Vol. 18,No. 6
INDUSTRIAL AND ENGINEERING CHEMISTRY
636
Recommended Specifications for Analytical Reagent Chemicals Part I Acetic Anhydride, Acetone, Glacial Acetic Acid, Hydrofluoric Acid, Perchloric Acid, Aluminum and Potassium Sulfate, Ammonium Acetate, Ammonium Carbonate, Ammonium Chloride, Ammonium Persulfate, Ammonium Sulfate, Amyl Alcohol By W. D. Collins, H. V. Farr, J o s e p h Rosin, G. C. Spencer, and Edward Wichers COMMITTEE O N GUARANTEED REAGENTS, AMERICAN CHEMICALSOCIETY
T
HE specifications given below are intended t o serve for re-
agents to be used in careful analytical work. The limits and tests are based on published work, on the experience of members of the committee in the examination of reagent chemicals on the market, and on studies of the tests made by members of the committee as the various items were considered. It is not intended that any limit or method of examination shall be recommended except after independent testing by several members of the committee. Suggestions for improvement of the specifications will be welcomed by the committee. The requirements specified are of two kinds. Some, like the strength of acids, are absolute requirements, regardless of the method of testing; others are merely that the chemical shall pass the test given, and the suggested limit may show only approximately the quantity of the impurity in question. I n all the directions the acids and ammonium hydroxide referred to are of full strength unless dilution is specified; "water" means distilled water of a grade suitable for the test described; reagents used in making the tests are supposed to be of the grade recommended below or in the previous publication2 from the committee. A time of 5 minutes is t o be allowed for the appearance of precipitates and before observation of color reactions, unless some other time is specified. Corrections for four of the specifications published* in 1925 are given a t the end of P a r t 11. Acetic Anhydride REQUIREMENTS Assay-Not less than 90 per cent (CHaC0)20. Nonvolatile Matter-Not more than 0.003 per cent. Chloride ((21)-Not more than 0.0005 per cent. Sulfate (Sod-Not more than 0.0005 per cent. Phosphate (Pod-Not more than 0.001 per cent. Substances Reducing Permanganate-To pass test. Heavy Metals-To pass test (limit about 0.0005 per cent lead, about 0.001 per cent iron).
TESTS Blank tests must he made on water and all reagents used in the methods unless the directions provide for elimination of errors due t o impurities. Solutions of the sample must be filtered for tests in which insoluble material would interfere. Assay-Weigh about 2 grams in a 200- or 250-cc. glass-stoppered Erlenmeyer flask, cool in ice, add 5 cc. of freshly distilled aniline, immediately stopper, shake vigorously, a n d allow t o stand at room temperature for half a n hour. Add 50 cc. of ice cold water, pouring i t in so a s t o rinse down the sides of the flask; mix well and titrate with normal alkali, using 3 drops of phenolphthalein indicator. The titration should be carried to a point where the red color persists after standing for 10 minutes. I n a second flask weigh about 2 grams of the sample, a d d 50 cc. of water, allow to stand for half an hour, and titrate with normal alkali to the same end point with phenolphthalein indicator. Calculate the number of cubic centimeters of alkali used in each of the titrations to the basis of 1 gram of the sample. The difference between the two calculated titrations multiplied by 2 is the number of cubic centimeters of normal alkali equivalent to the anhydride in 1 gram of the sample. Nonvolatile Matter-Evaporate 30 cc. on the steam bath, dry a t 105' 1 Presented in connection with the report of the Committee on Guaranteed Reagents a t the 71st Meeting of the American Chemical Society, Tulsa, Okla., April 5 to 9, 1926. 2 THIS JOURNAL, 17, 756 (1925).
t o 110' C., and weigh. The weight of the residue should not exceed 0.0010 gram. Chloride-Dissolve 5 cc. in 25 cc. of water, add 2 cc. of nitric acid a n d 1 cc. of 0.1 N silver nitrate. The turbidity should not be greater than is produced by 0.025 mg. of chloride ion in a n equal volume of solution containing the quantities of nitric acid a n d silver nitrate used in the test. Sulfate-To 25 cc. of the sample add 25 cc. of water and 0.01 gram of sodium carbonate and evaporate to dryness on the steam bath. Take up in water, filter, and make up t o a volume of 10 cc. in a test tube. Add 1 cc. of hydrochloric acid (1 volume strong acid in 20) and 1 cc. of 10 per cent barium chloride solution. The turbidity after 10 minutes should not be greater than is produced b y 0.13 mg. of sulfate ( S O I )in a n equal volume of solution containing the quantities of sodium carbonate, hydrochloric acid, and barium chloride used in the test. Phosphate-Evaporate 10 cc. on the steam bath. Take up the residue with 10 cc. of nitric acid and dilute with 50 cc. of water. Nearly neutralize with ammonium hydroxide, cool slightly, add 50 cc. of ammonium molybdate solution, shake (at a temperature of about 40' C.)for 5 minutes, and allow t o stand for half an hour. Any yellow precipitate should not be greater than is formed from 0.1 mg. of PO, in an equal volume of solution containing a s nearly a s possible the quantities of nitric acid, ammonium hydroxide, and ammonium molybdate used in the test. The ammonium molybdate solution is prepared as follows: Solution (1). Mix thoroughly 100 grams of 85 per cent molybdic acid with 240 cc. of water a n d then a d d 140 cc. of ammonium hydroxide. Filter and a d d 60 cc. of concentrated nitric acid. Solution (2). Add 400 cc. of concentrated nitric acid to 960 cc. of water. When the two solutions have cooled, a d d solution (1) t o solution (Z), stirring constantly. Then add 0.1 gram of ammonium phosphate dissolved in 10 cc. water. Stir the solution and allow to stand 24 hours before filtering out the yellow precipitate. Substances Reducing Permanganate-Dissolve 2 cc. of the sample in 10 cc. of water and add 0.4 cc. of 0.1 N potassium permanganate. A t the end of 5 minutes the pink color should not be entirely discharged. Heavy Metals-Dissolve 5 cc. of the sample in 45 cc. of water, pass hydrogen sulfide through the solution, and make just alkaline with ammonium hydroxide. N o brown color should be observed. Any green color should not be greater than is produced b y 0.05 mg. of iron in alkaline solution to which ammonium sulfide is added.
Acetone REQUIREMENTS Assay-Not less than 99.5per cent. Boiling Ranne-From 55.5' to 57.5" C. Nonvolatile Malter-Not more than 0.0013 per cent. Solubility in Water-To pass test. Acids (as acetic)-Not more than 0.003 per cent. Alkaline Subslances (as "8)-Not more than 0.001 per cent. dldehyde-To pass test. Substances Reducing Permanganate-To pass test. TESTS Assay-Test according t o the U. S. Pharmacopeia X. Boiling Range-Test according t o the U. S. Pharmacopeia X , using a sample of 100 cc. Nonvolatile Matter-Evaporate 100 cc. and dry a t 105' to 110' C. The weight of the residue should not exceed 0.0010 gram. Solubility i n Wafer-Mix 25 cc. with 25 cc. of carbon dioxide-free water. The solution should remain clear for 30 minutes. Acids-Add 2 drops of phenolphthalein indicator solution t o the solution prepared in the preceding test. N o t more than 0.1 cc. of 0.1 N sodium hydroxide should be required t o produce a pink color. Alkaline Subslancer-Mix 25 cc. with 25 cc. of water and add 1 drop of methyl red indicator solution. If the solution becomes yellow i t should not require more than 0.1cc. of 0.1 N acid to produce a pink color. Aldehyde-To 10 cc. of the sample add 5 cc. of ammoniacal silver nitrate solution (U. S. P. Test Solution) and allow t o stand protected from t h e
INDUSTRIAL A N D ENGINEERING CHEMISTRY
June, 1926
light a t about 50' C. for 15 minutes. N o brown color or precipitate of silver should develop. Substances Reducing P e r m a n g a n a t e A d d 0.05 cc. of 0.1 N potassium permanganate to 10 cc. of the sample and allow t o stand 15 minutes a t 25O C. The pink color should not be entirely discharged.
Acid, Acetic, Glacial REQUIREMENTS Assay-Not less than 99.5 per cent CHsCOOH. Dilufion Tesf-To pass test. Nonvolatile Matler-Not more than 0.001 per cent. Chloride (CI)-Not more than 0.0002 per cent. Sulfate (Sod-Not more than 0.0003 per cent. Substances Reducing Permanganate-To pass test. Heavy Metals-To pass test (limit about 0.0005 per cent lead, about 0.0002 per cent iron).
TESTS Blank tests must be made on water and all reagents used in the methods unless the directions provide for elimination of errors due t o impurities. Solutions of the sample must be filtered for tests in which insoluble material would interfere. Assay-The freezing point should not be below 15.7' C. Dilufion Test-Dilute 1 volume of acid with 3 volumes of water. N O turbidity should be observed within 1 hour. Nonvolatile Matter-Evaporate 100 cc. on the steam bath and d r y a t 105' to l l O o C. The weight of the residue should not exceed 0.0010 gram. C h l o r i d e D i l u t e 10 cc. with 35 cc. of water, add 3 cc. of nitric acid and 1 cc. of 0.1 N silver nitrate. T h e turbidity should not be greater than is produced by 0.02 mg. of chloride ion in the same volume o f solution containing the quantities of nitric acid and silver nitrate used in the test. Sulfate-To 50 cc. of the sample add 0.01 gram of sodium carbonate and evaporate t o dryness on the steam bath. Take u p in water, filter, and make u p t o 10 cc. in a test tube. Add 1 cc. of hydrochloric acid (1 volume strong acid in 20) and 1 cc. of 10 per cent barium chloride solution. The turbidity after 10 minutes should not be greater than is obtained in a n equal volume of distilled water containing 0.01 gram of sodium carbonate neutralized with hydrochloric acid, 0.15 mg. of sulfate (Sod, and the quantities of hydrochloric acid and barium chloride used with the sample. Substances Reducing Permanganate-Dilute 2 cc. of the sample with 10 cc. of water and add 0.1 cc. of 0.1 N potassium permanganate. The pink color should not be entirely discharged a t the end of 2 hours. Heavy Metals-Dissolve 5 cc. in 45 cc. of water, pass hydrogen sulfide through the solution, a n d make alkaline with ammonium hydroxide. No brown color should be observed. Any green color should not be greater than is produced by 0.01 mg. of iron in alkaline solution t o which ammonium sulfide is added.
Acid Hydrofluoric REQUIREMBNTS Assay-Not less than 46 per cent HF. Fluosilicic Acid (H&iFs)-Not more than 0.25 per cent. Nonvolatile Malter-Not more than 0.003 per cent. Chloride (Cl)-Not more than 0.003 per cent. Sulfate (SO,)-Not more than 0.005 per cent. Suljte (Sod-To pass test (limit about 0.01 per cent). Heavy Metals-To pass test (limit about 0.0005 per cent lead). Iron-To pass test (limit about 0.0005 per cent).
TESTS Blank Iests must be made on water and all reagents used in the methods unless the directions provide for elimination of errors due to impurities. Solutions of the sample must be filtered for tests in which insoluble matter would interfere. Assay and Fluosilicic Acid-Weigh a suitable quantity of the acid into a stoppered platinum crucible or weighing bottle tared with 5 cc. of water. Pour about 10 cc. of a saturated solution of potassium nitrate into a platinum dish, add somewhat less t h a n the necessary amount of N sodium hydroxide (preferably about 50 cc.) and 3 drops of phenolphthalein indicator. Cool the solution to 0' C. and cautiously add the weighed sample of the acid. (Rapid addition may cause loss of the acid.) Titrate with the alkali till the pink color persists for 15 seconds while the temperature of the solution is near 0' C. A , the number of cubic centimeters of alkali used in the titration, is equivalent to all the hydrofluoric acid and one-third of the fluosilicic acid. Heat the solution t o about 80' C. and continue the titration t o a permanent pink. B, the number of cubic centimeters of additional alkali used t o complete the titration, corresponds t o two-thirds of the fluosilicic acid. If W is the weight in grams of the sample, the percentages of hydrofluoric acid and of fluosilicic acid are calculated by the following formulas: 2.001 (A -0.5B) Percentage of hydrofluoric acid (HF)=
U'
637
Percentage of fluosilicic acid (HBiF's) =
-
3.602 B W
Acid which passes the tests for hydrochloric, sulfuric, and sulfurous acids will not contain enough of these acids t o affect the titrations and calculations described above. Nonvolatile Matter-Evaporate 30 cc. in a platinum dish on a steam bath. Add a few drops of sulfuric acid and ignite. T h e residue should not weigh more than 0,0010 gram. Chloride (CI)-Mix in a beaker 45 cc. of water, 2 cc. of nitric acid, and 0.5 cc. of approximately 0.1 &Vsilver nitrate; a d d 3 cc. of the sample. The turbidity should not be greater than is produced by 0.01 mg. of chloride ion in 45 cc. of water by the addition of the quantities of nitric acid and silver nitrate used in the test. Sulfafe (Sod-Add about 0.01 gram of sodium carbonate t o 20 cc. of the acid in a platinum dish and evaporate t o dryness on the steam bath. Moisten the residue with 1 cc. of dilute hydrochloric acid (1 volume strong acid in 20). add 5 cc. of water, filter if necessary, wash or dilute t o 10 cc., and add 1 cc. of 10 per cent barium chloride solution. The turbidity after 10 minutes should not be greater than is produced by 0.01 mg. of sulfate (SO41 in 9 cc. of water upon the addition of the quantities of hydrochloric acid and barium chloride used with the sample. Sulfite-Dilute 10 cc. with 40 cc. of water and add 1 drop of 0.1 N iodine. The solution should show a distinct yellow color. Heavy Metals, Iron-Mix in a beaker 30 cc. of water and 15 cc. of hydrogen sulfide water, add 5 cc. of the sample, a n d render alkaline with ammonium hydroxide. N o brown color should be produced (lead). Any green color should not be greater than is produced b y 0.025 mg. of iron in a n equal volume of solution containing the quantities of hydrogen sulfide water and ammonia used in the test.
Acid, Perchloric REQUIREMENTS Assay-Not less than 20 per cent HCIOI. Nonvolatile Matter-Not more than 0.015 per cent. Chloride (C1)-Not more than 0.001 per cent. Nitrogen ComPounds (as N)-Not more than 0.004 per cent. Sulfate (SO+-Not more than 0.005 per cent. Ammonia ("8)-Not more than 0.001 per cent. Heavy Metals-To pass test (limit about 0.0005 per cent lead, about 0.0001 per cent iron).
TESTS Blank tests must be made on water and all reagents used in the methods unless the directions provide for elimination of errors due t o impurities. Solutions of the sample must be filtered for tests in which insoluble material would interfere. Assay-Titrate a weighed portion of the acid, after suitable dilution, with standard alkali hydroxide solution, using phenolphthalein as indicator. Nonvolatile Matter-Evaporate 9 cc. of the acid and ignite gently. The residue should not weigh more than 0.0015 gram. Chloride-Dilute 5 cc. with 40 cc. of water, add 3 cc. of nitric acid a n d 1 cc. of 0.1 N silver nitrate. The turbidity should not be greater than is produced by 0.05 mg. of chloride ion in the same volume of a solution containing the quantities of nitric acid and silver nitrate used in the test. Nitrogen Compounds-Dilute 1 cc. of the sample in a flask with 10 cc. of ammonia-free water, add 10 cc. of 10 per cent sodium hydroxide solution and about 0.5 gram of aluminum wire in small pieces, and allow t o stand for 3 hours protected from loss or absorption of ammonia. Dilute t o 50 cc., decant from any insoluble matter, and add 2 cc. of Nessler's reagent. The color should not be greater than is produced b y 0.04 mg. of N as NHs in the same volume of a solution containing the quantities of sodium hydroxide and Nessler's reagent used in the test. Sulfate-Dilute 10 cc. of the acid with 35 cc. of water and neutralize with ammonium hydroxide, using litmus paper as indicator. Add 0.5 cc. of dilute hydrochloric acid (1 part strong acid in 10) and 5 cc. of 10 per cent barium chloride solution, and allow to stand overnight. Any precipitate of barium sulfate should not weigh more than 0.0012 gram. Ammonia-Dilute 2 cc. of the sample with 40 cc. of ammonia-free water, add 10 cc. of 10 per cent sodium hydroxide solution and 2 cc. of Nessler's reagent, Any yellow color produced should not be greater than is given by 0.02 mg. of NH3 in the same volume of a solution containing the quantities of sodium hydroxide and Nessler's reagent used in the test. Heavy Metals-Dilute 5 cc. with 40 cc. of water, add 5 cc. of hydrogen sulfide water, and make alkaline with ammonium hydroxide. N o brown color should be observed, Any green color should not be greater than is produced by 0.005 mg. of iron in alkaline solution t o which ammonium sulfide is added.
Aluminum and Potassium Sulfate REQUIREMBNTS Insoluble Matter-Not more than 0.005 per cent. Chloride (CU-Not more than 0.0005 per cent.
INDUSTRIAL A N D ENGINEERIh-G CHEMISTRY
638
Ammonia (NHs)-Not more than 0.005 per cent. Arsenic (As)-Not more than 0.0002 per cent. Heavy Metals-To pass test (limit about 0.001 per cent lead). l r o n (Fe)-Not more than 0.001 per cent.
TESTS Blank Tests must be made on water a n d all reagents used in the methods unless the directions provide for elimination of errors due t o impurities. Solutions of the sample must be filtered for tests in which insoluble matter would interfere. lnsoluble Matter-Dissolve 10 grams in 100 cc. of hot water, filter through asbestos in a Gooch crucible, wash with hot water, dry a t 1 0 5 O t o 110' C., and weigh. The weight of the residue should not exceed 0.0005 gram. Chloride-Dissolve 2 grams in 20 cc. of warm water, a d d 1 cc. of nitric acid and 0.5 cc. of approximately 0.1 N silver nitrate. The turbidity should not be greater than t h a t produced b y 0.01 mg. of chloride ion in an equal volume of solution containing the quantities of nitric acid and silver nitrate used in the test. Ammonia-Dissolve 1 gram in 20 cc. of water, a d d sodium hydroxide solution to redissolve the precipitate first formed, a n d then a d d 2 cc. of Nessler's solution. The color should'not be more than is produced by a quantity of an ammonium salt corresponding to 0.05 mg. of NH3 in an equal volume of solution containing the quantities of sodium hydroxide and Nessler's solution used in the test. Arsenic-Test 2 grams b y the modified Gutzeit method. Special care in making blank tests is necessary in this determination. Heavy Metals-Dissolve 2 grams in 25 cc. of water and pass hydrogen sulfide through the solution. The solution should not be darkened. Iron-Dissolve 5 grams in 90 cc. of water a n d add 5 cc. of hydrochloric acid and 2 cc. of nitric acid. Boil for a few minutes, cool, make up to 100 cc., a n d a d d 5 cc. of 10 per cent ammonium thiocyanate solution. If a pink color is produced, i t should not be greater than is produced by 0.05 mg. of iron in a ferric salt in a n equal volume containing the quantities of the acids and thiocyanate used in the test.
Ammonium Acetate REQUIREMENTS Insoluble Matter-Not more than 0.005 per cent. Nonvolatile Matter-Not more than 0.010 per cent. Chloride (CI)-Not more than 0.0005 per cent. Nitvatc (NOa)-To pass test (limit a b o u t 0.001 per cent). Sulfate (SO,)-Not more than 0.001 per cent. Heavy Metalr-To pass test (limit about 0.0005 per cent lead). Iron-To pass test (limit about 0.0005 per cent).
TESTS Blank tests must be made on water and all reagents used in the methods unless t h e directions provide for elimination of errors due t o impurities. Solutions of the sample must be filtered for tests in which insoluble matter would interfere. Insoluble Matter-Dissolve 10 grams in 50 cc. of water, filter through asbestos in a Gooch crucible, wash, d r y at 105" t o 110' C., and weigh. The weight of t h e residue should not exceed 0.0005 gram. Nonvolatile Matter-Gently ignite 5 grams of the sample. The residue should not weigh more t h a n 0.0005 gram. Chloride-Dissolve 2 grams in 20 cc. of water, add 1 cc. of nitric acid a n d 0.5 cc. of approximately 0.1 N silver nitrate solution. Any turbidity produced should not be greater than t h a t produced b y 0.01 mg. of chloride ion in a n equal volume of solution containing the quantities of nitric acid a n d silver nitrate used in the test. Nitrate-Dissolve 3 grams in 10 cc. of water and add 10 cc. of sulfuric acid. T o t h e hot solution a d d about 5 mg. of sodium chloride and 1 drop of indigo solution (1 in 1000). The blue color should not be entirely discharged after standing 5 minutes. SuZfateDissolve 10 grams in 10 cc. of water, add 0.01 gram of sodium carbonate, evaporate t o dryness, and heat a t 120' C. till all the ammonium acetate is volatilized. Add t o the residue 1 cc. of hydrochloric acid (1 volume of strong acid in 20) and 5 cc. of water. Filter and wash till the filt r a t e measures 10 cc.; add l cc. of 10 per cent barium chloride solution. Any turbidity produced in 10 minutes should not be greater than t h a t produced b y 0.1 mg. of SO4 in a n equal volume containing the quantities of acid a n d barium chloride used in the test. Heavy Metals-Dissolve 2 grams in 40 cc. of water, add 3 cc. of hydrochloric acid, atld heat to boiling. Cool, neutralize with ammonium hydroxide, a d d 1 cc. of N hydrochloric acid, dilute t o 50 cc., a n d pass hydrogen sulfide through t h e solution. N o brown color should be produced. Iron-Make the solution from the preceding test slightly alkaline with ammonium hydroxide. If a green color is produced, i t should not he greater t h a n is produced by 0.01 mg. of iron in a n alkaline sulfide solution of equal volume prepared with the quantities of hydrochloric acid and ammonium hydroxide used in the test.
T'ol. 18,No. 6
Ammonium Carbonate REQUIREMENTS Assay-Not less than 30 per cent N&. Insoluble Matter-Not more than 0.005 per cent. Nonvolatile Mat&-Not more than 0.005 per cent. Chloride (C1)-Not more than 0.0005 per cent, Sulfur Compounds (as S03-Not more than 0.001 per cent. Heavy Metals-To pass test (limit about 0.0005 per cent lead) Iron (Fe)-To pass test (limit about 0.0005 per cent).
TESTS Blank t e s l s must be made on water and all reagents used in the methods unless the directions provide for elimination of errors due to impurities. Solutions of the sample must be filtered for tests in which insoluble matter would interfere. Assay-Titrate a weighed portion with standard acid, using methyl orange indicator. Insoluble Matter-Dissolve 10 grams in 50 cc. of hot water. Filter through asbestos in a Gooch crucible, wash, dry a t 105' to 110' C., a n d weigh. The weight of the residue should not exceed 0.0005 gram. Reserve filtrate for test for sulfur compounds. Nonvolatile Matter-Volatilize 10 grams in a weighed dish on the steam bath and dry a t 105' t o 110' C. The residue should not weigh more than 0.0005 gram. Reserve the residue for the test for heavy metals. Chloride-Dissolve 2 grams in 25 cc. of hot water, a d d 0.01 gram.of sodium carbonate, and evaporate t o dryness on the steam bath. Dissolve the residue in 10 cc. of water, filter if necessary, a n d add 0.5 cc. of nitric acid and 0.5 cc. of 0.1 N silver nitrate solution. The turbidity produced should not be greater than is produced b y 0.01 mg. of chloride ion in the same volume of solution containing the quantities of nitric acid and silver nitrate used in the test. Sulfur Com$ounds-To the filtrate obtained in the test for insoluble matter add 0.01 gram of sodium carbonate, evaporate t o about 5 cc., add a few drops of bromine water (or sufficient t o impart a slight color to the solution), and evaporate t o dryness. Take u p the residue with a few cubic centimeters of water and 1 cc. of dilute hydrochloric acid (1 volume of acid to 20 volumes of water), filter if necessary, make u p t o 10 cc., and add 1 cc. of 10 per cent barium chloride solution. T h e turbidity produced in 10 minutes should not be greater than t h a t produced b y 0.1 mg. of sulfate radical (Son) in an equal volume of solution containing the quantities of reagents used in the test. Heavy Metals-Moisten the residue from the determination of nonvolatile matter with 5 drops of hydrochloric acid and dilute to 25 cc. Dilute 5 cc. of this solution to 25 cc. and pass hydrogen sulfide through the diluted solution. N o brown color should be produced. Iron-Add ammonium hydroxide t o make slightly alkaline the solution which has been tested for heavy metals. If a green color is produced, i t should not be greater than is produced by 0.01 mg. of iron in a n equal volume of a slightly alkaline sulfide solution.
Ammonium Chloride REQUIREMENTS Insoluble Matter-Not more than 0.005 per cent. Nonvolatile Matter-Not more than 0.015 per cent. Free Acid-To pass test. Phosphate (PO,)-Not more than 0.0003 per cent. SuZfate (SO,)--To pass test (limit about 0.002 per cent). Calcium and Magnesium Precipitale-Not more than 0.002 per cent. Heavy Metals-To pass test (limit about 0.0005 per cent lead). Iron-To pass test (limit about 0.0005 per cent).
TESTS Blank tests must be made on water and all reagents used in the methods unless t h e directions provide for elimination of errors due t o impurities. Solutions of the sample must be filtered for tests in which insoluble matter would interfere. Insoluble Matler-Dissolve 20 grams in 50 cc. of water and allow t o stand on the steam bath for 1 hour. Filter through asbestos in a Gooch crucible, wash, dry a t 105" t o llOo C.,and weigh. T h e residue should not weigh more than 0.0010 gram. Nonvolatile Matter-To 20 grams of the sample a d d 2 cc. of sulfuric acid, heat a t a low temperature, a n d then ignite gently. The residue should not weigh more than 0.0030 gram. Free Acid-Dissolve 5 grams in 50 cc. of freshly boiled and cooled water and a d d 1 drop of methyl red indicator. N o red color should be produced. Phosphate-Decompose 10 grams with 15 cc. of nitric acid b y taking t o dryness on the steam bath. Take up with 10 cc. of nitric acid, dilute with 50 cc. of water, a n d nearly neutralize with ammonium hydroxide. Add 50 cc. of ammonium molybdate solution, shake the solution (at about 40' C.) for 5 minutes, and allow t o stand one-half hour. Any precipitate formed should be less than is produced when a quantity of an alkaline phosphate containing 0.03 mg. of phosphate (PO,) is treated according t o t h e above
I X D U S T R I A L A X D ENGINEERISG CHE.WISTRY
June, 1926
procedure. The ammonium molybdate solution is prepared a s directed under the test for phosphate in acetic anhydride. Suljale-Dissolve 5 grams in 100 cc. of water, a d d 1 CC. of dilute hydrochloric acid (1 volume of strong acid in 4 J , heat to boiling, a d d 5 cc. of barium chloride, and allow to stand overnight. N o precipitate or turbidity should be produced. ' Calcium and Magnesium Precipitale-Warm the residue obtained in the determination of nonvolatile matter with 1 cc. of hydrochloric acid and 3 cc. of water. Add 2 cc. of ammonium hydroxide, filter, and add to the filtrate 2 cc. of 4 per cent ammonium oxalate solution a n d 2 cc. of 10 per cent ammonium phosphate. Allow t o stand overnight. If a n y precipitate is formed, filter, wash with a solution containing 2.5 per cent of ammonia. The weight of the ignited precipitate should not be more than 0.0004 gram. Heavy Melds, Iron-Dissolve 5 grams in 50 cc. of water, pass hydrogen sulfide through the solution, a n d a d d 1 cc. of ammonium hydroxide. h70 brown color should be produced (lead). Any green color should not be greater than is produced b y 0.025 mg. of iron in an equal volume of solution containing the quantities of ammonium hydroxide and sulfide used in the test.
A m m o n i u m Persulfate REQUIREMENTS Assay-Not less than 85 per cent (NH4)EhOs. Insoluble Muller-Not more than 0.040 per cent. Xonvolalile Matter-Not more than 0.25 per cent. Chloride (C1)-Not more than 0.001 per cent. Manganese (Mn)-Not more than 0.0001 per cent. Heacy ddelals-Not more than 0.030 per cent a s oxides.
TESTS Blank tests must be made on water a n d all reagents used in the methods unless the directions provide for elimination of errors due t o impurities. Solutions of the sample must be filtered for tests in which insoluble matter would interfere. Assass-Add 0 . 3 gram t o 25 cc. of a 10 per cent solution of potassium iodide. Then add 10 cc. of 10 per cent sulfuric acid, allow to stand onehalf hour, and titrate the liberated iodine with 0.1 N sodium thiosulfate. Make a blank test with the quantities of reagents used with the sample and apply a correction if necessary. Insoluble Matter-Dissolve 5 grams in 100 cc. of water and allow to stand on the steam bath for 1 hour. Filter through asbestos in a Gooch crucible, wash, dry a t 105' to 110" C., a n d weigh. The residue should not weigh more than 0.0020 gram. Nonvololile Muller-Gently ignite 2 grams in a weighed dish. The residue should not weigh more than 0.0060 gram. Chloride-Dissolve 2 grams in 10 cc. of water and a d d 0.5 cc. of 0.1 N silver nitrate solution. A n y turbidity produced in one minute should not be greater than t h a t produced b y 0.02 mg. of chIoride ion in the same volume of distilled water slightly acidified with nitric acid and containing 0.5 cc. of 0.1 N silver nitrate. Manganese-To the residue obtained from the volatilization of 9 grams of the sample a d d 10 drops of hydrochloric acid and evaporate to dryness on the water bath. Add 2 cc. of sulfuric acid a n d heat until fumes of sulfur trioxide are evolved. Cool, cautiously dilute with 20 cc. of water in a small flask, add 1.5 cc. of 0.1 N silver nitrate, heat to between 80' and 85' C., immediately add 1 gram of ammonium persulfate, and maintain at this temperature for 1 minute. Cool quickly and if not clear filter through a small pledget of glass wool. If the filtrate is pink, match the color in a blank (omitting hydrochloric acid) b y the addition of dilute standard potassium permanganate solution. The quantity of permanganate required to match the color should correspond to not more than 0.01 mg. of manganese (Mn). Heavy Melds-To the residue obtained in the test for nonvolatile matter a d d 2 cc. of hydrochloric acid and a few drops of nitric acid a n d evaporate t o dryness on the water bath. Take up the residue with a few drops of hydrochloric acid and 10 cc. of water, filter, and wash with a small amount of hot water. Pass hydrogen sulfide through the filtrate a n d render the filtrate slightly alkaline with ammonium hydroxide. Heat on the steam bath to coagulate the sulfides, filter (without washing), dry, ignite, and weigh. The weight should not exceed 0.0006 gram.
A m m o n i u m Sulfate REQUIREMENTS Insoluble Mailer-Not more than 0.005 per cent. Nonvolatile Mallev-Not more than 0.010 per cent. Free Acid-To pass test. Chloride (CI)-Not more than 0.0006 per cent. Xilratc? (NO+-To pass test (limit about 0.001per cent). Phosphate (POd)-Not more than 0.0005 per cent. Arsenic (AsI-Not more than 0.0005 per cent. Heaoy'Melals-To pass test (limit about 0.0005 per cent lead). Iron (Fe)-To pass test (limit about 0.0005 per cent).
639 TESTS
Blank lests must be made on water and all reagents used in the methods unless the directions provide for elimination of errors due to impurities. Solutions of the sample must be filtered for tests in which insoluble matter would interfere. Insoluble Muller-Dissolve 10 grams in 50 cc. of water, filter through asbestos in a Gooch crucible, wash, dry a t 105' to 110' C., and weigh. The weight of the residue should not exceed 0.0006 gram. A-onoolafile Matter-Heat 10 grams gently in a weighed dish till the salt is volatilized, and ignite a t cherry redness for 5 minutes. The weight of the residue should not be more than 0,0010gram. Free Acid-Dissolve 5 grams in 50 cc. of carbon dioxide-free water and add 1 drop of methyl red indicator solution. No red color should be produced. Chloride-Dissolve 2 grams in 20 cc. of water, a d d 1cc. of nitric acid and 0.5 cc. of 0.1 N silver nitrate solution. The turbidity should not be greater than is produced b y 0.01 mg. of chloride ion in a n equal volume of solution with the quantities of reagents used in the test. Nitrale-Dissolve 3 grams in 10 cc. of water a n d add 10 cc. of sulfuric acid. T o the hot solution add about 5 mg. of sodium chloride a n d 1 drop of indigo solution (1 in 1000). The blue color should not be entirely discharged after standing 5 minutes. Phosphate-Dissolve 6 grams in 50 cc. of water, a d d 10 cc. of nitric acid, nearly neutralize with ammonium hydroxide, add 50 cc. of ammonium molybdate solution, shake for 5 minutes at about 40' C., and allow to stand for 1 hour. Any precipitate produced should not be greater than is produced from a quantity of an alkaline phosphate containing 0.025 mg. of Po4 which has been treated like the sample. Arsenic-Test 1 gram b y the modified Gutzeit method. The quantity of arsenic found should not be more than 0.005 mg. Special care in making blank tests is necessary in this determination. Heavy Mefals-Dissolve 2 grams in 50 cc. of water, a d d 0.5 cc. of glacial acetic acid, and pass hydrogen sulfide through the solution. N o brown color should be produced. Iron-Render the solution obtained in t h e heavy metals test alkaline with ammonium hydroxide. If a n y greenish color is produced i t should not be greater than is produced by 0.01 mg. of iron in an equal volume of alkaline sulfide solution.
Amyl Alcohol (Isoamyl Alcohol) REQUIREMENTS Nonvolalile Mailer-Not more than 0.003 per cent. Boiling Range-From 128' t o 132O C. Acids and Esters (as amyl acetate)-Not more than 0.060 per cent. Aldehydes-To pass test. Subslances Darkened by Sulfuric Acid-To pass test.
TESTS Blank tests must be made on water a n d all reagents used in the methodr unless the directions provide for elimination of errors due t o impurities. 25 cc. on the steam bath and dry at Nonvolatile Matter-Evaporate 105' to 110' C. The weight of the residue should not exceed 0.0006 gram. Boiling Range-Follow the directions for this test in the U. S. Pharmacopeia X,using 50 cc. of the sample. Acids and Esters-Dilute 20 cc. with 20 cc. of ethyl alcohol, add 5 cc. of 0.1 N sodium hydroxide solution, and heat gently under a reflux condenser for 10 minutes. Cool,,add 3 drops of phenolphthalein indicator solution, and titrate the excess of sodium hydroxide with 0.1 N hydrochloric acid. N o t more than 0.75 cc. of the 0.1 N sodium hydroxide should have been consumed, correction being made for the amount consumed in a blank test. Aldehydes-Shake 5 cc. with 5 cc. of 30 per cent potassium hydroxide solution for 5 minutes in a glass-stoppered cylinder and allow to separate. N o color should develop in either layer. Substances Darkened by Sulfuric Acid-Agitate 10 cc. with an equal volume of sulfuric acid in a glass-stoppered cylinder for 5 minutes. The liquid should be colorless or have not more than a pale yellow color. (To be continued in 2he next issue)
Report of A. C. S. Committee on Guaranteed Reagents During the year 1925-26 the committee prepared tentative specifications for twenty-three reagents, and has considered thirteen additional specifications, several of which are nearly completed. The recommended specifications' do not appear t o be strikingly different from others t h a t have been published. Careful comparison, however, will show t h a t they are more definite in the description of tests and more accurate as regards the limits represented by the tests. 1
Beginning page 636, this issue.
W. D. COLLINS,Chairman
