I S D USTRIAL A N D EYGINEERISG CHEMISTRY
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The number of universities, colleges, and schools of engineering and agriculture furnishing data was 121 (139); the number of medical schools was 24 (32), and the number of schools of pharmacy was 10 (13). The total number of graduate research students in chemistry reported was 1763 (1700) distributed in various fields, as shown in Table I. Of these, 970 (563), or 55 (52) per cent, were reported by 13 (12) universities and colleges, including all their departments; 1234 (1193), or 69 (70) per cent, were reported by 25 (25) universities and colleges; 1412 (1357), or 80 (80) per cent, were reported by 40 (40) unirersities and colleges. In the group of 13 (12) universities and colleges which reported 55 (52) per cent of the total number, the highest number reported by any individual institution was 137 (122), followed by 101 (115) for the next competitor; the third and
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fourth reported 99 (93) and 89 (91), respectively. The lowest number of research students reported by any one institution in that group was 51 (47). The distribution of these 1763 (1700) students among the various fields of research is of interest. The physicochemical group (general, colloid, catalysis, subatomic, electrochemistry, photochemistry) appears to attract more students than any other; 544 (460) research students are working in this group. Organic chemistry comes next with 430 (420) research students. It is interesting to note that 44 (41) per cent of these are working in the aliphatic series. The medical group (physiological, pharmacological, pharmaceutical, nutrition, and bacteriological) is unexpectedly large, 333 (276) research students being a t work in those fields. Industrial and engineering chemistry comes fourth with 184 (203) research students, and inorganic chemistry fifth with 86 (101) workers.
Recommended Specifications for Analytical Reagent Chemicals’ Hydrochloric, Nitric, Oxalic, and Sulfuric Acids, Ammonium Hydroxide, Ammonium Oxalate, Ammonium Thiocyanate, Barium Chloride, Iodine, Potassium Dichromate, Potassium Hydroxide, Silver Nitrate, Sodium Hydroxide, Sodium Oxalate By W. D. Collins, H. V. Farr, Joseph Rosin, G . C. Spencer, and Edward Wichers COMMITTEE
ON
GUARANTEED REAGENTS, AMERICAN CHEMICAL SOCIGTY
T
HE specifications given below are intended to Serve for re-
agents to be used in careful analytical work. The limits and tests are based On published work and On the experience Of members of the committee and others in the examination Of reagent chemicals on the market. Suggestions for improvement of the specifications will be welcomed by the committee. The requirements ’IJecified are Of t’vo 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. In 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. 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. Specifications for sulfuric, nitric, and hydrochloric acids, and for ammonium hydroxide published by the Committee on Guaranteed Reagents and Standard Apparatus in 1921, have been only slightly modified for the present report.
Acid, Hydrochloric REQUIREMENTS AppeavanceColorless and free from suspended matter or sediment. Strenglh-Not less than 35 per cent by weight of HCI. Nonwolafile Matter-Not more than 0.0005 per cent. Sulfafe (Sod)-Not more than 0.0002 per cent. Free Chlorine (C1)-To pass test (limit about 0.0002 per cent). S u l j f e (S0a)-Not more than 0.003 per cent. Arsenic (As)-Not more than 0.00001 per cent. Iron (Fe)-Not more than 0.0001 per cent. Heasy M e f a l s T o pass test (limit about 0.0005 per cent leadJ. TESTS Blank tesls must be made on water and all reagents used in the methods unless the directions provide for elimination of errors due t o impurities. 1 Presented in connection with the report of the Committee on Guaranteed Reagents at the 69th Meeting of the American Chemical Society, Baltimore, Md., April 6 to 10,1925.
Solutions of the sample must be filtered for tests in which insoluble material
woul~$:~~~~-xrin the material in origrinal container, pour cc, into a test tube (I50 mm. by 20 mm.), and compare with distilled water in a similar tube. The liquids should be equally clear and free from suspended matter and on looking across the columns by transmitted light there should be no apparent differencein color between the two liquids. Assay-Tare a small glass-stoppered Erlenmeyer Bask containing 15 cc. of water. Quickly introduce about 3’cc. of the acid, stopper, and weigh. Titrate with standard sodium hydroxide solution. Nonaolafile Matter-Evaporate S5 cc. of the acid to dryness in platinum afteraddition of a drop of sulfuric acid, ignite at cherry redness for 5 minutes, cool, and weigh. The residue should not weigh more than 0.0005 gram. Sulfale-Add 0.01 gram of sodium carbonate to 20 cc. of the acid, evaporate to dryness, take up with water, filter, and make u p 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 obtained in an equal volume of distilled water containing 0.01 gram sodium carbonate neutralized with hydrochloric acid, 0.05 mg. of sulfate (SO4), and the quantities of hydrochloric acid and barium chloride used with the sample. Free C h l o v i n e T o 25 cc. of the sample add 25 cc. of freshly boiled water and cool; add 2 drops of 2 per cent potassium iodide solution and 1 cc. of carbon disulfide, and mix. The carbon disulfide should not acquire a pink color in half a minute. The potassium iodide should be free from iodate. Su&‘e--Add 0.05 cc. of 0.1 Niodine solution and a few drops of starch solution to 50 cc. of water, and then add 5 cc. of the sample previously diluted with 50 cc. of water. The mixture should retain a blue color after mixing. Arsenic-Determine in 20 cc. of the sample by the Gutzeit or the 3Iarsh-Berzelius method. Special care in making blank tests is necessary in this determination. Iron-To 8 5 cc. of the sample add about 0.05 gram potassium nitrate and evaporate t o a volume of about 2 cc. Wash into 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 1 cc. of hydrochloric acid and the quantities of potassium nitrate and ammonium thiocyanate used in the test, to which standard ferric chloride solution is carefully added from a buret until the tints match. Heavy Melals-Evaporate 10 cc. of the acid to dryness, add 5 drops of hydrochloric acid, dilute to 50 cc., and saturate with hydrogen sulfide. No color should be observed.
Acid, Nitric REQVIREMENTS Appearance-Colorless and free from suspended matter or sediment. Strenglh-From 6s to 70 per cent by weight of HX’O8.
INDUSTRIA 1; L4LYD EYGi‘XEERING CHE&ISTRY
July, 1925
Nonvolatile Mafter-Not more than 0.0005 per cent. Sulfate (SO4)-Not more than 0.0002 per cent. Chloride (Cl)-To pass test (limit about 0.00007 per cent) Arsenic (As)-Not more than 0.000003 per cent. Heavy Mefals-To pass test (limit about 0.0005 per cent lead, about .0.0001per 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 to impurities. Solutions of the sample must be filtered for tests in which insoluble material would interfere. Appearance-Mix the material in original container and transfer 10 cc. to a test tube (150 mm. by 20 mm.), and compare with distilled water in a similar tube. The liquids should be equally clear and free from suspended matter, and on looking across the columns by transmitted light there should be no apparent difference in color between the two liquids. Assay-Tare a small glass-stoppered Erlenmeyer flask containing 15 cc. of water. Quickly introduce about 2 cc. of the acid, stopper, and weigh. Titrate with standard sodium hydroxide solution. Konwolatile Matfer-Evaporate 70 cc. of the acid to dryness in platinum, ignite a t cherry redness for 5 minutes, cool, and weigh. The residue should not weigh more than 0.0006 gram. Sulfate-Add 0.01 gram sodium carbonate to 20 cc. of the acid, evaporate t o dryness, take up with water, filter, and make up to a volume of 10 cc. in a test tube. Add 1 cc. hydrochloric acid (1 volume strong acid in 20) a n d 1 cc. of 10 per cent barium chloride solution. The turbidity after 10 minutes should not be greater than is obtained in an equal volume of distilled water containing 0.01 gram sodium carbonate neutralized with hydrochloric acid, 0.05 mg. of sulfate (Sod) and the quantities of hydrochloric acid a n d barium chloride used with the sample. Chloride-Dilute 5 cc. of the acid with an equal volume of water and add 1 cc. of 0.1 N silver nitrate solution. The turbidity should not be greater than that produced by 0.005 mg. of chloride ion in 9 cc. of water to which are added 1 cc. of dilute nitric acid (1 volume diluted to 10) and 1 cc. of 0.1 N silver nitrate solution. Arsenic-Mix 70 cc. of the acid with 5 cc. of sulfuric acid and evaporate until fumes are evolved. .4 second or third evaporation to fumes after dilution may be necessary to remove all nitrate. Cool, and determine arsenic by the Gutzeit or the Marsh-Berzelius method. Special care in making blank tests is necessary. Heovy Metals-Dilute 7 cc. of the acid to 50 cc., make alkaline with ammonium hydroxide, and add 5 cc. of hydrogen sulfide water. N o brown color should be observed. If green color is observed i t should not be greater than is produced when the test is applied to 50 cc. of distilled water containing 0.01 mg. of iron.
Acid, Oxalic REQUIREMENTS Insoluble Matter--Not more than 0.010 per cent. Nonvolatile Matter-Not more than 0.020 per cent, Chloride (Cl)-Not more than 0.002 per cent. Sulfate (Sod-Not mort: than 0.002 per cent. Xilrogen Compounds (nit.rate, ammonia)-Not more than 0,001 per cent as N . Heavy Metals-To pass test (limit about 0.0005 per cent lead, about 0.0002 per cent iron). Subsfances Darkened by Not Sulfuvic Acid-To pass test.
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 insoluble material would interfere. Insoluble Matter-Dissolve 10 grams in 200 cc. of hot water and allow to stand on the steam bath for one hour. Filter on asbestos in a Gooch crucible, wash, dry a t 105” to 110’ C . , and weigh. The residue should not aeigh more than 0.0010 gram. Nonvolalile Matter-Ignite 5 grams and weigh the residue. The weight should not exceed 0.0010 gram. Chloride-Dissolve 5 grams in 7 5 cc. of water, a d d 15 cc. of nitric acid a n d 1 cc. 01 0.1 K silver nitrate. The turbidity should not be greater than that produced by 0.1 mg. of chloride ion in 75 cc. of water after the addition of the quantities of nitric acid and silver nitrate added to the solution of the sample. Sulfate-Dissolve 10 grams in 200 cc. of hot water, add 1 cc. of hydrochloric acid and 5 cc. of 10 per cent barium chloride solution; allow to stand overnight, filter, a n d weigh. The weight of the precipitate should not exceed 0.0006 gram. Nitrogen Compounds-Dissolve 2 grams in 20 cc. of water in a flask, add 40 cc. of 10 per cent sodium hydroxide solution, cooling with ice while adding the sodium hydroxide. Add about 0.5 gram of aluminium wire or foil in small pieces, protect from absorption of ammonia by covering the flask or closing with a stopper carrying a long thin tube, and allow to stand for 3 t o 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
757
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. Heavy Metals-Dissolve 2 grams in 50 cc. of water, saturate with hydrogen sulfide, and add 2 cc. of ammonium hydroxide. No darkening should be produced either before or after the addition of ammonium hydroxide. Subslances Darkened by Hot Sulfuric Acid-Heat 1 gram of the acid with 10 cc. of sulfuric acid in a previously ignited test tube until fumes of so8 are evolved. At most, only a faint coloration should be produced.
Acid, Sulfuric REQUIREMENTS Appearance-Colorless and free from suspended or insoluble matter when received and after diluting to 2 N concentration. Strengfh-Not less than 94 per cent by weight of H2SOd. Nonvolatile Maffer-Not more than 0.0006 per cent. Chloride ((21)-Not more than 0.00006 per cent. Nifrate (NOs)-To pass test (limit about 0.0002 per cent). Ammonium (“&)--Not more than 0.0003 per cent. Substances Oxidisable by Permanganate-To pass test (limit a b o u t 0.0005 per cent as SO,). Arsenic (As)-Not more than 0.000003 per cent. Heavy Metals-To pass test (limit about 0.0005 per cent lead, 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 to impurities. Solutions of the sample must be filtered for tests in which insoluble material would interfere. Appearance--1Mix the material in original container and transfer 10 cc. to a test tube (150 mm. by 20 mm.). Compare with distilled water in a similar tube. The liquids should be equally clear and free from suspended matter, and on looking across the columns by transmitted light there should be no apparent difference in color between the two liquids. Dilute a portion of the acid with water until 2 N, and compare a s before. N o difference in turbidity should be observed. Assay-Titrate a weighed portion of the acid, after suitable dilution, with standard sodium hydroxide solution. Nonvolatile Matter-Evaporate 53 cc. of the acid to dryness in platinum. ignite a t cherry redness for 5 minutes, cool, and weigh. The residue should not weigh more than 0.0005 gram. Chloride-Dilute 5 cc. of the acid to 50 cc. and cool. Add 1 cc. of nitric acid (1 volume diluted to IO) and 1 cc. of 0.1 N silver nitrate solution. The turbidity should not be greater than is produced by 0.005 mg. of chloride ion in 50 cc. of water to which are added 1 cc. of dilute nitric acid (1 volume diluted to 10) and 1cc. of 0.1 N silver nitrate solution. Nitrate-Dilute a sample of the acid with an equal volume of water and overlay 10 cc. of the cooled liquid upon diphenylamine solution (0.5 gram in 100 cc. sulfuric acid and 20 cc. water). A blue color should not appear a t the zone of contact within one hour. Ammonium-Dilute 6 cc. of the acid with 90 cc. of water, render alkaline with sodium hydroxide, and add 1 cc. of Nessler’s reagent. No more color should develop than is caused by 0.03 mg. of NH4 in the same volume of water with the quantities of sodium hydroxide and Nessler’s solution used in the test. Substances Oxidizable by Permanganate-Dilute 20 cc. of the acid with 60 cc. of water, cool to 2 5 O C., and add 0.05 cc. of 0.1 N potassium permanganate. The mixture should remain pink for not less than 5 minutes. Arsenic-Add 3 cc. of nitric acid to 55 cc. of the acid and evaporate to about 10 cc. A second or third evaporation to fumes after dilution may be necessary to remove all of the nitrate. Cool, dilute the residue with 40 cc. of water, and determine arsenic by the Gutzeit or the MarshBerzelius method. Special care in making blank tests is necessary in this determination. Heavy Metals-Dilute 5 cc. of the acid to 50 cc., saturate with hydrogen sulfide, and make alkaline with ammonium hydroxide. No brown color should be observed. If a green color is observed it should not be greater than is produced when the test is applied to 50 cc. of distilled water containing 0.01 mg. of iron.
Ammonium Hydroxide REQUIREMENTS Appearance-Colorless and free from suspended matter or sediment. Sfrengfh-Not less than 27 per cent by weight of NHa. Nonvolatile Matter-Not more than 0.005 per cent. Carbon Dioxide (Cod-Not more than 0.002 per cent. Total Sulfur (as Sod-Not more than 0.0003 per cent. Chloride (CI)-To pass test (not more than 0.00005 per cent). Pyridine-To pass test (not more than a trace). Substances Reducing Permanganale-To pass test. 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 d u e t o impurities.
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I-VDCSPRIAL A S D ESGI,VEERISG CHEMISTRY
Solutions of the sample must be filtered for tests in which insoluble material would interfere. Agpearance-Mix the material in original container and pour 10 cc. into a test tube (150 mm. by 20 mm.), and compare with distilled water in a similar tube. The liquids should be equally clear and free from suspended matter, and on looking across the columns by transmitted light there should be no apparent difference in color between the two liquids. Assay-Tare a small glass-stoppered Erlenmeyer flask containing 15 cc. of water. Quickly add about 2 cc. of the ammonium hydroxide, stopper, and weigh. Titrate with normal acid, using methyl orange as indicator, Sonvolatile Muller-Evaporate 45 cc. of the sample to dryness, ignite a t cherry redness for 5 minutes, cool, and weigh. The residue should not weigh more than 0.0020 gram. Carbon Dioxide-To 10 cc. of the sample a d d 5 cc. of a saturated solution of barium hydroxide. The turbidity should not be greater than is produced when the same quantity of barium hydroxide solution is added to 10 cc. of water (free from carbon dioxide) containing 0.5 mg. of sodium carbonate. Tolnl Sulfur-To 20 cc. of the sample add 0.01 gram sodium carbonate and evaporate to 5 cc. Add a drop of bromine water (or sufficient to impart a slight color to the solution) and evaporate to dryness, take up in a slight excess of dilute hydrochloric acid, and again evaporate to dryness. Take up in a few cubic centimeters of water, filter, and make to a volume of 10 cc. in a test tube. Add 1 cc. of dilute hydrochloric acid (1 volume of strong acid in 20) and 1 cc. of 10 per cent barium chloride solution. The turbidity produced after 10 minutes should not be greater than is obtained in an equal volume of distilled water containing 0.01 gram sodium carbonate neutralized with hydrochloric acid, 0.05 mg. of sulfate (SOa), and the quantities of hydrochloric acid and barium chloride used with the sample. Chloride-To 10 cc. of the sample add 0.005 gram of sodium carbonate and evaporate t o dryness. Take up with 8 cc. of water, and add 1 cc. of dilute nitric acid (1 volume diluted t o 10) and 1 cc. of 0.1 X silver nitrate solution The turbidity should not be greater than that produced by 0.005 mg. of chloride ion in 8 cc. of water to which have been added the quantities of nitric acid and silver nitrate used with the sample. Pyridine-Dilute 25 cc. of the sample with 25 cc. of water and nearly neutralize with about 25 per cent sulfuric acid, using methyl orange as an indicator. Stir briskly and note the odor. No more than a very faint odor of pyridine should be obtained. Substances Reducing P e r m a n g a n a t ~ - D i l u t e3 cc. of the sample with 5 cc. of water and add 50 cc. of approximately 2 A ' sulfuric acid, Add 1 drop of 0.1 N potassium permanganate. Heat to boiling and keep a t this temperature for 5 minutes. The pink color should not be entirely discharged. Heaoy Melals-Dilute 10 cc. of the sample to 50 cc. and pass hydrogen sulfide gas through the solution. No brown color should be observed. Any green color should not be greater than is obtained by passing hydrogen sulfide through 50 cc. of an ammoniacal solution containing 0.01 mg. of iron.
Ammonium Oxalate REQUIREMENTS Insoluble Matler-Not more than 0.010 per cent. Sonvolatile Matter-Not more than 0.020 per cent. Chloride (C1)-Not more than 0.02 per cent. Sulfale (SO&-To pass test (limit about 0.006 per cent). Heavy Metals-To pass test (limit about 0.0005 per cent lead, about 0.0002 per cent iron). TESTS Blank lesls 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 material would interfere. Insoluble Muller-Dissolve 10 grams in 200 cc. of hot water and allow to stand on the steam bath for one hour. Filter on asbestos in a Gooch crucibte, wash, dry a t 105' to 110' C., and weigh. The residue should not weigh more than 0.0010 gram. hTonoolalileMatter-Ignite 5 grams a t the lowest possible temperature for volatilization of t h e ammonium salt. The residue should not weigh more than 0.0010 gram. Chloride-Dissolve 2 grams in 50 cc. of water, add 10 cc. of nitric acid and 1 cc. of 0.1 N silver nitrate solution. The turbidity should not be greater than t h a t produced by 0.04 mg. of chloride ion in 50 cc. of water when the same quantities of nitric acid and silver nitrate are added. Sulfate-Dissolve 5 grams in 250 cc. of hot water, add 5 cc. of hydrochloric acid and 5 cc. of 10 per cent barium chloride. Allow to stand overnight. No precipitate should form. Heavy Melals-Dissolve 2 grams in 50 cc. of water, saturate with hydrogen sulfide, and add 2 cc. of ammonium hydroxide. No darkening should be produced either before or after the addition of ammonium hydroxide.
Ammonium Thiocyanate REQLXREMENTS ..lppearance-Colorless or white crystals. Insoluble Matter-Not more than 0.010 per cent. A'onvolatile .Walter-h'ot more than 0.025 per cent.
Chloride (CI)-Not Srclfale (SOI)-Not Heavy Melals-To 0.0001 per cent iron).
Vol. 17, No. 7
more than 0,020 per cent. more than 0.005 per cent. pass test (limit about 0.0005 per cent lead, about TESTS
Blank tesls 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 material would interfere. Insoluble Matler-Dissolve 10 grams in 100 cc. of hot water, allow to stand on the steam bath for one hour, filter through asbestos in a Gooch crucible, wash, and dry a t 105' to 110' C. The residue should not weigh more than 0,0010 gram. Nonvolatile Muller-Ignite 4 grams a t the lowest possibie temperature. The residue should not weigh more than 0.0010 gram. Chlovide-To a solution of 4 grams of copper sulfate (free from chloride) in 20 cc. of water add 30 cc. of a saturated solution of sulfur dioxide and 1 gram of the thiocyanate dissolved in 10 cc. of water. Boil about 1 minute, cool quickly, and filter. Add 10 cc. of the sulfur dioxide solution to the filtrate. If additional precipitation takes place filter and add more sulfur dioxide to the filtrate. To the clear filtrate add 5 cc. of nitric acid and 0.5 cc. of 0.1 A' silver nitrate solution. The turbidity should not be greater than is produced in the same volume of water containing 0.20 mg. of chloride ion, the quantity of sulfur dioxide used in the test, enough copper sulfate to match the color of the test solution, and the quantities of nitric acid and silver nitrate used in the test. Sulfate-Dissolve 10 grams in 100 cc. of hot water, add 1 cc. of hydrochloric acid and 5 cc. of 10 per cent barium chloride solution; allow to stand overnight. If any precipitate is formed, filter and weigh. The weight of the precipitate should not exceed 0.0012 gram. Heavy Melals-Dissolvc 2 grams in 20 cc. of water, add 1 cc. of ammonium hydroxide and 5 cc. of hydrogen sulfide water. No darkening should be observed.
Barium Chloride REQUIREMENTS Insoluble Mailer-Not more than 0.010 per cent. S i l r a ! e and Chlorate-To pass test (limit about 0.005 per cent as NOa). illkali Salfs-Not more than 0,050 per cent as sulfates. Strontium and Calcium Chlorides-Not more than 0.10 per cent. Heavy Metals-To pass test (limit about 0.0006 per cent lead, about 0,0002 per cent iron). TESTS Blank lesls 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 material would interfere. Insoluble Maller-Dissolve 10 grams in 100 cc. of water and beat on the steam bath for one hour. Filter through asbestos, wash thoroughly, and dry a t 105' to 110' C. The residue should not weigh more than 0,0010 gram. Xilrale and Chlorate-Dissolve 2 grams in 20 cc. of water, add 1 cc. of concentrated sulfuric acid to precipitate the barium, and filter. Overlay 10 cc. of the filtrate on 10 cc. of diphenylamine solution (0.5 gram in 100 cc. of sulfuric acid and 20 cc of water). No blue ring should develop between the two solutions in 20 minutes. .llkali 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 .V sulfuric acid, cool, make up to 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 noL exceed 0.0010 gram. Slron!ium and Cal'ium Chlorides-Treat 2 grams of the finely powdered sample with 20 cc. of absolute alcohol. Allow to stand for 30 minutes with occasional shaking. Filter, evaporate the filtrate, and ignite gently. The residue should not weigh more than 0.0020 gram. Heavy Metals-Dissolve 2 grams in 20 cc. of water, add 2 drops of hydrochloric acid, pass hydrogen sulfide, and make alkaline with ammonium hydroxide, No darkening should occur before or after the addition of ammonium hydroxide.
Iodine REQUIREMENTS Form-Sublimed iodine. A-onvolatile Aialler-Not more than 0.020per cent. Chlorine and Bromine-To pass test (limit about 0.005 per cent as el). 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 insoluble material would interfere. Sonaolalile .Waltev-Evaporate 5 grams on the steam bath. The residue should not weigh more than 0.0010 gram.
July, 1925
759
Clilorinc a?id Bromine-Triturate 5 grams of the powdered iodine with 25 cc. of water and let stand for one-half hour with frequent stirring Filter, and t o 20 cc. of the filtrate add dilute sulfurous acid, drop by drop, until the color of iodine is just discharged. Add 1 cc. of 10 per cent ammonium hydroxide and 1 cc. of 0.1 AT silver nitrate. Filter and t o the clear filtrate add 2 cc. of nitric acid. The turbidity should not be greater than is produced hy 0.2 mg. of chloride ion in 20 cc. of water t o which are added the quantities of ammonium hydroxide, silver nitrate, and nitric acid used with the sample.
Potassium Dichromate REQUIREMEXTS Insoluble Matier-Not more than 0.010 per cent. Chlovide (CI)-To pass test (limit about 0.005per cent). 3uIfaie (SOI)--TO pass test (limit about 0.005 per cent). .4luminium (Al)--Sot more than 0.002 per cent. Calcium (Ca)-h-ot more than 0.005 per cent. Sodiiim (Pia)-To pass test (limit about 0.010 per cent).
TESTS Blank t e s t s must be made on water a n d all reagents used i n 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 material would interfere. Insoluble .\faller-Dissolve 10 grams in 100 cc. of warm water. filter through asbestos, wash until the washings are colorless, d r y at. 105' to l l O c C., and weigh. T h e weight of the residue should not exceed 0 0010 gram. Ciilorid+Dissolve 1 gram in 20 cc. of water, add 10 cc. of nitric acid, heat to about 50' C., and add a few drops of 0.1 S silver nitrate. N o turbidity should develop. Sulfale-Dissolve 10 grams in 230 cc. of water, add 8 cc. of hydrochluric acid and 10 cc. of 10 per cent barium chloride solution, and :illow t o stand overnight. N o precipitate should form, Aluminium-Dissolve .j grams in 50 cc. of water, and add ammonium hydroxide until the liquid smells slightly of ammonia; heat on the steam bath until the odor of ammonia has disappeared and allow to stand overnight. Any precipitate formed should not be greater than is formed nhen the sxme test is applied to an equal volume of water containing 0.10 mg. of aluminium. Coliium-Dissolve 5 grams in 50 cc of water. Add a sllght excess of ammonium hydroxide and ii cc. of ammonium oxalate solution (4 grams in 100 cc.). Any precipitate formed on standing overnight should not be greater t h m is formed in a slightly ammoniacal solution of equal rolume containing 0.25 mg. of calcium (Ca), a n d 5 cc. of ammonium oxalate solution. Sodium-'% 10 per cent solution tested with a platinum wire in the flame should give no distinct yellow color to the flame.
Potassium Hydroxide REQUIREMENTS Polassium Hydroxide (KOH)--Not less than 85 per cent. Poiassium Carbonate (KLOs)-Not more than 3 per cent. Chloride (CIj-Not more than 0.010 per cent. Sulfate (Sod--Not more than 0.005 per cent. Phosphale (PO;)-Not more than 0 005 per cent. ' .Sili(a a,id Ammonium .Hydroxide Pvecipitaie ( S O ? , ALOs, Fe.O,i-Kot more than 0.020 per cent. .\'z!vogen (h') (tolal as nzirate, nitrile, and ammonia)-A'ot more than 0.001 per cent. Iron (Fe)-Not more than 0.002 per cent. H e m s .lfe/als-To pass test (limit about 0.003 per cent silver).
TESTS General-Special care must be taken in sampling to obtain .i representative sample and t o avoid absorption of water and carbon dioxide by the sample taken. B l a n k 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 material would interfere. Sample Solution (Solufion ,-l)---Dissolve 100 granis of the sample in water free from carbon dioxide and make up t o a volume of 500 cc. Polassium Hydroxide awd Carbonate-Dilute 10 cc. of Solution .4 t o 200 cc. with carbon dioxide-free water, add 5 cc. of 10 per cent Llarium chloride solution, shake, and allow to stand for a few minutes. 'Titrate with normal hydrochloric acid using phenolphthalein t o determine the total hydroxide, followed by methyl orange to determine the total alkalinity. The difference between the two titrations is the total carbonate. Ciiloride-Dilute 2 cc. of Solution A t o 50 cc. To 10 cc. oi the diluted solution in a test tube add 1 cc. of dilute nitric acid (1 volume of concentrated acid diluted t o lo), and 1 cc. of 0.1 Y silver nitratesolution. The turbidity should not be gre;zter than that 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. Sulfale-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 t o boiling and add 10 cc. of 10 per cent barium chloride solution. Allow to
stand for 16 hours; filter, wash, ignite, and weigh. The weight should not be more than 0.0012 gram. Phosphale-Neutralize 50 cc. of Solution A with nitric acid, add an excess of 20 cc. of acid, and make up t o about 100 cc. h-early neutralize with ammonium hydroxide (1 part t o 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 one hour. Treat any precipitate formed by one of the standard methods for thedetermination of phosphate in theyellowprecipitate. Silica and .4mmonium Hydroxzde Preirpitaie-Add an excess of sulfuric acid to 50 cc. of Solution A , evaporate, and drive off the 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 aeight should not be more than 0.0020 gram. Sitrogen-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 by 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 a i t h water to 100 cc., decant or pour off 50 cc. of the c l e u liquid, and add 2 cc. of ATessler's solution. The color produced should not be gr6ater than that in a blank made with a quantity of ammonium salt corresponding t o 0.01 mg. of nitrogen. Iron-Neutralize 25 cc. of Solution A with hydrochloric acid, add 1cc. excess of acid and 1 gram of potassium nitrate. Transfer to a colorcomparison tube, add 2 cc. of 5 per cent ammonium thiocyanate solution, and stir well. Compare with il 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. Hearty Metals-To 25 cc. of Solution .A add a slight excess of hydrochloric acid; neutralize with ammonium hydroxide, add 5 drops of glacial acetic acid, and saturate with hydrogen sulfide. The solution should not be darker than an equal volume of water containing 0.15 mg. of silver ion and 5 drops of glacial acetic acid. after saturation with hydrogen sulfide.
Silver Nitrate REQUIREMENTS f?isolubie .Ifaiter-To pass test. Chloride (CIj-To pass test (limit about 0.002 per cent). Free .icid-To pass test. Subsiaitres S o l Precipitaied by Hydrochloric Acid-Not more than 0,010 per cent. A'ulJale (Sod)-Not more than 0,002 per cent.
TESTS Blank l e s f s must he 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 material would interfere. fitsoluble Sfaterial-Dissolve 10 grams in 10 cc. of water. ATo insoluble crystalline material should be observed. Chlovide-Dilute the above solution with 90 cc. of water. h-o turbidity or opalescence should appear. Free Arid-The solution from the preceding test should not turn blue litmus paper red. Suhslan:es S o t Precipitaled by Hydrochloric .Acid-Dilute the solution obtained in the test for chloride with about 200 cc. of water, heat to boiling, and add hydrochloric acid to completely precipitate the silver. Allow to stand overnight, filter, and wash. Evaporate the filtrate t o dryness, add 3 drops of hydrochloric acid and 10 cc. of water. Heat and filter. Evaporate the resulting filtrate to dryness, dry a t 110' C., and weigh. Run a blank test and deduct the weight obtained from that obtained in the test of the sample. Sulfale-Dissolve 5 grams in 100 cc. of water, heat to boiling, precipitate with 10 cc. of hydrochloric acid, and allow to stand overnight. Filter and wash the precipitate with 50 cc. of hot water. Add to the filtrate about 0.01 gram of sodium carbonate, and evaporate to dryness on the water bath. Take up the residue in water, filter, and make to 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 should not be greater than is obtained in a n equal volume of water containing 0.01 gram of sodium carbonate neutralized with hydrochloric acid, 0.1 mg. of sulfate (Sod,and the quantities of hydrochloric acid and barium chloride used with the sample. The effect of sulfate in the distilled water and hydrochloric acid may be eliminated by evaporating 1.50 cc. of the water with 10 cc. of hydrochloric acid and 0.01 gram of sodium carbonate and treating the residue to m i k e the standard of turbidity.
Sodium Hydroxide REQUIREMENTS >odium Hydroxide (NaOH)-A'ot less than Q5per cent. Sodium Carbonate (hrasCOa)-h-ot more than 2.5 per cent. Ciilortde (Clj-Not more than 0.010 per cent. Sulfate iSOli--Not more than 0.003 per cent. Pliosphate (POd-ATot more than 0 005 per cent.
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 a n d 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 a d d 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 a d d 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 a n y 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 a n d saturate with hydrogen sulfide. T h e 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. T h e 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 a d d 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 a n y 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 a n d 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
I T H I S J O U R N A L13. , 736 (1921). Page 756, this issue.
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ROSIN G . C. SPENCER E D W A R D WICHERS JOSEPH
