January 15, 1933
INDUSTRIAL AND ENGINEERING
method, it has to be attacked only by concentrated hydrochloric acid plus water a t boiling temperature, using sodium chlorate to dissolve the antimony. For the determination of lead, copper, and antimony, any suitable acid may be used. If the slag does not dissolve, i t has to be fused with sodium peroxide and treated according to the following procedure: TIN. One-half gram is weighed into a nickel crucible, fused with sodium peroxide, and the fusion decomposed with water in a 400-cc, beaker. To this fusion 12.5 cc., equal to 0.5 gram, are tapped from the 500-cc. flask. If a preliminary test shows the absence of copper in great quantities, the solution is neutralized with hydrochloric acid, and an excess of 80 cc. is added. This solution, which should be about 200 cc., is boiled for a few minutes to expel all chlorine, and is then ready to be reduced and titrated according to standard methods. If the preliminary test shows high copper, the procedure is somewhat different. To the clear solution of hydrochloric acid are added 10 to 15 cc. of ferric chloride solutions (500 grams of ferric chloride to 5000 cc. of water), then ammonium hydroxide in excess, and 3 to 5 grams of ammonium carbonate. This is boiled for a short time and filtered. After the copper is washed out, a hole is punched in the filter paper through which the precipitate is washed into a 500cc. Erlenmeyer flask. The adhering precipitate is cleaned from the filter paper by washing out with hydrochloric acid (1 to 1). (It is not necessary to wash out the copper quantitatively from the precipitate of the hydroxides, as copper in small quantities does not influence the titration of the tin.) Enough hydrochloric acid is then added to the solution to bring the total free acid up to 80 cc. It is then ready t o be run for tin according to standard methods. LEADAND COPPER. If the slag does not dissolve in acid, one gram of it is fused in an iron crucible with sodium peroxide. The fusion is decomposed with water in a 600-cc. beaker, 25 cc. (equal to one gram) are tapped from the solution of the metallic part, and 60 to 70 cc. of yellow sodium sulfide (2500 grams of sulfide crystals dissolved in 12 liters of water with enough sulfur added to make the solution deep yellow) added to separate the lead and copper from the tin and antimony. The solution is boiled moderately, filtered, and waEhed twice with sodium sulfide containing hot water. Then the filter paper plus the precipitate is brought back to the beaker, 25 cc. of concentrated sulfuric acid added, and the paper destroyed by addition of nitric acid. After strong fuming, water is added and the solution boiled until the ferric salts dissolve. The lead sulfate is separated from the solution by filtration, and the lead determined as chromate according to standard methods. I n the filtrate the copper is determined according to the potassium sulfocyanate method with subsequent electrolysis. ANTIMONY.Two grams of the slag are fused in an iron crucible. The fusion is decomposed with water, 50 cc. (equal to 2 grams) of the solution of the metallic part are added, and the alkaline solution saturated with 70 to 80 cc. of yellow sodium sulfide. This solution is transferred to a 500-cc. flask and, after cooling, 250 cc. (equal to one gram) are filtered through dry filter paper. These 250 cc. are acidified with 100 cc. of concentrated hydrochloric acid, the solution boiled down to 150 to 175 cc., then 30 cc. of concentrated hydrochloric acid added and the solution gassed for 20 to 30 minutes with hydrogen sulfide to remove the arsenic as arsenous sulfide. The subsequent filtration is best done through a filter paper which has previously been moistened with hydrochloric acid (1 to 1). After two washings with this hydrochloric acid, the filter is finally washed with hot water. To this filtrate 3 to 5 grams of sodium
CHEMISTRY
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chlorate are added and the solution boiled down t o crystals. After cooling, 100 cc. of water are added and the solution shaken until it is clear. Then a few crystals of potassium iodide are added and the liberated iodine titrated with sodium thiosulfate. NOTES.If the lead content of the white metal products becomes very high, the solution has t o be made in a 1000-cc. flask in order t o keep the lead chloride from precipitating in the hydrochloric acid solution. In adding the oxidizing reagent, an excess of nitric acid must be avoided. If too much acid has been added and the lead chloride crystals begin to precipitate after cooling, the whole solution plus the precipitated lead chloride must be transferred to a bigger flask so that the greater quantity of hydrochloric acid can keep the lead chloride in solution. RECEIVED July 18, 1932.
Modified Combustion Apparatus R. N. EVANS Research Bureau, Brooklyn Edison Co., Inc., Brooklyn, N. Y.
S
EVERAL improvements in analytical combustion a p paratus have been recently published (1, S), one of which is the use of interchangeable ground-glass joints ( 2 ) . The chief difficulties in the latter design are the faulty alignment of the individual units which go to make up the train, the liquefaction of the grease on the ground joints of the combustion tube, and the delay and awkwardness in the process of inserting the boat containing the sample to be analyzed. The photograph illustrates the manner in which these difficulties were overcome in this laboratory. A circular flexible piece of glass tubing in the train allowed for expansion on heating and also compensated for lack of alignment. The side arm of the combustion tube made it possible to insert the sample without interrupting the flow of gas or without dis-
connecting the sections of the train. Finally, copper radiating vanes were fitted to the quartz tube by first winding the tube with fine copper wire and then soldering the copper collar, with the attached radiating fins, to the layer of copper wire. Ordinary stopcock grease was used with no difficulty when the joints were protected from the thermal flow in this manner. LITERATURE CITED (1) Avery and Hayman, IND.ENG.CHEM.,Anal. Ed., 2, 336 (1930). (2) Brunn, J., Bur. Standards J. Research, 2,487 (1929). (3) Stanffeld and Sutherland, Can. J . Research, 3, 318-21 (1930). RECEIVEDSeptemher 20, 1932
