All other soaps result from the combination' of fatty oils and fat with potash or soda solutions under conditions which favour saponification.
A few of the blubber oils, like dolphin jaw and porpoise jaw oils (used for lubricating typewriting machines), have exceedingly high saponification values ` owing to their containing volatile fatty acids with a small number of carbon atoms. Notable also are coco-nut and palm-nut oils, the saponification numbers of which vary from 240 to 260, and especially butter-fat, which has a saponification value of about 227.
Thus in cows' butter, tributyrin, C 3 H 5 (O C 4 H 7 0) 3, and the analogous glycerides of other readily volatile acids closely resembling butyric acid, are present in small quantity; the production of these acids on saponification and distillation with dilute sulphuric acid is utilized as a test of a purity of butter as sold.
The simplest modes of preparing pure glycerin are based on the saponification of fats, either by alkalis or by superheated steam, and on the circumstance that, although glycerin cannot be distilled by itself under the ordinary pressure without decomposition, it can be readily volatilized in a current of superheated steam.
Their formation is not due to a true process of saponification; but they occupy an important place in compound soaps.