THE FATS. 



The neutral fats are glycerol esters of fatty acids, in that 

 three hydrogens of the carboxyl groups of three fatty acids 

 are replaced by the glycerol radical. A general formula for 

 a neutral fat is represented thus: 



CH 2 -0-OC-R 

 CH-0-OC-R' 



CH 2 -0-OC-R" 



in which R, R', and R" stand for three of the same or 

 different hydrocarbon radicals. In the molecule of the 

 ordinary animal fats R, R', and R" may be represented 

 by three hydrocarbon residues of palmitic, of stearic, of 

 oleic, or of butyric acid, the compounds being designated 

 respectively as tripalmitin, tristearin, etc. 



The specific character of a fat is dependent upon the nature 

 of the fatty acid in the molecule; and since, in general, the 

 melting-points of the saturated fatty acids increase with 

 their carbon content, the lower compounds remain liquid at 

 ordinary temperature and the character of tributyrin (R, 

 R', and R" =C 3 H 7 ) is that of a soft fat, while tristearin (R, R', 

 and R" = C iy H3 5 ) possesses considerable firmness. 



Observe the olive oil, butter, mutton and beef fats pre- 

 sented for study. Pure neutral fats are devoid of color, 

 odor, and taste, and their low specific gravity and insolubility 



