VI. OLEICS. 



Although some fatty bodies are very different from others 

 in their chemical nature, and all of them differ from the 

 essential oils, yet being often used in the same branch of 

 manufacture indiscriminately, they may be embraced together 

 as a class. 



1. Oils and Fats. 



By far the larger proportion of oils and fats agree in being 

 composed of a fat acid united to a base called glycerin. The 

 three principal acids are stearic, margaric and oleic ; when 

 stearate or margarate of glycerin predominate (the compound 

 being called stearin or margarin), the fat is more solid, as 

 tallow, suet, &c. ; when oleate of glycerin (called also olein) 

 is in sufficient quantity, the fat is fluid or oily, as olive oil. 

 The chemical connection between margaric acid, which is a solid 

 crystalline fat, and vinegar or acetic acid, and the connection 

 between acetic acid and common alcohol, are pointed out in an 

 essay by one of us, published in the Journ. Fr. Inst. 1848. 

 Now since formic, acetic, and valeric acids can be shown to 

 be derived from wood-spirit, common alcohol, and fousel-oil, 

 which are their respective alcohols, we may infer that the 

 higher fat acids have also their alcohols. The investigations of 

 Brodie in wax seem to point out such alcohols and their acids. 

 The general formula for this fat acid series, the most ex- 

 tended series yet developed in organic chemistry, is CnHnOi, 

 n being an even number (see below). No well-defined con- 

 nection has yet been established between other fat acids not 

 belonging to this group. 



Coeoanut Oil. — According to Georgey (Ann. der Chem, 

 und Pharm. Ixvi.) the butter of cocoa contains the following 

 acids : 



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