Solubilities of saturated fatty acids in water reported by John and McBain (1) are one-fifth to one-tenth of those reported by Ralston and Hoerr (2). As a result of these discrepancies, it was decided to reopen the study.EXPERIMENTAL Preparation of Materials. The fatty acids used in this work were highly purified samples prepared by Mr. R. S. Sedgwick. Freezing points of the acids were as follows: octanoic, 16.63°; nonanoic, 12.52°; decanoic, 31.49°; hendecanoic, 28.59°; dodecanoic, 44.16°; tetradecanoic, 54.25°. Water with a conductivity of 1 micromho was used in making up all solutions.Procedure. Most of the determinations were made on fatty-acid solutions saturated by heating to 100°, shaking, then placing in a constant-temperature bath with a regulation range of ±0.05°. In several cases, saturation was also approached from a lower temperature, and in all such runs identical values were obtained. The minimum saturation time at the desired temperature was 16 hours. This time was checked in some cases by starting from an over-or under-saturated state, and was found to be adequate. During the saturation period, the solution was stirred by bubbling purified nitrogen through it. The nitrogen had previously been led through soda-lima and then water.To measure a volume of solution for analysis, a pipet of 149.4 cc. capacity was built into the constant-temperature bath in such a way that most of the path for transporting the solution from the saturation flask to the pipet was in the water-bath. This system was so arranged that the solution was exposed only to the purified-nitrogen atmosphere.The cell consisted of unplatinized platinum electrodes built into a 300-ec. round flask. The constant was approximately 0.
In the first paper,3 it was mentioned that no complex compounds of high molecular weight amines and metal salts containing a ratio of amine to metal greater than 2:1 could be obtained. However, it has been noted that a solution of a 2:1 complex containing copper becomes a deeper blue upon the addition of an excess of the corresponding amine. With the thought that compounds other than the 2:1 complex might exist in solution, we have here attempted to apply the Method of Continuous Variations as expanded by Vosburgh and Cooper4 to the dodecylaminecupric acetate system. ExperimentalStarting Materials.-Dodecylamine and cupric acetate were prepared as described earlier.3 Reagent-grade trichloromethane and absolute ethanol were used throughout.Instrument.-The optical density measurements were performed in a Beckman Photoelectric Spectrophotometer, Model DU, with a cell length of one centimeter.Data.-Seven solutions, all 0.001 M with respect to cupric acetate and ranging from zero to 0,006 M with respect to dodecylamine, were made up in a solvent comprising 90% of trichloromethane and 10% of ethanol by volume. The absorption spectra of these solutions were
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