A buffered acetonic solution of a test portion is titrated with a standard volumetric lead(II) nitrate solution in the presence of dithizone as indicator. The method is applicable to anionic surface active agents, containing sodium, ammonium and alkanolamine sulphates. It is not applicable to products containing other compounds such as phosphates or large amounts of chloride nor is it applicable in the presence of large amounts of salts of weak acids (for example, soaps or monoesters of sulphosuccinic acid).