LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Class WORKS OF ALFRED I. COHN PUBLISHED BY JOHN WILEY & SONS. Indicators and Test-papers. Their Source, Preparation, Application, and Tests for Sensitiveness. With Tabular Summary of the Applica- tion of Indicators. Second Edition. Revised and En- larged, lamo, ix--(- 267 pages. Cloth, $2.00. Tests and Reagents, Chemical and Microscopical, known by their Authors' Names: together with an Index of Subjects. 8vo, iii-f-383 pages. Cloth, $3.00. TRANSLATION. Fresenius' Quantitative Chemical Analysis. New Authorized Translation of the latest German Edition. In two volumes. By Alfred I. Cohn. Recalculated on the basis of the latest atomic weights, and also greatly amplified by the translator. 8vo, 2 vols., upwards of 2000 pages, 280 figures. Cloth, $12.50. Techno-Chemical Analysis. By Dr. G. LUNGC, Professor at the Eidgenbssische Polytechnische Schule, Zurich. Authorized Translation by Alfred I. Cohn. i2mo, vii + 136 pages, 16 figures. Cloth, $1.00. TECHNO -CHEMICAL ANALYSIS. BY DR. G.' LUNGE, Professor at the "Eidgenossische Polytechnische Schule" at Zurich. AUTHORIZED TRANSLATION BY ALFRED I. COHN, Author of "Indicators and Test-papers," " Tests and Reagents," " Freseniitf Quantitative Analysis'" (translation); Member of American Chemica' Society; Society of Chemical Industry; etc. FIRST EDITION. NEW YORK : JOHN WILEY & SONS. LONDON: CHAPMAN & HALL, LIMITED. 1905. RA Of THE UNIVERSITY -V3Al Copyright, 1904, BT ALFRED I. COHN. Entered at Stationers' Hall. ROBERT DRCMMOND, PRINTER, NEW YORK. TABLE OF CONTENTS. PAGE I. Scope of techno-ehemical analysis I II. General operations preceding the analysis. 3 Taking the average sample 3 Comminuting ; Weighing off 4 Measuring 5 Sampling gases , . 5 III. Technical Gas-analysis 7 1. Winkler's burette 7 2. Bunte's burette 9 3. Orsat's apparatus 12 4. Hem pel's burette 12 Determining gases by combustion , 19 a. By explosion 20 $. With the palladium-asbestos capillary tube. ... 21 c. Combustion of methane in a Drehschmidt plat- inum capillary 22 Reich's method of determining absorbable gases titri- metrically 23 Determining carbonic acid in the air 26 Determining very small quantities of gases by absorp- tion 26 IV. Gas-volumetry 27 1. The azotometer 27 2. The calcimeter 29 3. The nitrometer and gas- volumeter 30 iii 141363 iv TABLE OF CONTENTS. SPECIAL PART. PAGH Fuels and Heating 37 Calorimeter , 37 Examination of coal 38 Gas-calorimeter 38 Upper and lower heat values 38 Smoke-gases 39 Water 39 Hardness. Determining by Clark's method 41 Examination by purely chemical methods 41 INORGANIC CHEMICAL MANUFACTURES. Sulphurous and sulphuric acids 44 Sulphur 44 Gas-sulphur 45 Pyrites 45 Zinc blende 47 Cinders 47 Calcination gases 48 Nitrose 48 Lyes for sulphite cellulose 49 Sulphuric acids of different strengths 49 Specific-gravity table ... '50 Titration 50 Impurities 52 Fuming sulphuric acid. . : , 54 Nitric Acid . . . . , 55 Saltpeter 55 Specific-gravity table , . . 58 Mixed- and waste-acids 59 Titration 59 Sulphate 59 Common table salt 59 Sulphate 60 Hydrochloric Acid 60 Specific-gravity table 61 TABLE OF CONTENTS. V PAGE Soda 62 Eaw materials 62 Crude soda-ash melt 62 Crude lyes 62 Carbonated lyes 62 Leach residues 63 Ammonia soda 63 Caustic lyes 63 Calcined soda .' 64 Crystal soda 65 Caustic soda ; Bicarbonate 65 Chlorine Industry 66 Manganese dioxide 66 Limestone ; caustic lime 67 Chlorine gas 68 Electrolytic lyes; Bleaching liquids 68 Chlorinated lime 69 Potassium Salts 71 Crude salt (Carnallit, Kainit, etc.) 71 Commercial potassium chloride 72 Potash 72 Potassium cyanide; Potassium ferrocyanide 73 Clay and Cement Industry 74 Clay for brick manufacture and use in pottery 74 Clay and marl for cements; Cements 75 Aluminium sulphate 75 Artificial Manures 77 1. Phosphoric acid , . . . 77 2. Nitrogen 79 3. Chlorate; Perchlorate 80 4. Potassa 81 5. Ferric oxide; Alumina 81 6. Lime 81 Gas- and Ammonia manufacture 82 Illuminating-gas 82 Gas-purifying compound 84 Gas liquor 85 Ammonia 86 Ammonium sulphate ..,....,..,.......,., ,..-.. 87 VI TABLE OF CONTENTS. PAGE Addendum: Calcium carbide 87 Coal-tar Industry 87 Tar 87 Commercial benzol 88 Differentiation of coal-tar benzol from petroleum, benzin, brown-coal oils, etc 90 Naphtalin ; Anthracene 90 Carbolic acid 91 Crude carbolic acid and Carbolic-acid preparations 92 Coal-tar pitch 92 Mineral Oils 93 Petroleum ; Benzin 93 Kerosene 94 Lubricating oils 95 Oils and Fats 97 Soaps 100 Glycerin 102 Sugar 102 Alcohol Manufacture (Brandy, etc.) 107 Starch 107 Malt 108 Mash 109 Alcoholometry 110 Fusel-oil, etc Ill Vinegar 113 Wine 115 Beer Brewing 116 Tanning Materials 119 Dyeing 121 LITERATURE. LUNGE, Chemisch-Technische Untersuchungsmethoden. 3 vol- umes. Berlin, 1899-1900. LUNGE, Taschenbuch fur die /Soda-, Pottasche- und Ammoniak- fabriMtion. 3d edit. Berlin, 1900. AHRENS, Arileitung zur chemisch-technischen Analyse. Stutt- gart, 1901. TREADWELL, Kurzes Lehrbueh der analytischen Chemie. 2d edit. Leipzig, 1902-1903. A. CLASSEN, Ausgewahlte MetTioden der analytischen Chemie. 2 volumes. Braunschweig, 1901-1903. KONIG, Untersuchung landwirtschaftlich und gewerblich wich- tiger Stoffe. Berlin, 1891. KO'NIG, Chemische Zusammensetzung der menschlichen Nah- rungs- und G-enussmittel. 4th edit, by BOmer. Berlin, 1903. WINKLER, Lehrluch der technischen Gasanalyse. 3d edit. Leipzig, 1901. HEMPEL, Gasanalytische Methoden. 3d edit. Braunschweig, 1900. NEUMANN, Gasanalyse und Gasvolumetrie. Leipzig, 1901. WALTER und GARTNER, Untersuchung und Beurteilung der Wasser. 4th edit. Braunschweig, 1895. BENEDIKT, Analyse der Fette und Wachsarten. 4th edit, by F. Ulzer. Berlin, 1903. GNEHM, Taschenbuch fur Fdrberei und Farbenfdbrikation. Berlin, 1902, TECHNO-CHEMICAL ANALYSIS. GENERAL PART. ISCOPE OF TECHNO-CHEMICAL ANALYSIS. TECHNO-CHEMICAL ANALYSIS comprises: 1. The examination of raw material for chemical factories and other technical industries in which the chemical nature of the substances plays an important role. 2. The operative control of chemical factories by chemical and physical means. 3. The examination of the end-products respecting the properties which have an important bearing on their employment, and which are hence to be guaran- teed to the purchaser. All these investigations may be of the most varied character. Frequently only qualitative tests are made as to whether certain injurious impurities are absent, or whether color, luster, density, or solidity of the end- product meet the requirements demanded. Very often ; 2 TECHNO-CHEMJCAL ANALYSIS. however, quantitative determinations are required, it may be of the valuable chief constituent, or of useful or injurious secondary constituents; or it may be of the action exerted by the product (e.g., the viscosity of lubricating-oils, or the colorific power of dyes). In many cases empirical methods, useful for practical pur- poses, are employed; very often, however, the methods employed in scientific chemical analysis must be adopted, and with every attention to extreme accu- racy. II. GENERAL OPERATIONS PRECEDING THE ANALYSIS. The preparation of a uniform sample is of the utmost importance. If this has not been properly effected, the techno-chemical analysis is utterly worthless, and it may lead the investigator altogether astray. In the case of finely pulverulent substances the preparation of a sample presents no great difficulties; with fluids and gases the object is also easily attained, but in all these cases certain rules of procedure must be followed in order to obtain a correct average sample. Where, however, the material occurs in the form of coarse lumps, the preparation is attended by particular diffi- culties. Of such substances large quantities must be taken, the lumps comminuted, again thoroughly mixed, and the sample finally taken from the mixture, and, inclosed in sealed bottles, handed over to the chemist. Solids must then be further comminuted in the labora- tory, until they are reduced to a sufficiently fine powder to be available for analysis. In doing this, special pre- cautions must frequently be observed in order to avoid loss of moisture, or to prevent any attraction of mois- ture, oxygen, carbonic acid, etc., from the atmosphere. 3 4 TECHNO-CHEMICAL ANALYSIS. Reduction to a coarse powder is usually effected in an iron mortar, while porcelain, agate, or steel mortars are employed for preparing very fine powders. This procedure is of course unnecessary in the case of fluids and gases; nevertheless, even with these, cer- tain precautions must be taken to assure thorough mixing, and in any event the temperature of the sample must be taken, and allowance made for it. In the analysis, solids, and frequently liquids also, are weighed; the latter are, however, also often meas- ured, but gases are in all cases measured. For weighing off, both coarse and fine balances must be employed. Analytical balances which turn with 0.1 mgrm. (or after long-continued use often only with 0.2 mgrm.) are used only when the scientific chemical methods of analysis are employed, and where the quan- tity of the sample taken for the analysis does not ex- ceed 1 or at most 2 grm. In cases where larger quan- tities are weighed off, as is frequently done when it is required to dissolve the sample in order to take only a portion for analysis, the sufficiently sensitive hand- or tare-balance is to be preferred, as the weighing is much more rapidly done. Under all circumstances, how- ever, the sensitiveness of the balance and the accuracy of the weighing must be decidedly greater than the limit of error for the individual case, and which repre- sents the sum of all unavoidable errors incident to both the method and the manipulation. In technical analyses, such a quantity is frequently weighed off that, by titration, the volume of reagent OPERATIONS PRECEDING THE ANALYSIS. 5 used up gives directly, and without any calculation, the percentage of constituent sought, by a simple reading-off. Fluids, too, are at times weighed off in technical analyses, those that are non-volatile and unchanged on exposure to air being weighed in suitable vessels, and others in glass bottles provided with glass stoppers, or in pipettes provided with a stopcock. Usually, how- ever, fluids are measured, in which case the tempera- ture must always be noted, and the specific gravity taken. Gases are frequently examined at the place of col- lection, in which case the apparatus employed in the analysis serves for both drawing off and measuring the sample of gas. In doing this, however, care must be exercised to take the sample of gas at the proper place or point, avoiding also the introduction of any impuri- ties, such as soot, or even admixture of atmospheric air. The former may be excluded by employing a filter of cotton or asbestos within the inlet-tube; the latter, by passing the inlet-tube through a perforated stopper which closely fits the hole in the gas-pipe or chimney from which the gas is to be taken. In other cases the samples of gas must be taken to be subjected to analysis elsewhere. The samples are best collected by drawing the gas into glass tubes both ends of which are drawn out, and of which several may be successively introduced and filled; the tubes are best closed by fusion, rubber caps being not so good. In many cases the transportation of the samples is 6 TECHNO-CHEM1CAL ANALYSIS. satisfactorily accomplished in glass bottles, zinc ves- sels, etc. Rubber vessels are very convenient to use, as it is only necessary to press them together, when the gas readily fills them on releasing the pressure. Fre- quently, however, the gas may be rendered impure thereby, or a diffusion of the gas through the rubber walls is to be feared. III. TECHNICAL GAS ANALYSIS. In many cases, in the illuminating-gas industry, the technical chemist must employ the methods of scientific gas analysis, in which mercury is employed as the con- fining liquid. In the majority of cases, however, the methods and apparatus employed in technical analysis are used, in which water and aqueous fluids serve as the confining liquid, and which enable the operations to be much more simply and rapidly performed. In technical gas analysis, the object must be to oper- ate so rapidly that variations of the barometer during the operation may be disregarded. Those of the ther- mometer are avoided, where it can be done, by placing the measuring-tube within a water-mantle; otherwise a certain time must be allowed to elapse before each read- ing-off, and until the temperature has become station- ary. By this procedure it becomes unnecessary to re- duce the volume of gas to normal (0 C. and 760 mm. pressure). We will here mention only the more important appa- ratus employed in technical analysis. 1. Cl. Winkler's gas-burette (fig. 1) consists of two limbs, A and B, connected by means of a rubber tube, C, to form a U-tube. A is a measuring-tube graduated in 7 8 TECHNO-CHEMICAL ANALYSIS. 100 cc. It is closed above and below by glass cocks. The upper, a, is simple; the lower, 6, is a three-way cock, having, besides the usual transverse perforation, also a longitudinal one, so that communication can be estab- lished with the air by turning the cock. The second limb, B, is not graduated, and bears a side tube near the bottom pro- vided with a cock, c. The whole may be brought to a perpendic- ular or any inclination desired by being fixed in a stand. The gas to be examined is allowed to enter at 6, and passes out at a, or vice versa, until the tube A is filled with the pure gas. a and b are then closed, the confining liquid then introduced into B, until it begins to flow out from the longitudinal perforation in 6, and the cock b so turned that A and B are connected, i.e., the liquid may pass from B to A, and act upon the gas. By inclining the apparatus to and fro, the absorption is pro- moted, until it is complete. The tubes A and B are then manipulated so that the level of the liquid in both tubes is at the same height, by allowing liquid to flow out from c or C, after which the volume of the gas remaining in A is read off. FIG. 1. TECHNICAL GAS ANALYSIS. 9 Winkler's burette is particularly well adapted for such cases where but one constituent of a gas is to be deter- mined; e.g., carbonic acid in smoke-gases, saturation- gases, lime-oven gases, etc. In such a case the same absorption liquid is used; in the case before us it is soda-lye. 2. Bunte's burette (fig. 2) consists of a measuring-tube, A, closed above and below by cocks, a and 6. a is a three-way cock. Above the latter is a funnel, t, which bears a scratch or mark at about its center. The tube A has a capacity of a little over 110 cc., and is graduated from above downwards, from 100 to 0, the graduations being then con- tinued 10 divisions further. The tube A is loosely suspended in a stand, which at the same time supports a bottle or funnel, B, which is connected with the tip of the burette, c, by means of a rubber tube. A second bottle, C, is also required, it being ar- FIG. 2. ranged so that liquid may be drawn or forced from or into A. The bottle B is then connected with c, and water poured into it until the liquid has entered the funnel, t' } the cocks 10 TECHNO-CHEMICAL ANALYSIS, are then closed and the rubber tube removed from c. The longitudinal perforation of a is then made a part of the passage through which the gas to be examined is to be drawn, and b opened, when the gas will enter into A. After waiting a short time until the water in A has fallen about 5 cc. below the zero-mark, close a, and by means of the bottle B force water into A, until the level is about 5 cc. above the zero-mark, so that the gas is somewhat compressed, remove B again, and by cautiously opening a, allow water to flow out until the liquid stands at the zero-mark, and then pour water into t up to the mark or scratch. The gas will now be under the atmospheric pressure, together with that exerted by the small column of water in t] and under this pressure all subsequent measurements must be made. In order to next introduce an absorbing fluid into the burette, unite the tip of c with the bottle C, draw off the water from A so far as possible, close b } immerse c in a dish containing the liquid used for absorbing, and again open b. A certain quantity of the liquid will now enter A. Then close b, remove A from the stand, shake it well, replace it in the stand, immerse c in the dish of absorbing fluid, and open b. A further quantity of the fluid will now enter A; and these operations are repeated until no more liquid is drawn in, i.e., no more gas is absorbed. The proper pressure is then brought about as above, by pouring water into t, opening a, and allowing the water to run into A from t, whereby the walls of A are rinsed down, and the absorbing liquid TECHNICAL GAS ANALYSIS. 11 becomes covered with a layer of pure water. Care must be taken that on opening a, the water in t is on a level with the mark ; the volume is then read off in A. The volume of gas that has disappeared corresponds to the absorbed gaseous constituent. Other constituents of gases may be determined in a similar manner, as an example will best show; e.g., in a mixture of carbonic acid, carbonic oxide, and nitrogen, such as occurs in generator gases. The carbonic acid is always first absorbed by potassa lye; the original volume of gas is thereby reduced from 100 down to 90, according to which the gas contains 10 per cent, by volume of C0 2 . A now contains potassa lye. It is not necessary to remove the lye entirely, as the absorption of oxygen must next be accomplished by pyrogallol in an alkaline solution. For this purpose, only about half of the potassa lye is drawn off from A a b, and t is im- mersed in a dish containing aqueous pyrogallol solution, of which some is then made to enter A. By manipulat- ing as already described, we find the volume of gas reduced from 90 to 85, and thus ascertain the gas to contain 5 per cent, of oxygen. We now come to the carbonic oxide. This must be absorbed by an ammo- niacal solution of cuprous chloride, which is entirely incompatible with the alkaline pyrogallol solution re- maining in A. The pyrogallol solution is therefore drawn off as completely as possible by aid of the bottle C, water allowed to enter A through t and a, then again drawn off, and this procedure repeated, whereby A is cleansed. The new absorbing fluid is now introduced, 12 TECHNO-CHEMICAL ANALYSIS. and the residual gas energetically acted upon with the cuprous-chloride solution until all the CO is absorbed, which is more difficult to accomplish and requires more time than is the case with C0 2 and 0. The error in reading-off caused by the ammoniacal pressure is reduced to a minimum by finally allowing water to run from t into A to form a layer on the liquid therein. We now find the volume of gas to be, for instance, 65; we hence infer that 20 per cent, of CO was present in the gas. The remainder, 65 per cent., consists chiefly of nitrogen. It might also contain hydrogen, methane, and other non- absorbable gases, but in the case here instanced these are present only in very small quantities. Where these gases are present in large quantities, and they must be determined, the object may be accomplished by pass- ing the gasc through a Drehschmidt platinum tube (see below) into another burette (Bunte's), the operation being conducted as described below. Bunte's burette is particularly well adapted for those cases in which a transportable apparatus is required, and in which but few of the gaseous constituents are to be separated by absorption fluids. It is, however, also adapted for use in complicated cases, as above described, but then the advantage offered by its ready transportability is minimized. 3. Orsat's apparatus (fig. 3). In its usual form this consists of a gas-burette, A, inclosed within a water- mantle, and connected by means of a rubber tube with a leveling-bottle, E, and with the capillary tube, a, The tube a bears three cocks ; at right TECHNICAL GAS ANALYSIS. 13 FIG. 3. angles, and directed downwards, and which are con- nected with the U-shaped receiv- ers, B, C, and D; it also is provided with the three-way cock, e. The whole apparatus is inclosed within an easily transportable case. As a rule, the upper part of the burette is made wider, and is ungraduatedj the lower, narrower part is gradu- ated in cubic centimeters from 60 to 100, the zero-point being at the upper part of the tube. To better insure a good surface contact be- tween the gas and the liquid in the receivers B, C, and D, bundles of glass tubes are placed in the latter. The first receiver, B, is always filled with potassa lye for the absorp- tion of carbonic acid ; the second one, C, with an alkaline pyrogallol solution, or even a small stick of phosphorus, immersed in water, to absorb the oxygen.* The third receiver, C, is filled with ammoniacal cuprous-chloride solution and pieces of copper wire, to absorb carbonic oxide. In a mixture of gases, therefore, C02, 0, and CO may be determined directly, and the N by differ- ence. Special devices have also been devised in order to permit other gases, for instance heavy hydrocar- * It is much more convenient to use phosphorus than pyrogallol, because the latter can be used but a few times, whereas phos- phorus can be used for hundreds of analyses. Phosphorus can not, however, be used where the vapors of heavy hydrocarbons are pres- ent, and at temperatures below 16 C. 14 TECHNO-CHEMICAL ANALYSIS. bons, hydrogen, methane, etc., to be determined at the same time. These devices, however, make the apparatus so complicated that its great advantages, simplicity of use and ready transportability, are lost. The only modification that has been retained is that of Lunge. This is for the determination of hydrogen, and it requires the addition of a wide receiver, a platinum- asbestos tube, and a lamp; this makes the apparatus about one-third larger than otherwise. To use the apparatus, the gas is drawn into the burette, after the latter has been filled with water to the upper mark by raising the bottle E to a sufficient height, the three-way cock being connected with the source of gas supply, and so set as to communicate with the capillary tube, E being then lowered. E is next raised until the water in it and in A stands at the same level at 100., whereupon e is closed. The liquids in B, C, and D must previously have been intro- duced and, by means of the leveling-bottles and the space a, brought to marks just below the cocks b, c, and d. b is now opened, and the gas forced from A into B by lifting the bottle E, whereby the gas comes into contact with the potassa adhering to the glass "tubes, and the carbonic acid is rapidly absorbed. After two or three minutes draw the gas back into A again by lowering E, when the potassa solution will flow back and again fill B up to the mark, whereupon the cock must at once be closed. Now bring the water in A and E to the same level by raising E to a suitable height, and read off the volume of gas in a 6; the gas that has TECHNICAL GAS ANALYSIS. 15 disappeared corresponds to the carbonic-acid content. In the same manner force the gas into C, whereby the oxygen is absorbed by the pyrogallol-potassium solu- tion or phosphorus. This requires a somewhat longer time than is the case with carbonic acid, and it must be facilitated by repeatedly forcing the gas into and out of the tube C. The absorption of the carbonic oxide in D is still more slow ; furthermore the cuprous-chloride solution can only be used three or four times, and must then be renewed. In all these cases the space within the capillary must be regarded as having an injurious effect on the reading- off, and on this account alone the analysis can not be accurate. To this must also be added the solubility of the carbonic acid in the water used as the confining liquid, and which must be allowed for, of course, in other apparatus also. Very accurate determinations can not be made with the Orsat apparatus; the latter is, however, excellently adapted for use in the factory, be- cause of the ease and rapidity with which the manipu- lations may be carried out, and because of its transpor- tability, etc. 4. HempePs gas-burette (fig. 4), because of its size, is not readily available for use otherwise than in the laboratory, but, on the other hand, it is adapted for the most varied uses, so that with it most of the prob- lems of gas analysis may be solved with a compara- tively high degree of accuracy. The apparatus con- sists of the gas-burette or measuring-tube, A, which is connected with the leveling-tube, B, and a, suit- 16 TECIINO-CHEMICAL ANALYSIS. able number of gas-pipettes, C, of varied form, as shown in figures 5, 6, and 7. The measuring-tube A is sometimes inclosed within a water-mantle, which, however, greatly increases the difficulty of manipulating, and which can generally be dis- pensed with. The upper end of the tube forms a capillary, upon which is fastened a piece of soft-rubber tubing provided with a pinchcock, a, and in which is then fastened a twice- bent capillary tube, i. From the pinchcock, a, to a mark just above the wooden foot, the tube A holds 100 cc., graduated in 1/5-cc. Below the mark, the tube is narrowed and bent at a right angle; the bent part protrudes from the side of the wooden foot, and the same is the case with the simple, non- graduated leveling-tube, B. In the case of mixtures of gases that can not well be collected over water, a three- way cock is sealed into the measuring-tube between the zero-mark and the foot, and the tube is then filled just as the Winkler tube is filled. The meas- uring-tube in its usual form is filled with water by elevating the tube B ? until the water rises above the FIG. 4. TECHNICAL GAS ANALYSIS. 17 pinchcock a; then the gas is drawn in by lowering B and opening a, until the water, when it is level in both A and B, stands at the zero-mark in A. To treat the gas with absorption fluids or otherwise, it is drawn into a gas-pipette, C, and always by elevating B and opening a. The simple absorption pipette (fig. 5) consists of the U-formed capillary h, pinchcock I), and the bulbs c (200 cc.) and d (150 cc.). In order to fill the tube, pour the fluid into d, and apply suction at 6, until c and b are filled, while d remains almost empty, thus allowing room for the return of liquid into d } when gas enters c. The absorption pipette for solid reagents (fig. 6) is constructed upon exactly the same principle, but instead of the bulb c, the apparatus is provided with a vessel e, the neck at the lower end of FIG. 5. FIG. 6. FIG. 7. which is closed with a stopper, and in which phos- phorus, copper wire, etc., may be put. The com- pound absorption pipette (fig. 7) is provided with a second pair of bulbs, / and g, / being filled with water until it just enters g. These bulbs are employed with 18 TECHNO-CHEMICAL ANALYSIS. reagents which must be protected from exposure to the air (pyrogallol-potassium, cuprous-chloride solu- tion, etc.). In fig. 4 we see a U-formed glass capillary, i, which is connected with the measuring-tube A and the pi- pettes. Before use these are filled with water in order to obviate the " error-causing " space. By elevating B and opening the pinchcocks a and 6, the gas is forced from A into C; b is then closed, the pipette disconnected the apparatus gently shaken to facilitate the absorp- tion of the gas, the pipette again connected with A, and the gas again drawn into A by lowering B, by which procedure the absorption liquid once more fills the capillary tube i, but must not be allowed to enter A. The pinchcock a is now closed, the pipette again removed and stoppered, and the tube B elevated until the water is on a level in both A and B; the volume of gas is then read off. For the consecutive absorption of individual gas constituents a corresponding number of pipettes are required, and the gas must be consecutively forced into the tubes, and the contents of each tube returned to A in order to be measured. In this manner, carbonic acid, for instance, can first be absorbed by potassa lye, then oxygen by alkaline pyrogallol solution or phosphorus, and next carbonic oxide by cuprous- chloride solution, as described on page 14. In addi- tion, however, heavy hydrocarbons may be absorbed by fuming sulphuric acid; nitric oxide by potassium permanganate acidulated with sulphuric acid; nitro- TECHNICAL GAS ANALYSIS. 19 gen dioxide by concentrated sulphuric acid; ammonia by diluted sulphuric acid; chlorine, hydrochloric acid, hydrogen sulphide, or sulphur dioxide, by potassa lye; or the chlorine or sulphur dioxide by potassium-iodide solution. These reagents must, however, be used one after another systematically, so that one gas is not prematurely absorbed with one of the others. For instance, in order to determine chlorine and carbonic acid in a gas, potassa solution must not be employed at the start, but the chlorine should first be absorbed by potassium iodide, and after measuring the gas remain- ing, the carbonic acid then absorbed by potassa. When heavy hydrocarbons are to be absorbed, this must be done after the carbonic acid has been removed, but before the treatment with pyrogallol solution and cuprous chloride. DETERMINATION OF GASES BY COMBUSTION. The Hempel burette may also be easily employed in those methods in which the gases are determined by combustion, and which is usually the case with hydrogen and methane. In employing it thus, how- ever, all the gaseous constituents removable by absorp- tion fluids must first be removed; to the residual gas, after its volume has been measured, a measured quantity of atmospheric air, or even oxygen, if necessary, suffi- cient for combustion, is added. Usually a preliminary experiment is made in order to approximately determine the quantity of air required for the combustion, if no data are at hand that render the experiment un- 20 TECHNO-CHEMICAL ANALYSIS. necessary. During the combustion, 1 volume of 2 disappears for every 2 volumes of H 2 ; hence if only hydrogen is present, two-thirds of the volume-con- traction after the combustion may be calculated as hydrogen. In the case of methane, 1 volume of CH 4 always requires 2 volumes of 2 , with the formation of 1 volume of C0 2 , besides 2H 2 0, in liquid form; hence a contraction of 2 volumes. The volume of methane thus corresponds to one-half the observed contraction. If now the C0 2 is absorbed by potassa lye, the original volume of methane exactly corresponds to the contraction thus caused, or but one-third of the total contraction. When both hydrogen and methane are present, and we measure the contraction directly resulting from the combustion, KI, and the contraction resulting from the absorption of carbonic acid, K 2 , then K 2 will represent the volume of methane, and f(Ki-2K 2 ) that of the hydrogen. The combustion may be effected either by explo- sion, or by means of heated platinum or palladium. The explosion is effected by means of an electric spark in a eudiometer hi which a piece of platinum wire is fused, or in a Hempel tl explosion-pipette " similarly provided. It occurs, "however, only when the gases are mixed in certain proportions, and requires a rather complicated apparatus, so that it is not well adapted for technical purposes. Much more convenient is the other method of com- bustion, in which even fractional combustion may be TECHNICAL GAS ANALYSIS. 21 effected, i.e., the more readily combustible hydrogen is first burned by the aid of gently ignited palladium, and then the more difficultly combustible methane, by means of strongly ignited palladium or platinum wire. For the combustion of the hydrogen alone, the Winkler palladium-asbestos capillary is best adapted. This has exactly the same form as the capillary tube, i, shown in fig. 4, and, like it, is interposed between the burette tip a, and a pipette, C. In its horizontal part is placed a thread of palladium-asbestos, which is prepared by impregnating long-fibered asbestos with a concentrated mixture of solutions of palladious chloride, sodium formate, and sodium carbonate, and then drying at a gentle heat. The threads are intro- duced Into a glass capillary tube, 16 to 18 cm. long, and 1 mm. bore (6 mm. external diameter), which is then bent at a right angle 3J to 4 cm. from each end. During the operation the capillary is heated by a small gas- or alcohol-flame, but never to a point sufficient to soften it. After the residual gas in the burette A has been measured, the rest of the space in the burette, provided there is sufficient, is filled up to nearly 100 cc. with air, and another reading taken. If the volume of the resid- ual gas is too great, because of too large a nitrogen con- tent for instance, to permit a sufficient quantity of air to be added, the residual gas is first measured, and then a quantity of it is expelled into the air, the remainder measured, and then a sufficient volume of 22 TECHNO-CHEMICAL ANALYSIS. air introduced to afford enough oxygen for combustion. Of course the analytical calculations must be made accordingly. The mixture is then slowly forced, by elevating the tube B, through the heated palladium capillary, and equally as slowly back again, great care being taken that not the slightest drop of water enters the capillary, otherwise it will burst. After repeating the passage and re-passage of the gas through the capillary, the gas is again measured; two-thirds of the contraction observed corresponds to the hydrogen that was present. Carbonic oxide is burned in a similar manner, but much more slowly; and, at a higher temperature, also the heavy hydrocarbons which, however, should have been previously absorbed (see page 18). Methane is not burned under these conditions. In order to burn methane, the gas must be well mixed with sufficient air, and brought into intimate contact with strongly ignited platinum. For this purpose plati- num wire may be employed which is electrically heated within a small glass vessel through which the gaseous mixture is slowly passed. It is more convenient to use the Drehschmidt platinum capillary, a platinum tube 200 mm. long and 0.7 mm. in diameter and almost filled with 3 or 4 platinum wires; to each end of the tube brass or copper tubes are soldered. 100 mm. of its length are heated to a bright-red heat by a gas-burner with a fan-shaped opening. After twice passing and re-passing the gas through the tube at a moderately rapid speed, all the methane is burned. TECHNICAL GAS ANALYSIS. 23 The apparatus is then allowed to cool off, the carbonic acid formed is absorbed by potassa lye, and the volume of the methane that was present ascertained by dividing the total contraction by 3. In a similar manner nitr.ous oxide and nitric oxide may also be determined by combustion with hydrogen. In the case of nitrous oxide the reaction is as follows: N 2 0+H 2 = NH+H 2 0; hence the resulting contraction is the exact equivalent of the nitrous oxide. With nitric oxide, the reaction is as follows : 2NO -f 2H 2 = N 2 +2H 2 0; thus the volume of the nitric oxide is equal to two-thirds of the resulting contraction. REICH'S METHOD OF TITRIMETRICALLY DETERMINING ABSORBABLE GASES (Fio. 8). In this a definite volume of the absorption fluid is introduced through the middle tubulure of a three- cneked bottle, A; the other two tubulures serve as the inlet and exit, respectively, for the gases. The inlet tube, a, extends to the bottom of the bottle; its end is best sealed, and provided with a number of small holes just above the tip to better distribute the gas. The exit-tube b ends just below the stopper, and is connected with the bottle, B, which serves as an aspi- rator, the siphon-tube of which is provided with a pinch-cock, and leads into the measuring-cylinder C. After the absorption fluid, with a little of an indi- cator added, has been introduced into A, open c and slowly draw the gas, by applying suction, through a into A, and then out through b and C, while A is con- 24 TECHNO-CHEM1CAL ANALYSIS. stantly shaken in order to facilitate the reaction. The moment the color-change in A shows that the liquid in A has been saturated, close c. The liquid that has run out is measured in C, and shows the volume of FIG. 8. gas that has passed, to which must be added the volume of the constituent to be determined, and corresponding to that of the absorption fluid employed. This volume is in all cases the same, whereas the total volume natu- rally always differs. The percentage content of the gas constituent is therefore ascertained by multiplying TECHNICAL GAS ANALYSIS. 25 the fixed volume of the gas constituent by 100, and dividing the product by the total gas volume, found as above, and as we will show by an example. For more accurate determinations, the gas volume ascertained from the water that has run off from the aspirator must be reduced to C. and 760 mm., because the volume of the gas sought is always calculated in this condition; however, in the ordinary factory analyses this is usually omitted as being unimportant. Reich had devised his method for a particular case, which will be described below; namely, for the deter- mination of sulphur dioxide in the calcination gases from pyrites, and for like cases. This method is based upon the following reaction: S0 2 +2I +2H 2 = H 2 S0 4 +2HI. The determination is made by passing the current of gas through a known volume of standardized iodine solution until all the iodine is converted into hydriodic acid, the end-point being recognized by the decolorization of the solution; for every 2 atoms I, 1 molecule of SO 2 will be indicated as having passed through the apparatus. To carry out the process, introduce about 500 cc. of water into A, then add a little starch solution and 25 cc. of iodine solution, which is best so prepared that 1 cc. of the solution exactly corresponds to 1 cc. SO 2, wherefore the solu- tion must contain 11.3353 grm. I per liter. The cal- cination gas is then passed through the solution as above detailed, and while agitating, until the liquid has but a faint bluish color; the liquid that has run off from the aspirator is then measured. Let us sup- 26 TECHNO-CHEMICAL ANALYSIS. i pose that its volume was 320 cc. According to the 100X25 equation 3 ~ Q ~-=7.25, the calcination gas contains 7.25 volume-per cent, of S0 2 , the reduction of the 320 cc. to C. and 760 mm. being neglected. Lunge has further extended this method to the determination of the total acids in calcination gases, e.g., S0 2 , S0 3 , and HC1. In such a case soda-lye is used as the absorbing liquid, and phenolphtalein as indicator; the red color disappears when for 1 equiva- lent of the acids 1 equivalent of NaOH is used up. In other respects the process is the same as above detailed. Lunge has also devised an analogous method for the determination of carbonic acid in the air, and, in con- nection with Zeckendorf, constructed an easily trans- portable apparatus for it. In this method use is made of the circumstance that the reddening of the phenol- phtalein by the Na 2 C0 3 disappears when all the carbonate has become converted into bicarbonate, as in the following reaction: Na 2 C0 3 + C0 2 + H 2 = 2NaHC0 3 . Exceedingly small quantities of absorbable gases are determined by drawing a large volume of the gas, measured by passing it through an accurate gas-meter, through an apparatus affording a sufficiently large surface contact, and containing the absorbing sub- stance in liquid or solid form, and afterwards, accord- ing to circumstances, determining the quantity of the absorbed gas either by weighing the apparatus or by titrating back. IV. GAS-VOLUMETRY. Under this term is understood the operations by which the constituent of a liquid or solid substance sought for is determined by its evolution and measure- ment in the form of a gas. The most important appa- ratus used for this purpose are the following: 1. THE AZOTOMETER (FiG. 9). This instrument (Knop's) derives its name from the fact that it was originally devised for the determination of ammoniacal nitrogen, for which purpose it is even at present mostly used. It may, nevertheless, be used in many other gas-volumetric operations. We will describe its original application, in which the ammo- niacal nitrogen is liberated in its elementary form by the action of brominized soda-lye (100 grm. caustic soda dissolved in 1} liters of water, and adding to this solution, while kept cold, 25 grm. bromine). A is the decomposition vessel, to the bottom of which the small cylinder, a, containing the brominized lye, is sealed. A is placed within the vessel B, filled with water in order to maintain the temperature uniform throughout the reaction. The cylinder, C, also filled 27 28 TECHNO-CHEMICAL ANALYSIS. with water, holds the burette, c, graduated from above downwards, the additional tube, d, and a thermometer, e. By means of the tube /, sealed in near the lower end, and the cock g, d communicates with the bottle h, which in turn is connected with the rubber bulb, i. FIG. 9. c and d are filled with water by pressing i together, and then opening g to allow water to run off until it stands at the zero-mark, while by opening the cock k, communication is established with the bottle, in which the space surrounding a has been filled with the solu- tion of the ammonium salt, a itself being filled with the brominized lye. 30 to 40 cc. of water are now allowed to run out by opening g, after which A is re- moved from B and inclined so that a little of the lye GAS-VOLVMETRY. 29 flows from a into the ammonium-salt solution, whereupon the bottle is shaken; this operation is repeated until the decomposition is complete. A is then replaced in B. and after waiting about twenty minutes until the temperature has become, uniform, water is allowed to flow through-*/ until it stands at the same level in c and d, and the volume then read off. The volume must be reduced to C and 760 mm. ; in such a case, however, the volume must be increased by 2.5 per cent., in order to compensate for the " absorption of nitrogen " by the brominized lye (actually, however, it is due to the reaction being incomplete). If the temperature is not maintained uniformly, i.e., if the initial and final temperatures differ much, the errors caused thereby will be quite considerable. The reduction is made by employing the following formula, in which B represents the barometric pressure, t the temperature, and / the pressure of aqueous vapor at the temperature t: 273(B-/) (273 +0760 ' 2. THE CALCIMETER. This name is applied to apparatus intended for the determination of carbonic acid in carbonates, the acid being expelled by means of strong acids and deter- mined in gaseous form. The principle upon which the apparatus is based is quite similar to that of the azo- tometer. It is variously constructed, the forms devised by Scheibler, Dittrich, and Baur-Cramer being the 30 TECHNO-CHEMICAL ANALYSIS. ones most generally used; in these, water, mercury, and other fluids are employed as confining liquids. All these, however, suffer from the disadvantage that the liquid wherewith the evolution is effected retains some of the carbonic acid, a drawback from which the apparatus devised by Lunge and Marchlewski is free (see Lunge's Chem.-Techn. Untersuchungsmethoden, I, p. 142). 3. THE NITROMETER AND GAS-VOLUMETER. These apparatus, devised by Lunge, employ mer- cury as the confining liquid, and therefore afford more accurate results than are possible with apparatus in which water is used. The apparatus received the name '* nitrometer" because it was originally employed for the determination of nitrogen in nitrates and nitrites (and the corresponding esters), and in which the mer- cury served the double purpose of confining fluid and reagent for effecting the evolution of the nitrogen in the form of NO, in the presence of strong sulphuric acid. It was, however, found to be very serviceable in other cases as well. The name " gas-volumeter " is applied to those apparatus in which a " reduction-tube" is employed for mechanically reducing the tempera- ture and pressure to C. and 760 mm. The simple nitrometer is shown in fig. 10, and its most usual application, the analysis of nitrates and nitrites, will be described. A is the gas-measuring tube, which may be either cylindrical, with the portion below the cock holding 50 cc, and graduated hi 1/10 cc,; or GAS-VOLUMETRY. 31 globular in form, with a capacity of 100 to 150 cc., the lower 50 cc. of which are contained within the cylin- drical part, graduated in 1/10 cc. The upper part of the tube bears a three-way cock, a, and the funnel, b. A stout rubber tube connects the lower end of A with the leveling-tube B. A is filled with mercury through B, until it enters b, the excess being then allowed to run off through the side tube at a. The substance to be exam- ined is then introduced into b. Nit rose or sulphuric acid containing nitric acid is simply introduced with a pipette; saltpeter is in- troduced -either in substance with a little water, or in very concentrated solution; guncotton, dynamite, and the like, are placed within b in substance, and dissolved therein in concentrated sulphuric acid. The liquids are drawn into A by low- ering B and cautiously opening the cock a, b being then rinsed by pouring into it 2 to 3 cc. of concen- trated sulphuric acid, and drawing this into A as before, the operation being repeated once more, a is now closed, and A vigorously shaken until no further FIG. 10. 32 TECHNO-CHEMICAL ANALYSIS. evolution of gas takes place. After waiting ten to fifteen minutes, in order to allow the foam to subside and the temperature to become even throughout, the gas in A is brought under atmospheric pressure by raising B to such a height that the mercury in B stands at a somewhat higher level than in A, i.e., as much higher as the layer of acid in A, hence corresponding to about one-seventh of the height of the latter; it is advisable, in fact, to have the level slightly lower, in order to create in A a slight diminution of pressure. A few drops of acid are then poured into 6, and the cock a opened very cautiously, until the acid running from b causes the liquids in A and B to stand at the same height, and which naturally requires that air be allowed to enter A. The volume of nitric oxide in A is then read off, the temperature being also read from a ther- mometer suspended quite close to the apparatus, while the barometer is also observed; the proper reduction is then made to C. and 760 mm. As the gas in this case may be considered as perfectly dry, because of the presence of the concentrated sul- phuric acid, the formula for the reduction is quite sim- 273B S (273+ 0760' Every cubic centimeter of NO corresponds to 0.000625 grm. nitrogen, or 0.001694 grm. N 2 3 , or 0.002808 grm. IIN0 3 , or 0.003789 grm. NaN0 3 . The operation may also be carried out by having the reaction take place in a vessel separate from the meas- uring-tube; in which case the latter js then used only GAS-VOLUMETRY. 33 for measuring the gas: If the operation above de- scribed is to be made, i.e., the evolution of nitric oxide from nitrate- or nitrite nitrogen, by shaking with mercury and concentrated sulphuric acid, there is employed for the purpose -an ' ' agitation- flask" C (fig. 11), arranged like the nitro- meter, but not graduated, and provided with a separate leveling-tube, D. The de- composition is effected just as described above, and the gas then forced into A by raising D and lowering B and C, after the capillary tubes at the side of the cocks have been connected, and A filled to the top with mercury. All the gas is forced over, but none of the acid in C must be allowed to pass in along with the gas. The mercury in A and B is then brought to a level, the volume of gas in A read off, thermometric and baro- metric readings taken, and the reduction then made to C. and 760 mm. For those gas-volumetric operations in which other reactions occur, use is made of the flask shown in fig. 12. It resembles those used in the azotometer (fig. 9), and .is used in an exactly similar manner. The substance to be decomposed is placed in the space surrounding the inner cylinder, while in the latter is put the reagent (usually hydrogen peroxide). The flask is connected by means of a rubber tube with the side tube of the cock on A ; the latter hav- FlQ. 11. FIG. 12. 34 TECHNO-CHEMICAL ANALYSIS. ing first been filled with mercury up to the cock by raising B, care being taken that the flask be not warmed by the hand during handling. By inclining the flask, the reagent is caused to flow out of the cylinder and cause the evolution of gas, which expels a correspond- ing volume of air, and which hence may be measured after the mercury has been brought to a level in A and B. Under the name gas- volumeter is understood appa- ratus which is provided with a ' ' reduction-tube, " E, in addition to the parts already described, and which is con- nected by means of a T- tube and stout rubber tubing with A as well as with B (fig. 13). E has a capacity of about 130 cc., the upper ex- panded part holding 90 cc., and the lower part from 90 to 130 cc., graduated in 1/10 cc. The upper end of the tube may be closed either by a narrow capillary tube which can be sealed by fusion, or it may be provided with a cock, c, having a mercury seal. This tube is made so as to hold exactly 100 cc. of air, either fully saturated with moisture FIG. 13. GAS-VOLUMETftY. 35 or perfectly dry, at C. and 760 mm. This is effected by introducing into the tube a drop of water (for moist gases), or a drop of concentrated sulphuric acid (for dry gases), while c is open. B is then raised or lowered so that the mercury level will show in E the space that would be occupied by 100 cc. of air, moist or dry, at the prevailing temperature and pressure, c is then closed. If now B is elevated until the mercury in E stands at the 100-cc. mark, then the air will be com- pressed to the volume it would occupy at C. and 760 mm. Should now any gas from the " agitation-flask" C, or from the flask fig. 12, pass over into A, and the three tubes, A, E, and C, be so arranged that the mercury in E stands at the 100-cc. mark, while that in A is exactly at the same level, then the gas in A will occupy the vol- ume that it would have at C. and 760 mm. In all subsequent analyses, consequently, it is possible, by the use of this arrangement, to immediately effect the re- duction of the gas, and to read off at once the volume of gas without having to take note of the temperature or atmospheric pressure, as it requires but a few mo- ments to bring the mercury to a level in the tubes. In addition to its uses for the above-mentioned de- terminations of nitrates and nitrites, the nitrometer or gas-volumeter is also of particular service in two other classes of analytical operations, namely, (1) for such in which substances containing " active" oxygen are caused to react with hydrogen peroxide, and the lib- erated oxygen measured, e.g., 2KMn0 4 +3H 2 S04-f 5H 2 2 =K 2 S0 4 + 2MnS0 4 + 8H 2 0+ 10 ; or Mn0 2 H- 36 TECHNO-CHEMICAL ANALYSIS. H 2 S0 4 +H 2 2 =MnS0 4 +2H 2 + 20; and (2) the de- termination of carbonic acid in carbonates, the expul- sion of the gas being accomplished with hydrochloric acid, the completion of the expulsion requiring the observance of certain rules which will not be given here, but to which the reader is referred in Lunge's Chem.- Techn. Untersuchungsmethoden, I, p. 142 et seq. SPECIAL PAET. FUELS AND HEATING. FUELS are examined for technical purposes as to their fuel- or heat- value. In the case of solid or liquid fuels, the bomb- calorimeter is usually employed, in the form as first devised by Berthelot, or as modified by Mahler, Hempel, Langbem, and others. The principle upon which all are constructed is the same, and is as follows: A strong steel vessel, having a capacity of about 250 cc. (the bomb), and capable of resisting a pressure of at least 15 atmospheres when closed, serves for the combustion of the substance with compressed oxygen, which is forced in under a pressure of 15 atmos- pheres or over. The ignition is effected by means of the electric spark, the two platinum wires serving as the poles passing through the cover, the inner ends being connected by a spiral of thin iron wire which passes through the substance; on closing the circuit, the iron wire becomes heated to redness, and the combustion then proceeds. The bomb is, however, previously placed within a properly insulated calorimeter filled 37 38 TECHNO-CHEMICAL ANALYSIS. with water, and provided with a stirrer and a ther- mometer. The heat set free by the combustion is transferred to the calorimeter, the " water value" of which has been previously determined, and, after ap- plying various corrections, the increase in temperature of the water ascertained. For further details, see Lunge's Chem.-Techn. Untersuchungsmethoden, I, p. 234; and particularly also Langbein, Zeitschr. /. angew. Chemie, 1900, p. 1227. Anthracite coal, brown coal, etc., are, besides, exam- ined also as follows: The moisture is determined in a coarsely powdered average sample by drying at 110 C., best in a current of carbonic acid; furthermore, a determination of the ash is made, as well as of the coke remaining on heating in a covered platinum Cruci- ble, and the sulphur by ignition with magnesia and soda. Gaseous fuels are easily and rapidly examined by means of Junkers' calorimeter, a species of upright tubular boiler (see Lunge, Chem.-Techn. Untersu- chungsmethoden, I, p. 213, and II, p. 645). The upper heat value of a generator gas, the CO and H 2 content of which are known, is approximately ascertained by means of the following formula: 1 cm. = 30.6(CO +H 2 ) cal., CO and H 2 being replaced by the volume percentages of the respective gases. In all of these cases the upper and lower heat values are differentiated. The upper heat value, more prop- erly designated "heat of combustion," is the total heat liberated within the calorimeter, including the FUELS AND HEATING. 39 latent heat of the aqueous vapor, as the latter is of course condensed in the calorimeter to water. This latter amount is, however, of no value practically, as in all technical processes of combustion the water always escapes as vapor.- The lower, or actual, heat value is hence obtained when from the upper heat value we subtract the latent heat already existing in the fuel together with that of the water formed during the combustion. To obtain this result, both the con- tent of hygroscopic water and the quantity present in the dry substance must be ascertained by analysis. Technical analysis is also extended to the investiga- tion of smoke-gases. These are usually examined for their carbonic-acid content, which is best done by the aid of the Orsat apparatus (page 12). With this, should it be necessary, the carbonic oxide and oxygen may also be determined. Furthermore, under the names "dasymeter," " oekonometer," etc., apparatus have been constructed which utilize the circumstance that the specific gravity of a smoke-gas is the higher the greater the quantity of carbonic acid it contains, and that by means of a "gas-balance" the carbonic- acid content may therefore be ascertained with suffi- cient exactitude for practical purposes without analysis, by the simple reading of an index. WATER. Water, in technical analysis, is chiefly considered in reference to its use in steam-boilers. We have here simply the question of determining either the total, or 40 TECHNO-CtJEMWAL ANALYSIS. several individually, of the mineral constituents that remain on evaporation of the water. Organic impuri- ties in large quantities, free acids, etc., occur so seldom in water that, for the above-mentioned purposes, they need scarcely be considered. Alkalies (carbonates or chlorides), too, are found in water in very small quan- tity; water containing notable amounts of these are in fact classed among the mineral " waters," and need not be considered here. The constituents to which special attention must be paid are the calcium and magnesium compounds, which occur in water as carbonates (or bicarbonates) and sulphates, and which make the water " hard/' The hardness is frequently indicated in degrees, the total calcium and magnesium compounds being expressed in the terms of CaO equivalent to them. A German degree of hardness corresponds to 1 part of CaO in 100,000 parts of water. In France a degree of hard- ness is equivalent to 1 part of CaC0 3 in 100,000; while in England i j is 1 part of CaC0 3 in 70,000 parts of water. The sum of the units of all the earthy alkalies is designated as total hardness; the term permanent hardness is employed to express that which remains after prolonged boiling of the water, filtering, and adding sufficient distilled water to bring the whole to the original volume; while the term temporary hardness is used to express the difference between the total and permanent hardness, it being chiefly caused by the separation of calcium carbonate. The hardness of water was formerly generally, and WATER. 41 is often even yet, ascertained by Clark's method, which is based upon the fact that on adding an alcoholic potassa-soap solution to the water to be tested, it precipitates the salts of the alkaline earths, and, on shaking, affords no persistent foam antil the precipita- tion is perfectly complete. The quantity of soap solution used up is, therefore, a measure of the hard- ness of the water. But this, nevertheless, is not directly proportional to the quantity of soap solution used up: it must be ascertained by reference to tables prepared by purely empirical methods (see Lunge, Chem.-Techn. Untersuchungsmethoden, I, p. 710), which, of themselves, introduce an element of uncertainty that is even in- creased by various other circumstances. This method, of course, affords no indication as to what individual sub- stances are present. If to this be added the fact that the performance of the test requires considerable time, because the mixture must be thoroughly shaken after each addition of soap solution, and towards the end of the operation a period of five minutes must be allowed to elapse between the successive additions in order to see whether the foam persists, it will be seen that this method can not be recommended in prefer- ence to the more recent ones, which are not only sim- pler, but more accurate as well. The following methods are far better: 1. Determination of the total alkalinity, corresponding to the temporary hardness, excepting in such cases where notable quantities of sodium bicarbonate are present, as in the case of mineral waters or other 42 TECHNO-CHEMICAL ANALYSIS. waters which have been treated with soda. A small quantity of methyl-orange solution is added to 200 cc. of the water just to incipient yellowness, and then 1/5-normal hydrochloric acid is added until the color changes to a pale pink. Every cubic centimeter of the 1/5-normal acid used up is the equivalent of 0.01 grm. of CaC0 3 ; hence in 200 cc. of the water 0.05 grm. of CaC0 3 per liter is indicated, or 2.8 degrees of hardness on the German scale. The total hardness may already be approximately ascertained by evaporating 100 cc. of the water, igniting the residue with the addition of some ammo- num carbonate, and multiplying the weight of the ignition-residue, expressed in milligrammes, by 0.56; e.g., were 0.025 grm. obtained, the hardness would be 25X0.56=14. 2. A few drops of acid are added to 200 cc. of water neutralized as in 1 with hydrochloric acid, the liquid evaporated down to 50 or 60 cc., cooled, then washed into a 100-cc. flask, carefully neutralized, boiled once more, 40 cc. of a mixture of equal parts of 1/10-normal NaOH and 1/10-normal Na 2 C0 3 added, the liquid again boiled, allowed to cool, and then made up to the mark with distilled water. The liquid is now passed through a filter, and the excess of the alkali determined in 50 cc. of the filtrate by titrating with 1/10-normal hydrochloric acid, using methyl orange as the indicator. By multiplying the number of cubic centimeters used up by 2 and deducting the result from 40 cc., the quantity of alkali required to precipi- WATER. 43 tate the earthy alkalies in 200 cc. of the water is ascer- tained, and this multiplied by 1.4 gives the total hard- ness in German degrees. 3. If the earthy alkalies obtained in 1, calculated as CaO, be deducted from that obtained in 2, we obtain a measure of the " permanent" hardness, i.e., for the calcium sulphate present. In this case, instead of the German degree of hardness (or 0.028 per liter), we would always calculate 0.068 gm. CaS04 per liter. For the determination of magnesia, should this be required, as well as of iron, chlorides, etc., the usual methods of analytical chemistry are employed. INORGANIC CHEMICAL MANUFACTURING IN- DUSTRY. SULPHUROUS AND SULPHURIC ACIDS. The raw materials that serve as the source for the manufacture of sulphurous acid are elementary sul- phur, pyrites, zinc blende and other sulphides, and also the hydrogen sulphide obtained in the manufacture of ammonium sulphate. i. Sulphur. The kind most usually to be considered is the Sicilian crude sulphur. It is generally examined only as to its ash content, and for this purpose 10 grm. are burned in a tared porcelain dish. It is only occasion- ally examined for arsenic (from which it should be perfectly free), selenium, and bituminous substances. In very accurate analyses the sulphur is determined directly by dissolving in carbon disulphide and deter- mining the specific gravity of the solution (see Unter- suchungsmethoden, I, p. 240. When powdered sulphur is to be used for dusting vines, its degree of fineness must be considered, and this is ascertained by means of Chancel's sulphurimeter. This apparatus consists of a well-stoppered tube gradu- ated in 100 degrees, and in which 5 gm. of sulphur 44 INORGANIC CHEMICAL MANUFACTURES. 45 are shaken with 25 cc. of anhydrous ether, an observa- tion being then made as to at what mark on the scale the sulphur has settled; the finer the powder the less will it sink. Ordinary ground sulphur is indicated by 50 to 55, and the finest quality by 70 to 75, Chancel. Another form of elementary sulphur is gas-sulphur, i.e., the gas-purifying mass used in gas-works, and which contains, besides ferric oxide, ammonium salts, cyanogen compounds, tar, etc., also 50 per cent, and more of free sulphur. A determination of the total sulphur is not necessary in this case, but only that which is obtained in the form of S0 2 by combustion. For this purpose about 0.4 grm. of the substance is heated in a glass tube in a current of air, and the gas con- ducted into an absorption fluid, by which the 862 is retained. The most suitable liquid for this purpose is hydrogen peroxide, the reaction taking place as fol- lows: H 2 02+S02 = H 2 S04. The resulting free acid is then titrated with normal soda. 2. Pyrites. These are examined for moisture by drying at 105 C.; but particularly for its sulphur con- tent. This is most frequently accomplished by de- composition by the wet way, using a mixture of 3 vol- umes of nitric acid sp. gr. 1.4 and 1 volume of concen- trated hydrochloric acid. Of this mixture 10 cc. are taken for 0.5 gin. of the pyrites, the operation being conducted at a moderate heat, until the reaction is at an end and no more particles of unoxidized sulphur are visible. The mass is then evaporated to dryness, and the nitric acid decomposed by adding hydrochloric 46 TECHNO-CHEMICAL ANALYSIS. acid and again evaporating, after which the residue is dissolved in diluted hydrochloric acid. The iron is then removed by precipitating with ammonia in mod- erate excess at a temperature between 60 and 70 C., filtering off and thoroughly washing the ferric hydrox- ide, and precipitating the sulphuric acid in the filtrate by boiling with the gradual addition of barium-chloride solution. The clear liquid may already be decanted through a filter in from twenty to thirty minutes; the precipitate of barium sulphate, however, is first washed by decantation with boiling water, then thoroughly washed on the filter itself, dried, and ignited, the filter too being burned in a platinum spiral or in a crucible. The ignited BaS0 4 should have a pure white color, and be in very fine, pulverulent form; 1 part corresponds to 0.1373 part sulphur. The decomposition of pyrites is also frequently ac- complished by the dry way, the method formerly em- ployed being fusion with soda and saltpeter or potassium chlorate, while nowadays the fusion is effected with sodium peroxide. In this case the iron remains as a residue when the fused mass is dissolved; for the rest, the process is then carried out as above detailed. Many methods have been devised for the volumetric determination of combined sulphuric acid, but none of them are used for the accurate determination of sul- phur in the ores containing it; nor do they afford any great saving of time as compared with the gravimetric methods, in practiced hands, for determining the sulphur as barium sulphate, INORGANIC CHEMICAL MANUFACTURES. 47 At times arsenic also is determined in pyrites, and best by fusion with soda and saltpeter, whereby the arsenic is converted into an arsenate, which is then precipitated with silver nitrate as silver arsenate. The precipitate is washed, dissolved in nitric acid, and the silver hi it determined by titration with ammonium- sulphocyanate solution, using ferric sulphate as the indicator. 1 cc. of a 1/10-normal sulphocyanate solution indicates 0.0025 gm. of arsenic. Copper is most usually determined in pyrites by elec- trolytic methods, after it has been brought into solution by decomposing the ore with nitric acid, or in some other manner. Zinc, carbonates of the earths, and carbon are but seldom determined. 3. Zinc blende is decomposed just like pyrites, and the sulphur in it similarly determined, but in addition the zinc also, most generally by titration with sodium- sulphide solution. This must, however, be preceded by a rather troublesome purification, in order to remove any lead, cadmium, etc., present. In the manufacture of sulphuric acid there serve as raw materials, furthermore, sodium nitrate and nitric acid, which are to be tested as will be detailed in the chapter devoted to the manufacture of nitric acid. For the factory control we require: 1. The examination of the cinders of the pyrites or blende for any residual sulphur. For this purpose the decomposition is usually effected by the dry way. The decomposition is most speedily accomplished by fusion with a weighed quantity of sodium bicarbonate 48 TECHNO-CHEM1CAL ANALYSIS. of known titer in a nickel crucible, and at a gentle heat, whereby the sulphur is converted into sulphate by the atmospheric oxygen, and at the expense of the sodium bicarbonate, so that the quantity formed may be determined by titrating back the filtered solution of the melt with normal hydrochloric acid and methyl orange. When effecting the solution, however, a large quantity of sodium chloride must be added, other- wise finely divided ferric o:dde always passes through the filter, and renders titration almost impossi- ble. This process can not be employed, moreover, for cinders from pyrites rich in zinc, or from zinc blende, but the procedure must be that employed in the case of zinc blende (page 47). 2. The calcination gases are examined as to their content of sulphur dioxide by Reich's method, page 23, and also for their total acid content by Lunge's method, as detailed on page 26. 3. The acid issuing from the foot of the Gay-Lussac towers during the manufacture of sulphuric acid, and known as "nitrose," must be examined as to the con- tent of nitrogen acids; and so too must the chamber acids be frequently examined. It is usually sufficient to determine the nitrous acid which, in the form of nitro- sylsulphonic acid, S0 5 NH, is dissolved in the sulphuric acid. This is done by allowing the acid to be tested to run from a burette into a measured volume of standardized potassium-permanganate solution until the latter is just decolorized, nitric acid being formed INORGANIC CHEMICAL MANUFACTUR1 thereby; hence every 16 of oxygen yielded by ^ manganate solution indicate 47 of HN0 2 . The total nitrogen, i.e., that from the nitric and nitrous acids, is determined in a nitrometer (see page 30). The end-products of this industry are, besides liquid sulphur dioxide, which will not be here considered, the following: I. Lyes used in the manufacture of sulphite cellulose. In these the total content of sulphurous acid is ascer- tained by titration with iodine solution; and the free sulphurous acid (i.e., that in excess of what is required to form NaSOs) by titrating with normal soda-lye, using phenolphtalein as the indicator. II. Sulphuric acids of various strengths. The value of these depends, first and foremost, upon their content of actual sulphuric acid, H 2 S0 4 ; and in the case of fuming sulphuric acid, on the content of sulphuric anhydride, S0 3 . In addition, however, the impuri- ties in sulphuric acid must in many cases be deter- mined also. The sulphuric-acid content is in most cases deter- mined quite simply by taking the specific gravity with an araeometer which shows the strength in either degrees or percentage of H 2 S04. Of the araeometers, the one most generally used is that of Baume. The following table shows the relationship between the specific gravity, the sulphuric-acid content, and the degrees Baume: 50 TECHNO-CHEMICAL ANALYSIS. 4 IS > g If gl X* I Per Cent. H 2 S0 4 . >> ! 11 02 VflJ *>Q3 Per Cent. HaSO,. >> j c3 \& o> g jppo Per Cent. H 2 S0 4 . .01 1.4 1.57 1.31 34.2 40.35 1.60 54.1 68.51 .02 2.7 3.03 1.32 35.0 41.50 1.61 54.7 69.43 .03 4.1 4.49 1.33 35.8 42.66 1.62 55.2 70.32 .04 5.4 5.96 1.34 36.6 43.74 .63 55.8 71.16 .05 6.7 7.37 1.35 37.4 44.82 .64 56.3 71.99 .06 8.0 8.77 1.36 38.2 45.88 .65 56.9 72.81 1.07 9.4 10.19 1.37 39.0 46.94 .66 57.4 73.64 1.08 10.6 11.60 1.38 39.8 48.00 .67 57.9 74.51 1.09 11.9 13.00 .39 40.5 49.06 .68 58.4 75.42 1.10 13.3 14.35 .40 41.2 50.11 .69 58.9 76.30 1.11 14.2 15.71 .41 42.0 51.15 .70 59.5 77.17 1.12 15.4 17.01 .42 42.7 52.15 .71 60.0 78.04 1.13 16.5 18.31 .43 43.4 53.11 .72 60.4 78.92 1.14 17.7 19.61 .44 44.1 54.07 .73 60.9 79.80 1.15 18.8 20.91 .45 44.8 55.03 .74 61.4 80.68 1.16 19.8 22.19 .46 45.4 55.97 .75 61.8 81.56 1.17 20.9 23.47 .47 46.1 56.90 .76 62.3 82.44 1.18 22.0 24.76 .48 46.8 57.83 .77 62.8 83.32 1.19 23.0 26.01 .49 47.4 58.74 .78 63.2 84.50 1.20 24.0 27.32 .50 48.1 59.70 .79 63.7 85.70 1.21 25.0 28.58 .51 48.7 60.65 .80 64.2 86.80 1.22 26.0 29.84 .52 49.4 61.59 .81 64.6 88.30 1.23 26.9 31.11 .53 50.0 62.63 .820 65.0 90.50 1.24 27.9 32.28 .54 50.6 63.43 .825 65.2 90.80 1.25 28.8 33.43 .55 51.2 64.26 .83 65.5 92.10 1.26 29.7 34.57 .56 51.8 65.08 1.835 65.7 93.43 1.27 30.6 35.71 .57 52.4 65.90 1.840 65.9 95.60 1.28 31.5 36.87 1.58 53.0 66.71 1.8415 97.70 1.29 32.4 38.03 1.59 53.6 67.59 1.8385 99.95 1.30 33.3 39.19 The specific gravity must be taken at 15 C.; at other temperatures a correction must be made. Of course, the table holds good only for perfectly pure acids, although it is only in the highest concentrations that there are notable differences in strength between the pure and commercial acids of the same specific gravity. A more accurate determination of the sulphuric acid is effected by titration. This is, above all, necessary in INORGANIC CHEMICAL MANUFACTURES. 51 the case of the highly concentrated acids, in which the specific gravity no longer increases in proportion to the concentration. The titration of the sulphuric acid is accomplished most simply, and best, by means of a normal solution of caustic soda, with methyl orange as the indicator, whereby the carbonic-acid content of the soda-lye need not be considered, which thus permits the operation to be carried out very rapidly, and in the cold. This indicator is reddened by strong acids; on the other hand, towards weak acids, like carbonic acid, it is insensitive. Alkalies color it yellow. The end of the reaction is indicated by a brownish, mixed color, which is changed by a drop of acid to a reddish, and by a drop of alkali to a yellowish, color. The soda solution used for titrating is first standard- ized by normal hydrochloric or sulphuric acid, using chemically pure soda freed from moisture and carbonic acid by heating at 300 C. Other operators prefer to use phenolphtalein, which affords a very sharp color change from colorless to a rose-red as soon as the acid is neutralized by the alkali and a slight excess of the latter supervenes. As phenol- phtalein, however, is decolorized by carbonic acid, the titration must be carried out while the liquid is con- stantly boiling, which makes it absolutely necessary to discard the use of glass vessels, and which thus makes the operation more inconvenient and protracted. Or, it is necessary to employ perfectly pure, carbonic- acid-free lyes, which in the case of soda-lye it is a matter 52 TECHNO-CHEMICAL ANALYSIS. of some difficulty to assure. It is much more convenient to employ baryta solution, which must not, however, be prepared of a definite strength, but must be standard- ized empirically. On this account the employment of methyl orange is greatly to be preferred, although it requires somewhat more experience to recognize when the color change takes place. It must not be overlooked that any add impurities in the sulphuric acid (nitric acid, hydrochloric acid) are also calculated as sulphuric acid when titrating; these must be separately determined, therefore, and the proper allowance made for them. Of the impurities in sulphuric acid of commerce, the following are the most frequently to be considered: a. Nitrogen acids (nitric acid and nitrous acid, the latter being present in the form of nitrosylsulphuric acid, SOsNH). These acids are best determined qualita- tively by adding a 1-per-cent. solution of diphenylamine in concentrated sulphuric acid, which develops a blue coloration. The quantitative determination is effected as in the case of "nitrose" (see page 48). b. Selenium is recognized by adding a solution of ferrous sulphate, with which it affords a brownish-red precipitate. c. Lead is detected by diluting with water, very small quantities being precipitated, on adding alcohol, in the form of lead sulphate, which should be further examined with the blowpipe. d. Iron is recognized by boiling with a drop of pure nitric acid, diluting, cooling, and adding a solution of INORGANIC CHEMICAL ANUFACTURES. 63 potassium sulphocyanate; a red color develops if iron is present. e. Arsenic, above all, should not be present in sul- phuric acid which, in remedial agents, may be ingested into the human system. - A simple, and usually satisfactory, test for it is that of Marsh, which is performed as follows: A piece of chemically pure zinc is introduced into a flask pro- vided with a two-holed cork, one hole of which bears a funnel reaching almost to the bottom of the flask. Through this funnel a little pure diluted sulphuric acid is poured, and the hydrogen evolved escapes through a tube bent at a right angle, and inserted in the other hole in the cork; the outer end of the tube is drawn out to a point. When it is certain that all the air has been expelled from the flask, and that no explosion is there- fore likely, the jet of gas issuing from the tube is ignited, and the flame allowed to impinge on a white porcelain surface. A little of the acid to be tested (and pre- viously diluted) is now poured in. If any arsenic is present, a black spot will form on the porcelain. For more accurate purposes the Marsh-Berzelius test is employed. In this the procedure is the same as above, but the gas is freed from hydrogen sulphide by lead acetate, then dried by calcium chloride, and passed through a tube of difficultly fusible glass which is heated to redness by a gas-flame. If any arsenic is present, the arsine formed is decomposed at the heated point, and there is deposited a grayish-black mirror, the in- tensity of which is a measure of the quantity of arsenic 54 TECHNO-CHEMWAL ANALYSIS. present. It is imperatively necessary, however, under all circumstances, that a parallel test be made with pure acid in order to be certain that neither the zinc nor any other substance that may be present gives the arsenic test. Reinsch's test is also frequently used. This consists in heating the solution with a piece of bright copper foil, which, if arsenic is present, becomes coated with a grayish deposit of copper arsenide. In Gutzeit's test the acid is treated with arsenic-free zinc in a test-tube covered with a cap of filter-paper on which a drop of a 5-per-cent. silver-nitrate solution has been allowed to dry; if arsenic is present the spot first becomes yellow,, then black. It is best to place under the cap a plug of cotton moistened with lead-acetate solution. Fuming sulphuric acid (oil of vitriol) is weighed off in a small glass bulb provided with two long-drawn-out points, or in a pipette provided with a glass cock, then allowed to run out into a large excess of water, and the total acid determined by titration. This is calculated as S0 3 ; the remainder is taken as water, and for every 18 parts of water there are calculated 80 parts of S0 3 , the residual S0 3 being calculated as free anhydride. This, however, assumes that there are no other im- purities present which, otherwise, must be determined and deducted from the acid calculated from the water difference as above. INORGANIC CHEMICAL MANUFACTURES. 55 NITRIC ACID. Of the raw materials, saltpeter and sulphuric acid, the latter has already been mentioned (see page 49 et seq.). Saltpeter (soda-saltpeter, Chili saltpeter) is fre- quently examined only as to its refraction, i.e., for its content of sodium chloride, sodium sulphate, water, and insoluble substances, all else being assumed to be sodium nitrate. This is decidedly improper, because any potassium nitrate, should this be present, must be regarded as injurious, for, on account of its higher atomic weight, it yields less nitric acid than does sodium nitrate. Furthermore, the perchlorate (and what is of less importance, the iodate) is also here calculated as nitrate. In spite of this, however, this mode of " analy- sis " is still widely used as a standard in the wholesale trade. The moisture is determined by drying the saltpeter at 130 C.; and the substances insoluble in water by dissolving 50 grm., filtering, washing, and drying the residue on a tared filter at 130 C. The solution is made up to one liter, and the NaCl and Na 2 S0 4 in it determined by the usual methods. Far more accurate, however, is the direct determina- tion of the nitrate nitrogen, which is the procedure always followed by chemical manufacturers and agri- cultural chemists, and for which the following methods are chiefly used: 56 TECHNO-CHEMICAL ANALYSIS. 1. Ulsch's Method. Dissolve 20 grm. of the saltpeter in sufficient water to make one liter, and pipette off 50 cc. (equivalent to 1 grm. of substance) into a liter flask which is to be covered with a funnel. To the con- tents add 1 grm. powdered iron (iron-by-hydrogen) and 20 grm. sulphuric acid diluted with twice its weight of water, and heat for ten minutes to boiling, whereby all the nitrate is converted into ammonium sulphate. Now add 150 cc. water and 50 cc. of caustic soda-lye of sp. gr. 1.25, close the flask with a rubber stopper bearing a tube expanded above the stopper into a bulb, and reaching into a receiver containing normal hydro- chloric acid. The flask is then heated until all the ammonia is expelled, and absorbed by the acid in the receiver. The acid is titrated like normal lye, with methyl orange. The hydrochloric acid used up corre- sponds to the saltpeter content, every cubic centimeter of 1/5-normal acid being equivalent to 0.01702 gm. of NaN0 3 . 1 gm. of sodium nitrate would require 58.75 cc. of the acid. 2. Lunge's Nitrometric Method. The apparatus best adapted for this is the nitrometer with agitation vessel described on page 33, and which is best converted into a gas- volumeter by adding a " reduction" tube, so as to make it unnecessary to take account of the temperature and atmospheric pressure. Using a gas- measuring tube having a capacity of 130 cc., weigh off 0.35 grm. of the saltpeter and place it in the beaker of the agitation vessel, and then proceed as already de- tailed (loc. cit.). Every cubic centimeter of the nitric INORGANIC CHEMICAL MANUFACTURES. 57 oxide evolved, dried, and reduced to C. and 760 mm. indicates 0.003789 grm. of NaN0 3 . 3. Schlosing-Grandeau- Wagner's Method. This con- sists in boiling a liquid containing a nitrate with hydro- chloric acid and ferric chloride, the total nitrogen being thus evolved as nitric oxide which is measured over water, the NaN0 3 being then calculated as in the method previously described. Determination of Perchlorate. Almost all of the methods known are based upon the reduction of the perchlorate to chloride and its determination in this form, in which case, of course, the chloride originally present must be deducted from the total. The best mode of procedure is to fuse the saltpeter in an iron or nickel crucible with soda, generally also with the addi- tion of some other substance, like manganese dioxide or powdered iron, whereby the KC104 is converted into KC1, which is then determined either gravimetrically or volume trically. The nitric acid itself is next examined as to its con- tent of HN0 3 , and frequently only by means of the araeometer. The table on p. 58 gives the specific gravities of perfectly pure nitric acid of varying strengths; for the comparison between degrees Baume and specific gravities see the sulphuric-acid table page 50. In the case of nitric acid, however, the employment of the araeometer introduces far greater errors than when it is used for sulphuric acid, hydrochloric acid, and in most other cases, as the concentrated nitric acids as a 58 TECHNO-CHEMICAL ANALYSIS. Specific Grav- ity. Per Cent. HNO 3 . Specific Grav- ity. Per Cent. HNO 3 . Specific Grav- ity. Per Cent. HNO 3 . Specific Grav- ity. Per Cent. HNC-3. 1.01 1.90 1.14 23.31 1.27 42.87 1.40 65.30 1.02 3.70 1.15 24.84 .28 44.41 1.41 67.50 1.03 5.50 1.16 26.36 .29 45.95 1.42 69.80 1.04 7.26 1.17 27.88 .30 47.49 1.43 72.17 1.05 8.99 1.18 29.38 .31 49.07 1.44 74.68 1.06 10.68 1.19 30.88 .32 50.71 1.45 77.28 1.07 12.33 1.20 32.36 .33 52.37 1.46 79.98 1.08 13.95 1.21 33.82 1.34 54.07 1.47 82.90 1.09 15.53 1.22 35.28 1.35 55.79 1.48 86.05 1.10 17.11 1.23 36.78 1.36 57.57 1.49 89.50 1 11 18.67 1.24 38.29 1.37 59.39 1.50 94.09 1.12 20.23 1.25 39.82 1.38 61.27 1.51 98.10 1.13 21.77 1.26 41.34 1.39 63.23 1.52 99.67 rule always contain nitrogen tetroxide in solution, the quantity being seldom less than 1 per cent., but more generally several per cent., which makes its strength when taken with the araeometer seem greater than it actually is. It is hence more frequently necessary to resort to titration in the case of nitric acid than in the case of sulphuric acid, the titration being carried out as detailed under Sulphuric Acid (see page 50 et seq.). It must not be overlooked, however, that the nitrogen di- oxide also exerts an action in this case, and that besides making a determination of the total acid by means of normal alkali, the nitrogen dioxide must also be deter- mined. This is accomplished by running the acid into a measured quantity of titrated potassium-perman- ganate solution, just as in titrating " nitrose" (page 48). Every 16 parts of oxygen given up by the permanga- nate indicates 0.09208 of N 2 4 . Mixtures of sulphuric acid with nitric acid and lower nitrogen acids, such as are technically employed in INORGANIC CHEMICAL MANUFACTURES. 59 the form of mixed acid or waste acid in the manufacture of tar dyes and explosives, are examined as follows : The sulphuric acid is first determined by heating 2 to 3 grm. with the addition of a little water on the water-bath, until the nitrous odors have ceased, when only sulphuric acid will be present, which is then titrated with normal soda and methyl orange. The lower nitrogen acids are determined, as detailed on page 48, by running in the acid into permanganate solution, and calculating them as N 2 4 . The nitric acid is found by titrating the total acid and deducting from it the sulphuric acid and the N 2 4 found as above. The titration may be effected by means of methyl orange, even though the indicator is rapidly decom- posed by nitrous acid, if the methyl orange is added just before the neutralization with soda, or if the acid be supersaturated with the soda, the indicator then added, and the liquid titrated back with normal acid. SULPHATE. By this designation is understood both potassium sulphate and sodium sulphate, which are obtained by decomposing NaCl or KC1 with sulphuric acid, with the evolution of hydrochloric acid. The chlorides hence constitute the raw materials from which the products are obtained. Common Salt (Rock Salt). This is examined chiefly for its moisture content (by cautiously heating, because it crepitates) , and for calcium sulphate, and occasionally also for magnesia. 60 TECHNO-CHEMICAL ANALYSIS. Denaturized salt may contain various substances ; the one here considered is sodium sulphate. The deter- mination is most simply made by estimating the chlorine of the chloride as below detailed. Potassium Chloride. See under potassium salts. Sulphate. One grm. is usually examined for free acid, by adding normal soda and methyl orange to neutralization. The total acidity is calculated as S0.3, including that due to HC1, NaHS0 4 , Fe 2 (S0 4 ) 3 , etc., present. Sodium Chloride. Neutralize with a quantity of soda equal to that employed in 1, add a little potassiurn- chromate solution, and titrate with decinormal silver- nitrate solution; 1 cc. of the latter corresponds to 0.00585 grm. NaCl. The sulphate to be used in the manufacture of the finer kinds of glassware is also examined as to its iron content, by reducing the iron salt with sulphuric acid and zinc to a ferrous condition, and then titrating with potassium permanganate. HYDROCHLORIC ACID. In the factory control of the manufacture of hydro- chloric acid the chimney-gases must be examined as to their content of acid, which is to be calculated as HC1. A certain quantity of the chimney-gases is drawn off and passed through water, in which the S0 2 present in the gases is directly oxidized to H 2 S0 4 by means of chlorine-free hydrogen peroxide, and the total acid deter- mined by titrating with soda-lye and methyl orange. If INORGANIC CHEMICAL MANUFACTURES. 61 necessary, the chloride content is separately deter- mined by titrating with silver nitrate (see above under Sodium Chloride). Hydrochloric acid itself is usually examined as to its acid strength by means of the araeometer, the following table being employed for the purpose (for the com- parison between the Baume degrees and the specific gravities, see under Sulphuric Acid, page 50) ; the table serves, of course, only for pure acids, and at the tem- perature of 15 C. Specific Per Specific Per Specific Per Specific Per Grav- Cent. Grav- Cent. Grav- Cent. Grav- Cent. ity. HC1. ity. HC1. ity. HC1. ity. HC1. 1.01 2.14 1.06 12.19 1.11 21.92 1.16 31.52 1.02 4.13 1.07 14.17 1.12 23.82 1.17 33.46 1.03 6.15 1.08 16.15 1.13 25.75 1.18 35.39 1.04 8.16 1.09 18.11 1.14 27.66 1.19 37.23 1.05 10.17 1.10 20.01 1.15 29.57 1.20 39.11 The hydrochloric acid may, of course, be titrated with soda-lye, as in the case of sulphuric acid (p. 49 et seq.), when the free sulphuric acid present is also cal- culated as hydrochloric acid; or by neutralizing with sodium carbonate and titrating with potassium chromate and silver solution (see page 60) . Of the impurities, special attention is directed to arsenic (see page 53), iron (page 52), and sulphuric acid (which is to be determined as BaS0 4 , see pp. 45 and 46), taking care not to overlook any Na 2 S0 4 that may remain in the evaporation-residue). 62 TECHNO-CHEMICAL ANALYSIS. SODA. The raw materials for the manufacture of soda by the Leblanc process are sulphate (page 59), limestone (page 67), and coal (page 38). For the factory control in this process the crude soda- ash melt is examined as to its physical characteristics, and then chemically, chiefly for its content of alkali, by titrating the solution with normal acid and methyl orange; furthermore for its content of sodium sul- phide, by titrating with iodine solution (1 cc. N-iodine solution is the equivalent of 0.003908 Na 2 S); and finally, for sodium sulphate, the latter being most simply determined gravimetrically by precipitation with barium chloride. The crude lyes are also exam- ined for the same substances, and at times also for sodium ferrocyanide, by oxidation with a just sufficient quantity of chlorinated-lime solution and titration with a copper-sulphate solution empirically standard- ized against pure potassium ferrocyanide. The end- point of this reaction is recognized by bringing together a drop of the liquid on a porcelain surface with some dilute solution of ferrous sulphate, the color chang- ing from a blue to a reddish when the copper is in excess. In the carbonated lyes there is moreover deter- mined the carbonic acid of the bicarbonate, and most simply by adding phenolphtalein, cooling to nearly C., and titrating with hydrochloric acid until the red color just disappears. The number of cubic centi- meters of 1/5-normal hydrochloric acid used up we INORGANIC CHEMICAL MANUFACTURES. 63 will designate as a. Now add methyl orange followed by more hydrochloric acid, until the liquid becomes red. The cubic centimeters of 1/5-normal acid required for this we will term b. ba will then give the soda pres- ent as NaHC0 3 ; 2b will give that present as Na 2 C0 3 ; and a + b the total soda present. The leach-residue is chiefly examined for "utilizable " soda by digesting it with ten times its weight of warm water, treating the clear liquid with carbonic acid until H 2 S begins to be evolved, then concentrating by evaporation, filtering off the CaC0 3 , and titrating the filtrate with normal acid and methyl orange. In the factory control of the ammonia-soda process, the rock salt, brine, limestone, coke, etc., are examined as above; in addition, however, the gas liquor is exam- ined as detailed on page 85. The sodium chloride in the ammoniacal brine is determined as on page 60, and the ammonia either by titration or, very accurately, by driving it over into normal hydrochloric acid by boiling, as detailed on page 56. The bicarbonate in crude bicarbonate is estimated as on page 62. The lime-kiln gases are examined for carbonic acid with the gas-burette, as described on page 8. For the factory control of the manufacture of caustic soda, the examination of the crude caustic lye is of im- portance, in addition to that of the substances already mentioned. The alkalimetric titer is ascertained by means of normal hydrochloric acid and methyl orange; then the NaOH and the Na 2 C0 3 are determined by first ascertaining the number of cubic centimeters of normal 64 TECHNO-CHEMICAL ANALYSIS. hydrochloric acid used up (and at a low temperature), employing phenolphtalein (this we will term a), and then determining the further number used up, using methyl orange (which we will designate as 6), as de- scribed on pp. 62 and 63. In this case a b is equiva- lent to the NaOH, while 26 represents the Na 2 CO 3 . Lastly, the sulphide is determined by titrating with iodine solution, as described on page 62. The lime deposit also should be examined as to its content of soda compounds, by boiling and titrating. Electrolytic alkali lyes are examined like bleaching- liquors (page 68). The commercial products of the soda industry are as follows: Calcined Soda. This consists essentially of anhy- drous sodium carbonate, the content (alkalimetric titer) of which is ascertained by igniting 2.65 grm., dis- solving, and titrating with normal hydrochloric acid and methyl orange in the cold. Every cubic centimeter of normal acid indicates 2 per cent, of Na 2 C0 3 . The Ger- man degrees indicate the percentage of Na 2 C0 3 ; the English, the percentage of Na 2 ; and the French, as the Descroizilles, indicate how many parts of H 2 S0 4 are neutralized by 100 parts of the soda. Chemically pure sodium carbonate would indicate 100 German degrees, 58.5 English degrees,* or 92.45 degrees Descroizilles. The commercial soda is moreover tested as to its volu- metric weight, technically, by transferring 5 or 6 sepa- * In actual practice, English commercial analysts frequently state the number by J to 1 degree higher than here given. INORGANIC CHEMICAL MANUFACTURES. 65 rate portions of the anhydrous, ground soda to a tared vessel of stout glass, ground off smooth at the top, and of known capacity, the powder being each time pounded down and the excess scraped off, the quantity remain- ing being then ascertained- by weighing back. By this process the volume which 100 cc. of the ground soda occupies is ascertained. A complete analysis of the soda is rarely necessary; it comprises the determination of the insoluble matter present, the chlorides, sulphate, bicarbonate, caustic soda, and sodium sulphide, so far as these are present, but it never happens that these are all present (com- pare page 62 et seq.). Crystal Soda is at times adulterated with large quan- tities of Glauber's salt. It should never show less than 34 per cent, of Na 2 C0 3 by titration. Caustic Soda. It is not an easy matter to take a sample of this, because the substance usually occurs in large blocks, from having been poured into iron drums while fluid, and its composition varies at different parts of the drum. If the containers in which it is kept are not absolutely air-tight, it attracts moisture and car- bonic acid from the air, so that a false crust forms which must be removed by scraping before the quantity intended for analysis is weighed off. After the scraping has been done, 50 grm. are dissolved in sufficient water to make 1 liter, and the total alkali titrated in 50 cc. of the solution (2.5 grm. of the substance) by means of normal acid and methyl orange. In another 50 or 100 cc. of the solution the sodium carbonate still present 66 TECHNO-CHEMICAL ANALYSIS is determined, and for most purposes with sufficient accuracy by consecutive titration with phenolphtalein and methyl orange (page 63) , but accurately, by the volumetric determination of the C0 2 according to Lunge and Marchlewsky (page 30). Bicarbonate is examined by the above-mentioned methods as to its content of Na 2 C03 (compare page 62) . CHLORINE INDUSTRY. In the small manufacturing process, as well as in the completion of the Weldon process, manganese dioxide is used, together with hydrochloric acid, for effecting the evolution of chlorine; the dioxide is tested as to its actual content of Mn0 2 as follows: Weigh off 1.0875 grm. of the manganese dioxide, very finely powdered and dried by heating for some time at 100 C., and introduce it into a flask, which is then closed with a Bunsen rubber" valve, or better yet, with a Contat apparatus, as shown in fig. 14, and which con- tains a small quantity of sodium- bicarbonate solution. To the man- ganese dioxide add 75 cc. of a solu- tion of 100 grm. pure ferrous sul- phate and 100 cc. of pure sul- phuric acid in 1 liter of water; the solution must be standardized against a titrated potassium-permanganate solution the same day it is used. Then close the flask, and INORGANIC CHEMICAL MANUFACTURES. 67 boil until the manganese dioxide is decomposed. The Contat apparatus is then adjusted in order that the liquid may cool without the possibility of any air com- ing into contact with it; when cool, the liquid is titrated back with permanganate solution, and the volume used up deducted from the volume equivalent to the 75 cc. of ferrous-sulphate solution. Every cubic centimeter of 1/2-normal permanganate solution corresponds to 0.02715 grm., or 2 per cent., Mn0 2 . Limestone is used in the production of caustic lime for manufacturing chlorinated lime, and in the regen- eration of the manganese dioxide in the Weldon process. The limestone is examined either by determining the CaO or the C02. The former is effected accurately enough by dissolving 1 grm. in 25 cc. normal hydro- chloric acid and titrating back with normal soda. Every cubic centimeter of normal acid used up repre- sents 0.028 grm. CaO, or 0.05006 grm. CaC0 3 . The carbonic acid is determined either by the loss in weight in a weighable apparatus containing the quantity of hydrochloric acid necessary for the decomposition, and provided as well with an apparatus for drying the C0 2 evolved; or more accurately, and at the same time more rapidly, by the volumetric method (page 30), which, of course, assumes that the proper apparatus is available. Caustic lime is examined for free CaO by slaking 100 grm. of the lime with enough water to make a thin cream (500 cc.), 100 cc. of which are diluted with water to make 500 cc., shaking, and titrating 25 cc. of the 68 TECHNO-CHEMICAL ANALYSIS. mixture ( = 1 grm. caustic lime) with phenolphtalein and normal hydrochloric acid, with thorough shaking, until the red color just disappears. Every cubic centi- meter of normal acid is equivalent to 0.02806 CaO. The chlorine gas, whether obtained by the Deacon process or electrolytically, must be examined for car- bonic acid. This is most simply effected by filling two burettes with 100 cc. each of the chlorine. In the one, the chlorine is absorbed by potassium iodide, and the iodine separated estimated with arsenic solution or thio- sulphate solution; every cubic centimeter of 1/10-normal titrating solution indicates 0.003545 grm. of chlorine, or 1.1228 cc. dry chlorine at C. and 760 mm.; the re- 760(273 +0 duction may be made by using the formula -77 AO ~ Q , (0 I JA Id t being the prevailing temperature and b the baro- metric pressure (/ is the vapor-tension at t). In the second burette the chlorine and the C02 are absorbed together by soda-lye, and the C02 ascertained by dif- ference. Electrolytic Lyes and Bleaching-fluids. Bleaching- fluids consist of mixtures of hypochlorites and chlorides, and generally also a little chlorate, hypochlorous acid, and at times alkali, either free or as carbonate. The electrolytic lyes contain the same constituents, but in entirely different proportions; in these lyes the caus- tic alkali preponderates. The analytical methods, however, are the same for both lyes. In bleaching-fluids, the most important constituent to be determined is the active chlorine, and in the same INORGANIC CHEMICAL MANUFACTURES. 69 manner as in the case of chlorinated lime (see below). In addition it may be also required to determine the free hypochlorous acid present. This is determined by adding potassium iodide, when the following reactions take place: 1. NaOCl+2KI+H 2 = NaCl+2KOH+I 2 . 2. HOC1 +2KI = KC1 +KOH +I 2 . The iodine liberated in these reactions is neutralized by thiosulphate, and the two reactions then titri- metrically differentiated by the fact that in reaction 1 twice as much KOH is liberated as in reaction 2. Chlorates are determined together with the active chlorine by boiling with ferrous-sulphate solution, and titrating back with permanganate solution, the active chlorine being then deducted from the total. The bases are determined by the action of neutral hydrogen peroxide upon the active chlorine, as in the following reaction : NaOCl + H 2 2 = NaCl + H 2 + 2 . The caustic alkali as well as the carbonate is then titrated in the usual way with hydrochloric acid and phenolphtalein followed by methyl- orange (see page 63). Chlorinated Lime. The ready decomposability of this substance must be taken into account when taking the sample and preparing it for analysis, hence the opera- tions are to be rapidly conducted and the substance exposed as little as possible to the air. Chlorinated lime is examined only as to its content of active chlorine, the result being expressed either in per cents, by weight, or (as in France) in Gay-Lussac 70 TECHNO-CHEMWAL ANALYSIS. degrees, i.e., the number of liters of chlorine gas at C. and 760 mm. that are evolved from one kilo of chlorinated lime. One weigh t-per cent, of chlorine is equivalent to 3.15 degrees Gay-Lussac; or, 100 G.-L. are equivalent to 31.78 per cent, of chlorine. Of the many chlorimetric methods that of Penot is the simplest and at the same time the most accurate. It is based upon the oxidation of sodium arsenite to arsenate by the chlorinated lime, and the recognition of the end of the reaction by the aid of potassium- iodide-starch paper, as follows: Weigh off 7.091 grm. of the chlorinated lime to be examined, triturate it in a porcelain mortar with a little water to form a thin cream, dilute with more water, and wash the whole into a liter flask, which is then filled to the mark. For every test 50 cc. of the freshly shaken mixture, corre- sponding to 0.3545 grm. chlorinated lime, is taken, and into it is run from a burette 1/10-normal arsenite solu- tion (prepared by prolonged boiling of 4.95 grm. pure arsenous acid with 10 grm. sodium bicarbonate and 200 cc. water, filtering, and making up to one liter). When the saturation-point is reached, place a drop of the liquid on potassium-iodide-starch paper; a blue color will develop so long as any chlorinated lime is still present. The non-formation of a color is an evidence of the end of the reaction. Every cubic centimeter of the arsenic solution is equivalent to 1 per cent, of active chlorine. INORGANIC CHEMICAL MANUFACTURES. 71 POTASSIUM SALTS. The raw material for the manufacture of these is chiefly the Stassfurter potassium chloride, which occurs as Carnallit, Kainit, etc. . In examining the chloride, dis- solve 100 grm. in sufficient water to make one liter, and in the clear liquid determine the sulphuric acid gravi- metrically with barium chloride. To determine the potassium, precipitate the sulphuric acid in 100 cc. of the liquid by adding just sufficient barium chloride, whereby all the alkalies are converted into chlorides, then evapo- rate one-tenth of the nitrate (equivalent to 1 grm. of substance) to dryness, decompose the MgC0 2 by ignit- ing with oxalic acid, convert the CaO into CaC0 3 by means of ammonium carbonate, separate the alkali chlorides from the earth-alkalies by dissolving, filter- ing, and again evaporating, weigh the purified KC1+ NaCl, and determine the potassium with platinic chlo- ride; the NaCl is found from the difference. The potassium determination is effected with a pla- tinic-chloride solution, 1 cc. of which contains 1 grm. of platinum. Add sufficient of this solution to the solution of the potassium salt (which must be in the form of chloride and as pure as possible), evaporate in a porcelain dish to a syrupy consistency on the water- bath, stir the residue with 20 cc. strong alcohol, and decant the solution through a filter previously dried at 120-130 C. and weighed; repeat the stirring with alcohol and decantation two or three times, wash the precipitate onto the filter, and press it between filter- 72 TECHNO-CHEMICAL ANALYSIS. paper, then dry at 120-130 C., and weigh the potas- sium-platinic chloride, of which 1 part is equivalent to 0.3056 part KC1 or 0.1928 part K 2 0. Commercial potassium chloride is similarly examined, and so are also potassium salts with high sulphuric-acid content (manurial salts) ; in this case, however, the pre- cipitation of the sulphuric acid in the boiling, strong hydrochloric-acid solution must be effected by adding the barium-chloride solution drop by drop, and in such a manner that there should be present a small remainder of sulphuric acid rather than an excess of barium chlo- ride. The perchlorate process is also frequently employed; in it the sulphuric acid may be much more easily re- moved, as the presence of an excess of barium chloride is not material. Evaporate the filtrate from the barium sulphate on the water-bath with 1J times the quantity of perchloric acid necessary to decompose all the salts, and until the odor of hydrochloric acid has entirely disappeared, allow to cool, and wash the residue with 96-per-cent alcohol to which 0.2 per cent, of perchloric acid has been added. Then bring the precipitate onto a filter as in the platinum method, and weigh as in that method (page 71). Potash. In the manufacture of potash by the Leblanc process practically the same methods are employed as are detailed on page 62 et seq. ; and likewise in the po- tassa lyes obtained electrolytically, as on page 68 et seq. In the commercial products from potash and caustic- potassa lye, the potassa content must be determined as INORGANIC CHEMICAL MANUFACTURES. 73 well as the alkalinity. This is effected just as in the case of potassium chloride (page 71), by saturating with hydrochloric acid, precipitating the sulphuric acid with barium chloride, and treating the chlorides formed with platinum chloride. In vinasse-potash there must also be determined the phosphoric acid by precipitating the nitric-acid solution with ammonium molybdate, dissolving the precipitate in ammonia, and precipitating with magnesia mixture in the usual way. Potassium Cyanide. The cyanogen is determined by dissolving 0.5 grm. of the substance in 100 cc. water, adding 5 cc. normal soda lye and 0.5 grm. sodium bi- carbonate, and titrating with 1/10-normal silver solu- tion so long as the resulting precipitate continues to dissolve. As soon as opalescence persists the reaction is at an end. One cubic centimeter of the silver solu- tion corresponds to 0.01302 grm. KCN. If it is desired to determine the sodium salt which is frequently present in large quantity in commercial products, add 5 cc. of diluted hydrochloric acid to 0.5 grm. of the substance, cautiously evaporate on the water-bath (because of the vapors of hydrocyanic acid evolved), weigh the chlorides as such, and in them determine the KC1 as on page 71; the NaCl is then found from the difference. Potassium- or Sodium-ferrocyanide is examined by acidulating the solution with sulphuric acid and titrat- ing with potassium-permanganate solution until per- manent redness. For every part of iron, as indi- 74 TECHNO-CHEMICAL ANALYSIS. cated by the permanganate, calculate 7.543 parts K 4 Fe(NC) 6 . CLAY AND CEMENT INDUSTRY. In the wider sense we include under this category the investigation of the clays used in pottery, as well as that of marls and cements. Clay used in the Manufacture of Bricks and Cera- mics. This is examined for (a) sandy constituents (which render the (clay poor), and 6) for carbonates of calcium and magnesium. The former are determined, not by chemical methods, but by elutriating a finely triturated portion of the sample with water, whereby the clay itself is retained in suspension, while the quartz sand, the breccia, calcium carbonate, etc., rap- idly subside. The carbonates, however, are deter- mined just as in the case of limestone (page 67). By "rational " analysis is understood the separation of the aluminium silicate from the quartz sand and felspathic residues, etc., by chemical methods, and which is accomplished more or less completely by treatment with concentrated sulphuric acid, or by boiling with solutions of alkali carbonates. In the case of refractory materials the clay must be examined as to its fusibility, by what is called the pyrometric test. Samples of the substance are pre- pared, and are heated in a suitable oven, in which at the same time various normal clays are also placed. For the latter purpose Seger fusible cones are usu- ally employed; these are made of various degrees of INORGANIC CHEMICAL MANUFACTURES. 75 fusibility, and are variously numbered, the num- bers indicating the temperature at which the samples just begin to soften or fuse. Clay and marl for the manufacture of cement are, in important cases, fully examined by quantitative analytical methods. For the ordinary manufactur- ing control it is usually sufficient to determine the carbonic acid, by means of the calcimeter described on page 29, or more accurately by aid of the apparatus shown on page 66, calculating the carbonic acid as CaC0 3 (44 parts C0 2 =100 parts CaC0 3 ), the residue being regarded as "clay." The cements are examined, if at all, by the accurate methods of gravimetric analysis. More important, however, is their testing by a number of mechanical and other practical methods, the description of which can not here be gone into. Regarding these see Chem.- Techn. Untersuchungsmethoden, I, p. 645 et seq. Aluminium Preparations. The most important of these is the aluminium sulphate. This is examined in the main as follows: 1. The alumina, content is determined gravimetri- cally by precipitating with a slight excess of ammonia and boiling for a short time; or volume trically by adding sodium acetate and acetic acid, followed by an excess of sodium-phosphate solution, the phosphoric acid content of which has previously been ascertained by titrating with uranium solution (see below under analysis of manures), whereby all the alumina is pre- cipitated as phosphate, and then titrating back the 76 TECHNO-CHEMICAL ANALYSIS. phosphate not used up by employing the same uranium solution. 2. Iron should be present only in small traces when the preparation is intended for use in the dyeing indus- try. These traces can not be determined by the usual methods, but they can be estimated colorimetrically. For this purpose a solution is prepared by dissolving 8.606 grm. ferric alum in 1 liter of distilled water and diluting this solution one-hundredfold, so that the liter will contain 0.01 grm. iron, and will serve for making comparisons. The concentrated solution remains in good condition for a very long time if 5 grm. concentrated sulphuric acid be added, and the solution is kept away from the light; the diluted solution keeps only a few days. Now dissolve 1 to 2 grm. of aluminium sulphate in a small quantity of water, heat with 1 cc. of iron-free nitric acid, cool, dilute to 50 cc. in a glass cylinder provided with a glass stopper, add 5 cc. of a 10-per-cent. solution of potassium sulphocyanate, followed by 10 cc. of pure ether, stopper the cylinder, and shake thoroughly, whereby the ether acquires a red color. In quite the same manner treat the solution which is to serve for the comparison, and which is prepared by diluting a few cubic centimeters of iron solution of known strength to 50 cc., adding 5 cc. of sulphocyanate solution and 10 cc. of ether, and shaking. By comparing the colors on a white background and against the sky, it is easy to determine from the depth of the color which of the solutions used for ths comparisons corresponds to INORGANIC CHEMICAL MANUFACTURES. 77 aluminium-sulphate solution, and to thus ascertain the iron content of the latter. The comparison is best made after the lapse of an hour, because the color gradu- ally becomes deeper. 3. Free Acid. Dissolve 1 to 2 grm. of the aluminium sulphate in 5 cc. of water, add 5 cc. of a cold saturated solution of ammonium sulphate, stir for 15 minutes, and add 50 cc. of 95-per-cent. alcohol, by which treatment the aluminium sulphate is precipitated as ammonium alum, while the free acid remains in solution. Then filter, wash the contents of the filter with 50 cc. alcohol, evaporate the alcohol on the water-bath, dilute the residue with water, and titrate with 1/10-normal lye and phenolphtalein. ARTIFICIAL MANURES. To these belong particularly the superphosphates, to which are also usually added ammonium chloride, and also Chile saltpeter and even potassium salts. The superphosphates are chiefly examined for the following : i. Phosphoric Acid. To determine the water-soluble phosphoric acid, shake 20 grm. with 800 grm. of water, and make up to 1 liter. In the case of citrate-soluble phosphoric acid (in Thomas phosphate), shake 5 grm. in a half -liter flask with a 2-per-cent. citric-acid solution for half an hour in an agitation apparatus. For the total phosphoric acid, shake 10 grm. of the substance with 25 cc. of water or with 5-per-cent. sulphuric acid, boil with 50 cc, of concentrated sulphuric aci4 78 TECHNO-CHEM1CAL ANALYSIS. and 20 cc. hydrochloric acid, with frequent shaking, for one hour; on cooling, dilute to 500 cc., and filter. At times the citrate-soluble phosphoric acid is also determined as follows: Boil 5 grm. of the super- phosphate with 150 cc. of a solution of ammonium citrate containing 5 per cent, of 10-per-cent. ammonia for one hour at a temperature of 40 C., and then dilute to 250 cc. The solution, made as here detailed, is then examined by volumetric methods where rapid, but not very accurate, analyses are required; for more accurate purposes, the methods of gravimetric analysis are employed. The volumetric analysis is effected by adding 50 cc. of a solution of ammonium acetate (containing 100 grm. of ammonium acetate and 100 grm. concentrated acetic acid per liter) to 200 cc. of the solution made as above (containing 20 grm. per liter), whereby the iron and alumina are precipitated as phosphates (and of which half the weight may be calculated as P 2 5 ), then filter- ing, and titrating 50 cc. of the filtrate (representing 40 cc. of the original solution) with a standardized uranium- acetate solution, while boiling, until a drop placed on a porcelain plate gives a brown ring on contact with a drop of potassium-ferrocyanide solution. The ura- nium solution is prepared from 1 part of uranium nitrate, 28.2 parts of water, and 0.1 part of ammonium acetate, the solution being standardized against calcium phos- phate so that 1 cc. of it will indicate 0.005 grm. P 2 5 . This method is now employed usually only in the case of phosphates free from iron and alumina. INORGANIC CHEMICAL MANUFACTURES 79 The gravimetric analysis is effected by adding concen- trated (75-per-cerit.) ammonium-nitrate solution, and a solution of 150 grm. of ammonium molybdate in 1 liter of water plus 1 liter of nitric acid of sp. gr. 1.2. The total liquid should contain not less than 15 per cent, of ammonium nitrate, and not less than 50 cc. of molyb- denum solution for each 0.1 grm. of P 2 5 . Heat for 10 minutes to 80 to 90 C., allow to cool, filter, and wash with a solution of 150 grm. of ammonium nitrate and 10 cc. of nitric acid per liter. Now perforate the point of the filter, and wash the contents into a beaker with a 2^-per-cent. ammonia (using 75 cc. altogether for the purpose), add for each 0.1 grm. P20 5 drop by drop 10 cc. of magnesia mixture (55 grm. crys- tallized MgCl 2 and 70 grm. NH 4 C1 per liter of 2^-per^ cent, ammonia), allow to stand for two hours, filter, wash with 2^-per-cent. ammonia, dry, burn the filter separately, and then ignite the whole in a platinum crucible, finally with the blast. The magnesium pyro- phosphate thus found, multiplied by 0.6396, gives the P 2 5 . 2. Nitrogen. (a) Nitric-acid nitrogen is determined by Ulsch's, Lunge's, or Schlosing-Grandeau's method, as detailed on pp. 56 and 57. (b) Ammonia-nitrogen. Distil a sample (25 cc. of a solution of 20 grm. of the substance dissolved in 1 liter of distilled water, and diluted to 150 cc.) with 3 grm. of calcined magnesia in a flask provided with a tube for carrying off the gas, and a condenser, until 100 cc. of distillate are collected; the distillate is collected in 80 TECHNO-CHEM1CAL ANALYSIS. standardized acid and titrated back with soda-lye. Or, the azotometer described on page 27 may be employed. (c) Total Nitrogen (including of course organic nitro- gen). The best method for this is that of Kjeldahl and Jodlbauer. One grm. of the substance is placed in a Bohemian-glass flask of 350 cc. capacity, and to it are added, gradually and with constant shaking and cool- ing, 30 cc. of phenol-sulphuric acid, made by dissolving 200 grm. of phosphoric anhydride in 500 cc. of concen- trated sulphuric acid and mixing this with a solution of 40 grm. of phenol in 500 cc. of concentrated sulphuric acid. After one hour add, very gradually and with con- stant and vigorous shaking, 2 to 3 grm. of dry zinc-dust and 1 grm. mercury, heat cautiously to boiling after having allowed the mixture to stand for an hour or two, then boil vigorously until the liquid has become clear and colorless (which may require from ^ to 3 hours), allow to cool, wash with 200 cc. of water into a 500-cc. distillation flask provided with a bulb top (page 56) to prevent any liquid being spirted over, add 110 cc. of nitrogen-free soda lye of sp. gr. 1.285, and also 1 to 1.5 grm. zinc-dust, and distil off the nitrogen that is evolved. This is collected in a receiver containing 20 cc. of normal acid and connected with a three-bulb tube (Peligot or Will-Varrentrapp), and titrated back with soda lye and methyl orange. A small condenser is interposed be- tween the flask and the receiver. 3. Chlorates and Perchlorates are considered as in- jurious, and are determined, usually together, as on, page 57, INORGANIC CHEMICAL MANUFACTURES. 81 4. Potassium is determined as on page 71. 5. Ferric oxide and Alumina must be determined in the crude phosphates, and likewise in the superphos- phates, in order to be able to judge of the " re version" of the phosphate to the insoluble form. Glaser's method serves as a standard for this purpose; it is as follows: Dissolve 5 grm. of the phosphate in 25 cc. of nitric acid of sp. gr. 1.2 and 12.5 cc. of hydrochloric acid of sp. gr. 1.12, make up to 500 cc., add 25 cc. of concentrated sul- phuric acid to 100 cc. of the filtrate, shake for five min- utes, add 100 cc. of 95-per-cent. alcohol, cool, add alcohol to make 250 cc., shake again, filter after half an hour, evaporate 100 cc. of the filtrate until the alcohol has been driven off, then add 50 cc. water, boil, add am- monia until the reaction is alkaline, boil off the excess of ammonia, allow to cool, and filter off the precipitate of ferrous and aluminium phosphates, which then wash with warm water and ignite. Half of the weight is assumed to be Fe20a +A1 2 03. If it is desired to determine the individual contents of iron and alumina, estimate the iron in a separately made hydrochloric-acid solution, after reducing with zinc and adding manganese sulphate, by titrating with potassium permanganate. The alumina is found from the difference. 6. Lime is chiefly determined in Thomas phosphates, and in fact by precipitating a concentrated hydrochloric- acid solution with ammonia and neutral ammonium oxalate; the precipitate is washed with water, dissolved in a little hydrochloric acid, and precipitated by thq 82 TECHNO-CHEMICAL ANALYSIS. addition of a mixture of 10 cc. sulphuric acid (1 : 3) and 150 cc. of 96-per-cent. alcohol; the calcium sulphate is washed with alcohol and weighed as CaS0 4 . GAS AND AMMONIA MANUFACTURE. Illuminating-gas. The technical investigation of this gas is effected by the methods already described on page 7 et seq. The more accurate investigation must be accomplished by means of apparatus in which mercury is used as the confining liquid, e.g., the Dreh- schmidt apparatus, the description of which would be out of place here. It is proper, however, to here call attention to certain useful or injurious constituents of illuminating-gas, which are present in very small quan- tities, and which must hence be determined by special methods. a. Eihylene and benzol are most simply determined, according to Haber, by absorbing both the gases by standardized bromine-water in a Bunte burette (page 9), and measuring the reduction in volume. A stand- ardized iodine solution is then allowed to enter the tube, whereby a quantity of iodine equivalent to the excess of bromine present is liberated, this being then volumetrically determined by thiosulphate solution^ and the ethylene calculated according to the formula: 1 cc. decinormal iodine solution is equivalent to 1.1195 cc. C 2 H 4 at 0C. and 760 mm. The benzol is found from the difference. b. Carbonic acid is determined by passing a measured volume of the gas through a baryta solution of known INORGANIC CHEMICAL MANUFACTURES. 83 strength, and titrating back with oxalic-acid solution; or by means of the Rudorff apparatus, which con- sists of a three-necked flask of about 1 liter capacity, in one neck of which a burette is ground to fit accu- rately; from this burette potassa lye is allowed to flow so long as it is saturated by the carbonic acid; the volume of potassa lye used up is read off on the burette, and corresponds to the C0 2 . A manometer inserted in another neck serves to keep the pressure before and after the operation uniform. c. Hydrogen sulphide is determined in a Bunte bu- rette by means of an iodine solution containing 1.134 grm. I per liter; 1 cc. of this solution indicates 0.1 cc. of H 2 S. The solution is allowed to rise hi the burette, while being shaken, until a slight excess is present, which is recognized by the yellow color the liquid assumes (due to the milkiness caused by the precipitated sulphur). As the confining water has previously been drawn down to the lower mark (10), the volume of the iodine solution used up may be directly read off on the burette, and from it the volume of H 2 S calculated. In accurate determinations, however, the gas in the burette, the volume of which was originally 100 cc., must, after noting the temperature and pressure, be reduced to C. and 760 mm. and dryness. d. The total sulphur is determined in the Dreh- schmidt apparatus. A volume of gas accurately meas- ured by passing through a gas-meter is burned by the aid of a current of air which has been purified by pass- age through pumice-stone impregnated with potassa 84 TECHNO-CHEMICAL ANALYSIS. lye, the burning being done in a Bunsen burner above which a glass cylinder is fixed. The combustion prod- ucts are drawn by the aid of a water-pump through three absorption-flasks containing potassium-carbonate solution and a little bromine-water, and the sulphuric acid formed is determined with barium chloride. e. Ammonia is determined as in Reich's method (page 23), by drawing the gas by means of an aspira- tor or gas-meter through a standardized sulphuric acid tinted with an indicator, until the change of color shows that the acid has been saturated. The acid corresponds to its equivalent of ammonia, e.g., 1 cc. of decinormal acid corresponds to 0.0017 grm. NH 3 . /. The candle-power is ascertained by physical means, using a photometer, regarding the details of which see Chem.-Techn. Untersuchungsmethoden, II, p. 634; and also respecting the specific gravity, II, p. 649. As to the determination of the heat values, see above, page 38. Gas-purifying Compound. It is important to exam- ine the compound used, for the following particularly : a. Sulphur. Extract the compound in a Soxhlet apparatus with pure carbon disulphide, distil off the solvent, and weigh the residual sulphur. This is, of course, still impure, containing some tar; the latter may be removed by washing with a little ether, or else by oxidizing the sulphur to sulphuric acid by means of nitric acid, either alone or with the addition of some potassium chlorate, and then determining the sul- phuric acid formed by the gravimetric method. b. Cyanogen Compounds. According to Drehschmidt, INORGANIC CHEMICAL MANUFACTURES. 85 introduce 10 grm. of the compound into a half-liter flask, add 150 grm. of water, 1 grm. ammonium sulphate, and 15 grm. mercuric oxide, boil for 15 minutes, add J to 1 cc. of a saturated solution of mercurous nitrate and ammonia until a precipitate no longer forms, then fill up to the mark, and add a further 8 cc. of water, corresponding to the volume of the solid sub- stance. Pass through a dry filter, and to 200 cc. of the filtrate (=4 grm. of substance) add 6 cc. of ammonia of sp. gr. 0.91, and 7 grm. of zinc-dust with 2 cc. of potassa lye (30-per cent.), make up to 400 cc., and pass through a dry filter. One hundred cc. of the filtrate are then mixed with 30 to 35 cc. of decinormal silver solution and acidulated with diluted nitric acid in order to precipitate all the cyanogen as silver cyanide. Now make up with water to 400 cc., and titrate back 200 cc. of the clear liquid by Volhard's method with ammonium sulphocyanate in order to ascertain the unused excess of silver solution. Every cubic centi- meter of the decinormal silver solution used up corre- sponds to 0.002598 grm. of cyanogen, or to 0.004771 grm. Prussian blue. c. Ammonia is determined by leaching with water, distilling the solution with caustic lye or magnesia, and collecting the distillate in standardized acid, as on page 80. Gas Liquor. For the factory control this is frequently examined only with the areometer, the indications of which, in this case, however, are very uncertain be- cause of the varying composition of the solutions. 86 TECHNO-CHEMICAL ANALYSIS. The examination should therefore always be made by the following chemical methods: a. Free ammonia, and ammonia combined with weak acids (CO 2 , HS 2 ). This is also designated as "volatile " ammonia, because it may be driven off from the gas liquor by simple distillation, and without any addition of alkali. It may be titrated directly with normal acid and methyl orange, when 1 cc. of normal acid indicates 0.017 grm. NH 3 . b. The total ammonia is best determined by distilling with caustic soda or magnesia, and collecting the dis- tillate in standardized acid, as detailed on page 80. Ammonia Liquor is examined as to its content of NH 3 usually only by taking the specific gravity, for which purpose the folio whig table, calculated for 15 C., serves: Specific Grav- Per Cent. Specific Grav- Per Cent. Specific Grav- Per Cent. Specific Grav- Per Cent. ity. NH 3 . ity. NH 3 ity. NH 3 . ity. NH 3 . 0.998 0.45 0.966 8.33 0.934 17.42 0.902 27.65 0.994 1.37 0.962 9.35 0.930 18.64 0.898 29.01 0.990 2.31 0.958 10.47 0.926 19.87 0.894 30.37 0.986 3.30 0.954 11.60 0.922 21.12 0.890 31.75 0.982 4.30 0.950 12.74 0.918 22.39 0.888 32.50 0.978 5.30 0.946 13.88 0.914 23.68 0.886 33.25 0.974 6.30 0.942 15.04 0.910 24.99 0.884 34.10 0.970 7.31 0.938 16.22 0.906 26.31 0.882 34.95 The ammonia which is sold as "pure " is usually qualitatively examined for iron, copper, lime, chlorides, and also empyreumatic constituents (pyridine bases), for the last usually by immersing a piece of filter-paper in the liquid, and, after the ammonia has evaporated "*?>> INORGANIC CHEMICAL MANUFACTUWS from it, observing the tarry odor which then venes ; or by observing the odor which likewise develops after neutralizing with sulphuric acid. Ammonium Sulphate is examined by distillation with caustic lye (page 85), or by the azotometer (page 27). ADDENDUM. Calcium Carbide. As in sampling this it is very diffi- cult to obtain a uniform sample, it is necessary to take at least 50 grm., or better yet, 100 grm., for analysis. Ordinarily only the yield of gas is determined, although the gas is not pure acetylene. The volume of gas may be ascertained by direct measurement, for which purpose Lunge and others have devised appa- ratus (see Chem.-Techn. Untersuchungsmethoden, II, page 700), or it may be determined indirectly, although less accurately, by the loss in weight of an apparatus arranged so as to deliver water from a funnel provided with a stopcock, the cock being opened and the water allowed to fall on the carbide, the evolved gas being dried by calcium chloride. 0.4062 grm. loss in weight corresponds to 1 grm. CaC 2 , and each per cent, of CaC 2 is equivalent to 34.89 liters of C 2 H 2 at C. and 760 mm. COAL-TAR INDUSTRY. Coal-tar itself is examined only as to its specific gravity. Before ascertaining this, however, it is necessary to free the tar from water by allowing it to stand for twenty-four hours in a narrow-necked bottle standing in water at 50 C., and then removing the 88 TECHNO-CHEMICAL ANALYSIS. water, which separates by pouring off and absorbing with blotting-paper. The tar is then allowed to cool to 15 C. An araeometer or picnometer can not be used to take the specific gravity of the viscid tar. It is best to employ a cylindrical weighing-tube of 50 cc. capacity, with a longitudinal groove filed in its glass stopper. The specific gravity is determined: (a) by first weighing the dry tube, then (6) weighing it filled with water, then, after drying the tube again, filling it two-thirds full with tar, placing it for an hour in hot water until all the air-bubbles have been expelled, allow- ing to cool, and then weighing back (c). Now fill up with water, insert the stopper, remove the water which is expelled from the vessel, allow to stand in a large vessel of water at 15 C., and then weigh again (d). The specific gravity sought is calculated from the follow- ing formula: ca b+c-(a+d)' The free carbon is sometimes determined by exhaust- ing 10 grm. of the tar with 25 cc. of glacial acetic acid and 25 grm. toluol, filtering through a weighed filter, washing with toluol, and drying at 120 C. To ascertain the yield of products afforded by tar, large quantities must be submitted to distillation, which is a matter of considerable inconvenience in a technical laboratory. Commercial benzol is a mixture of benzol, toluol, and the higher homologues of these substances. It is first COAL-TAR. 89 examined by fractionally distilling 100 cc. in a frac- tionation-flask provided with a side-tube and a ther- mometer-vessel arranged so as to be surrounded by the vapor, the distillation being so regulated that two drops of liquid pass over per -second. The distillate is col- lected in a graduated cylinder, on which the volume- per cent, may be read off. At certain fixed points, which vary according to the commercial article, the flame is removed, and the distillate present in the con- denser allowed to run for two minutes before reading off. The fixed points, in the case of the light benzols, are 80, 90, 100, and 110 C.; for the heavy benzols they are 110, 120, and 130 C., and higher, according to agreement. In the trade in English benzols the irrational English test is still employed, in which, while all the dimensions of the apparatus are accurately prescribed, the ther- mometer-vessel is not surrounded by vapor, but is im- mersed in and reaches nearly to the bottom of the liquid. Occasionally there are also determined: (a) Non- nitratable constituents, by treatment with a mixture of strong sulphuric and nitric acids, washing, and distil- ling off the non-nitrated substances by passing-in a cur- rent of steam. (6) Carbon disulphidcj by shaking with a few drops of phenylhydrazine, whereby a precipitate of phenyl- hydrazine phenylsulphocarbaminate forms after an hour. (c) Thiophen. On shaking with a solution of sodium 00 TECHNO-CHEMICAL ANALYSIS. nitrate in sulphuric acid, a green color, changing to a blue, develops if thiophen is present. Differentiation of Coal-tar Benzol from Petroleum, Benzin, Brown-coal Oils, etc. This is already quite easily effected by the odor alone; also by means of the specific gravity, which in the case of the coal-tar prod- uct is never below 0.875, while with the others it is rarely above 0.7. Nitrosulphuric acid is capable of nitrating the former, but not the latter. Picric acid colors benzol yellow, but is insoluble in petroleum benzin. Coal-tar pitch, which has first been exhausted with a high-boiling petroleum and then dried, colors benzol a deep yellow, but petroleum benzin scarcely at all, a fact that permits an approximately quantitative valuation of a mixture of the two to be made. Naphtalin is tested as to its melting-point (79 C.) and boiling-point (218 C.). It should have a pure white color, and afford a colorless solution with petro- leum benzin. On being dissolved in pure, concentrated sulphuric acid, it should not impart more than a faint pink color to the acid. A sample placed under a glass bell over pure, concentrated nitric acid should remain colorless for one to two hours. Anthracene is always examined quantitatively as to the quantity of anthraquinone that may be obtained from it. The commercial anthracene is boiled with glacial acetic acid and chromic acid,. the anthraquinone then precipitated with water, thoroughly washed, dried at 100 C., heated with fuming sulphuric acid of 68 Be. to 112 C., diluted with water, the purified CARBOLIC ACID. 91 anthraquinone filtered off, washed, dried at 100 C., and weighed. It is then strongly heated until all the anthraquinone has been driven off, and weighed back. The difference multiplied by 0.8558 gives the actual amount of anthracene in the sample examined. In order, however, to obtain correct results, it is necessary to observe certain definite rules in carrying out the process (comp. Chem.-Techn. Untersuchungsmetho- den, II, p. 740). Carbolic Acid. The technical, solid carbolic acid is occasionally pure, or almost pure, phenol, but it fre- quently contains higher homologues (cresols); where a considerable quantity of these are present, it is liquid. Perfectly pure phenol melts at 42 C., while technically pure carbolic acid melts at 35 to 38 C., and dissolves in 20 paTts of water. The phenol content is occasion- ally determined gravimetrically by precipitating the phenol as tribromphenol, but more generally indi- rectly by volumetric methods, by the action of bro- minized soda solution of known effective value on the phenol, and then titrating back the excess of unused bromine. For this purpose there is used a mixture of 5NaBr+ NaBrOa, obtained by dissolving an excess of bromine in caustic lye, evaporating to dryness, dis- solving about 9 grm. of the residue in 100 cc. of water, and then adding concentrated hydrochloric acid and potassium iodide to the solution; the iodine that has separated out is then titrated back with thiosulphate. If, now, a phenol solution is treated with bromine solu- tion and hydrochloric acid, followed by potassium 92 TECHNO-CHEMICAL ANALYSIS. iodide, the slightest liberation of iodine indicates the presence of phenol. Crude Carbolic Acid and Carbolic-acid Preparations (creolin, lysol, sapocarbol, etc.). Crude carbolic acid is tested as to its content of phenols of every kind by shaking 1 volume with 9 volumes of caustic lye of sp. gr. 1.079, and determining the volume of undis- solved oils, i.e., non-phenols. The various (saponaceous) carbolic-acid preparations are similarly shaken with caustic-soda lye, the solution freed from hydrocarbons by shaking out with ether, the ether then driven off, the solution neutralized with hydrochloric acid, and the fatty acids precipitated as barium salts by adding barium chloride and baryta- water. The acids may be liberated from the precipi- tate by hydrochloric acid, and then determined. The solution freed from the fatty acids is acidulated, and the cresols shaken out with ether and weighed. Coal-tar pitch is examined as to its softening- and melting-points, but often only by the mastication test. Soft pitch may be easily pressed out flat; medium- hard pitch will only receive the pressure of the teeth; while hard pitch crumbles between the teeth and falls to powder. For more accurate examination the apparatus of Kraemer and Sarnow is employed. Twenty-five grammes of the pitch are melted in an iron pan in an oil-bath at 150 C.; the pitch should form a layer of about 10 mm. in the pan. Into it one end of a glass tube of 5 to 7 mm. internal diameter, and open at both ends, MINERAL OILS. 93 is dipped, the upper end closed with the finger, the tube removed, and the pitch allowed to solidify, after which that adhering to the glass removed. There remains a column of about 5 mm. in height in the tube. Now pour about 5 grm. of mercury into the tube, and hang the latter beside a thermometer in a beaker that serves as a water-bath, and which is contained within a simi- lar exterior water-bath. Heat gradually until the mercury penetrates the pitch, and note the tempera- ture; this will be the softening-point of the pitch. In the case of soft pitch this point will lie between 50 and 51 G.; for medium-hard, between 60 and 70 C,; and for hard pitch, between 80 and 89 C. MINERAL OILS. Petroleum. In order to determine the value of petroleum, the latter must be investigated as fully as possible as to various constituents obtainable from it, and best -by the fractional distillation of as conveniently large a quantity as possible, duplicating the manu- facturing operations on a small scale. We will here consider only the investigation of the commercial prod- ucts obtained from petroleum. Benzin is the name applied to the portion of crude petroleum boiling below 150 C. Of this, the specific gravity is always determined, and almost always by means of the areometer. Furthermore, it is subjected to a fractional distillation. For this purpose the cus- toms-office employs apparatus made entirely of metal, and of certain dimensions. The chemist generally 94 TECHNO-CHEMICAL ANALYSIS makes use of the Engler apparatus (fig. 15) , the dimensions of which are here accurately given. In- stead of using the copper side-tube, the vertical cooler, and the glass burette, it is better to conduct the distillation at a temperature below 200 C., employing FIG. 15 an ordinary Liebig condenser, just as in the case of benzol, page 88. Kerosene is similarly examined as to its specific grav- ity, and also ,by the distillation test; the greater part should distill over between 150 and 300 C. In addition, the clearness and color must be observed, and above all the flash-point, which is determined for the pur- pose of ascertaining the inflammability. For this pur- pose there is generally used the Abel petroleum tester, consisting of a metallic water-bath in which is suspended MINERAL OILS. 95 a smaller metallic vessel for the reception of the petro- leum. The inner vessel is closed by a cover which carries a thermometer dipping into the kerosene, and an ignition apparatus operated by a small train of gear-wheels. The ignition apparatus consists of a small slide connected with a small lamp which is brought into contact with the mixture of air and kerosene vapor in the upper part of the vessel when the slide is moved. The temperature at which the gaseous mixture ignites is noted, and corrected for the barometric pressure by aid of a table which accom- panies the apparatus. At times the sulphur content is determined, and just in the same manner as in the case of illuminating-gas (page 83 et seq.)', the candle-power is also determined by photometric methods. Lubricating-oils are chiefly examined as to their vis- cosity by means of the Engler viscosometer (fig. 16). The principle upon which this apparatus is based is the meas- urement of the rapidity of flow of the liquid under cer- tain definite conditions. The vessel A holds about 240 cc. of oil when filled up to the mark. The outflow-tube through which the liquid flows, a, is 20 mm. long and 2.8 mm. , , . FIG. 16. in diameter; before being filled it is closed by a wooden rod, 6. The mantle, B ; 96 TECHNO-CHEMICAL ANALYSIS. serves as a water- or oil-bath, and is heated by the ring- burner, d. The measuring-flask C bears two marks, one indicating 200 cc. and the other 240 cc. For the degree of fluidity there is taken the quotient obtained by divid- ing the time of outflow of 200 cc. of the oil (at the ex- perimental temperature) by the time of outflow of 200 cc. of water at 20 C. With the apparatus at normal conditions, the time required for water will be from 52 to 54 seconds, but for oils it will naturally be more. The temperature of the oil must be regulated accord- ing to the requirements of the case, and must always be stated in giving the results. For machine and gear- wheel oils the temperature must be maintained at 20 to 50 C.; for cylinder-oils, at 50, 100, or 180 C., and at times even much higher. There are also often de- termined the solidify ing-point, the rate of flow, and par- ticularly the flash-point, for which Pensky and Martin have constructed a special apparatus, differing only from that of Abel (page 94) by the addition of a stir- ring arrangement. An important test is that for the determination of the content of acid, which in the case of dark mineral oils may amount to 0.3 per cent, and even 0.5 per cent, (calculated as S0 3 ). It is calculated as S0 3 , although it consists chiefly of phenols and resin acids. It is determined by dissolving 10 cc. of the oil in 150 cc. of a mixture of 4 parts of alcohol and 1 part of ether, and then titrating with decinormal alcoholic soda lye and phenolphtalein. In the case of light-colored oils this may be done directly; dark oils, however, must OILS AND FATS. 97 first be shaken with double the volume of absolute alcohol, allowed to stand for several hours, and the titration effected with 20 cc. of the alcohol as above. In addition, the power of attacking metals may be tested by prolonged warming with polished metals; the surfaces of these should not be affected. In the case of bearing metals, a heat of 50 C. suffices; in the case of steam-cylinder oils, these must be heated in autoclaves at the temperature to which the oils will be subjected in practice. An attack on the metal here takes place almost always only in the case of an admix- ture of fatty oils, the presence of which may be directly detected by the formation of a soap on heating for 15 minutes with caustic soda in a paraffin-bath at a tem- perature of 230 to 250 C. OILS AND FATS. It is but seldom that fatty oils or solid fats can be decomposed into their individual constituents. By means of a number of reactions it is possible to quan- titatively ascertain, however, how many of the indi- vidual groups of glycerides are present, and to thereby quite easily characterize the fats and oils. The results are expressed in the form of numbers, which are some- times also designated by the names of the chemists who first advanced their use. These reactions are as follows : * 1. The Hehner number indicates the percentage of * For further particulars see Chem.-Techn, Untersuchungs- jnethoden, III, p. 88 et sey. 98 TECHNO-CHEMICAL ANALYSIS. water-insoluble fatty acids present (those soluble in water are the lower volatile fatty acids only). Saponify 3 to 5 grm. of the fat with alcoholic alkali, precipitate the fat acids with a strong acid, collect them on a filter, wash with water, and weigh. 2. The acid number indicates the number of milli- grammes of KOH required to saturate the free fatty acids in 1 grm. of the substance, and it is ascertained by titrating with seminormal lye and phenolphtalein. The number of cubic centimeters used up multiplied by 28 (one -half the molecular weight of KOH) gives the acid number. 3. The saponification number (Kottsorfer) denotes the number of milligrammes of KOH required to fully saponify 1 grm. of the fat; alcoholic lye is used for this purpose, the excess being titrated back with seminormal hydrochloric acid and phenolphtalein. The operation may be conducted with the aid of heat/ by boiling for half an hour under a reflux condenser, or hi the cold by dissolving in petroleum ether (accord- ing to Henriques). 4. The Hubl iodine number affords an insight as to the content of unsaturated acids; it indicates the number of grammes of iodine that are capable of combining with 100 grammes of fat. For this there is employed an alco- holic, approximately 1/5-normal, solution of iodine and mercuric chloride ; an excess of the solution is allowed to act upon the fat dissolved in chloroform, potassium iodide then added, and the excess of iodine then titrated back with sodium thiosulphate, OILS AND FATS. 99 5. The acetyl number gives the quantity of oxy- acids present which are acetylated by treatment with acetic anhydride. This method is rather difficult to carry out, and even then does not give certain re- sults. 6. The Reichert-Meissl number refers to the content of volatile acids, and denotes the number of cubic centi- meters of decinormal alkali-lye required to neutralize the acids volatilized by steam and soluble in water, and which are obtained by saponifying 5 grm. of the fat. In addition there are determined the specific gravity, melting-point, solidifying-point, and refractive index, the latter being ascertained by means of the Zeiss refrac-. tometer, the use of which is made obligatory for butter; the odor and taste are also noted. The presence of certain oils may be qualitatively determined by reactions, e.g., sesame oil by the rose- red color afforded by an alcoholic solution of furfurol (Baudouin's reaction) ; cottonseed-oil by the reduction of silver nitrate (Bechi's reaction); or the orange-red color afforded by a mixture of amylic alcohol and car- bon disulphide (Halphen's reaction). Of the foreign constituents, the water is determined by drying at 100 C. ; the inorganic constituents by incin- eration; the organic non-fatty substances (dirt of all kinds) by dissolving in ether and filtering; free mineral acids by boiling with water and titrating the solution with decinormal soda lye and methyl orange; soaps (in solid fats) by incinerating, and titrating the alkaline 100 TECHNO-CHEMICAL ANALYSIS. ash; non-saponifiable oils by boiling with an alcoholic alkali solution and then diluting with water. An admixture of resin is recognized by the compara- tively high acid number, by the solubility in 70-per- cent, alcohol, and also by shaking with acetic anhydride, when, on the addition of a drop of sulphuric acid (sp. gr. 1.53), a reddish-violet color develops (Storch- Morawski reaction). SOAPS. In taking the sample, due regard must be paid to the fact that the surface of the soap rapidly dries, and that hence the external layer must be removed; and in the case of soft soaps, all those parts that have been ex- posed to the air. The following determinations are then made : a. Water. Weigh off 5 to 10 grm. of the sample in a small dish, heat for two hours in a drying-closet at 60-70 C., then for half an hour at 105-110 C., and weigh. b. Inorganic Fillers. Boil 30 grm. of the sample with absolute alcohol, which will leave behind all the salts of the mineral acids (with C0 2 , Si0 2 , B 2 3 , S0 3 , Cl); then filter, wash with alcohol, and weigh after drying. The mixture of salts may then be investigated for its individual constituents by the usual methods. c. Total Fat and Total Alkali. These may be deter- mined in one operation, by decomposing a weighed sample with normal acid, and adding a solvent for the SOAPS. 101 fats; the uncombined acid in the aqueous solution is then determined by titrating back, while the fatty acids are estimated by evaporating an aliquot portion of the fat-acids solution. For this purpose Huggen- berg has constructed a peculiarly shaped burette, which admirably accomplishes its purpose. But even with- out this apparatus excellent results may be obtained as follows: Heat 5 to 10 grm. with diluted hydrochloric or sulphuric acid until the separated fatty acids float as a clear, oily layer, then add 5 to 10 grm. of remelted wax or hard paraffin, with which the fatty acids form a difficultly fusible mass, and allow to cool. The acid liquid is poured off, the fat-cake remelted once or twice with water, then removed, the adhering water allowed to drain off, and the cake then placed in an exsiccator for several hours before weighing. It is convenient to weigh a piece of filter-paper together with the wax, so that it may be used for wiping the vessels, removing fat adhering to the glass rods, etc. The fatty acids obtained by one method or another were of course not naturally present in the soap as such, but (in a dualistic sense) in the form of anhy- drides combined with N 2 or K 2 0; hence the water of hydration corresponding to their mean molecular weight must be deducted, and this is generally assumed to be equal to 3.25 per cent, of their weight. The total alkali may be more rapidly determined by itself by decomposing about 2 grm. of the soap with a measured volume of normal acid with the aid of heat, allowing to cool, adding methyl orange, and titrating 102 TECHNO-CHEMICAL ANALYSIS. back with normal soda lye without separating the fatty acids. The free alkali present (i.e., the carbonate and hydrate) is most simply determined by boiling 20 to 50 grm. of the soap with about 100 cc. of a neutral, saturated solution of sodium chloride, filtering, and titrating the solution with methyl orange and 1/5-normal acid. Glycerin is found in large quantity only in toilet soaps. The method of determining it is given here, because it must be examined by itself as an individual commercial article, and the glycerin yield of raw fats in the manufacture of stearin must also be determined. The determination is effected either by oxidation with potassium-permanganate solution in alkaline solution, precipitating the oxalic acid formed as a lime salt, and titrating the latter, or by oxidation with normal potas- sium-dichromate solution, with the addition of an excess of ferrous-sulphate solution of known effective value, and then titrating with dichromate solution. Pure glycerin should be colorless, almost free from ash, of sweet taste and odor, and have a specific grav- ity of 1.26. SUGAR. Sugar-beets. As good an average sample as possi- ble is taken, and reduced without loss of juice to a homogeneous pulp (for which purpose quite a number of various apparatus have been devised); in this the sugar content is determined, usually by polariza- tion. SUGAR. 103 For this purpose the Soleil-Ventzke-Scheibler polar- izer, improved by Schmidt and Haensch, is used. The scale of the apparatus is so arranged that when 26.048 grm. of sugar are dissolved in enough water to make 100 cc., and the solution examined in a 200-mm. tube at a temperature of 17.5 C., the plane of polarization will be turned 100, and hence every degree will indi- cate 0.26048 grm. of sugar in 100 cc. of solution. Hence if 26.048 grm. of any sugar or saccharine substance be weighed off and dissolved to make 100 cc. of solution, and the latter observed through a 200-mm. tube at 17.5 C. ; the deviation will give, without further cal- culation, the percentage content of sugar by a simple reading of the scale. It is absolutely essential to accurately control the temperature. The beet pulp is next subjected to alcohol extraction in a Soxhlet apparatus. To 26.048 grm. of the beet pulp, 3 cc. of lead-subacetate solution are added, and the mixture extracted with 75 cc. of 90-per-cent. alco- hol until exhausted, which will usually require at most two hours. If it is desired to make quite certain that the exhaustion is complete, the residue is again ex- tracted for half an hour in another apparatus. The alcoholic extract is then made up to 100 cc. and polar- ized as detailed above. The various other methods of digestion are less trustworthy. Furthermore, the s'olid constituents of the beets (the "marc") insoluble in water are also determined by leaching with water and drying the residue at 110 C., best in a vacuum drying-closet. 104 TECHNO-CHEMICAL ANALYSIS. The polarization does not give directly the content of cane-sugar, because there are also other optically active substances present, chiefly invert-sugar, of which 1 part gives the optical rotation afforded by 0.34 parts of cane-sugar. The invert-sugar is determined by its property of precipitating copper in the form of red Cu 2 from a boiling alkaline copper solution. To pre- pare the copper solution (Fehling's solution), dissolve (according to Soxhlet's formula) 34.639 grm. of chem- ically pure copper sulphate in enough distilled water to make 500 cc.; on the other hand, dissolve 173 grm. of the purest Rochelle salt in somewhat less than 400 cc. of water, add 100 cc. of a solution of 516 grm. of the purest NaOH in 1 liter of water, and make up to 500 cc. Both solutions, which must be perfectly clear, must be kept separately, and equal volumes of the two mixed just before use. The mixture remains in a serviceable condition but for a few days. It is em- ployed either gravimetrically or volumetrically. In the former, the method of procedure, where at most 1 per cent, of invert-sugar is present besides the cane-sugar, is as follows: In the case of rather pure products 20 grm. are dissolved to make 100 cc. of solution, the liquid filtered, and 50 cc. taken for the determination. In the case of more impure products, 25 grm. are dissolved with a little lead-subacetate solution to make 100 cc., the lead removed from 60 cc. of filtrate by means of sodium bicarbonate, the solution made up to 75 cc., and 50 cc. (=10 grm. of substance) of the filtrate taken for analysis. The sample is mixed SUGAR. 105 in a 300-cc. Erlenmeyer flask with 50 cc. of freshly prepared Fehling's solution, the mixture heated as rapidly as possible to boiling, and maintained at this point for two minutes, and then immediately diluted with 100 cc. of cold, air-free distilled water, and filtered by means of an air-pump through a previously weighed Soxhlet asbestos filter. The latter is a glass cylinder 2 cm. wide and 12 to 14 cm. long, constricted at one end to form a cone. The conical end bears a platinum cone, above which is placed a 2-cm. layer of purest asbestos. After filtering as above detailed, wash the residue with 300 to 400 cc. of boiling water, then with 20 cc. of abso- lute alcohol, dry at 130 to 200 C., heat to faint red- ness, and reduce to metallic copper by prolonged heating, finally igniting gently in a current of hydro- gen. (A table for the calculation of the percentage content of invert-sugar will be found in Chem.-Techn. Untersuchungsmethoden, III, 'p. 285.) When higher percentages of invert-sugar are present smaller quantities of the substance are weighed off, and the procedure then carried out as above. The calcula- tion made by aid of the polarizing apparatus is rather complicated in this case, hence it is better to determine the total sugar by inversion, and then to deduct the invert sugar found directly as above, in order to obtain the pure saccharose (cane-sugar). To effect inversion, i.e., conversion of the saccharose into sugars having the composition of dextrose (invert- sugar), heat 13.024 grm. of sugar with 75 cc. water and 5 cc. concentrated hydrochloric acid in a water- 106 TECHNO-CHEMICAL ANALYSIS. bath to 67 C., maintain at this temperature for five minutes, then cool immediately, and make up to 100 cc., and then dilute 50 cc. with water to make 1 liter; of this solution take 25 cc. ( =0.1628 grm. substance), neutralize the free acid by gradually adding 25 cc. of a solution of 1.7 grm. Na 2 C0 3 in 1 liter of water, then add 50 cc. Fehling's solution, heat to boiling, boil for 2 minutes, and convert the Cu 2 into Cu as detailed on pages 104 and 105. Every 100 mgm. of Cu will correspond to 30.93 per cent, of total sugar, calculated as cane-sugar. Fehling's solution may also be utilized for the volu- metric determination of invert-sugar. Saccharine juices are first tested as to their specific gravities, then measured in a Balling-Brix saccharom- eter, the degrees of which in the case of solutions of pure sugar give directly the percentage of sugar, but in the case of the impure factory products they give only the total (apparently) dry substance. A direct determination of the sugar content is effected by polar- izing as on page 103, after adding lead-subacetate solu- tion to clarify the solution and remove the non-sugars. There are also determined the water content, by evapo- rating with quartz sand at 105 to 110C.; the ash content; the content of invert-sugar (usually by titra- tion with Fehling's solution); the alkalinity, by titrating with very dilute normal acid and phenol- phtalein; and the lime content by precipitating with ammonium oxalate. The other factory products, as well as molasses, are examined in a similar manner. ALCOHOL. 107 For the examination of sugar itself (cane-sugar and refined sugar), dissolve 26.048 grm. in water to make 100 cc., clarify by adding lead-subacetate solution or (in the case of pure sugar) aluminium-hydrate cream, and polarize as on page -103. In addition all the other factors may be determined, as in the case of beet- juices. ALCOHOL MANUFACTURE (BRANDY, ETC.). Raw Materials. In amylaceous substances the starch is determined by converting it into dextrose by means of hydrochloric acid, the " inversion" being accom- plished by first gelatinizing 3 grm. of starch with 200 cc. water and then heating on a water-bath for two hours with 15 cc. hydrochloric acid of sp. gr. 1.125, loss of vapor during heating being avoided by fixing a rather long tube on the flask. The mixture is then neutralized almost completely with soda lye, made up to 500 cc., and the dextrose determined as on page 104. Nine parts of starch correspond to ten parts of dextrose, and the results are calculated accordingly. With substances containing cellulose, the inversion by acids gives too high results in cases where the high- pressure method is not employed, which method also partially converts these substances into fermentible bodies. In such cases the inversion is effected by means of malt extract, the reducing power of which has been previously determined by a separate test, and due allowance made for it. Qn the % other hand ? in the analysis by the high- 108 TECHNO-CHEMICAL ANALYSIS. pressure method, the inversion is effected under pres- sure, for which purpose the Lintner pressure-flask is employed, the stopper of which is held fast by a wire frame and screws. The determination of starch in potatoes is accom- plished with sufficient accuracy for ordinary practical work (with an error of +1 per cent.) by determining the specific gravity with a balance specially adapted for the purpose, the determination being based upon the fact that the specific gravity of starch is very high; and the dry substance of potatoes consists chiefly of starch. A table for this is given in Chem.-Techn. Untersuchungsmethoden, III, p. 371. Saccharine raw materials, such as molasses, etc., are examined by polarization (page 103), or by a direct fermentation test; e.g., by diluting 50 grm. of the molasses with 200 grm. water, adding 10 cc. concentrated sulphuric acid and a little yeast, allowing to ferment, and then distilling off 100 cc. In the distillate the alcohol is determined, and if necessary the volatile acids also. Malt is chiefly examined as to its saccharifying power, in addition to its external characteristics. 6 grm. of crushed malt are digested with 100 cc. water for one hour on a water-bath at 60 C., and the mixture then cooled and filtered. This malt extract is mixed with soluble starch. 2 grm. of Effront's or Lintner's soluble starch are dissolved in 100 cc. boiling water, 50 cc. of the solution diluted with 107.5 cc. water, and 2.5 cc, of the malt extract added, Saccharification is. ALCOHOL. then effected by heating for one hour on a wat1*rg$ A ^/ at 60 C., the mixture then heated rapidly to boiling, and cooled. The solution is then tested for its sugar content by means of Fehling's solution, and usually volumetrically. The liquefying power of malt is furthermore ascer- tained by warming with triturated rice starch at 80 C. The smaller the quantity of malt extract required for the purpose, the higher is its liquefying power. The acid content too, which by careless treatment may be considerably augmented, is determined by means of phenolphtalein in an extract obtained by digestion with chloroform water (distilled water shaken with chloro- form and then poured off from the latter). Sweet mash is examined as to the extent of the saccharization it has undergone, directly by means of the saccharometer (page 106), and indirectly by ex- tracting with cold water and determining the starch in the insoluble residue, as on page 107. Fermented mash is examined, after filtration, as to the extent it has fermented, by means of the saccharom- eter, which, however, gives only the apparent fermenta- tion, as the increase in the specific gravity of the liquid due to the sugar is to some extent counterbalanced by the decrease caused by the alcohol formed. The actual content of soluble matter is ascertained by taking note of the alcohol content. If S be the specific gravity of the mash considered as free from alcohol, S A that of the alcoholic mash, and s that of a mixture of alcohol and water of the same alcoholic strength as that of the mash, 110 TECHNO-CHEMICAL ANALYSIS. then S=S 1 +(1 s). From S the sugar still present is then found by means of the tables. Maltose is determined by polarization in the solution clarified by treatment with lead subacetate and freed from lead with sulphuric acid (page 103) The total car- bohydrates are determined, after inversion with hydro- chloric acid, by means of Fehling's solution (page 104), and then the dextrin content by deducting the maltose from the total. Alcohol is determined by distilling the mash-filtrate and taking the specific gravity as detailed below. Alcoholometry. In alcohol and similar relatively pure mixtures of alcohol and water, the alcohol is ascer- tained by the specific gravity, which is taken with an araeometer (alcoholometer), picnometer, or a hydro- static balance. Absolutely pure alcohol, at a tem- perature of 15 C., has a specific gravity of 0.79425. The alcoholometer officially used in Germany gives directly the percentage by weight, and must hence be employed either at the temperature of 15 C., or the proper correction must be made for other tempera- tures by means of tables issued by the Normal-Standard Commission. Frequently, however, the statements are also made in volume-percents, for which either a special alcoholom- eter, or reduction tables, must be employed. (Com- pare " Anleitung zur steueramtlichen Ermittelung des Alcohols im Branntwein, " Berlin, Julius Springer.) Alcohol is now usually bought and sold by liter- per cent., of which each represents 10 cc. of absolute ALCOHOL. Ill alcohol. Ten thousand liter-percent, is equivalent to 1 hectoliter absolute alcohol. Specific Gravity. Grammes Alcohol in 100 cc. Volume Per Cent. Specific Gravity. Grammes Alcohol in 100 cc. Volume Per Cent. 1.000 0.00 0.00 0.980 12.81 16.14 0.999 0.53 0.67 0.979 13.60 17.14 0.998 1.06 1.34 0.978 14.39 18.14 0.997 1.60 2.02 0.977 15.19 19.14 0.996 2.16 2.72 0.976 15.99 20.15 0.995 2.72 3.42 0.975 16.79 21.16 0.994 3.29 4.14 0.974 17.58 22.16 0.993 3.87 4.88 0.973 18.37 23.14 0.992 4.47 5.63 0.972 19.14 24.12 0.991 5.08 6.40 0.971 19.91 25.08 0.990 5.70 7.18 0.970 20.66 26.03 0.989 6.34 7.99 0.969 21.40 26.96 0.988 6.99 8.81 0.968 22.12 27.87 0.987 7.66 9.66 0.967 22.82 28.76 0.986 8.35 10.52 0.966 23.52 29.64 0.985 9.06 11.41 0.965 24.19 30.49 0.984 9.78 12.32 0.964 24.85 31.32 0.983 10.52 13.25 0.963 25.50 32.14 0.982 11.27 14.20 0.962 26.13 32.93 0.981 12.03 15.16 The above table gives the percentage of alcohol by weight and volume at 15 C. at various specific gravities.* Fusel-oil is determined by Rose's method and other modifications by shaking-out with chloroform, which dissolves the higher-boiling homologues of ethyl alcohol much more readily than it does alcohol, and thereby increases in volume. The apparatus in which the shaking is done is a glass tube expanded at both ends, * A complete table by K. Windisch has been published by Julius Springer, under the title " Tafel fur Ermittelung des Alcoholgehaltes von Alcohol- Wassermisehungen nach dem specifischen Gewicht." 112 TECHNO-CHEMICAL ANALYSIS. the lower end terminating in a closed half-bulb, and the upper closed by a cork stopper. The lower por- tion of the tube holds 200 cc. up to the narrowed part. The middle, cylindrical part holds 20 to 26 cc. and is divided into 1/20 cc. The upper part is pear-shaped, and holds from 150 to 180 cc. The brandy to be tested is distilled with the addition of a little soda lye. The distillate is carefully examined in a picnometer for its specific gravity, and diluted to an alcohol content of 24.7 per cent, by weight, equivalent to 30 per cent, by volume. By means of a funnel reaching to the bottom of the shaking-out apparatus, which has been brought to 15 C., 20 cc. of chloroform are introduced, and by means of a fine pipette, brought exactly to the mark. There are then added 100 cc. of the alcohol which has been reduced in strength to 30 volume-percent, and brought to 15 C., together with 5 cc. of sulphuric acid of sp. gr. 1.286; the apparatus is now stoppered, vigorously shaken 150 times, again cooled in a water-bath to 15 C., and the level of the chloroform in the narrow portion of the tube noted ( = a) . Chloroform takes up a little alcohol, even when the latter is perfectly pure, hence the quantity taken up must be determined for each lot of chloroform. The level of the chloroform after such a control test we will designate as b. According as a b is greater or less than 0.9 cc., the brandy contains more or less than 2 per cent, fusel-oil in every 2 parts by weight of anhy- drous alcohol. The figure representing the percentage by weight of fusel-oil up to 5 per cent, is obtained by multiplying a b by 2.22. In the case of brandies very VINEGAR. 113 poor in fusel-oil, special apparatus with finer gradua- tions is employed. Furfurol is detected in 10 cc. of the distillate by add- ing 10 drops of colorless aniline and 2 cc. acetic acid; in twenty to thirty minutes. a rose-red color develops. Of the denaturing substances, pyridine is detected by cadmium chloride, which gives with it a white, crystal- line precipitate. If an acid has been added to the brandy for the purpose of removing the pyridine odor ? the cadmium-chloride reaction does not occur, but it develops immediately on shaking with magnesia. Ace- tone is indicated by the formation of iodoform on adding ammonia and a solution of iodine in ammonium-iodide solution. The differentiation of the various grades of brandy from each other is far easier of accomplishment by means of the odor and taste than by chemical investi- gation. VINEGAR. The total acid is determined by titration with nor- mal alkali, using phenolphtalein as indicator; in highly colored vinegar the "spot" method is employed, using good litmus paper. Free mineral acids are detected by diluting the vinegar to a 2-per-cent. strength and adding a few drops of a 1/100-per-cent. solution of methyl violet, which, in the presence of a considerable quantity of mineral acid, imparts a green color, and with very small quantities of mineral acids, a blue color, to the 114 TECHNO-CHEMICAL ANALYSIS. liquid. Sulphuric acid particularly is detected by evaporating a small quantity of the vinegar with a little starch to one-fifth of its volume and adding iodine solution; if free sulphuric acid is absent the starch will be colored blue, but if the starch has been converted into sugar by inversion with sulphuric acid, no blue color will develop. Or, a little of the vinegar is evaporated to dryness on the water-bath with a little sugar, whereby a black ring will form, due to the carbonization of the sugar by the sulphuric acid. Hydrochloric acid or nitric acid is detected by distilling, and testing the distillate in the usual manner. Tar- taric acid is detected by evaporating, taking up the residue with alcohol, and adding potassium chloride, when a precipitate of potass' um bitartrate forms. Oxalic acid is recognized by the precipitate afforded by calcium-sulphate solution. If foreign acids are present, or if the vinegar is highly colored, the acetic acid is determined directly by neu- tralization with alkali, supersaturation with phosphoric acid, then distilling in a water-bath by the aid of a current of steam, and finally titrating the distillate. Poisonous metals are detected and determined by the methods employed in mineral analysis. Wood-vinegar contains chiefly empyreumatic con- stituents, which are detected by the decolorization of a decinormal potassium-permanganate solution. Nor does it contain the micro-organisms which occur in fermen- tation vinegar, and which may be microscopically detected in the. latter. WlXE. 115 WINE.* Of the methods for examining wines, officially pub- lished by the Chancellor of the Empire, and based on the Food Laws of 1896, only the more important will be given here. The specific gravity is determined with a picnometer, and the alcohol by distilling, and testing the distillate according to the table given on page 111; the content of extract "E" is ascertained according to the table on page 118, after determining the density "x" by means of the formula z = l + S S^ where S is the specific gravity of the distillate, and S x that of the residue which has remained after the distillation and which has been made up to the original volume. The mineral constituents are determined by incineration; the sulphuric acid (in red wine) is determined by precipitation with barium chloride ; the total acid by hot titration with a not less than one-fourth normal lye, employing the " spot " method with violet litmus paper (the results being cal- culated as potassium bitartrate); the volatile acids are estimated by distilling in a current of steam; glycerin is determined by evaporating with quartz-sand and milk-of-lime to dryness, extracting the residue with 96-per cent, alcohol, shaking out with ether, and evap- orating the ethereal solution; sugar is determined with * Compare K. Windisch, " Die chemische Untersuchung und Beur- teilung des Weines," Berlin, 1896, and Th. W. Fresenius, " Anleitung zur chemischen Untersuchung des Weines," Wiesbaden, 1898. 116 TECHNO-CHEMICAL ANALYSIS. Fehling's solution (page 104), or by clarifying with lead subacetate and then polarizing (page 103); impure starch-sugar is estimated by comparing the results obtained by both these methods, as the impurities polarize differently than does pure sugar; foreign dyes are detected by various methods which can not be given here; potassium bitartrate and tartaric acid are deter- mined together by converting the latter into potassium bitartrate and precipitating the total bitartrate with calcium chloride; sulphurous acid is determined by dis- tilling with the addition of phosphoric acid, collecting the distillate in iodine solution, and precipitating the sulphuric acid formed with barium chloride; tannin is determined by the usual methods (page 119 et seq.). BEER BREWING. Hops are usually examined chemically only as to the water content and sulphurization, the former by drying for four hours at 100 C. To find whether the hops have been sulphurized, extract 10 grm. of the hops with 200 cc. distilled water, and introduce 50 cc. of the filtrate together with 1.5 grm. sulphur-free zinc and 25 cc. pure hydrochloric acid of sp. gr. 1.125 into a flask, which is then covered with moist lead-acetate paper; if the latter is blackened within half an hour by the H 2 S, it indicates that S0 2 had been present. Barley too must be occasionally examined as to whether it has been sulphurized. In malts it is chiefly necessary to determine the extract, which is done by heating 50 grm. of the malt BEER BREWING. H7 with 200 cc. of water for half an hour at 35 C., then for twenty-five minutes at 70 C., and then digesting for an hour longer with constant stirring; frequent tests are then made with iodine as to the extent of saccharifi- cation, and, when an iodine reaction is no longer ob- tained, the mixture is cooled by at once adding 200 cc. of cold water, the temperature rapidly reduced to 15 C., and the weight made up on the balance to 450 grm. The specific gravity of the filtrate is taken at 15 C., and from this the extract content is ascertained by ref- erence to Windisch's table (page 118). The wort is examined as on page 109, but in addition, as to its color, by colorimetric comparisons with normal type solutions prepared from iodine, or better, from artificial dyes. Beer is examined as to its specific gravity; its alcohol content A, by distillation, as detailed on page 110; its extract content E, in the residue from the latter, as described on page 115; degree of fermentation V, by comparing that of the stock wort, e, ascertained from the alcohol content A according to the for- 100(E + 2.0665A) mula in n i i HAA^A with that of the extract content 1UU ~r 1 . E, according to the proportion e : e E :: 100 : V; whence V = l(X)(l V The value of V will lie be- tween 50 and 60 per cent., and is legally fixed in vari- ous countries. There may furthermore be determined, among other substances, the following: Sugar, as in wine, on pages 115 and 116; nitrogenous constituents, ac- TECHNO-CHEMICAL ANALYSIS. cording to KjeldahPs method (page 80) ; acids, by titra- tion with phenolphtalein and decinormal lye; carbonic acid, by moderately heating, at first in a vacuum, then in a current of air, drying the gas, and collecting in potash bulbs; glycerin, as detailed on page 102; sulphurous EXTRACT TABLE.* x = Density at 15 C. ; E = Per cent, of extract. X E X E X E X E .000 0.00 1.029 7.50 1.058 15.03 1.087 22.62 .001 0.26 .030 7.76 1.059 15.29 1.088 22.88 .002 0.52 .031 8.02 1.060 15.55 1.089 23.14 .003 0.77 .032 8.27 1.061 15.81 1.090 23.41 .004 1.03 .033 8.53 1.062 16.07 1.091 23.67 .005 1.29 .034 8.79 1.063 16.33 1.092 23.93 .006 1-55 .035 9.05 1.064 16.60 1.093 24.20 .007 1.81 .036 9.31 1.065 16.86 1.094 24.46 .008 2.07 .037 9.57 1.066 17.12 1.095 24.72 .009 2.32 1.038 9.83 1.067 17.38 1.096 24.99 .010 2.58 1.039 10.09 1.068 17.64 1.097 25.25 .011 2.84 1.040 10.35 1.069 17.90 1.098 25.51 .012 3.10 1.041 10.61 1.070 18.16 1.099 25.78 .013 3.36 1.042 10.87 1.071 18.43 1.100 26.04 .014 3.62 .043 11.13 1.072 18.69 1.101 26.30 .015 3.87 .044 11.39 1.073 18.95 1.102 26.56 .016 4.13 .045 11.65 1.074 19.21 1.103 26.83 .017 4.39 .046 11.91 1.075 19.47 1.104 27.09 .018 4.65 .047 12.17 1.076 19.73 1.105 27.35 .019 4.91 .048 12.43 1.077 20.00 1.106 27.62 .020 5.17 .049 12.69 1.078 20.26 1.107 27.88 .021 5.43 .050 12.95 1.079 20.52 1.108 28.15 .022 5.69 .051 13.21 1.080 20.78 1.109 28.41 .023 5.94 .052 13.47 1.081 21.04 1.110 28.67 .024 6.20 .053 13.73 1.082 21.31 .111 28.94 .025 6.46 .054 13.99 1.083 21.57 .112 29.20 .026 6.72 .055 14.25 1.084 21.83 .113 29.47 .027 6.98 1.056 14.51 1.085 22.09 .114 29.73 .028 7.24 1.057 14.77 1.086 22.36 .115 29.99 * This table is a short abstract of that published by K. Windisch under the title Tafel zur Ermittelung des zuckergehaltes wassriger Zuckerlosungen aus der Dichte bei 15 C., Berlin, Jul. Springer, 1896. TANNING MATERIALS. acid, by distilling with phosphoric acid, collect! (distillate in iodine solution, and determining the sul- phuric acid formed; and boric acid, by carbonizing the beer, to which a little alkali has been added, and testing the acidulated ash-extract with curcuma-paper, etc. TANNING MATERIALS. The taking of the sample of these substances pre- sents some difficulty; it is best accomplished, as well as the analysis, according to the conclusions arrived at by the international conference of leather chemists, which will be found in the Chem.-Techn. Untersuch- ungsmethoden, III, p. 574 et seq. From the prepared sample the tannin is extracted, and the solution made of such strength that 100 cc. will yield from 0.6 to 0.8 grm. residue. For this purpose weigh off, according to the nature of the material, from 12 to 50 grm. of the raw tanning material, and treat in a suitable extraction apparatus (for which purpose a number have been devised of various construction) with water, first at 50 C., and then at 100 C., until 500 cc. of extract are obtained, which is then diluted to 1 liter. In the case of extracts, dissolve 9 to 20 grm. in boiling water, rapidly cool to 15 to 20 C., make up to 1 liter, and filter. In this extract there are determined: 1. The total soluble matter by evaporating 100 cc. and drying at 100 to 105 C., and best by drying at 100 C. in a vacuum to constant weight; and 120 TECHNO-CHEMICAL ANALYSIS. 2. The non-tannins, by removing the tannin with hide powder, and again evaporating the filtrate. The commercial hide powder must first be well washed, and then introduced into a Procter filter. The latter consists of a bottomless flask of about 30 cc. capacity, the open bottom being closed by a piece of muslin; in the neck is fastened a siphon, formed from a glass tube bent twice at right angles and having a diameter of 2 mm. This filter holcls about 7 grm. of hide powder, and is placed in a beaker of 150 to 200 cc. capacity, in which 100 cc. of the tannin solution are poured, where- upon the siphon is set in operation by applying suction. The filtration requires from 1J to 2 hours for comple- tion. The first 30 cc. are rejected, and the non-tannins determined in the next 50 cc. of liquid. Instead of effecting the determination gravimetrically, it is more usual to employ the volumetric method de- vised by von Schroeder and improved by Lowenthal, the titration being effected with potassium-perman- ganate solution as follows: a. Dissolve 2 grm. of pure commercial tannin in 1 liter of water, and to 10 cc. of the solution add 20 cc. of an indigo solution prepared by dissolving 30 grm. sodium indigosulphonate in 6 liters of 10-per-cent. sulphuric acid and filtering; the 20 cc. should reduce about 10.7 cc. of the permanganate solution, and this must be ascertained by a test. Into the tannin-indigo mixture now run from a burette permanganate solution (10 grm. purest KMn0 4 dissolved in 6 liters of water). 1 cc. of the permanganate solution is added at a time, the DYEING. 121 liquid being vigorously stirred for 5 to 10 seconds after each addition. When the liquid acquires a light-green color the permanganate is added by drops only, stir- ring after each addition, and ceasing when the liquid appears golden-yellow. It is inadmissible to titrate back. 6. A second titration is now made after 50 cc. of the tannin solution have been digested with 3 grm. of hide powder for 18 to 20 hours. If the quantity of permanganate solution used up in 6 is not more than 10 per cent, above what was used in the first titration, a, then the tannin is suitable for preparing the standard solution. The tannin is then dried at 100 C., the per- manganate solution used up in a calculated for the dried tannin, and the result multiplied by 1.05, which will give the "'true titer." In making the determination of tanning materials in the extracts prepared as above (page 119), the procedure is exactly the same as in fixing the titer in the case of pure tannin, and the result is calculated on this. DYEING.* Textile Fibers. The microscope is indispensable for the examination and differentiation of these. There are, however, a number of chemical reactions also, that may be employed for their differentiation. The most important are the following: * Compare R. Gnehm, Taschenbuch fur Farberei und Farben- fabrikation, Berlin, 1902. 122 TECHNO-CHEMICAL ANALYSIS. Fuchsine solution and the acid tar dyes, particularly picric acid, color animal fibers (wool and silk), but not linen or cotton. Concentrated zinc-chloride solution (sp. gr. 1.7) easily dissolves silk, wool only partially, and plant fibers not at all. Ammoniacal copper solu- tion dissolves only plant fibers, whereas ammoniacal nickel solution dissolves silk only. Potassa or soda, lye dissolves only wool and silk. Iodine and sulphuric acid color only plant fibers (with swelling of the latter) linen and cotton blue, and hemp and jute greenish to brown. Sugar and sulphuric acid color only animal fibers a rose-red (furfurol reaction). Wood fiber in hemp, jute, etc., is detected by the yellow color afforded with aniline sulphate, by the orange color developed by naphtylamine hydrochlorate, and by the rose-red 'color produced with indol and sulphuric acid. Artificial silk (made from nitrocellulose or by dis- solving cotton treated with soda in ammoniacal copper solution) is differentiated from natural silk by its slight content of nitrogen (less than 1 per cent.), by its insolubility in a solution of 10 grm. copper sulphate and 5 grm. glycerin in 100 cc. water, to which just suffi- cient soda-lye has been added to dissolve the precip- itate it causes, and also by its rapid and complete com- bustion when brought into contact with a flame. Coloring-matter. The testing for and differentiation of the individual dyes, of which many hundreds are used in practice, can not here be described; we can only restrict our observations to general remarks, and for the rest refer to Gnehm's "Taschenbuch " and his DYEING. 123 treatise in Vol. Ill of Chem.-Techn. Untersuchungs- methoden. Inorganic dyes are examined by chemical methods, and by practical comparisons with a sample of known properties, the "'type " or standard. Both are trit- urated with linseed-oil, with the addition of white lead or zinc white, and compared on a marble slab ; in the case of dyes for printing fabrics, comparisons between the "type '' and sample are made on cotton. Organic dyes are always examined by means of test dyes. First, however, it is necessary to gain some idea as to which one of the four following groups the dye in question belongs: 1. Direct-dyeing cotton dyes are fixed on the fiber by boiling a small piece of cotton rag or a skein with the addition of a little soap, soda, or sodium phosphate, and then washing with water. The dyes belonging to the other classes when thus treated impart no, or almost no, color to the fiber. 2. Basic dyes are but seldom fixed on wool, but silk is frequently dyed with them. They dye animal fibers (and wool also) even without a mordant, but cotton only when it is tannated, i.e., when treated with a tanning sub- stance. In testing whether the dye is suitable for use on silk, an examination must be made as to whether it is to be used in a neutral or acid bath, or whether the dyeing is to be effected in pure water or the raw-silk bath, and also as to how it behaves when the color is brightened. 3. Acid dyes do not fix at all, or almost not at all, on cotton, nor on wool in a neutral bath, but do so very 124 TECHNO-CHEMICAL ANALYSIS. well in a warm bath with the addition of sulphuric acid or acid salts, or after the wool has first been treated with sulphuric acid, alum, or potassium bitartrate, after which the dyeing is completed in a boiling, neu- tral bath. Silk is dyed without any such preliminary treatment, and at a low temperature. 4. Mordant-dyes are such as can be fixed on fibers only in the form of their metallic lakes. They may be recognized by the fact that they dye neither wool nor cotton in acid, neutral, or alkaline bath, but do so after the fabric has been mordanted with solutions of alum, etc. In the case of cotton, pieces are used that have been imprinted with various mordants in parallel rows. Both the wool and cotton samples are then dyed with heat, and finally treated with a soap-bath to clear the color. After having ascertained to which one of the classes named the dye belongs, the next step is the Quantitative Test Dyeing. For this purpose there are required, besides graduated pipettes, cylinders, and flasks, also suitable dye-vessels, best beakers of porcelain or of tinned copper, 7.5 cm. in diameter and 14 cm. in height, and several of which may be suspended at one time in a copper water-bath by means of a perforated copper plate which keeps" the beakers a few centimeters from the bottom. The heating is done by gas or with a steam-coil. Where higher temperatures are required, glycerin, oil, or the like, must be used instead of water. For suspending the skeins or trans- ferring them from one dye-bath to another, glass rods are used which are "V or "1 /"-shaped. In carrying DYEING. 125 out the dyeing tests, it is essential that the materials employed, as well as all the operations to be made, approximate as closely as possible to those prevailing in manufacturing on the large scale, but which is not, of course, always strictly- possible. The fabric in this case is also usually to be compared with a "type," and both are to be treated side by side under like condi- tions. It is customary to dye the lighter shades of color, because these are more readily compared, and the dye-bath is then exhausted of its color as com- pletely as possible. As a rule, 1-per-cent. solutions in hot water (more rarely alcohol) of the dye to be tested and the "type," are made, and calculations made as to how many cubic centimeters are required to develop a 1- or 2-, or even higher, per cent, color on a weighed quantity of fiber. For every series of tests, like quantities by weight of skeins or rags are taken. In order to be able to distinguish the various samples, knots are tied in the skeins, and holes cut in the margins of the rags. In order to compare the dye with the "type," like volumes of the solutions of the "type" and sample are used with like quantities of the fiber. After a little practice quite noticeable increases in the intensity of coloration are recognized even before the end of the operation. To the less deeply colored sample a suffi- cient but measured volume of the solution of the dye is added until, at the close of the operation, both fabrics have the same intensity of color. In making the com- parison both skeins must be drawn from the bath at 126 TECHNO-CHEMICAL ANALYSIS. the same time in order that they may be observed at the same degree of moistness; the comparison must be repeated after washing with water and drying, and always by the same light. Usually, "type" samples are dyed of 1, 1J, and 2 per cent, strength, and simultaneously, with samples of the products to be tested, whereby it is generally possible to obtain a sample that will correspond to one of the three strengths mentioned. Should this not happen to be the case, a second, or at worst a third, trial will suffice to afford a correct sample, whereupon a com- parison can be made of the volumes of the dye solu- tions used up. In making the comparison, however, it is necessary not only to take note of the intensity of the color, but of its purity also. If the dye has not been completely used up in the bath, a new dyeing experiment must be made with fresh pieces of fabric, using the partially exhausted dye-bath, and the supplementary samples compared. Fractional dyeing sometimes permits the detection of the presence of several dyes or foreign substances. Silk is generally dyed in the skein after it has been boiled. Frequently, and particularly in the case of acid dyes, a bath acidulated with acetic or sulphuric acid suffices. Often, however, "bast soap" is used, it being first added to the bath, then the necessary quan- tity of sulphuric or acetic acid to "break" the bath, then filling up with water, and finally adding the dye and stirring thoroughly. In the case of basic dyes, a neutral bath, or one to which Marseilles soap has been DYEING. 127 added, is used; for substantive cotton dyes a neutral bath with 5 to 15 per cent, of sodium phosphate and 5 per cent, of soap is employed. The silk is first moistened with lukewarm water, then drawn several times through the cold or lukewarm dye-bath, then removed, the bath next heated, and the dyeing finally completed at the temperature de- sired. The silk is now drawn about several times in another bath of clean, warm water, and the color cleared by placing for ten minutes in water acidulated very weakly with sulphuric or acetic acid. After being repeatedly drawn about in this bath, the fabric is wrung out and dried. Soft water must be used. Wool is taken in the form of zephyr yarn or flannel rags thoroughly freed from fat, and at times also loose, but in this case great care must be exercised in order to avoid felting. The wool is thoroughly moistened, the greater part of the dye fixed on at about 50 C., the heat gradually raised to 90 to 95 C. while con- stantly stirring, the bath then allowed to boil gently for fifteen to thirty minutes (with alizarine dyes, from one to one and one-half hours), allowed to cool, and the fabric then washed and dried. After being washed, the skeins are weighted with sticks and hung up, and turned occasionally during the drying in order to avoid streaking. Acid dyes are used in a bath to which is added from 10 to 15 per cent, sodium bisulphate; the addition of alum or zinc chloride is also often advantageous. In the case of dyes that "take " rapidly, it is best to take 128 TECHNO-CHEMICAL ANALYSIS. at first only 2 to 5 per cent, acetic acid and towards the end 5 per cent, sulphuric acid (previously diluted). Basic dyes are fixed on without any addition whatever; and dyes requiring mordants, after a preliminary boiling with the latter (potassium bichromate, alum, tin salt, ferrous sulphate, etc., with various additions). Cotton is dyed in the form of well-boiled and washed hanks, which, in the case of light colors, must also be bleached. The substantive dyes (benzidine dyes, etc.) are fixed on the fiber with the addition of from 20 to 50 per cent, sodium sulphate or sodium chloride, potas- sium carbonate, sodium (or potassium) silicate, or sodium phosphate. More salt must be added when the dye takes with difficulty than when it takes rapidly. At times a supplementary treatment with copper sul- phate, potassium chromate, and the like, is necessary. Insoluble azo-dyes are fixed on the fabric by " coup- ling." In the case of the basic dyes, the cotton is first mordanted with tannin and tartar emetic. In the case of the true mordant-dyes, e.g., all the alizarine dyes, the cotton is first treated with the proper metallic salt (chromium, alumina, iron), and then oiled with Turkey- red oil (5 to 10 per cent, oil at 30 to 40 C.) ; the dyeing is then carried to completion at 40 to 50 C., and at times even at higher temperatures; then follow boiling in the soap bath and washing. In making tests in fabric printing , a small printing- machine must be employed, and the pieces treated in a manner as nearly as possible like that carried out on the large scale. INDEX. PAGE Abel's flash-point apparatus 94 Absorption-pipette, compound 17 for liquids and solids 17 Acetone, detection of 113 Acetyl number 99 Acid, carbolic, crude 92 examining 91 preparations of 92 carbonic, determining in bicarbonates 62 determining in gases 11 determining in illuminating-gas 82 hydrochloric, determining impurities in 61 determining in vinegar 114 examination of 60, 61 nitric, determining in vinegar 114 examination of 55 number, determining 98 oxalic, determining in vinegar 114 phosphoric, determining in superphosphates 77 sulphuric, determining impurities in 52 determining in mixtures of nitric and sulphuric acids 59 determining in vinegar 114 examination of 49 fuming, examination of 54 Acids, determining in wine 115 mineral, determining in vinegar 113 total, determination in calcination gases 26 determining in vinegar 113 129 130 INDEX. PAGE Alcohol, determining in wine 115 examining 107 Alcoholometry 110 Alkali, total, in soaps, determining 100 Aluminium, preparations, examining 75 sulphate, examining 75 Ammonia, determining in illuminating-gas 84 liquor, examining 86 -soda process, factory control of .' 63 Ammonium sulphate, examining 87 Analysis, techno-chemical, scope of 1 Anthracene, examining 90 Anthracite coal, examination of 38 Arsenic, Marsh's test for 53 Reinsch's test for 54 Asbestos filter, Soxhlet's 105 Azotometer, Knop's 27 Barley, examining 116 Baudouin's test. . 99 Bechi's test 99 Beer, brewing 116 examining 117 Benzin, examining 93 Benzol, determining in illuminating-gas 82 Bicarbonate, examining 66 Bleaching fluids, examining 68 Bomb-calorimeter 37 Brandy, examining 107 Brown coal, examination of 38 Bunte's burette 9 Burette, Bunte's 9 KempeFs 15 Orsat's 12 Winkler's 7 Calcimeter 29 Calcium carbide, examining 87 Calorimeter, bomb- 37 Candle-power of illuminating-gas, determining 84 Carbolic acid, see Acid, carbolic. INDEX. 131 Carbonic acid, see Acid, carbonic. Carbonic oxide, determination of, in gases 11 Carnallit, examining 71 Cements, examining 75 Chancel's sulphurimeter 44 Chili saltpeter, examination of 55 Chlorates, determining in superphosphates SO " Chloride of Lime," see Lime, chlorinated. Chlorimetric method, Penot's '. 70 Chlorine, examining 68 Clay, examining 74, 75 Coloring matter, testing for 122 Coal, anthracite, and brown, examination of 38 Coal-tar, examining 87 pitch, examining 92 Differentiating coal-tar benzol from petroleum, benzin, brown- coal oils, etc. 90 Drehschmidt's platinum capillary 22 Dyeing 121 Dyes, determining in wine V ....... 116 inorganic, examining 123 organic, examining 123 Engler's apparatus for distilling benzin 94 viscosimeter 95 Ethylene, determining in illuminating-gas 82 Extract, determining in wine 115 Fat, total, in soaps, determining 100 Fats, examining 97 Fehling's solution. 104 Fermentation test 108 Fillers, in soaps, determining 100 Filter, Soxhlet's asbestos 105 Flash-point apparatus, Abel's 94 Pensky-Martin's 96 determining 94 Fuels, examination of 37 Furfurol, detection of 113 Fusel-oil, determining Ill Fusible cones, Seger's. 74 132 INDEX. PAGH Gas analysis, technical 7 illuminating-, examining , 82 liquor, examining 85 -purifying compound, examining 84 -sulphur, examination of 45 -volumeter, Lunge's 30, 34 -volumetry 27 Gases, absorbable, determining very small quantities 26 Reich's method of determining 23 collecting 5 determining by combustion 19 Glycerin, examining 102 Halphen's test 99 Hardness of water, determination of 40, 42 Heat-values, determination of f 38 Hehner's number, determining 97 Hempel's burette 15 Hops, examining 116 Hubl's number, determining 98 Hydrochloric acid, see Acid, hydrochloric. Hydrogen, determining in gases. 14 sulphide, determining in illuminating-gas 83 Illuminating-gas, examining. 82 Inversion of sugar 105 Invert-sugar, determining 104 Iron, determining in aluminium colorimetrically 76 determining in superphosphates 81 Kainit, examining 71 Kerosene, examining 94 Knop's azotometer 27 Kottstorfer's number, determining 98 Lime, caustic, examining. 67 chlorinated, examining 69 determining in superphosphates 81 Limestone, examining 67 Lubricating oils, examining 95 INDEX. 133 PAGE Lunge's gas-volumeter 30, 34 method of determining nitrogen 56 nitrometer 30 Lyes, electrolytic, examining 64, 68 for sulphite cellulose, examination of 49 Malt, determining the liquefying power of 109 examining 108, 116 Maltose, determining 110 Manganese dioxide, examining 66 Manures, artificial, examining 77 Marl, examining 75 Marsh's test for arsenic 53 Mash, fermented, examining 109 sweet, examining 109 Methane, determination by combustion 20, 22 Molasses, examining 108 Naphtalin, examining 90 Nitric acid, examination of 55-59 Nitric oxide, determination by combustion 23 Nitrogen, determining in superphosphates 79 nitrate-, Ulsch's method of determining 56 Lunge's method of determining 56 Schlosing-Grandeau- Wagner's method of determining 57 Nitrometer, Lunge's 30 Nitrose, examination of < 48 Nitrous oxide, determination by combustion 23 Oils, determining foreign constituents in 99 examining 97 Orsat's apparatus 12 Palladium-asbestos capillary, Winkler's 21 Penot's chlorimetric method 70 Pensky-Martin's flash-point apparatus 96 Perchlorate, determining in niter 57 Perchlorates, determining in supjrphosphates 80 Petroleum, examining 93 Pipette, absorption-, compound 17 Pipettes, absorption-, for liquids and solids 17 134 INDEX. PAGE Platinum capillary, Drehschmidt's 22 Polarizer, Soleil-Ventzke-Scheibler 103 Polarizing 104 Potash, examining 72 Potassium chloride, examining 71, 72 cyanide, examining 73 determining in superphosphates 81 ferrocyanide, examining 73 salts 71 Pyridine, detection of 113 Pyrites, examination of 45 Pyrometric test 74 Raw material, examination of 1 Reichert-Meissl number 99 Reich's method of determining absorbable gases 23 Reinsch's test for arsenic. . 54 Rock salt, examination of 59 Saccharine juices, examining 106 Salt, examination of 59, 60 Saltpeter, examination of 55 Samples, uniform, preparation of 3 Saponification number 98 Schlosing-Grandeau-Wagner's method of determining nitrogen. 57 Seger's fusible cones 74 Smoke-gases, examination of 39 Soaps, examining 100 Soda-ash, crude, examination of 62 calcined, examination of 64 caustic, examining 65 caustic, factory control of 63 crystal- 65 examination of 62 Sodium ferrocyanide 73 Soxhlet asbestos filter 105 Starch, determining 107 in potatoes, determining 108 inverting 107 Sugar-beets, examining 102 determining in wine 115 INDEX. 135 PAGE Sugar, examining 102 inverting 105 Sulphate, examination of 59, 60 Sulphur, determining in illuminating-gas 83 dioxide, determination in calcination gases 25 examination of . t 44 Sulphuric acid, see Acid, sulphuric. Sulphurimeter, Chancel's 44 Superphosphates, examining.. 77 Table comparing specific gravity, degrees Baume, and percent- age strength of sulphuric acid 50 Table of extract, Windisch's 118 showing specific gravity and percentage strength of hy- drochloric acid 61 showing specific gravity and percentage strength of nitric acid 58 showing specific gravity, and quantity of alcohol in grammes per 100 cc 13 Tanning extracts, examining 119 materials, examining 119 Tartrates, determining in wine 116 Test-dyeing, quantitative 124 Textile fibers, differentiating 121 examining , 121 Ulsch's method of determining nitrate nitrogen 56 Vinasse-potash, examining 73 Vinegar, determining mineral acids in 113 determining total acid in 113 Viscosimeter, Engler's 95 Water, determining alkalinity of 41 determining hardness of 40, 42 technical analysis of 39 Weighing 4 Wine, determining acids in 115 determining alcohol in 115 determining dyes in 116 determining sugar in 115 136 INDEX. PAGE Wine, determining tartrates in 116 examining 115 Winkler's burette 7 palladium-asbestos capillary 21 Wood-vinegar, examining 114 Wort, examining 117 inc blende, examination of 47 SHORT-TITLE CATALOGUE OF THE PUBLICATIONS OP JOHN WILEY & SONS, NEW YORK. LONDON: CHAPMAN & HALL, LIMITED. ARRANGED UNDER SUBJECTS. Descriptive circulars sent on application. Books marked with an asterisk are sold at net prices only, a double asterisk (**) books sold under the rules of the American Publishers' Association at net prices subject to an extra charge for postage. All books are bound in cloth unless otherwise stated. AGRICULTURE. Armsby's Manual of Cattle-feeding i2mo, Si 75 Principles of Animal Nutrition 8vo 4 oo Budd and Hansen's American Horticultural Manual: Part I. Propagation, Culture, and Improvement 12 mo, Part II. 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Higher Structures 8vo, 2 50 Morison's Memphis Bridge 4to> 10 oo Waddell's De Pontibus, a Pocket-book for Bridge Engineers. . . i6mo. morocco> 3 oo Specifications for Steel Bridges lamo, i 25 Wood's Treatise on the Theory of the Construction of Bridges and Roofs. 8vo, 2 oo Wright's Designing of Draw-spans: Part L Plate-girder Draws 8vo 2 50 Part IL Riveted-truss and Pin-connected Long-span Draws 8vo, 2 50 Two parts in one volume 8 yo 3 SO 6 HYDRAULICS. Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from an Orifice. (Trautwine.) 8vo, 2 oo Bovey's Treatise on Hydraulics 8vo, 5 oo Church's Mechanics of Engineering 8vo, 6 oo Diagrams of Mean Velocity of Water in Open Channels paper, i 50 Coffin's Graphical Solution of Hydraulic Problems i6mo, morocco, 2 50 Flather's Dynamometers, and the Measurement of Power ismo, 3 oo Folwell's Water-supply Engineering 8vo, 4 oo Frizell's Water-power.. ... 8vo, 5 oo Fuertes's Water and Public Health lamo, i 50 Water-filtration Works I2mo, 2 50 Ganguillet and Kutter's General Formula for the Uniform Flow of Water in Rivers and Other Channels. (Hering and Trautwine.) 8vo. 4 oo Hazen's Filtration of Public Water-supply 8vo, 3 oo Hazlehurst's Towers and Tanks for Water-works 8vo, 2 50 Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal Conduits 8vo, 2 oo Mason's Water-supply. 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(A Pocket-book for Bridge Engineers.) . . i6mo, mor., 3 oo Specifications for Steel Bridges i2mo, i 25 Wood's (De V.) Treatise on the Resistance of Materials, and an Appendix on the Preservation of Timber 8vo, 2 oo Wood's (De V.) Elements of Analytical Mechanics 8vo, 3 oo Wood's (M. P.) Rustless Coatings : Corrosion and Electrolysis of Iron and Steel 8vo, 4 oo RAILWAY ENGINEERING. 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Vol.1 8vo, 2 50 Schwamb and Merrill's Elements of Mechanism 8vo, 3 oo Sinclair's Locomotive-engine Running and Management Z2mo, 2 oo Smith's Press-working of Metals 8vo, 3 oo Materials of Machines I2mo, i oo Spangler, Greene, and Marshall's Elements of Steam-engineering 8vo, 3 oo Thurston's Treatise on Friction and Lost Work in Machinery and Mill Work 8vo, 3 oo Animal as a Machine and Prime Motor, and the Laws of Energetics . i2mo, i oo Warren's Elements of Machine Construction and Drawing 8vo, 7 50 Weisbach's Kinematics and the Power of Transmission. (Herrmann Klein.) 8vo, 5 oo Machinery of Transmission and Governors. (Herrmann Klein.). 8 vo, 5 oo Wood's Elements of Analytical Mechanics 8vo, 3 oo Principles of Elementary Mechanics I2mo, i 25 Turbines 8vo, 2 50 The World's Columbian Exposition of 1893 - 4to, i oo 14 METALLURGY. Egleston's Metallurgy of Silver, Gold, and Mercury: VoL I. Silver 8vo, 7 So VoL H. Gold and Mercury 8vo, 7 50 ** Iles's Lead-smelting. 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A Study in Dietaries i2mo, i oo Cost of Living as Modified by Sanitary Science i2mo, i oo Richards and Woodman's Air, Water, and Food from a Sanitary Stand- point 8vo, 2 oo * Richards and Williams's The Dietary Computer 8vo, i 50 Rideal's Sewage and Bacterial Purification of Sewage 8vo> 3 50 Turneaure and Russell's Public Water-supplies 8vo, 5 oo Von Behring's Suppression of Tuberculosis. (Bolduan.) i2mo, i oo Whipple's Microscopy of Drinking-water 8vo, 3 50 Woodhull's Notes and Military Hygiene i6mo, i 50 MISCELLANEOUS. Emmons's Geological Guide-book of the Rocky Mountain Excursion of the International Congress of Geologists Large 8vo, i 50 Ferrel's Popular Treatise on the Winds 8vo, 4 oo Haines's American Railway Management i2mo 2 50 Mott's Composition, Digestibility, and Nutritive Value of Food. Mounted chart, i 25 Fallacy of the Present Theory of Sound i6mo, i oo Ricketts's History of Rensselaer Polytechnic Institute, 1824-1894. Small 8vo, 3 oo Rostoski's Serum Diagnosis. (Bolduan.) i2mo, i oo Rotherham's Emphasized New Testament Large 8vo, 2 oo Steel's Treatise on the Diseases of the Dog 8vo, 3 50 Totten's Important Question in Metrology 8vo, 2 50 The World's Columbian Exposition of 1893 4to, i oo Von Behring's Suppression of Tuberculosis. (Bolduan.) i2mo, i oo Worcester and Atkinson. Small Hospitals, Establishment and Maintenance, and Suggestions for Hospital Architecture, with Plans for a Small Hospital i2mo, i 25 HEBREW AND CHALDEE TEXT-BOOKS. Green's Grammar of the Hebrew Language 8vo, 3 oo Elementar.y Hebrew Grammar i2mo. i 25 Hebrew Chrestomathy 8vo, 2 oo Gesenius's Hebrew and Chaldee Lexicon to the Old Testament Scriptures. (Tregelles.) Small 4to, half morocco, 5 oo Letteris?fc Hebrew Bible 8vo, 2 25 16 I M. . OVERDUE. OCT 23 1932 OCT 24 1932 YB 16734 "::;". :-.'.!:;- n ^M^/K'