CHAPTER IV. 

 THE FATS AND SUBSTANCES RELATED TO THEM. 



In nature we find a large number of esters composed of 

 the fatty acids united to glyceryl. These are the ordinary 

 fats and as foodstuffs they are nearly as important *as the 

 carbohydrates. In structure they are practically all of the type 

 C 3 H 5 (C n H 2n _ 1 O 2 )3, but include bodies of widely different 

 physical properties. Some are liquids, while others at the 

 ordinary temperature are hard solids. Nearly all vegetable 

 products contain fats of some kind; often the amount is very 

 small, but frequently it constitutes fully 50 per cent by weight 

 of the seed, nut or fruit in question. In the animal kingdom 

 fats are always present, in some amount, in all organisms. 

 The animal fats are often derived from the vegetable fats con- 

 sumed as food. 



THE NATURAL FATS. 



The important fatty acids combined with the radical of 

 glycerol, C 3 H 5 (OH) 3 , are given in the following table. The 

 combinations are essentially like that illustrated by this struc- 

 tural formula of stearin : 



CH 2 O CisHaO 

 CH O CisHssO 



CH 2 O-CasHssO 



SATURATED ACIDS, CH 2 2 . 



Formic acid, HCHO 2 \ 



Acetic acid, HC2H 3 O 2 [ glycerides not natural substances. 



Propionic acid, HC 3 H 5 O 2 ' 



Butyric acid, HGHrOa, occurs in butter fat as glyceride. 



Pentoic acid, HC 5 H 9 O 2 , valeric acid occurs as a natural compound. 



Caproic acid, HCHuO 2 , in butter fat as glyceride. 



CEnanthylic acid, HC7H 13 O 2 , does not occur as glyceride. 



