SELECT METHODS. IN QUANTITATIVE ANALYSIS BYRON W. CHEEVEB, A.M., M. D., Late Acting Professor of Metallurgy in the University of Michigan. Arranged from Prof. Cheever's manuscript by FRANK CLEMES SMITH. PARTS I AND II. SECOND EDITION. ANN ARBOR: REGISTER PRINTING AND PUBLISHING HOUSE. 1888. COPYRIGHT, 1888, BY JENNIE E. CHEEVER. PAET I. EKRATA. Pr ge 8, third line, weight should read weigh. Page 33, eleventh line, diliquescent should read deliquescent; Bottle 12 should read Box 12. Page 35, second paragraph, page 10 should read page 14. Page 39, second paragraph, page 21 should read page 24. Page 49, paragraph (e), page 20 should read page 28. v Page 59, fifth paragraph, page (>o should read page 66; first footnote should read Fresenius 439. Page 61. first paragraph, page. 52 should read page GO; second par- agraph, page 70 should read page 76. Page 63, second paragraph, page 47 should read page 57. PAftT I, LABOEATOEY NOTES FOK A BEGINNERS COURSE QUANTITATIVE ANALYSIS, Ceo?; (fot> REFERENCES. ERESENIUS: Quant. Anal.; 7th Ed, CLASSEN. CBOOKES: Select Methods ; 2d Ed. WATTS' Dictionary. STJTTON: Volumet. Anal. ; 5th Ed. HART: Volumet. Anal. Chemical News. LIST OF ELEMENTS.* Hydrogen = 1. Name. Symbol. Atomic Weight. Atomic Weight Adopted in this Edition. Aluminium . Al 21 04 27 04 Antimony. Sb 119 6 119 6 Arsenic .. As 74 9 75 Barium Ba 136 86 136 9 Bismuth Bi 207 5 207 5 Bromine Br 79 76 79 8 Boron B - 10.9 11 Cadmium Cd 111 7 111 7 Calcium Ca 39 91 40 Carbon. c 11 97 12 Cerium . . Ce 141 2 141 2 Chlorine Cl 35 37 35 37 Chromium Cr 52 45 52 45 Cobalt , Co 58 6 58 6 Copper. . Cu 63 18 63 18 Fluorine F 19 06 19 06 Gold Au 196 2 196 2 Hydrogen H 1 1 Iodine I J26 5 126 5 Iron Fe 55 88 56 Lead Pb 206 39 206 4 Lithium Li 7 01 7 01 Magnesium Mg 23 94 24 Manganese Mn 54 8 55 Mercury Hg 199 8 199 8 Molybdenum.. Mo 95 9 96 Nickel Ni 58 6 58 6 Nitrogen N 14 01 14 Oxygen . o 15 96 16 Platinum. . . . Pt 194 3 194 3 Phosphorus . . . p 30 96 31 Potassium K 39 03 39 Silver As 107 66 107 66 Silicon sf 28 28 Sodium Na 22 99 23 Strontium Sr 87 3 87 3 Sulphur. . s 31 98 32 Tin Sn 117 35 117 35 Titanium.... Ti 50 25 50 25 Tungsten W 183 6 183 6 Uranium Ur 239 8 240 Zinc Zn 64 88 65 Meyer Atomgewichte. 819475 RULES FOR WEIGHING. 1. Level and adjust the balance. 2. Always place the substance to be weighed upon the same pan most conveniently upon the left. 3. Never place the substance upon the naked pan; use counterpoised watch-glasses, or a weighed porcelain or platinum dish. (Never use paper). 4. Always bring the balance to a rest, before placing upon or removing a substance or weight from the pans. 5. Use forceps, if possible, in placing upon and remov- ing dishes from the pans. 6. Always handle weights with forceps; never touch them with the hand. 7. Never weigh a vessel or substance while warm. 8. Never try weights at random; commence with the weight nearest to, and less than the substance, and add the weight next in succession till the correct weight is obtained. 9. Liquids, and solids which are volatile, or give off or absorb moisture when exposed to the air, must be weighed in closed vessels. All other substances may be weighed in the open air. SPECIFIC GRAVITY.* The specific gravity of a body is the weight of that body as compared with the weight of an equal volume of a standard body, which is taken as unity. In all cases of solids and liquids, this standard of unity is pure water at 60 F. = 15.5 C. Water being taken as unity, or one, any other sub- stance will be more or less than one. The results are expressed in whole numbers and decimals; the decimals are carried to the third place. Water = 1.000 (one, not one thousand). Alcohol = 0.815 Sand = 2.127 Cfravimetric Methods of Determining the Specific Gravities of Solids and Liquids. The following classification will serve for all solids and liquids which are likely to occur in ordinary investi- gations. 1. Liquids, heavier or lighter than water. 2. Solids, in powder, heavier than water and insoluble in it. 3. Solids, in mass, heavier than water and insoluble in it. 4. Solids, lighter than water and insoluble in it. 5. Solids, soluble in water. CLASS I. Liquids, heavier or lighter than water. Take a specific gravity bottle, clean and dry it; cool and weigh. * Watts Diet' V 357. 8 SPECIFIC GRAVITY. Now fill the bottle with distilled water at 60 F., (there must not be any air bubbles about the stopper) and again weight it. It will not be accessary to repeat these weighings except in cases of accident. Empty and dry bottle, cool and fill with the liquid at 60 F., (avoiding air bubbles as before) and weigh. We thus obtain the weight of an equal volume of pure water and liquid thus: Let B = sp. gr. bottle, W = distilled water, and L = the liquid. B + W = 30 grms. B + L = 38 grms. B = 10 grms. B = 10 grms. . W = 20 grms. L - 28 grms. To find the sp. gr. of the liquid, divide the weight of the liquid by the weight of pure water. L 28 = = 1.400 sp. gr. of the liquid; W 20 or, placing it in the form of a proportion, 20 : 28 : : 1.000 : x, = sp. gr. Determine the sp. gr. of the following table reagents : HC1 HN0 3 -H(C 2 H 3 2 )-KHO-NH 4 HO C 2 H 6 O. CLASS II. Solids, in powder, heavier than water and insoluble in it. (Soxes 1 and 2.) Clean and dry the specific gravity bottle, cool and put into it from 2 to 5 grms. of the powder and weigh. Then fill the bottle with distilled water (avoiding air bubbles) and weigh. Result: B + W = 30 grms. B + S = 20 grms. B 10 grms. B =10 grms. W = 20 grms. S = 10 grms. B + S + W = 36grm. W = 20 B + S = 20 - W 1 = 16. W 1 = 16 " W 11 = 4. SPECIFIC GRAVITY. 9 W = the weight of water which the bottle holds. W 1 = " " " above the substance. \yn K c< displaced by the substance. Displaced water has the same volume as the substance which displaced it; and since we have the weight of the substance, and the weight of the water displaced by it, we therefore have the weight of an equal volume of both. Applying the rule just given, we have S 10 = = 2.500 the sp. gr. of S. W 11 4 CLASS III. Solids, in mass, heavier than water and insoluble in it. (Sox 5.) Suspend the substance from the arm of the balance by means of a horse-hair, and then weigh. Now place a beaker of distilled water in such a position that the sub- stance hangs freely in it, and again weigh, (see that no air bubbles adhere to the substance). The loss in weight is equal to that of the water dis- placed. Thus S in air = 25 grms. " water = 15 " Loss = 10 " which is the weight of the displaced water, = W S 25 = = 2.500 sp. gr. of S. W 10 CLASS IY. Solids lighter than water and insoluble in it. (Soxes 4 and 5.) These being lighter than water, will not sink in it;: therefore some heavy substance must be attached to them,, to sink them, and thus displace the water. 10 SPECIFIC GRAVITY. Take as an example, wood: 1. Weight of sinker in air = 50. 2. " " " + wood " = 183. wood " = 133. 3. Weight of sinker + wood in water = 38. 4. " " " in water = 44. 2wt. 3wt. ( Weight of the water displaced ) W i 183 38 = 145 ( by sinker and wood. J Iwt. 4wt. ( Weight of the water displaced ) _ W11 5044= 6} by sinker. J ~ W 1 W 11 ( Weight of the water displaced ) _ W111 145 6 = 139 I by wood. J ~ Wood 133 = = 0.956 sp. gr. of wood. W m 139 CLASS V. Solids soluble in water. (Sox 6.*) Select some liquid in which the solid is insoluble, and -determine its sp. gr. Then proceed to determine the sp. gr. of the solid according to directions given for Class Two, using this liquid instead of water. (The substance in Box 6 is insoluble in alcohol.) Multiply the sp. gr. thus obtained by the sp. gr. of the iliquid used; the product will be the true sp. gr. QUANTITATIVE ANALYSIS. PRELIMINARY STEPS. 1. Selecting the Sample. The mode of selecting the sample will depend upon the object sought. In commer- cial work the sample should be so selected as to represent as nearly as possible the average quality of the whole. This, can be best accomplished by pulverizing a large quantity, taken from different parts of the mass, thor- oughly mixing the same and then taking from this a small sample for analysis. In technical work, pure, clean crystals should be se- lected. 2. Mechanical Division. Substances soluble in water or readily soluble in acids, are only pulverized moderately fine; they must be fine enough, however, to insure a uniform sample. A porcelain mortar answers for this work. Substances not readily dissolved by acids, or sol- uble only after fusion, must be reduced to an impalpable powder with an agate mortar. 3. Drying the Sample. The sample, when ready for analysis, must be in a definite state, that is, in a condition in which it can always be obtained a second time, if by accident or otherwise a new sample has to be prepared. This is accomplished by drying, which removes the hy- groscopic moisture. The mode of drying will depend upon certain physical characteristics peculiar to different bodies. Classification of Substances, with reference to the mode of drying. (a). Substances which lose water of constitution or crystallization when exposed to air are dried by pressing between folds of blotting paper. 12 QUANTITATIVE ANALYSIS. (6). Substances which only give off water in artifici- ally dried air, are pressed between folds of blotting paper and then left for some time exposed to the air, protected from dust by paper or otherwise. (c). Substances which undergone change in dry air, but lose water at 100 C., are dried in a desiccator over H 2 SO 4 or CaCl 2 . (d). Substances which give off all their moisture at 100 C., but undergo no other change, are dried in a water bath at 100 C. (e). Some substances retain moisture at 100 C., this moisture is generally determined and returned as per cent. GRAVIMETRIC DETERMINATIONS. The crucible which is used for igniting and weighing the precipitate must be cleaned, heated, cooled in the desiccator, and weighed before each ignition. The ash of the filter must also be determined by in- cinerating two or more filters till white, and weighing the resulting ash. Boxl. BARIUM CHLORIDE. Estimation of Barium. Take an exact weight (about 0.5 grm.*) of the substance, dissolve in 100 c. c. of water, acidulate with HC1, boil and add, drop by drop, dilute H 2 S0 4 as long as a precipitate forms; boil for some time, then place to one side until the precipitate has completely subsided ; filter by decantation and wash with hot water, until silver nitrate produces no turbidity in the washings. Dry, ignite, cool, add a few drops of HjSO^, ignite moderately till fumes are no longer given off, cool and weigh. Result, BaSO 4 . Calculation. BaSO 4 : Ba : : wt BaSO 4 : x = wt. of Ba found. Wt. taken : x : : 100 : y per cent, of Ba. Estimation of Chlorine. Dissolve 0.2 grms. in 50 c. c. of warm water, add silver nitrate in slight excess, then acidify with HNO 3 , heat and agitate briskly; place the beaker for a short time in a warm, dark place, then filter *The beginner should never weigh 1. grm. or .5 grm., but take a quantity, near the amount specified, and weigh it carefully. Some- times a definite amount will be specified, when from the context it will be evident that an approximate quantity is intended. 14 GBAVIMETEIC DETEEMINATIONS. and wash with hot water. Wash till filtrate gives no precipitate on adding HC1. Dry, remove the precipitate from the filter, incinerate the filter, then add the precipitate to the ash, cool, add 5 drops of HNO 3 , heat gently, then add 10 drops HC1, heat on water bath till dry, then ignite until the AgCl begins to fuse. Kesult = AgCl. Calculation. AgCl : Cl : : wt. AgCl : x = Cl in wt. taken. Wt. taken : x : : 100 : y = per cent, of Cl. To remove the fused AgCl from the crucible, place upon it a piece of Zn and add dilute H 2 SO 4 . Sox 2. MAGNESIUM SULPHATE. Estimation of Magnesium Oxide Dissolve 0.5 grm. in 50 c. c. of water, add NH^Cl, then NH^OH in excess (no precipitate should be formed; if there is, add HC1 till dissolved; then add NH 4 OH in excess); cool, and add sodium-ammonium phosphate in slight excess; agitate briskly, allow to stand till the supernatant liquid is clear; filter and wash the precipitate with a mixture of one part ammonium hydrate and three parts water, until the addition of HKO 3 and AgK0 3 to the filtrate does not produce a precipitate. Dry and ignite (commencing with a low heat) until constant weight is obtained. If, after ignition, the precipitate is not pure white, moisten it with nitric acid, and again ignite. Result = Mg 2 P 2 O 7 . Calculation. Mg,P 2 O 7 : 2MgO : : wt. Mg 2 P 2 O 7 : x = MgO in wt. taken. Wt. taken : x : : 100 : y = per cent, of MgO. Estimation of Sulphuric Add. Dissolve 0.5 grm. in 30 c. c. of water, acidulate with HC1, boil and add to it a GRAVIMETRIC DETERMINATIONS. 15 boiling solution of Barium chloride, as long as a precip- itate is formed; (now proceed as directed under Box 1 for the estimation of Barium.) Box 3. FERROUS SULPHATE. Estimation of Metallic Iron. Dissolve 1 grm. in 25 c. c. of water strongly acidulated with HC1, boil, and add small crystals of KC1O 3 , until all the iron is oxidized to the ferric salt; continue the boiling and add more HC1 if necessary, until the KC1O 3 is decomposed and the solution no longer emits an odor of chlorine; cool and add NH 4 OH in excess; boil, filter by decantation and wash with hot water, until silver nitrate produces no turbidity in the washings when acidulated with HNO 3 . Dry, ignite and weigh. Result = Fe 2 O 3 . Calculation. Fe 2 3 : 2Fe : : wt. Fe 2 O 3 : x Fe in wt. taken. Wt. taken : x : : 100 : y = per cent, of Fe. Sox 4. CALCIUM CARBONATE. Estimation of Calcium Oxide Take, 0.5 grm., place in a large beaker, add 30 c. c. of water, cover with a clock- glass, then add gradually HC1, till effervescence ceases* heat, add ammonium oxalate in moderate excess, and then ammonia in slight excess, boil, remove to a warmr> place, and let stand twelve hours; filter by decantation and wash with hot water, until the wash water, acidu- lated with nitric acid, gives no precipitate with silver nitrate. Dry, ignite at a moderate heat, cool, moisten with* ammonium carbonate, heat to faint redness, cool and weigh; repeat this operation until constant weight is- obtained. Result - CaCO 3 . 16 GRAVIMETRIC DETERMINATIONS. Calculation. CaCO 3 : CaO : : wt. CaCO 3 : x = CaO in wt. taken. Wt. taken : x : : 100 : y = per cent, of CaO. Estimation of Carbon Dioxide. When CO 2 is com- bined with a base, it is generally determined by loss of weight which the substance sustains, when treated with a stronger acid or acid compound. The more common method is to employ some simple apparatus which will permit the expulsion of the CO 2 , without loss from other causes. The apparatus is charged with a weighed quan- tity of the substance containing the CO 2 , and with the acid which is to expel it, it is then weighed, and after weighing, the acid is allowed to come in contact with the substance, when the CO 2 is expelled, the apparatus is weighed again; the loss in weight is the weight of C0 2 . Wt. taken : loss : : 100 : x = per cent, of C0 2 . Sox 5. SODIUM PHOSPHATE. Estimation of Phosphoric Acid. Dissolve 0.5 grm. in 50 c. c. of water, add NH 4 OH in excess, cool, then add magnesia mixture in excess, agitate briskly; after stand- ing three hours in a cool place, filter, and wash with a mixture of one part NH 4 OH, and three parts water, until the wash water acidulated with HNO 3 , gives no precipitate with AgNO 3 . (The precipitate is slightly soluble in dilute ammonia water). Dry, and ignite. (For precautions see Box 2). Eesult = Kg, P 2 O T . Calculation. .Mg 2 P 2 O 7 : P 2 O 5 : : wt. Mg 2 P 2 O 7 : x = P 2 O 5 in wt. taken. Wt. taken : x : : 100 : y = per cent, of P 2 O 5 . GRAVIMETRIC DETERMINATIONS. 17 Sox 6. AHSENIOUS ANHYDRIDE. Estimation of Arsenic. Dissolve 0.5 grm. in KHO, with the aid of heat; acidulate with HC1, maintain the heat at 70 C., and pass H 2 S gas through the solution for one hour, filter and wash with hot water. If As 2 S 3 ad- heres to the tube and beaker, dissolve it in NH 4 OH and reprecipitate with dilute HC1, and transfer it to the filter. Dissolve the moist precipitate on the filter with cold NH 4 OH, to this ammoniacal solution add cold dilute HC1 until the solution is moderately acid, filter through coun- terpoised filters, and wash with water. Dry at 100 C., cool and weigh. Eesult = As 2 S 3 . Calculation. As 2 S 3 : As 2 : : wt. As 2 S 3 : x = As in wt. taken. Wt. taken : x : : 100 : y per cent, of As. VOLUMETRIC ANALYSIS. Volumetric analysis is a method for determining quantity by measure. The reagent and the material under examination must therefore be in solution. The reagents which must have an exact and known strength are called Standard Solutions. These are divided into 1. EMPIRICAL. 2. NORMAL. Empirical Solutions, are used for estimating one ele- ment only. They are prepared without reference to the atomic weights, and are generally of such strength, that 1 c. c. = 1 per cent, or the fraction of a per cent, when titrating a given weight of the unknown. Normal Solutions, are used for estimating all elements, with which they produce a distinct reaction. They are prepared so that a given measure contains an exact atomic weight. Normal Solutions, are prepared so that one litre at 16 C, shall contain the hydrogen equivalent of the active re- agent weighed in grms. (H = 1). If the substance is univalent the full atomic weight is used, if bivalent one- half, and if trivalent one-third. This rule does not hold good in all cases, and the whole, or, an aliquot part of the atomic weight of the reagent must be taken, depend- ing upon its peculiar reaction in any given analysis. Solutions of less strength than the normal will often be required. These solutions may be shortly designated as N" normal; f seminormal; f quintinormal; ^ decinor- mal; T $ T centinormal. Titrate, is the term applied to the method of estimat- ing quantitatively the amount of pure substance con- tained in a given substance or solution, by a standard or titrated solution. End reaction, is the term applied to^that point in the VOLUMETBIC ANALYSIS. 19 operation where no further change takes place between the known and the unknown.- The end reaction must be manifest to the eye, either by some change in the solution itself, or by an indicator. Keagents which produce no visible change, cannot be used to prepare standard solu- tions. Normal factor, is used to express the amount in grms of the active reagent in 1 c. c. of a normal solution. CLASSIFICATION OF METHODS. (1). Analysis by saturation, or acidimetry and alka- limetry. (2). Analysis by oxidation and reduction. (3). Analysis by precipitation. Alkalimetry and Acidimetry or the methods for esti- mating the per cent, of actual alkali or acid in a given solid or solution. The end reaction in these determinations is not mani- fested by the solution itself, hence an indicator must be used. INDICATORS. Phenolphthalein is a yellowish powder, soluble in alcohol. To prepare a solution for use dissolve .010 grm. in 10 c. c. of 50 per cent, alcohol. One or two drops is sufficient for each titration. Acids produce no change in color, alkalies produce an intense purple-red. This, though perhaps not the best indicator, has been found to work well in the hands of beginners, on account of its great sensitiveness. It cannot be used for titrating ammonia, or the caus- tic alkalies when ammoniacal salts are present. Cold or only moderately warm solutions must be used in titrat- ing, oxalic, citric, tartaric, acetic and other organic acids, with potassium or sodium hydrate. Hot solutions must be used in titrating alkaline and earthy hydrates, carbo- nates, and bicarbonates, and sulphides, with mineral acids. 20 VOLUMETRIC ANALYSIS. STANDARD SOLUTIONS. In preparing standard solutions, it is not always pos- sible to obtain the reagent in a definite and permanent form, so that the exact amount required can be weighed or measured out. In such cases the standard is obtained by titrating the reagent with some standard solution, and then calculating the dilution required to bring the reagent to the standard. The volumes of all standard solutions of a given class (as ^) must be equal, that is 1 c. c. of a given ^ solution must exactly neutralize 1 c. c. of an ^ solution of the opposite kind. In preparing ^ solutions for this part of the work, we will commence with oxalic add, since this acid can be obtained in a definite and permanent form. ^ OXALIC ACID. C 2 O 4 H 2 , 2H 2 O = 126 -=- 2 = 63. 6.3 grms. per litre. Weigh out exactly 6.3 grms of the freshly prepared crystals of oxalic acid, dissolve in water, and dilute to one litre. Each c. c. contains .0063 grms of the acid; therefore .0063 is the decinormal factor of oxalic acid. ^y POTASSIUM HYDRATE. KHO = 56. 5.6 grms. per litre. Take 50 c. c. of the table reagent, and dilute with water to 600 c. c., cool, and titrate with f \ oxalic acid, as follows: Take 5 c. c. of the KHO solution, add 2 drops of the indicator, and run in gradually from a burette ^ ox- alic acid, until a drop just disperses the red color. Make at least six titrations and take the average result. Example for Calculating the Dilution. Suppose 5 c.c. of the KHO solution required 8 c. c. of the ^ oxalic acid to produce the end reaction, or to neutralize it. The pot- ash solution is therefore the stronger and must be diluted with water, so that 5 c. c. of it will require just 5 c. c. of the T % oxalic acid to neutralize it; when so diluted, it will VOLUMETRIC ANALYSIS. be an ^ solution, for, as we have said, ^ solutions are all equal, and 1 c. c. of any ^ solution can be substituted for 1 c. c. of any other ^ solution of the same nature. The graduated cylinder has left in it 550 c. c. of the KHO solution; how many c. c. of an T ^ solution will it make? 5 c. c. : 8 c. c. : 550 c. c. : x = 880 c. c. Now add water to the 550 c. c. until it has been raised to 880 c. c., mix thoroughly, and again titrate with the T \ oxalic acid; the solutions should be equal. Each c. c. contains .0056 grms KHO. Burettes with glass taps must not be used for measur- ing caustics. ^ SULPHURIC ACID. H 2 SO 4 = 98 -r- 2 = 49. 4.9 grms per litre. Take 5 c. c. of the table reagent, dilute with 300 c. c. of water in a porcelain dish, transfer to the graduated cylin- der, cool, and titrate with & KHO solution; see direc- tions for titrating and making an -f^ solution of KHO. Each c. c. contains .0049 grms. H 2 S0 4 . ^ NITRIC ACID. HNO 3 = 63. 6.3 grms. per litre. Take about 5 c. c. of the table reagent, dilute with 200 c. c. of water, and titrate with & KHO solution; see direction for H 2 SO 4 . Each c. c. contains' .0063 grms. HNO 3 . (The H]STO 3 must be free from nitrous fumes). NORMAL OXALIC ACID. Take 6.3 grms., dissolve in 80 c. c. of water, and dilute to 100 c. c. NORMAL SODIUM HYDRATE. Take about 15 grms. NaHO, place it in a porcelain dish, dissolve in 150 c. c. of water, cool, transfer to a grad- uated cylinder, and titrate with normal oxalic acid. 22 VOLUMETRIC ANALYSIS. From the results calculate the dilution necessary to make a normal solution. NORMAL TARTARIC ACID. Take about 20 grms. tartaric acid, dissolve in 150 c. c. of water, cool, and titrate with normal sodium hydrate. Titrations. All material, whether solid or liquid, which is to be titrated for the per cent, of any given element, must be weighed. For convenience in weighing, dissolving, or diluting, select a two-ounce, globe-shaped flask, clean, and dry, and then graduate by running into it, water, from a burette till a distinct meniscus is formed in the neck, and an even number of c. c. has been used; mark this point by a label which bears the number of c. c, used. This we will call the weighing flask. TITRATION OF HYDROCHLORIC ACID. HC1 = 36.37. ft factor = .003637. Take about 5 c. c. o the table reagent, place it in the weighing flask, and weigh; dilute with water. Mix thoroughly, cool, and dilute to the mark. Fill a glass tap burette with this solution, and a Mohr's burette with ft KHO. Run into a small beaker 5 c. c. of the HC1 solution, add two drops of the indicator and titrate with the ft KHO; repeat the titration three or four times and take the aver- age result. Calculation. To find the per cent, of HC1. HC1 taken, weighed 5.6 grms. Weighing-flask holds 60 c. c. 20 c. c. of ^ KHO were required to neutralize 5 c. c. of the diluted HC1. 5 c. c HC1 : 20 c. c. ft KHO : : 60 c. c. : x = 240 c. c. ft KHO. Therefore 240 c. c. ft KHO would be required to neu- VOLUMETBIC ANALYSIS. 23 tralize 5.6 grms. HC1 (that is the 60 c. c.); or by diluting the 60 c. c. with water to 240 c. c. we would have an ft solution of HC1. 1 c. c, of an -ft HOI contains .003637 grms. HC1, there- fore, 1 : .003637 : : 240 : y = 0.87288 grms. HC1 in wt. taken. Wt. taken (5.6 grms.) : 0.87288 : : 100 : z - per cent, of HC1 = 15.58. Volatile liquids, as NH 4 OH and HC# must be weighed in well stopped bottles. The titration of Acetic Acid by a standard caustic alkali is not rigidly exact, for neutral acetates have an alkaline reaction. Titrate the following table reagents : H]STO S ft factor = .0063 HC1 " " = .003637 C a O,H 4 " " = .006 KHO " " = .0056 Boxl. CITRIC ACID. C 6 O 7 H 8 + H 2 O = 210 -f- 3 = 70. ft factor = .007 Dissolve about 0.2 grm. in water, in the weighing ilask, and dilute to the mark, then titrate with ft KHO. Sox 2. SODIUM CARBONATE. Na 2 CO 3 . To be titrated for Na 2 O = 62 -=- 2 = 31. ft factor of Na 2 = .0031. Place about 0.5 grm. in the weighing flask, dissolve in water and dilute to the mark. Take 5 c. c. of this solution in a small beaker, add some water, then add two drops of the indicator, and run in from a burette ft H 2 SO 4 , % c. c. at a time (boiling after each addition) till the H 2 SO 4 is in excess; boil at least five minutes after the last addition of H Z SO 4 . How titrate back the excess of H 8 S0 4 with ft KHO. A drop or two 24 VOLUMET1UC ANALYSIS. of the indicator may be required from time to time dur- ing the titration. The difference between the HgSO^ and KHO used, is the amount of H 2 !SO 4 required to neutralize the 5 c. c. Box 3. SODIUM BICARBONATE. NaHCO 3 . To be titrated for NaHO = 40 ft factor of NaHO = .004 Follow directions for Box 2. Sox 4. CALCIUM CARBONATE. CaCO 3 . To be titrated for CO 8 = 44 -5- 2 = 22. Normal factor for CO 2 = 0.022 Take about .05 grm. in a large beaker, add water enough to cover the bottom of the beaker, then titrate according to directions given for Box 2, using normal HNO 3 in place of ft H 8 S0 4 . Bottle 5. SOLUTION OF CAUSTIC POTASH AND SODA. (Must not be weaker than a normal solution). Normal factor of KHO = .056. Normal factor of NaFO = .04. Place about 10 grms. mafias) (must not dilute), run in from a burette normal tarta ; acid, till neutral or faintly acid, note the number of , c. used, and then run in just as much more. This will >rm a bitartrate of pot- ash and soda; cork the flask and aake violently for a few minutes, this will cause the p' assium bitartrate to sep- arate almost completely, sine it is insoluble in sodium bitartrate. Filter and wher the nitrate has all passed through, rinse out the flask with 5 c. c. of water and pour it on the filter; when all has passed through, titrate the filtrate with normal NaHO; the number of c. c. of normal NaHO required, equals the soda in the mixture. VOLUMETRIC ANALYSIS. 25 Calculation. 10 grms. of the solution were taken. 5 c. c. of normal NallO were used; 5 X .04 = 0.2 grms. of NaHO in wt. taken. 10 : 0.2 : : 100 : x = 2 per cent, of NaHO. 24 c. c. of normal tartaric acid were used; 24 c. c. 10 c. c. (the amount of tartaric acid in combination with soda as bitartrate) = 14 c. c. the amount of acid in com- bination with the potash as bitartrate; 14 c. c. -+- 2 = 7 c. c., the amount of normal acid required to make a neu- tral tartrate of the potash. 7 x .056 = .392 grm. KHO in wt. taken. 10 : .392 : : 100 : y = 3,92 per cent, of KHO. OXIDATION AND REDUCTION. The most available oxidizing reagents are KMnO 4 , K 2 Cr 2 O,, and I. The most available reducing reagents are FeSO 4 , C 3 O 4 H 2 2H 2 O, H 2 SO 3 , Na 2 S 2 O 3 , As 2 O 3 , and SnCl 2 . & POTASSIUM PERMANGANATE. KMnO 4 = 158 -f- 5 = 31.6. 3.16 grms. per litre. Select some clean crystals, dry them for forty-eight hours in a desiccator over H 2 SO 4 ; then weigh out 3.16 grms., dissolve in water and dilute to one litre. If the salt is pure, the solution will be &; but as this is not always the case it must be titrated with some reducing reagent which has a definite and constant composition. & KMnO 4 cannot be used when there is much free HC1 present in the solution to be titrated, for free HC1 reduces the permanganate. In preparing standard solutions it is never safe to rely upon a solution ma.cle by taking a required weight, for 2b VOLUMETRIC ANALYSIS. there may be some impurity in the reagent. The solution should always be compared with one or more solutions of the opposite kind. TITRATION OF PERMANGANATE. (a) With ft Ferrous Sulphate Measure with a pipet- te, 5 c. c. of ft FeSO 4 into a small beaker, add some dilute H 2 SO 4 (1 to 5), and titrate with the ft permanganate, till a faint, permanent permanganate color is produced, (use a glass tap burette). Reaction. 10FeSO 4 + 8II 2 SO 4 + 2KMnO 4 = 5Fe 2 (SO 4 ) 3 + 2MnSO 4 + K 2 SO 4 + 8H 2 O. (6) With ft Oxalic Acid. Follow directions given under (a); (warm the oxalic acid to 60 C., before titrating). Reaction. 5C 2 H 2 4 + 3H 2 S0 4 -f 2KMn0 4 = K 2 SO 4 + 2MnSO 4 + 8H 2 + 10C0 2 . (c) With ft Sodium Hyposulphite. Measure into a flask one ounce of KI table reagent (which has no free iodine), add 2 c. c. HC1 (1.16), dilute largely with water, then run in 5 c. c., of ft KMnO 4 , cork the flask, and shake thoroughly; (must be kept cold), now titrate with ft sodium hyposulphite, until the solution is colorless, then run in ft KMnO 4 , one drop at a time till the iodine color re-appears. ft POTASSIUM BICHROMATE. K 2 Cr 2 O 7 = 294.9 -j- 6 = 49.15. 4.915 grms. per litre. Weigh 4.915 grms. of the pure crystals, dissolve in water, and dilute to one litre. Bichromate possesses the advantage over permangan- ate, that it is absolutely permanent in solution, may easily be obtained in a pure state, may be used in a Mohr's burette, and can be used in the presence of free sulphuric or hydrochloric acid. It possesses the disadvantage, in VOLUMETRIC ANALYSIS. 27 that, it requires an indicator, and cannot be used in the presence of zinc. Indicator Required. Potassium Ferricyanidemust be freshly prepared, and so dilute, that when a drop is placed on a marble slab it shows but a faint color. TITRATION OF BICHROMATE. (a) With ft Ferrous Sulphate. Measure, with a pip- ette, 5 c. c. of ft FeSO 4 , into a beaker, add some dilute H 2 SO 4 and run in ft K 2 Cr 2 7 , till a drop, brought in con- tact with a drop of the indicator on a marble or porcelain slab fails to give a blue color. Reaction. 6FeS0 4 + 7H 8 S0 4 + K 2 Cr 2 O T = 3Fe 8 (SO 4 ) s + K 2 SO< + Cr 2 (S0 4 ) 3 + 7H 2 0. (6) With ft Sodium Hyposulphite according to direc- tions given under titration of permanganate (c). ft IODINE. Iodine = 126.5. 12.65 grms. per litre. Place in a glass stoppered bottle about three grms. and weigh. (The bottle must be kept closed while weighing to prevent the iodine, which is very volatile, from injur- ing the balance). Prepare a solution of KI by taking ten grms. and dissolving it in 100 c. c. of water; transfer the iodine to the graduated cylinder, rinsing the weighing bottle with this solution ; shake the cylinder till the iodine is dissolved. To calculate the dilution. 12.65 : 1000 : : wt. taken : x. x = dilution. This solution changes after standing some time, and must therefore be often tested. TITRATION OF IODINE. (a) With & Sodium Hyposulphite Take 5 c. c. of ft 28 VOLUMETRIC ANALYSIS. sodium hyposulphite, add a few drops of starch indicator, and run in the iodine solution till one drop produces a permanent blue color. (The solution must not be heated). Reaction. 2Na 2 S 2 O 3 + 21 = 2NaI + Na 2 S 4 O 6 . (c) With A Arsenious Add. Take 5 c. c., of T ^ arsen- ious acid, add starch indicator and titrate; (as given under (a) ). Reaction. As 2 O 3 + 2Na 2 O -f 41 = As 2 O 5 STARCH INDICATOR. Take one part of starch, triturate in a mortar with cold water, then pour over it 200 parts of boiling water, and boil a short time; allow it to cool and settle, then draw off the clear liquor for use. $j- FERROUS SULPHATE. Weigh out one or two grms. of clean, fine, soft, iron wire, dissolve in dilute H 2 SO 4 by the aid of heat, in a small flask closed with a cork through which passes a glass tube drawn out to a fine point at the upper end; when dissolved, transfer to the graduated cylinder, and dilute according to the following proportion: 5.6 : 1000 : : wt. taken : x. x dilution. Since pure iron wire cannot readily be obtained, it is nec- essary to ascertain the per cent, of impurity and deduct the same from the amount taken. The Ammonio-ferrous Sulphate is a good and conven- ient substitute for the ferrous sulphate. The formula of this salt is, Fe(]SrH 4 ) 8 (SO 4 ) 2 , 6H 2 O, consequently it con- tains one-seventh of its weight of iron. Preparation. To 50 c. c. of water add 12 c. c. of strong H 2 S0 4 and divide into two equal portions. Place one portion in a flask, add a slight excess of small nails, free from rust, and allow the flask to stand in a warm place VOLUMETKIC ANALYSIS. 29 over night. In the morning add enough water to restore the solution to its original bulk, warm at 70 C., till the evolution of hydrogen has ceased or nearly ceased, add- ing water from time to time if necessary; now filter through a warm funnel into a warm dish. To the other portion add ammonium carbonate in lump till violent action ceases, then warm and add it in powder till the solution is neutral, and filter if necessary. Mix the two solutions in a beaker, heat to 80 or 90 C, mix thoroughly, add a few drops of H 2 SO 4 if the solution is not already acid, then pour into a porcelain dish, and stir till cold. Allow to stand some hours, decant the mother-liquor, transfer the bluish-white powder to a fun- nel and apply suction; wash three or four times with alcohol, and then dry on filter-paper, without heat, till the powder will run like sand. Preserve in ground-stop- pered bottles. & AMMONIO- FERROUS SULPHATE. . Take 3.92 grms., add 5 c. c. H 2 SO 4 , and dissolve in water, and dilute- to 100 c. c. For testing the strength of permanganate or bichro- mate solutions, take about 0.5 grm. of the iron salt, dis- solve in water acidulated with H 2 SO 4 and titrate. ^ SODIUM HYPOSULPHITE. Na 2 S 2 O 3 , 5H 2 O = 248. 24.8 grms. per litre. First powder and dry a quantity of the salt by press- ing between folds of blotting paper, then weigh 24.8 grms., dissolve in water, and dilute to one litre. Directions for titrating are given under " T ^ Perman- ganate and Iodine." The solution should be kept in the dark; after a time it undergoes a slight amount of oxidation, and sulphur deposits on the bottle. This it is said can be prevented by adding two grms, of Ammonium Sesquicarbonate or a little caustic soda to a litre of the solution. 30 VOLUMETRIC ANALYSIS. ft ARSENIOITS ANHYDRIDE. As 2 O s = 198 -5- 4 = 49.5. 4.95 grms. per litre. Weigh approximately 3 grms., place it in a flask, add 25 grms. of pure Sodium Bicarbonate, and about 250 c. c. of water; boil till dissolved, cool, decant the clear solution into a graduated cylinder; titrate with ft Iodine, and calculate the dilution required to make an ft solution of the As 2 O 8 . After diluting again titrate with ft Iodine to make certain of its accuracy. OXIDE OF IRON. To be titrated for Fe by ft KMnO 4 . ft factor of Fe = .0056. Weigh out 0.5 grm., place it in a porcelain dish, add strong HC1, mix thoroughly, cover with a clock glass and heat at 100 C., till dissolved; cool, then add strong H 2 S0 4 and evaporate till S0 3 fumes appear, cool, add water and dilute the solution to a given number of c, c., measure 10 or 20 c. c. into a beaker, dilute with water, add Zn, and enough 112804 to produce a brisk evolution of hydrogen; warm and allow the action to go on until the Fe 2 O 3 is all reduced to FeO, remove the Zn, and heat till the bubbles are all removed, then titrate with ft KMn0 4 . Note : The Zn should always be tested to ascertain if it has reducing power; and if it has, this must be deter- mined, and the amount of KMnO 4 which a given weight will reduce, deducted from the total KMnO 4 used. Boxl. IRON ORE. To be titrated for Fe by ft Na 2 S 2 O 8 . ft factor of Fe = .0056. Pulverize the sample very fine with an agate mortar, dry at 100 C. then weigh 0.5 grm., digest in a flask with VOLUMETRIC ANALYSIS. 31 strong HC1 at 100 C. When dissolved, cool, transfer to a graduated cylinder and dilute to 200 c. c.: take 5 c. c., dilute largely, add 3 c. c. of a one per cent, solution of Copper Sulphate, and two drops of KCyS, now titrate with fa Na 2 S z O 3 until the red color disappears. The solution must be cold, and must remain clear. The copper is alternately reduced by the Hyposulphite and oxidized by the Fe,Cl 6 . Also titrate the same solution for Fe in the following manner: Take 5 c.c.boil and run into it from a burette a solution of SnCl 2 (50 grms. to 500 c. c. of % strength HC1) one drop at a time, till all the Fe 2 O 3 is reduced to FeO, and the tin solution is in slight excess; now add 10 c. c. of a cold saturated solution of HgCl 2 , (60 grms. per litre) shake well, and titrate with fa K 2 Cr 2 7 . Box 8. FERROUS AND FERRIC OXIDES. To be titrated for FeO, fa factor - .0072 To be titrated for Fe 2 O 3 , fa factor = .008 Pulverize in an agate mortar, and dry at 100 C.; weigh out 1 grm., place it in the weighing flask, add strong HC1 close the flask with a cork, through which passes a glass tube; digest at 100 C till dissolved, cool, and dilute to the mark. Measure out 10 c. c. and titrate as quickly as possible with -fa K 2 Cr 2 O 7 ; this will give the FeO. Measure out 10 c. c.; reduce with SnCl 2 and titrate total Fe. Deduct the amount of FeO obtained by the first tit- ration and figure the remainder as Fe 2 O 3 . Sox 9. ARSENIOUS ANHYDRIDE = 198. fa factor of As 2 O 3 = .00495 fa factor of As = .00375 Weigh out 0.2 grm., and dissolve it in 50 c. c. of a sat- urated solution of pure sodium bicarbonate, with the aid 32 VOLUMETBIG ANALYSIS. of heat; cool and dilute to a given number of c. c.; meas- ure out samples, and titrate with ft iodine and starch. This method gives the As 2 O 3 only and not the As 2 O 5 which is always present in the commercial article. If the As 2 O 5 is to be estimated it must first be reduced to As 2 O 3 by SO 2 gas. Bottle 10. TINCTURE OF IODINE. Iodine = 126.5. ft factor = .01265. First test the sample to see whether it is a simple or compound tincture by adding water to a small portion, which will produce a precipitate in the former but not in the latter. If it is a simple tincture, dry the weighing flask, then put into it a few c. c. of the tincture and weigh; now add some KI solution, and dilute to the mark. If it is a compound tincture, weigh without the above precau- tions, and dilute with water. Now measure out samples and titrate with ^ Na 2 S 2 O 3 , also with ft As 2 O 3 . Bottle 11. BLEACHING POWDER = Ca 3 H 6 O 6 Cl 4 . ft factor = .003537. Commercial bleaching powder consists of a mixture of calcium hypochlorite (the true bleaching agent), calcium chloride and nydrate, and in some cases calcium chlorate. It is generally valued and sold in this country by its per-centage of chlorine. Weigh 5 grms. and triturate it in a porcelain mortar with water; pour the milky liquid into a graduated cylin- der, triturate the residue with water, and repeat the oper- ation till all has been transferred to the cylinder, then dilute to 500 c. c.; shake well and take of the milky liquid 10 c. c., and run into it an excess of ft As 2 O 3 (20 c. c.), shake well, add starch indicator and titrate back the excess of As s 3 with ft Iodine, VOLUMETRIC ANALYSIS. 33 BY PRECIPITATION. & SILVER NITRATE. AgN0 3 - 169.66. 16.966 grms. per litre. Dissolve 4.2418 grms. in water and dilute to 250 c. c. $5- SODIUM CHLORIDE. ZSTaCl = 58.37. 5.837 grms. per litre. Dissolve 2.918 grams, in water and dilute to 500 c. c. ffr AMMONIUM SULPHOCYANATE, KH 4 SCN = 76. 7.6 grms. per litre. This solution cannot be prepared by weighing the salt, owing to its diliquescent nature; therefore dissolve about 4 grms. in 400 c. c. of water and adjust by titrating with & AgNO 3 , (see directions given below). Indicators. (a) Normal Potassium Chromate (K 2 CrOJ, (it must be free from chlorine). Make a cold saturated solution; it can be used only with neutral solutions and in titrat- ing chlorine in chlorides. (6) Ammonia Ferric Alum, Make a saturated solu- tion. TITRATION OF SILVER NITRATE. (1) With & Sodium Chloride. Place 5 c. c. of & NaCl in a beaker, add 2 drops of indicator (a), and titrate with 3% AgNO 3 till a faint, permanent red precipitate is formed. (2) With & Ammonium Sulphocyanate. Place 5 c. c. of ^ AgN0 3 in a beaker, add 3 drops of indicator (6) and about 1 c. c. of HN0 3 , titrate with & sulphocyanate till a faint permanent red color is produced. Bottle 12. SODIUM CHLORIDE. To be titrated for Cl. T \ factor of Cl = .003537 4 34 VOLUMETEIC ANALYSIS. Dissolve 0.5 grm. in the weighing flask with water, dilute to the mark; measure out several samples and titrate with -ft AgN0 3 , using indicator (a). Bottle 13. SILVER NITRATE SOLUTION. To be titrated for Ag. ft factor of Ag = .010766 (1) Take 3-5 grms. of solution, and titrate with ft sul- phocyanate, without dilution. (2) Take known weight of silver solution in a beaker; run in excess of ft NaCl; add Indicator and titrate back with T \ Ag N0 3 . Bottle 14. Hydrocyanic Acid, HCN = 27. ft factor = .0054 Weigh about 5 grms. in a tightly stoppered flask, then add a solution of KHO till decidedly alkaline and dilute largely; now run into the whole solution, ft AgNO 3 till a slight permanent precipitate remains. Reaction. 2KCy + AgN0 3 = KCy,AgCy + KNO 3 (no precipitate), + AgNo 3 = precip = 2AgCy + GRAVIMETRIC SEPARATIONS. Boxl. SILVER COIN = Ag + Cu (+ traces of Au & Pb). Clean the sample by washing with KHO, or N then with water, dry, cool, and weigh; place it in the weighing flask, dissolve with HN0 3 (avoiding an excess), cool, and dilute to the mark. Take 30 c. c. of this solution, heat to 70 C., and add HC1 as long as a precipitate is formed (a large excess of HC1 must be avoided); stir thoroughly, let it stand in a dark place till the precipitate has fully settled, filter by decan- tation, wash first with hot water acidulated with HN"O 3 . then with pure water, dry, etc. (See page 10). Return the per cent, of Ag. Boil the filtrate, remove the lamp, add gradually KHO solution till strongly alkaline, boil for 15 minutes, filter and wash by decantation with hot water, until the wash water gives no precipitate with Ag^TO 3 . Dry, ignite and weigh. Result = CuO. Return the per cent, of Cu. Titrate a portion of the original solution with ^ sul- phocyanate, as a check upon the gravimetric determina- tion of the silver. Box 2. BRASS = Cu. -f Zn. (-J- traces of Sn. and Pb.). Take about 0.2 grm., dissolve in HN0 3 , evaporate to dryness, moisten with HNO 3 , add water, and heat. If there is a residue, filter. Res. (a) SnO 2 . Dry, ignite and weigh, result =. SnO 2 ; return the per cent, of Sn. 36 GRAVIMETRIC SEPARATIONS. Filt. (a) = Cu. Zn. Pb.; add 3 c. c. H 2 SO 4 , evaporate in a porcelain dish till copious white fumes of SO 3 are given off, cool, add 50 c. c. of cold water; if there is a residue, add 20 c. c. of alcohol, filter and wash with dilute alcohol <1 to 4). Pp. (6) = PbSO 4 , dry, ignite, cool, add a few drops of H 2 SO 4 , cover the crucible, heat moderately till excess of H 2 SO 4 is driven off; then ignite strongly. Kesult = PbSO 4 ; return the per cent, of Pb. Filt. (b) = Zn. Cu.; heat on the water bath until the alcohol is expelled, cool, dilute to 100 c. c., add 1 c. c. H 2 - SO 4 , boil then add gradually a solution of sodium hypo- sulphite (avoiding a large excess) as long as a black pre- cipitate continues to form ; filter, and wash thoroughly with hot water.* Pp. ( C ) = Cu 2 S, dry, remove the precipitate from the filter, incinerate the filter thoroughly, add the precipitate, and an equal bulk of sulphur, mix thoroughly, cover the crucible, ignite, moderately at first, finishing with a dull red heat; all the sulphur will be burned off in about 5 minutes. Result = CuO, Cu 2 S; a mixture of the oxide and sul- phide. CuO = 79.98 per cent. Cu. and Cu 2 S = 79.87 per cent. Cu. Return the per cent, of Cu. treating the result as Cu 2 S. Filt. (c) = Zn.; add HNO 3 , evaporate to a small bulk, filter to remove the separated sulphur, transfer the fil- trate to a large porcelain evaporating dish, boil, add a solution of NaHCO 3 till strongly alkaline, boil, wash by decantation, and afterwards on the filter with hot water. Pp. (d) = ZnCO 3 , dry, incinerate the filter, add the precipitate and ignite. Result = ZnO. Return the per cent, of Zn. Sox 3. PARIS GREEN. Aceto-arsenite of copper = 3 (CuOAs 2 O 3 ), Cu(C 2 H 3 2 ) 2 . *Fresenius 459, Classen 51. GRAVIMETRIC SEPARATIONS. 37 Weigh out 1 grm., add cold NH 4 OH, and stir till all the green particles have dissolved. If there is a residue, filter through counterpoised filters. Res. (a) = insoluble matter, dry at 100 C. and weigh. Return the per cent. Filt. (a) = Cu. As; add HC1 till nearly neutral, then yellow ammonium sulphide, and digest at a moderate heat for one-half hour, decant the supernatant liquid on a fil- ter, and to the residue add more ammonium sulphide and digest; filter and wash with water, to which a little am- monium sulphide has been added. Pp. (6) = CuS; dry, ignite and weigh. Result = CuO, CiigS. Return the per cent, of Cu. Filt. (b) = As; add dilute HC1, cautiously, to acid reaction; warm, pass H 2 S gas for one half hour; filter, (reject the filtrate) dissolve the precipitate with KHO y filter to remove the free sulphur, then pass into the solu- tion chlorine gas, for one hour, (the solution must be kept alkaline), now acidulate with HC1 (the solution must remain clear), add NH 4 OH in excess, and then magnesia mixture in excess, let it stand 12 hours, filter through tared with filters, wash with a mixture of 1 part NH 4 OH and 3 parts water. Pp. (c) = MgNH 4 AsO 4 + 6H 2 O; dry at 102 to 103 C, and weigh; repeat the drying till constant weight is obtained. Result = (MgNH 4 AsO 4 ) 2 , H 2 O. Return the per cent, of As. Box 4. BAKING POWDER. The value of a powder depends, first, upon the amount of CO 2 , which a given weight will give off when dissolved in water; second, upon the solution thus formed being neutral; third, upon its purity. 38 GRAVIMETRIC SEPARATIONS. Composition of some of the baking powders in common use. No. 3. No. 1. Corn Starch 4 % Bitartrate of Potash. 58 " Bicarbonate of Soda. 38 " Flour 37.5 Tartaric Acid 25 Bicarbonate of Soda 37.5 No. 2. Corn Starch 37 Tartaric Acid 10 Bicarbonate of Soda. 30 Sesqui Carb. Am 6 Alum . . .17 No. 4. Flour 20 Bitartrate of Potash. 51 Tartaric Acid 3 Bicarbonate of Soda. 24 .Carbonate of Am,. . 2 These are known as tartaric acid or cream of tartar powders; the alum in No. 3 is probably used to make the bread white and performs no other part in the powder. There are, besides the foregoing powders, those which have no tartaric acid. First, the alum powders, which should always be rejected. Second, the phosphate powders, which are said to be among the best. The following directions apply only to the tartaric acid or cream of tartar powder, which should always be tested for adulterations, especially alum; and if present it should be estimated. (1) Estimation of Starch or Flour Take 0.5 grm., add cold water and shake till the powder is dissolved, filter through tared niters, dry at 100 C, and weigh. The filtrate after boiling should give a neutral reaction when tested with litmus. If it gives an alkaline reaction, which is often the case, titrate this excess of alkali with -fa H 2 S0 4 , and calculate the excess as NaHCO 3 . (2) Estimation of C0 2 .(a) Use the ordinary car- bonic acid apparatus, and displace the CO 2 with dilute H 2 SO 4 ; this gives the total CO 2 . GRAVIMETRIC SEPARATIONS. 39 (6) Determine the C0 2 which the powder will give off when dissolved in water using the same apparatus; heat the flask to 80 C at the last, and cool before weighing; this gives the available C0 2 . (3) Estimation of Soda and Potash. First test for potash with the flame. Take 1 grin, incinerate thoroughly in a porcelain evaporating dish till the carbon is all burnt off, (the mass must not be fused). Extract the residue with hot water, filter into a flask (the filtrate should not exceed 30 c. c.) If there is no potash present titrate this filtrate with ^ H 2 S0 4 for soda. If potash is present, place the flask containing this filtrate over the lamp, boil, and while boiling add gradually from a burette normal tartaric acid, until the red color of the indicator fails to reappear after boiling two minutes, now add as much more tartaric acid, cool the solution, etc. (See page 21). (4) Estimation of Tartaric Acid. Since this cannot be estimated advantageously by any direct process, we resort to an indirect method by calculation. If the tartaric acid exists in the powder in the form of bitartrate of potash, the following proportion will give the amount of that salt present. KHO ; C 4 H 5 K0 6 : : the per cent of KHO : x. x = the per cent, of bitartrate of potash. If there is no potash present then we may conclude that the tartaric acid exists as such in the powder, and its per cent, may be thus calculated. Deduct from the total NaHO as found by (3), the excess, if any, of NaHO as found by (1); the difference represents the amount of NaHO, neutralized by the tartaric acid. Placing it in the form of a proportion, we have. 2(NaHO) : C 4 H 6 O 6 : : the per cent, of NaHO : y. y = per cent, of tartaric acid. Return the ingredients as found by the foregoing direc- tions as follows: 40 GKAVIMETKIC SEPARATIONS. Starch or Flour per cent. Total Bicarbonate of Soda (NaHC0 3 ) " " Excess of " " " " Bitartrate of Potash (C 4 H 5 KO 6 ) or " " Tartaric Acid (C 4 H 6 O 6 ) " " Also report what if any impurities are present. WATER ANALYSIS. REAGENTS AND APPARATUS. [A .] Reagents for the estimation of nitrogen, present as ammonia (NH S }. (1) Nessler Reagent Take 5 grms. KI, dissolve in 15 c. c. of water, add gradually, a cold saturated solution of mercuric chloride (table reagent), till the mercuric iodide ceases to be dissolved on stirring, and a slight permanent precipitate remains; now add a solution of caustic potash,, made by dissolving 15 grms. of solid caustic in 30 c. c. of water; allow to settle before using. (2) Dilute Solution of Ammonia. Dissolve 3.15 grms. of NH 4 C1 in one litre of water. Take 10 c. c. of this solu- tion and dilute to one litre. .1 c. c. of this solution con- tains .00001 grm. of NH 3 . (3) Dry Sodium Carbonate. Heat about 3 grms. of anhydrous sodium carbonate in a porcelain dish for one hour, at a bright red heat, cool, pulverize and place in a ground stoppered bottle. (4) Apparatus. Four large test tubes, of the same diameter, that will hold 60 c. c. or more. Graduate with a 50 c. c. mark. Also a glass tube with a bulb blown at one end. [J5] Reagent for the estimation of Albumenoid Am- monia. (1) Solution of Potassium Permanganate and Potash is made by dissolving 1. grm. of KMnO 4 , and 25 grms. of solid caustic potash in separate portions of water, mix- ing the solutions and diluting to 125 c. c. ; boil the solu- tion for one-half hour, cool and place in a well stoppered, bottle. [C] Reagents for determining hardness. 42 WATER ANALYSIS. (1) Solution of Calcium Chloride Dissolve 1 grm. of finely powdered marble, or pure carbonate of lime in a slight excess of dilute HC1, and neutralize the excess of acid by ammonia, and dilute to one litre. Each c. c. con- tains .001 grm. CaCO 3 . (2) Soap Solution. Dissolve about 8 grms. of white castile-soap (or any good olive-oil soap) in 600 c. c. of 35 per cent, alcohol, and so dilute it that 13 c. c. will produce a permanent lather in 70c.c.of distilled water which con- tains 12 c. c. of C. 1. It has been found that 70 c. c. of pure water destroy 1 c. c. of standard soap; and since we use 70 c. c. of the water under examination it will destroy 1 c. c. of soap, without any material being present which causes hardness. To compare the solutions proceed as follows: Take 12 c. c. of C. 1, place it in a 200 c. c., flask and add 58 c. c. of pure water (12 + 58 = 70); now run in from a burette the soap solution, 1 c. c. at a time, and shake the flask after each addition, till a lather is produced which will last five minutes. From the result obtained calcu- late the dilution required. Suppose 8 c. c. of the soap solution were used and there are 600 c. c. remaining in the graduated cylinder. We must dilute the 600 c. c. so that, 13 c. c. will be required instead of 8 c. c. The follow- ing proportion will give the amount of 35 per cent, alco- hol that must be added. 8:5: : 600 : x = 375 c. c. to be added or 600 + 375 = 975 c. c. total dilution. [D] Reagents for determining Cl, present as chlorides. (1) Silver Nitrate Dissolve 4.79 grms. of AgNO 3 in one litre of pure water; one c. c. will precipitate .001 grm. Cl. (2) Yellow Potassium Chromate Make a cold satur- ated solution (it must be free from chlorine). COLLECTION OF SAMPLES. The amount to be collected will depend upon the nature of the water and the number of elements to be WATER ANALYSIS. 43 determined; two gallons as a rule will be ample. Care must be exercised in collecting the sample to secure an average. The bottle, in which the sample is to be col- lected, should be first thoroughly cleansed, and then rinsed out with some of the same kind of water as that which is to be analyzed; after filling, it should be closed with a clean cork. Before taking out a sample for any of the following determinations, the bottle should be well shaken, unless otherwise directed. Determination of the Total Solid Residue. Take 100 c. c. and evaporate to dryness in a weighed dish, on a water -bath, then place in an air-bath and heat at 104 C for 30 minutes, cool and weigh. Eesult = total solid residue. A much larger quantity of water will be required in most cases. For the sake of convenience, convert all results as fast as obtained into parts per 1,000. Determination of Chlorine. Take 100 c. c., add a few drops of D. 2, and titrate with D. 1. If good results are not obtained, take 500 c. c., concen- trate by evaporation to about 50 c. c. and then titrate. Both solutions must be neutral; if acid, make neutral by adding some carbonate of soda. Determination of Sulphuric Acid. Take 200 c. c., acidify with HC1, boil, filter, and then precipitate with barium chloride. Determination of Inorganic Constituents. Acidulate one litre with HC1, and evaporate to dry- ness, moisten the residue with HOI and dissolve with water, filter. 44 WATEK ANALYSIS. Res. (a) = SiO 2 ; dry, ignite and weigh. Filt. (a); concentrate by evaporation, add excess of ammonia, boil, filter. Pp. (6) = Fe 2 O 3 A1 2 O 3 and P 2 O 5 . Dry, ignite and weigh. Filt. (6); add excess of ammonium oxalate, boil, let stand six hours, filter. Pp. (c) = calcium oxalate, dry, ignite and weigh. Filt. (c); concentrate, cool, add a solution of Na 2 HPO 4 and NH 4 OH in excess, let stand six hours, filter. Pp. (d) = Mg 2 (NH 4 ) 2 (POJ 2 . Dry, ignite and weigh. Determination of Potash and Soda. These are generally determined jointly. Take 500 c. c. evaporate to dryness, add 0.2 grm. of caustic baryta, and a little distilled water, and boil, filter; to the filtrate add ammonium carbonate, boil and filter; evaporate this filtrate to dryness and ignite moderately in a weighed porcelain crucible; remove the lamp, add solid N"H 4 C1, and again ignite till fumes cease to be given off (use only a moderate heat) cool ard weigh. Kesult = KC1, NaCl, return as Na 2 O. Determination of Hardness. Take 70 c. c. of the sample of water, place it in a 200 c. c. flask, then run in from a burette soap solution, 1 c. c. at a time, shaking the iiask after each addition, till a lather is produced which will last five minutes, and will reappear on shaking. The number of c. c. of soap solution used represents the degrees of hardness; and each degree stands for one grain of CaCO 3 , or its equivalent, in an English gallon. The English gallon hold 70,000 grains. The United States gallon holds 58,318 grains. If the 70 c. c. require more than 16 c. c. of the soap solu- tion, then take 35 c. c. of the water, and add to it 35 c. c. of distilled water, and titrate with the soap solution; the re- sult multiplied by two will give the degrees of hardness. WATER ANALYSIS. 45 Further dilution may be required to reduce the amount of soap solution required below 16 c. c. The reason why this dilution is called for, appears to be that too large a proportion of insoluble lime-salts, in- terferes with the formation of a lather. When the water contains much Magnesium, which is known by the lather having a curdy appearance, the reaction is slow, and the water should be diluted so much, that 70 c. c. will require less than 7 c. c. of the soap solution. Time should be given for the Magnesium salt to form. Determination of Ammonia. Place a well washed litre flask upon a piece of wire gauze, which rests upon the ring of the lamp-stand, and then connect it with a Liebig's condenser. Pour into this flask 500 c. c. of the sample of water, and add to it one grin, of the ignited sodium carbonate, connect the appa- ratus, and distil rapidly, collecting the distillate in the graduated test tubes (A-4). Distil until four tubes have been filled to the 50 c. c. mark, then stop the operation. Now Nesslerise the second tube, thus: add to it 2 c. c. of Kessler reagent and thoroughly mix; if ammonia is pres- ent, it will assume a rich brown color; and the more the ammonia, the deeper the color. Take another test tube, (A-4) place in it 1 c. c. of the dilute NH^Cl (A-2), and make up to 50 c. c. with distilled water, mix thoroughly, add 2 c. c. Nessler reagent and again mix; compare this witn the Nesslerised distillate. If the colors are not the same, the made up tube must be emptied, rinsed, and refilled, in the same order, adding more or less of the dilute NH 4 C1, as it was lighter or darker than the distillate. This operation must be repeated till the colors are the same. The amount of dilute NH 4 C1, added to the made up tube represents the amount of NH 3 in the distillate, the Nesslerising of this second tube, is to find out whether the first tube can be Nesslerised as a whole, or must be divided. If 1 c. c. of the dilute NH 4 C1 has been used, then the first tube cannot be Nesslerised as a whole, for it would give too dark a color. 46 WATER ANALYSIS. Therefore take 10 or 20 c. c. of the first tube, make it up to 50 c. c. with distilled water, mix thoroughly, add 2 c. c. Messier Reagent and again mix; compare with a made up tube as before; the result multiplied by the proper factor will give the total NH 3 in the first tube; add to this one-third, and we obtain the total free ammonia. Thus, 10 c. c. of the first tube gave .00001 grm. NH 8 , multiplied by 5 gives .00005 grm. in the first tube; add to this one-third and we have .000067 grm.NH 3 in the 500 c.c. taken, or .000134 grm. in a litre. * ESTIMATION OF TOTAL NITROGEN OF NITRATES AND NITRITES. Reagents; (To be prepared shortly before required for use). (1) Nessler's Reagent. (2) Solution of NH 4 C1. (3) Saturated Solution H 2 C 2 O 4 , nearly free from NH 3 . It should be tested for NH 3 before using. A slight color when Nesslerized may be disregarded. (4) Zn-Cu couple. Fill a wide mouthed quart bottle with solution of CuSO 4 in H 2 O, containing 1.4 to 1.8 per cent CuS0 4 . Clean several strips of sheet Zinc, four inches by three-fourths of an inch in size, in dilute H 2 SO 4 and rinse carefully with pure H 2 O. Introduce same into the solution of CuSO 4 and close the bottle set aside till the Zn is well coated with Cu. Carefully remove the strips of metal with forceps and wash with successive portions of pure H 2 O, being careful not to break off the coating of Cu. Method. 200 c. c. of the H 2 O under examination are barely acidulated with Reagent, 3 (above) and thoroughly mixed. Divide into two equal portions and place each 100 c. c. in "This method, called the Williams-Blunt method, has been dis- cussed at length, by Dr. A. B. Prescott, in the Pharmaceutical Era for 1887, and the method, as herein given, is taken from that source. WATER ANALYSIS. 47 a wide-mouthed bottle. Into one portion insert one of the prepared Zn-Cu plates. Close both bottles and set aside in an atmosphere free from NH 3 for from 24 to 40 hours. Great care should be taken to rinse all apparatus used in pure, Ammonia free H 2 O. Take from 10 to 50 c.c. from each bottle (if the H 2 has not over % part per million of .Nitrogen of Nitrates and Nitrites, 50 c. c.'s may be taken, but if there be 1 part per million, or over, less of the H 2 O, say 10-20 c. c. may be taken and diluted, with pure H 2 O, up to 50 c. c.) care being taken not to disturb any sediment of precipated oxalates which may be in the bottom. If less than 50 c. c. be taken from each bottle,, the same quantity must be taken from each, and diluted to 50 c. c. with the same ammonia free H 2 O. Treat both portions of H 2 O with Nessler's Eeagent (enough to serve the purpose after the H 2 C 2 4 has been neutralized) and titrate the sample, in which Nitrates and Nitrites have been reduced, against the other sample. The excess found in the reduced portion will be the Nitro- gen of Nitrates and Nitrites. No account being taken of the Ammoniacal Nitrogen, discovered by Nesslerizing the unreduced portion, which is estimated in another ope- ration. Nitrites remain to be tested for which may be done by use of Napthylamine Hydrochloride and Sulphanilic acid. If Nitrites are discovered their Nitrogen is to be estimated and deducted from the amount found by the last operation. The color titration of Nitrites with Nap- thylamine hydrochloride is a valuable method, and but little practice in comparison of known solutions is neces- sary to render the operator comparatively expert. The results of the above determinations should be calculated and reported as (1) Nitrogen of Nitrates, and (2) Nitrogen of Nitrites. DETERMINATION OF ALBUMENOID AMMONIA. From the 500 c. c. of water taken we have distilled oft 48 WATER ANALYSIS. 200 c. c. for the estimation of free Ammonia; in the re- maining 300 c. c. we estimate the " organic " or albumen- old Ammonia, as follows: Take 50 c. c. of Permanganate solution (B-l) and add to it 200 c. c. of pure ammonia-free water; distill till the distillate gives no color with Nessler's Reagent. Then add to this solution, in the retort, the 300 c. c. of the water under examination and distill for albumenoid Ammonia. Collect the whole distillate, of 150-200 c. c., mix thor- oughly, measure and take portions of 10-100 c. c. (accord- ing to the amount of NH 3 ) and Nesslerize. By the above dilution of the KMnO 4 solution it gives up, upon distillation, the small amount of Ammonia which it otherwise would retain and which would of course vitiate the result. Reports. Eesults obtained are generally reported as " parts per million " and also as " grains per gallon." The United States gallon contains, at 60 F., 58,318 grains of distilled water. To convert "grammes per Litre" into "grains per gallon," multiply by 58,318 and divide by 1,000. Eeport "free Ammonia" and "albumenoid Ammonia"; also, "Nitrogen of Nitrates" and "Nitrogen of Nitrites." METHODS OF ESTIMATING THE ORGANIC IM- PURITIES IN WATER WITHOUT GAS APPARATUS. THE OXYGEN PROCESS. Reagents. (a) Standard Solution of Potassium Permanganate. Dissolve 0.395 grms. of potassium permanganate in 1 litre of water. Each c. c. contains 0.0001 grm. of avail- able oxygen. (b) Standard Solution of Sodium Hyposulphite. WATEK ANALYSIS. 49 Dissolve 3.068 grms. of the salt in 1 litre of water. 1 c. c. = 1 c. c. of the permanganate solution. (c) Solution of Potassium Iodide. One part of the pure salt, recrystallized from alcohol, dissolved in ten parts of water. (d) Dilute Sulphuric Acid One part by volume of pure sulphuric acid is mixed with three parts by volume of water, and solution of potassium permanganate added until the whole retains a very faint pink tint, after warm- ing to 80 F for four hours. (e) Starch Indicator, (see page 20). Determination of the Oxygen Absorbed by the Water. Select a half litre glass-stoppered flask and clean thor- oughly with H 2 S0 4 and water. Put 250 c. c. of the water into it, stopper tightly and immerse in a. water or air bath until the temperature rises to 27 C. Now add to it 10 c. c. of the sulphuric acid (Sol. d), and then 10 c. c. of the standard permanganate (Sol. a). Stopper tightly and allow it to remain at 27 C, for 4 hours, remove and add the solution of potassium iodide till the pink color disap- pears, then shake thoroughly and titrate with hyposul- phite solution until the yellow color is nearly distroyed, then add a few drops of starch indicator, and continue the titration till the blue color is just discharged. The c. c. of KMnO 4 taken, less the c. c. of hyposulphite used the c. c. of KMnO 4 reduced. Should the permanganate color fade rapidly during the four hours, other measured quantities must be added from time to time. The permanganate and hyposulphite solutions must be compared often, and a correction factor used if neces- sary in the titration. CONCLUSIONS. The purity of the water is indicated by the amount of Oxygen absorbed from the permanganate by 100,000. parts of H 2 O. The following figures (which must be considered 5 50 WATER ANALYSIS. as of questionable value) have been given in connection with the foregoing process: " Water of great organic purity absorbs 0.05 parts of Oxygen." "Water of medium purity absorbs 0.05 to 0.15 parts of Oxygen." "Water of doubtful purity absorbs 0.15 to 0.2 parts of Oxygen." " Impure water absorbs 0.2 or more." Regarding the foregoing process as a means of definite decision as to the sanitary character of a water, it is now generally conceded that alone it is of no value, but should always be considered as simply an auxiliary estimation, to be considered together with the estimation of saline constituents, free and albumenoid ammonia, Nitrates and Nitrites, etc., etc. In concluding this section concerning Water Analysis it is necessary to state that the interpretation of the results of an analysis of water is a matter of far too ex- tensive a character for the scope of this book, and it will not be attempted, but, with a few of the elementary con- siderations necessary in forming an idea of the character of a water, the subject will be left to the student, as one which requires a vast amount of study and research. In the examination of a water, its source should be known whether from a cistern, well or hydrant; also, the proximity of any possible source of contamination, the geological character of the country and the character of the soil and sub-soil. Un-polluted spring water usually contains less than one part of Chlorine. Sewage generally contains from 10 to 14 parts of Chlorine. The amount of Albumenoid Ammonia is of great im- portance, since it indicates the presence of undecomposed animal or vegetable matter. The free NH 3 , the Nitrates and Nitrites may be con- sidered harmless in themselves; yet, as being products of WATER ANALYSIS. 51 the oxidation of organic matter, they indicate the possi- bility of evil, should the certain conditions of tempera- ture, nitration, etc. (which oxidize the organic matter) be removed or fail to exert their influence. A microscopic examination, both of the water and residue on evaporation, is often employed with profit, and, in some cases, valuable data may be determined from the appearance of the residue after evaporation and its odor upon ignition. SELECT METHODS IN QUANTITATIVE ANALYSIS, PART II. USE OF PLATINUM VESSELS. The following bodies should not be treated in plati- num vessels. 1. The caustic alkalies as well as baryta and strontia. 2. Fusible metallic sulphides, or mixtures of sulph- ides with carbon; especially the alkaline sulphides. 3. Phosphates and carbon, which at a high heat form platinum phosphide. 4. Metals that are easily fused, or metallic oxides that are easily reduced. These form fusible alloys with plati- num. 5. Chlorine, and all mixtures that liberate chlorine, either in the cold or by heat; as fusible mixtures of a metallic chloride and a nitrate, of ammonium sulphate and a chloride. Platinum crucibles may be cleaned by fusing borax or potassium bisulphate in them, and dissolving the fused mass with boiling water. Sometimes they may be cleaned by digesting with dilute HC1. To brighten them scour with sea-sand and water; do not use sharp sand or emery. SELECT METHODS IN QUANTITATIVE ANALYSIS, LIMESTONE. For technical purposes, it is sufficient to determine those constituents which perform the active part in any given operation. The more common constituents of limestone may be determined as follows: Pulverize a few grms., dry at 100 C. Weigh 1 grm. of the dry sample, transfer it to a porcelain dish, cover with a clock-glass, add 20 c. c. of water, then 10 c. c. of HC1, and 2 c. c. of HNO 3 , heat till effervescence ceases, then boil and filter. (For complete separation of the silica evaporate to dryness on the water bath. When perfectly dry, cool, moisten with HC1, add water and heat until dissolved, then filter.*) Res. (a) = Silica and silicates; dry, ignite and weigh; and return as insoluble matter. If it is desired to esti- mate the elements of this insoluble matter, mix the ignited residue with Ammonium Fluoride, cover the cru- cible and ignite till fumes cease to be given off, repeat this operation till constant weight is obtained. The difference between the first and last weight is the silica. Transfer the residue from the crucible to a beaker and dissolve in strong HC1, and add the solution to filtrate (a). Filt. (a); add 10 c. c. HC1, then ammonia to slight alkaline reaction, and boil till excess of ammonia is ex- pelled, filter. Pp. (6) = iron, alumina, and phosphoric acid. If this precipitate is small, it may either be rejected or returned * Classen 32. 56 LIMESTONE. as a whole; if large, separate, and estimate the per cent, of iron and alumina. Filt. (6), add ammonium oxalatein excess, (there must be sufficient to form an oxalate of all the magnesia pres- ent), heat just to boiling, and then allow it to stand in a warm place for six hours; filter by decantation, wash once with water in the same way; now dissolve the pre- cipitate in dilute HOI; add a little ammonium oxalate, and then ammonia in excess; boil, filter and wash by decantation. The re-precipitation is to separate the mag- nesia which is precipitated with the lime in the first operation. Pp. (c) = calcium oxalate. Filt. (c), (The united filtrates); concentrate by evap- oration, (adding HC1 if necessary, to prevent the forma- tion of a precipitate), cool, add ammonia in excess, then sodium ammonium phosphate, and allow to stand six hours in a cool place; filter and wash with water con- taining ammonia. Pp. (d) = Mg 2 (NH 4 ) 2 (P0 4 ) 2 . ESTIMATION OF C0 2 .* Fuse 2 grins, of vitrified borax in a platinum crucible, cool in a desiccator, and weigh; add about 0.5 grm. of the well dried limestone and weigh; then apply heat and gradually increase to redness and continue the heat till the mass is in a state of quiet fusion, cool and weigh. The loss in weight is the CO 2 . Volumetric Estimation of Calcium.t Weigh 1 grm. and dissolve in dilute aqua regia, cool add a slight excess of ammonia, then a large excess of ammonium oxalate; heat just to boiling and then allow it to stand till the precipitate has subsided; filter and wash thoroughly by decantation, till the ammonium oxalate * Fresenius 336. t Sutton 133. IKON QBE. 57 has been removed. Place beneath the funnel a 250 c. c. flask, pierce the filter, wash the precipitate into the flask, first with water, then with dilute sulphuric acid or HC1; then add to the contents of the flask enough dilute sul- phuric acid to dissolve (or decompose) the calcium oxalate, and dilute to 250 c. c. Titrate portions of this solution with ^ KMnO 4 . The T \ factor of CaO = .0028. Note. If there is much magnesia present, the calcium oxalate should be dissolved in dilute HC1 and re-precipi- tated. IRON ORE. Estimation of Iron, Silica and Sulphur. Weigh from 2 to 5 grms. of the dry ore, mix it thor- oughly in a clock-glass with five times its weight of the fusing mixture. Select a large platinum crucible, and fuse in it 2 grms. of the fusing mixture, when well fused lower the crucible into the flame of the Bunsen burner so that the bottom becomes cool and the heat is upon the sides; remove the lamp, introduce into the crucible one- third of the ore mixture, cover the crucible and replace the burner, and continue the heat till the mass has become quiet; now introduce another third and treat it in the same way; and finally the last third; continue the heat till the mass has become quiet, then apply the heat to the bottom of the crucible, and finally apply the heat of the blast-lamp until reduced to quiet fusion.* Sometimes a semi-fused mass results which cannot be made fluid by the strongest heat. Eemove the lamp and incline the crucible as much as possible, and rotate it as the mass solidifies; while still hot plunge it side wise into a beaker of cold water, remove it, and, after a few seconds plunge *Fresenius383. 58 IRON QBE. again; repeat this three or four times. Then place the crucible on its side in the beaker, and heat till the mass separates, remove the crucible, and continue the heat till the mass is disintegrated; filter and wash with hot water by decantation. Res. (a) contains the iron, alumina, etc. Dissolve in HC1, upon a water bath ; if it fails to dissolve, filter and re-fuse the insoluble portion; when all is dissolved except the silica, evaporate to dryness, moisten with HC1 and take up with water; filter. Res. (b) = part of the silica. Filt. (6), dilute to a given number of c. c. and esti- mate in one portion the iron and alumina together, and in another the iron by titration. Note. An alcohol lamp should be used if possible for the fusion. If gas is used, it should be passed through a solution of potash to remove the sulphur before burning. Filt. (a). Add HC1 cautiously till acid, evaporate to dryness, heat on an iron plate to 110 C; moisten the res- idue with HC1, add water and boil; filter. Res. (c) = silica. Dry and ignite residues (c) and (b) together. Filt. (c). Boil, and add a boiling solution of barium chloride; filter after standing over night, and determine the sulphur in the precipitate. v Titration of the iron in filt. (b). Take a portion of the filtrate, add HC1 till strongly acid, boil, and run into it from a burette stannous chlo- ride, very cautiously, till the Fe 2 O 3 is reduced to FeO, and the SnCl 2 is in slight excess. (When the reduction is com- plete the solution will be colorless); now add 5 c. c. of a saturated solutiod of HgCl 2 , and titrate the iron with & K 2 Cr 2 O 7 . For the estimation of manganese, lime, and magnesia, dissolve about 1 grm. of the ore, according to the direc- tions given below for the estimation of phosphorus, sep- .arate the iron and alumina from the other bases as basic IRON QBE. 59 acetates,* and the manganese with bromine or ammonium sulphide.! Estimation of Phosphorus. Weigh 5 grms. of the fine dry ore and digest at 100 C., with strong HC1, till all, or nearly all is dissolved; then boii for 15 minutes, filter and wash slightly. Res. (a). Place the filter with its residue in a platinum crucible, incinerate thoroughly; cool, add dry jN"a 2 CO 3 and fuse; dissolve in dilute HC1, and add this solution with its residual silica to filtrate (a). Filt. (a). Evaporate to dryness, and heat on an iron plate at 110 C., till it no longer emits an odor of HC1; cool slightly, add strong HC1 and boil till the iron is dissolved ; evaporate as low as possible without formation of oxide of iron, then add 30 c. c. of HNO 3 (1.42 sp. gr.) and evap- orate to a sirupy consistence, then add more HN0 3 and repeat till HC1 is driven off; now add an equal volume of water, cool and filter. Filt. (6). Precipitate the phosphoric acid according to directions given on page (60). Res. (a) and Filt. (a) may be worked separately and if no phosphorus is found in res. (a) it may be neglected in the analysis of ore from that mine. If phosphorus is found in res. (a), the amount may be determined in several samples of ore, and then neglected in other samples from that mine; the amount thus found being added to that obtained from filt. (a), in all subsequent determinations. Estimation of Iron. Place 0.5 grms.J of the very fine dry ore in a 4 oz. .Erlenrneyer flask, add 15 c. c. of strong HC1, mix thor- * Fresenius 429. t Fresenius 430 203. Classen 73. \ Or, better, weigh exactly 0.560 grms. ore, dissolve in 15-20 c. c. strong HC1, (in a^small beaker which has no lip and which should be closely covered with a watch-glass) letting substance digest for some 60 IKON ORE. oughly, place the flask on an iron plate and heat at from 80 to 90 C., till dissolved; now add 10 c. c. of water and run in stannous chloride solution, one drop at a time, shaking after each addition, till the iron solution is colorless, now transfer to a large flask and dilute to about 400 c. c. with water, then add 10 c. c. of a saturated solu- tion of HgCl 2 , which should produce a silky white pre- cipitate. Titrate this solution with & K 2 Cr 2 O 7 . Or add to this solution 10 c. c. of a cold saturated solution of manganous sulphate and titrate with ^ KMnO 4 ; the end reaction is reached when the pink color first permeates the whole solution. In titrating with ft KMnO 4 it is better to use only 0.2 grms. of ore. Estimation of Sulphur. First Method* Place 1 grm. of the fine dry ore in a porcelain dish, add 0.5 grms. of pulverized KC10 3 , pour over it 50 c. c. HNO 3 (1.42 sp. gr.) and cover with a funnel or clock-glass; now place it over the lamp and raise the heat gradually and bring to a boil and boil for fifteen minutes, adding from time to time crystals of KC1O 3 ; now remove the cover and evaporate to a small bulk, then add strong HC1 and evaporate to dryness on a water bath.. Moisten the residue with strong HC1, add water, boil, thf-n filter and wash thoroughly; nearly neutralize the filtrate with ammonia, boil, add 5 c. c. of the tartaric acid solu- tion, and sufficient BaCl 2 solution to precipitate the sul- phur, boil, then allow it to stand all night, filter, wash thoroughly with hot water, then with a dilute solution of ammonium acetate to dissolve any barium nitrate which may adhere to the sulphate. time at a slight heat and finishing by boiling. To the hot, concentrated solution add solution of SnCl 2 to exact decolorization, wash into a 400 c. c. beaker, add 15-30 c. c. of solution of HgCl 2 , dilute largely with H 2 O and titrate with ft K 2 Cr 2 O 7 . Each c. c. of K 2 Cr 2 O 7 = 1 per cent. (F. C. S.) * Crooks 480. COAL. 61 Second Method. Place 1 grm. of the fine dry ore in a 4 oz. Erlenmeyer flask, moisten thoroughly with the smallest quantity of water possible, then add about 3 c. c. of bromine and shake thoroughly; now heat at 80 C., for 5 minutes, then add 15 c. c. of strong HC1 and continue the heat 15 minutes longer, transfer to a porcelain dish and evaporate to dryness on a water bath, etc. (see page 52). Estimation of Manganese. Take 5 grms. of the ore, dissolve in strong HC1, cool, add H 2 S0 4 in slight excess, evaporate till HC1 is all ex- pelled, cool, add water, heat till dissolved, transfer to a 500 c. c. flask; dilute largely, add zinc oxide in excess, dilute to the mark, shake thoroughly, filter off a portion through a ribbed filter; boil a measured portion of this nitrate, and titrate with ^ KMnO 4 , (see page 70). COAL. Proximate Analysis of Coal. Pulverize a sample of the coal in a rough, porcelain mortar. Determination of Moisture. Take 1 grm. place it in a covered crucible, and heat in an air bath at 115 C. for one 'hour, cool and weigh. Loss = Moisture. Determination of Volatile Matter. Take 1 grm. of the undried coal, place it in a platinum crucible, and cover tightly; heat it for three and a half minutes over a Bun- sen burner, and then without cooling, for the same length of time, over a blast lamp, cool and weigh. Loss, less the moisture = volatile matter and one-half of the sulphur present as sulphide of iron. Determination of Fixed Carbon Incinerate the res- idue from the last operation until the carbon is burnt off 62 COAL. and a constant weight is obtained. Loss fixed carbon and one-half of the sulphur present as sulphide of iron. The last weight is the ash. Estimation of the Total Sulphur. Reagent. Mix thoroughly 4 grms. of calcined magne- sia and 2 grms. of anhydrous sodium carbonate, and deter- mine the sulphur in the mixture. Weigh 1 grm. of the very fine coal and mix it thoroughly with 2 grms. of the reagent in a porcelain crucible, which should not be more than two-thirds full. Place the crucible in an inclined position on a triangle, and heat very gradually, with an alcohol lamp, increasing the heat until the bottom is dull red. (The heat must not, in any stage of the operation, be so high as to fuse the mass). Stir the mixture with a platinum wire to hasten the combustion, which requires about one hour. When the carbon is all oxidised, remove the lamp and allow the crucible to stand until perfectly cold, then add 1 gram of pulverized ammonium nitrate, mix thoroughly and heat for 5 or 10 minutes at a red heat. Cool, dissolve in water and dilute to about 150 c. c.; acidulate with HC1, warm, and filter. Boil the filtrate and add a hot solution of BaCl 2 ; allow it to stand one hour, then filter, etc. Estimation of Sulphur, present as calcium sulphate. Take 4 grms. of the coal, add 6 grms. sodium carbo- nate (which must be free from sulphur), then add water and boil for two hours, replacing the evaporated water. Filter, acidulate the filtrate and precipitate the sulphuric acid in the usual way. Phosphoric Acid. If present in the coal, it will be found in the ash, and should be estimated in the usual manner. BLAST FURNACE SLAG. 63 BLAST FURNACE SLAG. The slag may contain FeO, Fe 2 O 6 , FeS, MnO, A1 2 3 , CuO, PbO, ZnO, CaO, MgO, K 2 O, Na 2 0, SiO 2 , TiO 2 , SO 3 P 2 O 5 , CaS. Scheme for Analysis. The slag when not soluble in HC1, is decomposed by fusion. (See directions for fusing iron ore for the estima- tion of iron, silica, and sulphur, page 47). Res. (a) silica and titanic acid. (It will contain most of the TiO 2 , if too large an amount of HC1 has not been used in taking up the residue.) Filt. (a) = all the bases acids (also some Si0 2 and Ti0 2 ). Reduce the ferric to ferrous iron by sulphurous acid and then pass through the solution H 2 S gas, and filter. Pp. (6) - PbS, CuS, As 2 S 3 . (If there is any arsenic in the slag, it will, as a rule, be volatilized in preparing the solution and will not appear at this point). The copper and lead can best be separated by sulphuric acid and alcohol. Filt. (6). Add HC1, boil, then add a few crystals of KC10 3 and continue the boiling until the odor of Cl has disappeared; now dilute the solution to 600 or 800 c. c. and precipitate the iron and alumina as basic acetates and filter. Pp. (c) = Fe 2 3 , A1 2 O 3 , SiO 2 Ti0 2 , P 2 O 5 . Pierce the filter and wash the precipitate into a beaker, and dissolve in sulphuric acid; nearly neutralize with ^H 4 OH, dilute if necessary, pass H 2 S gas till the Fe,O 3 is reduced to FeO, boil for some time, replacing the evaporated water; filter. Pp. (d) = Si0 2 , TiO 2 . Add this prcipitate to residue (a). Filt. (d). Add HNO 3 , and boil till the iron is oxidized,, filter if necessary, dilute to a given number of c. c. and estimate the iron and alumina in one portion, and the iron in another portion by titration. 64 BLAST FUBNACE SLAG. Fill. (c). Concentrate to 200 c. c. Add acetic acid and pass H 2 S gas; filter. Pp. (e) = ZnS. Dissolve in HC1; filter out the sulphur, and precipitate the zinc with sodium bi-carbonate in a porcelain dish. Filt. (e). Concentrate to 200 c. c. by boiling, filter if necessary and precipitate the manganese with bromine, Pp. (/) = manganese. Filt. (/). Add ammonia till alkaline, boil and add ammonium oxalate, filter. Pp. (g) = CaC 8 4 . Filt. (4, and the rose color will not be obtained till long after the ferrous iron has all been oxidized, if at all. 90 INSOLUBLE SILICATES. posed. This will take from 5 to 10 minutes. Now place the crucible in the upright position, and apply a bright red heat for from 40 to 60 minutes. Cool the crucible; when cold the contents will be found to be a semi-fused mass; place in an evaporating dish, add water, and heat till the mass slakes; remove the crucible, washing it thor- oughly with water, and digest the mass one hour longer or till completely disintegrated. Filter and wash well. The nitrate contains all the alkalies of the mineral, and some calcium chloride and caustic lime; add some ammo- nium carbonate, and concentrate to about 50 c. c.; then add a little more ammonium carbonate and a few drops of ammonia, and filter; to this filtrate add a few drops of ammonium carbonate, and concentrate; if a precipitate is formed, filter it off and repeat the last operation till a precipitate ceases to be formed; now evaporate to dryness in a weighed platinum dish on a water bath ; when dry, heat, at first moderately, over the Bunsen burner until the KH 4 C1 is driven off, and then gradually increase the heat to faint redness; cool, and weigh. This weight is the chlorides of the alkalies, or the weight of mixed chlorides. Indirect Determination of the Potash and Soda in the Mixed Chlorides. Dissolve the mixed chlorides in water and determine by titration with ft AgNO 3 the total chlorine: Then by means of the following formula? the ^quantities of NaCl and KC1 are determined. TV = weight of mixed chloride. C = weight of chlorine. Nad = C X 7.6311 W X 3.6288. KC1 = W X 4.6288 C X 7.6311. SUPERPHOSPHATES. 91 SUPERPHOSPHATES. Method for Determining Phosphoric Acid and Moisture. PREPARATION OF REAGENTS. (1) To prepare ammonium citrate solution. Mix 370 grams of commercial citric acid with 1,500 cubic centime- ters of water; nearly neutralize with crushed commercial carbonate of ammonia; heat to expel the carbonic acid; cool; add ammonia until exactly neutral (testing by sat- urated alcoholic solution of coralline) and bring to volume of two litres. Test the gravity, which should be 1.09 at 20, before using. (2) To prepare molybdic solution. Dissolve 100 grams of molybdic acid in 400 grams or 417 cubic centimeters of ammonic of specific gravity 0.96, and pour the solution thus obtained into 1,500 grams or 1,250 cubic centimeters of nitric acid of specific gravity 1.20. Keep the mixture in a warm place for several days, or until a portion heated to 40 C. deposits no yellow precipitate of ammonium phospho-molybdate. Decant the solution from any sedi- ment, and preserve in glass-stoppered vessels. (3) To prepare ammonium nitrate solution. Dissolve 200 grams of commercial ammonium nitrate in water and bring to a volume of two liters. (4) To prepare magnesia mixture. Dissolve 22 grams of recently-ignited calcined magnesia in dilute hydro- chloric acid, avoiding excess of the latter. Add a little calcined magnesia in excess, and boil a few minutes to precipitate iron, alumina, and phosphoric acid, filter, add 280 grams of ammonium chloride, 700 cubic centimeters of ammonia of specific gravity 0.96, and water enough to make the volume of two liters. Instead of the solution of 22 grams of calcined magnesia 110 grams of crys- tallized magnesium chloride (MgCl 2 , 6H 2 O) may be used. (5) Dilute ammonia for toashingOne volume am- monia of specific gravity 0.96 mixed with three volumes 92 SUPERPHOSPHATES. of water, or usually 1 volume of concentrated ammonia with 6 volumes of water. (1) Preparation of sample. The sample should be well intermixed and properly prepared, so that separate portions shall accurately represent the substance under examination, without loss or gain of moisture. (2) Determination of moisture. (a) In potash salts, nitrate of soda, and sulphate of ammonia heat 1 to 5 grams at 130 C. till the weight is constant, and reckon water from the loss. (6) In all other fertilizers heat 2 grams, or if the sample is too coarse to secure uniform lots of 2 grams each, 5 grams for five hours at 100 in a steam bath. (3) Water-soluble phosphoric acid. Bring 2 grams on a filter, add a little water, let is run out before adding more water, and repeat this treatment cautiously until no phosphate is likely to precipitate in the filter. If the wash- ings show turbidity after passing the filter clear up with acid. When the substance is nearly washed in this man- ner it is transferred to a mortar and rubbed with a rubber tipped pestle to homogeneous paste (but not further pul- verized), then returned to the filter and washed with water until the filtrate measures not less than 250 cubic centimeters. Mix the washings. Take an aliquot (usually corresponding to y% gram of the substance) and determine phosphoric acid, as under total phosphoric acid. (4) Citrate-insoluble phosphoric acid. Wash the res- idue of the treatment with water into a 150 cubic centi- meter flask with 100 cubic centimeters of strictly neutral ammonium citrate solution of 1.09 density, shred and add the filter paper, cork the flask securely, place in a water bath with constant temperature of 65 C., and digest for thirty minutes at this temperature with frequent shak- ing, filter the warm solution quickly and wash with water of ordinary temperature. Transfer the filter and its con- tents to a capsule, ignite until the organic matter is de- stroyed, treat with 10-to 15 cubic centimeters of concen- trated hydrochoric acid, digest over a low flame until the phosphate is dissolved, dilute to 200 cubic centimeters, SUPERPHOSPHATES. 93 mix, pass through a dry filter, take an aliquot and deter- mine phosphoric acid as under total. In case a determination of citrate-insoluble phosphoric acid is required in non-acidulated goods, it is to be made by treating 2 grams of the phosphatic material without previous washing with water, precisely in the way above described, except that in case the substance contains much animal matter (bone, fish, &c.) the residue insol- uble in ammonium citrate is to be digested with HC1 and KC1O 3 , as described below. (5) Total phosphoric acid. Weigh 2 grams into a flask or beaker, add 30 cubic centimeters concentrated hydro- chloric acid, heat and add cautiously and in small quan- tities at a time about 0.5 gram finely-powdered potassium chlorate. Digest at a gentle heat until all phosphates are dissolved and all organic matter destroyed, dilute to 200 cubic centimeters; mix; pass through a dry filter; take 50 cubic centimeters of filtrate; neutralize with ammonia; for every decigram of P 2 O 5 that is present, add 50 cubic centimeters of molybdic solution. Digest at about 65 C. for one hour filter and wash with ammonium nitrate solu- tion. (Test the filtrate by renewed digestion and addition of more molybdic solution.) Dissolve the precipitate on the filter with ammonia and hot water, and wash into a beaker to a bulk of not more than 100 cubic centimeters. Nearly neutralize with hydrochloric acid, cool, and add magnesia mixture from a burette; add slowly (one drop per second), stirring vigorously. After 15 minutes add 30 cubic cen- timeters of ammonia solution of density 0.95. Let stand several hours (two hours is usually enough). Filter; wash with dilute ammonia; ignite intensely for 10 min- utes and weigh. (6) Citrate-soluble phosphoric acid. The sum of the water-soluble and citrate-insoluble subtracted from the total gives the citrate-soluble. 94 ANALYSIS OF NICKEL SPEISS. ANALYSIS OF NICKEL SPEISS. Digest a weighed portion with strong HC1, at 60-70 C., for some time, afterward bringing to a boil. Evapo- rate to dryness, take up with HC1 + H 2 O and filter. Or, complete solution may be obtained by digesting the sam- ple in the above manner with Br and afterward taking up with HC1 and H 2 O. (This method of solution in Bromine is of great value with many Sulphides, especially where the S is to be estimated.) Res. (a) = SiO 2 . Filt. (a). Heat to 70 C. Pass H 2 S gas through the solution 1^ hour, and filter. Res. (b) = Sulphides of Cu, As, Sb etc. Filt. (6). Boil. Oxidize H 2 S with KC1O 3 , and expel excess of Cl by further boiling. Cool and precipitate Fe 2 O 3 as basic acetate. Filler. Res. (c) = Iron, etc. Filt.(c\ Concentrate to 200 c. c. Cool. Acidify with HC1 and add water solution of freshly prepared Potas- sium xanthate. Filter, and wash thoroughly with water. Res. (d) -= Ni, Co, and Zn as xanthates. Filt.(d). Contains Mn if present. Wash Res. (d} on filter with dilute NH 4 OH. Res. (e) = Cobalt xanthate. Dissolve this residue in strong HNO 3 . Evaporate nearly to dryness, and add more HNO 3 + H 2 SO and evaporate again. The solution should be concentrated. Add H 2 C 2 4 + excess of C 2 H 6 O and boil, replacing the C 2 H 6 O as it evaporates. Filter through sand and wash with C 2 H 6 O. Wash the sand and Cobalt Oxalate into a flask and. acidify with a few drops of H 2 SO 4 . The red color may be neutralized with a solution of Nickel Sul- phate, after which titrate the oxalic acid with ^ KMnO 4 . Filt. (e). Contains Nickel (and Zinc if present). If Zn be present, the solution may be acidified with Citric Acid and treated with H 2 S gas, when perfectly cold. If much Zn is present the gas should be passed at REAGENTS. 95 intervals, for five minutes at a time, so as to avoid pre- cipitation of Ni. Filter off ZnS and evaporate the filtrate to small bulk. Evaporate almost to dryness with HNO 3 (cone.), and repeat with addition to H 2 SO 4 . To the concentrated solu- tion add Oxalic Acid and further concentrate by boiling. Add excess of C 2 H 6 O and digest ^ hour, replacing the C 2 H 6 O. Filter as usual. Wash thoroughly with C 8 H 6 O and dissolve on filter with NH 4 OH. Acidify with H 8 SO 4 , neutralize the green color with solution of Cobalt Sul- phate and titrate the H 2 C 2 O 4 with ft KMn0 4 . From the amount of H 2 C 2 4 calculate the Nickel. REAGENTS. Fusing Mixture. 2 parts NaHCO 3 . 2 parts K 2 CO 3 . 1 part KN0 3 . Pul- verize very fine, and thoroughly mix, ( or 2 parts anhy- drous Na 2 CO 3 and one part KNO 3 ). Test the mixtures for sulphur, and if present determine the amount. Magnesia Mixture. No. 1. MgCl 2 101.5 grms. NH 4 C1 200. " NH 4 OH 400. c. c. Water to make one litre. _ ( 0.0355 grm. P 2 O 5 . No. 2. MgS0 4 100. grms. NH 4 C1 200. " NH 4 OH... 400. c. c. Water ...800. " 1 c. c. = (about) 0.01 grm. P. 1 0.0154 P. Stannous Chloride. 50 grms. of the crystallized salt, dissolved in 500 c. c. of one-half strength HC1. This solution soon deterior- ates, hence should not be made up in large quantities. 96 KEAGENT8. Mercuric Chloride. A saturated solution; 60 grms. per litre. Fused KHSO 4 . Heat some of the moist salt in a platinum dish or cru- cible to quiet fusion, and pour it on a porcelain slab. When cold, pulverize and place in a salt mouth bottle. Molybdate Solution. HTo.1. Take 3 grms. of ammonium molybdate, add 2 c. c. NH 4 OH and triturate in a mortar; then add 20 c. c. of water (should dissolve); now pour this solution slowly into 20 c. c. of HNO 3 (1.20 sp. gr.), keeping it cold. No. 2. (a) Dissolve 100 grms. of MoO 3 in a mixture of 300 c. c. of strong NH 4 OH and 100 c. c. of water. (6) 1250 c. c. of HN0 3 (1.20 sp. gr.). Pour a little of (6) into (a), then all of (a) into (6) rapidly. These solutions should staod several days before use. Acid Solution Ammonium Nitrate. Water 1 litre. tfH 4 $rO 3 100 grms. HNO 3 (1.40 sp. gr.) 15 c. c. Purified Nitric Acid (1.4O sp. gr.) Must be free from nitrous acid. If the bottle contain- ing the acid has red fumes, blow air through the acid until the red fumes disappear, and then add 5 per cent, of water and place the bottle in a dark, cool place. Nitric Acid (1.2O sp. gr.) Add an equal volume of water to the 1.40 sp. gr. acid. It must be free from HC1 and Cl. REAGENTS. 97 Hydrochloric Acid. Must be free from chlorine. If chlorine is present add strips of copper, let stand until it will not give a test for Cl, and then distil. Tartaric Acid. Tartaric Acid 40 grms. Water 200 c. c. Solution BaCl 2 10 c. c. Boil the solution, then allow it to stand till the precip- itate has completely subsided, and decant off the clear liquid for use. Purified Asbestos. Place a quantity of good, fibrous asbestos in a beaker, add some of the CrO 3 solution, then enough strong H 2 S0 4 to thoroughly saturate, and heat for some time; pour the mass into a funnel and wash first with water acidulated with H 2 S0 4 , then with pure water, until the Cr 2 O 3 and H 2 SO 4 are removed; dry. Oxide of Zinc Paste. Fill a large sand or clay crucible with commercial oxide of zinc, cover and heat in a furnace at a bright red heat for some time, cool, and triturate with water to form a thin paste. It should not reduce KMnO 4 . Solution of Zinc Sulphate.' Dissolve 50 grms. of ZnSO 4 in water and dilute to 100 c.c.; add to this KMn0 4 solution until a faint pink color is produced; then add some oxide of zinc paste and shake thoroughly; allow it to subside, then filter or de- cant off the clear solution for use. Pry, Granular Calcium Chloride Free From Calcium Oxide. Take crystallized calcium chloride in a porcelain dish and heat very carefully (not above 200 C.) till fused, then stir constantly until granulated; now transfer the 8 98 REAGENTS. dish to an air bath and heat at 200 C. till perfectly dry. Keep in well stoppered bottles. After filling the U-tubes pass dry C0 2 for one hour, then dry air until the C0 3 has been removed. Double Chloride of Copper and Ammonium. No. 1. CuCl 2 , 2H 2 O 340 grms. NH 4 C1 214 " Water 1850 c. c. When dissolved add enough NH 4 OH to form a slight precipitate, allow this to subside and use only the clear solution. 50 c. c. of this solution will dissolve 1 grm. of steel or iron. No. 2. Make a saturated solution of the double chloride of copper and ammonium (2NH 4 C1, CuCl 2 + 2H a O), add to it very dilute ammonia till a faint precipitate is produced, allow it to stand till the precipitate has subsided, then decant or filter off the clear solution. Solution of CrO 3 and H 2 SO 4 . Take 16 grms. CrO s and dissolve in 100 c. c. of water in a porcelain dish, add to this 260 c. c. of strong H 2 SO 4 . If on stirring, this fails to dissolve the precipitate which is first forme'd, add more H 2 SO 4 till it is dissolved, then heat to incipient ebulliton. When cold it is ready for use. It should not be prepared long before-hand. 1 grm. of iron will require 30 c. c. of this solution. 90 c. c. will oxidize the carbon in 3 grms. of ordinary steel; the amount must be increased with the per cent, of carbon. Anhydrous Copper Sulphate. Take small pieces of pumice stone, soak them in a saturated solution of copper sulphate, and then heat them in an air bath for several hours at 250 C. Cool and keep in well stoppered bottles. REAGENTS. 99 Standard Copper Sulphate. Dissolve 3.95 grm. of pure CuSO 4 , 5H 2 O in water, add a few drops of H 2 SO 4 , and dilute to one litre. 1 c. c. will contain 0.001 grm. Cu. Standard Potassium Cyanide. Dissolve 5 grms. of Potassium Cyanide in 300 c.c. of water, and titrate it so that 1 c. c. will be equal to 1 c. c. of the copper solution. Mode of titrating. Take 5 c. c. of the standard copper solution, add KH 4 OH till the precipitate first formed is dissolved and the solution is deep blue (avoid a large ex- cess, of NH 4 OH); now run into it (cold) from a burette potassium cyanide until the blue color of the copper solution has disappeared. When the reaction is complete the solution will have a slight yellow tinge. The cyanide solution loses strength by standing and must be compared often. Standard Solution of Zinc Chloride. Take 10 grms. Zn, dissolve in HC1, neutralize with NH 4 OH, then add 15 c.c. HC1 and 30 grins. NH 4 C1, and dilute to one litre. Standard Potassium Ferrocyanide. Take 43.2 grms. of the salt, dissolve in water and dilute to one litre. This should correspond volume for volume with the zinc solution; but the solutions should always be compared; for this purpose take 10 c.c. of the zinc solution, dilute to about 50 c. c., heat nearly to boil- ing, add a few drops of Uranium Acetate solution, then run in from a burette the Potassium Ferrocyanide solu- tion, one-half c.c. at a time, shaking violently after each addition, until the precipitate appears flesh colored; or place a few drops of Uranium Acetate on a porcelain slab and add a drop of the solution with a glass rod, from time to time, till it gives a flesh color. While the 100 REAGENTS. zinc is in excess the precipitate is flocculent and subsides rapidly, but when the zinc is nearly all precipitated, the precipitate becomes fine and subsides very slowly, and a drop or two will produce the flesh color. Potassium Xanthate. Dissolve some caustic potash in absolute alcohol, filter if necessary, and add to the filtrate a large excess of car- bon disulphide; a crystalline mass will soon form, which is brought on a filter and quickly washed with ether, and dried over sulphuric acid and paraffin. When dry, place in well corked bottles, and dissolve in water only the re- quired amount when need for use, for the solution soon deteriorates. Zinc Amalgam. Place a quantity of granulated zinc in a dish, cover with mercury, and add a very dilute solution of sulphuric acid, and stir till action ceases; then place in a funnel to drain off the excess of mercury. Battery Solution. For a Bunsen element. For the porous cell use a sat- urated solution of K 2 Cr 2 O 7 to which has been added one- fifth its volume of H 8 SO 4 . For the outer cell use a solu- tion of 1 part H 2 S0 4 . For the outer cell use a solution of 1 part H 2 S0 4 and nine parts water. i- -sc: i -if- 16Mar'53RL DEC 9 1954 LO IBW56RE J956 REC'D JUL 26 1957 21-100-7,-52(A252 8s i6)476 below.