ANALYTICAL EDITION
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TABLEI. DETERMINATION OF HYDROCYANIC ACID IN CARBON termined, and each flowmeter which is to be used for this DIOXIDE-AIRMIXTURES purpose should be individually calibrated. HYDROCYANIC ACID A solution of hydrocyanic acid in water, of a definite conCARBONDIOXIDE SAMPLE VOLGMEI Total Per liter centration and a t a definite temperature, has a definite hydro% Liters MO Ms. cyanic acid vapor pressure. This means that it will produce 6.73 1.52 0.0 4.43 5.90 100.0 3.93 1.50 the same volume concentration of hydrocyanic acid in any 47.0 4.29 5.46 1.27 indifferent gas which is brought into intimate contact with 27.0 4.37 5.54 1.27 the solution. Therefore, if pure carbon dioxide is slowly 5.75 1.31 12.4 4.40 4.41 5.85 7.0 1.33 bubbled through such a solution, it will acquire the same vol0.0 4.42 5.70 1.29 5.76 1.31 ume concentration of hydrocyanic acid as will a current of 7.0 4.41 12.4 4.40 5.63 1.28 air which is passed through the same solution. By the use 8.0 4.41 4.23 0.96 of this device the same concentrations of hydrocyanic acid 4.20 0.0 4.42 0.95 in air and in various carbon dioxide-air mixtures have been 8.0 4.41 3.64 0.83 produced, and the method of analysis has been checked by 3.63 0.82 0.0 4.42 analyzing the mixtures. Results obtained in this manner are 2.92 0.66 0.0 4.42 given in Table I, grouped in such manner that the results in 8.0 4.41 2.92 0.66 column 4 would be identical within each group if there were no errors of any kind during the experiments. Considering It appeared that under these circumstances hydrocyanic the fact that there are probably other inaccuracies in addition acid might be determined satisfactorily by absorption in 2 to those of analysis, the results indicate that this method is per cent sodium carbonate solution, with subsequent titra- suitable for the determination of hydrocyanic acid in carbon tion with standard iodine. This plan contemplated that the dioxide-air mixtures, volume of gas mixture would be determined by measuring LITERATURE CITED its rate of flow through a flowmeter which had been calibrated previously for carbon dioxide-air mixtures. The calibration (1) Griffin and Skinner, IND.ENG.CHIM.,24,862 (1932). curve for this purpose is shown in Figure 4. This curve is (2) Pratt, Swain, and Eldred, J.Econ. Entorno!., 24,1041 (1931). strictly applicable only to the flowmeter for which it was de- RECEIVEDJuly 28, 1932.
Determination of Small Quantities of Antimony in Solder in Presence of Iron C. W.
ANDERSON,
Continental Can Company, Inc., 4633 West Grand Ave., Chicago, Ill.
T
HIS laboratory is called upon to analyze numerous
samples of scrap solder which consist chiefly of tin and lead, but which are contaminated with as much as 5 per cent of iron. The presence of iron interferes with the titration of antimony by the usual bromate method, particularly if the amount of iron in the sample is more than 0.1 per cent. A method has therefore been worked out which eliminates this difficulty. I n reviewing the literature it was found that very little information had been recorded on the titration of antimony in the presence of iron. However, Rowell (1) in his method of direct estimation of antimony by the bromate method notes that the presence of 1 per cent iron increases the results by about 0.02 per cent. He gives no definite figures with larger quantities of iron. The following procedure has given satisfactory results when as much as 15 per cent of iron is present in the sample: Dissolve a 3-gram sample in 15 to 20 cc. of hot concentrated sulfuric acid in a 250-cc. Erlenmeyer Aask. Cool the solution and add carefully 50 cc. of concentrated hydrochloric acid. Add about 0.5 gram of potassium chlorate to oxidize the iron and expel the chlorine by boiling. Cool the solution and add 20 to 25 cc. of phosphoric acid, sp. gr. 1.37, and then 3 to 4 grams of sodium sulfite. Allow the solution to stand at a temperature of about 60" C. for 15 minutes and expel the excess sulfur dioxide by boiling in a current of carbon dioxide or air for 5 t o 10 minutes. Add about 50 cc. of water, and titrate at about 60' C. with 0.033 N potassium bromate solution which has been standardized against metallic antimony using methyl orange as indicator. About the same quantity of iron should be present in the antimony solution used for standardizing the bromate as is
present in the sample for analysis. The iron may be added as ferrous or ferric sulfate and the process of solution, reduction, and titration conducted in the same manner as in a regular determination. The methyl orange indicator should be added toward the end of the titration, having ascertained the approximate amount of bromate required by a preliminary test. The color change a t the end point is readily detected, since a dilute phosphoric acid solution is only faintly colored by the usual quantities of iron occurring in scrap solder. The amount of bromate required to destroy the methyl orange color is very slight, the correction usually being approximately 0.1 cc. which is deducted from the number of cubic centimeters used in titrating. ANALYSES TABLEI. RESULTSOF EXPERIMENTAL IRON TAXEN SOLDER TAKEN AS FeSOa.7HzO
a b
ANTIMONY TAKEN
Cram Grams Gram 3.0" 0.0300 0.1 0.0198 3.0a 0.16 0.0498 3.05 0.20 0.0104 3.0a 0.30 0,0400 3.0" 0.14 0.0250 0.10 3.0" 0.0050 2.26 0.16 0.0251 3.OC 0.4 0.0321 3.0C 0.6 0.0141 3.0d 0.4 0.0300 3.0d 0.5 Antimony content 0.03%. Antimony content 0.015%.
TOTAL ANTIANTIMONY PREEENT FOUND Cram Uram 0,0309 0.0310 0.0206 0.0207 0.0507 0.0600 0.0113 0.0106 0.0405 0.0394 0.0269 0.0254 0.0053 0.0058 0.0269 0.0268 0.0339 0.0344 0.0153 0.0148 0.0312 0.0302 0 Antimony content 0.06 d Antimony content 0.04g: MONY
LITERATURE CITED (1) Rowell, H. W., J. SOC.Chem. Ind., 25, 1181 (1906). RBIOEIVED Sugust 25, 1932.
