Unsaponified and unsaponifiable determinations as applied to incompletely saponified soaps

Unsaponified and unsaponifiable determinations were made on toilet bar soap, potash vegetable oil paste soap, yellow laundry soap and hardwater cocoa bar soap according to the method of (1) the American Oil Chemists’ Society, and (2) the Society of Public Analysts (British). The results obtained by the two methods were comparable for toilet bar soap, potash vegetable oil paste soap and yellow laundry soap. The unsaponifiable matter in hardwater cocoa bar soap, however, appeared considerably lower when determined by the A. O. C. S. method than when determined by the S. P. A. method. Extraction of unsaponified matter in the former method is by petroleum ether; in the latter method by ethyl ether. In order to determine whether the difference in results could be traced to the difference in solvents, extraction with petroleum ether in the A. O. C. S. method was followed by extraction with ethyl ether. The weight of unsaponified matter (50 gram sample) was increased thereby from 0.791 g. to 1.423 g. The saponification value of the ethyl ether extract under the A. O. C. S. method tended to show that practically all of the additional material extracted with ethyl ether was made up of mono and diglycerides with the mono predominating.