Determination of Sodium Oleate in Dilute Aqueous Solution

Abstract

THERE is no simple, satisfactory method for determining small amounts (<10⁻³M) of carboxylic soaps in aqueous solution. On the other hand, there are several methods of estimating synthetic ionic detergents, such as long-chain alkyl sulphates and quaternary ammonium salts. Of particular interest is the method of Epton¹, in which the titration of anionic against cationic detergent is carried out using a partition end-point with methylene blue as indicator. We have now found that sodium oleate can be estimated by a modification of this method, if certain precautions are taken. Considerations of solubility led us to choose sodium oleate to illustrate the method, although it is clearly applicable to other soaps of similar constitution.