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The solubility of sodium and potassium soaps and the phase diagrams of aqueous potassium soaps

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Journal of the American Oil Chemists Society


Solubility data are provided and collected for the pure sodium and potassium soaps. Hydrolysis obscures the temperatures of solution but is obviated by the presence of a small excess of alkali. Each sodium soap has a large range of temperature between fair and high solubility, whereas the potassium soaps go abruptly into solution, at almost the same temperature and concentration of each soap.

The only soaps that are even moderately soluble at room temperature are potassium laurate, myristate, and oleate, the potassium salt of acids from coconut oil, and the sodium oleate. The other sodium and potassium soaps of the saturated fatty acids require elevated temperatures for solution.

Phase diagrams for the five commonest potassium soaps are developed and recorded.

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This work was the basis of a thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, Stanford University, 1947.

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McBain, J.W., Sierichs, W.C. The solubility of sodium and potassium soaps and the phase diagrams of aqueous potassium soaps. J Am Oil Chem Soc 25, 221–225 (1948).

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