Previous reports from this laboratory (1, 2) have presented the solubilities of the normal saturated fatty acids from caprylic to stearic, inclusive, in benzene, cyclohlexane, tetrachloromethane, trichloromethane, ethyl acetate, butyl acetate, glacial acetic acid, acetone, 2-butanone, methanol, 95% ethanol, isopropanol, nbutanol, nitroethane, acetonitrile, and water. In view of the usefulness of such data, the scope of this investigation has been expanded to include a number of the more common aromatic solvents, as well as several simple, substituted hydrocarbons. This paper reports the solubilities of caprylic, capric, lauric, myristic, palmitic, and stearic acids in toluene, o-xylene, chlorobenzene, nitrobenzene, 1,4-dioxane, furfural, 1 ,2-dichloroethane, and nitromethane.
EXPERIMENTALThe lauric and myristic acids used in this investigation were those employed in tho previous studies (2). The caprylic and capric acids were obtained by vacuum fractionation of Armour Neo-Fat 7 and Neo-Fat 15, respectively, in a Stedman packed column. The stearic acid was prepared by repeated recrystallization of Armour Neo-Fat 1-65 from acetonitrile. The freezing points of these highly purified fatty acids are listed in Table I. These values are in good agreement with, and in most cases exceed, the best freezing points reported for these compounds.The solvents which were used were twice distilled from the best grade of commercial producl,s, those with higher boiling points being distilled under reduced pressure. The boiling points and refractive indices of these solvents were in good agreement with the data in the International Critical Tables.The solubilities of the fatty acids were determined by the methods described previously (3-5).
RESULTS AND DISCUSSIONThe solubilities of the fatty acids in the benzene derivatives, toluene, o-xylene, chlorobenzene, and nitrobenzene, are listed in Table 11-V, respectively, and the solubilities in toluene and in nitrobenzene are shown graphically in Figs. 1 and 2, respectively. The solubilities in toluene, o-xylene, and chlorobenzene are remarkably similar in spite of the fact that the first two solvents possess only a very slight polarity while the third is a moderately polar solvent. Upon an equimolar basis these solubilities are practically identical, indicating that moderate differences between the respective polarities of the solvent and solute exert much less influence upon the solubilities of the fatty acids than do other factors, such as the relative internal pressures of the molecules, intermolecular attractive forces, etc. The relatively high polarity of nitrobenzene, on the other hand, results in somewhat lower solubilities of the fatty acids. The high polarity of the solvent, however, is accompanied by other changes in its physical properties, such as in-
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