ORGANIC COMPOUNDS OF PLANTS 1 99 



Fats are organic salts, the basic part consisting of the 

 glycerol radical C 3 H 5 which is combined with a fatty acid. 

 Glycerin is the basic constituent common to all fats. 

 One fat, as stearin, differs from another, as olein, by 

 containing a different fatty acid in combination with the 

 glycerol radical. When the simple fats are separated into 

 their component parts, the acids formed are : stearic, 

 palmitic, oleic and butyric. 



Some of the fatty acids, as stearic and palmitic, are 

 solids, while others, as butyric, are volatile. Those fatty 

 acids which distil with boiling water are called volatile 

 fatty acids. Butter, for example, contains nearly 5 per 

 cent, of volatile fatty acids, present mainly in the form of 

 butyric acid. Some of the fats undergo fermentation and 

 become rancid, as butterin in butter, while others slowly 

 take up oxygen from the air and undergo oxidation. 

 The chemical and physical properties of the fats in plants 

 and foods are determined by the kinds and amounts of 

 the separate fats present. Olein, stearin and palmitin 

 are always present in larger amounts than are other fats. 



263. Stearin (C 57 H 110 O 6 ) is a solid fat with a high melt- 

 ing-point, 69.4 C. Beef and mutton tallow and animal 

 fats in general are composed mainly of stearin. When 

 pure, it is a white and tasteless body, and has a defi- 

 nite crystalline structure. Stearin predominates in all 

 hard fats. 



264. Palmitin (C 51 H 98 O 6 ) is a white, solid fat obtained 

 from butter, palm oil and human fat. When chemically 

 pure, it is tasteless, and crystallizes in the form of tufts 

 and needles. It has a melting-point of 63 C. Its 



