INDUSTRIAL AND ENGINEERING CHEMISTRY
760
Silica and Ammonium Hydroxide Precipitafe (SiOn, AlrOs, Fen03)Not more than 0.020 per cent. Nilrogen (N) (lotal a s nitrate, nitrite, and ammonia)-Not more than 0.001 per cent. Iron (Fe)-Not more than 0.002 per cent. Heavy Metals-To pass test (limit about 0.003 per cent silver).
TESTS General-Special care must be taken in sampling to obtain a representative sample and t o avoid absorption of water and carbon dioxide by the sample taken. 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. Sample Solution (Solution A)-Dissolve 100 grams of the sample in water free from carbon dioxide and make up to a volume of 500 cc. Sodium Hydroxide and Carbonate-Dilute 10 cc. of Solution A to 200 cc with carbon dioxide-free water, add 5 cc. of 10 per cent barium chloride solution, shake, and allow to stand for a few minutes. Titrate with normal hydrochloric acid, using phenolphthalein to determine the total hydroxide followed by methyl orange to determine the total alkalinity. The difference between the two titrations is the total carbonate, Chloride-Dilute 5 cc. of Solution A t o 50 cc. T o 10 cc. of the diluted solution in a test tuhe add 1 cc. of dilute nitric acid (1 volume of concentrated acid diluted to IO), and 1 cc. of 0.1 N silver nitrate solution. The turbidity should not be greater than t h a t produced by 0.02 mg. of chloride ion in 10 cc. of distilled water to which are added the quantities of acid and silver nitrate used with the sample. Sulfate-Dilute 50 cc. of Solution A with about 130 cc. of water. Neutralize with hydrochloric acid and add an excess of 1 cc. of strong acid. Heat to boiling and add 10 cc. of 10 per cent barium chloride solution. Allow to stand for 18 hours, filter, wash, ignite, and weigh. The weight should not be more than 0.0012 gram. Phosphate-Neutralize 50 cc. of Solution A with nitric acid, add an excess of 20 cc. of acid and make up to about 100 cc. Nearly neutralize with ammonium hydroxide (1part to 1 part of water) and add 50 cc. of ammonium molybdate solution. Shake the solution (at about 40' C.) for 5 minutes and allow to stand for 1 hour. Treat any precipitate formed by one of the standard methods for the determination of phosphate in the yellow precipitate. Silica and Ammonium Hydroxide Precipitate-Add an excess of sulfuric acid to 50 cc. of Solution A, evaporate, and drive offthe fumes of sulfuric acid until the residue is nearly dry. Cool, take up in about 100 cc. of water, boil, and add a slight excess of ammonium hydroxide. Filter, ignite, and weigh the precipitate. The weight should not be more than 0.0020 gram. Nilrogen-Dilute 10 CC. of Solution A with 50 cc. of ammonia-free water. Add about 0.5 gram of aluminium wire or foil in small pieces, protect from absorption of ammonia b y covering the flask or closing with a stopper carrying a long thin tube, and allow to stand for 3 or 4 hours, agitating occasionally. Dilute with water to 100 cc., decant or pour off 50 cc. of the clear liquid, and add 2 cc. of Nessler's solution. The color produced should not be greater than t h a t in a blank made with a quantity of ammonium salt corresponding to 0.01 mg. of nitrogen. Iron-Neutralize 25 cc. of Solution 4 with hydrochloric acid, add 1 cc. excess of acid and 1 gram of potassium nitrate. Transfer to a color comparison tube, add 2 cc. of 5 per cent ammonium thiocyanate solution, and stir well. Compare with a solution of the same volume containing the same quantities of hydrochloric acid, potassium nitrate, and ammonium thiocyanate to which standard ferric chloride solution is carefully added from a buret until the tints match. Heavy Metals-To 26 cc. of Solution A add a slight excess of hyclrochloric acid; neutralize with ammonium hydroxide, add 5 drops of glacial acetic acid and saturate with hydrogen sulfide. The solution should not be darker than a n equal volume of water containing 0.15 mg. of silver ion and 5 drops of glacial acetic acid, after saturation with hydrogen sulfide.
Sodium Oxalate REQUIREMENTS M o i s l u r e N o t more than 0.010 per cent Insoluble Matter-Not more than 0.010 per cent. Chloride (CI)-Not more than 0.002 per cent. Sulfate (SOli)-Not more than 0.002 per cent. h'eulraliiy-To pass test (limit of alkalinity equivirlent to 0.021 per cent NalCOa, limit of acidity equivalent to 0.022 per cent NaHCiOd). Iron (Fe)-To pass test (limit about 0 001 per cent.) Polassium (K)-Not more than 0.01 per cent. Substances Darkened by Hot Sulfuric Acid-To pass test.
Moislure-Dry 10 grams of the sodium oxalate t o constant weight at 105" to 110' C. The loss should not exceed 0.0010 gram. Insoluble Matter-Dissolve 10 grams in 400 cc. of water and allow to stand on the steam bath for one hour. Filter on asbestos in a Gooch crucible, wash, dry a t 105' t o 110' C., and weigh. The residue should not weigh more than 0.0010 gram. Chloride-Ignite 2.5 grams to carbonate. Dissolve in 50 cc. of water, neutralize with nitric acid, and filter if necessary. Make up to 100 cc. T o 10 cc. in a test tube add 1 cc. of dilute nitric acid (1 volume of concentrated acid diluted to 10) and 1 cc. of 0.1 A' silver nitrate solution. The turbidity should not be greater than t h a t produced by 0.005 mg. of chloride ion in 10 cc. of distilled water to which are added the quantities of acid and silver nitrate used with the sample. Sulfate-Ignite 10 grams in a platinum crucible, using an alcohol flame t o avoid contamination from a gas flame. Dissolve the residue in 50 cc. of water, neutralize with hydrochloric acid and add an excess of 1 cc. of dilute acid (10 per cent HCI). Make to about 100 cc., heat to boiling, add 5 cc. of 10 per cent barium chloride solution, and allow to stand for 18 hours. Auy precipitate formed should not weigh more than 0.0005 gram. Neutrality-Dissolve 2 grams in 150 cc. of water free from carbon dioxide. Add 0.2 cc. of phenolphthalein solution and boil the solution in a flask of resistant glass for 10 minutes while passing through i t a current of air free from carbon dioxide. Prepare a color standard by adding 0.2 cc of phenolphthalein solution to 150 cc. of carbon dioxide-free water, containing 10 cc. of 0.1 N sodium hydroxide solution, and diluting 6 cc. of this red liquid to 100 cc. with carbon dioxide-free water. Titrate the sodium oxalate solution with 0.01 N acid or alkali as required t o bring its color to match that of the prepared standard. Not more than 0.8 cc. of 0.01 N acid, or 0.4 cc. of 0.01 N alkali solution should be required. Iron-Ignite 5 grams t o carbonate and dissolve the residue in 25 cc. of water. Neutralize with hydrochloric acid and add an excess of 1 cc. of strong acid. Add 1 drop of bromine and boil until nearly all color is gone. After the solution has cooled to room temperature make to 50 cc and add 5 cc. of thiocyanate solution (either potassium, sodium, or ammonium, 2 grams in 100 cc.). The color should not he more than is produced by 0.05 mg. of iron in 50 cc. of solution containing the same excess of acid and the same quantity of thiocyanate as the sample. Potassium-Ignite 5 grams of the salt t o carbonate in a platinum crucible, dissolve in a small amount of water, and neutralize the solution with hydrochloric acid using a suitable indicator. Evaporate this solution t o dryness on the steam bath and.redissolve the residue in 15 cc. of water (to concentrate the solution and remove any free acid). Add 5 cc. of sodium cobaltinitrite solution and allow to stand overnight. (The sodium cobaltinitrite solution is made by dissolving 25 grams NaNOp in 50 cc. of water and then adding 15 cc. of 6 N HCzH302 and 2.5 grams of Co(CzH30Jn.4HrO or an equivalent amount of nitrate or chloride. The solution is allowed to stand overnight, filtered, and diluted to 100 cc.) Any precipitate formed should not be greater than is produced b y an amount of potassium chloride equivalent to 0.50 mg. K dissolved in 15 rc. of water, treated with 5 cc. of sodium cohaltinitrite solution and allowed to stand overnight. Subslances Darkened by Hot Sulfuvic Arid-Heat 1 gram in a recently ignited test tube with 10 cc. of sulfuric acid until the appearance of fumes of sulfur trioxide. The acid should not acquire more than a faint brownish tinge.
Report of A. C. S. Committee on Guaranteed Reagents During the year 1924-25 the committee revised specifications published' in 1921 for reagent sulfuric, nitric, and hydrochloric acids and ammonium hydroxide. Slight changes were adopted in specifications for sodium and potassium hydroxides and for sodium oxalate, which had been transmitted to the Committee on Pure Products for Research of the International Congress of Pure and Applied Chemistry. Specifications were prepared for Ammonium oxalate Ammonium thiocyanate Barium chloride Iodine
Oxalic acid Potassium dichromate Silver nitrate
The above-mentioned specifications are transmitted herewith t o be published for comment, as proposed specifications for the different reagents.' W. D COLLINS, Chawman H. V. FARR
TESTS Blank tests 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 insoluhle material would interfere.
Vol. 17, No. 7
ITHIS JOURNAL, 13. 736 (1921). Page 756, this issue.
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ROSIN G . C. SPENCER E D W A R D WICHERS JOSEPH
