THE FATS. 23 



THE FATS. 



The fats occur in both plants and animals. When pure 

 they are colorless, odorless, and tasteless. They are in- 

 soluble in water and have a lower specific gravity. They 

 dissolve in hot alcohol more easily than in cold, and are 

 easily soluble in ether, gasolin, or benzene. The fats mix 

 with water when the two are shaken violently together, but 

 they soon separate, the fats going to the top. If, however, 

 something like soap or a solution of albumin is added to 

 the mixture which will form a coating around the minute 

 globules of fat, they are prevented from reuniting, and 

 form an emulsion, that is, a mixture of small fat-globules 

 with the liquid, not a solution. It is destroyed by anything 

 which will remove the coating, the fat separating again 

 from the liquid. 



The fats are composed of three elements: carbon, 

 hydrogen, and oxygen. They contain a much smaller per- 

 centage of oxygen than the carbohydrates, the hydrogen 

 and oxygen not being in the proportion to form water. 

 When the fats are kept at the temperature of superheated 

 steam or subjected to the action of the pancreatic ferment, 

 they take up water and are split into two compounds: 

 glycerin, on the one hand, and one or more of the fatty 

 acids, on the other. Thus, stearin gives 



C 3 H 5 (C ]8 H 36 2 ) 3 + 3H 2 = C 3 H 5 (OH) 3 + 3C 17 H 35 C0 2 H. 



stearin -f- water = glycerin + stearic acid 



They may be considered then as made up of glycerin 

 and a fatty acid less water. 



This splitting up of the fat-molecule is called saponifi- 

 cation. It occurs when fats become rancid. It can be also 



