ANALYTICAL EDITION
154
Clark, W. M., and Cohen, B., U . S. Pub. Health Seruice, Hug.
mixtures satisfactory results may be obtained. B y calculation, the Orange I present (0.05 gram) should be completely reduced when 14.2 cc. of the 0.0401 N titanium trichloride solution had been added. Correspondingly, the calculated end point for the total dye content should be at 27.0 cc., which is exactly the case. Curve 3 is plotted from the same data used in making curve 2, the difference being that V (cc. of TiCla used) is plotted against the increment of the potential divided b y the increment in volume of the reagent (AV). This method of plotting has been explained b y Hostetter and Roberts (6). It gives a more satisfactory indication of the end point on a curve that does not have a sharp break and is applicable to all electrometric-titration curves.
Lab. Bull. 151,32 (1928).
Conant, J. B., and Biglow, N. M., J . A m . Chem. SOC.,53,676 (1931).
Evenson, 0. L., and McCutchen, D. T., IND. Eaa. CHEY.,20, 860 (1928).
Evenson, 0. L., and Nagel, R. H., Ibid., Anal. Ed., 3, 167 (1931). Hostetter, J. C., and Roberts, H. S., J . A m . Chem. Soc., 41, 1343 (1919).
(1926).
Kolthoff, I. M., and Tomicek, O., Ibid., 43,775 (1924). Tomicek, O.,Ibid., 43,808 (1924).
LITERATURE CITED Ambler, J. A,, Clarke, W. F., Evenson, 0. L., and Wales, H., U. 8. Dept. Agr., Bull. 1390 (revised 1927), and Suppl. 1 (March, 1930).
I
Jones, D.O.,and Lee, H. R., IND. E m . CHEW,14,46 (1922). Knecht, E., and Hibbert, E., “New Reduction Methods in Volumetric Analysis,” Longmans, 1918. Kolthoff, I. M., Rec. trav. chim., 43,768 (1924). Kolthoff, I. M., and Furman, N. H., “Potentiometrio Titrations,” p. 304, Wiley, 1926. Kolthoff, I. M., and Robinson, C., Rec. trav. chim., 45, 169
(a)
(1)
Vo!. 4, No. 1
RBICBIYED July 13, 1931. Ninth oontribution from the Color Certification Laboratory, Food and Drug Administration, U. S. Department of Bgrioulture.
Recommended Specifications for Analytical Reagent Chemicals
,
Barium Acetate, Borax (Sodium Borate, Na,B,O,.lOH,O), Cadmium Sulfate, Ferric Chloride, Ferric Nitrate, Litmus Paper, Potassium Bisulfate Fused ,-
W. D. COLLINS, GREGORYP. BAXTER,H. V. FARR,J. V. FREEMAN, JOSEPH ROSIN, G. C. SPENCER,AND EDWARD WICHERS,Conmiittee on Analytical Reagents, American Chemical Society HE specifications given below are intended to serve for reagents to be used in careful analytical work. The
Heavy Metals-To pass test (limit about 0.0005 per cent lead). Iron (Fe)-Not more than 0.001 per cent.
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. Suggestions for the improvement of the specifications will be welcomed by the committee. In all the directions the acids and ammonium hydroxide referred t o are of full strength unless dilution is specified; dilution indicated as (1 3) means 1 volume of the reagent or strong solution with 3 volumes of water; “water” means distilled water of a grade suitable for the test described; reagents used in making the tests are supposed t o be of the grade recommended below or in previous publications (18) from the committee. Directions for the preparation of t h e ammonium molybdate solution are given under the test for phosphate in ammonium nitrate (3). A time of 5 minutes is to be allowed for the appearance of precipitates and before observation of color reactions, unless some other time is specified. Blank tests must be made on water and all reagents used in the tests unless the directions provide for elimination of errors due t o impurities. Solutions of samples must be filtered for tests in which insoluble matter would interfere.
TESTS Insoluble Maher-Dissolve 10 grams in about 100 cc. of hot water and allow to stand on the steam bath for 1 hour. Filter through asbestos in a Gooch crucible, wash thoroughly, dry at 105’ to 110” C., and weigh. The weight of the residue should not exceed 0.0010 gram. Chloride-Dissolve 1 gram in 20 cc. of water and add 2 drops of nitric acid and 1 cc. of 0.1 N silver nitrate. The turbidity should not be greater than is produced by 0.03 mg. of chloride ion in an equal volume of solution containing the quantities of nitric acid and silver nitrate used in the test. Nitrate-Dissolve 3 grams in 15 cc. of water, add 1 drop of indigo solution (1 in IOOO), and add with constant stirring 15 cc. of sulfuric acid. The blue color should not be destroyed in 5 minutes. Alkali Salts-Dissolve 5 grams in about 150 cc. of water, add 1 cc. of hydrochloric acid, and heat to boiling. Add 25 cc. of 2 N sulfuric acid, cool, make up t o 250 cc., and allow to stand overnight. Decant through a filter, evaporate 100 cc. of the filtrate to dryness, ignite, and weigh the residue. The weight should not exceed 0.0020 gram. Calcium and Strontium Salts-Dissolve 2 grams in 10 cc. of hot water, add 10 cc. of hydrochloric acid, and evaporate to dryness on the steam bath. Dissolve the residue in 10 cc. of hot water, add 10 cc. of hydrochloric acid, evaporate t o dryness again, and dry in the oven at 105’ C. Powder the residue and add 20 cc. of absolute alcohol. Allow to stand for 30 minutes with occasional shaking. Filter, evaporate the filtrate, ignite gently, and weigh. The weight of the residue should not exceed 0.0030 gram. Heavy Metals-Dissolve 2 grams in 40 cc. of water, add 1 cc. of N hydrochloric acid, and pass hydrogen sulfide gas through the solution. No brown color should be produced. Observation of the color should be made within 2 minutes. Iron-Add ammonium hydroxide to the solution tested for heavy metals until i t is alkaline t o litmus. Any green color should be no greater than is produced by 0.02 mg. of iron in an alkaline sulfide solution.
T
+
BARIUM ACETATE
REQUIREMENTS Insoluble Matter-Not more than 0.010 per cent. Chloride (C1)-Not more than 0.003 per cent. Nitrats (NOs)-To pass test (limit about 0.01 per cent). Alkali Salts (as sulfates)-Not more than 0.10 per cent. Calcium and Strontium Salts-Not more than 0.15 per cent.
January 15, 1932
I N D U S T R I A L A N D E N G I N E E R I N G CHEMTSTRY
RORAX (SODIUM BORATE,
NazB407.10Hz0)
REQUIREMENTS Insoluble Matter-Not more than 0.005 per cent. Chloride (C1)-Not more than 0.001 per cent. Phosphate (PO4)-Not more than 0.001 per cent. Sulfate (SO&--Not more than 0 005 per cent. Calcium (Ca)-To pass test (limit about 0.005 per cent). Heazy Metals-To pass test (limit about 0.001 per cent as lead). Iron (Fe)--Not more than 0.001 per cent. TESTS Insoluble Matter-Dissolve 10 grams in 150 cc. of water and heat on the steam bath for 1 hour. Filter through asbestos in a Gooch crucible, wash thoroughly, dry a t 105' to 110" C., and weigh. The weight of the residue should not exceed 0.0005 gram. Chloride-Dissolve 1 gram in 15 cc. of warm water. Add 1 cc. of nitric acid and 1 cc. of approximately 0.1 N silver nitrate. Any turbidity produced at the end of 15 minutes should not be greater than is produced by 0.01 mg. of chloride ion in an equal volume of solution with the quantities of reagents used in the test. Phosphate-Dissolve 5 grams in 75 cc. of water and add 10 cc. of nitric acid and 8 cc. of ammonium hydroxide. Warm to 60" C., add 50 cc. of ammonium molybdate solution, and shake for 5 minutes. Any precipitate should not be greater than is produced in a solution of equal volume with the same quantities of reagents and 0.05 mg. of Pod. Sulfate-Dissolve 8 grams in 120 cc. of warm water and 6 cc. of hydrochloric acid. Filter and wash with 30 cc. of water. Heat to boiling, add 5 cc. of 10 per cent barium chloride solution, and allow to stand overnight. Heat to dissolve any boric acid that may be crystallized. Filter, wash thoroughly, ignite, and weigh. The weight of the ignited precipitate should not be more than 0.0010 gram greater than the weight of the ignited precipitate from a blank made with the quantities of the reagents used in the test, including filtration and ignition of the paper. Calcium-Dissolve 2 grams in 25 cc. of water and add 1 cc. of acetic acid and 5 cc. of 4 per cent ammonium oxalate solution. N o turbidity should appear in 10 minutes. Heavy Metals-Dissolve 2 grams in 25 cc. of hot water, add 0.5 cc. of hydrochloric acid, heat to about 80" C., and add 5 cc. of hydrogen sulfide water. No darkening of the solution should be observed. Iron-To the solution tested for heavy metals add ammonium hydroxide until it is alkaline to litmus. Any greenish color should not be greater than is produced by 0.02 mg. of iron in an alkaline sulfide solution. CADMIUM SULFATE REQUIREMENTS
Insoluble Matter--Kot more than 0.005 per cent. Chloride (C1)-Not more than 0.001 per cent. Nitrate (X03)-To pass test (limit about 0.005 per cent). Arsenic (&)-Not more than 0.0002 per cent. Copper (Cu)-To pass test (limit about 0.002 per cent). Iron (Fe)-To pass test (limit about 0.001 per cent). Lead (Pb)-To pass test (limit about 0.005 per cent). Substances Not Precipitated by Ammonium Sul/;de-Not more than 0.15 per cent. Zinc (Zn)-To pass test (limit about 0.05 per cent).
TESTS Insoluble Matter-Dissolve 10 grams in 150 cc. of water and allow to stand on the steam bath for 1 hour. Filter through asbestos in a Gooch crucible, wash thoroughly, dry a t 105" to 110" C., and weigh. The weight of the residue should not exceed 0.0005 gram. Chloride-Dissolve 1 gram in 10 cc. of water and add 1 cc. of nitric acid and 1 cc. of approximately 0.1 N silver nitrate. Any turbidity should not be greater than is produced by 0.01 mg. of chloride ion with the same quantities of reagents. A-itrate-To a solution of 1 gram in 10 cc. of warm water add about 10 mg. of sodium chloride, 2 drops of freshly prepared indigo solution (I in 1000), and 10 cc. of sulfuric acid. The blue color should not be disch,arged in 5 minutes. Arsenic-Test 5 grams by the Gutzeit *method as described in the I.7. S. Pharmacopeia. Copper and Iron-Dissolve 1 gram in 10 cc. of water, add 2 drops of nitric acid, bring to a boil, and allow to cool. Add 2 drops of a freshly prepared 10 per cent solutim of potassium
155
ferrocyanide. No red or blue color should be produced after standing 15 minutes. Lead-Dissolve 1 gram in 25 cc. of water, add 5 drops of glacial acetic acid, and filter if necessary. Add 1 cc. of 1 per cent potassium chromate solution. Any turbidity or precipitate should not be greater than is produced by 0.05 mg. of lead under the same conditions. Substances Not Precipitated by Ammonium Xu1fide-Dissolve 2 grams in 150 cc. of water, add ammonium hydroxide to dissolve the precipitate first formed, and pass hydrogen sulfide gas through the solution to precipitate all the cadmium. Filter off 75 cc. of the clear liquid, add 5 drops of sulfuric acid, evaporate t o dryness, and ignite gently. The weight of the ignited residue should not be more than 0.0015 gram. Zinc-Dissolve 0.2 gram in 100 cc. of water and add 3.5 cc. of sulfuric acid. Heat to boiling and pass a rapid stream of hydrogen sulfide for 15 minutes, allowing the solution to cool during the passage of the gas. Filter at once, evaporate t h e filtrate, and ex el practically all of the sulfuric acid. Take u p the residue wit! 5 cc. of water and add ammonium hydroxide until the solution is just alkaline to litmus paper. Then make it just acid to the litmus paper with 0.1 N sulfuric acid. Dilute to 100 cc. and pass a rapid stream of hydrogen sulfide for 6 minutes. No white precipitate or turbidity should be produced. FERRIC CHLORIDE
REQUIREMENTB Insoluble Matter-Not more than 0.010 per cent. Nilrate (N03)-To pass test (limit about 0.01 per cent). Phosphorus Compounds-Not more than 0.030 per cent a s PO& Sulfate (SOa)-Not more than 0.005 per cent. Arsenic (As)-To pass test (limit about 0.002 per cent). Copper (Cu)-To pass test (limit about 0.003 per cent). Ferrous Iron (Fe)-To pass test (limit about 0.002 per cent). Substances Not Precipitated by Ammonium Hydroxide-Not, more than 0.10 per cent. Zinc (Zn)-To pass test (limit about 0.003 per cent). TESTS Insoluble Matter-Dissolve 10 grams in 50 cc. of water and 1 cc. of hydrochloric acid and heat on the steam bath for 1 hour. Filter through asbestos in a Gooch crucible, wash with warm water containing about 0.5 per cent of hydrochloric acid until the washings are free of iron, dry a t 105' to, 110' C., and weigh. The weight of the insoluble residue should not exceed 0.0010 gram. Phosphorus Compounds-To 5 grams add 20 cc. of water and 20 cc. of nitric acid and evaporate on the steam bath to a sirup. Add 50 cc. of water, 15 cc. of nitric acid, and 13 cc. of ammonium hydroxide. Add 50 cc. of ammonium molybdate solution, shake for 5 minutes a t 40' to 50' C., and allow to stand for 1 hour. Any precipitate formed should not be greater than is formed under the same conditions by 1.5 mg. of Pod. Nitrate, Sulfate, and Substances Not Precipitated by Ammonium H ydrozideSolution A: Dissolve 10 grams in 100 cc. of water. Heat t o boiling and pour into a mixture of 140 cc. of water and 50: cc. of ammonium hydroxide. Filter through a folded filter while still hot and wash with hot water until the filtrate (solution A) measures 300 cc. Nitrate: Mix 15 cc. of solution A with 15 cc. of sulfuric acicf and add 2 drops of indigo solution (I in 1000). The blue colorshould not disappear in 5 minutes. Sulfate: Evaporate 120 cc. of solution A to 50 cc. and add 0.5 cc. of dilute hydrochloric acid (1 2 ) . Prepare a standard of equal volume containing 20 cc. of ammonium hydroxide, which has been boiled to expel the ammonia, 0.20 mg. of SO4, and 0.5 cc. of dilute hydrochloric acid (1 2). Add 3 cc. of 10 per cent barium chloride to each solution. After 10 minutes. the turbidity produced by the sample should not be greater than that produced by the standard. Substances Not Precipitated by Ammonium Hydyoxide: Evaporate 30 cc. of solution A to dryness. Add 10 drops or sulfuric acid and ignite cautiously. The weight ot the residue should not exceed 0.0010 gram. Arsenic-Dissolve 1 gram in 0.5 cc. of hydrochloric acid and add 5 cc. of freshly prepared stannous chloride solution. Warm t o 70' t o 80" C. for 5 minutes and allow t o stand for an additional 25 minutes. A t the end of this time the solution should not be noticeably darker than a mixture prepared with the same quantities of ferric chloride and stannous chloride solution immediately before observing the test. The stannous chloride solution used in this test is made b y saturating hydrochloric acid with stannous chloride.
+
+
156
Vol. 4, No. 1
ANALYTICAL EDITION
Copper and Zinc-Neutralize 90 cc. of solution A with acetic acid and add an excess of 1 cc. of glacial acetic acid and 2 cc. of freshly prepared 10 er cent solution of potassium ferrocyanide. No turbidity or i& color should appear in 30 minutes. Ferrous Iron-bssolve 0.5 gram in a mixture of 20 cc. of water and 1 cc. of hydrochloric acid and add 1 drop of a freshly prepared 5 per cent solution of potassium ferricyanide. No blue color should be produced in 1 minute. FERRIC NITRATE
REQUIREMENTS Insoluble Matter-Not more than 0.010 per cent. Chloride (C1)-Not more than 0.001 per cent. SuEfate (SOd)-Not more than 0.010 per cent. Substances Not Precipitated by Ammonium Hvdroxide-Not more than 0.10 per cent.
TESTS Insoluble Matter-Dissolve 10 grams in a mixture of 100 cc. of water and 1 cc. of nitric acid and heat on the steam bath for 1 hour. Filter through asbestos in a Gooch crucible, wash thoroughly, and dry at 105' to 110' C. The weight of the residue should not exceed 0.0010 gram. Chloride-Dissolve 2 grams in 15 cc. of water and add 1 cc. of nitric acid. To 15 cc. of water add I cc. of nitric acid and hydrochloric acid equivalent to 0.02 mg. of chloride. Add to each solution 1 cc. of 0.1 N silver nitrate. The sample should not be more turbid than the standard. Sulfate and Substances Not Precipitated by Ammonium HydroxideSolution A: Dissolve 5 grams in 70 cc. of water and pour it into a mixture of 15 cc. of ammonium hydroxide and 80 cc. of water. Filter through a folded filter and wash with hot water until the filtrate measures 250 cc. Sulfate: Evaporate 100 cc. of solution A to 50 cc. and add 0.5 cc. of dilute hydrochloric acid (1 2). Prepare a standard of equal volume containing 6 cc. of ammonium hydroxide, which has been boiled to ex el the ammonia, 0.20 mg. of Sod, and 0.5 cc. of dilute hydrocfloric acid (1 2). Add 3 pc. of 10 per cent barium chloride to each solution. After 10 minutes the turbidity produced by the sample should not be greater than that produced by the standard. Substances Not Precipitated by Ammonium Hydroxide: Evaporate 50 cc. of solution A to dryness, add 10 drops of sulfuric acid, and ignite carefulIy. The weight of the residue should not exceed 0.0010 gram.
+
+
LITMUS PAPER
REQUIREMENTS Ash-Not more than 0.4 mg. per strip (about 3 sq. cm.). Rosin Acids, etc. (for blue paper only)-To pass test. Sensitiveness-To pass test.
TESTS Ash-Ignite carefullv 10 strios. The ash should not be more than 0.0020 gram. " Rosin Acids, etc.-Immerse a strip of blue paper in a solution of 0.10 gram of silver nitrate in 50 cc. of water. The color should not change in 30 seconds. Sensitiueness-Drop a piece of the paper into 100 cc. of test solution in a beaker and stir continuously. A blue paper should change color in 45 seconds in 0.0005 N acid. A red paper should change color in 30 seconds in 0.0005 N alkali. POTASSIUM BISULFATE FUSED
in a Gooch crucible, wash thoroughly, and dry 1 hour a t 105' to 110' C. The weight of the . precipitate should not be more . than 0.0010 gram. Chloride-Dissolve 1 gram in 15 cc. of water and add 2 cc. of nitric acid and 1 cc. of 0.1 N silver nitrate. Anv ttlrbiditv should not be greater than is produced by 0.02 mg. bf chloridk ion in an equal volume of solution containing the quantities of reagents used in the test. Phosphate-Dissolve 5 grams in 50 cc. of water, add 10 cc. of nitric acid, and nearly neutralize with ammonium h droxide. Add 50 cc. of ammonium molybdate solution, shake i t about 40" C.) for 5 minutes, and allow to stand one-half hour. Any precipitate formed should not be greater than is produced when a quantit of an alkali phosphate containing 0.05 mg. of phosphate (P&) is treated according to the above procedure. ArsenicDetermine on a 0.5-gram sample by the modified Gutzeit method. Calcium and Magnesium Precipitate-To the filtrate from the test for insoluble matter (without the washings) add 5 cc. of 4 per cent ammonium oxalate solution, 3 cc. of 10 per cent ammonium phosphate solution, and 10 cc. of ammonium hydroxide. If any precipitate forms on standing overnight, filter, wash thorouohly with water containing 2.5 per cent of NHs, ignite, and w&h. The weight should not be more than 0.0005 gram. Heavy Metals-Dissolve 2 grams in 25 cc. of water, add 2 cc. of hydrochloric acid, and boil gently for 10 minutes. Cool, neutralize to litmus with ammonium hydroxide, add 1 cc. of 0.1 N hydrochloric acid, dilute to 25 cc., and pass hydrogen sulfide through the solution. No brown color should appear. Iron-Add ammonium hydroxide to the solution obtained in the test for heavy metals until it is slightly alkaline. Any green color produced should not be greater than is produced by 0.04 mg. of iron in an equal volume of alkaline s d d e solution. CORRECTIONS FOR PUBLISHED SPECIFICATIONS
Replace the requirements and tests previously printed by the following: MAGNESIUM
TESTS Aciditv-Dissolve 4 grams in 50 cc. of water and titrate with normal dkali. Insoluble Matter and Ammonium Hvdroxide Prectvitate-Dissolve 10 grams in 100 cc. of water, idd ammoniun; hydroxide until the solution is alkaline to methyl red, boil for 1 minute, and digest on the steam bath for 1 hour. Filter through asbestos
(8)
Chloride-Add 0.5 gram of the sample to a mixture of 10 cc. of water and 3 cc. of nitric acid. METHANOL (6) REQUIREMENT Acetone, AZdehydesTo pass test (limit about 0.003 per cent acetone). TEsT Acetone, Aldehydes-Make comparison with 0.030 mg. of acetone. POTASSIUM IODATE
(3)
TEST Chloride and Bromide-Second sentence should read, "Treat the residue with 10 cc. of hot water and 1 cc. of dilute nitric 4),filter, and wash with 10 cc. of hot water." Make acid (I comparison with 0.10 mg. of chloride.
+
POTASSIUM BROMIDE
(3)
TEST Iron-Make
REQUIREMENTS Acidity-Not less than 34.0 per cent, nor more than 36.0 per cent as HtSOa. Insoluble Matter and Ammonium Hydroxide Precipitate-Not more than 0.010 per cent. Chloride (C1)-Not more than 0.002 per cent. Phosphate (PO4)-Not more than 0.001 per cent. ArsBnic (As)-Not more than 0.0005 er cent. Calcium and Magnesium Precipitate-kot more than 0.005 per cent. Heavy Metals-To pass test (limit about 0.0005 per cent lead). Iron (Fe)-Not more than 0.002 per cent.
OXIDE
TESTS
comparison with 0.01 mg. of iron. SODIUM BISULFATE FUSED
(5)
TEST Arsenic-Use
a sample of 0.50 gram.
SPECIFICATIONS PREVIOUSLY PUBLISHED (1) Committee on Analytioal Reagents, IND.ENQ.CHEM.,17, 756 (1935). (2) I b i d . , 18, 636, 759 (1926). (3) I b i d . , 19, 645 (1927). (4) I h i d . , 19, 1369 (1927). ( 5 ) Ibid., 20, 979 (1928). (6) Ibid., Anal. Ed., 1, 171 (1929). (7) Zbid., 2, 351 (1930). (8) I b i d . , 3, 221 (1931). RECEIVEDDecember 6, 1931. Presented in connection with the report of the Committee on Analytical Reagents a t the 81st Meeting of the American Chemical Society, Indianapolis, Ind., March 30 t o April 3, 1931.
