Commercial cashew nut shell liquid is a dark colored indefinite mixture containing three alkenyl phenolic components and certain decomposition and polymerization products. The phenolic components are a monophenol (cardanol),3 a salicylic acid derivative (anacardic acid), and a resorcinol derivative (cardol)(2).The monophenol, which is the major component of the commercial shell liquid is formed by decarboxylation of the anacardic acid component during the extraction of the shells at high temperature. The shell liquid when obtained by a low-temperature solvent-extraction process, contains only anacardic acid and cardol. The anacardic acid is the major component.Although the carbon skeletons of these alkenyl phenols have been definitely established (3), the exact nature of the unsaturation of their fifteen carbon side chain has not yet been determined. Since the industrial uses (4) and the physiological functions (5, 6) of these types of phenolic compounds are intimately associated with their unsaturated character, the problem of clarifying their olefinic structure is one of considerable interest.The phenolic components of the shell liquid show an unsaturation equivalent to about two olefinic bonds when freshly prepared, and previous investigators have assumed the phenols to be homogeneous diolefins. However, Sletzinger and Dawson (7), working with the monophenolic component of the commercial shell liquid, found that it was not a homogeneous diolefin, but a mixture of mono-, di-, and possibly trior higher olefins, having the fortuitous average unsaturation of two olefinic bonds. Qualitatively, the same results were obtained when a sample of the monophenol, resulting from the decarboxylation of a solventextracted anacardic acid, was investigated. However, in both cases investigated by Sletzinger and Dawson, the monophenol was subjected to temperatures of