TRANSMITTANCE OF NEAR-INRARED ENERGY BY BINARY GLASSES*

A study has been made of the transmittance of near-infrared energy by a number of binary glasses. Of the systems studied, the lithia-silica and lead oxide-silica glasses were found to have the highest transmittance of energy in the range of wave lengths from 3.0 to 5.0 microns. The transmittance of lithia-silica glass is compared with that of the other alkali-silica glasses. Values of transmittance are given for lead silicate glasses of higher lead content than previously reported in the literature.     

Components of “soybean lecithin”

Summary The acetone-insoluble material from soybean “lecithin” has been fractionated by submitting alcohol-soluble and alcohol-insoluble portions to countercurrent distribution between hexane and methanol. The alcohol-soluble portion was found to contain lecithin, cephalin, and sugars or glycosides; the alcohol-insoluble portion was separated into two major inositol-containing phosphatides and sugars or glycosides. While the commonly accepted value of 30–35% for lecithin in the phosphatides was confirmed, it appears that the accepted value of 65% of cephalin needs revision. The approximate composition for one sample of soybean phosphatides is estimated to be 29% lecithin, 31% cephalin, and 40% inositol-phosphatides. Presented at the 39th Annual Meeting of the American Oil Chemists' Society, May 4–6, 1948, in New Orleans, Louisiana. This paper reports results obtained from a research project financed by the Research Marketing Act of 1946. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Some applications of ultraviolet spectrophotometry in drying oil research

Conclusions An alkaline-solution technique has been developed permitting the study of the drying and aging process of an oil film using the ultraviolet spectrophotometer. This technique has been found to be a valuable tool for investigating some of the chemical changes which occur as a vegetable oil film dries and ages. The drying or autoxidation of an oil film has been shown to proceed along the general lines of a three-stage reaction with the short initial stage being characterized by an accumulation of conjugated diene and triene structures which reaches a maximum at the time the film has set up or becomes continuous. The second or curing stage was characterized by a slow decrease in the measurable conjugated diene and triene structures. The third or deterioration stage was not investigated; however, this method should be readily adaptable to studies involving film breakdown as represented by phenomena such as after-yellowing since the development of absorption peaks characteristic of linolenic ketones, for example, would permit an early prediction of yellowing long before the concentration of the chromophore groups became great enough for visual observation. During the initial stage of drying there was also evidence for an increase in the alpha-keto structures capable of enolizing in alkali to give absorption maxima characteristic of triene and tetraene conjugated systems. These enolizable structures also decreased in amount during the film curing period and are not characterizable on the basis of observed absorption maxima and published information. The method of obtaining a spectral solution of a dry, infusible oil film through the medium of alcoholic KOH was applied to investigations on the relationship existing between the light absorption of the film solution and the durability or weather resistance of the straight oil film. The results obtained verified the principle previously reported that the quantity of light absorbed by an oil film in the region of 320–400 mμ was indicative of the durability of the film upon exposure to accelerated weathering conditions.     

Application of the line-width method to the spectrochemical analysis of oils,fats, and related substances

Summary The application of the line-width method to the spectrochemical analysis of oils and fats in conjunction with the use of an improved ashing technique has been shown to permit the quantitative determination of copper, iron, manganese, nickel, and tin in quantities as low as 1 part in 10 million. The procedure has been critically examined by precision tests on commercial and experimental samples, by accuracy tests on synthetic samples, and by recovery tests. Results of actual analysis of 30 vegetable oils and fats indicate the use of the procedure as a research tool. The procedure may be used for the trace element analysis of organic material low in ash content. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.