
 used in the drying-lofts of calico factories for hanging up the 
 printed goods. The cloth, of whatever kind, being cut into a 
 square of size proportioned to that of the frame, is stretched over 
 it very loosely, and retained in position by hitching its margin on 
 these tacks or hooks. This mode is far preferable to that of 
 nailing the cloth down with flat-headed tacks, for besides the 
 injury of material, there is less convenience in removing it if* 
 the filtration for pressure, or for replacing it with another when 
 it is required. The support for these strainers is an upright 
 
510 
 
 FILTRATION THROUGH CLOTHS. 
 
 stand, Fig. 434, the interval between the legs of which is suffi- 
 cient to allow the free entrance of the receiving-vessel. 
 
 Fig. 434. Fig. 435. 
 
 Fig. 430. 
 
 " When the cloths are made into conical bags, as is very often 
 the case, and not without advantage, they are to be suspended 
 by loops to a transverse beam, as shown in Fig. 435. The loops 
 or hangers are fastened to the ring, Fig. 
 436, around which the rim of the bag is 
 hooked. These bags allow the conve- 
 nience of using narrow-mouthed receivers, 
 as the liquid trickles through in a stream 
 from the most depending parts. 
 
 The texture of the straining-cloth must 
 be porous, but sufficiently compact to 
 prevent the passage of any solid par- 
 ticles. It is far more convenient than paper for coarse filtration 
 of decoctions, tinctures, oils, syrups, and for separating liquids 
 from solid organic matters. In most instances, the cloth or bag 
 may be renovated by washing, and thus be rendered fit for other 
 operations. 
 
 Before stretching the cloth upon the frame, or suspending the 
 bags, they should be first moistened with water, or, if necessary, 
 with a portion of the solvent liquor, in order to swell the fibres 
 and contract the meshes. The liquid should be then introduced 
 gradually without spilling. For this purpose, a tinned, copper, 
 or porcelain ladle, Fig. 437, with a wooden handle, is very con- 
 
FILTRATION THROUGH PULVERULENT MATTERS. 511 
 
 venient. A very excellent substitute is a dipper, made from, a 
 cocoa-nut shell, and sold in any of the furnishing shops. Addi- 
 
 Fig. 437. 
 
 tions of liquid should be made until the filter is nearly full, and 
 it should be kept at the same level by renewing it as fast as it 
 runs through. If the first runnings are turbid, they should be 
 returned to the filter, and if they continue murky, repassed 
 through a fresh cloth. 
 
 After all the liquid has passed through in this way, the cloth 
 or bag is to be unhooked, carried to a table, securely folded, and 
 enveloped in a wrapper, and subjected to pressure as directed at 
 p. 459, for the expulsion of the retained portion of liquid. The 
 precipitate thus pressed, when an object of value, is to be cut up 
 with a spatula and spread on frames for DESICCATION. 
 
 The cloths are then to be immediately rinsed and cleaned in 
 water without soap, dried, and placed away for service at another 
 time. 
 
 FILTRATION THROUGH PULVERULENT MATTER. Crushed 
 quartz, clean white sand, asbestos, bone-black, and charcoal, are 
 the materials generally used as media. The two latter act both 
 as filtering and purifying agents, as the liquid becomes not only 
 clarified in its passage, but freed from coloring and putrescent 
 matters, if any exist in it. The others are used for the filtration 
 of very acid or corrosive liquids, which would be destructive of 
 paper or cloth, and partially solvent of bone-black. 
 
 All of these substances may be used in funnels, a thin stratum 
 being placed in the bottom of the body, and prevented from 
 escaping through the barrel by a loose cotton plug in the neck. 
 
 A funnel plugged in this manner, even without the stratum of 
 pulverulent medium, answers an excellent purpose for the filtra- 
 tion of liquids which pass through freely, and whose suspended 
 matter is in coarse particles. 
 
 It will of course be remembered that the use of these media is 
 only practicable when the liquid is the sole object of value, for it 
 would be impossible to prevent at least the partial admixture of 
 the suspended matter with the secerning agent. 
 
 The asbestos, sand, and charcoal, should first be treated with 
 
512 
 
 FILTRATION OF VOLATILE LIQUIDS. 
 
 Fig. 438. 
 
 muriatic acid to remove soluble matters, and then thoroughly 
 rinsed with fresh "water to remove all traces of acid previous to 
 their employment as filtering means. Freshly prepared and 
 finely powdered charcoal, by its absorbent power, deprives most 
 liquors of their fetor and organic coloring matter ; bone-black has 
 the same effect, but in a much less degree. These two are the 
 best substances for separating impurities from syrups and aqueous 
 liquids. 
 
 The filtering substance should always, before being used, be 
 moistened throughout, as in displacement, with clean fluid, or, as 
 is proper in many cases, with the pure liquid which is the solvent 
 of the various substances in the fluid which is to be depurated. 
 Thus the substance in the funnel may be made to imbibe water 
 before the filtration through it of a syrup, and alcohol or ether 
 before the passage of tinctures or ethereal solutions. 
 
 Filtration by DISPLACEMENT, to which the above mode is in 
 some respects similar, has already been fully described at p. 452. 
 FILTRATION OF VOLATILE LIQUIDS. Donovan has contrived 
 an apparatus for filtering liquids which 
 are vaporizable or alterable by exposure 
 to air. It is identical in principle and 
 construction with the displacer, Fig. 372, 
 and is very useful for filtering alcoholic, 
 ethereal, or ammoniacal, and alterable 
 caustic liquids. 
 
 The modification of Riouffe is more 
 convenient than the original apparatus, 
 as it allows the use of an ordinary funnel 
 with a cover. It is represented by Fig. 
 438, and consists of a glass bottle A, with 
 two necks, into one of which enters the 
 barrel of the funnel. The neck of this 
 funnel is loosely closed with a plug of 
 raw cotton, and the liquid is introduced 
 through the s tube without uncovering or 
 disturbing the apparatus, As the liquid 
 filters through, the column of air displaced finds a vent through 
 the narrow tube a, adjusted in position by means of perforated 
 corks. The stop-cock K allows the withdrawal of the filtrate at 
 pleasure. 
 
WASHING. 513 
 
 CHAPTER XXVII. 
 
 WASHING. 
 
 v 
 
 IN all precipitations, the powder thrown down becomes involved 
 with more or less of the original liquid from which it has been 
 deposited. As these liquid portions are impurities, they must be 
 separated ; and in many large operations, and when the precipi- 
 tate is bulky, we effect their removal by repeated washing and 
 DECANTATION ; but when the powder is light, and in all cases 
 where accuracy in estimating results is required, the purification 
 is conducted by pouring continued streams of water or other fluid 
 through the substance contained on the filter. 
 
 Washing by decantation is usually practised by diffusing the 
 precipitate in a large quantity of cold or hot water, or other suit- 
 able liquid, as circumstances may require or 
 admit ; stirring well, and after sufficient re- 
 pose for settling, decanting the clear super- 
 natant solution. A repetition of additions of 
 fresh water, and subsequent decantations after 
 repose, will entirely remove all soluble matter 
 and free the precipitate from impurity. 
 
 In analyses, the precipitate is most gene- 
 rally washed upon the filter by projecting 
 water from the spritz bottle A, Fig. 426, the 
 jet of which, by its force, at the same time 
 loosens that portion adhering to the sides, 
 and concentrates it all at the bottom, when a 
 larger amount of washing liquid may be added from the bottle, 
 Fig. 55. To give force to the issuing jet, as is sometimes neces- 
 sary in detaching particles from the filter, the tubes of the spritz 
 may be as shown in Figs. 439, 440. The compression of the air 
 in the interior by blowing in the tube a produces a jet through 
 the lateral one 5, drawn out to a small orifice. This form of 
 spritz is much more convenient for large filters than the smaller 
 one, Fig. 428; either, however, allows the direction of the 
 stream to any desired part of the filter. The above-mentioned 
 
 33 
 
514 
 
 WASHING. 
 
 bottle is flat-bottomed, and of thin glass, so as to answer for the 
 use of boiling liquid. 
 
 Fig. 440. 
 
 The copper flask, Fig. 240, with tubes fitted to its mouth as 
 above described, is, however, far more convenient, and less liable 
 to receive injury. 
 
 Fig. 441. Fig. 442. 
 
 The precipitate being in this manner kept constantly mingled 
 with liquid, is soon freed from its soluble matter. The latter fact 
 is known when a drop of the wash-liquor, which has passed 
 through, leaves no stain upon a silver or platinum spatula heated 
 over the spirit-lamp. 
 
EDULCORATION WASHING BOTTLES. 515 
 
 There are many precipitates which require protracted washing, 
 or edulcoration, as it is sometimes termed, in order to cleanse 
 them thoroughly, and the bottle for the purpose is so con- 
 structed as to be self- operating in a measure, this mode being 
 a great saving of time and labor to the operator. Fig. 441 
 represents the whole arrangement, which is so contrived that 
 by a suitably constructed tube 5, adapted, by means of a per- 
 forated cork, to the flask or bottle a, the water therein contained 
 flows out very gradually, and in quantity proportional to its 
 passage through the filter. The tube is that known as Berzelius's. 
 It may be well replaced by two separate tubes, which can be 
 readily formed over the blowpipe flame by the operator himself ; 
 and the modified implement is shown at Fig. 442. 
 
 Below are the two forms of washing tubes, both acting upon 
 the same principle. Fig. 443 represents the one devised by Ber- 
 zelius, and Fig. 444 that by Gmelin. 
 
 The mode of washing by these bottles is very convenient. 
 They are nearly filled with water, and inverted over the funnel 
 in such a position that the part c extends below the surface of 
 the liquid and no further. The flow continues in a constant cur- 
 rent without further attention until the surface of water in the 
 filter rises towards the line e /, Fig. 444, and diminishes the 
 pressing column, when capillarity is in excess and no more water 
 flows. But as the water slowly percolates through the filter, the 
 column is increased, and the water again flows. This alternate 
 action is continued until the bottle is emptied. 
 
 The great convenience of this arrangement is that a filter may 
 be washed during the absence or inattention of the operator. 
 
 If the precipitate is soluble in water, it' must be washed with 
 alcohol, ether, or other liquid, which is without action upon it. 
 
 When the bottle filled with water is inverted, as in Fig. 441, 
 there will be no efflux of water from the small opening <?, Fig. 
 444, so long as this point is at a certain distance below the curve 
 of the syphon ; but if the moistened finger, or other body, be 
 held to the point c, water will flow freely from it, and air-bubbles 
 will ascend through i b to supply its place. If the tubes and 
 opening were of large size, the water would flow out with touch- 
 ing the end of the tube; but being of small diameter, and the 
 end c being drawn out finely, the efflux of water is opposed by 
 
516 
 
 EDULCORATION WASHING BOTTLES. 
 
 capillary attraction. The column of water between /and$r h 
 is the force tending to overcome the capillary resistance. If this 
 column be lengthened by drawing c d further through the cork, 
 
 Fig. 443. 
 
 Fig. 444. 
 
 then the water will flow out of e spontaneously. If c d be pushed 
 in just so far that the water does not flow spontaneously, then 
 the capillary resistance slightly predominates. Then if a sub- 
 stance to which water adheres by adhesive attraction, be applied 
 to the end of c, it will make the water flow so long as it is held 
 there, because the adhesive attraction of the touching overcomes 
 the capillary action. If c d be thrust still further into the cork, 
 then capillary action predominates so greatly that no adhesive 
 force can counteract it, and the water will consequently not flow 
 out. There is, therefore, a particular medium position for the 
 point <?, where it will act as desired. 
 
 For other than analytic operations, the washing arrangement 
 may be as shown by Fig. 445. 
 
 It consists of a wide-mouth bottle, with two perforations in the 
 cork, through which pass the bent tubes a and b. One of those 
 bent tubes descends nearly to the bottom of the bottle, as at c ; 
 the other stops below the cork. The outer legs of the tubes dip 
 into the filter, the one, 5, deeply, and the other, , just under the 
 surface of the contained liquid. The apparatus being ready, air is 
 to be drawn through the tube b by mouth suction at the end until 
 
COOKE'S WASHING MACHINE. 517 
 
 the liquid rises and flows over into the filter. The current thus 
 established will continue until the level of the liquid in the funnel 
 
 Fig. 445. 
 
 is uniform with the end c of the tube b in the bottle, and then 
 cease. As the latter, however, falls in proportion as the filtra- 
 tion proceeds, it will, of course, from time to time, open the' 
 mouth of the tube a, and the air entering at such intervals sup- 
 plies the pressure necessary to preserve the continuity of the 
 stream of liquid. 
 
 As it is very frequently requisite to wash precipitates with 
 volatile liquids, J. P. Cooke has suggested an arrangement for 
 the purpose, which combines efficiency with simplicity and cheap- 
 ness. It is also applicable for continuous filtration, or for filtra- 
 tion either in vacuo or in an atmosphere of any gas that is de- 
 sirable. Moreover, it protects the filter from the dust and fumes 
 of the laboratory, even when the exclusion of air is not essential. 
 
 The complete arrangement is shown at Fig. 446 (1), and "con- 
 sists of a wide-mouth glass bottle, into the neck of which is firmly 
 ground with emery a funnel , having a short but large spout. 
 These are made sufficiently thick to resist the atmospheric pres- 
 sure, and the rim of the funnel is ground so that the apparatus 
 may be closed air-tight by means of a glass plate. Within the 
 
518 
 
 COOKE'S ARRANGEMENT. 
 
 outer funnel the common filtering funnel is placed, resting loosely 
 against its side, so as to allow free passage of air." This funnel 
 
 Fig. 446. 
 
 and some other parts of the apparatus are shown in enlarged 
 views at 2. 
 
 " In order to wash a precipitate, or to produce a vacuum in 
 the interior of the apparatus, a glass plate, with a hole an inch 
 or more in diameter, drilled through its centre dj is substituted 
 for the covering plate. Through this passes the tube of a wash- 
 ing-bottle/; and this washing-bottle is of the usual construction, 
 except that it is fitted with a cork which projects about an inch 
 above the neck. This upper end of the cork fits the neck of a glass 
 plate, ground on the under side, as is represented at e. The plate 
 is about three inches in diameter, and when resting on the plate d, 
 covers the opening completely, and permits sufficient lateral 
 motion to bring the stream of water on different parts of the pre- 
 cipitate. A vacuum is readily obtained by connecting the appa- 
 ratus with an air-pump by means of a flexible tube having a brass 
 plate at the end sufficiently large to cover the opening in the 
 plate d, and by an easy manipulation, the interior may afterwards 
 be filled with hydrogen or any other gas." 
 
CYLINDER ELECTRICAL MACHINE. 519 
 
 CHAPTER XXVIII. 
 
 THE PRACTICAL RELATIONS OP ELECTRICITY. 
 
 THIS chapter will refer to the most ready and efficient means 
 of developing, detecting, and applying electrical action ; and will 
 comprise information upon the practical points of electricity 
 excited by friction as in the use of the electrical machines ; of 
 electricity evolved by chemical means as in the working of the 
 galvanic battery ; and also of electricity induced by magnetic 
 force, as in the operation of electro-magnetic apparatus. 
 
 We will open the subject with instruction as to the manner of 
 developing electricity by mechanical action, and describe the most 
 approved forms of electrical machines. The works of Faraday, 
 De La Rive, Hare, Noad, and Smead, will afford full information 
 upon theoretical points. 
 
 The Cylinder Electrical Machine is shown in Fig. 447. A is 
 a glass cylinder, the axis of which works in two wooden supports 
 
 Fig. 447. 
 
 fixed vertically in a solid frame. The cylinder is made to revolve 
 by turning a winch connected by a crossed band to a wheel 
 attached to one end of the axis of the cylinder. F, the negative 
 conductor, is a brass tube supported by a glass pillar, and has 
 
520 CYLINDER ELECTRICAL MACHINE. 
 
 upon the side nearest the glass cylinder the rubber, or leather 
 cushion, which presses against the glass. To the cushion is 
 attached the flap of silk G, which extends over the cylinder nearly 
 to the points of the positive conductor c. A screw, passing 
 through two nuts, is so placed bejow as to regulate the pressure 
 of the rubber upon the glass, by increasing or lessening, as may 
 be necessary, the distance between the movable pedestal upon 
 which the former stands and the main supports of the machine. 
 At the opposite side of the cylinder is the positive or prime con- 
 ductor c, being like the other conductor a tube of metal, and also 
 insulated and furnished with balls for the transference of the 
 electricity ; but having, instead of a rubber, a collector E, made 
 hollow, and of sheet brass, and provided with sharp-pointed pro- 
 jections, which almost touch the surface of the cylinder. 
 
 This machine is made to develope electricity by turning the 
 winch, which causes the small wheel and attached cylinder to re- 
 volve with accelerated rapidity. By the friction of the rubber, 
 covered with a metallic amalgam, upon the glass, the electricity 
 acquired by the glass is decomposed, its positive^ element remain- 
 ing attached to the glass, and its negative one to the cushion. 
 The former, prevented from escaping by the non-conducting flap 
 of silk, is carried round with the glass, and, after a series of 
 alterations, by induction, of the equilibrium of that portion of the 
 fluid naturally present in the conductor, finally by passing into 
 it through the highly conducting collector, fills it with positive or 
 vitreous electricity, which can be drawn off from it into other 
 conducting bodies, either insensibly or in sparks. The negative 
 conductor, while insulated, becomes in the same way negatively 
 electrified, and is capable of giving sparks to, or rather receiving 
 them from, other bodies oppositely influenced ; but while uncon- 
 nected with the earth, it gives off but a small amount of its posi- 
 tive component, and soon returns to its former state of equili- 
 brium from its negative electricity being neutralized by the 
 positive kind of the prime conductor, which passes back over the 
 surface of the cylinder, and which also reaches it by other sources 
 of imperfect conduction. 
 
 If much positive excitement is desired, the conductor to which 
 the rubber is attached, must be kept in connection with the earth 
 by a metallic chain or wire. When, on the contrary, the object 
 
PLATE ELECTRICAL MACHINE* 
 
 521 
 
 is to obtain negative electricity from its proper collector, the 
 prime conductor must be made to communicate with the earth by 
 similar means. 
 
 The Plate Electrical Machine. This is a modification of the 
 cylinder machine, and is preferable on account of its simplicity 
 and greater power. In damp weather, too, it is much more reli- 
 able and efficient. The figure shows this machine in its details. 
 
 Fig. 448. 
 
 It consists of a circular glass plate, from one-twelfth to one-eighth 
 of an inch in thickness, and varying in diameter from one to five 
 feet. The plate is traversed at its centre by a metallic axis, 
 fixed solidly to the glass by two clamp-nuts. The axis rests upon 
 two upright wooden supports fixed in a frame, and is so arranged 
 as to hold the glass in a central position. A pair of cushions is 
 fixed to the supports above and below the axis, and so placed as 
 to exert a considerable pressure upon the plate. A rotary mo- 
 tion is given to the plate by a glass handle attached to one end 
 of the axis. Two insulated conductors, joined by a metallic rod, 
 are placed parallel to the axis, and near the circumference of the 
 plate. One end of each conductor encompasses the glass plate, 
 and is fitted with points to draw off the electricity. A chain 
 fastened to the wooden supports serves to connect the machine 
 with the earth. As thus arranged, the plate machine only fur- 
 
522 PLATE ELECTRICAL MACHINE. 
 
 nishes positive electricity; if negative electricity is required, the 
 conductors must be made to communicate with the earth by a 
 chain; and if negative and positive electricity are needed, it 
 becomes necessary to insulate the cushions. 
 
 Great care is requisite in the construction and arrangement 
 of all the parts of the electrical machine. The quality of the 
 glass is the most important point. It should be well annealed, 
 strong, smooth, and even. The best glass is that which contains 
 the largest amount of silica, and has potash for a base. In the 
 cylinder machine all moisture must be carefully expelled from 
 the interior, and its openings hermetically sealed with cement or 
 sealing-wax. 
 
 The cushions are pads made of soft (buckskin) leather stuffed 
 with horse-hair, and should be sufficiently elastic to maintain a 
 strong and uniform pressure. 
 
 The flap attached to the rubber, of ordinary silk, is sometimes 
 waxed. 
 
 It has been found that, in order to render the exciting power 
 of the rubber greater, it is necessary to coat the cushions with 
 an amalgam. The amalgam of tin and mercury, used for making 
 mirrors, mixed with a little lard, answers the purpose very well, 
 or bisulphuret of tin (mosaic gold) may be used ; but the best is 
 formed by adding to six parts of heated mercury a melted alloy 
 of two parts of zinc and one of tin, and triturating the whole in 
 a mortar until cold. This amalgam is made into an unctuous 
 mass with tallow, and the cushions thoroughly covered with it. 
 The cylinder is made to revolve, and the excess of the amalgam 
 is removed with a cloth. The presence of little specks of the 
 amalgam on the cylinder appears to be rather beneficial than 
 otherwise. 
 
 The conductors, in order to preserve the electricity, must be 
 cylindrical and rounded at the ends, and otherwise free from all 
 angular points or projections other than the points which conduct 
 off the current from the glass. They may be made of sheet brass, 
 or of wood smoothly covered with tin foil. The supports must be 
 good insulators, and covered with a varnish of shell-lac ; and they 
 should also be fixed firmly into the frame of the machine and the 
 conductors themselves. 
 
 Electrical machines are most effective in dry and cold weather. 
 
THE LEYDEN JAR. 523 
 
 Any dampness in the atmosphere is unfavorable to the develop- 
 ment of electricity. To put a machine in good order, it should 
 be carefully freed from dust and moisture; this latter is best 
 insured by exposure of the machine before a fire, or wiping the 
 glass portions with a cloth moistened with ether. Care also 
 should be taken to have the communication of certain parts with 
 the earth as perfect as possible ; and to accomplish this, the chain 
 of the opposite conductor, from which it is desired to obtain the 
 electricity, may be connected with the water or gas pipes of a 
 house, or any good conducting substance which penetrates the 
 moist earth. 
 
 When the machine works properly, after a few turns of the 
 cylinder, it gives off a vivid spark with a crackling noise upon the 
 approach of the knuckle or a metallic ball to the insulated con- 
 ductor. 
 
 The Ley den Jar. This apparatus, as shown by Fig. 449, is 
 employed for the accumulation of electricity by 
 induction, and is the agent chiefly made use of for Fi s- 449 - 
 laboratory purposes. It consists of a wide-mouthed 
 thin glass jar, varying in size, neatly coated on its 
 inner and outer surfaces to within about one quar- 
 ter of its height from the top, with tin foil. The 
 stopper is made of cork or dry wood, and is firmly 
 inserted and well varnished. Through its centre 
 passes a metallic rod terminating on the exterior 
 in a smooth round ball, and the interior in a point, 
 or bunch of diverging wires, communicating with 
 the inner coating. The ball at the top of the rod should be at 
 least a half inch in diameter. The stoppers and uncovered por- 
 tion of the glass should be thickly covered with shell-lac varnish. 
 A common vial, containing iron filings, and covered on the out- 
 side with foil up to the level of the metal within, and provided 
 with a rod and ball, as above described, makes a very good Ley- 
 den jar. 
 
 In order to charge the jar the electrical machine must be put 
 in motion, and the jar held in the hand, so that the knob touches 
 that conductor of the machine which contains the kind of elec- 
 tricity it is desired to collect in the jar. The inner coating of a 
 Leyden jar is easily charged with negative electricity by holding 
 
524 THE LEYDEN JAR. 
 
 it by the knob and putting its outer coating in contact with the 
 prime conductor of the machine. When charged, it is necessary 
 to place it upon an insulated table ; for if touched by a con- 
 ducting medium, it would cause an unpleasant shock to the 
 operator. 
 
 The electricity often accumulates in the inner coating until 
 its tension becomes so great that the equilibrium of both coat- 
 ings is restored by a discharge from one surface to the other 
 taking place. For this reason it is not safe to use very large jars, 
 as any imperfection in the glass, which would render a particular 
 part weaker than the rest, would make it liable to fracture by 
 the mutual attraction of the two electricities, which would effect a 
 union by breaking the glass. 
 
 When one kind of electricity is collected in the interior, the 
 opposite sort is produced in the exterior coating, or, in accord- 
 ance with the theory which admits the existence of only one kind, 
 when it is in excess in the inside, it is deficient in the same 
 ratio upon the outside. The tendency is then always to restore 
 that neutrality, or natural order of things in which the influence 
 is not made evident to the senses ; but in a good Leyden jar, the 
 parts should be so arranged as to permit the collection of a large 
 amount of electricity before a spontaneous discharge takes place. 
 If the jar, before becoming highly charged, permits such an 
 escape, it is usually an evidence that there is a hole or crack in 
 the glass, that the uncovered surface has become a partly con- 
 ducting one from the presence upon it of moisture or dust, or 
 finally, that the outer metallic coating extends up so far as to 
 allow of the easy passage of a spark to it from the rod or ball. 
 The last condition can be altered by lessening the height of the 
 outer covering of foil, taking care to reduce that which is within 
 also to the same level. To expel moisture and dust, the vessel 
 should be warmed and wiped, as before directed for other parts 
 of the apparatus. 
 
 The retention for some time, of the charge, by the Leyden jar, 
 is often a matter of great importance in the chemical applica- 
 tions of electricity. A jar, of the capacity above-mentioned, 
 when dry, warm, and fully charged, should, after a lapse of ten 
 minutes, give a spark at least half an inch in length to the ball 
 of a discharging-rod, the ball being one-third of an inch in dia- 
 meter. 
 
THE ELECTRICAL BATTERY. 
 
 525 
 
 The power of the jar is dependent on the amount of the coated 
 surface, and the thinness of the glass. 
 
 The Electrical Battery.-^ is ' an arrangement b ^^ 
 the metallic surfaces of the Leyden jar are greatly increased in 
 size, and by which the intensity of the shock and discharge is 
 multiplied to almost any extent desired. A number of Leyden 
 jars, prepared in the usual manner, are placed in a box, which is 
 lined with tin foil or other metallic coating. The vessels are 
 placed in close contact, or are made to connect with each other 
 externally by the interposition of metallic or coated partitions, 
 and the inner coatings are made to communicate by means of 
 metallic rods or chains, connected with the wires going from 
 their interior. The whole is equivalent to a single large jar, and 
 may be charged and discharged with equal facility. (Fig. 450.) 
 
 Fig. 450. 
 
 The hook, seen in the front of the box which contains the series, 
 is attached to the metallic outer lining. 
 
 When the battery is to be used, it should be ascertained that 
 all the outside coatings are in proper connection with each other, 
 and that the inner surfaces communicate through their appro- 
 priate mountings and wires, and that no wires, threads, water, or 
 other conducting substances extend in any way from the inner 
 to the outer parts of the apparatus. No filamentous or pointed 
 body, or projecting piece of metal, should be allowed to remain 
 very near the battery while it is in operation. The battery is 
 charged by connecting one of the wires or knobs which are in 
 contact with the inner coating of the jars, by means of a chain 
 or wire, with the prime or negative conductor of the electrical 
 machine while it is in operation. It is both filled and discharged 
 
526 THE DISCHARGER. 
 
 in the same way as the Leyden jar, and all its operations are 
 those of that vessel upon a greater scale. 
 
 During the charging of a battery, a diffusion of electricity 
 sometimes takes place over that part of the uncoated glass, which 
 is near the edge of the foil. This is not entirely removed upon 
 the discharge of the coated part, but afterwards gradually returns 
 to the coating and recharges the battery, often to a considerable 
 extent. Hence, if after the discharge of a battery, it be left for 
 a few minutes with the two coatings unconnected, it will, upon 
 the application of the discharger, give a considerable spark. 
 This, which is the residual charge, is discharged in the same way 
 when the Leyden jar is used. 
 
 In order to know when a jar or battery is fully charged, the 
 inner coating is brought in contact with the quadrant electroscope, 
 the arc described by the repulsion of the needle of which shows 
 the relative amount of electricity in the jar or battery. When 
 the angle marked by the needle remains constant, or reaches to 
 45, the jar is filled to its capacity. 
 
 When it is desired to cut off electric communication with other 
 bodies, the object must be placed upon an insulated stool. The 
 latter is nothing more than a common stool with strong legs of 
 glass, which, being non-conductors, effect the insulation. 
 
 A plate of mica, or a piece of dry glass plate, laid across the 
 top of a glass jar, will answer as an insulating plane. It should 
 not be placed upon any conducting body, because of the influence 
 it may receive through induction. 
 
 The Discharger. A discharge between the oppositely electri- 
 fied surfaces of the jar may be effected by bringing one hand in 
 contact with the external coating, and touching the knob with a 
 knuckle of the other. In this case the person receives a shock 
 in his arms, and if the surfaces are large or well filled with elec- 
 tricity, he experiences a painful passage of this shock through 
 the shoulders and chest. A. battery ordinarily charged, should 
 never be discharged in this way, as serious and even fatal results 
 might follow. 
 
 The instrument shown in the figure is called a discharger, and 
 is used to complete the circuit between the opposite coatings of 
 both the jar and the battery. The rods R, R, are so united with 
 a hinge that the balls may be made to come in contact with the 
 
THE ELKCTROPHOKUS. 
 
 527 
 
 surfaces or to be removed from them by means of the insulating 
 glass handles, which are attached to the legs. This arrangement 
 
 Fig. 451. 
 
 Fig. 452. 
 
 gives the power of discharging a jar of almost any size, by re- 
 moving or approximating the handles. A very effectual and 
 cheap discharger is made of a piece of thick wire, about twelve 
 inches long, curved, and terminated by a bullet at each end. 
 
 The Electrophorus. This important instrument, Fig. 452, may, 
 in many cases, be made to take the 
 place of the common electrical machine. 
 A mixture of equal parts of common 
 resin, shell-lac, and Venice turpentine, 
 is melted and kept in a state of fusion 
 at a temperature between 230 and 
 240 of Fahrenheit, until nearly all 
 evolution of vapor has ceased and the 
 
 fluid is quiet. It is allowed to cool to the point of thickening, 
 and is then poured carefully, so as to avoid the formation of air- 
 bubbles, into a circular metallic tray or dish, of about nine or 
 twelve inches in diameter, and half an inch in depth. The resi- 
 nous surface should be as even and as smooth as possible. A 
 wooden box, or a receptacle made by placing upon a smooth 
 board a wooden hoop, are less costly, and do not expose the resin 
 
528 THE ELECTROPHORUS. 
 
 to the risk of cracking from the sudden contraction of the metal, 
 which is apt to occur after its expansion by heat. Upon the 
 smooth surface formed by the cooled mixture, is placed a metallic 
 disk, or one of wood smoothly covered with tin foil, either of 
 which is provided with an insulating handle of glass or sealing- 
 wax, which is inserted in its centre above. This disk should be 
 somewhat less in diameter than the surface of resin. The top 
 has usually attached near its edge a wire terminating in a metal- 
 lic ball, from which the spark is taken. 
 
 When this electrophorus is used, the cover is removed, and the 
 surface of the resin having been dried and slightly warmed, is 
 rubbed or wiped briskly with a piece of dry flannel, a silk hand- 
 kerchief, or the fur of a cat or hare's foot. After excitation by 
 this means, the cover is lifted by its handle also dry and is 
 replaced upon the surface of the resin. A spark will then pass 
 from the knob of the cover to the knuckle, or a metallic body 
 held near it. Upon raising the cover again, another spark, of 
 greater intensity than the first, will be received. A spark like 
 the first will be emitted by the knob after replacing the cover, and 
 again upon its withdrawal one similar in character to the second 
 will be given off, and in this way the experiment may be repeated 
 almost indefinitely, if the weather is favorable. 
 
 The action of the machine is explained in this manner. The 
 negatively excited cake of resin acts inductively upon the elec- 
 tricity inherent in the cover, attracting and combining with its 
 positive element, and repelling its negative one, which accumu- 
 lates in the upper part of the cover. When the top of the cover 
 is touched, the negative electricity escapes, and the positive re- 
 mains in combination with the negative kind of the resin, as long 
 as the latter is covered by the metallic plate. But, upon lifting 
 this by the insulating handle, the positive excitement is in its turn 
 set free, and given off in sparks from the knob. A similar suc- 
 cession of actions goes on for some time, and the instrument has 
 been known to give sparks for weeks without being freshly 
 excited. 
 
 To obtain strong positive sparks, it is necessary to touch the 
 cover, when on the resin, with a finger or other conducting body, 
 and to remove it before raising the cover. To obtain the strongest 
 negative sparks, the cover, when raised, should be discharged of 
 
HENLEY'S QUADRANT ELECTROMETER. 529 
 
 all its electricity, by touching with the hand, before it is again 
 placed upon the surface of the rosin 
 
 DETECTION OR MEASUREMENT OP ELECTRICITY. -It is an 
 established fact that ordinary annealed glass and sealing-wax 
 become respectively positively and negatively excited when rubbed 
 with a piece of silk. It is equally well determined that an at- 
 traction exists between bodies in their natural state and electrized 
 matter; that bodies, in a similar state of excitement, repel each 
 other; and that, on the other hand, bodies oppositely electrized 
 attract each other. Thus it is that we are enabled to apply tests 
 which will distinguish the kind of electrical excitement shown bv 
 various substances. 
 
 Instruments for this purpose are called electroscopes, the 
 simplest form of which consists of a glass rod to which is fixed a 
 thread of silk suspending a pith ball. If a piece 
 of sealing-wax, excited by rubbing, is brought 
 near this ball, the ball will be attracted to the 
 sealing-wax, and after having touched it will be 
 repelled. The ball, in the first instance, being 
 attracted by the negative electricity of the wax, 
 after having come in contact with it, becomes 
 itself negatively electrized and is repelled. Any 
 electrized substance brought near the ball will 
 then attract it, if positively electrized, and repel it if in a negative 
 state. 
 
 Henley's Quadrant Electrometer. This instrument, Fig. 454, 
 chiefly used to determine the amount of electricity present in the 
 conductor and in the Leyden jar, consists of a semicircle 
 of ivory or of wood covered with white paper, which is 
 graduated into 180 degrees, and fixed at its base to a 
 wooden column. In the centre of the semicircle there 
 is a pin upon the column, from which a movable radius, 
 terminated by a pith ball, is suspended. The column 
 may be fixed in a hole in the conductor. Upon working 
 the machine, the column and the ball being alike affected, the 
 latter with its radius is repelled from the former, and by the 
 amount of the divergence the force is exhibited in degrees. By 
 means of this instrument, we are enabled to ascertain when a jar, 
 or battery, in contact with the conductor, is sufficiently electri- 
 
 f\ A 
 
530 BENNET'S ELECTROMETER. 
 
 fied. During the accumulation in the inner coating, the elec- 
 tricity is retained forcibly by the attraction of the contiguous and 
 oppositely electrified surface, and will not be given off to an insu- 
 lated body, or one which is not in connection with the outer 
 coating. But, in proportion as it ceases to be retained by this 
 inductive action, and accumulates in the conductor, it raises the 
 index of the electrometer, often to a considerable height. When 
 a battery has received its greatest amount of charge, the ball 
 seldom rises above 40 or 50, as the tension of the electricity 
 never equals that of a single jar, probably on account of the 
 larger surface exposed to induction. 
 
 Bennet's Electrometer. This instrument, more properly called 
 an electroscope, as it detects rather than measures electricity, is 
 
 exceedingly delicate in its indications. 
 Fig. 455. j t cons i s ts in part of a glass cylinder, 
 
 which may be similar in form to the one 
 shown in the drawing. A circular brass 
 cap c, covers tightly the vessel, and to 
 its centre is attached a metallic rod, 
 enclosed in a glass tube, which is well 
 varnished with shell-lac, and having 
 attached to its ends two slender strips 
 of gold leaf hanging parallel to each 
 other. Two strips of tin foil T T, are 
 pasted upon the inside of the glass, with 
 their upper ends a little above the level 
 $<i-A of the depending extremities of gold 
 leaf, and their lower ends connected with the metallic bottom of 
 the glass cylinder. When an electrified body is made to ap- 
 proach the cap of the electrometer, the gold leaves will diverge, 
 and if the excitement be sufficiently powerful, will touch the tin 
 foil, and then return to their former state of rest. 
 
 The delicacy of Bennet's electrometer is much increased by 
 the addition of two metallic disks, one having its centre soldered 
 to the side of the cap of the instrument, being in a perpendicular 
 position, and the other being attached to a rod which is connected 
 with the metallic foot of the instrument by a hinge, so that it 
 may be placed parallel to the other disk, and so near as almost 
 to touch it without actually doing so. The presence of elec- 
 
BENNET'S ELECTROMETER. 531 
 
 tricity in the metallic cap and its disk, induces the opposite kind 
 in the contiguous metal, which is then to be removed a few inches 
 from its former position. As this disk is connected with the 
 base of the instrument, and of course with the tin foil upon the 
 inside of the glass, that becomes also oppositely electrified from 
 the cap, the connected gold leaves of which diverge to a much 
 greater degree than in the simple instrument. This is called the 
 condensing electrometer. 
 
 Bennet's electrometer is the one in most common use, and 
 many circumstances of interest in reference to its employment 
 are worthy of note, particularly those connected with the means 
 of ascertaining the kind of electricity which causes- its gold leaves 
 to diverge. 
 
 If an insulated conducting body containing electricity, such as 
 the prime conductor of the electrical machine, is made to approach 
 or to touch the cap of the electrometer, the leaves diverge to a 
 greater or less degree, in proportion to the tension of the elec- 
 tricity in the body, and remain separated, gradually returning to 
 their former position as the influence passes off. In examining 
 the condition of a body supposed to be highly electrified, care 
 must be taken not to make it approach the cap too rapidly, as 
 the result of a sudden and powerful communication of the agent 
 is very often the immediate separation and tearing of the gold 
 leaves. When a non-conducting body, electrically excited, a 
 piece of sealing-wax, for instance, is brought near to or in con- 
 tact with the top of the instrument, the same divergence takes 
 place ; but it is temporary, as upon the withdrawal of the body 
 the leaves come together again. To make their separation as 
 lasting as in the former case, it is necessary either to allow the 
 body to remain for a time upon the cap, or to rub it over its sur- 
 face, so that it may communicate its electricity from a number of 
 points. So far, the electricity of either kind, imparted to the 
 cap, has been that of conduction. But if the electrified body be 
 held so near to the cap, as just to cause the divergence of the 
 leaves, that divergence will diminish gradually until the leaves 
 finally collapse. If now the body be removed to such a distance 
 that it can scarcely affect the leaves, they, after coming together, 
 will often gradually diverge as before. This second separation 
 is caused by induction, and when it occurs, the opposite kind of 
 

 532 THE VOLTAIC PILE ELECTROSCOPE. 
 
 electricity to that existing in the body will be found to be pre- 
 sent in the cap and leaves. The same effect is produced by 
 touching the cap with the hand, while the leaves are diverging 
 from the electricity of the excited body, by removing the hand 
 after the collapse occasioned by its first contact, and by then 
 withdrawing the electrified body, as before, to a greater distance 
 from the cap. 
 
 It is well known that a piece of sealing-wax rubbed with warm 
 flannel becomes negatively electrified, and that a glass tube 
 rubbed with a silk handkerchief becomes positively affected. 
 These facts present us with the means of determining the kind of 
 electricity which is transferred to the cap and leaves of Bennet's 
 electroscope. If, after the leaves have been made to diverge by 
 the approximation to the cap of an excited body, the presence 
 upon the top of a piece of rubbed sealing-wax makes the diver- 
 gence greater, the electricity in the body is negative. If, how- 
 ever, the leaves approach each other slowly, or collapse at once, 
 the electricity is more or less positive. In the same way, a warm 
 tube of glass, rubbed with a silk handkerchief, will increase the 
 separation of the positively electrified leaves, and diminish or 
 annul it when they are negatively excited. 
 
 The Voltaic Pile Electroscope. This was invented by Bohnen- 
 berg. It consists of two dry voltaic 
 Flg> 456 - piles, made of layers of paper, tinned on 
 
 one side, and covered with a thin coat of 
 peroxide of manganese on the other. The 
 manganese is made to adhere by forming 
 it into a paste with milk and starch. The 
 paper thus prepared is cut into disks and 
 made into piles, care being taken to ob- 
 serve the proper order, the tin and man- 
 ganese being always in contact. The 
 piles are fixed on a stand about four 
 inches apart, and each is terminated by 
 a metal ball of the same diameter as the 
 disks. The order of the disks is so ar- 
 ranged that the upper poles of the two piles are respectively posi- 
 tive and negative ; the manganese being the positive element. 
 The whole is covered by a bell glass, through the top of which is 
 

 COULOMB'S ELECTROMETER. 
 
 533 
 
 Fig. 457. 
 
 inserted a metal wire having attached to its lower end a piece of 
 gold leaf, which hangs exactly between the poles of the two piles. 
 This forms a very sensitive electroscope, and indicates the kind 
 as well as presence of the electrical excitement 
 
 Coulomb's Electrometer. -K\\ the instruments previously de- 
 scribed indicate the presence of electricity, but afford little idea 
 of its quantity. Coulomb's torsion balance gives us a means of 
 measuring it with approximate exactness ; or rather of comparing 
 the amount of it found in one body with that existing in others 
 or in the same body at different times. This instrument, as repre- 
 sented in Fig. 457, consists of a slender beam, or thread, of shell- 
 lac B, having a gilt pith ball attached to one end, and a little 
 vane of paper to the other, and suspended at 
 its centre by a fine metallic wire, or, what is 
 better, a delicate filament of spun glass. This 
 ascends in a cylindrical or square frame of 
 glass, and its upper end terminates in a key 
 D, furnished with an index, the whole being 
 capable of moving easily in the centre of the 
 circle 6r, which is graduated into 360. A 
 rod of shell-lac I 7 , is inserted in the hole H, 
 and is prevented from falling down into the 
 glass cylinder which surrounds the whole ar- 
 rangement, by a stop at E. This rod termi- 
 nates in a gilded ball, which is called the 
 carrier ball, as it is used to convey to the 
 electrometer proper, the electricity of the 
 excited body. When this instrument is to be used, the rod F is 
 brought into contact with the excited body ; its ball acquires some 
 of the electricity, and upon being placed in the cage, it gives a 
 part of it to the ball of the lac beam. This having now the same 
 kind of electricity, is repelled from the ball of the rod, and de- 
 scribes a certain angle to its former position, which it retains 
 until it loses its electricity. To measure the amount of fluid thus 
 acquired, the key D, to which the glass thread is fastened, must 
 be turned around, until by the torsion or twisting of the latter, 
 the ball of B is made to come in contact with that of F. The 
 number of degrees described by the index, which is attached to 
 the revolving key D, gives an approximation to the proportion 
 
534 LANE'S DISCHARGING ELECTROMETER. 
 
 of electricity derived from the contact of the ball of F with the 
 electrified body. 
 
 A more simple form of this electrometer, and the one ordi- 
 narily described, consists of a lac needle with a gilt ball at each 
 end, suspended by means of a fine untwisted thread of raw silk, 
 which is fixed at top to a micrometer, by means of which it can 
 be turned around any number of degrees required. The whole 
 is encased in a glass vase or cylinder, with a tightly-fitting top 
 of glass, through a hole in the centre of which the silk passes, 
 the micrometer being above. Upon the level of the suspended 
 needle, a hole, drilled through the sides of the glass, encloses a 
 wire having a metallic ball at either end, the inner one being 
 nearly in contact with one of the pith balls. The excited body 
 is made to approach the outer ball, and, as in the instrument 
 before described, the movable knob separates from the other, and 
 the quantity of electricity is proportional to the distance to which 
 it is driven off. 
 
 Lanes Discharging Electrometer. This instrument is for 
 indicating the intensity of a charged jar or battery. Its con- 
 struction is shown in Fig. 458. A glass 
 arm, fitted in the cover of the Leyden 
 jar, has a hole in its upper end, on & line 
 with the ball of the jar, through which 
 passes a metallic rod, terminated at each 
 end with a ball similar to the one of the 
 jar. The outer ball communicates by a 
 chain with the external coating of the jar, 
 and the inner is advanced to the ball of 
 the jar until near enough to receive the 
 spark. The intensity of the charge is 
 shown by the distance at which the dis- 
 charge takes place. Of course, in the comparison of batteries, 
 the result is only relative when made under a like condition of 
 the atmosphere. 
 
 Calorific Electrometer. " The effect of the electrical discharge 
 on metallic bodies is to raise their temperature to a greater or 
 less degree, and, in many instances, to render metallic wires red- 
 hot, and to dissipate them in a shower of melted globules. The 
 fusion of wire has accordingly been resorted to as a measure of 
 
THE GALVANOMETER. 
 
 535 
 
 Fig. 459. 
 
 the force and extent of electrical accumulations on coated glass. 
 Independent of the uncertainty and tediousness of this method, 
 it is quite inapplicable for nice investigations. The calorific 
 electrometer, whilst it avoids all destruc- 
 tion of the metal, indicates at the same 
 time the comparative heating effect of the 
 discharge, and admits of an accurate 
 estimation of the force in operation. It 
 consists of an air-thermometer, Fig. 459, 
 having a fine wire of platinum passed 
 air-tight across its bulb, which is screwed 
 also air-tight on a small open vessel con- 
 taining a colored liquid, and soldered to the 
 extremity of a bent glass tube. The long 
 vertical leg of this tube is supported by 
 a graduated scale of inches and tenths, 
 on a convenient foot, the lower part of 
 which is marked zero, at the point where 
 the colored liquid in the short leg finds its level. There is a 
 small screw- valve on the top of the ball, to admit of an opening 
 with the external air, so as to adjust the fluid to zero. 
 
 " When an electrical accumulation from a jar or battery is 
 passed through the wire in the ball, the temperature of the wire 
 is more or less raised, which causes the air to expand and press 
 the colored fluid up in the long leg, the altitude being measured 
 on the graduated scale. In this way, a comparative numerical 
 value of the heating effect of the discharge may be arrived at; 
 and it is found that the height to which the fluid rises in the long 
 leg is, cceteris paribus, as the square of the quantity of electricity 
 discharged through the wire. The delicacy of this electrometer 
 will depend on the size of the platinum wire, which, for ordinary 
 purposes, may be from one-fiftieth to the joo^h of an inch in dia- 
 meter, and about three inches in length, corresponding with the 
 diameter of the ball of the thermometer." 
 
 The Galvanometer. This is an instrument for detecting the 
 electricity developed by chemical or galvanic action. If a com- 
 mon magnetic needle, supported upon its pivot, be placed directly 
 under and parallel to a wire which is connected with the poles of 
 a galvanic circuit, so that the positive fluid will pass through the 
 
536 THE GALVANOMETER. 
 
 wire from the north to the south, it will, during the passage of 
 the current, leave its position in the magnetic meridian, and, 
 after a few oscillations, assume one nearly or quite at right 
 angles to it, its northern end or austral pole pointing to the east, 
 or to some point between it and the north. Precisely the same 
 effect will be produced if the needle is placed over the wire, and 
 if the direction of the current is reversed. But the northern end 
 will be turned towards the west, if the current is passed from the 
 north to the south while the wire is under it, and also in the 
 same direction if the wire, again placed over it, transmits the 
 fluid from the south to the north. The needle always returns to 
 its former position immediately after disconnecting the wire. 
 The power possessed by a galvanic current of influencing the 
 magnet, may be increased to almost any extent, by passing it 
 through a number of wires, or a coil made of a single one, so as 
 to make the action of the whole equivalent to the sum of the ac- 
 tions of all its spires. This can be done most effectually by bend- 
 ing a long wire, covered with cotton or silk, to prevent the lateral 
 escape of the current, into the form of a rectangle. The needle 
 is supported parallel to, and between its horizontal branches, and 
 it is obvious that it will be similarly affected by each part of the 
 coil, in whatever position its wires may be; for, as before stated, 
 a current passing above it from the north to the south, and one 
 passing below from the south. to the north, cause it to deflect in 
 the same direction. This instrument is the galvanometer, or the 
 "electro-magnetic multiplier," of Schweigger. By its use we can 
 detect traces of electricity much too mi- 
 ; ,,, Fig. 460. nu j. e to ac j. on t k e gold-leaf electrometer; 
 
 tmt its chief applications are to the dis- 
 covery of delicate galvanic currents, and 
 to the determination of their direction. 
 As shown in the figure, 460, it consists of 
 the coil of covered copper wire N B s, containing usually about 
 twenty convolutions, of which the extremities are connected with 
 the cups c z. A card, graduated into 360, is fixed to the board 
 A, so that a line drawn between the numbers 360 and 180, coin- 
 cides with the direction of the centre of the coil. Above this is 
 placed a delicate magnetic needle, supported on a pivot. The 
 coil is placed with its long axis in the magnetic meridian. If 
 
ASTATIC GALVANOMETER. 
 
 537 
 
 any source of feeble electricity is now connected with the cups, 
 the current from it will pass through the coil, and the magnet 
 will move to the east or west, according to the direction of the 
 fluid. The intensity of the influence is estimated in degrees, by 
 comparing the position of the utmost divergence of the needle 
 with the number under it on the card. The delicacy of this in- 
 strument depends in a great measure upon the number of convo- 
 lutions of wire. Thus, if all other circumstances are favorable, 
 it may be supposed that one consisting of one hundred turns will 
 detect an amount of electricity which is only one-fifth as great as 
 that shown by the one with twenty convolutions. 
 
 The Astatic G-ahanometer. The sensibility of the common 
 galvanoscope may be almost indefinitely increased by connecting 
 the magnetic needle immovably with another one placed above 
 the rectangular coil of wire, but parallel, and opposed in the 
 direction of its poles to tjie first. They are fastened by their 
 centres to a common axis, which revolves freely in an aperture 
 of the upper branch of the coil. This axis is suspended by a fibre 
 of silk to the upper part of the glass or other vessel in which the 
 whole is encased, and it penetrates a graduated card, placed 
 under the upper needle. This arrangement makes the needle a 
 
 Fig. 461. 
 
 balance of torsion, the movements^ which are compared with the 
 degrees marked upon the card, in the same way as in the simple 
 multiplier. Terrestrial magnetism has scarcely any effect upon 
 this system of needles, and would have none at all if both po| 
 sessed an equal amount of magnetic power, the tendency o 
 
538 ASTATIC GALVANOMETER. 
 
 one to assume its position in the meridian being in that case en- 
 tirely counteracted by the reversed direction of the other. By a 
 reference to the statements at the head of this article, it will be 
 seen that a current passed through the coil, in either direction, 
 will have the same effect upon both needles. Fig. 461 represents 
 two of the many forms of Nobili's galvanometer. It is called 
 astatic because it is unaffected, or nearly so, by the magnetism 
 of the earth. 
 
 As these instruments are used not only to detect currents, but 
 also to ascertain the directions in which they pass through the 
 wires, it is important to impress upon the mind the movements 
 of the needles which indicate that one or other extremities of the 
 coil is in connection with the positive or negative electric poles. 
 A simple aid to the memory is to suppose that a current is pass- 
 ing around the middle of a watch, from the handle over the face, 
 and is returning back to its place of origin. The minute-hand, 
 if pointing to the hour twelve, which is usually placed next to 
 the handle, may be supposed to represent the northern half of 
 the needle. It would then move around in its usual direction 
 towards the figure three. If the current were passed around the 
 back of the watch from the handle, and returned to the face, the 
 hand would move backwards towards the figure nine. Ampere 
 has devised the following formula, which is still better calcu- 
 lated to impress the direction of the deviations upon the memory. 
 " Let any one identify himself with the current, or let him sup- 
 pose himself to be lying in the direction of the positive current, 
 his head representing the copper, and his feet the zinc plate, and 
 looking at the needle, its north pole will always move towards 
 the right hand." The person must, however, suppose himself to 
 be lying over the needle, his head and its north pole being both 
 in the same direction. 
 
 The needles, notwithstanding all care to make them astatic, 
 will vary in their magnetic force. Nobili suggests, in order to 
 equalize the action of the needles, that after having discovered 
 which of the poles of the needles are most highly magnetized, to 
 abstract a portion of the magnetism by touching them lightly 
 with the opposite pole of a weak magnet. As the sensibility of 
 the apparatus depends upon the needles having only so much 
 directive force as to keep them in a fixed position, it is necessary 
 
DIFFERENTIAL GALVANOMETER. 539 
 
 to adjust them carefully, so that they may he affected hy the 
 feeblest current. 
 
 After the direction of the current is once ascertained in the 
 instrument, to avoid delay and the annoyance of repeating the 
 operation, it is best to mark it upon the card. 
 
 Differential Galvanometer. An instrument for comparing the 
 force of two currents. It is made by forming simultaneously into 
 a coil two wires exactly similar in diameter, length, and every 
 respect ; and arranging the needles so that when two equal and 
 opposite currents are passed through the wires they will exactly 
 neutralize each other, and bring the index to 0. But when un- 
 equal currents are compared, the needles will indicate the direc- 
 tion of the currents and their relative intensity. 
 
 Galvanometers of this sort differ only in the length and size of 
 the insulated wires, according to the purposes to which they are 
 to be applied. Care is requisite in winding the coils to have the 
 wires perfectly insulated. This is attained by gimping them with 
 thick silk, and interposing a coat of shell-lac between each suc- 
 cessive layer on the coil. In the case of galvanometers, it is im- 
 portant not to subject them to currents too powerful for their 
 capacity, as the action of the needles is apt to be impaired by a 
 diminution, and sometimes even of an inversion of their mag- 
 netism. 
 
 Weygandt's Galvanometer. The principal novelty of this 
 apparatus, Fig. 462, is the construction of the pole-changer, 
 which gives great facility in working, and allows the coil and 
 divided circle to be turned freely around without altering the 
 position of the pole-changer or disturbing the needle. 
 
 This instrument, as described in the Franklin Institute Journal, 
 No. 356, rests upon a flat, circular wooden stand (1), about nine 
 inches in diameter, which is supported by three levelling screws 
 (2). On one side of the stand are the two binding-screws (3), 
 for the reception of the wires from the thermo-pile, or metals to 
 be experimented upon ; the wires running from them to the keys 
 of the pole-changer, which is situated diametrically opposite to 
 the binding-screws on the stand (1). 
 
 From the centre of this stand, rises the brass centre, upon 
 which the circular glass box (5), containing the coil and gradu- 
 ated circle, turns with a very steady motion. The two needles 
 
540 
 
 WEYGANDT'S GALVANOMETER. 
 
 Fig. 462. 
 
 are suspended by a human hair from a hook (6) at the top of the 
 instrument, which is arranged so as to be very nicely adjusted 
 for the twist and for its height in the coil. 
 
 The coil, needles, and graduated 
 circle, are enclosed in a glass box, 
 the plate on the top of which has a 
 small hole in the centre through 
 which the suspending hair passes; 
 the hair being protected by a glass 
 tube (7), the top of which is sup- 
 ported by the long brass standards 
 (8), which carry the suspending 
 hook. By this arrangement the gra- 
 duated circle can be read through a 
 plane flat glass, instead of through 
 the side of the glass cylinder, as 
 frequently constructed. The inner 
 wire of the coil comes down to a 
 brass ring, which is fixed to the 
 underside of the bottom of the re- 
 volving-box. Concentric with this 
 ring, and in the same plane, at the 
 
 distance of quarter of an inch, is another brass ring which is 
 connected through the axis with the wire from the outside of 
 the coil. These two rings thus form the extremities of the 
 coil, and the pole-changer plays between them. The wires 
 from the binding-screws are attached to two brass slips, which 
 terminate in pieces pressed by a spring against the inner ring, 
 so that when the pieces are in their normal position, the current 
 from the binding-screws passes through the short space of ring 
 between them, and does not go through the coil ; but when either 
 of the pieces is withdrawn from the inside ring, and pressed 
 against the outside ring, the current passes through the coil, and 
 by altering their position again, bringing that one which was 
 against the inside ring in contact with the outside ring, and that 
 which was in contact with the outside against the inside ring, the 
 direction of the current is changed, and the needle deflected in 
 the opposite direction. If the stand is placed upon the table 
 
WEYGANDT'S GALVANOMETER. 641 
 
 in a position which is convenient for the operator, with the keys 
 of the pole-changer near his right hand, the coil and graduated 
 circle can be placed in any position without interfering with the 
 circuit, as some part of the brass ring must always be opposite 
 to the pole-changer. 
 
 Each key of the pole-changer works like the writing key of a 
 telegraph ; that is, it is depressed by the finger, and returns to 
 its position by the spring attached to it. By means of the fore- 
 finger and second finger depressing the keys alternately, the 
 direction of the current can be changed six or eight times in a 
 second, and the motion being in a vertical plane, is little liable to 
 affect the adjustment of the instrument. The operator has, 
 therefore, very great facility in bringing the needle to rest by 
 changing the circuit, and thus checking the vibrations, which 
 enables him to make a great many more observations in a short 
 space of time than with any other instrument known. 
 
 This instrument is remarkable for its delicacy, as was confirmed 
 by the following tests. 
 
 Two pieces of zinc and bismuth, each about the size of an ordi- 
 nary type, being held in the fingers of the operator, the free ends 
 touching the binding-screws, produced an instantaneous and steady 
 deflection of 175. 
 
 With a small magnet, weighing about half an ounce, a deflexion 
 of 95 was produced, at the moment of induction, by introducing 
 the magnet into the coil. 
 
 Two wires of zinc and copper, one-twentieth"of an inch in dia- 
 meter, and dipped one-fifteenth of an inch into a single drop of 
 Schuylkill water, gave an instant deflexion of 12. 
 
 With a small Melloni thermo-multiplier of twenty pairs, the 
 heat from the face of one of the observers, at a distance of eight 
 feet, gave a deflexion of 68. 
 
 The needle can be brought to rest, after a deflexion of 90 , in 
 a very few seconds, by alternating the current by means < 
 pole-changers. .. 
 
 The needles are remarkably astatic, having a very small 
 tive power, and standing steadily in an east and west position, 
 with a slight trouble in setting them, Mr. Weygandt mentions 
 that the power of the needles was balanced by rubbing the 
 stronger one lightly upon an oil-stone, which appeared to weaken 
 
542 THE COMMON EUDIOMETER. 
 
 without removing any sensible part of its weight. Altogether, 
 the instrument is very remarkable for its high finish, extreme 
 delicacy, and great convenience in use, the arrangement of the 
 pole-changers enabling the observer to make many observations 
 in a short time, by the great ease in bringing the needle to rest 
 by changing the current rapidly. 
 
 APPLICATIONS OF ELECTRICITY. Electricity proper has its 
 most general application in the chemical analysis of gaseous mix- 
 tures, being the convenient and efficient means by which they are 
 exploded and decomposed. It is employed in connection with the 
 eudiometer, an instrument, as its name indicates, chiefly intended 
 for determining the purity of the air, but by means of which other 
 gases, containing carbon and hydrogen, are occasionally examined. 
 These latter are made to unite explosively, in it, with oxygen ; 
 while in the examinatioit of the atmosphere, the explosion of hy- 
 drogen with its constituent oxygen, and the consequent produc- 
 tion of water, and diminution of volume, enable the chemist to 
 determine the proportion of its ingredients. It would be foreign 
 to our purpose to give a full description of all the applications of 
 eudiometry; but a short account of the means most commonly 
 employed, particularly in reference to the proper mode of apply- 
 ing the electric spark, will scarcely be at variance with the prac- 
 tical nature of this work. 
 
 The Common Eudiometer is a short tube of thick glass, having 
 one end closed. This' tube is graduated, and near its closed ex- 
 tremity, two stout wires of platinum, or other metal, intended for 
 the transmission of the spark, are inserted in the opposite sides, 
 their ends inside of the tube being a short distance apart. The 
 other end of the tube serves for the introduction and escape of 
 the gas, and it remains constantly immersed in the liquid over 
 which the experiment is made, the tube being supported in a per- 
 pendicular position. The gas to be subject to the spark is gene- 
 rally such a mixture as will inflame explosively at once, though 
 sometimes a gradual combination of some of its elements is 
 effected by a long-continued succession of sparks. The tube, 
 being filled with water or mercury, may be placed over the trough ; 
 or, for the purpose of more accurately determining the level of 
 the gas in the way about to be described, it should be supported 
 over a glass vessel containing the proper liquid. The gases are 
 
THE COMMON EUDIOMETER. 543 
 
 then successively introduced into it, in the proper proportions, 
 after the manner heretofore described. To determine their 
 volumes with the utmost degree of accuracy, it is necessary to 
 support the tube by a forceps or a cork-lined clamp, as repre- 
 sented m the figure, and not between the fingers, so that their 
 
 Fig. 463. 
 
 temperature and volume shall not be increased by the heat of the 
 hand. To insure that the gas be submitted to no more pressure 
 than that of the atmosphere, the eudiometer should be raised in 
 such a manner that the interior level of the liquid contained in 
 it, shall be exactly at the same height as that of the liquid in the 
 vessel outside. In order to secure this, it is necessary that the 
 eye of the observer be in the same plane as the two levels of the 
 liquid, and that the line of the liquids in direct contact with the 
 glass inside and outside of the tube, be not taken as the proper 
 standard. It must be recollected that, as the edge of a surface 
 of water, in contact with the glass, is elevated above its true 
 level by capillarity, and that of mercury in the same circumstances 
 is depressed, the lower line in the former case, and the upper 
 one in the latter, will give the true position of the main surfaces. 
 The exterior of the tube is now wiped clean, so that no mercury 
 or water in contact with the wires, can conduct off the electricity. 
 The tube, kept upright, should then be clasped firmly in the hand 
 by its middle, and its lower end, still under water, should be 
 closed with slight force by the thumb or a finger of the unoccu- 
 
544 THE COMMON EUDIOMETER. 
 
 pied hand. This permits the descent of the fluid, which is driven 
 out by the force of the explosion, while it does not allow its too 
 sudden return upon the subsequent contraction of the gaseous 
 contents of the tube, or the escape of any of the latter. 
 
 In using the eudiometer, we must take into account the relative 
 degree of explosibility of different mixtures. Thus a mixture of 
 oxygen and carbonic oxide expands when inflamed, much less 
 than one of oxygen and hydrogen or olefiant gas. A large 
 quantity of any mixture will of course increase in bulk much 
 more than a small one. The whole quantity of gas contained at 
 first in the tube, should be at least so small, that after expansion 
 it shall not occupy quite the whole of the eudiometer. No more 
 gas should be introduced for detonation than will occupy a sixth 
 of its capacity at common temperatures, and generally it will be 
 advisable to employ much less. 
 
 The spark which is intended to effect the detonation or slow 
 union of the gases contained in the tube, may be derived from 
 the electrophorus, the prime conductor of the electrical machine, 
 or the Leyden jar, the power of the last two being of course 
 greater, in the order in which we have spoken of them, than that 
 of the first. When the electrophorus is employed, one of the 
 wires upon the side of the eudiometer is placed in connection 
 with a finger of an assistant, or with a metallic chain, the other 
 end of which hangs in the trough or vessel over which the tube 
 is supported. The ball of an excited electrophorus is then brought 
 near to the other wire, and the spark obtained from it, passing 
 from wire to wire through the interior of the tube, inflames the 
 mixture, if it be of sufficient intensity, and if all the other cir- 
 cumstances are favorable. The ball upon the conductor of the 
 electrical machine may, in the same way, be made to approach 
 one of the wires, with usually a more powerful effect. The em- 
 ployment of the electrical machine is particularly advantageous 
 when it is desired to pass a succession of sparks for a consider- 
 able time through the mixture, for the purpose of effecting a gra- 
 dual combustion or combination of the gases contained in the 
 tube. The use of the Leyden jar is equally convenient for a 
 single contact, and much more apt to be attended with success, 
 on account of the greater size and force of the spark. One of 
 the wires may be connected with the external coating of the jar, 
 
URE'S EUDIOMETER. 545 
 
 by means of a chain or hooked wire, and a discharger or other 
 conductor, applied at one end to the ball of the vial, may be 
 brought near the other wire. When other means of connection 
 are not at hand, the operator, at the risk of receiving an unplea- 
 sant shock, may grasp the jar in his hand, and apply its ball to 
 one wire of the eudiometer, while he touches a finger of the other 
 hand to the opposite wire. To insure the explosion of the mix- 
 ture, a spark of the largest size that can be obtained from the 
 electrical instrument, should be passed through it. Very often, 
 although a sufficient amount of electricity is given off from the 
 conductor of the electrophorus or electrical machine, its effect is 
 lessened by its communication from wire to wire, as an electrical 
 brush, or in a succession of small sparks. To remedy this evil, 
 a ball, half an inch or more in diameter, should be placed upon 
 the outer extremity of that wire which is to receive the spark, 
 and the latter should always be given off from the surface of a 
 ball of considerable size. 
 
 The wires of the eudiometer must be firmly fitted in their 
 places, and the openings in the glass through which they enter 
 should be hermetically closed around them. Before filling the 
 tube with gas, it must also be ascertained that they are perfectly 
 insulated. When the detonation is effected over water, a film of 
 it is apt to adhere to the glass and wires, both internally and 
 externally, which, by its conducting power, sometimes diminishes 
 the force of the spark, or intercepts it entirely. To prevent 
 this, the outside of the tube and wires must be wiped as dry as 
 possible before applying the conductor. The top of the tube 
 should be gently tapped so as to shake off any particles of mois- 
 ture adhering to it within. The perfect transmission of a large 
 spark is only secured by the presence of the balls upon the ends 
 of the wire and discharger, as before described. 
 
 Ures Eudiometer. Analysis of gases by explosion is much 
 more conveniently performed by means of Dr. Tire's syphon 
 eudiometer, shown in Fig. 464. It differs from the other eudio- 
 meter in being curved like the letter U ; but, like it, it has the 
 part intended to contain the gaseous mixture graduated and 
 pierced by two platinum wires. It is usually about twenty inches 
 in length, and the third of an inch in internal diameter. This 
 instrument, like the other, may be used for the analysis of va- 
 
 35 
 
546 URE'S EUDIOMETER. 
 
 rious gases over either water or mercury, but it is applied chiefly 
 to that of atmospheric air over the latter liquid : and we will con- 
 fine ourselves to a short account of this em- 
 Fig. 464. 
 
 ployment of it. When about to be used for 
 
 an examination of the atmosphere, it is filled 
 with mercury, and the required amount of air 
 is introduced into the open end, which is in- 
 verted over the trough, as in the case of the 
 use of the other form of the tube. This end 
 is then tightly closed with the finger, and the 
 tube is turned slowly so as to admit the air 
 into the graduated extremity. The instru- 
 ment is then held upright, and the amount of 
 air introduced is read off by looking at the 
 scale, after subjecting it to atmospheric pres- 
 sure by displacing, with a stick thrust in, that portion of mercury 
 which is above the level of that in the graduated limb. This 
 having been accurately done, the open part is again filled with 
 mercury, closed with the finger, inverted into the liquid, and an 
 amount of pure hydrogen is introduced equal, as nearly as can be 
 guessed, to half the volume of the air. The quantity of hydro- 
 gen added is then accurately estimated by returning the eudio- 
 meter to the erect position, equalizing the surface of the mercury 
 as before, and reading off its level. The instrument is then held 
 in the way represented in the figure, the thumb firmly closing its 
 aperture, and the knuckle of the forefinger touching the nearer 
 platinum wire. The explosion is produced by the aid of the 
 electrophorus, prime conductor, or charged jar, as before de- 
 scribed, the violence of the expansion being moderated by the 
 spring-like action of the air contained in the open limb. The 
 level of the mercury is again equalized by pouring into the open 
 side enough to produce that result, and the volume of the gaseous 
 mixture is then finally read off. 
 
 The loss in volume of the mixture, which is produced by the 
 explosion, gives, by a very simple process, the amount of oxygen 
 originally contained in the air. As hydrogen unites with oxy- 
 gen to form water in the proportion by measure of two to one, 
 one-third of the diminution must be due to the oxygen of the air 
 introduced. Thus, if 100 measures of air and 50 of hydrogen 
 
ELECTRICITY DEVELOPED BY GALVANIC ACTION. 54 7 
 
 have been introduced, and if the mixture contain only 87 mea- 
 sures after explosion, the diminution has been that of 63 measures. 
 One-third of the loss is equal to 21 measures, which represents 
 
 duced f the air 
 
 The same precautions are to be observed in manipulating with 
 this instrument as directed for the common eudiometer. 
 
 ELECTRICITY DEVELOPED BY GALVANIC ACTION.! All the 
 foraw of apparatus for the purpose of producing a continuous 
 electrical current, are called galvanic circuits, and those in com- 
 mon use consist of two metals, one more oxidable than the other 
 and of a liquid, which, by its action upon the readily oxidized or 
 active metal causes the development of the influence. The old 
 voltaic pile and the crown of cups are the most simple examples 
 of galvanic apparatus. The former consists of a series of disks 
 of zinc and copper, platinum or silver, arranged in a column, 
 each piece of different metal having placed between it and its 
 neighbor a disk of cloth, or paper, steeped in some liquid which 
 acts chemically upon the zinc. The crown of cups is differently 
 arranged, but upon the same principle. A number of cups are 
 placed in row or circle, each one containing an exciting liquid, 
 such as dilute sulphuric acid, and a plate of zinc, and one of the 
 inactive metal. The zinc of one cup is connected by a wire with 
 the copper or other metal of the next cup, and the zinc of that 
 is also connected with the copper of the one beyond it. The two 
 external plates of both kinds of series have wires soldered to 
 them, which are called the poles. In this way a communication 
 exists between all the parts of the series, directly between the 
 alternate plates of the different cups, and indirectly through the 
 liquid between those in the same cup. A simple circuit, as exhi- 
 bited by the most elementary form of either of these arrange- 
 ments, represents in miniature all the other kinds of voltaic ap- 
 paratus employed. Thus, if a single cup be used, containing a 
 plate of zinc and one of copper, immersed in dilute acid, and 
 having wires attached to them, the voltaic current is supposed to 
 be developed upon the surface of the zinc, along with its partial 
 solution and the evolution of hydrogen, to pass through the liquid 
 to the copper, and to be conducted through that metal to the end 
 of its wire, which forms the anode or positive pole. The end 
 
548 ELECTRICITY DEVELOPED BY GALVANIC ACTION. 
 
 of the wire attached to the zinc is the kathode or negative pole. 
 When these poles are placed in contact with each other, or with 
 a conductor of the fluid, the electricity originally developed upon 
 the surface of the zinc returns to it from the positive wire through 
 the negative one ; and if the current be sufficiently powerful, the 
 various phenomena of voltaic light, heat, electro-magnetism, 
 chemical decomposition and action on the living body, are capable 
 of being exhibited during this passage from pole to pole. 
 
 In most of the forms of compound circuits, where a number of 
 pairs of plates are arranged together in a battery, the wire at- 
 tached to the terminal zinc plate becomes the positive pole, and 
 that of the last copper plate the negative one. This arises from 
 the fact that in these arrangements the last two plates are actu- 
 ally superfluous, not being so much producers of the galvanic 
 fluid, as conductors of that which has been generated in the 
 intermediate parts of the apparatus. 
 
 The more oxidable of the metals should form a readily soluble 
 salt with the exciting liquid. If both 'metals are easily acted 
 upon by the liquid, the electrical current produced by one will be 
 overcome in proportion to the action of the liquid on the other. 
 So that the most power will be obtained by having one metal 
 that is easily acted upon and another that will remain unchanged 
 in the liquid. The metal dissolved is always the positive metal, 
 and the unchanged metal the negative element. Thus, in an 
 acid solution, silver is positive to platina and negative to zinc. 
 
 The following table of substances shows their electrical rela- 
 tion to each other in sulphuric acid, commencing with the most 
 positive, and each element being respectively positive and nega- 
 tive to those that precede and follow it. 
 
 Potassium, Bismuth, 
 
 Barium, Nickel, 
 
 Zinc, Silver, 
 
 Cadmium, Antimony, 
 
 Tin, Palladium, 
 
 Iron, Gold, 
 
 Lead, Charcoal, 
 
 Copper, Platinum. 
 
 The conducting power of bodies is different. Fluids are gene- 
 rally imperfect conductors ; the metals and carbon are the best. 
 
WOLL ASTON *S BATTERY. 549 
 
 Some of the metals are better conductors than others; the relative 
 conducting power of eight of them, is as follows : 
 
 Silver, ... 100 
 
 Copper, ... 100 
 
 Gold, . 'S-.. > ;; . 67 
 
 Zinc, . . . 33 
 
 Platinum, ... 20 
 
 Iron, ... 20 
 
 Tin, Skate . . 17 
 
 Lead, ,*' ' . . 10 
 
 The efficiency of a battery, as regards intensity and quantity, 
 depends upon the amount of surface of the positive metal acted 
 upon, the distance between the positive and negative elements, 
 the purity of the materials, the size and length of the connections, 
 the temperature of the atmosphere, and the good condition of all 
 the parts of the battery, and complete connections. 
 
 In constructing batteries, only the purest zinc should be used ; 
 and especial care should be taken to prevent its contamination 
 with tin, which always shows itself by rising in flocculent masses 
 to the surface of the solution. 
 
 To prevent local action in the batteries, which is occasioned by 
 impurities in the zinc, the zinc should be amalgamated by first 
 dipping it in chloro-hydric or sulphuric acid, and then quickly 
 immersing in mercury, of which they should be made to absorb 
 as much as possible. The excess of mercury is removed with a 
 cloth, and the zinc well rinsed with water. Two and one quarter 
 ounces of mercury will amalgamate a square foot of zinc surface. 
 When batteries are not in use, all the parts should be removed 
 from the vessels containing the liquids, well washed, and kept 
 covered from the dust. 
 
 Wollaston's Battery. This is the very best of the old forms, 
 of the voltaic battery. It consists, as shown in Fig. 465, of a 
 number of zinc and copper plates, the latter entirely encircling 
 the former except at the edges, and the two metals being kept 
 apart by pieces of cork or wood. Each plate of zinc is soldered 
 to the one of copper which is before it in the series, and the 
 whole arrangement is screwed to a bar of dry mahogany, which 
 permits its elevation from or depression into the acid. This is 
 contained in an earthenware trough, divided by partitions into 
 compartments, each one of which receives a single pair. The 
 exciting liquid is made of a mixture of 100 parts by measure of 
 water, 2J parts of sulphuric acid, and 2 parts of strong nitric 
 acid. In the same manner that the shock of the Leyden jar i% 
 
550 WOLLASTON'S BATTERY. 
 
 increased by combining it with others in a battery, the power of 
 this apparatus can be multiplied to any desired extent, by uniting 
 
 Fig. 465. 
 
 it by means of strips of copper, passing from the zinc of one 
 instrument to the copper of another, with any desired number of 
 similar batteries. 
 
 The chief objection to the use of this and like forms of appa- 
 ratus is what is called the local action, which, in it, is very great, 
 and which gives rise to a rapid diminution of power and corrosion 
 of the zinc. 
 
 The bubbles of hydrogen given off from its surface, adhere to 
 the zinc, preventing perfect contact with the exciting fluid ; some 
 of the electricity is dissipated by the escaping gas, and the sul- 
 phate of zinc which is formed, is in part reduced to the metallic 
 state, in a crust upon the surface of the copper. All of these 
 circumstances form serious objections to the use of this battery 
 where a long-continued action is desired. 
 
 When common zinc is exposed to dilute sulphuric acid, it is 
 rapidly dissolved, and this solution and loss of material in the 
 common batteries are excessive and entirely disproportional to 
 the amount of galvanic fluid given off. This, which is the local 
 action, is supposed to arise from a number of little voltaic circles 
 being formed by the presence in the zinc of particles of plum- 
 bago, and of other metals which excite the rapid erosion of 
 parts of its surface. This evil can only be prevented, as before 
 directed, by carefully amalgamating the surfaces of the zino 
 plate. 
 
DANIELL'S CONSTANT BATTERY. 551 
 
 A single pair of Wollaston's battery is very efficient in the 
 production of the phenomena which are due to the evolution of a 
 quantity of electricity, such as ignition and deflagration on a 
 small scale, the deflection of the magnetic needle, and the various 
 electro-magnetic experiments. Its intensity or electro-chemical 
 power is very much increased, as before stated, by combining it 
 with other similar arrangements. 
 
 The plates of the old form of voltaic apparatus should be 
 removed from the acid, and washed with water after the comple- 
 tion of each experiment, or if they are permanently connected 
 with the trough, the acid in it should be poured out, and reserved 
 for future operations. In Wollaston's battery, the plates are 
 taken out by elevating the mahogany bar to which they are at- 
 tached, and freed from acid and metallic deposit by washing with 
 water, and are then either suspended over the trough by a cord 
 attached to a support above, or are placed upon a tile or old table 
 until their next employment. As the acid solution soon becomes 
 unfit for use from the large amount of sulphate of zinc dissolved 
 in it, it must be removed after reaching a certain point of satu- 
 ration. The best evidences of the cleanliness and perfect con- 
 nection of the surfaces, and of the activity of the liquor, are 
 afforded by the constant bubbling up of hydrogen during the 
 action, and by the ordinary voltaic phenomena exhibited at the 
 poles. 
 
 Daniel? s Constant Battery. This is a far better form of ap- 
 paratus than the one last described, and has the advantage over 
 it of being comparatively permanent in its 
 action. The local action being obviated by Flg< 466> 
 
 the amalgamation of the zinc, it is of course 
 much more applicable to those purposes of 
 electro-chemical examination in which long 
 continued and uniform transmission of the 
 fluid through a body is desired. In its 
 simplest form, it consists of a copper cylinder 
 A, 3 or 4 inches in diameter, and from 6 to 
 18 inches in height, containing in its interior 
 a cell of porous earthenware or of animal membrane, within which 
 is suspended a rod of zinc, three-quarters of an inch in diameter, 
 which has been carefully amalgamated by rubbing its surface 
 
552 DANIELL'S CONSTANT BATTERY. 
 
 with mercury by means of a cloth previously dipped in dilute 
 sulphuric acid. The earthen cell or membrane containing the 
 zinc is filled with a mixture of one part by measure of sulphuric 
 acid and 8 parts of water, and the space between it and the outer 
 copper cylinder contains a saturated solution of sulphate of cop* 
 per, the surface of which should be upon the same level as that 
 of the solution within the cell. The solution of blue vitriol is 
 prepared by pouring boiling water over an excess of crystals of 
 the salt, and stirring constantly until it is saturated. 
 
 To this solution, a little sulphuric acid, never amounting to 
 more than one-tenth part by measure, of the whole, should be 
 added. In order that this liquor be kept concentrated, a little 
 perforated copper shelf, seen in the figure, is usually placed upon 
 the inside of the cylinder, within an inch or two of the top. This 
 is intended to contain a supply of crystals of the sulphate. They 
 are placed at the upper part of the liquid, because that portion 
 becomes exhausted first, and because the saturated solution of the 
 crystals in its passage downwards diffuses itself equably. In the 
 absence of the shelf, a strong bag of loose texture, or a network 
 of copper wire attached to the top of the cylinder, may be used 
 to contain the crystals. 
 
 Attached to each metal of Daniell's battery is a binding-screw 
 to form connections. When wires are held in each of these, and 
 a communication from the cylinder to the rod is made, a power- 
 ful current is produced. In the figure, the extremity of z repre- 
 sents the positive pole, and that of x the negative one. In this 
 arrangement there is no evolution of hydrogen, and no local 
 action upon the zinc or consequent unnecessary erosion of its 
 surface. The interior of the copper cylinder becomes covered 
 with a compact deposit of metallic copper, from the decomposi- 
 tion of the oxide by the nascent hydrogen. 
 
 The intensity or power of producing electro-chemical decom- 
 positions of this battery, may be much increased by associating 
 it with a number of others. Ten pairs, so arranged that the 
 inactive metal of one is attached, by copper wires or strips, to the 
 active metal or the zinc of the next, make a most powerful com- 
 pound circuit, quite sufficient for nearly all the purposes of the 
 chemist. 
 
 Daniell's battery may be constructed very simply and cheaply, 
 
SMEE'S BATTERY. 553 
 
 by immersing in a tumbler or jar containing a solution of sul- 
 phate of copper, a copper plate of the proper size, bent into the 
 form of a cylinder, and having suspended in its centre upon a 
 piece of wood supported on the top of the outer vessel, an amal- 
 gamated zinc bar. This is surrounded by a piece of bladder or 
 of the intestine of an animal, tied at its lower part, and contain- 
 ing the acid liquor. Bags of very firm sail cloth, well sewn, 
 make excellent diaphragms, and resist the action of the acid for 
 a long time. Cylinders made by cementing coarse strong brown 
 paper, at the edges and bottom, also answer perfectly well. The 
 terminal wires may be soldered upon the top of the metals with 
 which they are to be connected, and the solution of sulphate of 
 copper may be kept saturated by the means before spoken of. 
 Very little chemical action upon the surfaces of these batteries 
 goes on when the voltaic circuit is not completed ; nevertheless it 
 is proper always to pour out the contents of the diaphragm or to 
 disconnect the zinc bar after each use of them. The liquid may 
 be kept in a separate vessel, and employed in future experi- 
 ments. The solution in the outer cylinder may be allowed to 
 remain. 
 
 Smee's Battery. This simple and powerful apparatus is chiefly 
 used to excite the precipitations of metals in the electrotype or 
 galvano-plastic processes. As commonly con- 
 structed and shown in Fig. 467, it consists of 
 two plates of amalgamated zinc, clamped to 
 a piece of wood by means of a bent strip of 
 brass, and furnished with a binding-screw. 
 Between the plates of zinc is fixed one of 
 platinized silver, connected at its upper end 
 with another similar screw. The silver is 
 covered over with a thin layer of platinum, 
 by first roughening the surface with strong 
 nitric acid, and, after washing, placing it in a 
 vessel of water acidulated with sulphuric acid, to which a little 
 chloride of platinum has been added. A porous vessel of pipe- 
 clay or earthenware, or an animal membrane, with a plate of zinc 
 in its interior, and containing dilute sulphuric acid, is then im- 
 mersed in the other receptacle, and the silver and zinc are 
 connected together by a wire. The platinum precipitates upon 
 
554 GROVES'S BATTERY. 
 
 the silver surface as a dark and granular but closely attached 
 deposit. 
 
 This rough surface of the silver plate, presenting myriads of 
 minute conducting points, greatly facilitates the evolution of hy- 
 drogen. The only liquid used to excite this battery consists of 
 one part of sulphuric acid, and seven of water. The addition of 
 a few drops of nitric acid makes it act with greater intensity, 
 but it is not advisable to use it unless the silver is thoroughly 
 covered with platinum. 
 
 Another form of this battery consists of a glass vessel like a 
 tumbler, on which rests the frame which supports the metallic 
 plates. As in the other, two screw-caps on the top of the frame 
 allow the attachment of wires for the conveyance of the current. 
 One of these is connected with a central slip of platinum foil, on 
 each side of which descend amalgamated zinc plates, connected 
 above with the other screw. Like Daniell's batteries, a series of 
 these may be connected together, by making communication 
 between the alternate zinc and platinum plates. 
 
 Grroves's Battery. This is the most energetic battery known. 
 Its activity is very great, and though this prevents it from being 
 so well adapted for galvanoplastic operations, it is the one gene- 
 rally employed for the development of magnetism, and is in com- 
 mon use in the magnetic telegraph. 
 
 Various forms of this arrangement are met with, but in the 
 most common one, a strip of platinum foil, furnished above with 
 a screw-cap, is immersed in a cylinder of porous earthenware, 
 filled with strong and pure nitric acid. The cylinder is sur- 
 rounded by another one of amalgamated zinc, also provided with 
 a screw-cap, standing on short legs, and divided by a longitudinal 
 opening in one side, in order to permit the acid to circulate 
 freely around it. It is placed in a glass jar or tumbler, contain- 
 ing one part, by measure, of sulphuric acid, and eight of water. 
 When the circuit is completed by bringing together the wires 
 placed in the screws, the hydrogen from the decomposed water 
 in the outer vessel is not given off in the gaseous state, but pass- 
 ing through the diaphragm, combines with some of the oxygen 
 of the nitric acid, reducing it to nitric oxide. Some of this dis- 
 solves in the acid, and the rest escapes in the form of dense red 
 
BUNSEN'S BATTERY. 
 
 555 
 
 fumes of nitrous acid, formed by its combination with the oxygen 
 of the air. 
 
 This battery owes its intensity and rapidity of action to the 
 absorption of the hydrogen, the good conducting nature of the 
 materials, and the consequent concentration of the fluid. It has 
 been said to be, when properly prepared, about seventeen times 
 more powerful than that of Daniell. The great objection to its 
 use arises from the escape of the irritating and poisonous nitrous 
 acid, which is sometimes so considerable as to fill the apartment 
 with the fumes. 
 
 Bunsen's Battery. This is the same in principle as Groves's 
 battery, but is more economical, as a cylinder of porous coal is 
 used in place of platinum. It is represented in Fig. 468. A B 
 
 Fig. 468. 
 
 Fig. 469. 
 
 is a glass vessel filled up to B' B' with commercial nitric acid, c 
 and c' are hollow charcoal cylinders, dipping into the acid as far 
 as B" B", and resting on the edge of the glass by a flange. A 
 ring of zinc or copper P encircles the top of the charcoal cylin- 
 der, and terminates in an appendage P', for 
 connecting it with the wire. D D, which are 
 diaphragms of porous earthenware, contain 
 an amalgamated hollow zinc cylinder z z, with 
 its appendage P", also intended for communi- 
 cation, and which is immersed in dilute sul- 
 phuric acid. The connections are made by 
 means of the clamp A B, Fig. 469, and screw v, which are shown 
 in place at H, Fig. 468. The perfect contact of these appen- 
 
556 CONNECTION OF BATTERIES. 
 
 dages, screws, and the ribbons or wires of copper connected with 
 them, must be secured, by keeping them clean and bright by 
 rubbing with sand paper. When the battery is about to be used, 
 the glass vessel is half filled with equal parts of commercial nitric 
 acid and water, and the diaphragm with water acidulated with 
 sulphuric acid. The coal cylinder is prepared by pressing a 
 thorough mixture of one part of caking coal and two of coke with 
 a little rye flour, into a cylindrical mould of sheet-iron, in the 
 centre of which is a core of wood or pasteboard. The mould, 
 after being closed by a movable cover well luted on, is heated 
 gradually to redness, and the calcination is continued until the 
 disengagement of gas ceases. The cylinder is then taken out, 
 soaked in a strong solution of molasses, dried, and again cal- 
 cined by an intense heat, in order to increase its firmness of tex- 
 ture. After this, its surface may be smoothed off with a file, or 
 in a lathe. ; 
 
 This battery is said to be almost equal to Groves's in power. 
 Professor Bird has constructed one similar to it by the use of a 
 black lead crucible. He ignited the crucible for a short time, 
 and, when thus prepared, filled it with nitric acid, and wound a 
 wire tightly around its outside, making it serve both as a support 
 and as the conductor of the fluid. A bar of amalgamated zinc, 
 also connected with a wire, was then placed in a porous cylin- 
 der containing dilute sulphuric acid, and the whole was immersed 
 in the acid of the crucible. He states that, although powerful, 
 it is much inferior to Groves's battery. 
 
 In the use of any of the above-described batteries, care must 
 be taken not to fill either of the receptacles too full of the liquid, 
 since on immersing the metals or charcoal, some part of it might 
 overflow and mix with that of the other vessel, to the injury of 
 the surfaces. After the insertion of the cylinders or bars, the 
 surfaces of the two liquids must be as nearly as possible upon the 
 same level ; any deficiency in this respect must be regulated by 
 the addition of more fluid. 
 
 Connection of Batteries. The connection between the dif- 
 ferent plates of batteries is very conveniently made by means of 
 the binding-screw, Fig. 470. The wire by which the communi- 
 cation is established is passed through the hole in the side, and 
 kept in its place by the movable screw in the top. The screw 
 
WIRE FQE BATTERY PURPOSES. 
 
 557 
 
 below serves to fasten the arrangement firmly into a hole of the 
 proper size, in the top of either plate. The operator should be 
 supplied with a number of these, as they permit him to unite and 
 
 Fig. 470. 
 
 disconnect the different parts of an apparatus with the greatest 
 ease and rapidity. They are shown in the figure, attached to the 
 copper and zinc plates of a simple circuit, with the wires, of which 
 the ends form the poles, passing through them. 
 
 Wire for Battery Purposes. Copper wire is more often em- 
 ployed for connecting the different parts of a voltaic circuit than 
 any other, on account of its high conducting power, its flexibility, 
 and its not being susceptible of magnetization by the passage 
 through or around it of a galvanic current. Its thickness should 
 be proportioned to the energy of the battery, and it should be as 
 short as possible, because a great length of wire causes resistance 
 to, and loss of the fluid proceeding from a battery of moderate 
 power. Its connecting parts, as well as those of the plates or 
 screws to which it is attached, must be bright and clean. In 
 order to insure perfect contact, it is advisable to amalgamate the 
 extremities of the wire ; which is done by washing them with a 
 solution of nitrate of mercury, and dipping them afterwards in 
 metallic mercury. 
 
 When it is desired to break and renew the connections often or 
 very rapidly, the common mode of attaching the wires is found 
 to be inconvenient. In that case, a little cup made of copper, or 
 other metal which does not too readily amalgamate with mercury, 
 is partly filled with that metal, and the wires are received in the 
 cup, a depression in the bottom of the latter being often made so 
 as to hold them more firmly in their place. By keeping one of 
 the wires immersed in this cup, the connection may be made 
 
558 ELECTROLYSIS. 
 
 complete or broken at will, and without disarranging any part of 
 the apparatus, by simply placing the extremity of the other wire 
 in its appropriate cup, or taking it out. 
 
 The wires are, in one point of view, the most interesting parts 
 of the battery, as it is at their extremities, or the electrodes, that 
 the most important phenomena of galvanism are exhibited. Their 
 size and length should be adapted to the power of the battery. 
 
 Electrolysis. Any one of the batteries already mentioned may 
 be employed for the purpose of producing chemical decomposi- 
 tions, by passing the current from them through the substance, 
 from pole to pole, of the terminal wires of the series. As electro- 
 chemical changes are usually effected most perfectly by a current 
 of intensity, as distinguished from one of quantity, which is more 
 active in producing light, heat, and electro-magnetism, a number 
 of pairs of plates or cylinders, varying with the difficulty of the 
 decomposition, are employed. The other results spoken of are 
 generally obtained by using a small number of plates with large 
 surfaces. A combination of small batteries, made upon the plan 
 of Daniell's, is, perhaps, the most active of all in producing 
 chemical change. 
 
 Whatever form of apparatus is used for such decompositions, 
 particular attention must be paid to the proper connection of the 
 alternate metals, and to the close contact of the wires, as well as 
 the other circumstances before spoken of in reference to their 
 relative size. The points of the wires should, in most cases, be 
 made of platinum, as that metal is the best conductor of the fluid, 
 and is not liable to be chemically acted on by any of the sub- 
 stances evolved from the electrolyte. 
 
 Any one of the class of bodies called electrolytes, which includes 
 all those known to be capable of decomposition by electricity, 
 may be exposed to the voltaic influence by being placed between 
 the electrodes or extremities of the wires, so as to be the medium 
 of communication between them. This is effected in various ways, 
 as the substances differ in being solid or fluid, and good or bad 
 conductors of the influence. 
 
 Many solutions, like that of iodide of potassium, admit very 
 readily of decomposition. A solution of this salt may be easily 
 decomposed by a battery consisting only of a wire of zinc and 
 one of copper. Water alone, however, may require the power of 
 
ELECTEOLYSIS. 559 
 
 a number of cells of Darnell's battery to separate it into its ele- 
 ments. The addition of a little common salt, or of almost any 
 saline body, will make the electrolysis of it much more easy by 
 increasing its conducting power. 
 
 In the decomposition of water, and, indeed, in most cases in 
 which gaseous components of bodies are eliminated from liquids, 
 platinum strips are attached to the ends of the wires, thus making 
 the surfaces of contact much greater. These strips, which may 
 be made of platinum foil, are placed parallel and as close to each 
 other as is possible, without their being actually in contact. 
 Their touching each other would effectually prevent all chemical 
 action, as the voltaic fluid would be directly transmitted through 
 the wires from the positive to the negative plates. 
 
 When the electrodes are placed in a vessel of water, and the 
 battery is made to act properly, bubbles of hydrogen will ascend 
 from the end of the wire or foil connected with the negative end, 
 and oxygen from that of the positive one. These gases can be 
 collected in a tube closed at one end, or a jar previously filled 
 with water, and inverted over the wires ; or they may be sepa- 
 rately received in different vessels. As water consists of two 
 volumes of hydrogen and one of oxygen, of course the quantity 
 of the first given off, will be twice that of the last. Fig. 471 re- 
 Fig. 471. 
 
 presents a mode of effecting this decomposition in which the 
 terminal wires of a trough arrangement are passed through a 
 perforated cork into water contained in a funnel. The end of 
 each wire is placed directly under a test-tube previously filled 
 with water, and inverted in the funnel. The ascending gases 
 
560 ELECTROLYSIS. 
 
 displace the water, occupy the tube, and may, if necessary, be 
 accurately measured. 
 
 As the quantity of electricity set in motion by the battery is 
 in direct proportion to the amount of zinc dissolved in it, so are 
 the effects of chemical decomposition always proportionate to the 
 former; this being thus always in a certain relation with the 
 equivalents both of the products of electrolysis and of the portion 
 of zinc acted upon. Thus, one grain of hydrogen, given off at 
 the negative pole, indicates that thirty-three grains of zinc have 
 been dissolved during the time of the action. Upon this prin- 
 ciple Faraday constructed his voltameter, which affords the only 
 means known of accurately measuring the galvanic influence. 
 That form of this which is most employed, is one in which strips 
 of platinum foil, attached to the wires of a battery, are placed 
 opposite and near to each other in a jar. or bottle, from which a 
 tube issuing, enters under a graduated jar inverted over the 
 pneumatic trough, all of these vessels being full of water. By 
 the measure of the gases collected, the quantity of electric force 
 can be estimated. By placing strips of platinum upon the ends 
 of the wires in Fig. 471, and substituting a single graduated tube 
 with a wide or funnel-shaped mouth, for the two which are seen 
 in the cut, the same result may be attained. 
 
 Faraday describes a convenient form of tube for the collection 
 and examination of gases evolved from either electrode, in expe- 
 F . 4?2 riments conducted upon a small scale. This tube, 
 represented in Fig. 472, is filled with the solution 
 to be acted upon, and held in the position repre- 
 sented. The nature of the gas to be collected, 
 depends on the end of the battery, which is fastened 
 to the curved wire at a. The other electrode is 
 to be loosely inserted at b, so as to allow the gas 
 given off from it, to escape through the open orifice. 
 It should not be placed so far within the extremity 
 of the tube as to permit any bubbles of the gas to pass around 
 the bend, and to mix with that in the upright limb. The wire b 
 is to be removed when a sufficient amount of gas has been col- 
 lected, and the latter can then be transferred to a suitable vessel 
 and examined. 
 
 The methods of subjecting substances to the action of the bat- 
 
HEAT AND LIGHT FROM GALVANISM. 561 
 
 tery are very numerous. "When the electrolyte is a fluid, it may 
 be placed in any one of a great variety of suitable receptacles. 
 In all cases it must be recollected that the electrodes should be 
 brought as near together as possible, so that the small amount of 
 the substance which is directly between them, shall have the full 
 effect of the current concentrated upon it. Decompositions of a 
 drop of fluid may be made by placing it upon a glass plate, and 
 bringing the poles in contact with its sides. Larger quantities 
 may be received in a watch-glass or other concave piece of glass, 
 or in a cup of the proper size. A very convenient mode of sub- 
 jecting liquids to the current, so that the results of the decompo- 
 sition can be easily inspected by the observer, is that of closing 
 one end of a piece of glass tube tightly with a cork, and support- 
 ing it in an upright position by passing one of the wires of the 
 battery perpendicularly through the cork. The tube may then 
 be filled with the liquid, and the other wire, bent downwards, 
 may be immersed in it, and placed alongside of its fellow. In 
 nearly all such decompositions, the ends of the poles should be 
 armed with strips of platinum foil, on account of the greater 
 surfaces of contact presented by them. 
 
 When it is desired to direct the electrolytic influence upon a 
 large surface of a liquid, a piece of platinum foil attached to one 
 pole may be hollowed out into a cup-like form, and the substance 
 may be placed in it ; or the terminal wire may be made to support 
 and communicate with a platinum crucible, by being wound around 
 it. The other wire can then be immersed in the liquid, and pre- 
 vented from touching the vessel by the intervention of a piece of 
 glass tube. 
 
 Production of Heat and Light by Galvanism. The physical 
 effects of galvanism, among which are the production of heat and 
 light, result generally from the passage of a current of great 
 quantity and of feeble intensity, through an insufficient and im- 
 perfect conductor, the resistance of the latter impeding the cur- 
 rent, and increasing its calorific power. The batteries employed 
 for fusion and deflagration generally consist of a very small 
 number of pairs with extensive surfaces, which will develop a 
 great quantity of electricity. Usually these are the best batteries 
 for physical experiments, but occasionally those consisting of a 
 large number of plates are found useful for such purposes. A 
 
 3G 
 
562 HEAT AND LIGHT FROM GALVANISM. 
 
 single pair of very moderate size will effect these results in a small 
 way. Thus, Dr. Wollaston fused a very fine wire of platinum by 
 means of a small battery, made of a lady's thimble and a rod of 
 zinc. We have before stated that the intensity or decomposing 
 power of the galvanic fluid is increased by placing batteries in 
 connection so as to multiply the number of plates. Batteries 
 may also be associated together so as to increase their calorific 
 and light-producing power. Any number of troughs like Wollas- 
 ton's may, for this purpose, be placed, not as before, end to 
 end, but sidewise, and the cells at either end of each may be 
 connected with the same cells of the others by two wires going 
 across the series, and so bent as to be in perfect contact with the 
 last plates. The projecting ends of these wires on one side are 
 to be used as the poles of the battery. 
 
 Daniell's, or any other of the cell batteries, can be made 
 capable of producing the physical phenomena of electricity, by 
 paying attention to the size and conducting power of the wires or 
 other bodies to be heated ; but the quantity of the fluid is much 
 increased by connecting a number of them so as to make them 
 equivalent to a single pair. This can be done by connecting 
 together all the copper or platinum plates by means of wires, 
 either soldered to them or inserted into the binding-screws already 
 spoken of. The zinc bars or cylinders are to be brought into 
 contact in like manner, and the poles may be made by attaching 
 wires to any two of the opposite pieces of metal. 
 
 The wires of such batteries should all be made of larger size 
 than those which are employed in the ordinary arrangements. 
 
 When the electricity developed in a powerful battery is passed 
 through conical pieces of charcoal placed upon its poles, and 
 these are brought into contact, and then withdrawn to a short 
 distance from each other, the interval becomes occupied with a 
 brilliant spark or arch of flame, the light of which is often too 
 vivid to be borne by the eyes. The heat given out is also very 
 intense, and gases and other bodies are sometimes subjected to 
 its influence for the purpose of being decomposed. Carburetted 
 and sulphuretted hydrogen are both thus affected by it. The 
 wires may be twisted around two pieces of fine, well-burnt char- 
 coal, which are then brought together. The brilliancy of the 
 spark or arch passing between the points of charcoal, serves often 
 
HARE'S SLIDING-ROD EUDIOMETER. 563 
 
 to indicate the power and good condition of the battery. When 
 a very powerful current is set in motion, it is advisable not to 
 make the contact by means of the hands, but to use insulated dis- 
 chargers analogous to those employed in electrical experimer-ts. 
 The wires may be brought together and disconnected by means 
 of clamps or small vices attached to wooden handles. These 
 may be screwed on and taken off at pleasure. The charcoal used 
 in these experiments must be of the best quality. It is properly 
 prepared by packing pieces of box or other suitable wood, two 
 inches long, and a quarter of an inch thick, in an earthenware 
 crucible, and after covering them up with dry sand, heating them 
 until they cease to flame. The best pieces must be selected and 
 preserved for use in a well-stoppered vessel. 
 
 Various substances ignite and burn with brilliancy between the 
 galvanic poles. Metallic leaves or foil of different kinds may be 
 conveniently burned by taking them up upon the point of one 
 electrode, and bringing them in contact with a plate of polished 
 tinned iron, which is attached to the other. In this way the 
 different appearances and colors of their flames are shown. 
 
 A platinum wire stretched between the poles of a battery, will 
 attain a red or white heat, and, if offering sufficient resistance to 
 the passage of the fluid, may even be fused. It must not be too 
 thin, as the electricity may be sometimes so much retarded as to 
 produce no visible indications of heat. A wire of the proper size 
 will often remain at a red heat for a great length of time if a 
 constant battery is used. 
 
 The power possessed by the battery of igniting platinum wire, 
 enables us to apply heat in situations in which it would be diffi- 
 cult or impossible to do it by other means. By its use, substances 
 placed under water may be ignited or exploded, if necessary, at 
 a great distance from the operator. Out of the laboratory, it 
 may be employed for the purpose of exploding gunpowder in 
 mines, or under ships, and in other positions far removed from 
 the source of electricity: while, in it, it may be used for the ex- 
 plosive decomposition of various gases. 
 
 Dr. Hare has taken advantage of this power in the construc- 
 tion of his sliding-rod, aqueous, eudiometer. This instrument 
 consists of a glass vessel, with a capillary orifice closed by a 
 spring and lever in its top, and connected below with a socket, 
 
564 HARE'S CALORIMOTOR. 
 
 and a tube in which a graduated piston moves. A fine wire of 
 platinum is stretched across the middle of the vessel, between two 
 brass wires, which pass through the socket below, and terminate 
 in legs, which are made capable of connection with the cups upon 
 the poles of a battery. The instrument having been filled with 
 water, the gaseous mixture is drawn into it in the proper quan- 
 tities by pulling out the piston to regulated distances, and is then 
 exploded by the ignition of the wire, after the capillary orifice 
 has been closed. This last is now again opened, but under water, 
 enough of which enters to supply the vacuum produced by the 
 condensation. The amount of undecomposed air which remains, 
 is indicated by the distance through which the rod has to be 
 passed for the purpose of expelling it all from the glass vessel. 
 
 Dr. Hare uses for the ignition of the wire in this experiment, 
 his calorimotor of two pairs of plates. He has constructed a 
 variety of arrangements for procuring the heating effects of the 
 battery. In one of these, twenty sheets of copper, and the same 
 number of zinc plates, united separately to two bars of metal, 
 were secured in a wooden frame, so as to leave a space between 
 them of a quarter of an inch. A rope, passing over a pulley, was 
 attached at one end to the frame, and at the other to a counterpois- 
 ing weight. The frame could be lowered by means of the rope into 
 a cubical box containing the acid liquor. Another form of Hare's 
 battery is so constructed that the vessel containing the acid is 
 raised up to and lowered from the plates, when necessary, by 
 means of a lever connected with pulleys. By this most conve- 
 nient and powerful battery, constructed with a new arrangement 
 of the plates, the most intense galvano-ignition and deflagration 
 may be accomplished. 
 
 This apparatus, the description of which might, perhaps, have 
 been more properly introduced along with the account of other 
 batteries, is shown in Figs. 473 and 474. We extract the de- 
 scription of it from Hare's Compendium. 
 
 " The two forms of calorimotor, represented in Figs. 473 and 
 474, have been much used by me for what is described in my 
 Compendium as 'galvano-ignition.' (C, 335.) Within any 
 cavity, ignition of any intensity short of fusing platinum may be 
 produced, by making a platinum wire the subject of a galvanic 
 discharge from an instrument of this kind. I first resorted to this 
 
HARE S CALORIMOTOR. 
 
 565 
 
 process in the year 1820, for the purpose of igniting gaseous 
 mixtures in eudiometers of various forms. In June, 1831, I 
 applied it to ignite gunpowder in rock blasting ; and to this object 
 it was subsequently applied, agreeably to my recommendation, 
 by Colonel Pasley, Professor O'Shognessy, and others. 
 
 Fig. 473. 
 
 " This machine consists of sixteen plates of zinc, and twenty 
 plates of copper, each twelve inches by seven, arranged in four 
 galvanic pairs. The plates are supported within a box with a 
 central partition of wood A B, dividing it into two compartments. 
 Each of these may be considered as separated into two subdivi- 
 sions, by four plates of copper between the letters c c. Of course 
 the box may be considered as comprising four distinct spaces, No. 
 1, No. 2, No. 3, and No. 4. The circuit is established in the 
 following manner. Between the zinc plates of compartment No, 
 
566 ELECTRO-METALLURGY. 
 
 1, and the copper plates of compartment No. 2, a metallic com- 
 munication is produced by soldering their neighboring corners 
 to a common mass of solder, with which a groove in the wooden 
 partition between them is filled. With similar masses of solder, 
 two grooves severally made in the upper edges of each end of the 
 box are supplied. To one of them, the corners of all the copper 
 plates of space No. 1 and the zinc of space No. 4, are soldered. 
 To the other, the zinc plates of space No. 2 and the copper 
 plates of space No. 3, are soldered in like manner. Lastly, the 
 zinc plates of No. 3 are connected by solder in a groove, and the 
 copper plates of No. 4 are in like manner connected by solder in 
 another groove. Upon the ends s s of the solder just mentioned, 
 the gallows-screws are severally soldered, and to these the rods 
 p P, called poles, are fastened. The means by which the acid is 
 made to act upon the plates must be sufficiently evident from in- 
 spection. Depressing the handle causes the wheels to revolve, 
 and thus, by means of the cord which works in their grooved 
 circumferences, to lift the receptacle which holds the acid, until 
 this occupies interstices between the plates." 
 
 ELECTRO-METALLURGY. The deposition of metals by electric 
 action is one of the modern triumphs of practical chemistry. The 
 art dawned in 1805 with the discoveries of Brugnatelli ; but no 
 substantial benefits were derived from it until 1838, when Jacobi, 
 of St. Petersburg, and Spencer, of England, applied the prin- 
 ciple to the utilitarian purposes of life. The subsequent inven- 
 tion, by Daniell, of his well-known battery gave an impulse to 
 the art which resulted in many gratifying and wonderful improve- 
 ments ; so that now it has become, in its greatly advanced con- 
 dition, a prime element of the economy of many branches of 
 manufacture. Plating, gilding, stereotyping, medal copying, 
 engraving, and kindred arts, are all largely indebted to electro- 
 metallurgy for many of the facilities which at present promote 
 and distinguish their progress. 
 
 Those who may wish to experiment in this interesting branch 
 of scientific art will find ample instruction in the following pages. 
 
 Any of the many forms of batteries previously described may 
 be used for electrotyping, but the best is Srnee's. Care should 
 be taken to observe the directions heretofore given for the treat- 
 
MOULDS. 567 
 
 ment and management of batteries ; their good condition, proper 
 arrangement and management, being necessary to success. 
 
 The intensity and quantity of the galvanic current should be 
 proportional to the work to be done. 
 
 Preparation of Articles to be Plated or Copied. In gilding 
 and silvering, it is merely necessary to have the objects perfectly 
 clean and bright. This is effected by first boiling the articles in 
 a solution of caustic soda or potassa, and afterwards immersing 
 them in dilute nitric acid, and rinsing with water. They are 
 further cleaned by rubbing with a hard brush, and sometimes a 
 little fine sand or tripoli. 
 
 Moulds. Many substances are used for making moulds; 
 among the best are beeswax, plaster of Paris, fusible metal, and 
 gutta percha. 
 
 Wax moulds are prepared by melting the wax over a water- 
 bath, and stirring in one ounce of white lead to each pound of 
 wax. The wax should be clear and free from impurities. 
 
 If the object to be copied is a medal, it should be brushed over 
 with sweet oil, and the excess of oil removed with a cloth. A 
 slip of metal or card is bound round the edges of the medal, so 
 as to form a rim. The wax being melted, the medal, to prevent 
 air-bubbles, is held in an inclined position, and the wax, which 
 should not be too hot, poured gently on the lowest part, and 
 allowed gradually to spread over the surface of the medal by 
 bringing it to a level when it is filled to the top of the rim with 
 wax. As soon as the wax begins to set, the band should be re- 
 moved to prevent cracking. Let the medal and wax remain 
 together until entirely cold, so that they may be easily separated. 
 
 If it is desired to take a wax mould from a plaster-cast or 
 medallion, a similar course is followed, the medallion being first 
 prepared as follows: the medallion is warmed a little, brushed 
 over with boiled linseed oil, and allowed to dry perfectly. It 
 then presents a polished appearance and is ready for the wax. 
 
 Instead of oil, water is often used ; the plaster being saturated 
 with it by placing the back of the medallion in the water, care 
 being taken not to allow the water to flow over the face of the 
 medallion. 
 
 Plaster of Paris moulds are made by mixing the finest calcined 
 plaster with water, to form a thin paste about the consistence of 
 
568 NON-CONDUCTING SUBSTANCES. 
 
 cream. A little of this paste is poured upon the object and well 
 brushed into every part with a camel's hair brush, and then more 
 of the paste is added to produce the requisite thickness. It is 
 allowed to set and dry ; the drying can be facilitated by heating 
 in an oven or otherwise. 
 
 The fusible metal of which moulds are frequently made is an 
 alloy of five parts of lead, three of tin, and eight of bismuth, and 
 melts below 212 F. 
 
 Care and practice are requisite for producing a good and sharp 
 casting ; and the metal must not be poured too hot. Commence 
 by pouring sufficient of the melted alloy into a suitable vessel, 
 taking the precaution to skim the dross from the surface of it 
 with a card, and when it is nearly congealed, bring the matrix 
 down upon it quickly and with considerable force, and let it 
 remain until the mass has perfectly cooled. When done with 
 skill, a reverse will be obtained with all the sharpness and per- 
 fection of the original. 
 
 . Gutta percha is probably the substance best adapted for taking 
 moulds for electrotyping. It is applicable to metal, wood, glass, 
 stone, &c. It needs only to be softened by heat either in warm 
 water or by a steam-bath, spread into suitable form, laid and 
 pressed upon the object to be copied, and allowed to cool under 
 the pressure, when the mould will be fit for use. 
 
 Sulphur is sometimes used for moulds ; and very beautiful im- 
 pressions can be made also with sealing-wax, which takes the 
 minutest lines of the original. Reverses may be procured in lead 
 by forcing the matrix into a bright surface of it, either by pres- 
 sure or blows. 
 
 Non-conducting Substances. As gutta percha, wax, plaster 
 of Paris, and many of the materials used for making moulds are 
 non-conductors, it is necessary to coat the surface on which it is 
 desired to deposit metal with some conducting substance. The 
 best and easiest of application is plumbago or black lead. A 
 copper band or wire is fastened around the edge of the mould, 
 and the ends formed into a hook, or punched with holes, to make 
 the connection with the battery. A fine brush is dipped into the 
 plumbago and passed thoroughly over the face of the mould, all 
 excess of black lead being carefully removed, and the brushing 
 continued until every part is covered and brightly polished. This 
 
SOLUTIONS. 569 
 
 treatment will insure a quick and even deposit. In wax moulds 
 it is only necessary to insert, in the edge of the mould, a piece 
 of copper by which to attach it to the battery-pole. In every 
 case, however, the conducting coating must extend to and be in 
 contact with the battery connection. In using metal moulds, 
 those parts on which metal is not to be deposited should be covered 
 with wax or some kind of varnish. 
 
 The battery connection is most conveniently and perfectly 
 formed by soldering a copper wire, flattened, at one end to the 
 metal mould. 
 
 Bronze powder is sometimes used instead of plumbago and in 
 the same manner. Flowers, and other objects to which plumbago 
 is not applicable, may be rendered conducting by a film of gold 
 or silver. This is applied through the medium of a solution of 
 phosphorus in bi-sulphuret of carbon. The solution is made by 
 dissolving 1 ounce of phosphorus in 15 ounces of bi-sulphuret of 
 carbon, and adding thereto 1 ounce of wax, 1 ounce of asphalte, 
 1 ounce of spirits of turpentine, and 1 drachm of india-rubber. 
 The india-rubber must be dissolved in turpentine, and the as- 
 phalte in the phosphorus solution. The wax is melted first, the 
 turpentine and india-rubber stirred in, and then the asphalte and 
 phosphorus solution added. 
 
 This should be done with caution over a water-bath, as the 
 components are highly inflammable. The bi-sulphuret of carbon 
 being very volatile, the solution should be kept in a well-stoppered 
 bottle. " The solution, as above prepared, is applied to the sur- 
 faces of non-metallic substances by immersion or brushing ; the 
 article is then dipped in a dilute solution of nitrate of silver or chlo- 
 ride of gold ; in a few minutes the surface is covered with a fine film 
 of metal, sufficient to insure a deposit of any required thickness 
 on the article's being connected with a battery. The solution in- 
 tended to be used is prepared by dissolving 1 ounce of silver in 
 nitric acid, and afterwards diluting with 3 gallons of water ; the 
 gold solution is made by dissolving 2 pennyweights of gold in 
 aqua regia, and then diluting with a gallon of water." 
 
 G-old Solution. Convert a half ounce of gold into terchloride, 
 dissolve the gold salt in a little water, and add it to a solution of 
 four ounces of cyanide of potassium in two quarts of water and 
 filter. 
 
570 SOLUTIONS. 
 
 Silver Solution. Take of cyanide of silver 1 ounce, cyanide 
 of potassium 10 ounces, water 6 pints ; dissolve the cyanide of 
 potassium in the water, add the cyanide of silver, and filter the 
 solution. 
 
 Probably a better way to make the solutions of gold and silver 
 in cyanide of potassium is with the battery. Immerse, in a solu- 
 tion of 1 part cyanide of potassium to 16 parts of water, a silver 
 plate, connected with the positive pole of a battery, complete the 
 connection with the negative pole, and keep up the action of the 
 battery until silver is freely deposited on the negative pole. The 
 same process is followed for gold, care being taken to substitute 
 a gold for the silver plate. 
 
 Sulphate of Copper is the best salt for the reduction of copper. 
 A nearly saturated solution, acidulated with a few drops of sul- 
 phuric acid, is used. One pound of the sulphate in six pounds of 
 water is a good strength. 
 
 Cyanide of Copper is sometimes used for depositing copper or 
 iron. It is made by dissolving the oxide in an excess of cyanide 
 potassium, or by making a sheet of copper the positive pole in a 
 solution of cyanide of potassium. 
 
 Platinum, zinc, and most of the metals can be reduced from 
 their salts by the battery ; but for electrotyping they are seldom 
 or never used. 
 
 To have the metals adhere well in gilding and silvering, the 
 articles to be plated must be well cleansed. As silver is gene- 
 rally precipitated on copper, the article is boiled in caustic potash 
 or soda well rinsed with water, dipped in dilute nitric acid, after- 
 wards immersed in a weak solution of nitrate of mercury, and 
 immediately placed in the silvering solution. Gold is usually 
 deposited on silver. The silver object is treated as before with 
 caustic lye, rinsed, and, when dry, is thoroughly scratched with 
 a scratch-brush, which is a bunch of fine wires made into a brush. 
 It is then ready for the battery. In gilding, the solution should 
 be maintained at about 150 F. by a water-bath. 
 
 To avoid opposite currents of electricity in the depositing solu- 
 tion from an exhaustion of the solution around the negative pole, 
 and a dense solution forming around the positive pole, the articles 
 should be kept in motion during the deposition; for this motion 
 also prevents that crystalline deposit deemed so objectionable. 
 
BRONZING. 
 
 571 
 
 To prevent the adhesion of the matrix to the deposited metal, 
 Mr. Mathiot, of the United States Coast Survey, recommends 
 that the engraved copper plates, &c., be coated in a battery with 
 a thin film of silver, and afterwards washed with a dilute solution 
 of iodine in alcohol, about one grain of the former in a quart of 
 the latter. 
 
 Dusting with black lead, or spreading a little oil over the sur- 
 face of the article, care being taken not to use an excess, will 
 cause the metals to separate easily. A little wax dissolved in 
 spirits of turpentine also answers well. 
 
 Solutions should be kept covered from the air and dust; and 
 the working of the batteries is promoted by having the surrounding 
 atmosphere of a warm temperature. 
 
 A few drops of bi-sulphuret of carbon added to a silver solu- 
 tion will produce a bright deposit. 
 
 In inserting the articles in the solutions the air adhering to 
 their surfaces, and which prevents a contact of the metals, may be 
 dispelled by moving the articles about in the liquid or by heating 
 the solution. 
 
 Fig. 475. 
 
 The plates attached to the positive poles should be parallel to 
 the articles on which the metal is to be deposited and present the 
 same amount of surface. 
 
 A battery, if in proper working order, will, when the connec- 
 
572 BLOWPIPE MANIPULATIONS. 
 
 tions are made, show a disengagement of gas at its negative 
 metal ; but no gas should be seen to escape at either pole. 
 
 Bronzing. To give the copies of medals and other objects an 
 antique or bronzed appearance like the original, several means 
 are employed. A dark bronze is produced by dipping the object 
 in very dilute nitric acid, say half an ounce of acid to a pint 
 of water, and, after drying, heating it gradually and uniformly. 
 The color is deepened in proportion to the heat applied. Sul- 
 phuretted hydrogen or hydrosulphuret of ammonia may also be 
 used. Afterwards polish with a brush. Green bronzes are 
 formed by immersing the articles in a solution of chloride of 
 ammonium or chloride of sodium, or by exposing them to the 
 fumes of chloride of lime. The depth of the bronze is regulated 
 by the length of time during which the articles are subjected to 
 the galvanic action. A coating of black lead and subsequent 
 heating of the article, gives a beautiful bronze. A thin film of 
 oil or wax, and heating until the grease commences to decompose, 
 produces a good bronze. Immersion in a solution of chloride of 
 platinum also gives a handsome bronze. 
 
 CHAPTER XXIX. 
 
 BLOWPIPE MANIPULATIONS. 
 
 THE blowpipe is a small and convenient instrument by which a 
 blast of air may be forced through a candle, or oil or gas flame, so 
 as to intensify the heat of the latter to such an extent as to render 
 it a substitute for the furnace in very minute and delicate ope- 
 rations. 
 
 Its use had long been known in the arts, but its first applica- 
 tion to chemistry was made, in 1738, by Anthony von Schwab, a 
 Swedish Counsellor of the College of Mines. He employed it in 
 testing ores and minerals, but not having left any account of his 
 experiments, we are ignorant how far they extended. 
 
 In the hands of Cronstedt, a Swedish Master of Mines, it be- 
 came a ready means of distinguishing and arranging minerals 
 according to their characteristic behavior with fusible reagents. 
 
 Von Engestrom published, in 1770, an English translation of 
 
BLOWPIPE MANIPULATIONS. 573 
 
 Cronstedt's system of mineralogy, with an account of the methods 
 employed by him in testing minerals; hut yet the instrument 
 found no general favor, and for a long time afterwards had no 
 more extended application than to the testing of the fusibility of 
 substances, and their solubility in borax-glass. 
 
 Bergmann enlarged the sphere of usefulness of the blowpipe, 
 and employed it in analytical investigations, to detect the pre- 
 sence of minute quantities of certain mineral substances. His 
 work on the use of the blowpipe appeared in 1779. Bergmann's 
 feeble health caused him to seek the assistance of Gahn in his 
 experiments, who became, under his instruction, so expert in the 
 use of the blowpipe that he was able to detect with it substances 
 which had escaped the most careful analysis in the moist way. 
 But Gahn could never be prevailed to give to the world the re- 
 sults of his experience. Fortunately for science, his pupil, Ber- 
 zelius, recognized the value of this instrument, and after testing 
 with it the reactions of most of the minerals and mineral sub- 
 stances then known, published his valuable work on "The use of 
 the Blowpipe in Chemistry and Mineralogy." 
 
 After the publication of this work, in 1821, the use of the blow- 
 pipe become general among chemists and mineralogists. Harkort 
 first attempted to make quantitative assays with its assistance; 
 but it is to Plattner, Professor of Metallurgy in the Saxon Royal 
 School of Mines, that the method of performing quantitative de- 
 terminations by the blowpipe owes its great exactness and sim- 
 plicity. His admirable work " On the Art of Assaying with the 
 Blowpipe," furnishes the most accurate and complete information 
 on this branch of science, and will be a lasting monument to his 
 patient industry and genius. 
 
 A simple form of the blowpipe, and that originally adopted for 
 soldering, &c., by metal-workers, is repre- 
 
 fjo^ 476. 
 
 sented in Fig. 476. It consists of a taper- ^ n 
 
 ing tube of brass, curved nearly at a right (F 
 angle, a short distance from the smaller 
 end. The bore terminates in a very small perforation. A steady 
 stream of air is forced through it by the action of the muscles of 
 the cheeks, and directed against the flame of a candle or lamp. 
 This form of the blowpipe has the disadvantage of promoting, by 
 long-continued blowing, the condensation of the moisture of the 
 
574 
 
 BLOWPIPE MANIPULATIONS. 
 
 breath in the tube. This obstructs the passage of air, or, being 
 driven out into the flame, very seriously interferes with the suc- 
 cess of the operation. It, therefore, becomes necessary to con- 
 struct the blowpipe with a chamber in which the condensed 
 moisture may lodge. 
 
 The instrument which best fulfils all the requirements for 
 general use is that devised by Gahn, and recommended by Ber- 
 zelius. 
 
 It consists of a slightly tapering tube (Fig. 477), fitting into a 
 
 Fig. 477. 
 
 cylindrical chamber, an inch long, and half an inch in diameter. 
 Into the side of this chamber, a much shorter and smaller tube is 
 inserted at a right angle. The end of this tube is covered with a 
 tip of platinum, Fig. 478, with a fine aperture. Plattner 
 ^ recommends two such tips, with perforations of different 
 Oj dimensions. The finest, which is used in qualitative tests, 
 has an aperture O4 millimetre in diameter. The other, 
 for such tests as require a stronger heat, has a slightly larger 
 aperture. Tips of platinum are preferable to those made of any 
 other metal, on account of the facility with which they may be 
 freed from soot by heating them on charcoal. If tips of brass or 
 silver are employed, the aperture may be cleaned with a fine 
 splinter of horn. The length of the blow- 
 pipe must be adjusted to the sight of the 
 operator, so that the test object may be 
 held at such a distance as to be distinctly 
 visible. The blowpipe should be provided 
 with a mouth-piece of ivory or horn a b, 
 Fig. 479. The form of the mouth-piece 
 recommended by Plattner is trumpet- 
 shaped, and it is to be pressed against the 
 lips instead of being held between them. 
 The outer edge must have a sufficient spread to present a flat 
 
 Fig. 479. 
 
 
BLOWPIPE MANIPULATIONS. 
 
 575 
 
 Fig. 480. 
 
 surface to the lips, so that any undue pressure may be avoided. 
 The diameter of this mouth-piece should not exceed one and one- 
 fourth to one and one-half inches. 
 
 The use of this mouth-piece very much diminishes the fatigue 
 of the muscles of the lip in long-continued blowing, and the diffi- 
 culty at first felt in preventing the escape of air at the corners of 
 the mouth is easily overcome by practice. The drawing exhibits 
 it in full size. 
 
 Mitscherlich has so modified the form of Gahn's blowpipe as to 
 render it very portable. The moisture- 
 chamber is diminished in length, and per- 
 manently attached to the long tube, as 
 shown in the drawing, Fig. 480. This 
 tube is made to unscrew in the middle, 
 so that the small tube c, with its plati- 
 num jet D, can be slid into the part con- 
 nected with the chamber, and the other 
 half A passed over it as a cover. The 
 whole forms a short, smooth cylinder, which 
 may conveniently be carried in the pocket. 
 The mouth-piece should be silvered ; or a 
 separate mouth-piece of ivory may be made 
 to screw into it. 
 
 For the purpose of relieving the cheek muscles at intervals, 
 without interruption to the blast, the blowpipe may be constructed 
 according to De Luca's suggestions, and as exhibited in the an- 
 nexed drawing, Fig. 481. Between the mouth-piece and the 
 
 Fig. 481. 
 
 chamber for collecting the moisture, an india-rubber bulb or bag 
 is adjusted by ivory collars upon the tubes D and H, the project- 
 ing ends of which are connected by means of, a light metal rod. 
 The escape of air, when the mouth may be removed, is prevented 
 by a valve at A opening outwards. 
 
576 THE COMBUSTIBLE. 
 
 The proper material for the construction of blowpipes is real 
 or German silver. When made of the latter, it will be advisable 
 to galvano-plate them, otherwise the base metal, by constant 
 handling, will impart an unpleasant odor, and dirty the skin. 
 The great conducting power of both of these materials is apt to 
 cause the instrument to become overheated by a long-continued 
 blowing. Brass blowpipes are very objectionable, as they oxidize 
 readily at the jet, and moreover give a metallic taste and odor. 
 In emergencies, a very convenient blowpipe may be made from 
 a common tobacco-pipe, by accurately 
 Flg>482 - closing the bowl with a tight cork, and 
 
 fitting in the latter a glass jet. This 
 latter is formed by drawing out a 
 small tube to a fine point, and smooth- 
 ing the end in the flame until it be- 
 comes thick, but, at the same time, presents a perfectly round 
 and small aperture. 
 
 The Combustible. Almost any flame which is strong enough 
 to afford the requisite heat may be used with the blowpipe. In labo- 
 ratories where coal-gas is burned, its use will be found very con- 
 venient. The form of burner which we have found to answer 
 best is that known as Solliday's patent, a single slit burner, with 
 a small cylinder fitting closely around it, and reaching a short 
 distance above the base of the flame. This cylinder, or jacket, 
 has two shallow incisions lying in the axis of the flame, in one of 
 which the jet of the blowpipe may be made to rest. For very 
 small operations the flame of a candle may be employed ; but for 
 many reactions it does not yield sufficient heat, and in quantita- 
 tive assays its use is quite inadmissible. The best fuel for this 
 purpose is olive, or refined rape oil. Care must be taken to select 
 oil which burns without much smoke, and with a colorless flame, 
 as the color of the flame is frequently a characteristic reaction. 
 
 Harkort's modification of Berzelius's lamp is the most conve- 
 nient and best adapted for blowpipe experiments. It consists of a 
 sheet brass, horizontal cylinder, four and a half inches long, and 
 slightly tapering to one inch width at the end nearest the ope- 
 rator, as shown in Fig. 483. 
 
 It is made to slide upon an upright brass rod, and can be ad- 
 justed to any height by a screw. At one end of the lamp is an 
 
HARKORT'S LAMP. 
 
 577 
 
 opening for introducing oil, and at the other is the wick-holder. 
 Both of these openings are closed by screw-caps, with the thread 
 
 Fig. 483. 
 
 cut on the inside. The escape of oil is prevented by washers 
 cemented to the caps with shell-lac and wax. The wick-holder 
 has its greatest breadth at right angles to the axis of the lamp, 
 and must be cut off obliquely, to allow the flame to be directed 
 downwards. Cylindrical woven wicks, such as are made for Ar- 
 gand burners, are best adapted for this lamp, and they are pressed 
 flat and folded lengthwise, so as to be introduced fourfold. Care 
 must be taken that the wick does not fit too tightly, else its capil- 
 larity will be impaired, and the ascent of the oil obstructed. 
 
 Moreover, the wicks must be entirely free from any lime that, 
 may have been used in the bleaching of them, as that earth, 
 
 3T 
 
578 THE FLAME. 
 
 " rf 
 
 in giving a reddish-yellow flame itself, may obscure the flame re- 
 action of the substance under process. 
 
 The r6d in which the lamp slides also carries a triangle, which 
 is very convenient for supporting small capsules, crucibles, &c., 
 over the flame. To render the apparatus compact and portable, 
 it is constructed in parts, with screw connections. Fig. 485 shows 
 the several pieces in their proper positions. 
 
 In addition to the above, a small spirit-lamp is often needed 
 for applying a flame directly to tubes, crucibles, &c., Fig. 484. 
 
 The blowpipe is held in the right hand, as shown in Plate 3, 
 and in such a manner as to facilitate a direction of the flame 
 upon the substance under process. This latter, as 
 
 Fig. 485. w jjj k e geen j n t ^ e same (J raw i n g ) i s ne l(j upon a 
 
 support by the left hand ; care being taken to retain 
 the arms in their fixed position, for unsteadiness 
 will prevent an uninterrupted action of the blast in 
 the assay. 
 
 The mouth furnishes the blast, which derives its 
 force from the muscles of the cheek. To prevent 
 fatigue of the respiratory organs, communication 
 between the mouth and chest must be closed during 
 the blowing, and breathing maintained through the 
 nostrils. A few days' practice removes all the difficulty at first 
 experienced in producing a continuous, steady current ; and it is 
 by this means only that proficiency can be acquired. The ope- 
 ration is commenced by filling the mouth with air, expanding the 
 cheeks, and then keeping up a steady forcible pressure with the 
 muscles, respiration being allowed to go on as usual through the 
 nose. 
 
 The Flame. The flame which furnishes the heat for blowpipe 
 operations consists of several parts, of each of which it is neces- 
 sary to have a knowledge in order to be able to manage it skil- 
 fully. Flame may be considered as a miniature furnace, pro- 
 ducing an intense heat with the aid of a blowpipe. It consists of 
 four distinct parts, as will be explained by the drawing, Fig. 486, 
 which represents an oil or tallow flame. The base a b is a dis- 
 tinct blue conical envelope surrounding the burning wick, and 
 which gradually diminishes as it rises, and eventually disappears 
 when it reaches the point where the flame elongates perpendicu- 
 
I 
 
 
 *.T 
 
 "w,. , 
 
 
 
 
 

 ; *-.: if W 
 
 ?*- . . :/< 
 
 
THE FLAME. 
 
 579 
 
 Fig. 486. 
 
 larly. The central portion is the dark cone <?, sur- 
 rounded by the brilliant, luminous envelope d, which 
 is the sphere of illumination. Exterior to this, and 
 enveloping the whole is the faintly luminous cur- 
 tain a e I, forming the hottest portion of the flame, 
 and presenting its greatest intensity at the point/. 
 From this point the heat gradually diminishes, both 
 upwards and downwards. 
 
 The structure of the flame is explicable as follows. 
 The wick being an assemblage of threads, exercises, 
 when lighted, the power of capillarity, arid continu- 
 ously draws up the fluid fat to the accendible point, 
 where the elements of the latter, carbon, oxygen, and hydrogen, 
 are resolved by combustion into inflammable gases, which burn and 
 produce flame. The external part a e b is the hottest, owing to its 
 direct contact with the air, which supplies oxygen to complete the 
 burning of those products which rise from the wick through the 
 flame as faintly luminous matter, and in a state of partial combus- 
 tion. As before said, this portion gives its maximum of heat at the 
 level of//. The coolest part of the flame, on the other hand, is at 
 a 6, and its blue color is due to the combustion of carbonic oxide 
 and a small portion of carburetted hydrogen. The shaded cone 
 in the centre is the sphere of unburned combustible, owing to the 
 difficult access of the air to it ; and surrounding it is the brilliant 
 
 Fig. 487. 
 
 portion, less favored with oxygen from the air than the exterior 
 sphere of complete combustion on which it impinges. 
 
580 OXIDATION. 
 
 When a current of air is directed through a blowpipe with a 
 small, straight aperture against a flame, it drives the latter be- 
 fore it in a long, pointed, and conical projection. To produce a 
 clean and uniform flame, the tip end of the blowpipe should 
 barely penetrate the flame, Fig. 487, and when it is desired to 
 give it volume, it must be slightly parted in the middle by draw- 
 ing the tip of the blowpipe across it. In this latter case, too, the 
 blowpipe should be directed at an angle of forty-five degrees 
 across this channel. In blowing, the breath must be so regu- 
 lated that the blast should be neither too strong nor too feeble ; 
 for, in the first instance, the excessive air cools the flame, and in 
 the latter, the combustion is slow and imperfect. 
 
 " The long, narrow blue flame a 6, which appears directly be- 
 fore the jet, is the same as a 5, Fig. 486, although changed in 
 form, being now concentrated into a small cylindrical space, 
 whereas before it formed an envelope around the whole flame. 
 Just before the point of this blue flame is the greatest heat, just 
 as in a free flame, but with this difference, that, in the latter case, 
 it formed a ring around the flame, while, in the former, it is con- 
 centrated into a focus. It is thus rendered sufficiently intense 
 to fuse and volatilize substances which were not sensibly acted on 
 by the flame in its usual state. On this is founded the whole 
 theory of the intense heat produced by the blowpipe ; the effect 
 which would otherwise be distributed over the whole surface of 
 the flame is concentrated into a small space, exactly as if the 
 flame had been turned inside out. The surrounding illuminating 
 portion of the flame prevents the heat from escaping. 
 
 " Long practice is required to know where the maximum of 
 heat is, since different substances are differently ignited, and the 
 light which they emit is often deceptive. A very intense heat 
 is required when the fusibility of a substance is to be investigated, 
 or when different metallic oxides, which are obstinate in parting 
 with their oxygen, like the oxides of tin or iron, are to be reduced. 
 But it is not a high temperature only which it is the design of 
 the blowpipe to produce ; there are other operations which require 
 a less intense heat, and which, though diametrically opposed to 
 each other, can be effected by the blowpipe. These are oxidation 
 and reduction." 
 
 Oxidation. "This takes place when the assay is heated, just 
 
REDUCTION. 581 
 
 before the extreme point of the flame, when all the combustible 
 particles are completely oxidized. The farther from the apex 
 of the blue flame, the better the operation goes on, provided the 
 heat be sufficiently intense ; and it must be observed that a too 
 high temperature often impedes the oxidation, especially if the 
 assay be supported upon charcoal. Oxidation goes on best at a 
 low red heat ; and to this end the blowpipe jet must have a large 
 aperture." 
 
 Reduction. " This process succeeds best with a fine jet, which 
 should not be inserted too far in the flame, since, in this case, a 
 highly illuminating flame is produced, the elements of which, not 
 undergoing complete combustion, do not take oxygen from the 
 assay, which may be considered as being heated in an inflam- 
 mable gas. If, in the course of the operation, the assay becomes 
 coated with soot, it is a proof that the flame is too smoky, and, 
 consequently, its heat is diminished. The blue flame was formerly 
 regarded as the proper reducing flame ; this is, however, untrue, 
 for it is the brilliant portion of the flame which causes deoxida- 
 tion ; but the assay must be held in it in such a manner as to be 
 surrounded by it on all sides and protected from contact with the 
 air. It is to be remembered, that reduction is accomplished, not 
 by the charcoal, but by the combustible atmosphere which sur- 
 rounds the assay. The reduction which takes place at the points 
 of contact of the assay and the charcoal would happen equally 
 as well in the outer as in the inner flame. 
 
 " The most important matter is to be able to produce, option- 
 ally, oxidation or reduction ; and this is soon acquired by prac- 
 tice. Oxidation is so easily performed that it is only necessary 
 to be told how to do it. Reduction requires more experience, and 
 a better knowledge of the management of the flame. It is an 
 excellent exercise to fuse a small grain of tin upon charcoal, and 
 raise it to a white heat, while keeping its surface brilliant. Tin 
 has an attraction for oxygen so strong, that the moment the flame 
 is changed in the least the metal becomes covered with an in- 
 fusible crust of oxide of tin. The larger the globule of tin that 
 the operator is able to keep fused in the metallic state, the more 
 proficient is he in the management of the blowpipe and the 
 flame." 
 
 The wick of the lamp must be cut evenly and free from fibres, 
 
582 SUPPORTS. 
 
 and the blast must be uninterrupted, more particularly in the 
 reducing process. 
 
 Supports. The substance under examination must be allowed 
 to rest firmly upon a support, which should be such as will not 
 fuse under a high heat, combine chemically with the fused body, 
 or prevent its complete heating by rapid conduction. The sup- 
 ports in most common use are charcoal, and platinum either in 
 the form of wire or foil. 
 
 Charcoal makes, for many operations, an excellent support, 
 especially that kind of it which is made from well-grown pine 
 wood, or the branches of the willow. It must be well charred, 
 and that which snaps or smokes in the fire should be rejected. It 
 is desirable that it shall be as free as possible from ashes, which 
 nearly always contain a trace of iron and manganese ; therefore 
 dense and compact woods should not be used, as they give much 
 ashes, and often contain a considerable amount of these oxides, 
 which, by uniting with the fluxes employed, would give incorrect 
 results. Straight pieces, free from knots, are to be sawed in the 
 direction of the fibres, into oblong supports of the proper size. 
 The saw for cutting the charcoal should have fine teeth and a 
 blade of five inches length, three-eighths of an inch breadth, and 
 one-sixteenth of an inch thickness. The assay is placed in a 
 shallow concavity, made near one end of such a support by the 
 borer or point of a knife ; and upon this substance, so prepared, 
 oxidation, reduction, and fusion are chiefly performed. 
 
 Sometimes the reducing property of charcoal, and the rapidity 
 with which it is dissipated into carbonic acid, interfere with the 
 result. In such cases, platinum in the form of foil or wire is used. 
 A narrow strip, 3 inches long and J inch broad, is often advan- 
 tageously employed for oxidation. The substance which is to be 
 oxidized, is placed on it near one end, and heat is applied by the 
 blowpipe flame upon its under side. Its conducting power is so 
 inconsiderable, that the other end may be held between the fin- 
 gers without inconvenience. Platinum cannot in general be used 
 for reduction, as it forms fusible alloys with some of the metals ; 
 nor should sulphurets, arseniurets, &c., be heated in contact with 
 it. When the strip is too short to be held between the fingers, it 
 can be inserted in a piece of wood or charcoal, or be held between 
 the points of a pincette. A small spoon of the same metal is 
 
SUPPORTS. 583 
 
 sometimes made use of; but in the majority of cases, the wire 
 may be substituted for any other means. 
 
 When platinum wire is used, it should be about 2 J inches long, 
 moderately thin, and bent into a hook at one end, which 
 serves as the support for the assay. This part is either Fig. 488. 
 heated for a moment in the flame, or moistened and dip- 
 ped into the flux, whereby a small quantity becomes 
 attached, which, when fused to a transparent bead by the 
 blowpipe flame, becomes firmly fixed in its bed, and oc- 
 cupies the space within the curve. The side of the bead 
 is then moistened, and a little of the assay is made to 
 adhere to it. 
 
 Both are now fused together, and the appearance of the bead 
 held in one or the other part of the flame, in reference to opacity, 
 color, and other characteristics, can be distinctly seen from all 
 sides, and in this way are colorations of the bead by metallic 
 oxides particularly to be distinguished. The only objection to 
 this hooked wire, occurs in the case of the use of fusible flux, 
 which is apt to fall through it. Two or three additional turns of 
 the hook will generally make a bed sufficiently close to prevent 
 this salt from running through when fused. 
 
 The bead can be detached from the wire, when cold, by a slight 
 blow with the hammer. If, after its removal, the wire is not left 
 perfectly clean, a bead of soda may be fused upon it, and after- 
 wards dissolved out, when it takes the impurities with it. In 
 extensive investigations, by means of the blowpipe, a number of 
 these wires should be provided. 
 
 Fig. 489. 
 
 The wire may be held in the hand, either with or without a hilt ; 
 but it is more convenient to use the latter. It is nothing more 
 than a turned piece of wood, Fig. 489, with a metallic socket on 
 the end for receiving the wire, which is then fastened in by the 
 screw B. 
 
584 
 
 DETECTION OF VOLATILE SUBSTANCES. 
 
 Fig. 490. 
 
 A support for cupels and small crucibles is shown by Fig. 
 
 490. It is a piece of turned wood, 3J inches long, with a brass 
 wire, fashioned, as is seen, for receiving the 
 cupel and holding it firmly during the action 
 of the blowpipe. The handle allows the 
 operator to change its position before the 
 flame, merely by turning, raising, or lowering 
 it, as may be necessary. 
 
 A small platinum spoon, from 3- to f inches 
 diameter, and of form shown by Fig. 491, will 
 be required, as the containing vessel, in flux- 
 ing ores. It is made with a projecting strip 
 from the bowl, by which it is adjusted in the 
 handle, Fig. 489, on preceding page. 
 
 A well-polished ivory or platinum spoon, 
 Fig. 492, about three inches long and three-six- 
 teenths of an inch in breadth, will be necessary 
 in weighing the powdered ore, and mixing it 
 with the flux. The handle should, for greater 
 convenience, be made in the form of a spatula. 
 Detection of Volatile Substances by means of the Blowpipe. 
 
 When volatile substances or gaseous products are to be tested 
 
 Fig. 491. 
 
 by means of this instrument, the body to be examined is usually 
 exposed to heat in an open glass tube, which may be from two to 
 
 Fig. .492. 
 
 four inches in length, and from the twelfth to the third of an inch 
 in diameter. The body is placed near to one end, and the blast 
 
INSTRUMENTS USED IN BLOWPIPE ANALYSIS. 
 
 585 
 
 is directed upon it, while the tube (Fig. 493) is inclined more or 
 less in proportion to the current of air, which is required to be 
 passed through it. By such means, disengaged vapors may be 
 sometimes recognized as they emerge from the upper end, and 
 volatile matters condensed upon a part of the tube. 
 
 It is often necessary to deposit the substance in the angle of a 
 curved tube, so as to prevent it from falling out. A tube so bent 
 is shown at 5, Fig. 494. Another modification is required where 
 
 Fig. 493. 
 
 Fig. 494. 
 
 the access of much or any air would counteract the intention of 
 the operator, by oxidizing the body. In such cases, the lower 
 end of the tube is either completely closed, or drawn out to a 
 fine orifice as at c in the same figure. A tube of this form is 
 well adapted to the sublimation of selenium from a sulphuret, 
 where the entrance of much air would oxidize it. Decrepitating 
 substances should also be heated in tubes closed at one end, and 
 should be so inclined as to avoid loss of particles. For such and 
 many other purposes, tubes, Fig. 484, enlarged into a bulb at one 
 extremity, are very appropriate. 
 
 All the glass tubes and vessels employed in this way should be 
 perfectly free from lead. 
 
 The following instruments are also used in making examina- 
 tions with the blowpipe ; steel forceps with the points made of 
 platinum, for holding the assay in the blowpipe flame to ascertain 
 its fusibility or other properties when exposed to an elevated tem- 
 perature. The two upper drawings of Fig. 495 represent different 
 views of an excellent forceps, capable of very general applica- 
 tion. Two strips of steel, with narrow platinum points, &, >, are 
 fastened in the middle by a piece of metal seen at ej e. These 
 strips separated, as seen in the figure, constitute a double pair, 
 one being at a, a, and the other at c. The platinum points, by 
 
586 INSTRUMENTS USED IN BLOWPIPE ANALYSIS. 
 
 the elasticity of the metal of which the forceps are made, are 
 always closed. To open them it is only necessary to compress 
 with the thumb and finger the small projections with the button 
 heads d, d, which are connected with the strips opposite to them. 
 Upon relaxing the pressure, the assay is forcibly held between the 
 points. The points a a are tempered, and are used for detach- 
 ing exceedingly small fragments of the mineral. 
 
 Fig. 495. 
 
 Another form of this instrument is employed, but its use is not 
 quite as convenient as that of the one just mentioned. Its points 
 b c are also of platinum, but curved a little, as represented in the 
 figure. The legs are made of brass. The forceps is kept open 
 by the elasticity of the metal, and closed by a double button d, 
 which slides up and down in a slit cut in the legs. As brass is a 
 good conductor of heat, two pieces of wood e e are fixed to the 
 legs, by which the instrument is held, to prevent any inconvenience 
 to the hand. Under this last forceps, is still another, made of 
 iron, which can be used for a variety of operations, and which is 
 not solely confined to this application. Substances to be held 
 very firmly are placed between the points. It has a button d d, 
 with a steel spring d e, to prevent the forceps from opening by 
 the sliding back of the button. 
 
 Microscope. A plano-convex microscope, with two lenses of 
 different magnifying powers, is often useful in minute analysis, 
 and one is represented in Fig. 496, which is made to fit in a small 
 
INSTRUMENTS USED IN BLOWPIPE ANALYSIS. 
 
 587 
 
 receptacle. By its aid, the minute structure of bodies, and fine 
 colors imparted to the fluxes or to charcoal, which often deceive 
 the naked eye, are examined. 
 
 Fig. 496. 
 
 Charcoal Borer. A conical tube of tinned iron, with the 
 margin filed to -a sharp edge, for making cavities in the charcoal 
 support, is often made to occupy a place in blowpipe apparatus. 
 It answers very well as a case to contain a vial, as shown in the 
 figure above. Another form of charcoal borer is presented in the 
 annexed drawing, Fig. 497. " It is a four-sided pyramid of hard- 
 Fig. 497. 
 
 ened steel, with its sides filed away, so as to give it the form of 
 a double chisel crossing at right angles." It is used for boring a 
 round hole in the charcoal, by pressing it against the latter and 
 turning it upon its axis until the cavity is sufficiently deep. 
 A pair of cutting pliers are used to clip off small particles of 
 
 Fig. 498. 
 
 minerals and pieces of a metal or alloy for examination, and for 
 many other purposes which will suggest themselves to the expe- 
 
588 INSTRUMENTS USED IN BLOWPIPE ANALYSIS. 
 
 riinenter. A clasp is attached to the handles for the purpose of 
 keeping them forcibly closed. 
 
 Hammer and Anvil. A polished hammer of hardened 
 steel, Fig. 499, with a square, even surface at one end, and the 
 
 Fig. 499. 
 
 other terminating in an edge with sharp corners, is a very neces- 
 sary implement. The flat surface is very applicable for flattening 
 globules of reduced metals, and the edge for breaking off small 
 pieces of minerals. Very small fragments can be broken off 
 without doing any injury to the remaining portion, which is often 
 kept as a specimen. 
 
 A necessary accompaniment to the hammer is the anvil, which 
 
 is represented by Fig. 500, in a most 
 
 lg ' convenient and compact form. It is 
 
 made of steel, and is usually about 
 three inches long, one inch in thick- 
 ness, and five-eighths of an inch in 
 breadth, and any one of its surfaces 
 can be used. The substance to be 
 
 broken up, or the metallic globule to be flattened out, is enclosed 
 In thin paper, and having been placed upon the anvil, is struck 
 with the hammer until the proper effect is produced. If the sub- 
 stance is reduced to powder, the paper prevents any of it from 
 being scattered or lost. 
 
 Mortar and Pestle. These implements, made of agate, are 
 of small size, and have been described at page 92. They should 
 be hard and perfectly free from holes and cracks, or they will 
 be liable to fracture, and to the filling up of their crevices 
 with the powdered materials, much to the detriment of future 
 operations. 
 
 Electroscope and Magnetic Needle Case. A cylindrical 
 wooden box is used to contain Hatiy's electroscope and a mag- 
 netic needle. 
 
INSTRUMENTS USED IN BLOWPIPE ANALYSIS. 589 
 
 The former consists of the hair of a cat, insulated by being 
 inserted in sealing-wax poured into the bore of a small glass tube. 
 This tube is fastened in a wooden screw, which closes at one end 
 of the case. It is so delicate that a very small 
 quantity of electricity is discovered by its aid. 
 On bringing it near to an excited body, it is at- 
 tracted by it ; but if negative electricity is deve- 
 loped in it, by rubbing or drawing it rapidly 
 through the fingers, and it is then brought in 
 proximity to the excited body, it will be attracted 
 or repelled in accordance with the existence in that body of posi- 
 tive or negative electricity. In the screw at the other end (each 
 one serving as a stand), is fixed a similar tube and sealing-wax to 
 insulate a small steel pin, which supports a magnetic needle con- 
 tained in the box. The needle is mounted with an agate cup to 
 prevent friction as much as possible, when suspended on the point 
 of the pin. In this condition, it is used to indicate the presence 
 of iron when it exists in a mineral in an appreciable quantity, 
 and also the magnetic condition of iron ores. Minerals, before 
 and after being submitted to the action of the blowpipe, should 
 be examined in regard to these properties. 
 
 Steel Magnet. This is employed in the mode recommended 
 by Haiiy to ascertain whether the slightest trace of magnetic 
 force exists in minerals, and consequently whether the metals in 
 which that force exists are present. The experiment is thus per- 
 formed. The magnet is placed at a small distance from a sus- 
 pended magnetic needle, its north pole being directed towards 
 that of the needle ; it is then gently moved around the needle 
 until the latter takes a position at right angles to its former place, 
 owing to the repulsion of the same kind of magnetism. This re- 
 pulsion, and the force of terrestrial attraction, which tends to 
 make the needle return to its former direction, now hold the needle 
 exactly balanced between them, so that the smallest disturbing 
 magnetic force moves it out of its place. In this way, an amount 
 of magnetic influence may be detected, which would not be suffi- 
 cient to affect the needle in its ordinary state. In performing 
 this experiment, care must be taken not to excite electricity in 
 the mineral by friction, as that force might affect the result more 
 or less. 
 
590 INSTRUMENTS USED IN BLOWPIPE ANALYSIS. 
 
 A knife of good hardened steel is used for trying the compara- 
 tive hardness of metallic bodies and minerals generally. It may 
 be used as a charcoal borer, and if well magnetized can be sub- 
 stituted for the magnet. The point is used to take up the fluxes 
 before mixing them in the palm of the hand with the mineral 
 which has been pulverized for examination. 
 
 Files are convenient for detaching small particles of a metal 
 which is to be investigated, cutting glass tubes, and for trying 
 the hardness of bodies. They may be of different shapes, and 
 should be kept clean, and out of the reach of corrosive vapors. 
 
 An Edulcorator or spritz, Fig. 428. This is used to wash the 
 charcoal from the reduced metal. It is necessary to be very 
 cautious in doing this when the metal is small in quantity, as the 
 force of the jet may carry the latter away with the charcoal. A 
 pipette or dropping-tube, made by drawing out in the flame of a 
 candle or spirit-lamp one end of a glass tube to a small opening, 
 can be used with less danger. The separation will be facilitated, 
 by reducing to powder, in the agate mortar, for the charcoal 
 adhering to the piece of metal, as the globule, if malleable, will 
 be thus slightly flattened and made more distinctly visible. 
 
 Small capsules of porcelain, or watch glasses, are useful as 
 temporary receptacles for the results of the experiments ; such as 
 specimens of reduced metal, the colored beads, &c., and for 
 keeping separate different fragments of the minerals to be in- 
 vestigated. 
 
 A small pair of scissors, a pair of small tongs for holding cru- 
 cibles, &c., over the spirit-lamp, a small capsule of platinum, a 
 touchstone with needles of gold, and alloys of different standards 
 for trying the fineness of gold, will each be occasionally required. 
 
 Fig. 002. 
 
 Sox containing the Reagents. As it is necessary to have the 
 fluxes always ready for use, Gahn contrived a convenient and 
 
THE REAGENTS. 591 
 
 portable box for the purpose, which is seen in Fig. 502. It is 8J 
 inches long, Iy 3 g broad, 1 inch in height, and is divided into nine 
 compartments to receive the different reagents. Each division has 
 a lid nicely closing its particular box, so as to prevent any one 
 substance from becoming mixed with the others. A common lid 
 closes over these smaller ones, and is fastened to the box by two 
 hooks. The cross pieces, which are permanently fixed to the 
 large lid, fit into spaces between the second and third lids from 
 each end, and serve to make them more secure. 
 
 The Reagents. The reagents, which must all be chemically 
 pure, are the following : 
 
 Carbonate of Soda, commonly called soda, which is much used 
 to detect the presence of silica, to assist the reduction of metallic 
 oxides, arid generally, to determine whether a body unites with it 
 to the production of a fusible compound. 
 
 Cyanide of Potassium. This substance being very deliques- 
 cent, should be kept as free as possible from contact with humid 
 air, and had better be placed in a small, tightly corked test-tube, 
 which may have its place in one of the small compartments of 
 the box. 
 
 As a blowpipe reagent, cyanide of potassium is highly useful ; 
 its action is indeed extraordinary. Substances like peroxide of 
 tin, sulphuret of tin, &c. &c., which for their reduction with car- 
 bonate of soda, require rather a strong flame, are reduced with 
 the greatest facility when cyanide of potassium is used. In blow- 
 pipe experiments we always use a mixture of equal parts of car- 
 bonate of soda and of cyanide of potassium, since the latter alone 
 fuses too easily. This mixture, besides its more powerful action, 
 has another advantage over carbonate of soda : it is with extreme 
 facility imbibed by the porous charcoals, so that the purest 
 metallic globules are obtained. 
 
 Biborate of Soda. This salt, which is commonly called borax, 
 is used to facilitate the fusion of very many substances. When 
 melted with the metallic oxides, its bead assumes a great variety 
 of colors, which furnish excellent indications of the presence of 
 the metals. 
 
 Phosphate of Soda and Ammonia. This substance, called 
 also microcosmic salt, phosphorus salt, and fusible flux, is of very 
 general application, and as it dissolves most of the metallic 
 
592 THE REAGENTS. 
 
 oxides with great readiness, the colors produced in its bead are, 
 if possible, more brilliant and characteristic than those made 
 with borax. 
 
 Nitrate of Potassa, or saltpetre, is used to assist in the oxida- 
 tion of metals, as it yields up its oxygen very readily when 
 exposed to heat. 
 
 Bisulphate of Potassa in solution, is used to indicate lithia, 
 boracic acid, nitric acid, fluohydric acid, bromine, and iodine ; 
 and also for the separation of baryta and strontia from other 
 earths and metallic oxides. 
 
 Vitrified Boracic Acid (glass of borax), is used to detect the 
 presence of phosphoric acid ; also small portions of copper in 
 alloys of lead. 
 
 Fluoride of Calcium (fluor spar), when mixed with bisulphate 
 of potassa, serves to detect lithia and boracic acid. Alone, it is 
 a test for gypsum. 
 
 Sulphate of Lime, or gypsum, in the form of plaster of Paris, 
 is sometimes used as a reagent with fluoride of calcium. 
 
 Nitrate of Cobalt. This very valuable test is used in a some- 
 what concentrated solution. 
 
 Alumina heated in the oxidating flame, after being moistened 
 by a drop or two of this- solution, acquires a beautiful pale blue 
 color, magnesia a rose-red tint, and zinc a bright 
 Figj303, g reen . The solution is contained in a phial similar to 
 the one represented in Fig. 503. The glass stopple, 
 tapering to a point, descends into the solution, so that 
 on withdrawing it, a small quantity adheres to its ex- 
 tremity. Berzelius uses a cork stopple with a platinum 
 wire flattened out in the form of a spoon, the end of 
 which is immersed in the solution. The phial may be 
 of such a size as to be conveniently received in the charcoal 
 borer, Fig. 496. Oxalate of cobalt may be made to take its 
 place, and as it is used in powder, it is often of more convenient 
 application. 
 
 Nitrate of Nickel in solution, or Oxalate of Nickel in powder. 
 The oxide of nickel gives a brown color to soda glass, while pot- 
 ash, if melted with a substance containing it, acquires a bluish- 
 purple color. A bottle similar to the one just described may 
 contain the solution of the nitrate. 
 
THE REAGENTS. 593 
 
 Lead, very pure, and especially free from silver, is used in 
 cupellation. 
 
 Bone ashes are employed in cupelling metals containing gold 
 and silver, and some of the ores. The cupels are prepared by 
 moistening a small quantity of the ashes, mixed with a little soda- 
 salt to make it coherent, and by kneading the mass in the palm 
 of the left hand to the consistence of a stiff paste. A cylindrical 
 hole made in a piece of charcoal is then filled with the paste, and 
 after the surface is smoothed with the small agate pestle, a slight 
 depression is made in the centre, sufficiently large to hold the 
 metal or mineral to be cupelled, together with a small quantity 
 of the proof lead. The cupel is slowly dried by heating it care- 
 fully in a stove or over the flame of a spirit lamp. The assay 
 with the lead is then placed on the cupel and submitted to the 
 action of the exterior or oxidating blowpipe flame. By the in- 
 fluence of this, the lead is oxidized, and the fused litharge so 
 formed, is absorbed by the bone ashes, while the silver or gold is 
 left behind in the form of a brilliant globule ; which, before its 
 complete purification, exhibits the iridescence formerly described 
 under CUPELLATION. Plattner describes a convenient instrument 
 for making the cupels. 
 
 Oxide of Copper is used for the purpose of detecting chlorine. 
 
 Silicic Acid, when melted into a fusible glass with soda, is a 
 test for sulphur or sulphuric acid. The assay must, however, not 
 contain it. 
 
 Silver, in the form of wire or foil, is made use of for ascer- 
 taining the presence of sulphuret of potassium, or any other 
 soluble sulphuret. 
 
 Tin Foil sometimes assists in the reduction of metallic oxides, 
 which are dissolved in a bead of one of the fluxes, and by its use 
 we sometimes get a more satisfactory result than is obtained with- 
 out it. For instance, when a small quantity of copper is dissolved 
 in a bead of borax, or of microcosmic salt, and the glass is treated 
 in the reducing flame, it sometimes becomes ruby-red and opaque. 
 But if the amount of copper is so small that the reducing flame 
 cannot produce this result, a little tin added to the bead, and 
 heated with it, makes the proper appearance evident immediately 
 upon its cooling. 
 
 Iron wire, which is generally that metal in its purest state, 
 
 38 
 
594 BLOWPIPE TABLE. 
 
 precipitates some other metals from the different fluxes, or sepa- 
 rates therefrom sulphur and the fixed acids. It is also used to 
 reduce phosphoric acid to phosphorus, which, combining with iron, 
 forms a white brittle metallic globule, the phosphuret of iron. 
 
 Besides the above-mentioned tests, it is proper to have Formate 
 of Soda, which, when anhydrous, is used to detect arsenic in oxide 
 of antimony. Test papers colored with litmus, Brazil wood, and 
 turmeric, are also convenient. 
 
 The substances mentioned in the foregoing list as reagents, 
 are all of those which are essential to the completeness of the 
 blowpipe apparatus. While, however, occasions may arise for 
 the use of any or all of them, the great majority of examinations 
 with the blowpipe can be made with the aid of but a few, and the 
 possession of the first four or five upon our list, with the fluid 
 nitrate of cobalt and the metals referred to, may be considered 
 as quite enough to make the manipulator competent to pursue 
 ordinary investigations. 
 
 Blowpipe Table. In the laboratory all the instruments essen- 
 tial to the expedition of blowpipe analysis are placed within con- 
 venient reach of the operator. For this purpose Gahn's table, 
 
 Fig. 5(J4. 
 
 which has drawers both in the side and front, will be found very 
 useful. The side drawers are shown in Fig. 504, drawn out from 
 their usual position. The right hand drawer contains the appa- 
 
BLOWPIPE TABLE. 595 
 
 ratus most frequently used, and the left that which is less often 
 required. The lamp, blowpipe, fuel, wick, and other necessaries 
 of a rougher kind, occupy those in front. 
 
 The drawers are fitted with receptacles for each and every 
 article, so that they may rest securely, when moved ; and they 
 can therefore he readily formed into a travelling case. Chests, 
 however, for this purpose, are specially constructed with great 
 regard to economy of space and number of conveniences. Those 
 made by Lingke, comprise, in a case of about twelve inches 
 square, and admirably arranged with drawers and apartments, all 
 the implements and accessories for quantitative as well as quali- 
 tative blowpipe assays, including a compact and very delicate 
 balance with weights. 
 
 Having fulfilled our duty of describing the more practical 
 points of blowpipe operations, we refer the reader, for all other 
 necessary information, to the comprehensive treatises of Berzelius 
 and Plattner, both of which have been translated into English, 
 the first by Whitney and the second by Muspratt. 
 
 The annexed tables will also serve, conveniently, both as a 
 guide and for reference, in practical exercises. For testing by 
 them observe the following directions : 
 
 Fuse a globule of microcosmic salt on platinum wire ; add a 
 small quantity of the substance to be tested, and again heat to 
 redness in the oxidizing flame ; observe the color of the globule, 
 and allow it to cool, and again note its color. The substance 
 may thus be referred to one of six classes. If the globule is 
 colorless, add a further quantity of the substance to be tested, 
 and treat as before, in order to ascertain if the globule will become 
 opaque on saturation. Then heat the same globule in the redu- 
 cing flame, and again note its color. Repeat the operations with 
 a globule of borax, and, if necessary, apply the special tests given 
 under the head of Remarks to Individualize. 
 
596 
 
 TABLE FOR TESTING BY THE BLOWPIPE. 
 
 REMARKS. 
 
 
 Compounds containing chromium, when 
 fused with nitre and potash in a silver 
 crucible, yield a yellow mass, containing 
 chromic acid. 
 Compounds containing copper, when fused 
 with soda on charcoal, yield metallic cop- 
 per. Copper is malleable, and red in color; 
 is acted upon by nitric acid, giving a solu- 
 tion which is turned blue by an excess of 
 ammonia. 
 
 Compounds containing manganese, when 
 fused with nitre and potash (see 2), yield 
 a bright green mass (mineral chameleon). 
 
 On charcoal are only partially reduced; 
 with soda, on ditto, fuse, and are absorbed. 
 
 Compounds containing silver, on charcoal 
 in R. F., alone or with soda, are easily 
 reduced. Silver is easily fused, silvery 
 white in color, malleable, and not oxidiz- 
 able, B.B.; is soluble in nitric acid, and 
 the sol. yields a white curdy precipitate 
 with hydrochloric acid. 
 
 
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TABLE FOR TESTING BY THE BLOWPIPE. 
 
 597 
 
 
 
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598 
 
 TABLE FOR TESTING BY THE BLOWPIPE. 
 
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TABLE FOR TESTING BY THE BLOWPIPE. 
 
 599 
 
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600 
 
 TABLE FOR TESTING BY THE BLOWPIPE. 
 
 00 
 
 B 
 
 Compounds of mercury, when heated in a 
 tube with tin or iron filings, yield a gray 
 sublimate of metallic mercury, which, when 
 examined by a lens, is seen to consist of 
 
 minute globules. 
 Arsenical compounds, when heated in a 
 tube with black flux or cyanide of potas- 
 
 sium, yield a steel-gray mirror-like subli- 
 mate of metallic arsenic. This, when 
 
 heated in a current of air, diffuses an alli- 
 aceous odor, and yields a sublimate of ar- 
 senious acid, crystallized in brilliant co- 
 
 lorless octohedra. 
 
 Are easily reduced on charcoal, with soda, 
 in R.F. Metal very fusible, malleable, 
 silvery white in color; oxidizes in O.F., 
 and gives a non-volatile white oxide coat- 
 
 iwT */<e surface of the fused metal; areola, 
 none. 
 
 Is not reduced on charcoal. 
 
 Compounds of alumina, when moistened 
 with nitrate of cobalt, give a beautiful blue 
 enamel before the blowpipe. 
 Compounds of soda communicate a bright 
 yellow color to the blowpipe flame. 
 Compounds of lithia color the flame red. 
 
 if no soda is present. 
 Compounds of potash color the flame pale 
 lilac, or violet, if no soda is present. 
 
 Compounds of ammonia, when heated with 
 lime or potash, give off ammoniacal gas. 
 
 
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GLASS-BLOWING. 601 
 
 CHAPTER XXX. 
 
 GLASS-BLOWING. 
 
 THE ability to work glass over the lamp or blowpipe-flame is a 
 very desirable accomplishment for the chemist, as it enables him 
 to fashion for himself, and in accordance with his own judgment, 
 such micro-apparatus as is constantly in demand during experi- 
 mental research. The inconvenience and expense of having a 
 large stock of delicate glass instruments always at hand, and the 
 difficulty of obtaining such at all times, especially in localities 
 distant from the cities, render instruction in the art doubly de- 
 sirable. On these accounts, we think it proper to devote a chap, 
 ter to a few illustrations of the processes by which tubes are bent, 
 closed, rounded, widened, and drawn out, and by which bulbs are 
 blown and joints sealed. 
 
 The two principal pieces of apparatus required are a lamp and 
 a table blowpipe. The latter, as well as its management, have 
 already been written of at page 69. The former, known as Dan- 
 ger's " Glass-blower's Improved Lamp," of form shown by Fig. 
 505, is of sheet brass, and rests upon a tray designed for the 
 
 Fig. 505. 
 
 reception of any overflow of oil. These lamps are fitted with an 
 arrangement by which the wick may be raised or lowered, and 
 the flame consequently enlarged or diminished as desired: an 
 accompanying hood, or short conical chimney over the burning 
 wick, serves to increase the heat and to protect the eyes from the 
 smoke and flame. 
 
602 THE TABLE. 
 
 The wick may be made of common candle-wick, divided into 
 lengths of proper dimensions, and stranded together, so as to 
 form a diameter of about three-fourths of an inch. This bunch 
 is placed in that part of the lamp intended as its receptacle, and 
 should only protrude above the oil about the third of an inch. 
 It should be kept constantly supplied with oil or fat, and free 
 from "snuff" by frequent trimming. To obtain the highest pos- 
 sible heat from the lamp, the vent-hole in the nozzle c of the 
 blast table must be very small compared with the capacity of the 
 wind chest, and when it is desired to lessen the power of its flame, 
 as may be necessary in the heating of small tubes, the force of 
 the blast must be diminished. 
 
 The fuel may be olive, lard, sperm, or tallow oil ; the latter, 
 however, being preferable on account of its giving a hotter flame. 
 In case of the absence of a lamp of this sort, any common me- 
 tallic vessel, of proper size, may be fitted for use, upon the blow- 
 pipe-table, by training up upon, and allowing to overhang its 
 side, a thick bunch of wick. This may be kept in place, and its 
 flame, at the same time, be prevented from descending too far, 
 by encircling it with a tin or other metallic tube, or a coil of wire, 
 which may be temporarily connected with the sides of the vessel, 
 so as to answer all the intentions of support and the conduction 
 off of the excess of heat. 
 
 If the experimenter cannot have access to a properly made 
 blowpipe table, he may, in a very short time, construct a substi- 
 tute himself, which, however rough, will enable him to carry on 
 nearly all the operations of glass-blowing. A hollow reed or 
 piece of cane-angle, about a foot in length, may be firmly fixed 
 in a circular hole, drilled near the edge of a common table, and 
 which is just large enough to admit and hold it firmly in its place. 
 This may have adapted, by means of cement, plaster, or putty, 
 to its upper end, a nozzle of metal, or of glass drawn out to the 
 proper sized orifice, or one made of a piece of tobacco-pipe of the 
 requisite calibre. A bladder of the largest size, or bag of caout- 
 chouc, furnished with two openings upon the same part of its 
 circumference, is now firmly attached to the bottom of this tube, 
 in one of which a similar piece of reed, long enough, however, to 
 reach from the operator's knees while sitting to his mouth, 
 having been inserted and tied into the other opening. That end 
 
IMPLEMENTS. 
 
 603 
 
 of this last-mentioned tube which is within the bladder, should 
 be provided with a valve, like that of a cupping-glass, made by 
 placing loosely over it, a long strip of oiled silk, of the diameter 
 of the tube, folding the ends upon the body of the reed and 
 tying them firmly to it by waxed thread. This valve admits the 
 passage of air into the receptacle, but will not allow its return 
 through the same orifice, so that pressure upon the bladder will 
 compel its exit through the nozzle of the tube which is fixed in 
 the table. If, then, the operator, sitting near the table, with the 
 bladder hanging between his knees and the loose tube fixed in 
 his mouth, inflates the former, and then presses upon it uniformly 
 with his knees, a continuous current is expelled from the nozzle 
 upon the flame of the wick placed directly above it. A repeti- 
 tion of the inflation only becomes necessary when the bladder is 
 nearly emptied of its contained air. The inflation of this home- 
 made apparatus is scarcely, if at all fatiguing ; and it gives to 
 the glass-blower the unincumbered use of both his hands. Russia 
 lamps, and similar implements, described in Chapter XI, may, in 
 many cases of glass-blowing, be substituted for the blast-table 
 and Danger lamp. 
 
 Fig. 506. 
 
 The position of the jet upon the top of the table, and that of 
 the operator before it, are shown in the annexed drawing. 
 
604 
 
 IMPLEMENTS. 
 
 When it is desired to use the gas flame, the straight jet and 
 Argand burner, as is shown in the annexed drawing, are em- 
 ployed. It is still better, in ordering a blast-table, to have pre- 
 pared a movable jet, with ball and socket joint, suitable for giving 
 the flame a horizontal or vertical direction, as may be required. 
 
 The other implements are an iron piercer with wooden handle, 
 Fig. 507, a cone of biscuit-ware or soap-stone, Fig. 508, for 
 
 Fig. 507. 
 
 Fig. 503. 
 
 Fig. 509. 
 
 widening the necks of tubes, a small pair of brass tongs, Fig. 
 509, for fashioning bulbs, &c., a small piece of smooth hoop-iron, 
 styled the marver, a hardened cast-steel knife, and one or two 
 three-cornered files for cutting tubes and rods. 
 
 In addition to the above, the table should be supplied with a 
 stock of tubes and rods, of assorted diameters, and made of glass 
 free from lead. They should, moreover, be very uniformly 
 regular throughout, and exempt from flaws or striae. 
 
 To prevent the table from being incumbered and uncleanly, the 
 
 Fig. 510. 
 
 Fig. 511. 
 
 long tubes should be kept in a rack like that shown by Fig. 510, 
 and the shorter pieces in one as presented by Fig. 511. 
 
CUTTING OP GLASS. 605 
 
 Before commencing operations, the wick must be evenly 
 trimmed and parted in the middle, so that when the jet is placed 
 opposite in the rear, and in proper relation, it may drive the 
 flame* forcibly in advance, but not of too great length, else it will 
 become smoky. 
 
 Tubes can very readily be severed, or divided into lengths, by 
 scratching them with a file, and breaking asunder as at Fig. 519. 
 For large tubes, the scratch must extend entirely around the 
 circumference. 
 
 Vessels of larger diameters, such as necks of retorts, and the 
 like, require the use of a diamond spark. According to Mr. Nas- 
 myth, coke has the property of cutting glass, and can very well 
 be substituted for the diamond. 
 
 When the scratch of the file is insufficient to effect a smooth 
 division, it must be moistened and then traced with a heated wire 
 or pastile. A heated wire will also divert a crack in a glass ves- 
 sel to any desired direction. 
 
 The tubes or rods, previously divided into the required length, 
 should always be wiped perfectly dry before being subjected to 
 the action of the flame, and then carefully and gradually heated, 
 the uniform diffusion of the heat being effected by keeping them 
 revolving ; these precautions, which are always to be observed, 
 prevent breaking from sudden and unequal heating. After being 
 heated, they must be removed gradually from the fire, and laid 
 upon a piece of charcoal, so as to become annealed, as it were, 
 by gradual cooling. 
 
 The most simple and easily performed of all the operations of 
 
 Fig. 512. 
 
 glass-blowing, is the rounding of edges, which is readily done by 
 heating them to softness in the flame during constant revolution 
 
606 TUBES CEMENTED TUBES BENT. 
 
 of the tube between the thumb and three fingers, which support 
 it. This operation, by which the edges of tubes and rods are 
 smoothed, is also preliminary to that of widening the mouth of 
 a tube, a test-tube for example, which is done by spreading it 
 while hot, as shown in Fig. 512, by means of the iron piercer, 
 or, better, the biscuit cone, either of them being previously 
 warmed, and then carried round the opening with an outward 
 pressure. 
 
 Tubes Cemented. Tubes or rods are also cemented together 
 
 by softening their ends and blowing gently through them at the 
 
 moment of junction. Care must be taken 
 
 Fig. 513. to hold them firmly and perfectly even, 
 
 ^^-jjifr- .L,jj-.'w as S ^ own i* 1 -Fig- 513, and to retain hold 
 ; .--J||' of the joined tube until it has entirely 
 
 cooled, else it may bend by its own weight 
 at the heated part, and thus become crooked. 
 
 If the tubes to be cemented are of unequal diameters, the wider 
 one must be closed at its end, then heated in the flame and 
 quickly blown into a thin bulb, as shown by A, Fig. 514. This 
 
 bulb is then broken off so as to 
 Fig< 514> leave only a shoulder at the mouth 
 
 B. This being done, the end of 
 the small tube is next blown in 
 the same manner, as at c, and the 
 two shoulders are then to be ce- 
 mented as before directed. 
 
 Kods are cemented together by partially fusing their ends and 
 bringing them carefully together, and pressing them until they 
 adhere. The welding is then completed by heating the new joint, 
 during which process, in order to impart shape, the rods must be 
 kept rotating, and be alternately drawn out and brought together, 
 until the junction is as smooth and uniform as any other part of 
 the surface. 
 
 Tubes Bent. Very small tubes can be bent over the spirit 
 lamp, Fig. 151 ; but larger ones require the force of the blow- 
 pipe-flame to heat them. The operation of bending consists in 
 heating the tube to dull redness, about an inch on either side 
 beyond the point of the intended curve, by revolving it in the 
 flame, and just at the commencement of softening, in making an 
 
DRAWING OUT, 
 
 607 
 
 angle, by bending it dexterously, but very gradually, in the de- 
 sired direction until it assumes the required form. In order to 
 prevent a wrinkled, and consequently very fragile elbow, Fig. 515, 
 it is necessary that the operation of bending shall be accomplished 
 by progressive steps, as illustrated by Fig. 517. Closing the 
 
 Fig. 515. 
 
 Fig. 516. 
 
 Fig. 517. 
 
 tube at one end, and blowing gently into the other, during flexion, 
 so as to produce internal pressure, will also counteract any ten- 
 dency to malformation. 
 
 Drawing Out. When a tube is to be drawn out, either as pre- 
 liminary to further working, or in the preparation of nozzles for 
 washing-bottles, or other purposes, one of the proper size is taken, 
 at the ends, between the thumb and index of each hand, and 
 along its length with the other fingers, and kept revolving gradu- 
 ally over the flame until it becomes red, and commences to soften 
 at the heated part. It is then taken from the fire and drawn 
 apart, as shown in Fig. 518. In this way also stirring-rods are 
 
 Fig. 518. 
 
 pointed, and when the tips of either tubes or rods thus wrought 
 are to be smoothed, it is only necessary to divide or break across 
 the centre of the part drawn out, and to heat the surfaces in the 
 flame until they soften and become round. The proper mode of 
 severing glass rods or tubes, is first to make a deep scratch with 
 a three-cornered file in the spot where separation is required, and 
 then, after grasping them as shown in Fig. 519, by gently break- 
 ing them apart. 
 
608 TUBES CLOSED DRAWING OUT AND CLOSING. 
 
 Fig. 519. The tube must not be kept in the 
 
 fire too long, nor yet drawn out 
 too rapidly. When the tube or rod 
 is too short to be divided, it may be 
 drawn out at either of its ends by 
 
 means of a punto a piece of glass rod which is heated to soft- 
 ness and cemented to the other as a handle. 
 
 Tubes Closed. Very small tubes may readily be closed by 
 
 softening their edges over a flame, and rotating them until they 
 
 unite and adhere. Tubes of larger size are treated in the same 
 
 way, but to facilitate their closure, occasional pressure of the hot 
 
 end against the back of the tool, Fig. 509, and sometimes gentle 
 
 blowing through the open end, are required. 
 
 Fig. 520. Tubes also are closed hermetically by draw- 
 
 R ing out one end, as shown in Fig. 520, by 
 
 i&feM ^>=<r~ll then scratching with a file and breaking 
 
 asunder the part #, and finally by closing 
 
 the small orifice by fusion in the flame. 
 
 Drawing Out and Closing. When it is desired to form a ves- 
 sel like a test-tube, a tube of the required diameter is drawn out, 
 as at Fig. 521, and then cut asunder at a. The two pieces thus 
 formed, serve to make two test-tubes. For that purpose, it is 
 necessary to heat the smaller end of each to softness, and imme- 
 
 Fig.521. 
 
 I 
 
 Fig. 522. 
 
 diately upon removal from the flame, to blow cautiously and 
 slowly into the open extremity until the closed end assumes a 
 uniform spherical shape. Sometimes it is necessary to repeat the 
 heating and blowing, in order to fashion the bottom perfectly, as 
 seen in Fig. 523. If the piece of glass is only long enough to 
 form one tube, its end can be drawn out by attaching a punto, as 
 before described, and now shown at 5, Fig. 522. This punto, or 
 
LATERAL ATTACHMENTS. 609 
 
 glass rod handle, serves also to remove any redun- 
 dant glass, it being only necessary for that purpose Flg< 523 ' 
 to heat the closed end highly, to apply the punto a 
 little less heated, and after collecting upon its end ,,,, TF -^ 
 
 as much of the surplus melted glass as is required to 
 make the bottom thin and capable of supporting sudden changes 
 of temperature, to draw it off. This manipulation requires some 
 dexterity, which is, however, easily acquired by slight practice. 
 If at one heating and gathering, the bottom has been reduced to 
 the proper thinness, it may be heated anew, removed from the 
 fire, and then by slow and gentle blowing, through the open end, 
 the bottom may be blown out to roundness. The mouth of the 
 tube is then finished as directed at page 605, Fig. 512. 
 
 Lateral Attachments. To attach a tube to the side of another 
 is somewhat difficult. For this purpose, the tube with which the 
 junction is to be effected is closed at one end and heated at the 
 desired point, such as 5, Fig. 524, to high redness. To this hot 
 part a glass rod, or punto c, slightly heated, is attached and 
 drawn out, as shown in the figure. When the glass has cooled, 
 
 Fig. 524. Fig. 525. 
 
 cut off the new joint at 5, heat again in the flame, and widen its 
 mouth with the tool, Fig. 507, to the size of the diameter of the 
 tube which is to be joined with it. This having been done, the 
 tube is to be attached as directed at page 606. Fig. 525 shows 
 the joint perfected. 
 
 Another mode is. to heat and close the drawn out end, and to 
 blow forcibly through the tube until the bulb, thus formed, bursts. 
 All the remains of the thin glass bulb being broken off, a pro- 
 truding aperture is left, to which the lateral tube may be ce- 
 mented, in the usual way, by heating the edges of the ends of the 
 two tubes to be united, joining them in the flame with slight 
 compression, heating the joint to redness, and then slightly blow- 
 ing, to give form and prevent cracking. 
 
 To Blow Bulbs. To form a bulb at the end of a narrow tube, 
 
 39 
 
610 
 
 BULBS. 
 
 Fig. 526. 
 
 it is only necessary to continue heating it after closure until it 
 commences to soften, and then, immediately upon its removal 
 from the flame, to blow into the open end, as in Fig. 526, slowly, 
 until the heated part expands to the proper size and shape. Care 
 must be taken to heat the tube to a suffi- 
 cient extent, so that there may be enough 
 glass softened to give a bulb of the re- 
 quired size; moreover, during both the 
 heating and blowing the tube must be 
 kept slowly rotating between the fingers, 
 so as to prevent an accumulation of the 
 melted glass, by its own weight, in any 
 one part. 
 
 To blow a bulb in the middle of a tube, 
 the latter must be heated at its centre 
 
 during constant but slow rotation between the fingers, and then 
 carefully blown into at one end, whilst the other is closed with 
 the finger, a cork, or a piece of wax. The pressure of the air 
 within expands the hot glass into a spheroid, regular or irregular 
 in form, according to the care and skill of the operator. The 
 part of the tube to be expanded must be heated uniformly, and 
 kept in constant and slow revolution during both the heating and 
 blowing. 
 
 In the fashioning of certain glass-tube apparatus, it is some- 
 times necessary to blow the bulbs separately, and to attach them 
 afterwards to their adjacent parts ; the bulb is then formed as 
 follows. Take a glass tube A, Fig. 527, of the required dia- 
 
 Fig. 527. 
 i a 
 
 u ? A. 
 
 meter and length, heat it at the points a and 5, and draw it out 
 in two places, as shown at r s in B. When the tube has cooled, 
 divide it at the attenuated parts r 8 with the file, as directed at 
 page 608, Fig. 519, and close one end of one of the pieces in the 
 flame. Then hold it by the other end, which is drawn out, heat 
 
WELTER'S TUBES. 
 
 611 
 
 it to redness, and fashion the bulb by blowing, as above directed, 
 until it assumes the shape of G. It is then cemented to the 
 other parts of the apparatus, as directed at page 606, the pre- 
 vious widening of the drawn-out parts being performed as at Fig. 
 512. 
 
 Thermometer bulbs are made by expanding, as above directed, 
 the heated end of tubes with a capillary bore. 
 
 To Make a Welter's Tube. By way of illustrating the dif- 
 ferent operations of fashioning glass tubes over the blowpipe 
 flame, we will go through the different stages of manufacture of 
 the safety-tubes of Welter. A straight tube is first bent into 
 form, as at A, Fig. 527, and the flame is directed upon a; as 
 
 Fig. 528. 
 
 ttt 
 
 soon as the glass softens at that point one end of the tube is 
 closed with the finger, and the other is blown into forcibly, so as 
 to form the very thin, brittle bulb represented by the dotted lines. 
 When the tube is thick, a repetition of the heating and F . 52Q 
 blowing is required. This bulb is then broken off, and 
 the bent tube, thus formed, is ready to be attached to 
 the straight tube B. This latter is formed of a separate 
 tube, and having a bulb b blown into its centre, is ce- 
 mented to A at , in the manner before directed. The 
 funnel top of the tube B, is formed by first blowing a 
 bulb c on its upper end to extreme thinness, removing it 
 with the file and cementing a bulb, with open mouth, as 
 at x in D. The s form is given merely by bending B in 
 the proper direction. 
 
CORKS. 
 
 "Instead of an open bull at the top of the D tube, a small 
 funnel is cemented to it, as in the fashioning of funnel-tubes, 
 Fig. 529. 
 
 CHAPTER XXXI. 
 
 CORKS. 
 
 CORKS are in many ways indispensable for laboratory purposes, 
 and the stock should consist of all sizes ; those for mounting 
 apparatus being necessarily of the finest velvet kind, smooth and 
 as free as possible from imperfections. 
 
 An excellent means of increasing the elasticity of corks is 
 compression by a small apparatus, Fig. 530, sold for the purpose. 
 
 Fig. 530. 
 
 This treatment renders them capable of being fitted to apertures 
 with great nicety and ease. For trimming them, as may be 
 sometimes necessary, a sharp knife must be used. The cut sur- 
 face can then be made perfectly smooth with a fine, flat file. 
 
 We have frequently made mention of the adaptation of tubes 
 and other parts of apparatus by means of perforated corks. 
 These perforations may be made with a hot metallic rod, and 
 
 Fig. 531. 
 
 afterwards enlarged with a rat-tail file; but a much smoother 
 and neater hole can be made with a cork-borer, Fig. 531, which 
 
CORKS. 
 
 613 
 
 Fig. 532. 
 
 is intended specially for this purpose. It consists of a series of 
 brass tubes of uniform length, but varying from an eighth to one 
 inch in diameter, and fitting one within 
 the other. The sizes contained in such 
 a series are equal to all the requirements 
 of the laboratory, as holes of smaller or 
 larger dimensions than the above ex- 
 tremes are seldom required. Each of 
 the tubes is open below, but closed at 
 the top with a cap c, Fig. 532, through 
 which is a hole b for the passage of a 
 stiff wire d, which serves both as a handle 
 and as a punch for ejecting the cores 
 from the tube after the perforation of 
 the cork. 
 
 The drawing exhibits one of the tubes 
 of the series already in operation, it 
 
 being only necessary to bring its base upon a cork, and to effect 
 the perforation by pressure upon the cap and a slight circular 
 motion. The core or part of the cork removed, ascends into the 
 barrel a of the tube, and must be ejected by the force v of the 
 punch d. As the tubes become dull on the edges, they may be 
 sharpened upon a grindstone or with a fine file. 
 
 As a familiar illustration, we exhibit in Fig. 533 a cork 
 thus treated, with tubes inserted in the perforations. Their con- 
 Fig. 533. 
 
 venience is shown in many of the arrangements of which we have 
 given drawings. 
 
 When the corks are not of good quality, they may be rendered 
 impermeable by coating their surfaces with soft cement. 
 
 India rubber corks have lately appeared in the market : they 
 are made by Goodyear, and answer admirably as cheap stoppers 
 of bottles containing substances which are volatile, and which 
 do not corrode the caoutchouc. 
 
614 WEIGHTS AND MEASURES. 
 
 CHAPTER XXXII. 
 
 WEIGHTS AND MEASURES. 
 
 THE following tables of the corresponding values of French 
 and English weights and measures will be found very useful for 
 reference, as the decimal system of the French, owing to its 
 greater convenience for calculations, is extensively adopted in 
 chemical works. 
 
 The unit of the French weight is the gramme, which is the 
 weight of the hundredth part of a cubic metre of distilled water, 
 at the temperature of melting ice. Below are some comparative 
 tables, which will serve to give every explanation. 
 
 Grammes. Troy Grains. 
 
 Milligramme = -001 = -01543 
 
 Centigramme = -01 = -15434 
 
 Decigramme = ! = 1'5434 
 
 TROY WEIGHT. 
 English weights. French weights. 
 
 1 grain = ^ dwt. = 0-06477 gramme. 
 
 1 pennyweight = ^th of an ounce = 1-55456 gramme. 
 
 1 ounce = ^th of a Ib. Troy = 31*09130 grammes. 
 
 1 pound imperial = 0*3730956 kilogramme. 
 
 AVOIRDUPOIS WEIGHT. 
 
 English. French. 
 
 1 drachm = y^th of an ounce = 1-7712 gramme. 
 
 1 ounce = y^th of a pound = 28-3384 grammes. 
 
 1 pound or 1 pound imperial = - 4534148 kilogramme. 
 
 1 cwt. . =112 pounds = 50-7824600 kilogrammes. 
 
 1 ton = 20 cwt. = 1015-6490000 kilogrammes. 
 
 
 
 Grammes. 
 
 
 Troy grains. 
 
 Gramme 
 
 =3 
 
 1 
 
 
 
 15-434 
 
 Decigramme 
 
 mm 
 
 10 
 
 = 
 
 154-34 
 
 Hectogramme 
 
 = 
 
 100 
 
 == 
 
 1543-4 
 
 Kilogramme 
 
 mm 
 
 1000 
 
 = 
 
 15434 
 
 Myriagramme 
 
 = 
 
 10000 
 
 = 
 
 154340 
 
 Or: 
 
 French. English. 
 
 1 gramme = 15-438 grains troy = 0-643 dwts. = 0-03216 oz. Troy. 
 1 kilogramme = 2*68027 Ibs. = 2 Ibs. 8 oz. 3 dwts. 6 grs. Troy wt. 
 1 kilogramme = 2-20548 Ibs. = 2 Ibs. 3 oz. 4| drs. Avoirdupois. 
 1 myriagramme = 22 '0485 Ibs. Avoirdupois. 
 1 quintal = 1 cwt. 3 qrs. 25 Ibs. 
 
WEIGHTS AND MEASURES. 
 
 615 
 
 The unit of superficial measure is "the are, a surface of ten 
 metres each way, or 100 square metres. The unit of measures 
 of capacity is the litre, a vessel containing the cube of a tenth 
 part of the metre, and equivalent. to 0-220097 parts of the British 
 imperial gallon. The standard temperature is 32 F. All the 
 divisions and multiples of the units are decimal." 
 
 MEASURES OF LENGTH. 
 
 Myriametre 
 Kilometre 
 Hectometre 
 Metre 
 
 10,000 metres. 
 1000 " 
 100 " 
 1 " 
 
 Decimetre 
 Centimetre = 
 Millimetre = 
 
 0-1 metres. 
 0-01 
 0-001 " 
 
 MEASURES OF SURFACE. 
 
 Hectare = 1000 sq. metres. 
 
 Are = 100 " 
 
 Centiare = 1 " 
 
 Kilolitre 
 
 Hectolitre 
 
 Decalitre 
 
 MEASURES OF CAPACITY. 
 
 1000 litres. 
 
 100 " 
 
 10 " 
 
 Litre 
 
 Decilitre 
 
 Centilitre 
 
 1 litre. 
 
 0-1 
 
 0-01 
 
 The unit of solid measure is the stere, or cube of the mStre, 
 equal to 85-31658 English cubic feet. 
 
 MEASURES OF LENGTH. 
 English. 
 
 1 inch or ^ of a yard ... 
 1 foot equal = of a yard = 12 inches 
 1 yard = 3 feet .... 
 1 fathom = 2 yards ... 
 
 1 pole or perch = 5J yards 
 ] furlong = 220 yards - 
 1 mile, or 1760 yards - - * 
 
 LONG MEASURE. 
 
 French. 
 
 =, 2-539954 centimetres. 
 a 3-0479449 decimetres. 
 = 0-91438348 metre. 
 = 1-82876696 " 
 = 5- 02 9 1 1 000 metres. 
 = 201-16437000 
 = 1609-31490000 
 
 French. 
 1 millimetre 
 1 centimetre 
 1 decimetre 
 1 metre 
 1 decametre 
 1 hectometre 
 1 kilometre 
 1 myriametre 
 
 0-039370 
 0-393708 
 3-937079 
 39-37079 
 393-7079 
 3937-079 
 39370-79 
 393707-9 
 
 English. 
 
 = 1-093633 yards. 
 
 = 10-936630 " 
 
 = 109-366300 " 
 
 = 4 furlongs, 213-633 yards. 
 
 =* 6 miles, 1 furlong, 156-288 yards. 
 
616 WEIGHTS AND MEASURES. 
 
 French. English. 
 
 1 toise = 6-3945 feet = 2-1315 yards = 76-735 inches. 
 1 aune or ell = 3'893 feet = 46'79 English inches, 
 
 SQUARE MEASURE. 
 
 English. French. 
 
 1 square yard - - - - - - = 0-836097 metre carre*. 
 
 1 rod or pole = 30 sq. yards - = 25-291939 metres carr^a. 
 
 1 rood = 1210 sq. yards - - -""' = 10-116775 ares. 
 
 1 acre = 4840 sq. yards = 40-4671 ares = 0-404671 hectare. 
 
 1 metre carre" = 1 centiare, = 1*196033 sq. yard. 
 
 1 are = 3-95 English poles . V - - = 0-98845 rood. 
 
 1 hectare = 2 acres, 1 rood, 5 perches, - = 2-473614 acres. 
 
 MEASURES FOR LIQUIDS. 
 English. French. 
 
 1 pint or fth of a gallon = 0-567932 litre. 
 
 1 quart or ^th of a gallon = 1-135864 litres. 
 
 1 imperial gallon = 4-5434579 " 
 
 DRY MEASURE. 
 
 English. French. 
 
 1 peck = 2 gallons = 9-0869159 litres. 
 
 1 bushel = 8 " = 36-347664 " 
 
 1 sack == 3 bushels == 1-09043 hectolitre. 
 
 1 quarter = 8 " = 2-907813 hectolitres. 
 
 1 chaldron = 12 sacks = 13-08516 " 
 
 French. English. 
 
 1 litre = 1-760773 pints = '8803865 qts. = -2200966 gallons. 
 
 1 decilitre = 2-2009667 " 
 
 1 hectolitre - - T ,***.*" =22-0096670 " 
 
 As a greater convenience for common purposes, the French 
 denominations were, in 1812, arranged as follows : 
 
 1 toise or 6 feet = 2 metres = 6-5618334 English feet. 
 1 foot or 12 inches = metre = 1-0936389 " foot. 
 1 inch or 12 lines - - = 1-0936389 " inch. 
 1 line - ,7 *' = 0-0911365 " 
 
 1 aune or ell =1 | mdtre = 3 937 English feet: Or, 
 1 aune - * ^'V** = 47-244 tl inches. 
 
 1 bushel = f hectolitre == 762-85 cubic inches. 
 
 1 old Paris foot = T066 English foot. 
 1 old Paris inch = 1-066 " inch. 
 1 old line = O'OSSS " 
 
 The metre, the square metre, and the cubic metre, are the 
 radical standards of the three measures ; for there are only three, 
 
WEIGHTS AND MEASURES. 617 
 
 as solidity and capacity, differently named and used, are the same 
 in reality. From these radical denominations, namely, the metre 
 of the lineal measure, the are of the superficial measure, the litre 
 of measured capacity, and the stere of solid or cubic admeasure- 
 ment, the larger ones are procured by multiplying by ten, and 
 the lower ones by dividing by the same. Thus, 
 
 ti prefixed, means 10 times. 
 Hecto, 100 
 
 Kilo, " " '1000 " 
 
 Myria, " 10,000 " 
 
 The number is understood to multiply the surface of the solid 
 and not its side ; thus, one decare. is ten ares, not a square of ten 
 times the side of an are, and so of the others. 
 
 The denominations below the radical ones are expressed by a 
 sort of Latin prefix : thus, 
 
 . Deci is one-tenth. 
 Centi is one-hundredth. 
 Milli is one-thousandth. 
 
INDEX. 
 
 A 
 
 ACIDS, filtration of, .* '* 
 
 511 
 328 
 402 
 116 
 
 
 . 270 
 
 oil, 
 
 . 270 
 
 liquid, evaporation by, 
 desiccation by, . 
 filter, .... 
 
 . 467 
 . 479 
 . 479 
 
 Adie's sympiesometer, . . > ' .. 
 Adjustment of balances, . 
 
 Balloons for weighing gases, . 
 Barometer . 
 
 . 126 
 . 386 
 
 Air, analyses of, 
 heated, evaporation by, . 
 Air-pump, .... 70 
 
 546 
 468 
 126 
 225 
 231 
 
 135 
 
 396 
 200 
 522 
 549 
 582 
 403 
 547 
 
 
 . 386 
 
 Wheel 
 
 . 387 
 . 389 
 
 
 . 388 
 
 
 
 . 389 
 
 Alexander's method for taking speci- 
 fic gravity, .... 
 
 Troughton's, . 
 Hassler's, 
 Alexander's, 
 
 . 391 
 . 394 
 . 396 
 . 399 
 
 Alkalimeter, Schuster's, 
 Amalgam for electrical machines, . 
 Amalgamating battery zincs, . 
 Analysis by blowpipe, . 
 Aneroid barometer, 
 Anode, 
 
 Morland's diagonal, . 
 Adie's sympiesometer, 
 Aneroid, .... 
 
 . 400 
 . 402 
 . 403 
 . 406 
 
 Water, . 
 Wollaston's, . 
 Regnault's, 
 
 . 402 
 . 407 
 . 407 
 . 407 
 
 Areometer, '. 
 
 134 
 
 134 
 , 69 
 345 
 312 
 113 
 225 
 537 
 
 28 
 101 
 102 
 108 
 111 
 113 
 113 
 114 
 115 
 116 
 533 
 131 
 271 
 %*> 
 
 
 Argand burner, ... 64 
 Arsenic apparatus, Marsh's, . 
 
 construction of, . ",..*# 
 adjustment of, . 
 
 . 408 
 . 410 
 . 411 
 
 Assay balance, .... 
 furnace, ..... 
 Astatic galvanometer, . 
 
 B. 
 
 Barren's furnace, . . . 
 Barometric corrections, . 
 Batteries, electrical, . ^-^ 
 
 . 226 
 . 414 
 . 525 
 . 547 
 
 efficiency of, 
 construction of, . 
 local action in, . 
 amalgamating, . 
 Wollaston's, 
 Daniell's, . 
 Smee's, 
 Grove's, . 
 Bunsen's, . 
 connections, 
 wire for, . 
 arrangement of, 
 power of, . 
 for plating, . 
 Baume's hydrometer, 
 tables for, . . . 
 Beale's gas furnace, 
 3eindorfl 's apparatus, 
 Bennett's electrometer, . 
 
 . 549 
 . 549 
 . 549 
 . 549 
 . 549 
 . 551 
 . 553 
 . 554 
 . 555 
 . 556 
 . 557 
 . 562 
 . 562 
 . 566 
 . 145 
 . 145 
 . 246 
 . 54 
 . 530 
 
 description, test, and use of, . 
 
 Kater's and Robinson's, . 
 Berlin, . 
 
 Assay, 
 Tralle's 
 
 Platform, . 
 preservation of, 
 adjustment of, . 
 Torsion, Coulomb's 
 Hydrostatic, 
 Baths, sand, . . 31, 66, 
 
 
 266 
 268 
 
 saline, . . . +' 
 
620 
 
 INDEX. 
 
 Bell glasses 368 
 
 for weighing gases, . . . 126 
 
 Berlin balance, ' . . . . Ill 
 
 Berzelius' lamp, . . . .233 
 
 combustion tube, . . 307 
 
 washing bottle, . . . 415 
 
 Binding screws 556 
 
 Black lead crucibles, . . .279 
 
 flux, 294 
 
 Bladder, 381 
 
 Blast furnaces, . . . .219 
 
 lamp, Deville's, . . .238 
 
 Nunn's, . . . .239 
 
 Sonnenschein's, . . 257 
 
 B lowing glass, ''. . . 69,601 
 
 Blowpipe table, .... 69 
 
 compound, . . . .251 
 
 mouth, 572 
 
 Gahn's, . . . . .574 
 Mitscherlich's, . . .575 
 
 De Luca's 575 
 
 gas-lamp, . 576 
 
 lamp, Harkort's, 576 
 
 use of, . . 577 
 
 the flame, . . 578 
 
 oxidation, . 580 
 
 reduction, .-. 58i 
 
 supports, 582 
 
 instruments for analysis, . . 585 
 Herapath's tables for testing by, 
 
 . 596-600 
 
 reagents, .... 590, 593 
 table, . . .69, 594, 603 
 testing by, .... 595 
 
 Blue pots, 279 
 
 Boiling, 445 
 
 by steam, 450 
 
 in beaker glasses, . . . 448 
 tubes,' . . .445 
 flasks, . . . .448 
 capsules, . . . . . 449 
 
 Bottles, 73 
 
 labels for, 76 
 
 for test series, . ... 83 
 Bottles for spec, grav., . . . 132 
 
 Wolffe's 351 
 
 Spritz, 506 
 
 Washing, . . . . .507 
 
 Berzelius's, . . . 515 
 
 Gmelin's, .... 516 
 
 Cooke's, . 4 . .517 
 
 Bronze Powder, . . . .569 
 
 Bronzing, 572 
 
 Bunsen's Battery, .... 555 
 Bulbs, glass, blown, . . 609,610 
 
 C. 
 
 Cadet's apparatus, .... 458 
 Calcination, . . . . 298 
 
 Calcining furnace, .... 223 
 Calorific electrometer, . . . 533 
 Calorimotor, Hare's, . . . 564 
 Capsules, .... 450, 463 
 
 Caoutchouc, 380 
 
 for joints, . . . .381 
 
 Celsius thermometer, . . . 208 
 
 Cement, soft, 382 
 
 resin, 382 
 
 iron, ...... 383 
 
 for glass, . . . . .383 
 
 steam joints, . . . 384 
 
 labels 385 
 
 Centigrade thermometer, . 208 
 
 Charcoal for fuel, ... 228 
 
 Chemical tables, ... 191 
 
 reaction, crystallization by 477 
 
 Chloride of calcium tube, . 489 
 
 Cistern barometer, . . . 388 
 
 Clarke's combustion tube, . 307 
 
 Cleaning of glassware, . . 77 
 
 Cloth filters, .... 509 
 
 Coffee's syphon, . . v . 496 
 
 Cohobation, . . . ' 340 
 
 Collection of gases, . . . 350 
 
 over air, ..... 372 
 
 Combustion in glass tubqs, . . 308 
 
 Condensers, 324 
 
 Gedda's, 48 
 
 Schrader's 324 
 
 Liebig's 330 
 
 Compound blowpipe, . . 251 
 
 Ritchie's, ... 255 
 
 Tale's, .... 256 
 
 Cooke's washing bottle, . 517 
 
 Copper solutions for electro-metal 
 
 lurgy, .... 570 
 
 Cooling mixtures, . . . 272 
 
 table of, 274 
 
 Corks 612 
 
 fitting of, . . . . 612, 613 
 
 borer, . . . . 613 
 
 612 
 
 Coulomb's electrometer, 
 Crown of cups, .. , 
 Crucible jackets, 
 Crucibles, clay, 
 
 black-lead, -.'- 
 porcelain, . . i 
 iron, 
 
 533 
 547 
 234 
 278 
 279 
 279 
 281 
 
 silver, 281 
 
 platina, ..... 282 
 
 use of, 284 
 
 Crushing, 88 
 
 Crystals, purification of, . . . 475 
 
 drying of, 479 
 
 Crystallization, .... 472 
 
 by fusion, 472 
 
 sublimation, . . . 472 
 Crystallization, by solution, . . 473 
 
 granular, 474 
 
 by chemical reaction, . . 477 
 Cupel, furnace, .... 225 
 
 Cupels, 310 
 
 Cupellation 312 
 
 Curtains, with spring rollers, . . 22 
 Cushions, for electrical machines, . 522 
 Cylinder, " " " . 519 
 
 D. 
 
 Daniell's pyrometer, 
 battery, . 
 
 205 
 551 
 
INDEX. 
 
 621 
 
 561 
 301 
 575 
 129 
 
 478 
 479 
 479 
 480 
 485 
 
 Darcet's digester, .... 442 
 Decantation, ..... 493 
 
 washing by, . . . . 494 
 
 Decoction, 438 
 
 Decolorization, ', . .511 
 Deflagration, . . . . .300 
 
 by electrical action, . 
 Decrepitation, 
 De Luca's blowpipe, 
 Densities of bodies, 
 Desiccation of solids, 
 of filters, 
 
 by water-bath, ,^ 
 hot air, 
 
 of easily alterable substances, 
 
 in vacuo, ..... 487 
 
 of liquids, . .' . .488 
 
 gases, . . . .488 
 
 apparatus for, . . 489 
 
 Deville's blast lamp, . . .238 
 
 gasometer t .... 365 
 
 Diaphragms, for batteries, . . 553 
 
 Differential thermometer, . .211 
 
 galvanometer, . . ..V . . 539 
 
 Digestion, . /. .' *< . . 439 
 
 in beakers, . . . 440 
 
 flasks 441 
 
 under pressure, . . . 441 
 
 Digesters, Papin's, .... 441 
 
 D'Arcet's, . . . .442 
 
 Mohr's, , . . . . 444 
 
 Displacement, 452 
 
 solution by, .... 452 
 
 Robiquet's apparatus, . . 453 
 
 Payen's, " . . 455 
 
 Distillation, . 314, 334 
 
 of liquids, . . . .335 
 
 gases, . . . .340 
 
 in tubes, . . . . .330 
 
 retorts, . . . . 325 
 
 vacuo, .... 374 
 
 dry, 375 
 
 micro-chemical, . . . 330 
 
 by steam, 373 
 
 destructive, .... 375 
 
 Discharger, electrical, . . . 527 
 Dippers, . . .... . . 507 
 
 Donovan's filtering apparatus, . 512 
 Dropping-tubes, .... 201 
 
 Drummond light, .... 254 
 
 Drying-tubes, 489 
 
 chamber, .... 32 
 Duvoir's boiling vats, . . .46 
 
 E. 
 
 Earthenware retorts, . . .333 
 Ebullition, . ', . . . . . 445 
 Edulcoration, .... 515 
 
 Efflorescence, . . . .478 
 
 Electrical machine, cylinder, . 519 
 
 plate, 521 
 
 construction of, ... 522 
 cushions for, .... 52$ 
 amalgam for, .... 522 
 conductors for, . . . 222 
 preparation for use of, . . 523 
 
 Electrical battery, .... 525 
 
 discharger, .... 527 
 
 relations of the metals, . . 548 
 
 conducting power of the metals, 549 
 
 decompositions, . . . 558 
 
 currents, ..... 558 
 
 Electricity, 519 
 
 detection of, . . 529 
 
 measurement of, . 529 
 
 applications of, . . . 542 
 
 from galvanic action, . . 547 
 
 Electro-magnetic multiplier, . 536 
 
 Electrometer, Henly's, . . . 529 
 
 Bennett's, ' ; .'.:... . 530 
 
 Coulomb's, . '.-' "f . 533 
 
 Lane's, . . . . . 534 
 
 Calorific, .... 534 
 
 Electrodes, 558 
 
 Electrolytes, 558 
 
 Electrolysis, ..... 558 
 
 Electrotype, . .. . - .-., . 567 
 
 Electro-metallurgy, . . . 566 
 
 copying by, .... 567 
 
 plating by, .... 567 
 
 moulds for, .... 567 
 
 non-conducting substances, . 568 
 
 solutions, .... 569 
 
 arrangement of batteries for, . 571 
 
 Electroscopes, .... 529 
 
 voltaic pile, .... 532 
 
 Electrophorus, .... 527 
 
 Etching on glass, .... 79 
 
 Eudiometer, 542 
 
 use of, 543 
 
 Ure's, . . . . .'545 
 
 Hare's aqueous, . . . 563 
 
 Evaporating vessels, . . 463 
 
 Evaporation, ..... 463 
 
 spontaneous, . 464 
 
 in vacuo, 465 
 
 by heat in open air, . . . 467 
 
 liquid baths, . . . 467 
 
 steam, .... 467 
 
 heated air, . . . 468 
 
 over sandbath, . . . 468 
 naked fire, . . .471 
 
 F. 
 
 Fahrenheit's thermometer, . . 208 
 Faraday's table for estimating the 
 amount of watery vapor in 
 
 gases, 127 
 
 voltameter, .... 560 
 
 decomposition tube, . . 561 
 
 Filter stands, .... 262 
 
 bath, . . . . 479 
 
 Riouffe'a, . . . .512 
 
 Filters ignition of, . . 287 
 
 drying of, .... 479 
 
 paper, 498 
 
 cutting of, . . . . 499 
 
 folding of, . . . .502 
 
 cloth, . . . . . 509 
 
 frames for. . '. . .510 
 
 washing of, .... 513 
 
 Filtering paper, German, . 498 
 
622 
 
 INDEX. 
 
 Filtering paper, Swedish, . 
 
 . 499 
 
 
 
 purification of, . 
 
 . 499 
 
 light, . 
 
 . 561 
 
 
 497, 505 
 
 battery, Smee's, . . 
 
 . 553 
 
 through paper . . , 
 of oils and viscous liquids, 
 through cloths, . . 
 pulverulent matter, . 
 
 . 498 
 . 508 
 . 509 
 . 511 
 
 Daniell's, . - ,^i 
 Grove's, . 
 Bunsen's, y , ?& 
 
 . 551 
 . 554 
 . 555 
 . 547 
 
 
 . 508 
 
 decomposition by, . . 
 
 . 558 
 
 .of corrosive liquids, . 
 volatile " 
 Fire lute, .... 
 Flame ftlowpipe, ... 
 
 . 511 
 
 . 512 
 . 383 
 
 . 578 
 
 reduction by, . 
 Galvanometer, 
 Schweigger's, . . . 
 
 . 561 
 . 535 
 . 536 
 . 537 
 
 Flasks, Florence, . 
 sublimation in, 
 
 . 346 
 . 317 
 
 . 448 
 
 differential, 
 Weygandt's, . 
 Gas chamber, ... 
 
 . 539 
 . 539 
 55 
 
 
 . 381 
 
 
 64, 240 
 
 
 . 303 
 
 apparatus Kent's, . . 
 
 . 241 
 
 Florence flasks, 
 Florentine receivers, * f <& 
 
 . 346 
 . 339 
 
 manufacture of, 
 
 . 242 
 
 . 242 
 
 Fluids, measuring of, . -f i 
 spec grav of, . . . 
 
 . 194 
 . 139 
 
 grease, 
 
 . 241 
 
 66 
 
 Flux, black, .... 
 Fluxes, ignition with, . 
 non-metallic, ... 
 
 . 294 
 . 290 
 . 291 
 
 Beale's, . 
 Hoffman's, 
 
 . 246 
 . 247 
 . 250 
 
 
 . 297 
 
 hydrogen apparatus, 
 
 . 348 
 
 Freezing mixtures, 
 tables of, 
 French crucibles, 
 Fuel for furnaces . . 
 
 . 271 
 
 . 274 
 . 279 
 . 228 
 
 jars, 
 regulator, Kemp's, . 
 burner for blowpipe, 
 
 . 368 
 
 . 481 
 . 576 
 304, 360 
 
 Funnels, filtering, 
 
 . 498 
 500 
 
 collected over water, 
 
 . 365 
 . 372 
 
 porcelain, 
 
 . 501 
 . 501 
 
 mercury, . 
 receivers, . . . 
 
 . 369 
 
 . 350 
 
 stands for, 
 Furnace-room, . V 
 
 . 504 
 . 29 
 . 229 
 
 illuminating, . 
 distillation of, . 
 Gases, weighing of, . 
 
 . 240 
 . 340 
 . 126 
 
 
 . 223 
 
 spec. grav. of t ... 
 
 . 147 
 
 
 . 225 
 
 measurement of, . 
 
 . 202 
 
 
 30, 218 
 
 collection of, . . 
 
 . 350 
 
 
 . 219 
 
 generation of, . * 
 
 . 354 
 
 
 . 220 
 
 absorption of, ... 
 
 . 356 
 
 universal, 
 
 . 221 
 . 222 
 
 transfer of, ... 
 
 . 372 
 . 424 
 
 reverberatory, . 
 
 . 223 
 
 . 225 
 
 desiccation of, . 
 Gasometers, .... 
 
 . 488 
 . 360 
 
 Aiken's 
 
 . 225 
 
 Peov's 
 
 . 361 
 
 assay or cupel, . 
 
 . 225 
 226 
 
 mercurial, 
 D^ville's, 
 
 . 363 
 . 365 
 
 
 . 227 
 
 Gay Lussac's barometer, 
 
 . 399 
 
 furniture for, 
 gas, .... 
 
 . 228 
 '66, 246 
 . 568 
 
 Generator, steam, . 
 German filtering paper, . 
 Glassware, cleansing of, . 
 
 . 35 
 . 498 
 . 77 
 
 Fusing-points ... 
 
 . 286 
 
 
 . 326 
 
 Fusion -. . 
 
 277 285 
 
 
 . 499 
 
 crystallization by, 
 by electrical action, 
 
 . 472 
 . 562 
 
 cement for, . " # 
 etching upon, 
 
 . 383 
 . 79 
 69, 601 
 
 
 . 277 
 
 implements for . . 
 
 . 604 
 
 G. 
 
 Gahn's blowpipe, . 
 
 . 574 
 . 252 
 
 tubes, . . . 
 blower's lamp, 
 bulbs, blown, 
 cutting of, 
 tubes, bent, 
 cemented, . . 
 
 . 307 
 . 601 
 609, 610 
 . 601 
 . 606 
 . 606 
 
 Galvanic action, . . . 
 
 . 547 
 
 
 . 608 
 
 batteries, 
 arrangement of, 
 power of, . 
 
 . 548 
 . 562 
 . 562 
 
 divided, 
 drawn out, 
 Glass tubes, edges of, rounded, 
 
 605, 608 
 . 607 
 . 605 
 
INDEX. 
 
 623 
 
 Gmelin's washing-bottle, . . 516 
 
 Gold solutions for electro-gilding, . 569 
 Goodall's grinding and levigating 
 
 apparatus, 94 
 
 Graduation of vessels, . . . 194 
 
 Granulation, ..... 474 
 
 Gravimeter, 141 
 
 Grove's battery, .... 554 
 
 Gutta percha, for moulds, . . 568 
 
 H. 
 
 Hare's compound blowpipe, 
 
 eudiometer, 
 
 calorimeter, . . .; . 
 Harkort's blowpipe lamp, 
 Harris's machine sieve, . 
 Hart's gas furnace, 
 Hassler's barometer, 
 
 . 251 
 . 563 
 . 564 
 . 576 
 . 97 
 . 250 
 . 394 
 
 Heating by baths, . . . .264 
 
 steam, ..... 265 
 
 in close vessels, . . . 377 
 
 by hot air, .... 468 
 
 Heat from galvanism, . . . 561 
 
 Henley's electrometer, . . . 529 
 
 Henry's subliming apparatus, . 320 
 
 Hessian crucibles, . . . 278 
 
 Herapath's tables for testing by blow- 
 
 pipe, 596-600 
 
 Hewitt's machine mortar, . . 93 
 
 Hoffman's gas furnace, . . . 247 
 
 Hoods for carrying off noxious vapors, 34 
 
 for retorts, . . . .334 
 
 Hydrogen, reduction by, . . 302 
 
 gas apparatus, .... 348 
 
 Hydrometers, . . . . 140 
 
 Baume's 14 
 
 Hydrostatic balance, . . .131 
 Hydro-sublimation, . . . .320 
 
 Igneous fusion, . .27 
 Ignition with fluxes, . . . 290 
 of filters, . . . . .287 
 in vapors, ; ' . 290 
 
 604 
 299 
 84 
 304 
 303 
 304 
 
 Implements for glass-blowing, 
 Incineration, .... 
 Index rerum, . 
 India rubber connecting tubes, 
 
 for joints, .... 
 
 gas bags, 
 
 Infusion, 437 
 
 Ink for labels, 80 
 
 Iron crucibles, . . . .281 
 
 tubes, 309 
 
 retorts, , ' ,. . . .33 
 
 cement, 382 
 
 Jacket for crucibles, . . . 234 
 
 Jars, gas, 368 
 
 Leyden, . , . .523 
 
 K. 
 
 Kater's balance, . . . .108 
 
 Kathode, . 
 
 Kemp's generating jar, 
 
 gas regulator, . 
 Kent's furnace, 
 
 gas apparatus, . 
 
 Labelling of bottles, 
 Labels etched, 
 
 paste for, .... 
 
 ink for, .... 
 
 varnish for, 
 Laboratory, arrangement of, . 
 
 heating of, 
 
 ventilation, 
 
 plan of, . . 
 
 materials for, . 
 
 jack 
 
 water for, . 
 
 cleansing apparatus, 
 
 costume, . 
 
 record, . . . >" 
 Lamp, alcohol, 
 
 Danger's, 
 
 glassblower's, . 
 
 oil, . . . 
 
 pyroxylic spirit, 
 
 Berzelius's, 
 
 supports, 
 
 Luhme's, 
 
 Rose's, .... 
 
 Russian, .... 
 
 Deville's blast, 
 
 Nunn's " . 
 
 table gas, .... 
 
 tongs, . . . :. # 
 
 heating oven, . 
 Lane's electrometer, 
 Leslie's differential thermometer 
 LetorelPs gas receiver, . 
 Levigation, .... 
 
 by machinery, . , .4^1* 
 
 by decantation, . 
 Leyden jars, .... 
 Liebig's furnace, . . 
 
 combustion-tube, . :.../ 
 
 drying-tube, . . -4.*;* 
 Lime cement, .... 
 Liquids, weighing of, 
 
 measurement of, 
 
 distillation of volatile, 
 
 distillation of, . 
 
 solution of, 
 
 evaporation of, . 
 
 desiccation of, . . . 
 
 filtration of corrosive, 
 volatile, 
 
 electrical decomposition of, 
 Lutes 
 
 mode of applying, . 
 
 lime, .... 
 
 plastic, .... 
 
 resinous, . 
 
 iron, v 
 
 fire, . . 
 
 Local action in batteries, 
 London crucibles, . 
 
 64 
 
 548 
 347 
 481 
 222 
 241 
 
 . 76 
 
 79 
 
 80 
 
 80 
 
 80 
 
 17 
 
 19 
 
 19 
 
 21 
 
 21 
 
 36 
 
 56 
 
 58 
 
 84 
 
 84 
 
 231 
 
 601 
 
 601 
 
 231 
 
 231 
 
 233 
 
 235 
 
 236 
 
 237 
 
 237 
 
 238 
 
 239 
 
 240 
 
 232 
 
 230 
 
 534 
 
 211 
 
 356 
 
 98 
 
 94 
 
 494 
 
 523 
 
 227 
 
 307 
 
 489 
 
 382 
 
 124 
 
 194 
 
 329 
 
 335 
 
 423 
 
 463 
 
 488 
 
 511 
 
 512 
 
 558 
 
 380 
 
 385 
 
 382 
 
 382 
 
 382 
 
 383 
 
 383 
 
 549 
 
 278 
 
624 
 
 INDEX. 
 
 M. 
 
 Maceration, . . . 
 
 Machine for slicing, . 
 
 crushing, . . . . 
 Magnets, .... 
 Marsh's arsenic apparatus, . 
 Measures and measuring, 
 
 and weights, tables of, . 
 
 equivalent weights of, 
 Measurement of fluids, . 
 
 gases, .... 
 
 temperature, . . . 
 
 electricity, . . 
 Melloni's thermo-multiplicator, 
 Mercurial gasometer, 
 Mercury trough, . . . 
 
 bath, .... 
 Metallic baths, 
 
 fluxes, . . 
 
 tubes, .... 
 
 retorts, .... 
 
 crucibles, 
 Metals, pulverization of, 
 
 electrical relation of, 
 
 conducting power of, 
 Micro-chemical distillation, . 
 Mineral cases, % . . 
 Minimeter, Alsop's, . .=-.> 
 Mint balance, . . . 
 
 Mitscherlich's blowpipe, 
 Mixtures, freezing, >..}**! 
 Mohr's dropping-tube, . . 
 
 digester, .... 
 Morland's barometer, . . 
 Mortars, .,. 
 
 iron, ' ?, + . 
 
 steel, V . 
 
 agate 
 
 porcelain, . 
 
 Wedgwood, 
 
 glass, .... 
 Muffles, 
 
 Taylor's, * v . & 
 
 . 437 
 
 . 87 
 
 . 88 
 
 . 589 
 
 . 345 
 
 . 194 
 614, 617 
 
 . 199 
 
 . 194 
 
 . 202 
 
 . 205 
 
 . 529 
 
 . 211 
 
 . 363 
 
 . 369 
 
 . 270 
 
 . 270 
 
 . 297 
 
 . 309 
 
 . 331 
 
 . 281 
 
 . 91 
 
 . 548 
 
 . 549 
 
 . 330 
 
 . 25 
 
 . 201 
 
 . 102 
 
 . 575 
 
 . 271 
 
 . 201 
 
 . 444 
 
 . 400 
 
 . 89 
 
 . 90 
 
 . 91 
 
 . 92 
 
 . 93 
 
 . 93 
 
 . 89 
 
 . 225 
 
 . 313 
 
 N. 
 
 Newman's barometer, . . 
 Nicholson's areometer, . . 
 Nobili's galvanometer, . . 
 Nunn's blast lamp, . . 
 
 0. 
 
 . 389 
 . 134 
 . 537 
 . 239 
 
 . 241 
 
 baths, . , . 
 filtration of, ... 
 
 . 270 
 . 508 
 . 576 
 
 Office, arrangement of, . 
 furniture, 
 Operating table, 
 
 . 25 
 . 27 
 61, 67 
 61 
 
 Ores, pulverization of, 
 Organic analysis, 
 furnace for, . . , 
 
 . 91 
 . 226 
 . 227 
 
 Oxygen apparatus, . . 252 
 
 O xy hydrogen blowpipe, . .. . 251 
 
 P. 
 
 Paper filtering, * . . 498 
 Paste for labels, . . . .80 
 Papin's digester, , . .441 
 Pepy's gasometer, ... 361 
 
 Pipettes, .... 199, 495 
 
 Plaster of Paris lute, . ,' . 382 
 Plastic lute, . . . . .382 
 Platform balance, . . . .114 
 Platina crucibles, . 282 
 
 retorts, 331 
 
 Platinized silver, .... 553 
 Pneumatic pump, .... 70 
 
 trough, 365 
 
 Poles of a battery, . . . .547 
 Porcelain crucibles, . . . 279 
 
 tubes, 308 
 
 retorts, 333 
 
 funnels, ... . . .500 
 
 Porphyrization, . .95 
 
 Potash, bulbs, ... .353 
 
 Precipitation, ... . 491 
 
 Precipitates, desiccation of, . 479 
 
 washing of, . 493 
 
 Precipitating, directions for, . 492 
 
 vessels for, . . . 492 
 
 by galvanism, . . . 570 
 
 Pressure, digestion under, . 441 
 
 Pump, air, 70 
 
 Purification of crystals, . . . 475 
 Putnam's curtain spring rollers, . 22 
 
 Pulverization, 89 
 
 of metals, 99 
 
 Pyrometer, . . . , .205 
 
 Q. 
 
 Quantity of the galvanic fluid, 
 
 R. 
 
 551 
 
 Reaction, chemical, crystallization 
 
 by, 477 
 
 Reagents, 80 
 
 blowpipe, . . . 590, 594 
 
 Reaumur's thermometer . . 208 
 
 Receivers, . . . 336, 327 
 
 Florentine, . . 339 
 
 gas, ... . 350 
 
 Lettorel's, . . . 356 
 
 Record of analyses, . . . 84 
 
 Rectification, . . , 340 
 
 Reduction by chemical means, . 99 
 
 charcoal, 301 
 
 hydrogen, . . . . 302 
 
 apparatus, . . . . 303 
 
 tubes, 306 
 
 Register, barometer, . . . 407 
 
 Regnault's " ... 407 
 Resinous lutes, . . . .382 
 
 Retorts, sublimation in, . . . 318 
 
INDEX. 
 
 625 
 
 Retorts, distillation in, . 
 
 glass, . 
 
 platma, . 
 
 earthenware, . 
 
 iron, 
 
 porcelain, . 
 
 lutes for, .... 
 Reverberatory furnace, . 
 RioufTe's filtering apparatus, 
 Ritchie's compound blowpipe, 
 Roasting, . 
 
 in tubes, .... 
 Rose's combustion tube, 
 
 lamp, . 
 Robinson's balance, 
 Rosin gas, .... 
 Rubber of electrical machine. 
 Russia lamp, 
 
 S. 
 
 Safety tubes, ..... 
 Saline baths, ..... 
 Salts, solubility of, . . . 419, 
 
 table of, ..... 
 Sand bath, . .'J'- , 31, 66, 
 
 evaporation by, 
 Saturation, ..... 
 
 Schweigger's galvanometer, . 
 Schuster's alkalimeter, . 
 Sefstrom's blast furnace, 
 Separating funnels, 
 Sieves, . . 'v 
 Sifting, ...... 
 
 Silver crucibles, 
 
 solutions for electro-plating, . 
 
 platinized, . . . . 
 
 Sink, the, ..... 
 
 Slicing, ...... 
 
 Smee's battery, .... 
 
 Solids, weighing of, ... 
 
 spec. grav. of, . . . . 
 
 solution of, .... 
 
 desiccation of, ... 
 
 Solubility of salts, . 
 Solutions, saturated, boiling-point of, 
 
 decolorization of, . . 
 
 Solution, ...... 
 
 means of facilitating, 
 
 of solids, ..... 
 liquids, ..... 
 
 325 
 326 
 331 
 333 
 332 
 333 
 384 
 223 
 512 
 255 
 299 
 307 
 307 
 237 
 108 
 242 
 522 
 237 
 
 , 
 
 by digestion, .. 
 
 under pressure, 
 
 boiling, .. 
 in test-tubes, .. 
 
 beakers, .. 
 
 flasks, .. 
 
 capsules, .. 
 by steam, .. 
 
 displacement, . 
 in volatile solvents, . 
 
 close vessels, 
 Cadet's mode of, . 
 under pressure of steam, 
 Duvoir's apparatus, 
 crystallization by, . 
 
 359 
 268 
 426 
 426 
 271 
 468 
 418 
 536 
 200 
 225 
 501 
 
 97 
 
 95 
 281 
 570 
 553 
 
 56 
 
 86 
 553 
 122 
 129 
 421 
 478 
 426 
 269 
 511 
 417 
 420 
 421 
 423 
 424 
 439 
 441 
 445 
 446 
 447 
 448 
 449 
 450 
 452 
 454 
 457 
 458 
 461 
 462 
 473 
 
 40 
 
 Sonnenschein's blast-lamp, . . 257 
 Specific gravity, . . . .129 
 
 bottles, 132 
 
 by areometer, . . .134, 143 
 Alexander's method, . 135 
 
 of fluids 139 
 
 by the flask, . . . .139 
 hydrometers, . . 140, 144 
 
 Sravimeter, . . . 141 
 am's method, . . 146 
 
 of gases 147 
 
 vapors, . . . .150 
 
 tables of, 154 
 
 Spirit lamps, , 232 
 
 Spritz bottles, 
 
 Spontaneous evaporation, 
 
 Steam generator, 
 series, 
 
 bath, . . , 
 distillation by, . 
 joints, cement for, . 
 solution by, 
 evaporation by, 
 
 Stills, 
 
 506 
 . 464 
 . 35 
 . 43 
 . 265 
 . 373 
 . 384 
 450, 461 
 . 467 
 48,51,322 
 
 furnaces for 52 
 
 Stock for laboratory, ... 83 
 Stoneware retorts, .... 333 
 Sublimation, .... 315, 472 
 
 in tubes 316 
 
 flasks, 317 
 
 retorts, ; . . . .318 
 shallow vessels, . . .319 
 by Henry's process, . . 320 
 
 lire's, 320 
 
 Sulphur moulds, .... 568 
 Supports lor lamps, . .235, 259 
 
 retorts, 260 
 
 universal, 260 
 
 Gahn's, 261 
 
 for funnels, .... 504 
 Swedish filtering paper, . . , 499 
 Sympiesometer, Adie's, , . 402 
 
 Syphon, 495 
 
 use of 496 
 
 Coffee's, 496 
 
 barometer, .... 389 
 eudiometer, . 546 
 
 T. 
 
 Table, operating, . . . 61, 67 
 blowpipe, .. . . 69, 594, 602 
 glass blowers' .... 69 
 for balance, . . . .115 
 
 Table furnace, .... 220 
 
 Tables, Faraday's, for estimating 
 watery vapor in gases, . 127 
 
 .for Baume's hydrometer, . 145 
 of spec, grav., ... 154 
 
 chemical, .... 191 
 
 Tables of measures, . . 199, 615 
 freezing mixtures, . . 274 
 thermometrical equivalents, 213 
 solubility of salts, . . 426 
 boiling-point of saturated solu- 
 tions, 269 
 
 electrical relations of the metals, 548 
 
626 
 
 INDEX. 
 
 Tables of electrical conducting power 
 
 of metals, . . . . 549 
 of weights and measures, 614,617 
 Herapath's, for testing by 
 
 blowpipe, . . . 596, 600 
 
 blowpipe, .... 594, 602 
 
 Tasker's water furnace, . . 19 
 
 Temperature, measurement of, . 205 
 
 Test-tube racks, .... 58 
 
 stands, 63 
 
 case, 79 
 
 series, 80 
 
 bottles, 83 
 
 papers, . . . . .88 
 
 tubes, solution in, . . . 446 
 
 Testing by blowpipe, . . ..595 
 
 Thermometers, . , . .207 
 
 Celsius, 208 
 
 Fahrenheit, . . . .208 
 
 Reaumur, . . . .209 
 
 differential, . . . .211 
 
 Thermometrical equivalents, . 213 
 
 Thermometrograph, . . .211 
 
 Thermomultiplicator, . . .211 
 
 Thermostat, Kemp's, . . .481 
 
 Tongs, furnace, . . . . 229 
 
 lamp, 232 
 
 cupel, 312 
 
 Tool chest, 60 
 
 Tralle's balance, . . . .113 
 Transfer of gases, .... 372 
 
 Trituration, 92 
 
 Torsion balance, Coulomb's, . . 533 
 
 Troughs, pneumatic, . . . 365 
 
 water, .... . 366 
 
 mercury, 369 
 
 Troughton's barometer, . . .391 
 
 Tubes, porcelain 308 
 
 metallic, 309 
 
 combustion, .... 307 
 
 reduction, 307 
 
 flexible, . . . .- . 303 
 graduation of, . . . .197 
 
 iron 309 
 
 platina, 310 
 
 safety, 359 
 
 test, 446 
 
 drying, . . . 484, 489, 490 
 chloride of calcium, . . . 489 
 
 U, 490 
 
 Faraday's decomposition, . 560 
 glass, attachments to, . . 619 
 
 bent, 606 
 
 cemented 606 
 
 closed 608 
 
 drawn out, .... 607 
 divided, . . . 605,608 
 edges of, rounded, . . 605 
 . funnel, blown, . . . -611 
 Welter's blown, . . 611 
 
 U. 
 
 U tube, 
 
 490 
 
 Universal furnace, . . . .221 
 
 Kent's, . . . .222 
 
 Ure's subliming apparatus, . . 320 
 
 eudiometer, . . . 545 
 
 V. 
 
 Vacuo, distillation in, 
 
 evaporation in, . 
 
 desiccation in, . 
 Vapors, noxious, 
 
 spec, gravity of, 
 
 ignition in, 
 Varnish for labels, . 
 Ventilation of laboratory 
 Vessels exhausted of air, . 
 
 graduated, 
 
 Viscous liquids, filtration of, 
 Volatile liquids, distillation of 
 filtration of, 
 
 solvents, . 
 Voltaic pile, .. .. 
 
 electroscope, . 
 
 W. 
 
 . 374 
 
 . 465 
 
 . 487 
 
 . 34 
 
 . 150 
 
 . 290 
 
 . 80 
 19, 34 
 70, 126 
 
 . 194 
 
 . 508 
 
 . 339 
 
 . 512 
 
 . 454 
 
 . 547 
 
 . 532 
 
 Washing precipitates, . . . 493 
 by decantation, . . 494, 513 
 
 bottles 507, 513 
 
 filters, 513 
 
 Water-bath, ..... 266 
 trough, . . , . . 366 
 barometer, .... 402 
 decomposition of, . . 559 
 
 mother, 474 
 
 gas collected over, . . . 365 
 
 Wedgwood's pyrometer, . . 205 
 
 Weighing, 120 
 
 solids, 
 liquids 
 
 122 
 124 
 126 
 124 
 123 
 
 corrosive substances, 
 hygrometric, " 
 
 Weights, 116 
 
 adjustment of, .... 117 
 divisions, . . . . .117 
 materials for, , . . .117 
 
 testing of, 118 
 
 Weights and measures, tables of, 614, 617 
 Wind furnaces, . . . .219 
 Wheel barometer, .... 387 
 Weygandt's galvanometer, . . 539 
 Wire for batteries, .... 557 
 Wollaston's battery, . . . 549 
 barometer, .... 407 
 Wolfie's bottle, . . . .351 
 
 Z. 
 
 Zinc for batteries, 
 local action in, 
 amalgamating, 
 
 548 
 549 
 549 
 
 THE END. 
 
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