162 SAPONIFICATION. [ VI. 



2. Saponification. 



Soap-boiling consists in boiling a fat with alkali and water, 

 whereby the fat acid unites with the alkali to form a soap, and 

 glycerin is set free. The soft soaps usually contain the 

 glycerin, but it is removed from the hard soaps, and remains 

 in the saline solution. Soaps retain variable quantities of 

 water, even to 30 per cent, and more, when they appear to 

 be dry. Rosin is usually added to make the common yellow 

 soaps, but it can hardly be called an adulteration, as it pos- 

 sesses some detergent properties. 



Irish Moss and Salt in Soap. — (Lond. Journ. 1849, 37.) 

 To a strong solution of Irish moss (lib to 6 galls, water), 

 made by a short ebullition and maceration for several hours, 

 and run through sieves, a quantity of common salt is added, 

 1ft) to each 4 galls., and stirred until dissolved. One ton of 

 this mixture is combined with 5 tons of soap. The utility of 

 this compound is not clear. 



Oily Acids, — When wool is cleaned by alkali in water, a 

 portion of fat is removed, and in order to get the oily acids 

 again from the water, Shearman treats the water with sul- 

 phuric or muriatic acid, heats the fat acid, separated from the 

 liquid, to 212° in a leaden vessel, saturates the free acid with 

 chalk, adds hot water, stirs, and lets it settle for several days, 

 when the fat can be drawn off clear. It may be reconverted 

 into soap by alkali. 



Perfumery is allied to soap-boiling, which in fact forms 

 part of this art, since one of its most extended applicatioip^s 

 is to perfume soap. The perfumes are essential oils, some- 

 times solid ; usually derived from the distillation of odorous 

 plants or parts of plants. Many of them are simple com- 

 pounds of carbon and hydrogen ; others contain also oxygen, 

 and a few sulphur. It is probable that we shall be enabled to 

 make some of them artificially on a large scale ; for through 

 the interesting experiments of Wohler and Liebig, it was shown 

 how oil of bitter almonds was formed ; through those of 



