The n-fatty acids

The normal fatty acids may unquestionably be regarded as one of the most interesting and important groups of chemical compounds. Many of them occur commonly in nature, and form the basis of valuable industrial products. The part which they and their derivatives play in life processes gives them a particular interest to the biologist. As compounds, which appear to be readily obtainable pure, and which form regular series including a comparatively large number of individuals, they furnish the chemist and physicist with material peculiarly adapted for the study of the relationship between constitution and properties. For these reasons they have been the subject of an almost endless number of investigations, in which the preparation and properties both of individual members or groups of individuals have been studied. At this stage, it might well have been assumed that every member of the series had long since been obtained pure, and its properties determined with so high a degree of accuracy, that only the exacting requirements of some new investigation would have demanded further study of the subject. Reference to the literature of the subject, however, showed that the real position was by no means satisfactory. While, on the one hand, the results of the determination of such a property as the melting point of certain members of the series, for instance, arachidic acid, obtained from various natural sources by chemists of established reputation, gave a constant value, and while the criteria of purity of the various samples were quite satisfactory, the material was certainly not identical with samples of the corresponding acid prepared synthetically. The difference was in some cases such as to justify the assumption that the natural and synthetic acids were differently constituted, but no theory could be found to account for the observed differences.