144 OILY OXIDES, SAPONIFIABLE. 



atom of stearic acid usually combines with two atoms of base. 

 Thus pure stearate of soda is composed of, 



1 atom stearic acid, . = 64 25 



2 atoms soda, . . 8* 



2 atoms water, . . =2.25 



74-5 



If stearin were composed of stearic acid and glycerin alone, its 

 constitution would be, according to the analysis of Liebig and 

 Pelouse, * modified by the subsequent investigations of Redten- 

 bacher and Verrentrapp, f 



2 atoms stearic acid, . C 136 H 132 O 10 = 128-5 



1 atom glycerin, . . C 6 H 7 O 5 = 10-375 



2 atoms water, . H 2 O 2 = 2-25 



C 142 H 141 O 17 = 141-125 



But it is probable that margaric acid, and also oleic acid, &c. are 

 very common ingredients in most varieties of stearin. 



Margaric acid was first described by Chevreul in 1813, under 

 the name of margarin. In 1816 he gave it the name of marga- 

 ric acid. But it was not till 1820 that he was able to distin- 

 guish with precision margaric acid from stearic acid. The mode 

 of obtaining margaric acid employed by Chevreul has been de- 

 tailed in the Chemistry of Inorgaric Bodies, (Vol. ii. p. 125.) 



Dr Redtenbacher first ascertained that, when pure stearic acid 

 is distilled over into a receiver, it is converted into margaric acid. 

 So that the stearic acid from the ox by distillation becomes the 

 acid of human fat Besides margaric acid there was formed mar- 

 garon,and a light oily substance which Redtenbacher called (from 

 its composition) polymo-carburetted hydrogen. 



Varrentrapp found that when ox's tallow, mutton suet, hog's 

 lard, or olive oil were subjected to distillation, the solid products 

 obtained possessed the characters of margaric acid. They were 

 freed from the liquid products of the distillation by pressure, and 

 afterwards purified by repeated solutions in alcohol and crystal- 

 lizations, and finally they were saponified by soda, and precipi- 

 tated by means of muriatic acid. The distilled product contain- 

 ed also margaron and an oily carbohydrogen. 



* Ann. de Chim. et de Phys. Ixiii. 148. 

 f Annalen der Pharm. xxxv. 46. 



