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T HE CI-IARACTERIZXTION of the naturally occurring C6-C~s saturated fat acid esters through various physical constants has been the subject of immediate concern in this laboratory for a number of years. This paper presents data for the physical characterization of (1) the ethyl esters of the aforementioned acids and (2) the ethanoate esters of the saturated monohydric alcohols obtained through the reduction of the respective acids. Preparation and Purificatio~Ethyl Esters. The ethyl esters of caproic, eapric, lauric, myristic, and pahnitic acids (of varying degrees of purity) were furnished by the Kessler Chemical Company. These compounds were purified by repeated fractional distillations, using either a column packed with glass curls or a column packed with single-turn glass helices.Ethyl caprylate and ethyl stearate were prepared by refluxing Armour's Neo-Fat 7 and 1-65, respectively, with an excess of ethyl alcohol in the presence of concentrated sulfuric acid (5% by weight). The esters were purified by repeated fractional distillations.Ethanoate Esters. Methyl esters of the naturally occurring saturated fat acids from caprylie to stearic were prepared by reacting the crude acids with an excess of methyl alcohol in the presence of eOllcentrated sulfuric acid (5% by weight). The esters were purified by repeated fractional distillation. The esters from laurate to stearate were also hydrogeimted as a part of the purification procedure. The refractive indices of the purified methyl esters corresponded to those reported by Althouse, Hunter, and Triebold (1).The saturated alcohols having the same carbon content as the above-mentioned acids were prepared by the reduction of the methyl esters with lithium aluminum hydride (LiA1H4). The detailed procedure for this reduction is given by Bonhorst (3).The crude preparations of octanol, decanol, and dodecanol were purified by fractional distillation. Benzene solutions of each of the alcohols were treated with ethanoic anhydride. The ethanoate esters were purified by fractional distillation.Benzene solutions of the crude preparations of tetradecanol, hexadecanol, and octadecanol were treated with ethanoic anhydride, The ethanoate esters were purified by fractional distillation.Hexyl ethanoate was prepared by treating practical n-hexanol (Eastnmn) with ethanoic anhydride. The ester was purified by fractional distillation. Based in part on dissertations presented by g. W. Shigley, C. W. Bonhorst, and C. C. Liang to the faculty of the Graduate School of Pennsylvania State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

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Summary Methyl esters of saturated naturally occurring fat acids from C6 through C18 were prepared and purified by fractional distillation. Refractive indices were used as a measure of their purity. A micro surface tension apparatus was constructed to comply with a modified capillary rise method devised by Ferguson. The surface tensions of water and of benzene were determined at several temperatures. The results obtained compared quite favorably with the values listed in the International Critical Tables. The surface tensions of the methyl esters were determined at 40°C., 60°C., and 80°C. with an accuracy of ±0.15 dynes/cm. Similar to other homologous series the surface tensions of the fat acid methyl esters decrease with increasing temperature, apparently in a linear manner. As the molecular weight of the methyl ester series increases, the surface tension also increases. Close correlation is shown for the methyl esters between the calculated parachors based upon Gibling's system of values and the experimental parachors.

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