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below are recommended. These brands may contain a conMODIFICATION I V (For copper high in arsenic only)-The siderable amount of arsenic and some antimony, tellurium, committee gives preference to “ B . ” bismuth and nickel. ,411 assays are made in duplicate and must A-Dissolve the sample in 42 cc. of the “Assay Solution” check within a n outside limit of 0.015 per cent. in the regular way and add j grams of ammonium nitrate. ElecIt has been recommended1 to use with solutions of these cop- trolyze as usual. pers about 2 cc. of an addition agent prepared by boiling “hard B-Dissolve the sample in 60 cc. of the “Assay Solution” oil” with strong .nitric acid, cooling and removing the grease. instead of 42 cc. Electrolyze as usual. This, it is said, will permit the use of high current densities and SCOVILLMASCFACTURI~YG Co., WATERBURY,CONN. yet allow the copper t o be deposited pure and bright. Moreover, it is said that arsenic and antimony, when present, do not ANALYSIS OF SPELTER2 contaminate the copper. It seems probable, however, t h a t Report f r o m a Subcommittee on M e t h o d s of Analysis of Non-ferrous copper deposited from such solutions is not quite pure and that Alloys of t h e Division of Industrial Chemists a n d Chemical Engineers: it is more accurate to purify the cathode deposit (Modification W u . B. PRICE,C h a i r m a n , ALDEN MERRILL, GEo. I,. HEATH, I below) or t o give a preliminary treatment t o the solution GILBERT RICG, BRLTO WOICIECHOWSKI (Modification 11). Received April 30, 1915 The committee gives preference to Modification 11, and ModiSpelter ordinarily used for brass and similar alloys is usually fication I should be used only in the presence of small amounts considered in three grades: A, “High Grade;” B, “Intermeof impurities. diate;” and C, “Brass Special;” according to the amounts of MODIFICATION I-Carry out the assay exactly as given for ,lead and other impurities present. 4 fourth grade, D, “Prime Electrolytic and Low-Resistance Lake Copper. Place the Western,” principally used for galvanizing, contains more imcathode in a clean beaker, cover with a watch glass perforated purities than the three grades preceding. These grades are with a small hole just large enough t o accommodate the stem covered by the specifications of the .4merican Society for Testof the electrode, add 42 cc. of stock “Assay Solution” and water ing Materials in its Year Book for 1913, pages 248-251. enough to cover the sheet. Let it stand upon the steam bath The methods of sampling and analysis described below are until the coating is dissolved. Re-electrolyze in the regular those generally accepted in the United States for standard manner. analysis in all the larger laboratories of both producers and conMODIFICATION 113-Dissolve a 5-gram sample in 42 cc. of the sumers of zinc and zinc products. The methods of analysis “Assay Solution” and evaporate until all the nitric acid is ex- are those originally proposed by Elliott and Storer3 and Price,‘ pelled. Redissolve in 7 0 cc. water and add 3 cc. ferric nitrate whose work has been checked and elaborated by the members solution ( I cc. = 0 . 0 1 g. iron). Transfer the solution to a lipped of the committee beaker and place the original beaker under a funnel fitted with SAMPLING SLABS a small filter paper. Precipitate the iron from the hot liquid Select ten slabs a t random from a carload and saw each by ammonia, filter and wash out salts. Place the solution on a slab completely across from the middle of one long side to the hot plate to concentrate, reprecipitate the hydroxide from middle of the other and use the sawdust as the sample; or, drill dilute sulfuric acid in a very small volume of solution and add three 9 mm. holes along one diagonal of each slab, boring comthe filtrate to the main solution. Reprecipitate the hydroxide pletely through and taking care to make fine drillings; the holes once more from dilute sulfuric acid, filter, wash thoroughly should be drilled as nearly as possible a t the middle and one-half and add the filtrate to the main solution. Make acid with dilute way between either end and the middle of such diagonals. Go sulfuric acid and add z cc. of nitric acid (I .42 sp. gr.). Deposit over the drillings or sawings with a powerful magnet t o take out the copper as in the method for Electrolytic and Low-Resistance any iron which may have come from the drill or saw, and mix Lake Copper. the sample thoroughly. The drill or saw must be thoroughly MODIFICATION 1114 (For copper containing only traces of cleaned before use, and no lubricant shall be used in either drillantimony or bismuth but sufficient selenium or tellurium t o ing or sawing. interfere)-Dissolve the 5 gram sample in 42 cc. of “Assay METHODS O F AN.4LYSIS Solution” and evaporate until fumes appear, or un$il the residue LEAD-The committee cqnsiders the Electrolytic and “Lead is white. Redissolve in 60 cc. of water and saturate the boiling Acid” methods described below to be of equal merit, so far as hot solution for I O minutes with sulfur dioxide gas, removing the solution from the lamp when the gas is started. The gas accuracy is concerned, but where laboratories are equipped may be generated by dropping cold saturated sodium sulfite for electrolysis the electrolytic method is preferred as a time solution into strong sulfuric acid. It is also conveniently ob- saver. LEAD BY ELECTROLYTIC METHOD-Place 8.643 grams Of the tainable in cylinders which are fitted with a valve. Let the precipitate settle for a few hours, filter and wash with a little sample6 in a 400-cc. beaker and add sufficient water to cover the hot water. Boil the filtrate gently t o remove most of the sul- sample. Then add gradually and cautiously 30 cc. of concentrated nitric acid (sp. gr. I . 4 2 ) ; when the action is complete fur dioxide gas. Ignite the filter in a porcelain crucible to volaboil the solution for a few minutes to expel nitrous fumes. n’ash tilize the selenium5 and tellurium, redissolve the oxidized residue in 1.5-2 cc. of nitric acid and add t o the main solution. Deposit the watch glass and sides of the beaker and transfer the solution to a 200-cc. electrolytic beaker. Dilute to 125 cc. and electhe copper as in the method for Electrolytic and Low-Resistance trolyze with a current of five (j) amperes. The time required Lake Copper. for the electrolysis is from l / , to 3 / 4 of an hour, depending upon . Guess, Tuans. Am. Inst. J l i n Eng., 36 (1905), 605. the amount of lead present in the sample. Test the solutions 2 Keller Ibid., p . 2099 (1913). Bull. 8 0 ; H e a t h , THIS JOURNAL, S (191 1 ) . 7 5 . 3 H e a t h (Senter modified), J . .Am. Chem. S O L , 26 (1904), 1123 4 H e a t h . I b i d . , 26 (1914). 1123; Keller, Tuans. Am. I n s f . M i n . Eng., p . 2098 (1913), Bull. 80. j T h e selenium is said t o be carried down b y sulfur dioxide a s a seienide o f silver, b u t t h e roasting sufficiently removes t h e elements selenium a n d tellurium. W h e n silver is t o be removed, theseienium, e t c . , are thrown down w i t h t h e silver b y t h e sulfur dioxide gas a n d t h e p’recipitation of silver is t h e n completed b y t h e addition of chlorides or hydrochloric
acid.
1 (A) H e a t h , J . A m . Chem. Sac., 26. (1904). 1124; (B) H e a t h , THIS JOURNAL, 3 (19111, 7 5 . 3 Approved b y t h e Supervisory Committee on S t a n d a r d N e t h o d s of Analvsis. American Chemical Societv. M e m . A m . Acad. Arts and Sciences. 8 , P a r t I . M a y 20 (1860) 4 The Chemical Engineer, 9 !1909), 4. a T h e empirical f a c t o r weight (8.643:) i. used in>tead of ~ h theoretical r one i8.66),a5 t h e dried dioxide is liable to contain some adherent and included water, expelled with difficulty E F Smith’s “Electro-analysis, 4 t h edition, p. 102.
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for complete precipitation of lead by washing the watch glasses and sides of the beaker, so t h a t the depth of the solution is increased about I Z mm. Then continue the current for fifteen minutes and if the newly exposed surface is still bright, the lead is completely deposited. Wash the anode three or four times with distilled water, once with alcohol and then dry in an oven, or on a hot plate, a t 2 1 0 ’ C. for I,/* hour and weigh. The weight of the PbOn in milligrams, divided by 100, will give the percentage of lead. The PbOt deposit can be readily removed by covering the anode with dilute nitric acid and inserting a rod of copper. The electrodes are cylinders of platinum gauze with 400 meshes per sq. cm. The anodes are 30 mm. in diameter, by 30 mm. high, with a stem 105 mm. long of No. 16 Brown & Sharpe gauge wire ( I ,z 9 mm.), making the total height 137 mm. The cathodes are I Z mm. in diameter by 30 mm. high, with a stem 105 mm. long of No. 16 Brown & Sharpe gauge wire, making the total height 137 mm. LEAD BY “LEAD A C I D ” METHOD’-PlaCe in a 350-cc. beaker z j , r j , I O or 5 grams of the drillings or sawings, according t o whether the spelter is of Grade A, B, C or D, respectively, and add, according to the size of the sample taken, 300, 180, I Z O or 60 cc. of “lead acid” (prepared as indicated in footnote below). After all but about one gram of the zinc is dissolved, filter on a close filter and wash out the beaker a couple of times with “lead acid” from a wash bottle. Wash the undissolved matter from the filter into the original beaker with water and dissolve with a small amount of hot I : I nitric acid. Add 40 cc. of “lead acid,” and evaporate until strong fumes of sulfuric acid escape. When cool, add 35 cc. of water (which is the quantity of water evaporated from the “lead acid”), and heat t o boiling. Add the first filtrate (containing the greater part of the zinc, and possibly a small amount of lead sulfate), stir well, and allow t o stand for a t least five hours, preferably over night. Filter on a Gooch crucible, wash with “lead acid,” then with a mixture of equal parts of alcohol and water, and finally with alcohol alone. Set the Gooch crucible inside a porcelain crucible in order t o avoid reduction of lead by flame gases and mechanical disintegration of the asbestos mat. Ignite for five minutes a t the full heat of a Tirrell burner. Cool and weigh as PbS04. moix-Place 25 grams of zinc in a tall 700-cc. beaker and dissolve cautiously in 125-cc. of nitric acid (sp. gr. I . 4 2 ) . Boil, dilute to about 300 cc., add I O grams of ammonium chloride, and then ammonia until the precipitated zinc hydroxide has redissolved. Boil, let settle and filter on a n I I-cm. s. & s. “Black Ribbon” or similar filter paper. Wash with dilute ammonia and with hot water. Dissolve the precipitated ferric hydroxide with hot I : 4 sulfuric acid, add 40 cc. of I : I sulfuric acid, pass through a Jones reductor,* wash first with I j o cc. of dilute sulfuric acid and then with IOO cc. of water and titrate with potassium permanganate. The potassium permanganate solution contains approximately 0 , z gram of the crystals per liter. One cc. of permanganate solution will equal about 0.000334 gram of iron. Run a blank with the same amounts of acid and water and correct accordingly. 1 “Lead Acid” is a solution of one volume of sulfuric acid in seven volumes of water, s a t u r a t e d with lead sulfate. It is prepared a s follows: 300 cc. of sulfuric acid (sp. gr. 1,841 are poured into 1800 cc. of water: one gram of lead acetate is dissolved in 300 cc. of water a n d is added t o the h o t solution with stirring. T h e solution is allowed t o settle for several d a y s a n d is siphoned off through a thick asbestos filter for use. When “lead acid” is used i t is unnecessary t o consider t h e solubility of t h e lead sulfate, since t h e solution is always brought back t o t h e same volume as t h e volume of “lead acid” originally a d d e d ; consequently, when t h e lead sulfate is filtered no more lead remains in t h e filtrate t h a n was originally added in t h e “lead acid.” I f , before passing t h e solution through the ‘reductor a large a m o u n t of lead sulfate is present, it is well t o filter i t off so as t o prevent i t from clogging t h e reductor.
Val. 7 , NO. 6
Standardize the potassium permanganate against sodium oxalate. Weigh duplicate samples of sodium oxalate, o,ozoo gram each, an amount which may require between 49 and 50 cc. of the permanganate solution. T o convert sodium oxalate to iron, use the factor 0,833. cADrmuhl-Place z j grams of drillings in a tall 500-cc. beaker; add 2 5 0 cc. of water and 5 5 cc. of concentrated hydrochloric acid and stir. When the action has almost ceased add more acid with stirring, using about z cc. at a time, and allowing t o stand after each addition of acid, until finally all but about two grams of the zinc have been dissolved. About 60 cc. of acid in all are usually required; it is best t o allow the first 5 5 cc. of acid t o act over night. Filter, first transferring one of the undissolved pieces of zinc to the filter, and wash a couple of times with water. Discard the filtrate. Wash the undissolved matter on the filter paper into the 500-cc. beaker, cover, and dissolve in nitric acid. Transfer to a casserole, add 20 cc. of I : I sulfuric acid and evaporate until fumes appear, take up with about 100 cc. of water, boil, cool, and let settle for several hours (best over night). Filter off the lead sulfate on paper, wash with water, retain the filtrate and discard the lead sulfate. Dilute the filtrate to 400 cc., add about I O grams of ammonium chloride, and pass hydrogen sulfide for one hour. It is occasionally necessary t o start the precipitation of the cadmium sulfide by the addition of a drop or two of ammonia to the dilute solution. Allow t o stand until the precipitate has settled, and then filter off the impure cadmium sulfide in a loose-bottomed Gooch crucible; remove the cadmium sulfide by carefully punching out the bottom into a tall zoo-cc. beaker. Wipe off any cadmium sulfide remaining on the sides of the crucible, using a little asbestos pulp, add 60 cc. of I : 5 sulfuric acid and boil for one-half hour. In case of spelters carrying large amounts of cadmium it may be necessary to add more acid. The dilute acid dissolves cadmium and zinc sulfides, but not lead sulfide. Filter and dilute t o 300 cc., add about j grams of ammonium chloride and precipitate with hydrogen sulfide again in order to get rid of traces of zinc. In case a large amount of cadmium is present, a third precipitation may be necessary. After the final precipitation, let settle, filter and transfer t o a weighed platinum dish, cover, and dissolve in I : 3 hydrochloric acid. Also dissolve the sulfide remaining on the filter paper in hot I : 3 hydrochloric acid, and add it to the solution in the platinum dish. Add a little sulfuric acid and evaporate the solution until copious fumes escape. Dilute with water, add a few cc. of concentrated nitric acid to oxidize any filter paper shreds, and again evaporate the solution until fumes of sulfuric acid come off freely. Remove the excess of sulfuric acid by heating the dish cautiously, and finally heat to between 500’ and 600’ C. or to dull redness, and weigh the cadmium as sulfate. ALTERNATE METHOD FOR CADMIUM-Proceed as above until the cadmium sulfide has been dissolved in hydrochloric acid. Oxidize with nitric acid and filter from sulfur. Transfer the solution t o a zoo-cc. electrolytic beaker, add a drop or two of phenolphthalein and then pure sodium or potassium hydroxide solution until a permanent red color is obtained. Add a strong solution of pure potassium cyanide with constant stirring until the precipitate of cadmium hydroxide is completely dissolved. Avoid using an excess of the potassium cyanide. Dilute the solution to 1 5 0 cc. and electrolyze with a current of five amperes, using gauze electrodes of the same size as in the lead determination. The time required is I to z hours. The solution should always be tested for cadmium as follows: Raise the liquid in the beaker and then note after twenty minutes the newly exposed surface of the electrode. If i t is still bright, the cadmium is completely deposited. S e x t wash the electrodes with distilled w,ater and then with alcohol. Dry a t 1 0 o O c., cool and weigh. The increase is metallic cadmium. SCOVILL h I A K U P A C T U R 1 S G
CO.. WVATERBCRY, C U N S
