ANALYTICAL EDITION
October 15, 1942
Summary A photometric procedure has been described for the determination of acetone-insoluble material and break in solventextracted soybean oil. The photometric method is rapid, possesses an average precision of approximately 0.005 break per cent, and is relatively free of errors introduced by differences in technique. A direct empirical relation has been
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found between acetone-insoluble material and break in solyent-eutracted soybean oils. LiLerature Cited (1) - h i . Oil Chemists’ SOC., Official and Tentative Methods, p. 16e. ( 2 ) A ~ ~ O COfficial . ~ ~Chem., r . Official and Tentative Methods of Analysis, 5th ed., p. 114 (1940).
Determination of Oxide Copper R. S. YOUNG AND D. G. 31. GRAHARI Nchanga Consolidated Copper Mines, Ltd., Chingola, Northern Rhodesia
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N RECENT editions of widely used reference books on the chemical analysis of metallurgical products (1, 2 ) , i t is stated that cuprite, tenorite, malachite, chrysocolla, and other oxidized forms of copper can be determined by leaching with 3 per cent sulfur dioxide. This method depends on the fact that oxidized copper is soluble in dilute sulfurous acid, whereas copper sulfides are unattacked under these conditions. It is recommended that 1 to 2 grams of 100- to 150-mesh ore be agitated with approximately 100 ml. of 3 per cent sulfur dioxide for 0.5 to 2 hours, filtered, and washed, and copper determined on the filtrate or oxide portion. I n many parts of the world oxide copper is determined by leaching with 5 per cent sulfuric acid saturated with sulfur dioxide, instead of the 3 per cent sulfur dioxide recommended in the literature. During a study of local oxidized copper ores a large number of comparative tests were carried out on mine and concentrator products, using these two solutions. Slightly higher and more consistent results were secured when using 5 per cent sulfuric acid saturated with sulfur dioxide, but in these complex products it is difficult to obtain an absolute or calculated value for the oxide copper present. The authors then turned to pure copper minerals, whose composition they could determine by careful chemical and mineralogical analysis, in their study of the determination of oxide copper. The material was ground to
