The effect of some inorganic salts in dilute solution on the formation of calcium and magnesium soaps

Summary The reactions in mixtures of dilute solutions of builders, pure soaps and hard water have been examined under conditions for optimum foam stability for the soap solution. An attempt has been made to interpret these reactions on the basis of solubility products. For dilute solutions of soaps of pure fatty acids a minimum mole ratio of builder to calcium or magnesium salts is required to prevent the formation of alkaline earth soaps. These mole ratios are different for each soap studied and vary with the particular calcium or magnesium salt and builder combinations. The procedure used by previous investigators of this subject is discussed. The authors wish to express their appreciation to C. W. Jakob for performing many of the determinations upon which this paper is based.