Studies in the properties of bivalent metal oleates-Part I

Abstract

Different samples of zinc and magnesium oleates were prepared by varying the amounts of the electrolyte and the monovalent soap. As a result of the analysis of the samples thus prepared, it is observed that the metal and the acid are not present in stoichiometric ratios except in the case of zinc oleate obtained by refluxing zinc dust and oleic acid. This sample of zinc oleate melts at 85·5° C. while the other samples melt at a much lower temperature. Similar behaviour is observed in the case of magnesium oleate. It has been suggested that these variations are due to the adsorption of various ions by the metal soaps formed. A study of other physical properties such as solubility, molecular complexity, surface tension, viscosity, electric conductivity, and molecular magnetic rotation using benzene as solvent reveals that the behaviour of magnesium oleate is different from that of zinc oleate inasmuch as it shows conductivity, abnormally high molecular weight, comparatively higher viscosity, a greater lowering of interfacial tension and a variation of molecular magnetic rotation with change in concentration. Riedel from a study of the viscosity of metal soaps concluded that these soaps could not be treated as colloidal electrolytes but that they behaved more like gels. The difference in behaviour of zinc and magnesium oleates, however, suggests that whereas zinc oleate may be regarded as a gel, magnesium oleate behaves more like a colloidal electrolyte. © 1939 Indian Academy of Sciences.