108
JOURNAL OF CHEMICAL EDUCATION
JANUARY, 1930
of undeviated rays is greater, and the blinding effect produced by direct reflection of light from the white cloud is completely lost in the black. Screening smokes are more effective in atmospheres of high humidity, probably because such substances are usually deliquescent or hygroscopic, and therefore absorb moisture. This causes the particles to grow to a size which will effectively reflect light rays and hence increase the screening power. In the case of phosphorus the humidity is of primary importance since i t depends for its maximum effect upon the hydrolysis produced by water vapor in the air. The screening power of a smoke is usually measured in terms of the weight necessary to obscure when distributed over an area 100 feet long by 10 feet high, the depth being immaterial (within limits). This value for white phosphorus is 0.4 oz. Naturally, the most efficient smoke material is that which takes much from the air for its formation (from the standpoint of the quantities required). Phosphorus is ideal in this respect since it first takes oxygen from the air to form particles of P20s and these particles then grow by absorption of water vapor from the air, forming droplets of H8POn. One pound of phosphorus takes up 1.29 pounds of oxygen and 0.87 pound of water to form 3.16 pounds of smoke. The resultant smoke is harmless to man and equipment, although i t sometimes causes coughing. References Chemical Warfare Magmine, Vol. 1-15 inclusive. Chemical Warfare School Texts, Books I-X inclusive. Fries and West, "Chemical Warfare," MoEraw-Hill Book Co., New York City, 1921. Edward P. Vedder, "Medical Aspects of Chemical Warfare," Williams & Wilkins Co., Baltimore, 1925. Production of Nitric Acid in Japan. Japan is able t o produce sufficient nitric acid to meet all her needs, and has a surplus for export. The ammonia oxidation process is the only method used, and the bulk of the present production is from two companies. The production during recent years was as follows: 1925, 15,929,936 pounds; 1926, 17,226,370 pounds; 1927, 14,226,606 pounds; 1928, 15,M)0,000 pounds. Manufacturers are not producing t o their full capacity and many o t h r factories besides the two at present mncwltmtin,: on this product could manufacturr if necLssary. Estimates of putcntid produrtioo 3re not obtainable. Exports of nitric acid by Japan fur the pa5t three yea& were as follows: 1926, 3,413,500 kin; 1927, 4,310,400 kin; 1928, 4,351.500 kin (1 kin = 1.32 pounds).-Chem. Age Competition for Detection of Mustard Gas. The committee of award for the competition for the production of a reagent for the detection of dichloroethyl sulfide (mustard gas) consists of the following: Professors F. Haber, Berlin; Sir William Pope, Cambridge; F. Swarts, Ghent; and G. Urbain, Paris. The secretary of the committee is the technical adviser to the International Committee of the Red Cross. Professor L. Demolis, Geneva. The committee of award will meet in Paris in April, 1931.-Chem. Age ~
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