UC-NRLF 
 
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REESE LIBRARY 
 
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 OF THE 
 
 UNIVERSITY OF CALIFORNIA 
 
 Deceived ^ 
 Accessions No.^,. Shelf JVo. 
 
ELECTRO-CHEMICAL 
 ANALYSIS. 
 
 SMITH. 
 
RlCHTER'S 
 
 AUTHORIZED TRANSLATIONS. 
 
 BY EDGAR F. SMITH, F.C.S., M.D., PH.D., 
 
 Professor of Chemistry, University of Pennsylvania ; Member of Chemical Societies 
 of Berlin and Paris, etc. 
 
 INORGANIC CHEMISTRY. A Text-book for Students. Third 
 
 American, from the Fifth German Edition, thoroughly revised, and 
 
 in many parts rewritten. With 89 Illustrations and a Colored Plate 
 
 of Spectra. I2mo. Cloth, $2.00 
 
 THE CHEMISTRY OF THE CARBON COMPOUNDS, or 
 
 Organic Chemistry. A Text-book for Students. Translated from 
 the Fourth German Edition. Illustrated. 
 
 Cloth, $3.00; Leather, $3.50 
 
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 giving a high technical education, as well as those who aim to 
 give but a groundwork in the science of chemistry ; this shows 
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 mendations and examination prices, will be sent free. 
 
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 1O12 WALNUT STREET, -' PHILADELPHIA. 
 
ELECTRO-CHEMICAL 
 ANALYSIS. 
 
 BY 
 
 EDGAR F. SMITH, 
 
 M 
 
 PROFESSOR OF ANALYTICAL CHEMISTRY, UNIVERSITY OF PENNSYLVANIA. 
 
 WITH TWENTY-FIVE ILLUSTRATIONS. 
 
 PHILADELPHIA: 
 
 P. BLAKISTON, SON & CO., 
 
 1012 WALNUT STREET. 
 1890. 
 
Copyright, 1890, by P. BLAKISTON, SON & Co. 
 
 PRES8 OF WM. F. FELL <* CO., 
 
 1220-24 SANSOM STREET, 
 
 PHILADELPHIA. 
 
PREFACE 
 
 In preparing this little volume the author has had 
 constantly in view the needs of a large class of stu- 
 dents of analytical chemistry desirous of becoming 
 acquainted with the methods of quantitative analysis 
 by electrolysis ; these are daily acquiring greater im- 
 portance, and being introduced and applied wherever 
 possible. 
 
 The larger texts devoted to analysis have omitted 
 electrolysis from their pages, thus rendering its special 
 treatment necessary and desirable. 
 
 The plan adopted in the following pages in present- 
 ing this subject has been to give a brief introduction 
 upon the behavior of the current toward the different 
 acids and salts, a short description of the various 
 sources of the electric energy; its control and measure- 
 ment ; after which follow a condensed history of the 
 introduction of the current into chemical analysis, and 
 sections relating to the determination and separation 
 of metals, as well as the oxidations possible by means 
 of the electric agent. 
 
 In using this book as a guide, the student is ear- 
 nestly recommended to perform the determinations of 
 each metal as indicated in the text. The details have 
 
 v 
 
VI PREFACE. 
 
 been made sufficiently full, and clear enough, it is 
 hoped, for the most inexperienced analyst. Additional 
 skill and valuable experience are acquired with each 
 trial, so that, when the section treating of separations 
 is reached, the work there outlined will be performed 
 without difficulty. Before commencing the determina- 
 tion of any one metal read, if possible, its literature. 
 
 The methods of determination and separation given 
 preference are not those of any one individual, but 
 have been selected from all sources after an experience 
 of many years, care being taken to present only those 
 which actual tests have shown to be reliable and trust- 
 worthy. 
 
 It has not been considered advisable to include an 
 outlined electrolytic analysis of alloys and minerals 
 in the text, inasmuch as the experience gained in per- 
 forming the analyses already described there will have 
 given the analyst such a fund of experience that the 
 course to be pursued in special cases will readily sug- 
 gest itself. 
 
 The author would here acknowledge his indebted- 
 ness to the various writers on electrolysis, whose 
 publications he has freely used, to the editors of the 
 different journals consulted, to friends who have made 
 kindly suggestions, and to his brother, Dr. Allen J. 
 Smith, who prepared all the drawings from which the 
 illustrations of the text were made. S. 
 
 University of Pen n a., 
 Philadelphia, Sept., 1890. 
 
TABLE OF CONTENTS. 
 
 PAGB 
 
 INTRODUCTION, 9-10 
 
 ACTION OF THE ELECTRIC CURRENT UPON ACIDS AND SALTS, 10-13 
 
 OHM, VOLT, AMPERE, ; . 13-14 
 
 SOURCES OF ELECTRIC CURRENT 
 
 Grenet Battery, Leclanche Cell, Daniell Cell, Meidinger 
 Cell, Crowfoot Cell, Bunsen and Grove Batteries, 
 Magneto-Electric Machines, Storage Cells, Ther- 
 mopile, 14-25 
 
 REDUCTION OF THE CURRENT 
 
 Rheostat, Resistance Frame, 25-29 
 
 MEASURING CURRENTS 
 
 Voltameter, Amperemeter, 29-32 
 
 HISTORICAL SKETCH, .* . 32-46 
 
 SPECIAL PART. 
 
 1. DETERMINATIONS OF METALS, 47-89 
 
 2. SEPARATION OF METALS, 89-108 
 
 3. OXIDATIONS BY MEANS OF THE ELECTRIC CURRENT, . 108-113 
 INDEX, 115 
 
 Vll 
 
IO ELECTRO-CHEMICAL ANALYSIS. 
 
 determinations where the ordinary methods yield un- 
 satisfactory results. This statement is readily con- 
 firmed on recalling the gravimetric methods usually 
 employed in the estimation of copper, mercury, cad- 
 mium, bismuth, tin, etc., etc. That this assertion may 
 be the conviction of every student of analysis, the 
 writer would call attention first to the course of the 
 current in solutions of some of the more frequently 
 occurring salts; after which will follow a brief account 
 of the various modes of obtaining the electric current, 
 how it may be measured and how controlled. Finally, 
 all the metals, which have been studied electrolytically, 
 will be taken up in detail, and their various determina- 
 tions will be followed by a sufficient number of separa- 
 tions to show, at least in part, how widely the electro- 
 lytic method of analysis may be applied. 
 
 i. ACTION OF THE ELECTRIC CURRENT UPON 
 ACIDS AND SALTS. 
 
 At the At the 
 
 Pole. + Pole. 
 
 Hydrochloric acid -(- the current = Hydrogen -|- Chlorine. 
 Copper chloride -f- " " = Cu + C1 2 . 
 
 Zinc chloride -f " " = Zn + C1 2 . 
 
 Nitric acid -f " " = H -f NO 2 -f O. 
 
 In this last case the hydrogen further acts upon more 
 nitric acid and produces ammonia (NH 3 ) and water. 
 
 Lead nitrate -f the current = Pb -f NO 2 + O. 
 
 The oxygen liberated here attacks a second molecule of 
 
ACTION OF CURRENT UPON ACIDS AND SALTS. I I 
 
 lead nitrate, and produces lead peroxide, Pb(NO 3 ) 2 -j- 
 O 2 = PbO 2 , which deposits upon the positive elec- 
 trode. 
 
 At the At the 
 Pole. + Pole. 
 
 Copper nitrate -}- the current = Cu -)- (NO 3 ) 2 . 
 Sulphuric acid + " " = H 2 -f SO 4 . 
 
 Secondary changes frequently occur in these de- 
 compositions ; thus, in the last example the SO 4 reacts 
 with the water present: SO 4 + H 2 O == H 2 SO 4 -f O, 
 the oxygen going to the positive electrode. In the 
 electrolysis of copper sulphate, which is analogous to 
 sulphuric acid, secondary changes also occur. 
 
 At the At the 
 Pole. + Pole. 
 
 Potassium sulphate -|- the current = K 2 -f- SO 4 
 
 In this decomposition the liberated potassium acts 
 upon water, with the liberation of hydrogen and the 
 formation of potassium hydroxide. 
 
 Bourgoin observed the following changes with 
 formic, acetic and oxalic acids, and their salts : 
 
 I. Formic Acid. The decomposition may be ex- 
 pressed in two equations 
 
 (a) CH 2 2 = H + (CHO -f O). 
 
 Pole + Pole 
 
 (6) 2(CHO -f- O) = CH 2 2 + C0 2 . 
 
 The decomposition of sodium formate yields carbon 
 dioxide and formic acid at the anode, and hydrogen 
 and sodium hydroxide at the cathode. 
 
12 ELECTRO-CHEMICAL ANALYSIS. 
 
 2. Acetic Acid. The electrolysis of the dilute acid 
 affords ^hydrogen at the negative electrode, and at 
 the positive electrode a mixture of oxygen, carbon 
 dioxide and a small quantity of carbon monoxide. 
 
 3 Oxalic Acid. The electrolysis of this acid with 
 a current obtained from four Bunsen cells gave de- 
 compositions which may be expressed as follows : 
 
 C 2 H 2 O 4 .2H 2 O -j- current = 3H 2 -f 2CO 2 -f O 2 ; 
 Pole. +Pole. 
 
 the oxygen reacts upon additional acid : 
 
 2C 2 H 2 O 4 + 2H 2 O -f O 2 = 4CO 2 + 4H 2 O, 
 
 so that the final products are pure carbon dioxide at 
 the positive electrode and hydrogen at the opposite 
 pole. The decomposition of potassium oxalate may 
 be formulated in the following way : 
 
 Pole. + Pole. 
 
 the liberated metal and the carbon dioxide then react 
 further : 
 
 2H 2 O -f K 2 = 2KOH -f H 2 and 2CO 2 -f 2KOH = 2KHCO 3 . 
 
 When exposed to the same influence ammonium 
 oxalate yields hydrogen at the negative electrode, and 
 hydrogen ammonium carbonate at the positive elec- 
 trode. The latter compound further breaks down 
 into ammonia and carbon dioxide. 
 
 Succinic acid is electrolysed with difficulty. In its 
 decomposition the products which have generally been 
 
OHM, VOLT AND AMPERE. 13 
 
 observed at the positive electrode were oxygen and 
 the two oxides of carbon. By electrolysing sodium 
 succinate Kekule obtained hydrogen at the cathode, 
 and carbon dioxide and ethylene at the anode. 
 Tartaric acid -f the current gave at 
 
 Pole. + Pole. 
 
 hydrogen acetic acid, carbon dioxide, 
 
 carbon monoxide and oxygen ; 
 
 while with potassium tartrate the products were hy- 
 drogen and potassium at the cathode and acid potas- 
 sium tartrate, carbon dioxide, carbon monoxide and 
 oxygen at the anode. An alkaline solution of potas- 
 sium tartrate gave hydrogen at the cathode and at the 
 anode, acetic acid, the oxides of carbon, oxygen and 
 ethane (C 2 H 6 ). 
 
 The above examples will suffice to indicate the na- 
 ture of the decomposition due to the current; they 
 will assist very materially in understanding the 
 changes occurring in ordinary electrolytic analyses. 
 For further particulars in this direction, consult 
 Tommasi's Traite Theorique et pratique d' Electrochimie. 
 
 2. OHM, VOLT AND AMPERE. 
 
 These terms may be defined as follows : 
 The ohm is the unit of resistance. Its value is rep- 
 resented by a column of mercury I sq. mm. in cross- 
 section, and 106.2 cm. in length at the temperature 
 
14 ELECTRO-CHEMICAL ANALYSIS. 
 
 The volt is the unit of electromotive force (E. M. F.). 
 It is the E. M. F. which gives a current of one ampere 
 through a resistance of one ohm. 
 
 The ampere is the unit of current. It is the 
 current which, under an electromotive force of one 
 volt, flows through a circuit offering a resistance 
 of one ohm. 
 
 V 
 
 A-. 
 O 
 
 3. SOURCES OF THE ELECTRIC CURRENT. 
 
 The electric energy required for quantitative analy- 
 sis has been variously furnished by batteries of well- 
 known types, magneto-electric machines, dynamos, 
 thermo-piles, and electrical accumulators or storage 
 cells. A brief description of some of these may be 
 properly introduced here. 
 
 The Grenet cell or Bichromate Battery (Fig. i) con- 
 sists of two plates of carbon (K) and one of zinc (Z), 
 movable by means of the handle, a. This is a con- 
 venient arrangement, as it allows of easy interruption 
 of the current. The liquid to be used in this cell con- 
 sists of potassium bichromate (i lb.), strong sulphuric 
 acid (2 Ibs.), and water (12 Ibs.). In mixing these, the 
 probable chemical change is : 
 
 K,Cr 2 7 + 7 H 2 S0 4 = 2Cr0 3 + K,SO 4 + H 2 O + 6H 2 SO 4 . 
 
SOURCES OF THE ELECTRIC CURRENT. 15 
 
 The chemical action in the cell, when the current 
 passes, may be expressed by the equation : 
 
 2 CrO 3 + 6H 2 SO 4 
 
 -f 
 
 4 -f- 6H 2 O. 
 
 The writer found four cells of this type (capacity 
 two quarts) very serviceable in the electrolysis of solu- 
 tions of cadmium, uranium, molybdenum and other 
 
 FIG. i. 
 
 metals. No disagreeable fumes arise from cells of 
 this class. The electromotive force is about two 
 volts, and the internal resistance low. The Grenet 
 cell loses in intensity when used for long periods, but 
 regains its value when it has remained out of action 
 for some time. 
 
i6 
 
 ELECTRO-CHEMICAL ANALYSIS. 
 
 Leclanche cell (Figs. 2 and 3). Two forms of this 
 cell are in use. In the first, to the left of the 
 figure, there is a zinc rod, immersed in a solution 
 of ammonium chloride, and a carbon plate inside 
 a porous cup, tightly packed with a mixture of 
 manganese dioxide and broken gas carbon. The 
 
 FIG. 2. 
 
 FIG. 3. 
 
 porous cup is only intended to hold the mixture 
 in position. There is but one liquid, and that a 
 strong solution of ammonium chloride. The E. M. F. 
 of this cell equals 1.47 volts; it decreases rapidly 
 when sending strong currents. It is inferior to the 
 Daniell cell when a steady current is desired for 
 a long period. 
 
SOURCES OF THE ELECTRIC CURRENT. 1 7 
 
 The chemical action in cells of this kind Ayrton 
 expresses as follows : 
 
 (Before sending the current) 
 
 kC+ I (MnO 2 ) + m (NH 4 C1) + n Zn. 
 (After sending the current) 
 
 k C + (/- 2)(Mn0 2 ) + (m 2)(NH 4 C1) + (Mn. 2 O 3 ) + 2(NH 3 ) 
 + (H 2 0) + (ZnCl 2 ) + (n - i)(Zn). 
 
 The letters k, /, m, n represent indefinite amounts 
 of the acting substances. 
 
 In the modified Leclanche cell the porous cup is 
 not needed, as compressed prisms of manganese diox- 
 ide, gas carbon and shellac are used around the 
 carbon plate. 
 
 The Daniell cell (Fig. 4) consists of a glass jar, the 
 porous cup T, and a cylinder of zinc (Z), the negative 
 pole. Outside of the porous cup is the sheet-copper 
 cylinder K. The zinc is the negative electrode, and 
 the copper the positive electrode. The zinc stands in 
 dilute sulphuric acid (i : 20), and the copper in copper 
 sulphate. Zinc sulphate often replaces the sulphuric 
 acid. The chemical action in the cell is probably : 
 
 k (Cu) -f / (CuSO 4 ). /Before sending\ .2 m (ZnSO*) + n (Zn). 
 
 \ the current. / *S 
 
 o. 
 
 (k + i)(Cu) + (/ - i)(CuS0 4 ). /After sendingN (m + i)(ZnSO 4 + ( - i)(Zn). 
 V the current. ) (Ayrton). 
 
 PU 
 
 The E. M. F. of this cell is about 1.07. The Meid- 
 inger (Fig. 5) and Crowfoot (Fig. 6) cells are modifica- 
 tions of the Daniell, and very serviceable in electrolytic 
 
i8 
 
 ELECTRO-CHEMICAL ANALYSIS. 
 FIG. 4. 
 
SOURCES OF THE ELECTRIC CURRENT. \g 
 
 work when currents of low intensity are desired. In 
 the sketch of the Meidinger cell, G is a large glass 
 jar; g t a small glass vessel, in which stands the copper 
 cylinder, K (-f- P). Z ( P) is a cylinder of zinc. 
 B contains the supply of copper sulphate crystals. 
 
 The current from either of these batteries remains 
 quite constant for long periods. The cells themselves 
 do not require much attention. Haifa dozen of either 
 of these forms will do nearly all the electrolytic work 
 of an ordinary laboratory. The "Crowfoot" form 
 can be readily and cheaply prepared. Rejected acid 
 bottles, after removing the neck and upper portions, 
 answer well as jars. 
 
 If currents of greater E. M. F. are required, the 
 Bunsen (Fig. 7) or Grove cell (Fig. 8) should be used. 
 * In the former there is zinc in dilute sulphuric acid, or 
 a mixture of potassium bichromate and sulphuric acid, 
 and a carbon plate in a cup of nitric acid. It is a less 
 expensive cell than the Grove, as platinum is not 
 employed. It is not so readily handled, and con- 
 sumes more nitric acid. Its electromotive force is 
 somewhat less than that of the Grove form. In the 
 latter there is a strip of* platinum (P) in concentrated 
 nitric acid (in the porous cup, x)~ and zinc (ZZ) in 
 dilute sulphuric acid (one pint acid and ten pints 
 water). The E. M. F. is 1.93 volts. When acting, 
 X 2 O 4 is set free ; this can be in a measure suppressed 
 by adding ammonium chloride to the nitric acid. 
 The chemical changes occurring in the Bunsen and 
 
20 
 
 ELECTRO-CHEMICAL ANALYSIS. 
 
 Grove cells are very similar. Ayrton expresses them 
 as follows : 
 
 (Befor^ current is sent) 
 
 A(Pt) +/(HN0 3 ). 
 (After sending current) 
 * (Pt) + (/ 2 )(HN0 8 ) + (N 2 O 4 ) + ( 2 H 2 0). 
 
 FIG. 7. 
 
 The internal resistance of the Grove cell is small. 
 To obtain good results both the Bunsen and Grove 
 cells require constant attention. 
 
SOURCES OF THE ELECTRIC CURRENT. 21 
 
 In amalgamating the zincs in any of the preceding 
 batteries, first allow them to remain o,ver night in very 
 dilute hydrochloric acid, then immerse in mercury, 
 and with a wet cloth rub the latter into the metal. 
 This should be done once a week, when the cells are 
 in daily use. For further information upon batteries, 
 consult Ayrton's Practical Electricity. 
 
 Magneto-electric machines, and dynamos have been 
 used to some extent in electrolytic decompositions, 
 but a detailed description of their construction will 
 not be given. This may be found in Classen's 
 Analysis by Electrolysis, pp. 21-35 (Herrick's transla- 
 tion). 
 
 Thermo-piles have also been used to furnish cur- 
 rents for electrolytic work. Their use has been 
 objected to upon the ground that the currents afforded 
 by them are rarely strong enough for the greater num- 
 ber of determinations and separations, and again they 
 are easily broken and difficult to repair. The forms 
 generally met with are those recommended by Cla- 
 mond and Noe. 
 
 The Clamond thermo-pile is pictured in Fig. 9. I 
 is a perspective view of the same ; 2 represents a ver- 
 tical section, and 3 a basal section, showing the bars 
 and armatures. The elements consist of bars of a zinc 
 and antimony alloy, and a strip of sheet-iron. These 
 are arranged in circles, as indicated in 3 ; they are 
 placed one above the other. In 3, B represents the 
 bars of zinc and antimony alloy, while the tinned 
 
22 
 
 ELECTRO-CHEMICAL ANALYSIS. 
 
SOURCES OF THE ELECTRIC CURRENT. 23 
 
 sheet-iron plates are marked L. The sheet-iron serves 
 to conduct the current from one element to the other; 
 hence, these strips rest upon the bars B. Heat ex- 
 pands the latter, and in consequence renders the con- 
 tact more intimate. The single elements, as well as 
 the circles of elements, are separated from each other 
 by plates of asbestos (see r in 2). The cylinder itself 
 consists of a series of such circles. The welded points 
 of the bars are all directed to the centre of the cylin- 
 der. The gas flames are prevented from coming in 
 immediate contact with them by the asbestos lining 
 of the cylinder. As gas is employed to furnish the 
 necessary heat, in the middle of the cylinder will be 
 observed a clay tube (A) provided with apertures (2 
 and 3). The gas enters through the Giroud regulator 
 C (i and 2), which makes it possible to maintain a 
 uniform temperature, and a constant current. From 
 C it is conducted to A, through 7", into which air is 
 admitted by suitable apertures. The mixture of air 
 and gas burns at the openings in A. Additional 
 air is supplied through D. Light the gas jets from 
 above, after removing the cover. The poles of each 
 ring of elements end in binding screws, thus en- 
 abling the operator to connect any number of them, 
 depending upon the external resistance (Z. f. a. Ch., 
 
 15, 334)- 
 
 When in excellent condition, thermo-piles are said 
 to yield a current equivalent to 400-500 c.c. oxy- 
 hydrogen gas per hour. Those persons who may 
 
24 ELECTRO-CHEMICAL ANALYSIS. 
 
 desire fuller information upon this type of battery are 
 referred to the following 
 
 LITERATURE: Z. f. a. Ch., 14, 350; 17, 205; Ding. p. Jr., 224, 
 267; Z. f. a. Ch., 18, 457; 25, 539. 
 
 The best source of electric energy, for electrolytic 
 purposes, is unquestionably the storage cell (Fig. 10). 
 
 FIG. 10. 
 
 The illustration represents a cell of the Julien type. 
 It contains nineteen alternating plates of lead and lead 
 dioxide. Each of these is five and three-fourths inches 
 square. The exciting liquid is sulphuric acid of sp. 
 gr. 1.2. The E. M. F. of such a cell is a little more 
 than two volts. The current is very constant. 
 
 Cells of this kind can be charged from primary 
 
REDUCTION OF THE CURRENT. 25 
 
 batteries, or better, by means of a dynamo. In any 
 community where electric lighting is employed it is 
 possible to have the charging done at little expense, 
 and in factories where there is always sufficient power, 
 a small dynamo could easily be arranged for this pur- 
 pose, so that almost any number of cells could be kept 
 in condition for work. The iron estimations required 
 by any establishment could be rapidly and accurately 
 made with three cells of this type ; little attention 
 would be demanded from the chemist. While storage 
 cells can be used in almost every description of elec- 
 trolysis, there are a great many cases where economy 
 would suggest the use of the cheaper batteries, e.g., 
 the Crowfoot. Consult the following literature upon 
 storage batteries: 
 
 Proceedings of the Royal Society, June 2Oth, 1889; Transactions of 
 Am. Inst. Mining Engineers (Electrical Accumulators, Salom), Feb., 
 1890. 
 
 Having thus briefly described the more important 
 current-producers, the means of regulating the current 
 may be next considered. 
 
 4. REDUCTION OF THE CURRENT. 
 When a battery gives a current that generates 10 
 c.c. oxy-hydrogen gas per minute, and work is to be 
 done which can easily be performed by an expenditure 
 of energy not exceeding 3 c.c. oxy-hydrogen gas per 
 minute, it will become necessary to reduce the strong 
 c 
 
26 
 
 ELECTRO-CHEMICAL ANALYSIS. 
 
 current. Persons acquainted with practical physics 
 will promptly suggest the resistance coils found in 
 physical laboratories, as suitable for this purpose. 
 They are, on the whole, quite satisfactory, and have 
 been thus utilized, although simpler and more con- 
 venient current-reducers have made their appearance 
 
 FIG. ii. 
 
 in recent years. A few of these later appliances may 
 be mentioned : 
 
 i. The current may be sent through a solution 
 (saturated) of zinc sulphate, contained in a large glass 
 cylinder, about 22 cm. long and 8.5 cm. in diameter. 
 In one experiment the current is passed from a to b 
 (Fig. T i), and in the next from b to a. " The rod b, 
 
REDUCTION OF THE CURRENT. 2/ 
 
 with one zinc pole, is pushed toward the zinc pole a, 
 until the current reaches the desired strength." It is 
 well to amalgamate the zincs from time to time. We 
 are indebted for this piece of apparatus to Classen, 
 who has also described another simple rheostat (Fig. 
 12) (Ben, 21, 359). In this apparatus the current 
 enters at a, travels the German silver resistance ;/, and 
 returns through b to the battery. In the performance 
 of electrolytic depositions the platinum vessels, serv- 
 
 ing as negative electrodes, may be connected with any 
 one of the binding-posts from 1-20. This makes it 
 possible for the analyst to execute eight different de- 
 terminations at the same time. To show the influence 
 of this apparatus, a current from five Bunsen cells, 
 generating 68 c.c. oxy-hydrogen gas per minute, was 
 allowed to act upon copper solutions contained in six 
 vessels. The current at binding-post I was found to 
 be equal to 3.75 amperes; at 2, it equaled 2.617 
 
 
28 
 
 ELECTRO-CHEMICAL ANALYSIS. 
 
 P^JG. 13. 
 
MEASURING CURRENTS. 29 
 
 amperes; at 3, 2.085 amperes; at 4, 1.911 amperes, 
 etc., until at 20 it was only 0.098 of an ampere. 
 
 To better understand these figures it should be re- 
 membered that an ampere equals 10.436 c.c. oxy- 
 hydrogen gas per minute, or it is equivalent to a 
 current which will precipitate 19.69 mg. of metallic 
 copper, or 67.1 mg. of metallic silver in one minute. 
 
 For a larger form of apparatus somewhat similar to 
 that described above see Ber., 17, 1787. 
 
 The writer has for some time employed a much 
 simpler current-reducer, which has the advantage of 
 cheapness and ready construction to recommend it. 
 It consists of a light wooden parallelogram, about six 
 feet in length. Extending from end to end, on both 
 sides, is a light iron wire, measuring in all about 500 
 feet (Fig. 13). With the binding-posts at a and b, and 
 a simple clamp, it is possible to throw in almost any 
 resistance that may be required. It answers all prac- 
 tical purposes. 
 
 LITERATURE. v. Klobukow, Jr. f. pkt. Ch., 37, 375; 40, 121. 
 
 5. MEASURING CURRENTS, VOLTAMETER, 
 AMPEREMETER. 
 
 In every analysis by electrolysis it is advisable that 
 the strength of the acting current should be known. 
 The simplest and most convenient apparatus for this 
 purpose is the Bunsen voltameter (Fig. 14). The 
 inner tube a, containing sulphuric acid of sp. gr. 1.22, 
 
3O ELECTRO-CHEMICAL ANALYSIS. 
 
 stands in a large cylinder of water to cool it. The 
 liberated hydrogen and oxygen are collected over 
 water in the eudiometer tube R ; p and p r are platinum 
 electrodes. In all accurate experiments the volume 
 of gas should always be reduced to o and 760 mm. 
 
 FIG. 14. 
 
 pressure. Some chemists substitute a galvanometer 
 (tangent or sine) for the voltameter. The deflection 
 of the needle by the current measures the strength of 
 the latter. " In order to express in terms of chemical 
 action the deflection of the needle, it is placed in the 
 
MEASURING CURRENTS. 3! 
 
 same current with a voltameter, and the deviation of 
 the needle is observed, as well as the volume of elec- 
 trolytic gas (reduced to o and 760 mm. pressure), 
 which is produced in a minute. Placing the volume 
 equal to v, the quotient ~ - gives the standard value 
 for the galvanometer. If this standard value is de- 
 
 FIG. 15. 
 
 noted by R, the strength I, of a current, which pro- 
 duces the deviation a, is I = R tan. a." 
 
 The writer has found the amperemeter of Kohl- 
 rausch (Fig. 15) very satisfactory, especially in cases 
 where strong currents are employed. In this instru- 
 ment the current travels through an insulated wire 
 
32 ELECTRO-CHEMICAL ANALYSIS. 
 
 surrounding a bar of soft iron. The latter, in its 
 magnetized state, attracts the needle C, attached to a 
 spiral. C moves over a graduated face (in amperes), 
 and its deflection gives at once the strength of the 
 current in amperes. 
 
 In electrolytic work of any kind it is advisable 
 that the apparatus intended to measure the current 
 strength should be in the circuit during the entire 
 decomposition, for it is only in this way that we can 
 expect to effect separations without encountering un- 
 pleasant difficulties. It is necessary to know just what 
 energy is required, and then to so regulate the current 
 that the same is approximately maintained throughout 
 the entire determination. 
 
 Before taking up the description of the details to 
 be observed in the electrolytic precipitation of indi- 
 vidual metals, it may not be uninteresting to briefly 
 trace the history of the introduction of the electric 
 current into chemical analysis. 
 
 6. HISTORICAL. 
 
 Although the early years of this century show con- 
 siderable activity in electrical studies, the efforts were 
 mainly directed to the solution of the physical side of 
 electrolysis. To Gaultier de Claubry probably be- 
 longs the credit of having first (1850) applied the cur- 
 rent to the detection of metals when in solution. His 
 efforts were wholly directed to the isolation of metals 
 
HISTORICAL. 33 
 
 from poisons by depositing the same upon plates of 
 platinum. When the precipitation was considered 
 finished the plates were removed, carefully washed, 
 and the deposited metals brought into solution with 
 nitric acid, and there tested for and identified by the 
 usual course of analysis. The current was evidently 
 very feeble, as the time recorded as necessary for the 
 deposition varied from ten to twelve hours. Gaultier 
 considered this method reliable in all instances, but 
 especially recommends it for the separation of copper 
 from bread. In testing for zinc he employed a strip 
 of tin as anode, but states that a platinum plate will 
 answer as well. 
 
 In Graham-Otto's Lehrbuch der Chemie (1857) it 
 is stated that the oxygen developed at the positive 
 electrode readily induces the formation of peroxides ; 
 . . . that lead and manganese peroxides are de- 
 posited, from solutions of these metals, upon the posi- 
 tive electrode of the battery ; . . . that the point of 
 a platinum wire, when attached to the anode of a cell, 
 is therefore a delicate means of testing for manganese 
 and lead. In the same text the oxidizing power of 
 the anode is nicely shown by the following simple ex- 
 periment : A piece of iron, in connection with the 
 positive electrode of the battery, is introduced into a 
 V-shaped glass tube containing a concentrated solu- 
 tion of potassium hydroxide, while a platinum wire 
 running from the negative electrode projects into the 
 other limb of the vessel. In a short time ferric acid 
 
34 ELECTRO-CHEMICAL ANALYSIS. 
 
 appears around the anode, and is recognized by its 
 color. 
 
 C. Despretz (1857) described the decomposition of 
 certain salts by means of the electric current, and 
 remarked that, while operating with solutions of the 
 acetates of copper and lead, he expected both metals 
 would be deposited upon the negative pole, and was 
 much surprised to find that the lead separated as oxide 
 upon the anode at the same time that the copper 
 was deposited upon the cathode. The results were 
 the same when experiments were conducted with 
 the nitrates and pure acetates. With manganese no 
 deposition took place upon the negative electrode, but 
 a black oxide appeared at the opposite pole. Potas- 
 sium antimonyl tartrate gave a crystalline metallic 
 deposit of antimony at the cathode, and upon the anode 
 a yellowish-red coating, supposed to be anhydrous 
 antimonic acid. Bismuth nitrate yielded a reddish- 
 brown deposit at the positive electrode. Despretz 
 concludes his paper by stating that although the facts 
 were few in number, yet they were new in so far as 
 they concerned lead, antimony and manganese ; and, 
 furthermore, that the separation of copper from lead 
 by the current was almost perfectly complete. 
 
 Three years later (1860) Charles L. Bloxam recom- 
 mended the process of Gaultier for the detection of 
 metals in organic mixtures, although it may not be 
 improper to add that Smee (1851), in his work on 
 electrometallurgy, asserts that Morton was the first 
 
HISTORICAL. 35 
 
 person to employ the electric current for the isolation 
 of metals from poisonous mixtures. However this 
 may be, the fact remains that Bloxam did use the 
 current quite extensively for this purpose, and while 
 he claims no quantitative results for the method, the 
 apparatus employed by him and his subsequent work 
 in this direction deserve great credit. 
 
 To detect arsenic electrolytically Bloxam made use 
 of a glass jar, four cubic inches in capacity, closed 
 below by parchment, which was tightly secured by 
 means of a thin platinum wire. In the neck of the 
 jar was a large cork, through which passed a glass 
 tube bent at a right angle. This tube was intended 
 to serve as a means of escape for the gases liberated 
 within the jar. The platinum wire from the negative 
 electrode was also held in position by the cork. The 
 portion of the wire within the jar was attached to a 
 platinum plate dipping into the arsenical mixture con- 
 taining dilute sulphuric acid. The jar with its contents 
 stood in a wide beaker, filled with water, into which 
 dipped the positive electrode of the battery. Under 
 the influence of the current, metals like antimony, 
 copper, mercury and bismuth separated upon the 
 platinum plate of the negative electrode, while arsine 
 was liberated and escaped through the exit-tube into 
 some suitable absorbing liquid. To ascertain what 
 metal or metals had separated upon the cathode, 
 the plate attached thereto was removed, after the 
 interruption of the current, and treated with hot 
 
36 ELECTRO-CHEMICAL ANALYSIS. 
 
 ammonium sulphide. Upon evaporating this solution 
 an orange-colored spot remained if antimony had been 
 previously present. If a metallic deposit continued 
 to adhere to the foil the latter was acted upon by 
 nitric acid to effect the solution of the remaining 
 metals. 
 
 J. Nickles (1862) precipitated silver with the current 
 obtained from a zinc-copper couple. The positive 
 electrode consisted of a piece of graphite, taken from 
 a lead-pencil, while a thin, bright copper wire consti- 
 tuted the negative electrode. The silver separated 
 upon this. The current was very feeble, for hydrogen 
 was not liberated at the cathode. Nickles also sug- 
 gested the reduction of large quantities of silver from 
 the solution of its cyanide by this means. To obtain 
 the silver he advised using a cylindrical cathode con- 
 structed from some readily fusible alloy, so that after 
 the reduction was finished, the other metals might be 
 easily melted out and leave a silver plate. Copper, 
 lead, bismuth and antimony were separated electro- 
 lytically, by Nickles, from textiles. 
 
 In 1862 A. "C. and E. Becquerel resumed their 
 electro-chemical investigations, first begun some thirty 
 years previously. Their experiments seem to have 
 been aimed chiefly toward the reduction of metallic 
 solutions upon a large scale, caring not for the quanti- 
 tative estimation of metals, but seeking rather a rapid 
 and satisfactory technical isolation process. 
 
 Wohler (1868) found that when palladium was 
 
HISTORICAL. 37 
 
 made the positive conductor of two Bunsen cells, and 
 placed in water acidulated with sulphuric acid, it 
 immediately became covered with alternating, bright, 
 steel-like colors. He regarded the coating as palladium 
 dioxide since it liberated chlorine when treated with 
 hydrochloric acid, and carbon dioxide when warmed 
 with oxalic acid. Black amorphous metal separated 
 at the cathode. Its quantity was slight. Under 
 similar conditions lead also yields the brown dioxide, 
 and the same may be said of thallium. Osmium, in 
 its ordinary porous form, at once becomes osmic acid. 
 When caustic alkali is substituted for the acid the 
 liquid rapidly assumes a deep yellow color, while a 
 thin deposit of metal appears upon the cathode. 
 Ruthenium behaves similarly when applied in the 
 form of powder. Osmium-iridium, a compound de- 
 composed with difficulty under ordinary circum- 
 stances, immediately passes into solution when brought 
 in contact with the positive electrode of a battery 
 placed in a solution of sodium hydroxide, and imparts 
 a yellow color to the alkaline liquid. A black 
 deposit of metal slowly makes its appearance upon 
 the negative pole. 
 
 The experiments, thus far described, are qualitative 
 in their results. The first notice of the quantitative 
 estimation of metals electrolytically was that of Gibbs 
 (1864), when he published the results he had obtained 
 with copper and nickel. Luckow, in alluding to this 
 work a year later (1865), says : " I take the liberty to 
 
38 ELECTRO-CHEMICAL ANALYSIS. 
 
 observe that so far as the determination of copper is 
 concerned, I estimated that metal in this manner 
 more than twenty years ago, and as early as 1860 
 employed the electric current for the deposition of 
 copper quantitatively in various analyses." It was 
 Luckow who proposed the name Elektro-Metall Ana- 
 lyse for this new method of quantitative analysis. 
 According to this writer the current may be applied 
 as follows : 
 
 1. To dissolve metals and alloys in acids by which 
 they would not be affected unaided by the electric 
 current. 
 
 2. To detect metals like manganese and lead 
 (silver, nickel, cobalt) ; separating them in the form 
 of peroxides ; also manganese as permanganic acid. 
 
 ' 3. To separate various metals, e.g., copper and 
 manganese from zinc, iron, cobalt and nickel. 
 
 4. To deposit and estimate metals quantitatively, 
 in acid, alkaline and neutral solutions. 
 
 5. For various reductions, e.g., silver chloride, basic 
 bismuth chloride and lead sulphate, in order that the 
 metals in them may be determined. To reduce chro- 
 mic acid to oxide, e. g., potassium bichromate acidu- 
 lated with dilute sulphuric acid. 
 
 These applications embrace nearly all that has since 
 been accomplished by the aid of the current. In the 
 same article to which Luckow calls attention to the 
 facts recorded above, he describes minutely the method 
 
HISTORICAL. 39 
 
 pursued by him in the precipitation of metals. Refer- 
 ence to these early experiments will show with what 
 care and accuracy every detail was worked out. 
 Luckow also announced " that all the lead contained 
 in solution was deposited as peroxide upon the posi- 
 tive electrode, and might be determined from the 
 increased weight of the latter." This observation 
 was fully confirmed by Hampe and, later, by W. 
 C. May. 
 
 Wrighfson (1876) called attention to the fact that 
 if solutions of copper were electrolysed in the presence 
 of other metals, the latter greatly influenced the sepa- 
 ration of the former. For example, with copper and 
 antimony, the deposition of the copper was always 
 incomplete when the antimony equaled one-fourth to 
 two-thirds the quantity of the former. Notwithstand- 
 ing, a complete separation of the two metals can be 
 effected when the quantity of the antimony is small. 
 A somewhat similar behavior was noticed with other 
 metals. The deposition of cadmium, zinc, cobalt and 
 nickel was apparently not satisfactory. 
 
 Lecoq de Boisbaudran (1877) electrolysed the potas- 
 sium hydroxide solution of the metal gallium, using 
 six Bunsen elements with 20-30 c.c. of the concen- 
 trated liquid. The deposited metal was readily de- 
 tached when the negative electrode was immersed in 
 cold water, and bent slightly. 
 
 The unpromising behavior of zinc solutions, ob- 
 served by Wrightson, was fortunately overcome by 
 
40 ELECTRO-CHEMICAL ANALYSIS. 
 
 Parodi and Mascazzini (1877), who employed a solu- 
 tion of the sulphate, to which was added an excess of 
 ammonium acetate. Lead was also deposited in a 
 compact form from an alkaline tartrate solution of this 
 metal in the presence of an alkaline acetate. 
 
 After Luckow's experiments upon manganese, little 
 attention appears to have been given this metal until 
 Riche (1878) published his results. While confirming 
 the observations of Luckow, he discovered that manga- 
 nese was not only completely precipitated from the 
 solution of its sulphate, but also from that of the 
 nitrate, thus rendering possible an electrolytic sepa- 
 ration of manganese from copper, nickel, cobalt, zinc, 
 magnesium, the alkaline earth and the alkali metals. 
 Riche recommended that the deposited dioxide be 
 carefully dried, converted by ignition into the proto- 
 sesquioxide and weighed as such. According to this 
 chemist, the one-millionth of a gram of manganese, 
 when exposed to the action of the current, gave a 
 distinct rose-red color, perceptible even when diluted 
 tenfold. 
 
 In zinc depositions Riche gave preference to a 
 solution of zinc- ammonium acetate containing free 
 acetic acid. 
 
 Luckow was the first to mention that the current 
 caused mercury to separate in a metallic form, from 
 acid solutions, upon the negative electrode. F. W. 
 Clarke (1878) used a mercuric chloride solution, 
 feebly acidulated with sulphuric acid, for this purpose. 
 
HISTORICAL. 41 
 
 The deposition was made in a platinum dish, using 
 six Bunsen cells. Mercurous chloride was at first pre- 
 cipitated, but it was gradually reduced to the metallic 
 form. J. B. Hannay (1873) had previously recom- 
 mended precipitating this metal from solutions of 
 mercuric sulphate, but gave no results. 
 
 Clarke, also, gave some attention to cadmium ; his 
 results, however, were not satisfactory. A few 
 months later the writer (1878) succeeded in depositing 
 cadmium completely and in a very compact form 
 from solutions of its acetate. Upon this behavior 
 Yver (1880) based his separation of cadmium from 
 zinc. Furthermore, the writer found (1880) that the 
 deposition of cadmium could be made from solutions 
 of its sulphate, contrary to an earlier observation of 
 Wrightson. At the same time copper was completely 
 separated from cadmium by electrolysing their solu- 
 tion in the presence of free nitric acid. 
 
 A very successful determination of both zinc and 
 cadmium was published by Beilstein and Jawein in 
 1879. They employed for this purpose solutions of 
 the double cyanides. 
 
 Heinrich Fresenius and Bergmann (1880) found 
 that the electrolysis of nickel and cobalt solutions 
 succeeded best in the presence of an excess of free 
 ammonia and ammonium sulphate. 
 
 Their experience with silver demonstrated that 
 the best results could be obtained with solutions 
 
42 ELECTRO-CHEMICAL ANALYSIS. 
 
 containing free nitric acid, and by the employment 
 of weak currents. 
 
 The writer showed (1880) that if uranium acetate 
 solutions were electrolysed the uranium was com- 
 pletely precipitated as a hydrated protosesquioxide ; 
 and further, that molybdenum could be deposited as 
 hydrated sesquioxide from warm solutions of am- 
 monium molybdate in the presence of free ammonia. 
 Very promising indications were obtained with salts 
 of tungsten, vanadium and cerium. 
 
 In a more recent (1880) communication from 
 Luckow, to whom we are indebted for much that is 
 valuable in electrolysis, is given a full description of 
 his observations in this field of analysis, from which 
 the following condensed account is taken. While it 
 relates more particularly to the qualitative behavior 
 of various compounds, its importance demands careful 
 study. 
 
 When the current is conducted through an acid 
 solution of potassium chromate the chromic acid is 
 reduced to oxide, whereas, if the solution of the oxide 
 in caustic potash be subjected to a like treatment 
 potassium chromate is produced. Arsenic and 
 arsenious acid behave similarly. The same is true 
 also of the soluble ferro- and ferri-cyanides and nitric 
 acid. In the presence of sulphuric acid, ferric and 
 uranic oxides are reduced to lower states of oxidation. 
 Sulphates result in the electrolysis of the alkaline 
 
HISTORICAL. 43 
 
 sulphites, hyposulphites and sulphides, and carbonates 
 from the alkaline organic salts. In short, the current 
 has a reducing action in acid solutions, and the 
 opposite effect in those that are alkaline. In the 
 electrolysis of solutions of hydrogen chloride, bromide, 
 iodide, cyanide, ferro- and ferri-cyanide and sulphide, 
 the hydrogen separates at the electro-negative pole, 
 and the electro-negative constituents at the positive 
 electrode. Cyanogen sustains a more thorough de- 
 composition, the final products being carbon dioxide 
 and ammonia. In the electrolysis of ferro- and ferri- 
 cyanogen, Prussian blue separates at the positive 
 electrode. In dilute chloride solutions hypochlorous 
 acid is the only product, whereas chlorine is also 
 present in concentrated solutions. In alkaline chloride 
 solutions chlorates are produced as soon as the liquid 
 becomes alkaline. In the iodides and bromides iodine 
 and bromine separate at the positive electrode, while 
 bromates and iodates are formed when metals of the 
 first two groups are present. Potassium cyanide is 
 converted into potassium and ammonium carbonates. 
 Concentrated nitric acid is reduced to nitrous acid ; 
 however, when its specific gravity equals 1.2, this does 
 not occur, at least not when a feeble current is used. 
 Dilute nitric acid alone, or even in the presence of 
 sulphuric acid, is not reduced to ammonia. If, how- 
 ever, dilute nitric acid be present in a copper sulphate 
 solution undergoing electrolysis, copper will separate 
 upon the negative electrode and ammonium sulphate 
 
44 ELECTRO-CHEMICAL ANALYSIS. 
 
 will be formed. Solutions of nitrates, containing .sul- 
 phuric acid, behave analogously. Phosphoric acid 
 sustains no change. Silicic acid separates as a white 
 mass, and boric acid, in crystals uniting to arborescent 
 groups, at the positive electrode. 
 
 In the Ber. d. d. chem. Gesellschaft for 1881 (Vol. 
 14, 1622), Classen and v. Reiss presented the first of 
 a series of papers upon electrolytic subjects, which 
 continued through subsequent issues of this publica- 
 tion. Their early work was devoted to the precipita- 
 tion of metals from solutions of their double oxalates. 
 They also elaborated excellent methods for antimony 
 and tin. Many very serviceable forms of apparatus, 
 intended for electrolytic work, were devised and de- 
 scribed by them, and it must be conceded that through 
 the activity of the Aachen School electrolysis acquired 
 more importance in the eyes of the chemical public 
 than it ever before possessed. The details of the 
 more important methods proposed by Classen and 
 his co-laborers will receive due mention under the 
 respective metals. 
 
 At the same time with and quite independently of 
 Classen, Reinhardt and Ihle proposed the double oxa- 
 lates for the estimation of zinc electrolytically ; and 
 in this connection it may not be improper to mention 
 that as early as 1879, two years prior to the publica- 
 tion of Classen's first communication, Parodi and Mas- 
 cazzini (Gazetta chimica italiana, Vol. 8) announced 
 that antimony and iron could be deposited completely 
 
HISTORICAL. 45 
 
 and in compact form by electrolysing the solutions 
 of the sulpho-salts of the former and the chloride 
 of the lattter in the presence of acid ammonium 
 oxalate. 
 
 In 1883, Gibbs recommended placing solutions of 
 mercury, tin and cobalt in a beaker glass, on the 
 bottom of which was placed a layer of mercury, 
 which served as the negative electrode. Knowing 
 the combined weight of the beaker and mercury, the 
 increased weight, after precipitation and removal of 
 the liquid, will give the quantity of metal under 
 examination. This method is not applicable in the 
 case of antimony and arsenic. 
 
 Three years later (1886) Luckow recommended a 
 very similar procedure for the estimation of zinc. 
 
 Moore (1886) also published new data upon the 
 estimation of iron, cobalt, nickel, manganese, etc., full 
 notice of which will appear under these metals. 
 
 The most recent publications relating to electrolysis 
 are those of Brand, who succeeded in effecting sepa- 
 rations by utilizing solutions of the pyrophosphates of 
 different metals, and those of Smith and Frankel, who 
 have made an extended study of the double cyanides, 
 and found thereby a number of very convenient 
 methods of separation heretofore unrecorded. The 
 results are given in detail in the following pages. 
 
 The preceding paragraphs give a brief outline of 
 what has been accomplished in the field of analysis by 
 
46 ELECTRO-CHEMICAL ANALYSIS. 
 
 electrolysis ; for further information consult the fol- 
 lowing 
 
 LITERATURE. Jahrb., 1850, 602; C. r., 45, 449; Jr. f. pkt. Ch., 73, 
 79; Chem. Soc. Quart. Journ., 13, 12; Jahrb., 1862, 610; Ann., 124, 
 131; C. r., 55, 18; Ann., 146, 375; Z. f. a. Ch., 3, 334; Ding. p. Jr. 
 (1865), 231 ; Z. f. a. Ch., 8, 23; n, I, 9; 13, 183; Am. Jr. Sc. and 
 Ar. (3d ser.), 6, 255; Z. f. a. Ch., 15, 297; Ber., 10, 1098; Annales 
 de Ch. et de Phy., 1878; Am. Jr. Sc. and Ar., 16, 200; Am. Phil. Soc. 
 Pr., 1878; Z. f. a. Ch., 15, 303; Am. Ch. Jr., 2, 41; Berg-Hutt. Z., 
 37, 41; Z. f. a. Ch., 19, i, 314, 324; Am. Ch. Jr., i, 341; B. s. Ch. 
 Paris, 34, 18; Ber., 12, 1446; 14, 1622, 2771; 17, 1611, 2467, 2931; 
 18, 168, 1104, 1787; 19, 323; 21, 359, 2892, 2900; Jr. f. pkt. Ch., 
 24, 193; Z. f. a. Ch., 18, 588; 22, 558; 25, 113; Chem. News, 28, 
 581 ; 53, 209. And the following will be found worthy of careful 
 study: Ann., 36, 32; 94, i; Z. f. a. Ch., 19, I ; Berg-Hutt. Z., 42, 
 377; Z. f. a. Ch., 22, 485. 
 
SPECIAL PART. 
 
 i. DETERMINATION OF THE DIFFER- 
 ENT METALS. 
 
 COPPER. 
 
 LITERATURE. Gibbs, Z. f. a. Ch., 3, 334; Boisbaudran, B. s. 
 Ch., Paris, 1867, p. 468; Merrick, Am. Ch., 2, 136; Wrightson, 
 Z. f. a Ch., 15, 299; Her pin, Z. f. a. Ch., 15, 335 ; Moniteur Scien- 
 tifique [3 ser.], 5,41 ; Ohl, Z. f. a. Ch., 18, 523; Classen, Ber., 14, 
 1622, 1627 ; Classen and v. Reiss, Z. f. a. Ch., 24, 246; 25, 113; 
 Riche, Z. f. a. Ch., 21, 116; M akin tosh , Am. Ch. Jr., 3, 354; 
 Rudorff, Ber., 21, 3050; Luckow, Z. f. a. Ch., 8, 23. 
 
 Dissolve 19.6 grams of pure copper sulphate in 
 water, and dilute to I litre. Place 50 c.c. of this solu- 
 tion (= 0.25 gram of metallic copper) in a clean plati- 
 num dish, previously weighed. Connect the dish with 
 a battery, whose current is sufficiently strong to effect 
 the complete precipitation of the copper in the course 
 of ten or twelve hours. The apparatus may be 
 arranged as in the accompanying sketch (Fig. 16), 
 page 48. 
 
 A is an ordinary filter stand, upon the base of which 
 is fixed a binding-post, x, to which is attached a heavy 
 copper ring for the support of the platinum vessel. It 
 
 47 
 
4 8 
 
 ELECTRO-CHEMICAL ANALYSIS. 
 
DETERMINATION OF METALS COPPER. 49 
 
 is in connection with the negative electrode of the bat- 
 tery. The arm, y t has been shortened, and at its 
 extremity there is a second binding-screw,/; the lat- 
 ter holds the positive pole (a heavy platinum wire 
 bent into a flat spiral at its lower end), and the copper 
 wire from the anode of the battery (the copper plate 
 in a " Crowfoot " cell). It will be noticed that the 
 current passes through the vessel, B (a Bunsen volta- 
 meter), in which acidulated water is undergoing de- 
 composition, the resulting gases being collected in d. 
 Their volume serves to measure the strength of the 
 acting current. Copper is very readily precipitated 
 from solutions containing free nitric or sulphuric acid. 
 Hydrochloric acid should never be present. 
 
 Having arranged the apparatus as just described, 
 add 9-10 drops of concentrated nitric acid to the solu- 
 tion of the electrolyte ; cover the vessel with a perfo- 
 rated watch crystal during the decomposition. To 
 ascertain when the metal has been completely precipi- 
 tated, add water to the dish ; this will expose a clean, 
 platinum surface, and if in the course of half an hour 
 no copper appears upon it, the deposition may be con- 
 sidered as finished. Or, a drop of the liquid may be 
 removed, and brought in contact with a drop of 
 ammonium hydroxide or hydrogen sulphide, when, if 
 a blue coloration or black precipitate is not produced, 
 the deposition can be considered ended. 
 
 As the precipitation has been made in an acid solu- 
 tion, the current should not be interrupted until the 
 
50 ELECTRO-CHEMICAL ANALYSIS. 
 
 acid liquid has been removed, for in many cases the 
 brief period during which the acid can act upon the 
 metal will be sufficient to cause some of the latter to 
 pass into solution. To obviate this, siphon off the 
 
 FIG 17. 
 
 acid liquid. The sketch (Fig. 17) shows how this can 
 be done. A rubber tube of small diameter may be 
 substituted for the glass siphon. As the acidulated 
 water is conveyed away by the latter, pour distilled 
 
DETERMINATION OF METALS COPPER. 51 
 
 water into the dish. Empty the platinum dish twice 
 in this way ; the current can then be interrupted with- 
 out loss of copper. Finally, disconnect the dish, wash 
 the deposit with hot water and then with alcohol. Dry 
 the precipitated copper at a temperature not exceed- 
 ing 1 00 C; an air-batH, an asbestos plate, or warm 
 iron plate will answer for, this purpose. Do not weigh 
 the dish until it is perfectly cold, and has attained the 
 temperature of the balance-room. 
 
 In the ordinary precipitations of copper from dilute 
 nitric or sulphuric acid solution a current, giving 
 0.3-0.5 c.c. oxy-hydrogen gas (electrolytic gas) per 
 minute, will be amply sufficient. The deposition can 
 also be made in a platinum crucible, or the copper can 
 be precipitated upon the exterior surface of the same. 
 This is sometimes convenient. Place the liquid under- 
 going electrolysis in a beaker glass (capacity 100-250 
 c.c.), and suspend the crucible in it (Fig. 18); support- 
 ing it there by a. tight-fitting cork, through which 
 passes a stout copper wire, w, in connection with the 
 negative electrode of a battery. The positive electrode 
 is a platinum plate projecting into the liquid. The end 
 of the decomposition may be learned by pressing down 
 upon w, or by adding water to the solution in the 
 beaker. No further appearance of copper on the newly 
 exposed platinum indicates the end of the precipita- 
 tion. Raise the crucible from the liquid, wash the 
 copper with water, then detach the vessel carefully 
 from the cork, and dry as already directed. 
 
52 ELECTRO-CHEMICAL ANALYSIS. 
 
 Instead of using either of the suggestions first 
 offered, substitute the apparatus of Riche (Fig. 19) if 
 convenient. This consists in suspending a crucible 
 within a crucible. The sides of the inner vessel are 
 perforated so that the liquid will maintain uniform 
 
 FIG. i 8. 
 
 FIG. 19. 
 
 concentration. It is practically the same as the device 
 just described above. 
 
 Copper can also be precipitated from the solution of 
 ammonium-copper oxalate. To this end the copper 
 solution (sulphate or chloride) is treated with an ex- 
 cess of a saturated solution of ammonium oxalate, 
 care being taken that the entire volume does not 
 
DETERMINATION OF METALS COPPER. 
 
 53 
 
 exceed 170200 c.c. A current liberating 0.10.2 c.c. 
 oxy-hydrogen gas per minute will answer for the 
 deposition, which will require about twelve hours. If 
 the double oxalate solution be heated to 70, and 
 held at that temperature, the decomposition will be 
 finished in five hours at the most. Use ferrocyanide 
 
 FIG. 20. 
 
 of potassium to learn whether all the metal has been 
 precipitated. Wash and dry as already instructed. 
 
 Riidorff obtained excellent results with the follow- 
 ing conditions: 0.1-0.3 gram of metallic copper in 100 
 c.c. water, to which were added 2-3 grams of potas- 
 sium or ammonium nitrate, and 10 c.c. of ammonium 
 
54 ELECTRO-CHEMICAL ANALYSIS. 
 
 hydroxide. A current giving 0.5 c.c. oxy-hydrogen 
 gas per minute will throw out the copper from this 
 solution. 
 
 Moore advises dissolving the recently precipitated 
 copper sulphide, obtained in the ordinary course of 
 analysis, in potassium cyanide; and, after the addition 
 of an excess of ammonium carbonate, electrolyses the 
 warm (70) solution. 
 
 In the analysis of commercial copper Luckovv em- 
 ployed the apparatus pictured in Fig. 20. The beaker 
 (a) contains the electrolyte, and. the metal is precipi- 
 tated upon the cylinder of platinum (ti). It is a very 
 satisfactory device for almost any kind of electrolytic 
 work. 
 
 Foote (Am. Ch. Jr., 6, 333) has also described a 
 very excellent improvement in the apparatus intended 
 for the electrolytic precipitation of copper. 
 
 CADMIUM. 
 
 LITERATURE. Ber., 11,2048; Smith, Am. Phil. Soc. Pr., 1878; 
 Clarke, Z. f. a. Ch., 18, 104; Beilstein and Jawein, Ber., 12, 
 759; Smith, Am. Ch. Jr., 2, 42; Luckow, Z. f. a. Ch., 19, 16; 
 Wright son, Z. f. a. Ch., 15,303; Class en and v. Reiss, Ber., 
 14, 1628. 
 
 Cadmium can be determined electrolytically as 
 readily as copper. Prepare a solution of the chloride 
 or sulphate of definite strength. Remove 50 c.c. to a 
 suitable, weighed platinum vessel. Add one gram of 
 
DETERMINATION OF METALS CADMIUM. 55 
 
 pure potassium cyanide ; dilute with water to 150-200 
 c.c., and then connect with five or six " Crowfoot " 
 cells in the same manner as directed under copper. 
 Introduce the voltameter as there indicated. It is well 
 to commence the decomposition in the evening, and 
 by morning the metal will be fully deposited. A 
 current yielding 0.3 c.c. electrolytic gas per minute 
 will precipitate 0.2 gram metal in this time. To ascer- 
 tain whether the precipitation is complete, raise the 
 level of the liquid in the platinum dish. In washing, 
 it will not be necessary to siphon off the supernatant 
 liquid ; it can be poured off, after interruption of the 
 current, without loss of metal from re-solution. Wash 
 the deposit with cold and hot water. Dry upon a 
 warm iron plate (temperature not exceeding 100 C.). 
 
 Cadmium may also be precipitated from a solution 
 of its sulphate containing a small amount of free sul- 
 phuric acid (2 c.c. H 2 SO 4 , sp. gr. 1.09 for o.i gram 
 cadmium). When operating with a solution of this 
 character, use a current generating 5 c.c. electrolytic 
 gas per minute. Two Bunsen cells will answer, 
 although it may be necessary to reduce the current to 
 some degree ; this can be accomplished by introducing 
 one of the resistances described on pages 26 and 27. 
 Arrange the apparatus as under copper. The pre- 
 cipitation takes place at the ordinary temperature. 
 
 Cadmium can also be deposited quite readily, and 
 in a crystalline form, from its acetate solution. In 
 this case the liquid, containing an excess of free acetic 
 
50 ELECTRO-CHEMICAL ANALYSIS. 
 
 acid, is heated to 70-80 during the decomposition. 
 The apparatus can be arranged as in Fig. 21. The 
 platinum dish is placed in a water bath, and the current 
 made to pass through R (resistance frame) and V 
 (voltameter). An asbestos plate may be substituted 
 
 for the water bath. The current should give I J^-2 
 c.c. of oxy-hydrogen gas per minute. This will insure 
 the precipitation of 0.12-0.15 gram of cadmium in 
 five to six hours. When the precipitation is completed, 
 detach the dish, wash the deposited metal first with 
 
DETERMINATION OF METALS MERCURY. 57 
 
 warm water, then with absolute alcohol, and finally 
 with ether. Dry upon a moderately warm plate. 
 
 If desired, the metal can also be precipitated from 
 the solution of the double oxalate of ammonium and 
 cadmium (see Copper). 
 
 In the usual course of gravimetric analysis cad- 
 mium is obtained as sulphide. To prepare it for elec- 
 trolysis dissolve the same in nitric acid, and after 
 expelling the excess of the latter, add a small amount 
 of potassium hydroxide (sufficient to precipitate the 
 cadmium), and follow this with an excess of potassium 
 cyanide (i to 2 grams). Proceed further as already 
 directed. 
 
 MERCURY. 
 
 LITERATURE. Ber., 6, 270; Clarke, Am. Jr. Sc. and Ar., 16, 200; 
 Classen and Ludwig, Ber., 19, 323; Hoskinson, Am. Ch. Jr., 8, 
 209; Smith and Knerr, ibid.; Smith and Frankel, Am. Ch. Jr., 
 n, 264. 
 
 In preparing solutions for experimental purposes, 
 use either mercuric nitrate or chloride. A current 
 equivalent to 0.5-1.0 c.c. electrolytic gas per minute 
 will precipitate 0.3 gram of mercury from such solu- 
 tions (add a slight amount of free nitric acid) in twelve 
 hours. The deposit will be drop-like in appearance. 
 Even in the presence of considerable free nitric acid 
 it has been found that a current of 4 c.c. electrolytic 
 gas per minute will suffice to precipitate as much as 
 o.io gram of metal in 30 to 45 minutes. In such cases 
 E 
 
58 ELECTRO-CHEMICAL ANALYSIS. 
 
 the acid liquid must be removed before the interrup- 
 tion of the current occurs. 
 
 A mercuric chloride solution, feebly acidulated 
 with sulphuric acid, gradually yields its metal to 
 a current, giving 56 c. c. oxy-hydrogen gas per 
 minute. Always wash the deposited metal with cold 
 water. 
 
 From experiments made in this laboratory the writer 
 prefers and would especially recommend solutions of 
 the double cyanide of mercury and potassium for the 
 electrolytic deposition of mercury. A current of 0.2 
 c.c electrolytic gas per minute will precipitate from 
 0.10-0.20 gram of metal in twelve hours. This pro- 
 cedure requires no further attention after it is once 
 set in operation. The deposit is always compact, 
 and gray in color. Use water only in washing it, 
 for alcohol seems to detach some of the metallic 
 film. The quantity of alkaline cyanide present may 
 vary from 0.26-2.6 grams (KCN) for every gram of 
 mercury. 
 
 In general analysis mercury is frequently obtained 
 as sulphide. Its determination in this form requires 
 time and exceeding care. As a substitute for this the 
 writer would advise the solution of the sulphide in 
 acid, and after neutralizing the excess of the latter 
 with caustic alkali, add an excess of pure potassium 
 cyanide, and electrolyse as above indicated. It is best 
 to use a platinum dish as the negative electrode, and 
 a platinum spiral (p. 49) for the anode. Dry the 
 
DETERMINATION OF METALS BISMUTH. 59 
 
 deposit on a moderately warm plate, or over sulphuric 
 acid. " Crowfoot " cells are well adapted for decom- 
 positions of this kind. 
 
 BISMUTH. 
 
 LITERATURE. Luckow, Z.f. a. Ch.,ig,i6; Classen and v. Reiss, 
 Ber., 14, 1622; Thomas and Smith, Am. Ch. Jr., 5, 114; Moore, 
 Ch. News, 53, 209; Smith and Knerr, Am. Ch. Jr., 8, 206; 
 Schucht, Z. f. a. Ch., 22, 492; Eliasberg, Ber., 19, 326; Brand, 
 Z. f. a. Ch., 28, 596. 
 
 Prepare a solution of definite value as directed 
 under the preceding metals. To a portion of it add 
 an excess of a cold ammonium oxalate solution, and 
 act upon the mixture with a current of o.io c.c. oxy- 
 hydrogen gas per minute. Those who have employed 
 this method find that the deposit is not very adherent, 
 and great care must be taken to expose as large a pla- 
 tinum surface as possible. If metallic particles do sepa- 
 rate, collect them upon a small filter and weigh alone. 
 
 Eliasberg advises bringing the solution of the metal 
 into a weighed platinum dish, and then adding 10 c.c. 
 of a potassium oxalate solution (i 13). Heat is applied, 
 and solid ammonium oxalate is introduced until com- 
 plete solution ensues. Dilute to 170-180 c.c., and 
 warm to 70-80 C, while the current acts. The latter 
 should be so feeble that the liberation of gas in the 
 voltameter is scarcely perceptible. In sixteen hours 
 the greater portion of the metal will have separated, 
 
60 ELECTRO-CHEMICAL ANALYSIS. 
 
 and then oxalic acid is added to distinct acid reaction. 
 As soon as the metal is fully precipitated, interrupt the 
 current and wash the deposit with water. Take special 
 pains in drying, so that the metal does not oxidize. 
 
 Experiments made in this laboratory demonstrate 
 that by electrolysing the sulphate, an alkaline citrate 
 solution, or one containing free citric acid, the bis- 
 muth will be rapidly and completely precipitated. In 
 some cases the deposits were made in small platinum 
 crucibles, while others were thrown upon the exterior 
 surface of the crucibles arranged as under Copper. If 
 peroxide should separate upon the anode in the electro- 
 lysis of citrate or sulphate solutions of bismuth, it will 
 disappear before the decomposition is fully ended. 
 Heat is not required. The best results were obtained 
 with solutions of the sulphate, containing free sul- 
 phuric acid. For example: 0.1542 gram of bismuth, 
 as sulphate, 3 c.c. sulphuric acid (1.09 sp. gr.), and 150 
 c. c. of water, required a current giving 3 c.c. oxy- 
 hydrogen gas per minute, for a period of three hours, 
 to effect the complete separation of the metal. The 
 latter was quite compact and offered no difficulty in 
 washing with water and alcohol. An air-bath was 
 used for drying purposes. 
 
 Moore recommends the following method : add 
 sufficient tartaric acid to the bismuth solution to 
 prevent the precipitation of a basic salt, then, after 
 rendering the solution slightly alkaline with ammon- 
 ium hydroxide, add a considerable excess of glacial 
 
DETERMINATION OF METALS BISMUTH. 6 1 
 
 phosphoric acid, so that the solution has a strong acid 
 reaction. The current should give 0.33-0.50 c.c. 
 electrolytic gas per minute, at first, but this must be 
 increased at last to 7.5 c.c. per minute. The deposit 
 at the beginning of the deposition is loose, but 
 gradually becomes hard and compact. 
 
 Brand's recommendation consists in adding to a 
 somewhat dilute acid solution of bismuth from four 
 to five times as much sodium pyrophosphate as will 
 be necessary to form the double salt. Ammonium 
 carbonate is then carefully introduced until the re- 
 action of the liquid is distinctly alkaline, when 35 
 grams of ammonium oxalate are added. The total 
 dilution should be about 200 c.c. The electrolysis is 
 commenced with a current giving o.i-i.o c.c. electro- 
 lytic gas per minute, although toward the close it will 
 be necessary to increase the same to 2-3 c.c. per min- 
 ute. By following these instructions 0.2500 gram of 
 bismuth can be precipitated in twelve hours. When 
 considerable quantity of metal is present in solution a 
 feeble current should be used at first. If the peroxide 
 appears upon the anode in the course of the decompo- 
 sition, redissolve it in a few drops of a concentrated 
 solution of oxalic acid. However, this should not be 
 done until there is no further separation of metal upon 
 the cathode. The final reduction is ascertained by 
 testing with hydrogen sulphide. The metal is said 
 to sustain a superficial oxidation, hence it is converted 
 into oxide and weighed as such. 
 
62 ELECTRO-CHEMICAL ANALYSIS. 
 
 LEAD. 
 
 LITERATURE. Luckow, Z. f. a. Ch., 19, 215; Riche, Ann. de 
 Chim. et de Phys. [5 ser.], 13, 508; Z. f. a. Ch., 21, 117; Classen, 
 ibid., 257; Hampe, Z. f. a. Ch., 13, 183; May, Am. Jr. Sc. and Ar. 
 [3 ser.], 6, 255, also Z. f. a. Ch., 14, 347 ; Parodi and Mascazzini, 
 Ber., 10, 1098 ; Z. f. a. Ch., 16, 469; 18,588; Riche, Z. f. a. Ch., 17, 
 219; Schucht, Z. f. a. Ch., 21, 488; Tenney, Am. Ch. Jr., 5, 413; 
 Smith, Am. Phil. Soc. Pr., 24, 428. 
 
 The metal may be obtained by electrolysing so- 
 lutions of the double oxalate(see Copper and Cadmium), 
 the acetate, the oxide in sodium hydroxide, or the 
 phosphate dissolved in the latter reagent. A current 
 of o. I 0.2 c.c. electrolytic gas per minute, is sufficient 
 for this purpose. While the metal separates well from 
 either one of these solutions, difficulty is experienced 
 in drying the deposit, for the moist metal almost in- 
 variably suffers a partial oxidation, thus rendering the 
 results high. The deposit can be dried, without oxid- 
 ation, in an atmosphere of hydrogen, but for the in- 
 experienced operator this procedure offers little satis- 
 faction. It is, therefore, better to utilize the tendency 
 of lead to separate, from acid solutions, as the dioxide. 
 For trial purposes make up a definite volume of lead 
 nitrate. Electrolyse several portions (= o.i gram lead 
 each) in a platinum dish connected ivith the anode of a 
 battery, giving 0.1-0.2 c.c. electrolytic gas per minute. 
 In order that the lead may be precipitated wholly 
 as dioxide upon the positive electrode and none in 
 metallic form upon the cathode, it is necessary that 
 
DETERMINATION OF METALS SILVER. 63 
 
 the solution being analyzed should contain from ten 
 to twenty per cent, of free nitric acid. This quantity 
 of acid is required when lead alone is present in so- 
 lution. In the presence of other metals the complete 
 deposition of the lead as dioxide occurs with even 
 less acid (eight per cent.). At the end of the precipi- 
 tation siphon off the acid liquid, and wash in the dish, 
 then dry the deposit at 1 10 C, and weigh. Reference 
 to the literature shows that May preferred, after dry- 
 ing the deposit, to carefully ignite it and finally weigh 
 as lead oxide (PbO). This deportment of lead affords 
 an excellent method by which to separate it from 
 other metals, e.g., mercury, copper, cadmium, silver, 
 and all those soluble in nitric acid, or those which, in 
 a nitric acid solution, are deposited upon the electro- 
 negative pole of a battery. 
 
 The analysis of an alloy of lead, bismuth and 
 copper can be most satisfactorily made by employing 
 electrolytic methods (see Separations). 
 
 SILVER. 
 
 LITERATURE. Luckow, Ding. p. Jr., 178, 43, Z. f. a. Ch., 19, 
 15; Fresenius and Bergmann, Z. f. a. Ch., 19, 324; K rut wig, 
 Ber., 15, 1267; Schucht, Z. f. a. Ch., 22, 417; Kinnicutt, Am. 
 Ch. Jr., 4, 22. 
 
 The experiments of Luckow showed that this metal 
 could be deposited from solutions containing as high 
 as eight to ten per cent, ef free nitric acid. The 
 
64 ELECTRO-CHEMICAL ANALYSIS. 
 
 deposit was spongy, and there was a simultaneous 
 deposition of silver peroxide at the anode. This was, 
 however, prevented by adding to the solution some 
 glycerol, lactic or tartaric acid. A voluminous mass 
 was also obtained from silver solutions, containing an 
 excess of ammonium hydroxide or carbonate, and per- 
 oxide appeared at the same time upon the anode. 
 
 Fresenius and Bergmann, who have given the elec- 
 trolysis of acid solutions of silver particular study, 
 observed that the tendency of the metal to sponginess 
 is most marked when the electrolyte is concentrated, 
 and acted upon by a strong current. In a dilute 
 liquid, the current being feeble, the deposit was com- 
 pact and metallic in appearance (free acid should be 
 present). From neutral solutions, although very 
 dilute, the metal is separated in a flocculent condition 
 by the feeblest currents. Therefore, to obtain results 
 that would answer for quantitative analysis, the fol- 
 lowing conditions were adopted : The total dilution 
 of the solution was 200 c.c. ; in this there was 0.03 
 gram .04 gram silver, and 36 grams of free nitric 
 acid. The poles were separated about I cm. from 
 each other, while the current gave 100-150 c.c. elec- 
 trolytic gas per hour. 
 
 In the experiments of Fresenius and Bergmann, 
 apparatus similar to that in Fig. 22 was employed. 
 It has some decided advantages. Both spiral (a) and 
 cone (b) are constructed of platinum. The metallic 
 deposition, it will be understood, occurs upon the 
 
DETERMINATION OF METALS SILVER. 65 
 
 cone, the sides of which are perforated, so that a uni- 
 form concentration of liquid is preserved throughout 
 the decomposition. When liquid electrolytes contain 
 much iron, it is essential that the oxygen liberated 
 within the cone should be equally distributed over its 
 outer surface. This is made possible through open- 
 ings. The shape of the cone also prevents loss from 
 
 FIG 22. 
 
 the bursting of the bubbles, arising from the platinum 
 spiral in connection with the anode. 
 
 Krutwig advises adding a large excess of ammo- 
 nium sulphate to the silver solution, previously made 
 alkaline with ammonium hydroxide, and employs a 
 current giving 150 c.c. electrolytic gas per hour, but 
 after half an hour the latter is increased to 300 c.c. of 
 
66 ELECTRO-CHEMICAL ANALYSIS. 
 
 gas per hour. In this way, o.i gram of silver is 
 precipitated in two hours. 
 
 The writer's experience has chiefly been with solu- 
 tions of silver containing an excess of alkaline cyanide 
 (l gram KCN for 0.2-0.3 gram silver). With these 
 peroxide separation does not occur, and a very weak 
 current will precipitate 0.15-0.20 gram metal in ten 
 ho.urs from a cold solution. The precipitation can 
 be made either in a platinum dish or crucible as 
 cathode. 
 
 Chlorine, bromine and iodine can be indirectly 
 estimated electrolyttcally by first precipitating them 
 as silver salts, then dissolving the latter in potassium 
 cyanide, and exposing "the resulting solution to the 
 action of a current from three to four " Crowfoot " 
 cells. 
 
 Luckow reduced silver chloride by placing it in a 
 platinum dish, serving as the negative electrode, cov- 
 ered it with dilute sulphuric or acetic acid, and allowed 
 the positive electrode to project into the solution. 
 Four Meidinger cells were strong enough to reduce 
 o.i gram silver chloride in ten minutes. The deposit, 
 while spongy, was adherent. It was washed with 
 water and then thoroughly dried to insure the absence 
 of any acid. (See the reference to Kinnicutt's experi- 
 ments ; also Prescott and Dunn, Jr. An. Ch., 3, 373.) 
 
DETERMINATION OF METALS ZINC. 6/ 
 
 ZINC. 
 
 LITERATURE. Wrightson, Z. f. a. Ch., 15, 303; Parodi and 
 Mascazzini, Ber., 10, 1098, Z. f. a. Ch., 18,587; Riche, Z. f. a. Ch., 
 17, 216; Beilstein and Jawein, Ber., 12, 446, Z. f. a. Ch., 18, 588; 
 Riche, Z. f. a. Ch., 21, 119; Reinhardt and Ihle, Jr. f. pkt. Ch., 
 [N. F.], 24, 193; Classen and v. Reiss, Ber., 14, 1622; Gibbs, 
 Z. f. a. Ch., 22, 558; Luckovv, Z. f. a. Ch., 25, 113. 
 
 Much has been written upon the electrolytic esti- 
 mation of zinc. The personal experience of the writer 
 inclines him to give preference to the method sug- 
 gested by Parodi and Mascazzini. They recommended 
 that the metal be present in solution as sulphate ; its 
 quantity may vary from o. 1-0.25 gram. To it add 4 c.c. 
 of a solution of ammonium acetate, 20 c.c. citric acid, 
 and dilute to 200 c.c. with water. The electrodes are 
 then introduced into the liquid, their distance apart 
 being not more than a few millimetres. The precipi- 
 tation can be made in a beaker glass, using a weighed 
 platinum cone (Fig. 22) as the cathode. The current 
 for this purpose should give 250-300 c.c. electrolytic 
 gas per hour. When the precipitation of metal has 
 ended, which may be ascertained by removing a small 
 quantity of the liquid with a capillary tube and bring- 
 ing it in contact with a drop of a solution of potassium 
 ferrocyanide, remove the bulk of the liquid with a 
 siphon. Wash the deposit with water and alcohol. 
 There is no danger of oxidation during the drying 
 process. It will be discovered on dissolving the pre- 
 cipitated zinc that a considerable quantity of the metal 
 
68 ELECTRO- CHEMICAL ANALYSIS. 
 
 remains unattacked, but this can be removed by gently 
 heating the residue with air contact, then fusing it 
 with potassium bisulphate. 
 
 Beilstein and Jawein add sodium hydroxide to the 
 solutions of zinc nitrate or sulphate, until a precipitate 
 is produced, and dissolve it in potassium cyanide. 
 The decomposition is carried out in a rather large 
 beaker glass, the cathode being either the platinum 
 cone already described (p. 65), or a rather large plati- 
 num crucible suspended from a cork (p. 52), perforated 
 by a copper wire, touching the inner surface of the 
 crucible. Four Bunsen cells (usual size) are sufficient 
 for the precipitation. Wash the deposit as instructed 
 above. 
 
 Reinhardt and Ihle have objected to nearly all the 
 methods which have been proposed for the electrolytic 
 estimation of zinc. They say of the Beilstein and 
 Jawein method .... that the results are fairly good, 
 .... but a strong current is necessary, otherwise the 
 precipitation of the zinc is slow and incomplete, .... 
 the positive pole diminishes in weight very appreciably, 
 .... finally, working with potassium cyanide is very 
 unpleasant. The writer's experience has proved that 
 a current considerably less than that which Beilstein 
 and Jawein first recommended will throw out all the zinc 
 in the course of a night, and further that the anode 
 is not appreciably affected. The method suggested 
 by Reinhardt and Ihle is, however, very excellent 
 and deserves trial by all interested in the electrolytic 
 
DETERMINATION OF METALS - ZINC. 69 
 
 estimation of zinc. Its essential features, taken from 
 their publication, are these: Mix the solution of 
 zinc sulphate or chloride, neutral as possible, with an 
 excess of neutral potassium oxalate, until the pre- 
 cipitate, which appears at first, redissolves. A current 
 giving 90 c.c. electrolytic gas per hour will answer for 
 complete precipitation. 
 
 The immediate decomposition of the zinc oxalate 
 is into zinc and carbon dioxide (two molecules), and 
 the potassium oxalate into carbon dioxide (two mole- 
 cules) and potassium ; the latter then reacts with the 
 water, so that while an abundant liberation of hydrogen 
 occurs at the cathode, the alkali simultaneously set 
 free is converted into acid potassium carbonate by the 
 carbon dioxide at the anode : 
 
 K 2 C 2 4 = (Zn + ^KOU + H 2 ) + 4 CO 2 . 
 Cathode. Anode. 
 
 Therefore, just as long as zinc oxalate is being 
 decomposed, considerable evolution of gas is notice- 
 able at the positive electrode, and when this dimin- 
 ishes, and occasional bubbles escape, the decomposi- 
 tion is complete, and the deposition of metal may be 
 considered finished. 
 
 Free oxalic acid, or any other acid, is not injurious 
 if there is a sufficient quantity of potassium oxalate 
 present. Nitric acid, however, free or combined, should 
 
70 ELECTRO-CHEMICAL ANALYSIS. 
 
 be avoided ; it gives rise to ammonium salts, which 
 prevent the zinc from separating in a dense form. The 
 acid potassium carbonate produced during the decom- 
 position offers great resistance to the current ; it is, 
 therefore, advisable to add potassium sulphate to the 
 solution to increase its conductivity. Reinhardt and 
 Ihle recommend the following solutions for use in 
 decompositions like that just described: 166 grams of 
 potassium oxalate in I litre of water; 250 grams of 
 potassium sulphate in I litre of water, and a solution 
 of oxalic acid saturated at 15 C. 
 
 Experiments, (i) 40 c.c. of a solution of zinc sul- 
 phate (= 0.181 2 gram metallic zinc), to which were 
 added 50 c.c. of potassium oxalate and 100 c.c. of 
 potassium sulphate, were electrolysed with a current 
 giving 109 c.c. of electrolytic gas per hour. After 
 five hours the current was interrupted. The precipi- 
 tated zinc weighed 0.1814 gram. (2) 2.1867 grams 
 brass (containing tin, copper, lead and zinc) were dis- 
 solved in nitric acid and the tin determined in the 
 usual gravimetric way. Its quantity was found to be 
 0.04 per cent. In the filtrate, containing nitric acid, 
 lead and copper were determined simultaneously by 
 electrolysis (the copper separated upon the cathode 
 and the lead as dioxide upon the anode) : 
 
 Found /-- 8 5# Pb and 64.60 # Cu. 
 1 \ 0.85 64.62 
 
 The acid liquid was siphoned off from the deposits, 
 
DETERMINATION OF METALS ZINC. /I 
 
 evaporated to dryness with sulphuric acid, neutral- 
 ized with caustic potash, and then to this (100 c.c. in 
 volume) solution were added 50 c. c. of a solution 
 of potassium oxalate and 100 c. c. of a solution of 
 potassium sulphate. The zinc found equaled 34.50 
 per cent. 
 
 When using this method employ a stout platinum 
 wire, wound to a spiral at the one end, for the anode, 
 and a platinum cone for the cathode. To avoid the 
 peculiar spots which electrolytic zinc shows upon a 
 platinum surface, it will be best to first coat the nega- 
 tive electrode with copper (5 grams). In dissolving 
 the precipitated zinc, use rather dilute nitric acid. 
 The copper layer will be but slightly attacked, and 
 after washing and drying will serve for further depo- 
 sitions. Wash the zinc deposit with water, alcohol 
 and ether ; dry in a desiccator. Oxidation is liable to 
 occur if an air bath be used for the drying. 
 
 Riche employs " a solution of the acetate with an 
 excess of ammonium acetate, obtained by supersatu- 
 ration with ammonia, and acidifying with acetic acid." 
 This method affords good results, as may be seen 
 from the following determination : 0.4736 gram of zinc 
 sulphate was dissolved in 200 c.c. of water, to which 
 were added three grams of sodium acetate and ten 
 drops of ordinary acetic acid. The current gave 3 c.c. 
 of electrolytic gas per minute. After two hours o. 1063 
 gram of metallic zinc was obtained, the required 
 quantity being 0.1072 gram. 
 
72 ELECTRO-CHEMICAL ANALYSIS. 
 
 Moore seems to have obtained exceedingly satis- 
 factory results by precipitating a solution of zinc 
 sulphate with sodic phosphate, then adding an excess 
 of ammonium carbonate, and after dissolving the pre- 
 cipitate in potassium cyanide, the solution was elec- 
 trolysed at a temperature of 80 with a current giving 
 rooo c.c. electrolytic gas per hour. The metal was 
 deposited upon a silver-plated electrode. 
 
 A very convenient stand for electrolytic work and 
 suitable in the zinc depositions has been described by 
 v. Malapert (Z. f. a. Ch., 26, 56), and since conve- 
 niently modified by Herrick (Jr. An. Ch., 2, 167). 
 
 NICKEL AND COBALT. 
 
 LITERATURE. Gibbs, Z. f. a. Ch., 3, 336; Z. f. a. Ch.,n, 10; 22, 
 558; Merrick, Am Ch., 2, 136; Wrightson, Z. f. a. Ch., 15, 300, 
 3 3>3335 Schweder, Z. f. a. Ch., 16,344; Cheney and Richards, 
 Am. Jr. Sc. and Ar. [3], 14, 178; Ohl, Z. f. a. Ch., 18, 523; Luckow, 
 Z. f. a. Ch., 19, 16; Bergmann and Fresenius, Z. f. a. Ch., 19, 
 314; Riche, Z. f. a. Ch., 21, 116, 119; Classen and v. Reis, Ber., 
 14,1622,2771; Schucht, Z. f. a. Ch., 21, 493; Kohn and Wood- 
 gate, Jour. Soc. Chem. Industry, 8, 256. 
 
 These metals are precipitated from solutions of their 
 double cyanides, double oxalates, and sulphates mixed 
 with alkaline acetates, tartrates and citrates, or from 
 ammoniacal solutions. The latter seem best adapted 
 for nickel depositions, the presence of ammonium 
 sulphate or sodium phosphate being favorable to the 
 precipitation. 
 
DETERMINATION OF METALS NICKEL, COBALT. 73 
 
 Fresenius and Bergmann, who have carried out a 
 series of experiments with nickel and cobalt, give the 
 following as satisfactory conditions : 50 c.c. nickel 
 solution (=0.1233 gram nickel), 100 c.c. ammonia 
 (sp. gr. 0.96), io c.c. ammonium sulphate (305 grams 
 of the salt in I litre of water), 100 c.c. of water; sepa- 
 
 FIG. 23. 
 
 ration of the electrodes j~~X cm. : time, four hours. 
 Current, 300 c.c. electrolytic gas per hour. The nickel 
 found was 0.1233 gram. Apparatus suitable for the 
 decomposition just described is represented in Fig. 
 23. The metal is deposited upon the weighed plat- 
 inum cone in the beaker glass, C. The vessel is covered 
 
 F 
 
74 ELECTRO-CHEMICAL ANALYSIS. 
 
 with a glass lid having suitable apertures for the posi- 
 tive and negative electrodes. As soon as the blue- 
 colored liquid becomes colorless, an indication that 
 the metal is completely precipitated, remove a few 
 drops and test with a solution of potassium sulpho- 
 carbonate. If the latter causes only a faint rose-red 
 coloration the deposition of metal may be considered 
 complete. It is not advisable to interrupt the current 
 or to remove the cone from the electrolysed liquid 
 until the latter has been replaced by water. This is 
 effected by the vessels to the left of the figure : A 
 is an aspirator, filled with water ; B is air-tight and 
 empty; x is a doubly bent tube extending to the 
 bottom of C. Open p and the liquid in C is gradually 
 transferred to B. Add fresh water in C. Ammonium 
 chloride should not be present in the solution under- 
 going electrolysis. 
 
 The statements upon nickel also apply to cobalt. 
 An experiment, taken from the article of Fresenius 
 and Bergmann is here given as a guide in determin- 
 ing cobalt: 50 c.c. of cobalt sulphate ( 0.1286 gram 
 cobalt), 100 c.c. of ammonia, 10 c.c. of ammonium sul- 
 phate, 100 c.c. water; current, 300 c.c. electrolytic gas 
 per hour ; separation of electrodes, ^-^ cm. Time, 
 five hours. The deposited cobalt weighed 0.1286 
 gram. 
 
 Use potassium sulpho-carbonate to test when the 
 metal is fully reduced ; it gives a wine-yellow colora- 
 tion with even the most dilute solutions of cobalt salts. 
 
DETERMINATION OF METALS MANGANESE. 75 
 
 When too little ammonia is present in the electro- 
 lyte the results are bad ; too much of this reagent 
 retards the deposition of the cobalt. 
 
 When precipitating these metals from the solutions 
 of their double oxalates, the conditions should be 
 similar to those indicated under Iron (p. 78). 
 
 The writer has electrolysed cobalt compounds con- 
 taining an excess of an alkaline acetate (see Zinc) with 
 perfectly satisfactory results, and would recommend 
 such solutions for this particular metal. 
 
 MANGANESE. 
 
 LITERATURE. Z. f. a. Ch., ix, 14; Rich 6, Ann. de Chim. et de 
 Phys. [5th sen], 13, 508; Lu cko w, Z. f. a. Ch., 19, 17 ; Schucht, 
 Z. f. a. Ch., 22,493; Classen and v. Reiss, Ber., 14, 1622; Moore, 
 Ch. News, 53, 209 ; Smith and Fran kel, Jr. An. Ch., 3, 385; Ch. 
 News, 60, 262; Brand, Z. f. a. Ch., 28, 581. 
 
 The electric current causes this metal, when in solu- 
 tion as chloride, nitrate or sulphate, to separate as the 
 dioxide upon the anode (see Lead). In a solution of 
 nitric acid, the hydrogen set free reduces the acid to 
 oxides of nitrogen and, finally, to ammonia. Hence, 
 when the liquid becomes alkaline or only slightly acid, 
 peroxide will also separate upon the cathode ; it will 
 be necessary to remove this by means of a strip of 
 paper, and ignite the same along with the greater bulk 
 of dioxide, weighing all finally as Mn 3 O 4 . As long 
 as manganese alone is present in the solution, this 
 
76 ELECTRO-CHEMICAL ANALYSIS. 
 
 separation at both electrodes will not cause a serious 
 result; but in electrolysing a nitric acid solution con- 
 taining manganese, magnesium or aluminium, the re- 
 sults will be high. For this reason a solution of the 
 sulphate, slightly acidulated with two to six drops of 
 sulphuric acid, is preferable for electrolytic purposes. 
 Riche advises connecting a platinum crucible or dish 
 with the anode of a battery, warming the solution, 
 during the deposition, upon a water-bath (7O-9O), 
 and then electrolyses with a current generating 
 3 c.c. of oxy-hydrogen gas per minute. Arrange 
 the apparatus as directed under Cadmium. As 
 soon as the manganese has been fully precipitated 
 as dioxide, the current is interrupted, the deposit 
 washed with water, and should any of the dioxide 
 become detached, it must be caught upon a small 
 filter, then dried, ignited and weighed, together with 
 the adherent dioxide, which is changed to Mn 3 O 4 
 before weighing. In the presence of large quantities 
 of iron, this precipitation is unsatisfactory ; therefore, 
 first remove the iron with barium carbonate. Tartaric, 
 oxalic and lactic acids retard the formation of manga- 
 nese dioxide. The same is true of phosphoric acid. 
 Potassium sulphocyanide also prevents its formation, 
 and, if added to solutions in which dioxide is already 
 precipitated, it causes the same to redissolve. 
 
 The apparatus devised by Herpin (Fig. 24) can be 
 well applied in the decomposition of manganese salts. 
 It consists of a platinum dish, A, resting upon a tripod, 
 
DETERMINATION OF METALS MANGANESE. 
 
 77 
 
 B, in connection with the cathode of a battery. The 
 upper portion of the dish is so constructed that it 
 will support an inverted glass funnel, D. Any loss 
 from the bursting of bubbles is prevented by this 
 
 FIG. 24. 
 
 means. The anode is a platinum spiral C. In esti- 
 mating manganese it must not be forgotten to connect 
 the dish with the anode of the battery employed for 
 the decomposition. 
 
78 ELECTRO-CHEMICAL ANALYSIS. 
 
 IRON. 
 
 LITERATURE. Wrightson, Z. f. a. Ch., 15, 305; Parodi and 
 Mascazzinl, G. Ch. ital., 8; also Z f. a. Ch., 18, 588; Luckow, Z. 
 f. a. Ch., 19, 18; Classen and v. Reiss, Ber., 14, 1622; Moore, 
 Ch. News, 53, 209; Smith, Am. Ch. Jr., 10, 330; Brand, Z. f. a. 
 Chem., 28, 581. 
 
 In the historical sketch p. 44, it was mentioned 
 that Parodi and Mascazzini found that iron could be 
 precipitated from solutions of its double oxalates. 
 This suggestion has since been greatly elaborated by 
 Classen, and by him applied to many other metals. 
 Following the recommendation of this chemist the 
 iron salt is placed in a weighed platinum dish con- 
 nected with the cathode of a battery, and to this are 
 added 1 3 c. c. of a solution of potassium oxalate 
 (i 13), and 25 c. c. of water. 3-4 grams of ammo- 
 nium oxalate are next introduced into this liquid and 
 dissolved by the aid of heat, and the entire solution 
 then diluted to 200 c. c., and electrolysed with a cur- 
 rent generating 12 c. c. of electrolytic gas per minute. 
 It is necessary to increase this toward the end of the 
 reduction, to insure the complete deposition of the 
 metal. Test the clear liquid, acidulated with hydro- 
 chloric acid, with potassium sulphocyanide. The 
 solution should be hot (70) during the decomposi- 
 tion. The deposited iron has a steel-gray color; it 
 should be washed with water, alcohol and ether. 
 Avoid the presence of chlorides and nitrates. By 
 
DETERMINATION OF METALS IRON. 79 
 
 carefully complying with the conditions recommended 
 by Classen good results are sure to follow. To show 
 that persons with but little experience can obtain 
 satisfactory results the two following determinations, 
 made by a student, are given : A quantity of ferric 
 ammonium sulphate (= 0.0814 gram iron) was dis- 
 solved in 200 c. c. 'of water, and to this were added 
 eight grams of ammonium oxalate. The solution 
 was heated to 80, and in two hours, with a current 
 of 15 c. c. electrolytic gas per minute, 0.0814 gram 
 of iron was obtained. In a second experiment, the 
 quantity of iron was doubled (= 0.1628 gram iron), 
 while the ammonium oxalate was 1 1 grams, tempera- 
 ture 66 and the current 10 c. c. electrolytic gas per 
 minute. The precipitated iron weighed 0.1619 gram 
 instead of 0.1628. 
 
 The writer found the following procedure admirably 
 suited for iron determinations: 10 c. c. iron solution 
 ( 0.0300 gram metal), 20 c. c. sodium citrate (28 
 grams in % litre) with a little free citric acid, then diluted 
 with water to 150 c. c. Current, 12 c. c. electrolytic 
 gas per minute. In four hours 0.0303 gram iron was 
 precipitated from the cold solution. The deposit was 
 washed as already directed. In several determina- 
 tions aluminium and titanium were present with the 
 iron, but the latter was precipitated free from the other 
 two. 
 
 A third method, originated by Moore, advises that 
 glacial phosphoric acid (15% acid) be added to the 
 
8O ELECTRO-CHEMICAL ANALYSIS. 
 
 distinctly acid solution of ferric chloride or sulphate, 
 until the yellow color fully disappears, then a large 
 excess of ammonium carbonate added and gently 
 warmed until the liquid becomes clear. On electrolys- 
 ing the hot (70) solution by a current equal to 1200 
 c. c. electrolytic gas per hour, the iron is rapidly and 
 completely deposited at the rate of 0.75 gram per hour. 
 The end of the decomposition is recognized by test- 
 ing a portion of the solution with ammonium sulphide. 
 Wash the deposit as already directed. 
 
 URANIUM. 
 
 LITERATURE. Luckow, Z. f. a. Ch., 19, 18; Smith, Am. Ch. 
 Jr., i, 329- 
 
 For electrolytic purposes use the acetate or any of 
 the salts to which an alkaline acetate has been added 
 in large excess, together with a few drops of free acetic 
 acid. The dish in which the deposition is made is 
 placed upon a water-bath, and connected with the 
 negative electrode of a battery giving 2-3 c.c. of elec- 
 trolytic gas per minute (see Cadmium). Heat the 
 liquid to 70 throughout the entire decomposition. 
 The uranium separates as yellow uranic hydroxide 
 upon the cathode; by the continued action of the 
 current it changes to the black hydrated protosesqui- 
 oxide. As soon as the solution becomes colorless, 
 interrupt the current, and quickly pour the clear liquid 
 upon a small filter, to catch any detached particles of 
 
DETERMINATION OF METALS THALLIUM. 8 1 
 
 oxide. Wash with a little acetic acid and boiling 
 water ; dry, ignite and weigh as Ur 3 O 4 (Ur s O 8 ). This 
 method affords an excellent separation of uranium from 
 the alkali and alkaline earth metals. 
 
 THALLIUM. 
 
 LITERATURE. Schu cht, Z. f. a. Ch., 22, 241, 490; Neumann , 
 Ber., 21, 356. 
 
 This metal separates as sesquioxide, from acid solu- 
 tions, upon the anode, while from ammoniacal liquids it 
 is deposited partly as metal and partly as oxide. From 
 oxalate solutions, and from its double cyanides it sepa- 
 rates only as metal, when the current is feeble. How- 
 ever, difficulty is experienced in drying the deposit 
 without having it oxidized. In this respect it is even 
 more troublesome than lead. Neumann utilizes the 
 current to separate the metal, dissolves the latter in 
 acid and measures the liberated hydrogen ; from its 
 volume he calculates the quantity of thallium origi- 
 nally present. For suitable apparatus to carry out 
 this method, consult the literature cited above. 
 
82 ELECTRO-CHEMICAL ANALYSIS. 
 
 PLATINUM, PALLADIUM, MOLYBDENUM, 
 GOLD, ETC. 
 
 LITERATURE. Luckow, Z. f. a. Ch., 19, 13; Classen, Ber., 17, 
 2467; Schucht, Z. f. a. Ch., 22, 242; Smith, Am. Ch. Jr., i, 329; 
 Hoskinson and Smith, ibid., 1,90; Smith and Keller, Am. 
 Ch. Jr., 12, 252. 
 
 The solutions of platinum salts, slightly acidulated 
 with sulphuric acid, and acted upon by a feeble cur- 
 rent, give up the metal as a bright, dense deposit upon 
 the dish, frequently so light as to be scarcely dis- 
 tinguished from the latter. In using platinum vessels 
 for this purpose, first coat them with a rather thick 
 layer of copper, upon which afterward deposit the 
 metal. Wash the deposit with water and alcohol. 
 
 In ordinary gravimetric analysis, potassium is 
 frequently estimated as potassio-platinum chloride, 
 K 2 PtCl 6 . This operation requires time and care. 
 Rather dissolve the double salt in water, slightly acidu- 
 late the solution with sulphuric acid, and electrolyse 
 with one Bunsen cell. The deposit will be black 
 and spongy if the current is too strong. From the 
 quantity of platinum found calculate the potassium. 
 
 The following facts have been taken from Classen's 
 article (see Literature) : A platinic chloride solution, 
 containing 0.6 gram platinum, was diluted to 200 c.c. 
 with water and electrolysed. In five hours 0.4581 
 gram platinum had separated. When mixed with 
 ammonium oxalate 0.0996 gram platinum was pre- 
 
DETERMINATION OF METALS PALLADIUM. 83 
 
 cipitated in two hours. From a solution, feebly acidu- 
 lated with hydrochloric acid, four Meidinger cells 
 precipitated 0.737 gram platinum in the course of 
 twenty-four hours. On dissolving 0.5 gram ammonio- 
 platinum chloride in 100 c.c. water and mixing with 
 ammonium oxalate the current from one Bunsen cell 
 precipitated 0.208 gram platinum in five hours. 0.6042 
 gram potassio-platinum chloride was dissolved in 150 
 c.c. of water, acidulated with thirty drops of dilute sul- 
 phuric acid (i : 6), and in six hours gave 0.2017 gram 
 platinum to the action of the current; 0.5015 gram 
 of the same salt gave 0.0956 gram metal in two 
 hours; while 0.4545 gram of the double chloride 
 dissolved in 100 c. c. water, and not acidulated, gave 
 0.0688 gram platinum in three hours. 
 
 PALLADIUM can be deposited in the same manner as 
 platinum. The use of a feeble current gives a bright 
 metallic deposit ; otherwise it is spongy. 
 
 It has been recently discovered, in this laboratory, 
 that this metal can be rapidly and fully precipitated 
 from ammoniacal solutions of palladammonium chlo- 
 ride, by a current liberating 0.7 c.c. electrolytic gas per 
 minute. Palladammonium chloride, Pd(NH 3 Cl) 2 , is 
 prepared by adding hydrochloric acid to an ammonium 
 hydroxide solution of palladious chloride. To show 
 the accuracy of this method several actual determina- 
 tions are here introduced: (i) A quantity of the 
 double salt (= 0.2228 gram palladium) was dissolved 
 
84 ELECTRO-CHEMICAL ANALYSIS. 
 
 in ammonium hydroxide; to this solution were added 
 20-30 c.c. of the same reagent (sp. gr. 0.935), and 100 
 c.c. of water. A current, giving 0.9 c.c. electrolytic 
 gas per minute, acted upon this mixture through the 
 night, and deposited 0.2225 gram palladium. (2) In 
 another experiment, with conditions similar to those 
 just mentioned, excepting that the quantity of the 
 palladammonium chloride was doubled, and the current 
 reduced to 0.7 c.c. electrolytic gas per minute, the 
 quantity of metal precipitated equaled 0.4462 gram 
 instead of 0.4456. Oxide did not separate upon the 
 anode. The deposit, when dry, showed the same 
 appearance as is ordinarily observed with this metal 
 in sheet form. It was washed with hot (70) water, 
 and dried in an air-bath at no-ii5. It is best to 
 deposit the palladium in platinum dishes previously 
 coated with silver. 
 
 WHEN the electric current acts upon ammoniacal, 
 or feebly acid solutions of ammonium molybdate, a 
 beautiful iridescence appears ; as the action continues 
 this assumes a black color, and the deposit becomes 
 more dense. It is the hydrated sesquioxide, which is 
 precipitated ; after washing with hot water it is dried, 
 carefully ignited to molybdic acid, and weighed. The 
 precipitation can take place in a platinum crucible, in 
 connection with the cathode of a battery liberating 
 3-4 c.c. of electrolytic gas per minute. The tempera- 
 ture of the solution should not fall below 70 ; its 
 
DETERMINATION OF METALS TIN. 85 
 
 volume may vary from 25 c.c.-i25 c.c. Three hours 
 were required for the precipitation of 0.0329-0.1000 
 gram of oxide. 
 
 GOLD is best deposited from solutions of its double 
 cyanides. 
 
 THE facts relating to the electrolytic behavior of 
 vanadium, tungsten and osmium are, at the present 
 writing, few in number and will not be given here. 
 
 TIN. 
 
 LITERATURE. Luckow, Z. f. a. Ch., 19, 13; Classen and v. 
 Reiss, Ber., 14, 1622; Gibbs, Ch. News, 42, 291 ; Classen, Ber., 
 !7, 2467; 18, 1104. 
 
 Tin may be deposited either from a solution of its 
 chloride, or from that of ammonium tin oxalate. It 
 is advisable not to use potassium oxalate in the electro- 
 lysis, for then a basic salt is liable to separate upon the 
 anode. Three to four grams of ammonium oxalate 
 will be sufficient for the decomposition. The current 
 should liberate 3 c.c. electrolytic gas per minute. 
 When electrolysing acid tin solutions do not interrupt 
 the current until the free acid is first removed ; this is 
 not necessary when operating with oxalate solutions. 
 
 Classen has published a great deal of very valuable 
 information upon the electrolysis of this metal, and 
 has discovered that a tin solution, containing an excess 
 
86 ELECTRO-CHEMICAL ANALYSIS. 
 
 of ammonium sulphide, largely diluted with water, 
 yields a quantitative deposition of the metal when 
 exposed to the action of a current from two Bunsen 
 cells. In dilute sodium or potassium sulphide solu- 
 tion the tin precipitation is incomplete, and whenever 
 such conditions exist, the sodium or potassium salt 
 must be converted into ammonium sulphide. To this 
 end the liquid is mixed with about 25 grams of ammo- 
 nium sulphate, free from iron, and the solution then 
 carefully warmed in a covered vessel until the evolu- 
 tion of hydrogen sulphide ceases ; after which the 
 liquid is heated to incipient ebullition for fifteen min- 
 utes. Allow it to cool, dissolve any sodium sulphate 
 which may have separated by the addition of water, 
 and electrolyse with a current of 9-10 c.c. oxy-hydro- 
 gen gas per minute. The tin separates in a gray, dense 
 layer. Wash it with water and alcohol. At times 
 sulphur sets itself upon the tin deposit ; this is diffi- 
 cult to remove, but can be detached, after washing the 
 deposit with alcohol, by gently applying a linen hand- 
 kerchief. 
 
DETERMINATION OF METALS ANTIMONY. 
 
 ANTIMONY. 
 
 LITERATURE. Wright son, Z. f. a. Ch., 15, 300 ; Parodi and 
 Mascazzini, Z. f. a. Ch., 18, 588; Luckow, Z. f. a. Ch., 19, 13 ; 
 Classen and v. Reiss, Ber., 14, 1622; 17,2467; 18,1104; Lecre- 
 nier, Chemiker Zeitung, 13, 1219; Chittenden, Pro. Conn. Acad. 
 Sci., Vol. 8. 
 
 Antimony, when precipitated from a solution of its 
 chloride, or from that of antimony potassium oxalate, 
 does not adhere well to the cathode. It is deposited 
 very slowly from a solution of potassio-antimony 
 tartrate. Its deposition from a cold ammonium sul- 
 phide solution is satisfactory, but the use of this 
 reagent for this purpose is not pleasant, especially 
 when several analyses are being carried out simulta- 
 neously. For this reason potassium or sodium sul- 
 phide has been substituted. The alkaline sulphide 
 used must not contain iron or alumina. 
 
 The antimony solution, mixed with sodium sulphide, 
 is largely diluted with water. A more rapid reduction 
 follows in consequence of the dilution. A current 
 giving 2-3 c.c. of electrolytic gas per minute will pre- 
 cipitate o.i gram of antimony in four or five hours. 
 To ascertain when all the metal is deposited incline 
 the dish slightly, thus exposing a clean platinum sur- 
 face. If this remains bright for half an hour the pre- 
 cipitation is finished. In separating antimony from 
 the heavy metals, e. g., lead, it happens that alkaline 
 sulphides containing polysulphides are used, or are 
 
55 ELECTRO-CHEMICAL ANALYSIS. 
 
 produced. To remove these Classen proposed adding 
 to the antimony-polysulphide mixture, already in a 
 weighed platinum dish, an ammoniacal solution of 
 hydrogen peroxide, and warming the same until the 
 liquid becomes colorless. When this is accomplished, 
 even if a precipitate has been produced, add, after 
 cooling, 10 c.c. of a concentrated solution of sodium 
 monosulphide, and electrolyse with a current of 1.5-2 
 c.c. electrolytic gas per minute. Wash the deposit 
 with water and alcohol. 
 
 Lecrenier writes as follows relative to the preceding 
 method: The precipitation is all that one can desire, 
 providing the solution of the sulpho-salt is absolutely 
 free from polysulphides ; otherwise, it is incomplete. 
 The antimony sulphide, obtained in the ordinary 
 course of analysis, always contains sulphur, and this 
 must be eliminated. To remove the various incon- 
 veniences connected with the method add 50-75 c.c. 
 of a 20 per cent, solution of sodium sulphite to the 
 solution after the addition of the excess of sodium 
 sulphide, then heat the liquid to complete decoloriza- 
 tion ; allow to cool, after which the current is con- 
 ducted through the liquid. This can rise to 5 c.c. per 
 minute without impairing the result ; but it is not best, 
 as the precipitated metal is then not very coherent. 
 It is better to use a current giving not more than half 
 of the above volume of electrolytic gas per minute. 
 When the quantity of antimony does not exceed 
 0.2 gram the deposit will be adherent and free from 
 
SEPARATION OF METALS. 89 
 
 sulphur ; wash with water, alcohol and ether. Sulphur 
 will separate upon the anode, despite the presence of 
 an excess of sodium sulphite. This, however, does 
 not affect the result. 
 
 ARSENIC. 
 
 LITERATURE. Luckow, Z. f. a. Ch., 19, 14; Classen and v. 
 Reiss, Ber., 14, 1622; Moore, Ch. News, 53, 209. 
 
 A successful method for the complete deposition of 
 arsenic is not known. The current, acting upon the 
 chloride, causes complete volatilization of the metal 
 in the form of arsine. Its separation from oxalate 
 solutions is incomplete; nor do the sulpho-salts 
 answer for electrolytic purposes. 
 
 2. SEPARATION OF THE METALS. 
 
 Electrolysis, to be of value, must not only furnish 
 the analyst with methods suitable for the complete 
 deposition of metals, but it should, in addition, enable 
 him to separate metallic mixtures. The data given 
 in the preceding pages will serve for this purpose, but, 
 as special treatment is required in some instances, a 
 brief outline of a series of separations will be indi- 
 cated. 
 
90 ELECTRO-CHEMICAL ANALYSIS. 
 
 COPPER. 
 
 We recall, first of all, that this metal can be de- 
 posited electrolytically from solutions in which free 
 nitric acid is present (p. 51). This behavior renders 
 the separation of copper from cadmium possible (Am. 
 Ch. Jr., 2, 42). Place the solution containing the two 
 metals in a beaker glass of 200 c. c. capacity ; suspend 
 (p. 52) a weighed platinum crucible in the liquid, 
 and precipitate the copper upon it. The total dilution, 
 during the decomposition, should not exceed I5<DC. c. 
 As much as 5 per cent, of nitric acid can be present ; 
 the current should give 0.5 c. c. electrolytic gas per 
 minute. When all the copper is precipitated, washed, 
 dried and weighed (p. 51), make the residual liquid 
 alkaline with sodium hydroxide, and add sufficient 
 potassium cyanide to redissolve the precipitate. Elec- 
 trolyse as directed (. 55). Copper and cadmium 
 can also be separated in solutions of their double 
 alkaline cyanides (Jr. An. Ch.,^, 385). Five to six 
 grams of potassium cyanide should be added for every 
 0.2-0.4 gram of metal. Do not work with less than 
 200 c. c of liquid, and the current should not exceed 
 0.28 c.c. of electrolytic gas per minute. Under these 
 conditions the cadmium is deposited, while the copper 
 remains dissolved. Very recent experiments, made 
 in this laboratory, show that also in the presence of an 
 excess of free sulphuric acid the current will precipi- 
 tate copper free from cadmium: e.g., 0.1975 gram of 
 
SEPARATION OF METALS COPPER. 9 1 
 
 metallic copper, and 0.1828 gram of cadmium, both as 
 sulphates, were dissolved in 20 c. c. of water ; to this 
 were added 10 c. c. of sulphuric acid, of 1.09 sp. gr. 
 and 100 c. c. of water. The current gave 0.30 c. c. 
 electrolytic gas per minute. The precipitated copper 
 weighed 0.1976 gram; it contained no cadmium. 
 
 It is not possible to separate these metals when 
 present together in an oxalate solution. 
 
 The precipitation of copper in nitric acid solutions 
 further enables us to separate it from iron, aluminium, 
 chromium, cobalt, nickel, zinc, the alkaline earth and 
 the alkaline metals, though it would perhaps be better 
 to execute the separation from the first six in a solu- 
 tion containing free sulphuric acid. From mercury, 
 silver and bismuth the copper cannot be separated in 
 the presence of nitric or sulphuric acid. For the elec- 
 trolytic separation of copper from mercury see p. 97. 
 Its separation from bismuth has only recently been 
 made possible by combining the behavior of copper 
 in the presence of an excess of alkaline cyanide, and 
 that of bismuth where it exists as a double citrate in 
 an alkaline solution (p. 60). Add 3-4 grams of citric 
 acid to the bismuth solution, so that upon the later 
 addition of sodium hydroxide to alkaline reaction a 
 precipitate is not produced. Into this liquid introduce 
 the cyanide copper solution, and electrolyse with a 
 current giving 0.15 c.c. electrolytic gas per minute. 
 
 In a solution of copper and lead, containing 5 per cent, 
 of nitric acid, the former will be deposited completely 
 
92 ELECTRO-CHEMICAL ANALYSIS. 
 
 at the cathode, while the latter is fully precipitated as di- 
 oxide at the anode (p. 62). This course is adopted when 
 separating these metals in alloys or minerals (p. 63). 
 
 The separation of copper from manganese should 
 be conducted in solutions containing a slight excess 
 of sulphuric acid. While the copper is deposited as 
 such upon the cathode, the manganese separates upon 
 the anode as dioxide (p. 76). A platinum foil may be 
 used as anode in this separation. Another method, 
 applicable here, is based on the observation that man- 
 ganese remains dissolved in the presence of phos- 
 phoric acid, while the copper is deposited in its usual 
 form. For example, 0.1770 gram copper and 0.1500 
 gram manganese, both as sulphates, were treated with 
 30 c.cr of sodium phosphate, of sp. gr. 1.0388, and 10 
 c.c. phosphoric acid, of sp. gr. 1.347, trien diluted to 
 1 50 c.c. with water and electrolysed with a current 
 giving I c.c. of electrolytic gas per minute. The pre- 
 cipitated copper weighed 0.1765 gram. Manganese 
 did not separate, even as dioxide. (See Am. Ch. Jr., 
 
 12, 329.) 
 
 The deposition of copper in the presence of anti- 
 mony is yet unsatisfactory. When the latter does not 
 exceed j of the quantity of the first, no fault can be 
 found with the separation (p. 39, and Wrightson, Z. f. 
 a. Ch., 15, 297). 
 
 As to the separation of copper from arsenic, Classen 
 remarks (Ber., 15, 297), that when the arsenic exceeds 
 0.20 per cent., the deposited copper is more or less 
 
SEPARATION OF METALS COPPER. 93 
 
 dark in color, and the result will be high. Some 
 chemists have advised that after the copper deposit 
 has been dried, it should be heated to volatilize the 
 arsenic ; the residual cupric oxide is redissolved and 
 its solution again electrolysed. This procedure will 
 be satisfactory when arsenic is present in traces, other- 
 wise it is worthless. The arsenic in copper ores can 
 be entirely removed by evaporating their acid solution 
 with bromine, when it will be expelled as bromide. 
 The copper results are then satisfactory. 
 
 McCay (Chemiker Zeitung, 14, 509) has observed 
 that when the current from 4-6 Meidjnger cells is con- 
 ducted through a potassium arsenite solution, made 
 distinctly alkaline with ammonium hydroxide, this 
 salt sustains no change. With copper, under like con- 
 ditions, the separation of the metal is quantitative. 
 Upon this behavior he bases a very excellent separa- 
 tion of these two metals. The only care necessary is 
 to see that not too much ammonia is employed. In 
 this laboratory like results were obtained, but prefer- 
 ence has since been given to the following course : 
 Add the copper solution to that of the alkaline arsen- 
 ite or arsenate, and follow it with a solution of potas- 
 sium cyanide until the precipitate first produced is 
 just dissolved; the liquid will then show a slight 
 purple tint. A current of 0.25 c.c. electrolytic gas 
 per minute, precipitates the copper quite rapidly 
 under these conditions ; the deposit will contain no 
 arsenic (Am. Ch. Jr., 12, 428). 
 
94 ELECTRO-CHEMICAL ANALYSIS. 
 
 When antimony, arsenic and tin are associated with 
 copper, treat the sulphides with sodium sulphide. 
 The resulting alkaline sulphide solution can then be 
 employed for the separation of the first three (p. 102), 
 while the insoluble copper sulphide may be dissolved 
 and treated as described on page 54. 
 
 CADMIUM. 
 
 The methods already described under copper are 
 sufficient for the separation of cadmium from this 
 metal. A solution containing free nitric acid is used 
 for the separation of cadmium from silver, mercury, 
 lead and bismuth ; the latter is also separated from it 
 by using a solution in which there is a slight excess 
 of sulphuric acid (p. 60). When these metals have 
 been removed from their solution, neutralize the 
 excess of acid with potassium hydroxide, add a slight 
 excess of potassium cyanide and electrolyse the liquid 
 for the estimation of the cadmium, as directed on 
 page 55- 
 
 When there is an excess of but 2 c.c. of sulphuric 
 acid, of sp. gr. 1.09, cadmium can be precipitated 
 (p. 55), and thus separated from iron, aluminium, chro- 
 mium, zinc, cobalt, nickel and manganese (the latter 
 deposits at the same time as dioxide upon the anode, 
 p. 76). Another method which serves for the separa- 
 tion of cadmium from either zinc or cobalt, consists 
 in having these metals in solution in the form of 
 
SEPARATION OF METALS CADMIUM. 95 
 
 double cyanides with the alkaline cyanides. The 
 volume of the aqueous solution should be at least 
 200 c.c. ; to this add 4^ grams of potassium cyanide, 
 and electrolyse the liquid with a current giving 0.30 
 c.c. electrolytic gas per minute (Am. Ch. Jr., n, p. 
 352). Cadmium cannot be separated from nickel by 
 this method. 
 
 Under the special methods given for the estimation 
 of cadmium (p. 55) it was mentioned that it separates 
 well from solutions of the acetate. Yver (B. s. Ch. 
 Paris, 34, 18) has employed this behavior to separate 
 cadmium from zinc. The method is this : the metals 
 are converted into acetates by the addition of 2-3 
 grams of sodium acetate to their solution, followed 
 by several drops of free acetic acid. This liquid is 
 then exposed to the current from two ordinary Daniell 
 cells. Heat (70) the solution during the decomposi- 
 tion. The precipitated cadmium contains no zinc. 
 Three to four hours are necessary for the reduction 
 of 0.18-0.210 gram of cadmium. Remove the zinc 
 from the filtrate by the method of Riche (p. 71). 
 Smith and Knerr (Am. Ch. Jr., 8, 210) have tried this 
 separation, and recommend that the current should 
 not exceed 0.10.2 c.c. of electrolytic gas per minute. 
 It is also essential that the liquid be held at a nearly 
 uniform temperature (70) during the reduction. The 
 dilution of the liquid should not exceed 100 c.c. 
 
 The same chemists also (Am. Ch. Jr., 8, 210) 
 found that upon electrolysing a solution of these two 
 
96 ELECTRO-CHEMICAL ANALYSIS. 
 
 metals, to which 3-4 grams of sodium tartrate and 
 tartaric acid had been added, with a current of 3-4 
 c.c. electrolytic gas per minute, tKe cadmium was 
 deposited completely from the warm solution, and 
 contained no zinc. 
 
 Eliasberg (Z. f. a. Ch., 24, 550) has also proposed 
 a method for the separation of cadmium from zinc : 
 Dissolve the metallic oxides in hydrochloric acid, 
 evaporate their solution to dryness, add 8-10 grams 
 of potassium oxalate, and 2-3 grams of ammonium 
 oxalate, diluting finally to 100 c.c. ; heat "to boiling 
 and electrolyse the warm (not boiling) liquid with a 
 current equal to 0.15 c.c. electrolytic gas per minute. 
 Cover the vessel in which the decomposition is made. 
 Six to seven hours' will be required for the com- 
 plete deposition of 0.15 gram of metal (cadmium). 
 The electrolytic separation of these two metals is also 
 possible in a solution of their phosphates, dissolved 
 in phosphoric acid (Am. Ch. Jr., 12, 329). 
 
 To separate cadmium from antimony and tin it is 
 necessary to have recourse to the usual method of 
 analysis, the solubility of the sulphides of the first 
 two in alkaline sulphides. A direct separation of 
 cadmium from arsenic is possible, but that the cad- 
 mium may be precipitated absolutely free from 
 arsenic, the latter must be present in the solution as 
 an arsenate. Upon adding two grams of potassium 
 cyanide to such a solution, and electrolysing the same 
 with a current equal to 0.3 c.c. of electrolytic gas per 
 
SEPARATION OF METALS MERCURY. 97 
 
 minute, the cadmium will be completely precipitated 
 in ten hours. The reduction is made in cold solu- 
 tions (Am. Ch. Jr., 12, p. 428). 
 
 MERCURY. 
 
 This metal is deposited quite rapidly from solutions 
 containing free nitric acid (p. 57), hence under such 
 conditions it may be separated from cadmium, iron, 
 aluminium, chromium, zinc, nickel, cobalt, barium, 
 strontium, calcium, magnesium and the alkalies. When 
 lead and mercury are exposed, in a solution of nitric 
 acid, to the action of the current, they are deposited 
 simultaneously, the lead as dioxide at the anode 
 (p. 62), and the mercury as metal upon the cathode. 
 Manganese and mercury are separated to the best 
 advantage in solutions containing free sulphuric acid 
 (p. 76). Mercury cannot be separated in the electro- 
 lytic way from silver and bismuth. From copper, as 
 long as the quantity of this metal does not exceed 20 
 per cent, of that of the mercury, the separation can be 
 made in a cyanide solution (Jr. An. Ch., 3, 254). As 
 an example, it may be stated that 0.1833 gram mer- 
 cury, as chloride, and 0.0259 gram copper, as sul- 
 phate, with 1.5 grams potassium cyanide, were diluted 
 to 200 c.c. with water, and then electrolysed in the 
 cold, with a current giving 0.32 c.c. of electrolytic gas 
 per minute. At the end of sixteen hours 0.1833 gram 
 mercury had separated. 
 
98 ELECTRO-CHEMICAL ANALYSIS. 
 
 More recent experiments, made in this laboratory, 
 prove that mercury may be readily separated in the 
 same way from zinc, nickel and cobalt. The quantity 
 of alkaline cyanide to be used in these separations 
 may vary from three to four grams, although when 
 cobalt is to be separated from mercury good results 
 will not be obtained if more than three grams of potas- 
 sium cyanide are present for 0.30.4 gram of metal. 
 The current should not exceed 0.8 c.c. of electrolytic 
 gas per minute (Am. Ch. Jr., 12, 104). 
 
 In separating mercury from tin and antimony, pre- 
 pare their sulphides, and digest these with ammonium 
 sulphide, dissolving out the first two. The residual 
 mercury sulphide is then dissolved in aqua regia, and 
 after neutralizing the excess of acid with an alkaline 
 hydroxide, potassium cyanide is added in sufficient 
 quantity to form the double cyanide, which is then 
 electrolysed as described, p. 58. Mercury is separated 
 from arsenic similarly to cadmium from this metal, 
 although it is immaterial whether the arsenic exists 
 in the solution as an arsenite or arsenate (p. 96). 
 
 BISMUTH. 
 
 At present there is no satisfactory electrolytic 
 method known for the separation of this metal from 
 mercury, silver and lead. Its separation from cad- 
 mium is effected in solutions containing free sulphuric 
 acid (5-10 c.c. of sp. gr. 1.09), p. 60. This course will 
 
SEPARATION OF METALS LEAD. 99 
 
 also serve to separate it from iron, manganese, zinc, 
 nickel, cobalt, aluminium, chromium, uranium, mag- 
 nesium and the alkaline metals (p. 60). The method 
 of Eliasberg (p. 59) may also be used for the separa- 
 tion of bismuth from zinc, nickel, cobalt and uranium. 
 In separating bismuth from those metals the sulphides 
 of which are soluble in alkaline sulphides, it is neces- 
 sary to have the usual gravimetric course precede the 
 electrolytic reduction. 
 
 LEAD. 
 
 The deposition of lead as dioxide upon the anode 
 (p. 62) in the presence of at least five per cent, of 
 nitric acid affords a method for its separation from 
 mercury, silver, copper, cadmium, iron, chromium, 
 aluminium, zinc, nickel, cobalt, uranium, the metals 
 of the alkaline earths and the alkaline metals. It 
 will be remembered, of course, that some of these 
 metals separate as such upon the cathode simultane- 
 ously with the lead upon the anode. Lead, in some 
 respects, is much like manganese, from which it can- 
 not be separated electrolytically. Its deposition re- 
 quires no special description, as the conditions already 
 described upon p. 63 are to be observed in the per- 
 formance of the separations just indicated. Lead, tin, 
 antimony and arsenic are separated as directed under 
 the preceding heavy metals. Follow the ordinary 
 gravimetric course. 
 
 Lead dioxide, like manganese dioxide (p. 76), is 
 
IOO ELECTRO-CHEMICAL ANALYSIS. 
 
 not separated from solutions containing an excess of 
 an alkaline sulphocyanide, and, if already precipitated 
 as dioxide, will redissolve upon the addition of the 
 sulphocyanide. 
 
 SILVER. 
 
 To separate silver and copper electrolytically, mix 
 equal quantities of the two metals, in the form of 
 nitrates, with four and one-half grams of potassium 
 cyanide, dilute to 200 c.c. with water, and electrolyse 
 with a current, giving 0.15-0.80 c.c. electrolytic gas 
 per minute (Am. Ch. Jr., 12, 104). As much as 0.2 
 gram of silver will be deposited in 1214 hours. If 
 desirable, expose the filtrate containing the copper to 
 the action of a stronger current (3 c.c. O-H gas per 
 minute) ; as soon as the excess of alkaline cyanide is 
 decomposed, the copper will be deposited in a dense 
 and brilliant coating. Proceed as directed (p. 94) in 
 separating silver from cadmium. There is no known 
 electrolytic method for the separation of silver from 
 mercury. It is true both can be precipitated from a 
 nitric acid solution (pp. 57, 64), their joint weight 
 determined, after which the mercury can be expelled 
 by heat and the silver residue be re-weighed. 
 
 There is no electrolytic method known for the 
 separation of silver from bismuth. The separation of 
 silver from lead is made in a nitric acid solution (p. 
 64). A similar solution is used to separate it from 
 the metals of other groups. 
 
SEPARATION OF METALS SILVER. IOI 
 
 When antimony, tin and silver are present together, 
 digest their sulphides with sodium sulphide, which 
 will bring the antimony and tin into a proper condition 
 to effect their separation electrolytically (p. 102). The 
 insoluble silver sulphide is dissolved in nitric acid, 
 and, after the excess of the latter is expelled, potas- 
 sium cyanide is added in excess and the resulting 
 liquid electrolysed in the cold, with a feeble current. 
 The silver is deposited as a dense coating, and may 
 be washed with hot water. 
 
 It is possible to separate silver from arsenic in the 
 presence of three grams of potassium cyanide, pro- 
 viding the arsenic exists in the solution as an arsenate. 
 A current, giving 0.30 c.c. electrolytic gas per minute, 
 will be sufficient for the metallic reduction. Deter- 
 mine the arsenic in the residual liquid by the usual 
 gravimetric method (Am. Ch. Jr., 12, p. 428). 
 
 The course just described (above) for the separation 
 of silver from copper will answer admirably for the 
 same purpose with silver, zinc, nickel and cobalt. Not 
 more than three grams of potassium cyanide are re- 
 quired for 0.2 gram of each metal. The total dilution 
 should not be less than 200 c.c., and the current not 
 stronger than 0.3 c.c. electrolytic gas per minute. 
 
102 ELECTRO-CHEMICAL ANALYSIS. 
 
 Much credit is due Classen and his co-laborers for 
 valuable data upon the electrolytic separation of the 
 following metals : 
 
 ANTIMONY FROM TIN. 
 
 The sulphides (or residue from a solution of the 
 metals) are placed in a weighed platinum dish, and 
 covered with 60 c.c. of sodium monosulphide, to which 
 is added one gram of sodium hydroxide. If imme- 
 diate solution does not occur, apply heat, then cool. 
 Conduct a current of 1.5-2.0 c.c. of electrolytic gas 
 per minute through this mixture. When the reduc- 
 tion is finished, pour off the liquid into a second dish. 
 Treat the antimony deposit as already directed (p. 
 87). To prepare the tin solution for electrolysis, pro- 
 ceed as described (p. 86) for the conversion of the 
 sodium into ammonium sulphide (Ber., 17, 2245 ; 18, 
 1 1 10). 
 
 ANTIMONY FROM ARSENIC. 
 
 These metals, or compounds of the same, are evapor- 
 ated to dryness with aqua regia, the residue dissolved 
 in 23 c.c. of water ; concentrated sodium hydroxide is 
 added so that there will be one gram of alkali present 
 in the liquid, and finally add 60 c.c. of sodium mono- 
 sulphide. Electrolyse as in the separation of anti- 
 mony from tin (Ber., 19, 323). 
 
 If antimony, arsenic and tin are present together, 
 
SEPARATION OF IRON FROM MANGANESE. 103 
 
 the arsenic is expelled from their solution by the 
 Fischer-Hufschmidt method (Ber., 18, 1 1 10), and the 
 separation of the tin and antimony made as already 
 directed on the preceding page. 
 
 In general analysis phosphoric acid is frequently 
 precipitated as tin phosphate. The latter, of course, 
 contains oxide of tin. Dissolve the precipitate in 
 ammonium sulphide. On electrolysing the solution 
 the tin is precipitated, and the filtrate will contain all 
 the phosphoric acid; this can be estimated in the 
 usual way (Classen). By observing this suggestion 
 the determination of the phosphoric acid in a separate 
 portion of the material will not be required. 
 
 IRON, MANGANESE, ZINC, NICKEL, COBALT, ALU- 
 MINIUM, CHROMIUM AND PHOSPHORIC ACID. 
 
 Electrolytic methods for the separation of these 
 metals are not either so numerous, nor so thoroughly 
 worked out as with the metals already considered. 
 Their separation from the heavy metals has been out- 
 lined under these, and it only remains to describe the 
 courses which may be pursued with this group of 
 metals when present together. 
 
 Concerning the separation of iron from manganese, 
 it should be remembered that objections have been 
 offered to the suggestion of Classen (Ber., 18, 1787), 
 hence to obtain results at all satisfactory it is advisable 
 to carry out the separation exactly as given by this 
 
IO4 ELECTRO-CHEMICAL ANALYSIS. 
 
 chemist : " If a solution of the double oxalates of iron 
 and manganese is subjected to electrolysis, without 
 the previous addition of a great excess of ammonium 
 oxalate ..... it is impossible to obtain a 
 quantitative separation of the two metals, because the 
 manganese dioxide carries down with it considerable 
 quantities of ferric hydroxide. The complete sepa- 
 ration of the metals is possible only when the sepa- 
 ration of the dioxide is delayed till most of the iron 
 is precipitated." The electrolysis in the cold is not 
 favorable ; the large amount of ammonium carbonate, 
 or ammonia formed in the decomposition of the ex- 
 cessive ammonium oxalate dissolves the precipitated 
 dioxide. " The rapid dissociation of ammonium oxa- 
 late when heated, however, gives a simple means of 
 delaying, or entirely preventing, the formation of a 
 manganese precipitate during the electrolysis." The 
 solution containing the two metals is treated with 56 
 grams of ammonium oxalate, and while hot is acted 
 upon with a current giving 1 5-20 c.c. of electrolytic 
 gas per minute. Treat the iron deposit as directed 
 on p. 78. Boil the liquid, poured off from the iron, 
 with sodium hydroxide, to decompose the ammonium 
 carbonate present, after which add sodium carbonate 
 and a little sodium hypochlorite. The manganese 
 is precipitated as dioxide, and finally weighed as the 
 protosesquioxide. Nickel and manganese are sepa- 
 rated from each other in a similar manner. Cobalt 
 and zinc, when present with manganese, are separated 
 
SEPARATION OF IRON FROM ZINC. IO5 
 
 from it by a current of 10 c.c. oxy-hydrogen gas per 
 minute, acting in the cold. Oxalic acid is added 
 toward the end of the reduction to redissolve any 
 separated manganese dioxide. 
 
 To separate iron from zinc, add 1-3 c.c. of a solu- 
 tion of potassium oxalate (i : 3) and 3-4 grams of 
 ammonium oxalate to their solution, and electrolyse 
 the liquid with a current liberating 10-12 c.c. electro- 
 lytic gas per minute. The zinc is deposited first, and 
 no difficulty is experienced, providing its quantity is 
 less than one-third that of the iron present. Classen 
 provides for this condition by adding a weighed 
 amount of pure ferrous ammonium sulphate in excess. 
 The same chemist precipitates iron and cobalt simul- 
 taneously from their double oxalate solution (condi- 
 tions as above), takes the combined weight of the 
 metals, dissolves them in acid and determines the iron 
 by titration ; the cobalt is found by difference. Nickel 
 and iron are also deposited together (same as cobalt 
 and iron) as an alloy, which is weighed, then dissolved 
 in concentrated hydrochloric acid, the iron oxidized, 
 and the ferric solution titrated with a stannous chloride 
 solution. It will be observed that an electrolytic 
 separation of zinc from cobalt and nickel, and 'the 
 latter from each other is wanting. 
 
 The writer would recommend the following course 
 
 in separating the metals of this group : Separate the 
 
 iron from the manganese, zinc, nickel and cobalt, by 
 
 precipitation with barium carbonate. Dissolve the 
 
 H 
 
IO6 ELECTRO-CHEMICAL ANALYSIS. 
 
 iron precipitate in citric acid, and electrolyse the 
 solution according to the directions given upon page 
 79. The filtrate, containing the zinc, manganese, 
 nickel and cobalt, together with a little barium salt, 
 is carefully treated with just sufficient dilute sulphuric 
 acid to remove the barium. After filtering, electrolyse 
 the filtrate in a platinum dish, connected with the 
 anode of a battery, yielding 35 c.c. of electrolytic 
 gas per minute. A weighed piece of platinum foil 
 will answer for the cathode. The manganese is de- 
 posited as dioxide (p. 76) ; the other metals remain dis- 
 solved and can only be separated by one of the usual 
 gravimetric methods. This course proved quite satis- 
 factory in the analysis of the mineral franklinite, where, 
 after having obtained the iron and manganese as 
 described, the zinc was also determined electrolytically 
 in the liquid poured off from the manganese deposit. 
 If the solution containing these two metals be very 
 slightly acid with sulphuric acid, they can be precipi- 
 tated simultaneously the zinc at the cathode, and 
 manganese dioxide at the anode. 
 
 Iron can be further separated, in citrate solution, 
 from aluminium, chromium and titanium (p. 79). 
 The deposition should occur in a cold solution, with 
 a current, liberating 12 c.c. electrolytic gas per minute. 
 This method will also serve to separate iron from 
 chromium and phosphoric acid. Classen separates 
 iron, cobalt, nickel and zinc from manganese, chromium 
 and aluminium by electrolysing their hot oxalate solu- 
 
SEPARATION OF MERCURY AND PALLADIUM. IO/ 
 
 tion in the presence of a large excess of ammonium 
 oxalate. The first four are deposited as metals, while 
 the manganese dioxide upon the anode has carried 
 with it some chromium, and should be dissolved, and 
 the manganese reprecipitated by sodium hydroxide 
 and sodium hypochlorite (p. 104). The main solu- 
 tion from the metals is digested until the excess of 
 ammonia is expelled, when the aluminium hydroxide 
 is filtered off; the chromate solution, then reduced 
 with hydrogen sulphide in the presence of an acid, is 
 precipitated with ammonium, hydroxide. In all cases 
 where it is necessary to add oxalic acid to redissolve 
 the aluminium hydroxide, or manganese dioxide, the 
 acid should be introduced without the interruption of 
 the current. When phosphoric acid is present with 
 the iron and manganese it will be found in the liquid 
 (oxalate) from which the metals have been previously 
 precipitated, and may be removed as ammonium 
 magnesium phosphate. 
 
 Little can be said relative to the separation of the 
 rarer metals ; further investigation is required in this 
 direction. 
 
 Quite recent experiments, made in this laboratory, 
 show that mercury and palladium can be separated if 
 present together in a solution containing not less than 
 3 grams of potassium cyanide for 0.2-0.4 gram of the 
 metals. The current necessary here may vary from 
 
IO8 ELECTRO-CHEMICAL ANALYSIS. 
 
 0.08 c.c. 0.22 c.c. electrolytic gas per minute. Not- 
 withstanding that cadmium and silver are easily 
 precipitated from their double cyanide solutions, it is 
 impossible to separate them from palladium. In fact, 
 they appear to hasten the deposition of the latter 
 metal. 
 
 Mercury, silver and cadmium, furthermore, can be 
 separated from solutions containing excess of alkaline 
 cyanide together with tungstic and molybdic acids, 
 without carrying down any of the latter. The con- 
 ditions most favorable for these separations are 
 perfectly similar to those just given above (pp. 96, 98, 
 101) for the separation of these metals from arsenic 
 (Am. Ch. Jr., 12, p. 428). 
 
 3. OXIDATIONS BY MEANS OF THE 
 ELECTRIC CURRENT. 
 
 When natural sulphides, e.g., chalcopyrite, marca- 
 site, etc., are exposed to the action of a strong current 
 in the presence of a sufficient quantity of potassium 
 hydroxide their sulphur will be quickly and fully 
 oxidized to sulphuric acid (Jr. Fr. Ins., April, 1889, 
 Ber., 22, 1019). The metals (iron, copper, etc.) orig- 
 inally present in the mineral separate as oxides and 
 metal on dissolving the fused alkaline mass in water. 
 This method of oxidation eliminates many other 
 disagreeable features of the old methods. Its rapidity 
 
OXIDATIONS BY MEANS OF CURRENT. 1 09 
 
 and accuracy entitle it to the following brief descrip- 
 tion : 
 
 Place about 20 grams of caustic potash in a nickel 
 crucible i^ inches high and i%& inches wide. Apply 
 heat from a Bunsen burner until the water has been 
 almost entirely expelled, when the flame is lowered so 
 that the temperature is just sufficient to retain the 
 alkali in a liquid condition. The crucible is next 
 connected with the negative pole of a battery, and the 
 sulphide to be oxidized is placed upon the fused 
 alkali. As some natural sulphides part with a portion 
 of their sulphur at a comparatively low temperature, 
 it is advisable to allow the alkali to cool so far that a 
 scum forms over its surface, before adding the 
 weighed mineral. 
 
 The heavy platinum wire, attached to the anode, 
 extends a short distance below the surface of the 
 fused mass. When the current passes a lively action 
 ensues, accompanied with some spattering. To pre- 
 vent loss from this source, always place a perforated 
 watch-crystal over the crucible. After the current 
 has acted for 10-20 minutes interrupt it. When the 
 crucible and its contents are cold place them in about 
 200 c.c. of water, to dissolve out the excess of alkali 
 and alkaline sulphate. Filter. Invariably examine 
 the residue for sulphur, by dissolving it in nitric acid 
 and then testing with barium chloride. The alkaline 
 filtrate is carefully acidulated with hydrochloric acid, 
 and after digesting for some time, is precipitated with 
 
1 10 ELECTRO-CHEMICAL ANALYSIS. 
 
 a boiling solution of barium chloride. When the 
 hydrochloric acid is first added, care should be taken 
 to observe whether hydrogen sulphide or sulphur 
 dioxide is liberated. If the oxidation is incomplete 
 sulphur also makes its appearance as a white tur- 
 bidity. The caustic potash employed in these oxida- 
 tions should always be examined for sulphur and 
 other impurities. As it is difficult to obtain alkali 
 perfectly free from sulphur compounds, a weighed 
 portion should be taken and its quantity of sulphur 
 deducted from that actually found in the analysis. 
 
 The arrangement of apparatus employed in the 
 oxidations just outlined is represented in Fig. 25. 
 The crucible A is supported by a stout copper wire 
 bent as indicated, and held in position by a binding 
 screw attached to the base of a filter stand. The arm 
 of the latter carries a second binding screw holding 
 the platinum anode in position. While the platinum 
 rod is generally the positive electrode, it is best to 
 make it the negative pole for at least a part of the 
 time during which the current acts. This is advisable 
 because in many of the decompositions metals are 
 precipitated upon the sides of the crucibles, and can 
 readily enclose unattacked sulphide, so that by revers- 
 ing the current (the poles) any precipitated metal will 
 be detached, and the enclosed sulphide be again 
 brought into the field of oxidation. Cinnabar is a 
 sulphide which has a tendency to mass together, and 
 it could only be decomposed and its sulphur thor- 
 
OXIDATIONS BY MEANS OF CURRENT. 
 
112 ELECTRO-CHEMICAL ANALYSIS. 
 
 oughly oxidized by reversing the current every few 
 minutes. To reverse the current use the contrivance 
 C\ this is nothing more than a square block of wood 
 fastened to the top of the table T, by a screw or nail. 
 The four depressions (x) in it contain a few drops of 
 mercury, into which the side binding screws (a) pro- 
 ject. The mercury cups are made to communicate 
 with each other by a cap of wood, D, carrying two 
 metallic wires, which pass through it and project a 
 slight distance on its lower side. By raising the cap 
 and turning it so that the wires are vertical (J) or 
 horizontal (*->), the crucible or the platinum wire 
 extending into the fused mass can be made the anode 
 or cathode in a few seconds. E is a Kohlrausch 
 amperemeter (Fig. 15), and R the resistance frame 
 
 ( Fi g- 13)- 
 
 Storage batteries furnish the most satisfactory cur- 
 rent for work of this character. In the sketch the 
 cells stand beneath the table ; the wire from the anode 
 passes through a hole in the table top, and is attached 
 to one of the binding posts of the block C, while the 
 positive wire is attached to a binding post at the end 
 of the table top, and from here it passes to the resist- 
 ance frame R y where it is fixed by an ordinary metal- 
 lic clamp. 
 
 For most purposes the strength of current need not 
 exceed 11.5 amperes per minute; however, it may 
 be necessary occasionally to increase it to 4 amperes 
 per minute. Pyrite, FeS 2 , is even then not completely 
 
OXIDATIONS BY MEANS OF CURRENT. 113 
 
 decomposed. This particular case requires the addi- 
 tion of a quantity of cupric oxide equal in weight to 
 the pyrite, and a current of the strength last indi- 
 cated before all of its sulphur is fully converted into 
 sulphuric acid. 
 
 By increasing the number of crucibles it will be 
 possible to conduct at least from four to six of these 
 decompositions simultaneously, and by using a volu- 
 metric method for estimating the sulphuric acid, a 
 sulphur determination can easily be executed in forty 
 minutes. 
 
 Experience has demonstrated that 0.1-0.2 gram of 
 material will require about 20-25 grams of caustic 
 potash. 
 
 The arsenic in minerals is rapidly oxidized to 
 arsenic acid by this method. 
 
 Chromite also seems to be rapidly decomposed 
 when subjected to this treatment. Several quantita- 
 tive experiments have been carried out, and the 
 results obtained were very satisfactory. 
 
INDEX. 
 
 AMPERE, 14 
 i* Amperemeter, 31 
 Anions, 9 
 Anode, 9 
 
 Antimony, determination of, 87-89 
 separation from arsenic, 102 
 
 bismuth, 99 
 
 copper, 92, 94 
 
 lead, 99 
 
 mercury, 98 
 
 silver, 101 
 
 tin, 102 
 Arsenic, determination of, 89 
 
 separation from antimony, 102 
 
 bismuth, 99 
 
 cadmium, 96 
 
 copper, 92 
 
 lead, 99 
 
 mercury, 98 
 
 silver, 101 
 
 tin, 103 
 
 D ATTERY, Bunsen, 19 
 *-* Crowfoot, 17 
 Daniell, 17 
 Grenet, 14 
 Grove, 19 
 Leclanche 16 
 Meidinger, 17 
 storage, 24 
 Bismuth, determination of, 59-61 
 
 separation from aluminium, antimo- 
 ny, arsenic, cadmium, chromium, 
 cobalt, iron, manganese, nickel, 
 tin, uranium, zinc, 98-99 
 separation from copper, 91 
 
 CADMIUM, determination of, 54-57 
 ^ separation from aluminium, anti- 
 mony, arsenic, bismuth, cobalt, 
 iron, manganese, mercury, nickel, 
 silver, tin, uranium, zinc, 94-97 
 separation from copper, 90 
 
 molybdenum and tungsten, 
 
 108 
 Cathions, 9 
 
 Cathode, 9 
 
 Cobalt, determination of, 72-75 
 separation from bismuth, 99 
 
 cadmium, 94, 95 
 
 copper, 91 
 
 iron, 105, 106 
 
 manganese, 104 
 
 mercury. 97, 98 
 
 silver, 101 
 Copper, determination of, 47-54 
 
 separation from aluminium, 90, 91 
 
 antimony, 92, 94 
 
 arsenic, 93 
 
 bismuth, cobalt, iron lead, 
 nickel, uranium, zinc, 91 
 
 cadmium, 90 
 
 manganese, 92 
 
 mercury, 97 
 
 silver, 100 
 
 tin, 94 
 Current, action upon compounds, 10 
 
 ELECTROLYSIS, defined, 9 
 
 "OLD, determination of, 85 
 
 LJISTORICAL account, 32-46 
 
 IRON, determination of, 78-80 
 separation from aluminium, 106 
 bismuth, 99 
 cadmium, 94 
 cobalt, 105 
 copper, 91 
 lead, 99 
 
 manganese, 103 
 mercury, 97 
 nickel, 105, 106 
 silver, 64 
 zinc, 105 
 
INDEX. 
 
 EAD, determination of, 62-63 
 ' separation from aluminium, 99 
 antimony, 99 
 arsenic, 99 
 cadmium, 99 
 cobalt, 99 
 copper, 91, 99 
 iron, 99 
 
 mercury, 97, 99 
 nickel, 99 
 silver, 99, 100 
 uranium, 99 
 zinc, 99 
 
 AGNETO-machines, 21 
 
 M 
 
 Manganese, determination of, 75-78 
 
 separation from aluminium, 105, 106 
 bismuth, 99 
 cadmium, 94 
 cobalt, 106 
 copper, 92 
 iron, 103, 105 
 mercury, 97 
 nickel, 106 
 zinc, 106 
 Mercury, determination of, 57-59 
 
 separation from aluminium, cad- 
 mium, copper, iron, lead, 97 
 antimony, arsenic, tin, 98 
 from cobalt, nickel, zinc, 97, 98 
 molybdenum, 108 
 palladium, 107 
 tungsten, 108 
 Molybdenum, determination of, 84 
 
 separation from cadmium, mercury 
 and silver, 108 
 
 NICKEL, determination of, 72, 75 
 separation from aluminium, 106 
 bismuth, 99 
 cadmium, 94 
 cobalt, 94, 95 
 copper, 91 
 iron, 105, 106 
 lead, 99 
 
 manganese, 106 
 mercury, 97, 98 
 silver, 101 
 
 O HM ' '.3 
 
 ^-s Osmium, 37 
 
 Oxidations by means of the current, 108 
 
 DALLADIUM, determination of, 83 
 
 separation from mercury, 107 
 Platinum, determination of, 82, 83 
 Phosphoric acid, separation, etc., 
 
 103, 107 
 
 R 
 
 ESISTANCE coils and frames, 
 
 26, 27, 28 
 
 SILVER, determination of, 63-67 
 separation from aluminium, copper, 
 iron, lead, manganese, uranium, 
 
 100 
 antimony, arsenic, cobalt, 
 
 nickel, tin, zinc, 101 
 cadmium, 94 
 
 molybdenum and tungsten, 
 1 08 
 Sulphur, oxidation of, 108, 109 
 
 'TANGENT galvanometer, 30 
 
 Thallium, determination of, 81 
 Thermo-electric pile, 21 
 Tin, determination of, 85, 86 
 
 separation from antimony, 102 
 
 arsenic, 103 
 
 bismuth, 99 
 
 cadmium, 96 
 
 copper, 94 
 
 lead, 99 
 
 mercury, 98 
 
 U 
 
 RANIUM, determination of, 80 
 
 fOLT, 14 
 
 Voltameter, 29 
 
 '7INC, determination of, 67-72 
 ^ separation from aluminium, 106 
 bismuth, 99 
 cadmium, 94, 95, 96 
 copper, 91 
 iron, 105 
 lead, 99 
 
 manganese, 106 
 mercury, 97, 98 
 silver, 101 
 
JUST PUBLISHED. 
 
 FUEL AND ITS APPLICATIONS, 
 
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 On the various Branches of Medicine and Surgery. 
 
 Can be used by Students of any College. 
 Price of each, Handsome Cloth, $3.00. Full Leather, $3.50. 
 
 The object of this series is to furnish good manuals 
 for the medical student, that will strike the medium 
 between the compend on one hand and the prolix text- 
 book on the other to contain all that is necessary for 
 the student, without embarrassing him with a flood of 
 theory and involved statements. They have been pre- 
 pared by well-known men, who have had large experience 
 as teachers and writers, and who are, therefore, well 
 informed as to the needs of the student. 
 
 Their mechanical execution is of the best good type 
 and paper, handsomely illustrated whenever illustrations 
 are of use, and strongly bound in uniform style. 
 
 Each book is sold separately at a remarkably low 
 price, and the immediate success of several of the 
 volumes shows that the series has met with popular 
 favor. 
 
 No. 1. SURGERY. 236 Illustrations. 
 A Manual of the Practice of Surgery. By WM. J. 
 
 WALSHAM, M.D., Asst. Surg. to, and Demonstrator of 
 
 Surg. in, St. Bartholomew's Hospital, London, etc. 
 
 228 Illustrations. 
 
 Presents the introductory facts in Surgery in clear, precise 
 language, and contains all the latest advances in Pathology, 
 Antiseptics, etc. 
 
 " It aims to occupy a position midway between the pretentious 
 manual and the cumbersome System of Surgery, and its general 
 character may be summed up in one word practical." The Medi- 
 cal Bulletin. 
 
 " Walsham, besides being an excellent surgeon, is a teacher in 
 its best sense, and having had very great experience in the 
 preparation of candidates for examination, and their subsequent 
 professional career, may be relied upon to have carried out his 
 work successfully. Without following out in detail his arrange- 
 ment, which is excellent, we can at once say that his book is an 
 embodiment of modern ideas neatly strung together, with an amount 
 of careful organization well suited to the candidate, and, indeed, to 
 the practitioner." British Medical Journal. 
 
 Price of each Book, Cloth, $3.00 ; Leather, $3.50. 
 
THE NEW SERIES OF MANUALS. 
 
 No. 2. DISEASES OP WOMEN. 15O Illus. 
 
 NEW EDITION. 
 
 The Diseases of Women. Including Diseases of the 
 Bladder and Urethra. By DR. F. WINCKEL, Professor 
 of Gynaecology and Director of the Royal University 
 Clinic for Women, in Munich. Second Edition. Re- 
 vised and Edited by Theophilus Parvin, M.D., 
 Professor of Obstetrics and Diseases of Women and 
 Children in Jefferson Medical College. 150 Engrav- 
 ings, most of which are original. 
 " The book will be a valuable one to physicians, and a safe and 
 
 satisfactory one to put into the hands of students. It is issued in a 
 
 neat and attractive form, and at a very reasonable price." Boston 
 
 Medical and Surgical Journal. 
 
 No. 3. OBSTETRICS. 227 Illustrations. 
 A Manual of Midwifery. By ALFRED LEWIS GALABIN, 
 M.A., M.D., Obstetric Physician and Lecturer on Mid- 
 wifery and the Diseases of Women at Guy's Hospital, 
 London; Examiner in Midwifery to the Conjoint 
 Examining Board of England, etc. With 227 Illus. 
 " This manual is one we can strongly recommend to all who 
 desire to study the science as well as the practice of midwifery. 
 Students at the present time not only are expected to know the 
 principles of diagnosis, and the treatment of the various emergen- 
 cies and complications that occur in the practice of midwifery, but 
 find that the tendency is for examiners to ask more questions 
 relating to the science of the subject than was the custom a few 
 years ago. * * * The general standard of the manual is high ; 
 and wherever the science and practice of midwifery are well taught 
 it will be regarded as one of the most important text-books on the 
 subject" London Practitioner. 
 
 No. 4. PHYSIOLOGY. Fourth Edition. 
 
 321 ILLUSTRATIONS AND A GLOSSARY. 
 A Manual of Physiology. By GERALD F. YEO, M.D., 
 F.R.C.S., Professor of Physiology in King's College, 
 London. 321 Illustrations and a Glossary of Terms. 
 Fourth American from second English Edition, revised 
 and improved. 758 pages. 
 
 This volume was specially prepared to furnish students with a 
 new text-book of Physiology, elementary so far as to avoid theories 
 which have not borne the test of time and such details of methods 
 as are unnecessary for students in our medical colleges. 
 
 " The brief examination I have given it was so favorable that I 
 
 B'aced it in the list of text-books recommended in the circular of the 
 niversity Medical College." Prof. Lewis A. Stimson, M.D., 
 3^ East 33d Street, New York. 
 
 Price of each Book, Cloth, $3.00; Leather, $3.50. 
 
THE NEW SERIES OF MANUALS. 
 
 No. 5. ORGANIC CHEMISTRY. 
 
 Or the Chemistry of the Carbon Compounds. By Prof. 
 VICTOR VON RICHTER, University of Breslau. Au- 
 thorized translation, from the Fourth German Edition. 
 By EDGAR F. SMITH, M.A., PH.D. ; Prof, of Chemistry 
 in University of Pennsylvania; Member of the Chem. 
 Socs. of Berlin and Paris. 
 
 " I must say that this standard treatise is here presented in a 
 remarkably compendious shape." y. W. Holland, M.D., Professor 
 of Chemistry, Jefferson Medical College, Philadelphia. 
 
 " This work brings the whole matter, in simple, plain language, 
 to the student in a clear, comprehensive manner. The whole 
 method of the work is one that is more readily grasped than that of 
 older and more famed text-books, and we look forward to the time 
 when, to a great extent, this work will supersede others, on the 
 score of its better adaptation to the wants of both teacher and 
 student." Pharmaceutical Record. 
 
 " Prof, von Richter's work has the merit of being singularly 
 clear, well arranged, and for its bulk, comprehensive. Hence, it 
 will, as we find it intimated in the preface, prove useful not merely 
 as a text-book, but as a manual of reference." The Chemical 
 News, London. 
 
 No. 6. DISEASES OP CHILDREN. 
 
 SECOND EDITION. 
 
 A Manual. By J. F. GOODHART, M.D., Phys. to the 
 Evelina Hospital for Children ; Asst. Phys. to 
 Guy's Hospital, London. Second American Edition. 
 Edited and Rearranged by Louis STARR, M.D., Clinical 
 Prof, of Dis. of Children in the Hospital of the Univ. 
 of Pennsylvania, and Physician to the Children's Hos- 
 pital, Phila. Containing many new Prescriptions, a list 
 of over 50 Formulae, conforming to the U. S. Pharma- 
 copoeia, and Directions for making Artificial Human 
 Milk, for the Artificial Digestion of Milk, etc. Illus. 
 
 " The author has avoided the not uncommon error of writing a 
 book on general medicine and labeling it ' Diseases of Children,' 
 but has steadily kept in view the diseases which seemed to be 
 incidental to childhood, or such points in disease as appear to be so 
 peculiar to or pronounced in children as to justify insistence upon 
 them. * * * A safe and reliable guide, and in many ways 
 admirably adapted to the wants of the student and practitioner." 
 American Journal of Medical Science. 
 
 Price of each Book. Cloth, $3.00 ; Leather, $3.50. 
 
THE NEW SERIES OF MANUALS. 
 
 No. 6. Goodhart and Starr : Continued. 
 
 " Thoroughly individual, original and earnest, the work evi- 
 dently of a close observer and an independent thinker, this book, 
 though small, as a handbook or compendium is by no means made 
 up of bare outlines or standard facts." The Therapeutic Ga- 
 zette. 
 
 " As it is said of some men, so it might be said of some books, 
 that they are 'born to greatness.' This new volume has, we 
 believe, a mission, particularly in the hands of the younger 
 members of the profession. In these days of prolixity in medical 
 literature, it is refreshing to meet with an author who knows both 
 what to say and when he has said it. The work of Dr. Goodhart 
 (admirably conformed, by Dr. Starr, to meet American require- 
 ments) is the nearest approach to clinical teaching without the 
 actual presence of clinical material that we have yet seen." New 
 York Medical Record. 
 
 No. 7. PRACTICAL THERAPEUTICS. 
 
 FOURTH EDITION, WITH AN INDEX OF DISEASES. 
 
 Practical Therapeutics, considered with reference to 
 Articles of the Materia Medica. Containing, also, an 
 Index of Diseases, with a list of the Medicines 
 applicable as Remedies. By EDWARD JOHN WARING, 
 M.D., F.R.C.P. Fourth Edition. Rewritten and Re- 
 vised by DUDLEY W. BUXTON, M.D., Asst. to the Prof, 
 of Medicine at University College Hospital. 
 
 " We wish a copy could be put in the hands of every Student or 
 Practitioner in the country. In our estimation, it is the best book 
 of the kind ever written. 'N. Y. Medical Journal. 
 
 No. 8. MEDICAL JURISPRUDENCE AND 
 TOXICOLOGY. 
 
 NEW, REVISED AND ENLARGED EDITION. 
 
 By John J. Reese, M.D., Professor of Medical Jurispru- 
 dence and Toxicology in the University of Pennsyl- 
 vania ; President of the Medical Jurisprudence Society 
 of Phila. ; 2d Edition, Revised and Enlarged. 
 
 " This admirable text-book." Amer.Jour. of Med. Sciences. 
 
 " We lay this volume aside, after a careful perusal of its pages, 
 with the profound impression that it should be in the hands of every 
 
 doctor and lawyer. It fully meets the wants of all students 
 
 He has succeeded in admirably condensing into a handy volume all 
 the essential points." Cincinnati Lancet and Clinic. 
 
 Price of each Book, Cloth, $3,00 ; Leather, $3.50. 
 
6 STUDENTS' TEXT-BOOKS AND MANUALS. 
 
 ANATOMY. 
 
 Macalister's Human Anatomy. 816 Illustrations. A new 
 Text-book for Students and Practitioners, Systematic and Topo- 
 graphical, including the Embryology, Histology and Morphology 
 of Man. With special reference to the requirements of 
 Practical Surgery and Medicine. With 816 Illustrations, 
 400 of which are original. Octavo. Cloth, 7.50; Leather, 8.50 
 
 Ballou's Veterinary Anatomy and Physiology. Illustrated. 
 By Wm. R. Ballou, M.D., Professor of Equine Anatomy at New 
 York College of Veterinary Surgeons. 29 graphic Illustrations. 
 I2mo. Cloth, i.oo; Interleaved for notes, 1.25 
 
 Holden's Anatomy. A manual of Dissection of the Human 
 Body. Fifth Edition. Enlarged, with Marginal References and 
 over 200 Illustrations. Octavo. Cloth, 5.00; Leather, &oo 
 
 Bound in Oilcloth, for the Dissecting Room, $4.50. 
 
 " No student of Anatomy can take up this book without being 
 pleased and instructed. Its Diagrams are original, striking and 
 suggestive, giving more at a glance than pages of text description. 
 * * * The text matches the illustrations in directness of prac- 
 tical application and clearness of detail." Ne^v York Medical 
 Record. 
 
 Holden's Human Osteology. Comprising a Description of the 
 Bones, with Colored Delineations of the Attachments of the 
 Muscles. The General and Microscopical Structure of Bone and 
 its Development. With Lithographic Plates and Numerous Illus- 
 trations. Seventh Edition. 8vo. Cloth, 6.00 
 
 Holden's Landmarks, Medical and Surgical. 4th ed. Clo., 1.25 
 
 Heath's Practical Anatomy. Sixth London Edition. 24 Col- 
 ored Plates, and nearly 300 other Illustrations. Cloth, 5.00 
 
 Potter's Compend of Anatomy. Fourth Edition. 117 Illus- 
 trations. Cloth, i.oo; Interleaved for Notes, 1.25 
 
 CHEMISTRY. 
 
 Bartley's Medical Chemistry. Second Edition. A text-book 
 prepared specially for Medical, Pharmaceutical and Dental Stu- 
 dents. With 50 Illustrations, Plate of Absorption Spectra and 
 Glossary of Chemical Terms. Revised and Enlarged. Cloth, 2. 50 
 
 Trimble. Practical and Analytical Chemistry. A Course in 
 Chemical Analysis, by Henry Trimble, Prof, of Analytical Chem- 
 istry in the Phila. College of Pharmacy. Illustrated. Third 
 Edition. 8vo. Cloth, 1.50 
 
 JH&" See pages 2 to j for list of Students' Manuals. 
 
STUDENTS' TEXT-BOOKS AND MANUALS. 7 
 
 Chemistry : Continued. 
 
 Bloxam's Chemistry, Inorganic and Organic, with Experiments. 
 Seventh Edition. Enlarged and Rewritten. 330 Illustrations* 
 
 Cloth, 4.50 ; Leather, 5.50 
 
 Richter's Inorganic Chemistry. A text-book for Students. 
 Third American, from Fifth German Edition. Translated by 
 Prof. Edgar F. Smith, PH.D. 89 Wood Engravings and Colored 
 Plate of Spectra. Cloth, 2.00 
 
 Richter's Organic Chemistry, or Chemistry of the Carbon 
 Compounds. Illustrated. Cloth, 3.00 ; Leather, 3.50 
 
 Symonds. Manual of Chemistry, for the special use of Medi- 
 cal Students. By BKANDRKTH SYMONDS, A.M., M.D., Asst. 
 Physician Roosevelt Hospital, Out- Patient Department; Attend- 
 ing Physician Northwestern Dispensary, New York. i2mo. 
 
 Cloth, 2.00 ; Interleaved for Notes, 2.40 
 
 Tidy. Modern Chemistry, ad Ed. Cloth, 5.50 
 
 Leffmann's Compend of Chemistry. Inorganic and Organic. 
 Including Urinary Analysis and the Sanitary Examination of 
 Water. New Edition. Cloth, i.oo; Interleaved for Notes, 1.25 
 
 Muter. Practical and Analytical Chemistry. Second Edi- 
 tion. Revised and Illustrated. Cloth, 2.00 
 
 Holland. The Urine, Common Poisons, and Milk Analysis, 
 Chemical and Microscopical. For Laboratory Use. 3d 
 Edition, Enlarged. Illustrated. Cloth, i.oo 
 
 Van Niiys. Urine Analysis. Illus. Cloth, 2.00 
 
 Wolff 's Applied Medical Chemistry. By Lawrence Wolff, 
 M.D.,Dem. of Chemistry in Jefferson Medical College. Clo.,i.oo 
 
 CHILDREN. 
 
 Goodhart and Starr. The Diseases of Children. Second 
 Edition. By T. F. Goodhart, M.D., Physician to the Evelina 
 Hospital for Children ; Assistant Physician to Guy's Hospital, 
 London. Revised and Edited by Louis Starr, M.D., Clinical 
 Professor of Diseases of Children in the Hospital of the Univer- 
 sity of Pennsylvania; Physician to the Children's Hospital, 
 Philadelphia. Containing many Prescriptions and Formulae, 
 conforming to the U. S. Pharmacopoeia, Directions for making 
 Artificial Human Milk, for the Artificial Digestion of Milk, etc. 
 Illustrated. Cloth, 3.00; Leather, 3.50 
 
 Hatfield. Diseases of Children. By M. P. Hatfield, M.D., 
 Professor of Diseases of Children, Chicago Medical College. 
 i2mo. Cloth, i.oo; Interleaved, 1.25 
 
 Day. On Children. A Practical and Systematic Treatise. 
 Second Edition. 8vo. 752 pages. Cloth, 3.00; Leather, 4.00 
 
 9&~ See pages 14 and rf for list of f Quiz- Compends f 
 
8 STUDENTS' TEXT-BOOKS AND MANUALS. 
 
 Children: Continued. 
 
 Meigs and Pepper. The Diseases of Children. Seventh 
 Edition. 8vo. Cloth, 5.00; Leather, 6.00 
 
 Starr. Diseases of the Digestive Organs in Infancy and 
 Childhood. With chapters on the Investigation of Disease, 
 and on the General Management of Children. By Louis Starr, 
 M.D., Clinical Professor of Diseases of Children in the Univer- 
 sity of Pennsylvania; with a section on Feeding, including special 
 Diet Lists, etc. Illus. Cloth, 2.50 
 
 DENTISTRY. 
 
 Fillebrown. Operative Dentistry. 330 Illus. Cloth, 2.50 
 
 Flagg's Plastics and Plastic Filling. 3d Ed. Preparing. 
 
 Gorgas. Dental Medicine. A Manual of Materia Medica and 
 Therapeutics. Third Edition. Cloth, 3.50 
 
 Harris. Principles and Practice of Dentistry. Including 
 Anatomy, Physiology, Pathology, Therapeutics, Dental Surgery 
 and Mechanism. Twelfth Edition. Revised and enlarged by 
 Professor Gorgas. 1028 Illustrations. Cloth, 7.00 ; Leather, 8.00 
 
 Richardson's Mechanical Dentistry. Fifth Edition. 569 
 Illustrations. 8vo. Cloth, 4.50; Leather, 5.50 
 
 Stocken's Dental Materia Medica. Third Edition. Cloth, 2.50 
 
 Taft's Operative Dentistry. Dental Students and Practitioners. 
 Fourth Edition, too Illustrations. Cloth, 4.25 ; Leather, 5.00 
 
 Talbot. Irregularities of the Teeth, and their Treatment. 
 Illustrated. 8vo. Cloth, 1.50 
 
 Tomes' Dental Anatomy. Third Ed. 191 Illus. Cloth, 4.00 
 
 Tomes' Dental Surgery. 3d Edition. Revised. 292 Illus. 
 772 Pages. Cloth, 5.00 
 
 DICTIONARIES. 
 
 Gould's New Medical Dictionary. Containing the Definition 
 and Pronunciation of all words in Medicine, with many useful 
 Tables etc. ^ Dark Leather, 3.25 ; ^ Mor., Thumb Index 4.25 
 See last page. 
 
 Cleaveland's Pocket Medical Lexicon. 3ist Edition. Giving 
 
 correct Pronunciation and Definition. Very small pocket size. 
 
 Cloth, red edges .75 ; pocket-book style, i.oo 
 
 Longley's Pocket Dictionary. The Student's Medical Lexicon, 
 giving Definition and Pronunciation of all Terms used in Medi- 
 cine, with an Appendix giving Poisons and Their Antidotes, 
 Abbreviations used in Prescriptions, Metric Scale of Doses, etc. 
 24010. Cloth, i.oo; pocket-book style, 1.25 
 
 KiT See pages 2 to 5 for list of Students' Manuals. 
 
STUDENTS' TEXT-BOOKS AND MANUALS. 9 
 
 EYE. 
 
 Arlt. Diseases of the Eye. Including those of the Conjunc- 
 tiva, Cornea, Sclerotic, Iris and Ciliary Body. By Prof. Von 
 Arlt. Translated by Dr. Lyman Ware. Illus. 8vo. Cloth, 2.50 
 
 Hartridge on Refraction. 4th Ed. Cloth, 2.00 
 
 Meyer. Diseases of the Eye. A complete Manual for Stu- 
 dents and Physicians. 270 Illustrations and two Colored Plates. 
 8vo. Cloth, 4.50; Leather, 5.50 
 
 Fox and Gould. Compend of Diseases of the Eye and 
 Refraction. 2d Ed. Enlarged. 71 Illus. 39 Formulae. 
 
 Cloth, i. oo ; Interleaved for Notes, 1.25 
 
 ELECTRICITY. 
 
 Mason's Compend of Medical and Surgical Electricity. 
 With numerous Illustrations. 12010. Cloth, i.oo 
 
 HYGIENE. 
 
 Parkes' (Ed. A.) Practical Hygiene. Seventh Edition, en- 
 larged. Illustrated. 8vo. Cloth, 4.50 
 
 Parkes 1 (L. C.) Manual of Hygiene and Public Health. 
 i2mo. ' Cloth, 2.50 
 
 Wilson's Handbook of Hygiene and Sanitary Science. 
 Sixth Edition. Revised and Illustrated. Cloth, 2.75 
 
 MATERIA MEDICA AND THERAPEUTICS. 
 
 Potter's Compend of Materia Medica, Therapeutics and 
 
 Prescription 'Writing. Fifth Edition, revised and improved. 
 
 Cloth, i.oo; Interleaved for Notes, 1.25 
 
 Biddle's Materia Medica. Eleventh Edition. By the late 
 John B. Biddle, M.D., Professor of Materia Medica in Jefferson 
 Medical College, Philadelphia. Revised, and rewritten, by 
 Clement Biddle, M.D., Assist. Surgeon, U. S. N., assisted by 
 Henry Morris, M.D. 8vo., illustrated. Cloth, 4.25; Leather, 5.00 
 
 Headland's Action of Medicines. 9th Ed. 8vo. Cloth, 3.00 
 
 Potter. Materia Medica, Pharmacy and Therapeutics. 
 Including Action of Medicines, Special Therapeutics, Pharma- 
 cology, etc. Second Edition. Cloth, 4.00 ; Leather, 5,00 
 
 Starr, Walker and Powell. Synopsis of Physiological 
 Action of Medicines, based upon Prof. H. C. Wood's " Materia 
 Medica and Therapeutics." 3d Ed. Enlarged. Cloth, .75 
 
 "Waring. Therapeutics. With an Index of Diseases and 
 Remedies. 4th Edition. Revised. Cloth, 3.00; Leather, 3.50 
 4&- See pages 14 and ij for list of f Quit- Compends f 
 
10 STUDENTS' TEXT-BOOKS AND MANUALS. 
 
 MEDICAL JURISPRUDENCE. 
 Reese. A Text-book of Medical Jurisprudence and Toxi- 
 cology. By John J. Reese, M.D., Professor of Medical Juris- 
 prudence and Toxicology in the Medical Department of the 
 University of Pennsylvania ; President of the Medical Juris- 
 
 B-udence Society of Philadelphia; Physician to St. Joseph's 
 ospital ; Corresponding Member of The New York Medico- 
 legal Society. 2d Edition. Cloth, 3.00; Leather, 3.50 
 Woodman and Tidy's Medical Jurisprudence and Toxi- 
 cology. Chromo-Lithographic Plates and 116 Wood engravings. 
 
 Cloth, 7.50; Leather, 8.50 
 
 OBSTETRICS AND GYNAECOLOGY. 
 
 Byford. Diseases of Women. The Practice of Medicine and 
 Surgery, as applied to the Diseases and Accidents Incident to 
 Women. By W. H. Byford, A.M., M.D., Professor of Gynaecology 
 in Rush Medical College and of Obstetrics in the Woman's Med- 
 ical College, etc., and Henry T. Byford, M.D., Surgeon to the 
 Woman's Hospital of Chicago ; Gynaecologist to St. Luke's 
 Hospital, etc. Fourth Edition. Revised, Rewritten and En- 
 larged. With 306 Illustrations, over 100 of which are original. 
 Octavo. 832 pages. Cloth, 5.00 ; Leather, 6.00 
 
 Cazeaux and Tarnier's Midwifery. With Appendix, by 
 Munde. The Theory and Practice of Obstetrics ; including the 
 Diseases of Pregnancy and Parturition, Obstetrical Operations, 
 etc. By P. Cazeaux. Remodeled and rearranged, with revi- 
 sions and additions, by S. Tarnier, M.D., Professor of Obstetrics 
 and Diseases of Women and Children in the Faculty of Medicine 
 of Paris. Eighth American, from the Eighth French and First 
 Italian Edition. Edited by Robert J. Hess, M.D., Physician to 
 the Northern Dispensary, Philadelphia, with an appendix by 
 Paul F. Munde, M.D., Professor of Gynaecology at the N. Y. 
 Polyclinic. Illustrated by Chromo-Lithographs, Lithographs, 
 and other Full-page Plates, seven of which are beautifully colored, 
 and numerous Wood Engravings. Students' Edition. One 
 Vol., 8vo. Cloth, 5.00; Leather, 6.00 
 
 Lewers' Diseases of Women. A Practical Text-Book. 139 
 Illustrations. Second Edition. Cloth, 2.50 
 
 Parvin's Winckel's Diseases of Women. Second Edition. 
 Including a Section on Diseases of the Bladder and Urethra. 
 150 Illustrations. Revised. See page 3. 
 
 Cloth, 3.00; Leather, 3.50 
 
 Morris. Compend of Gynaecology. Illustrated. In Press. 
 
 Winckel's Obstetrics. A Text-book on Midwifery, includ- 
 ing the Diseases of Childbed. By Dr. F. Winckel, Professor 
 of Gynsecology, and Director of the Royal University Clinic for 
 Women, in Munich. Authorized Translation, by J. Clifton 
 Edgar, M.D., Lecturer on Obstetrics, University Medical Col- 
 lege, New York, with nearly 200 handsome illustrations, the 
 majority of which are original with this work. Octavo. 
 
 Cloth, 6.00; Leather, 7.00 
 
 Landis' Compend of Obstetrics. Illustrated. 4th edition, 
 enlarged. Cloth, i.oo; Interleaved for Notes, 1.25 
 
 t Pages 2 to 3 for list of New Manuals. 
 
STUDENTS' TEXT-BOOKS AND MANUALS. 11 
 
 Obstetrics and Gynacology : Continued. 
 
 Galabin's Midwifery. By A. Lewis Galabin, M.D., F.K.C.P. 
 227 Illustrations. Seepages. Cloth, 3.00; Leather, 3.50 
 
 Glisan's Modern Midwifery. 2d Edition. Cloth, 3.00 
 
 Rigby's Obstetric Memoranda. 4th Edition. Cloth, .50 
 
 Meadows' Manual of Midwifery. Including the Signs and 
 
 Symptoms of Pregnancy, Obstetric Operations, Diseases of the 
 
 Puerperal State, etc. 145 Illustrations. 494 pages. Cloth, 2.00 
 
 Swayne's Obstetric Aphorisms. For the use of Students 
 
 commencing Midwifery Practice. 8th Ed. 12010. Cloth, 1.25 
 
 PATHOLOGY. HISTOLOGY. BIOLOGY. 
 
 Bowlby. Surgical Pathology and Morbid Anatomy, for 
 Students. 135 Illustrations. i2mo. Cloth, 2.00 
 
 Davis' Elementary Biology. Illustrated. Cloth, 4.00 
 
 Gilliam's Essentials of Pathology. A Handbook for Students. 
 47 Illustrations. i2mo. Cloth, 2.00 
 
 *** The object of this book is to unfold to the beginner the funda- 
 
 mentals of pathology in a plain, practical way, and by bringing 
 
 them within easy comprehension to increase his interest in the study 
 
 of the subject. 
 
 Gibbes' Practical Histology and Pathology. Third Edition. 
 Enlarged. i2mo. Cloth, 1.75 
 
 Virchow's Post-Mortem Examinations. 2d Ed. Cloth, i.oo 
 
 PHYSIOLOGY. 
 
 Yeo's 
 dents 
 
 's Physiology. Fourth Edition. The most Popular Stu- 
 nts' Book. By Gerald F. Yeo, M.D., F.R.C.S., Professor of 
 Physiology in King's College, London. Small Octavo. 758 
 pages. 321 carefully printed Illustrations. With a Full 
 Glossary and Index. See Page 3. Cloth, 3.00; Leather, 3.50 
 
 Brubaker's Compend of Physiology. Illustrated. Fifth 
 Edition. Cloth, i.oo; Interleaved for Notes, 1.25 
 
 Stirling. Practical Physiology, including Chemical and Ex- 
 perimental Physiology. 142 Illustrations. Cloth, 2.25 
 
 Kirke's Physiology. New i2th Ed. Thoroughly Revised and 
 Enlarged. 502 Illustrations. Cloth, 4.00; Leather, 5.00 
 
 Landois' Human Physiology. Including Histology and Micro- 
 scopical Anatomy, and with special reference to Practical Medi- 
 cine. Third Edition. Translated and Edited by Prof. Stirling. 
 692 Illustrations. Cloth, 6.50; Leather, 7.50 
 
 " With this Text-book at his command, no student could fail in 
 
 his examination." Lancet. 
 
 Sanderson's Physiological Laboratory. Being Practical Ex- 
 ercises for the Student. 350 Illustrations. 8vo. Cloth, 5.00 
 
 Tyson's Cell Doctrine. Its History and Present State. Illus- 
 trated. Second Edition. Cloth, 2.00 
 
 Hff- Set pages 14 and 15 for list of 'Quiz-Commends f 
 
12 STUDENTS' TEXT-BOOKS AND MANUALS. 
 
 PRACTICE. 
 
 Taylor. Practice of Medicine. A Manual. By Frederick 
 Taylor, M.D., Physician to, and Lecturer on Medicine at, Guy's 
 Hospital, London; Physician to Evelina Hospital for Sick Chil- 
 dren, and Examiner in Materia Medica and Pharmaceutical 
 Chemistry, University of London. Cloth, 4.00 
 
 Roberts' Practice. New Revised Edition. A Handbook 
 of the Theory and Practice of Medicine. By Frederick T. 
 Roberts, M.D. ; M.R.C.P., Professor of Clinical Medicine and 
 Therapeutics in University College Hospital, London. Seventh 
 Edition. Octavo. Cloth, 5.50 ; Sheep, 6.50 
 
 Hughes. Compend of the Practice of Medicine. 4th Edi- 
 tion. Two parts, each, Cloth, i.oo; Interleaved for Notes, 1.25 
 PART i. Continued, Eruptive and Periodical Fevers, Diseases 
 
 of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver, 
 
 Kidneys, etc., and General Diseases, etc. 
 
 PART n. Diseases of the Respiratory System, Circulatory 
 
 System and Nervous System ; Diseases of the Blood, etc. 
 Physician's Edition. Fourth Edition. Including a Section 
 on Skin Diseases. With Index, i vol. Full Morocco, Gilt, 2.50 
 
 Tanner's Index of Diseases, and Their Treatment. Cloth, 3.00 
 
 PRESCRIPTION BOOKS. 
 
 Wythe's Dose and Symptom Book. Containing the Doses 
 and Uses of all the principal Articles of the Materia Medica, etc. 
 Seventeenth Edition. Completely Revised and Rewritten. Just 
 Ready. 321110. Cloth, i.oo; Pocket-book style, 1.25 
 
 Pereira's Physician's Prescription Book. Containing Lists 
 of Terms, Phrases, Contractions and Abbreviations used in 
 Prescriptions Explanatory Notes, Grammatical Construction of 
 Prescriptions, etc.., etc. By Professor Jonathan Pereira, M.D. 
 Sixteenth Edition. 32mo. Cloth, i.oo; Pocket-book style, 1.25 
 
 PHARMACY. 
 
 Stewart's Compend of Pharmacy. Based upon Remington's 
 Text-Book of Pharmacy. Second Edition, Revised. 
 
 Cloth, i.oo ; Interleaved for Notes, 1.25 
 
 SKIN DISEASES. 
 
 Anderson, (McCall) Skin Diseases. A complete Text-Book, 
 with Colored Plates and numerous Wood Engravings. 8vo. 
 Just Ready. Cloth, 4.50; Leather, 5.50 
 
 Van Harlingen on Skin Diseases. A Handbook of the Dis- 
 eases of the Skin, their Diagnosis and Treatment (arranged alpha- 
 betically). By Arthur Van Harlingen, M.D., Clinical Lecturer 
 on Dermatology, Jefferson Medical College ; Prof, of Diseases of 
 the Skin in the Philadelphia Polyclinic. 2d Edition. Enlarged. 
 With colored and other plates and illustrations. 12010. Cloth, 2.50 
 
 Bulkley. The Skin in Health and Disease. By L. Duncan 
 Bulkley, Physician to the N. Y. Hospital. Illus. Cloth, .50 
 
 JKS~ See pages 2 to 3 for list of New Manuals. 
 
STUDENTS' TEXT-BOOKS AND MANUALS. 13 
 
 SURGERY. 
 
 Caird and Cathcart. Surgical Handbook for the use of 
 Practitioners and Students. By F. MITCHELL CAIRO, M B., 
 F.R.C.S., and C. WALKER CATHCART, M.B., F.R.C.S., Asst. Sur- 
 geons Royal Infirmary. With over 200 Illustrations. 400 pages. 
 Pocket size. Leather covers, 2.50 
 
 Jacobson. Operations in Surgery. A Systematic Handbook 
 for Physicians, Students and Hospital Surgeons. By W. H. A. 
 Jacobson, B.A., Oxon. F.R.C.S. Eng. ; Ass't Surgeon Guy's Hos- 
 pital ; Surgeon at Royal Hospital for Children and Women, etc. 
 199 Illustrations. 1006 pages. 8vo. Cloth. 5.00; Leather, 6.00 
 
 Heath's Minor Surgery, and Bandaging. Ninth Edition. 142 
 Illustrations. 60 Formulae and Diet Lists. Cloth, 2.00 
 
 Horwitz's Compend of Surgery, including Minor Surgery, 
 Amputations, Fractures, Dislocations, Surgical Diseases, and the 
 Latest Antiseptic Rules, etc., with Differential Diagnosis and 
 Treatment. By ORVILLE HORWITZ, B.S., M.D., Demonstrator of 
 Surgery, Jefferson Medical College. 3d edition. Enlarged and 
 Rearranged. 91 Illustrations and 77 Formulae. 12010. 
 
 Cloth, i. oo ; Interleaved for the addition of Notes, 1.25 
 
 Walsham. Manual of Practical Surgery. For Students and 
 Physicians. By WM. J. WALSHAM, M.D., F.R.C.S., Asst. Surg. 
 to, and Dem. of Practical Surg. in, St. Bartholomew's Hospital, 
 Surgeon to Metropolitan Free Hospital, London. With 236 
 Engravings. See Page 2. Cloth, 3.00; Leather, 3.50 
 
 URINE, URINARY ORGANS, ETC. 
 
 Acton. The Reproductive Organs. In Childhood, Youth, 
 Adult Life and Old Age. Seventh Edition. Cloth, 2.00 
 
 Beale. Urinary and Renal Diseases and Calculous Disorders. 
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 trated. Third Edition. i2mo. Interleaved. Cloth, i.oo 
 
 Ralfe. Kidney Diseases and Urinary Derangements. 42 Illus- 
 trations. i2mo. 572 pages. Cloth, 2.75 
 
 Legg. On the Urine. A Practical Guide. 6th Ed. Cloth, .75 
 
 Marshall and Smith. On the Urine. The Chemical Analysis of 
 the Urine. By John Marshall, M.D., Chemical Laboratory, Univ. 
 of Penna; and Prof. E. F. Smith, PH.D. Col. Plates. Cloth, i.oo 
 
 Thompson. Diseases of the Urinary Organs. Eighth 
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 Tyson. On the Urine. A Practical Guide to the Examination 
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 Bright's Disease and Diabetes. Illus. Cloth, 3.50 
 
 Van Niiys, Urine Analysis. Illus. Cloth, a.oo 
 
 VENEREAL DISEASES. 
 
 Hill and Cooper. Student's Manual of Venereal Diseases, 
 with Formulae. Fourth Edition. i2mo. Cloth, i.oo 
 
 Durkee. On Gonorrhoea and Syphilis. Illus. Cloth, 3.50 
 4S- See pages 14 and 13 for list of ? Quiz-Compends .' 
 
NEW AND REVISED EDITIONS. 
 
 PQUIZ-COMPENDS? 
 
 The Best Compends for Students' Use 
 in the Quiz Class, and when Pre- 
 paring for Examinations. 
 
 Compiled in accordance with the latest teachings of promi- 
 nent lecturers and the most popular Text-books. 
 
 They form a most complete, practical and exhaustive 
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 np to the times in every respect, containing many new 
 prescriptions and formulae, and over two hundred and 
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 large experience as quiz-masters and attaches of colleges, 
 with exceptional opportunities for noting the most recent 
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 Cloth, each $1.00. Interleaved for Notes, $1.25. 
 No. i. HUMAN ANATOMY, "Based upon Gray." Fourth 
 Edition, including Visceral Anatomy, formerly published 
 separately. Over 100 Illustrations. By SAMUEL O. L. 
 POTTER, M.A., M.D., late A. A. Surgeon U. S. Army. Professor 
 of Practice, Cooper Medical College, San Francisco. 
 Nos. 2 and 3. PRACTICE OF MEDICINE. Fourth Edi- 
 tion. By DANIEL E. HUGHES, M.D., Demonstrator of Clinical 
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 PART I. Continued, Eruptive and Periodical Fevers, Diseases 
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 PART II. Diseases of the Respiratory System (including Phy- 
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 in Jefferson Medical College, Philadelphia. Revised, Enlarged 
 and Illustrated. 
 
 No. 5. OBSTETRICS. Illustrated. Fourth Edition. By 
 HENRY G. LANDIS, M.D., Prof, of Obstetrics and Diseases of 
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BLAKISTON'S ? QUIZ-COMPENDS ? 
 
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 Bound in Cloth, $1.00. Interleaved, for Notes, $1.25 
 
 No. 6. MATERIA MEDICA, THERAPEUTICS AND 
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 and a complete article on Prescription Writing. Based on the 
 Last Revision of the U. S. Pharmacopoeia, and including many 
 unofficinal remedies. By SAMUEL O. L. POTTER, M.A., M.D., 
 late A. A. Surg. U. S. Army; Prof, of Practice, Cooper Medical 
 College, San Francisco. Improved and Enlarged, with Index. 
 
 No. 7. GYNAECOLOGY. A Compend of Diseases of Women. 
 By HENRY MORRIS, M.D., Demonstrator of Obstetrics, Jefferson 
 Medical College, Philadelphia. 
 
 No. 8. DISEASES OF THE EYE AND REFRACTION, 
 
 including Treatment and Surgery. By L. WEBSTER Fox, M.D., 
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 ical College, etc., and GEO. M. GOULD, M.D. 71 Illustrations, 39 
 Formulae. Second Enlarged and improved Edition. Index. 
 
 No. 9. SURGERY. Illustrated. Third Edition. Including 
 Fractures, Wounds, Dislocations, Sprains, Amputations and 
 other operations; Inflammation, Suppuration, Ulcers, Syphilis, 
 Tumors, Shock, etc. Diseases of the Spine, Ear, Bladder, Tes- 
 ticles, Anus, and other Surgical Diseases. By ORVILLH HORWITZ, 
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 lege. Revised and Enlarged. 77 Formulas and 91 Illustrations. 
 
 No. 10. CHEMISTRY. Inorganic and Organic. For Medical 
 and Dental Students. Including Urinary Analysis and Medical 
 Chemistry. By HENRY LEFFMANN, M.D., Prof, of Chemistry in 
 Penn'a College of Dental Surgery, Phila. Third Edition, Revised 
 and Rewritten, with Index. 
 
 No. u. PHARMACY. Based upon " Remington's Text-book 
 of Pharmacy." By F. E. STEWART, M.D., PH.G., Quiz-Master 
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 No. 12. VETERINARY ANATOMY AND PHYSIOL- 
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 No. 13. DISEASES OF CHILDREN. By DR. MARCUS P. 
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 College. 
 
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 printed and bound. Each one forms a complete set of 
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