62 INTRODUCTION. 



vous matter there exists a phosphorized fat, the composition 

 and properties of which are not very well understood, in 

 union with organic matter. A minute quantity of fat exists 

 in combination with the organic matter of the blood corpus- 

 cles. 



The fats are insoluble in water and in the animal fluids, 

 with the exception perhaps of the bile, which holds a small 

 quantity in solution by virtue of its saponaceous constituents. 

 They are all very soluble in ether and hot alcohol, and but 

 slightly soluble in cold alcohol. The varieties which are solid 

 at the temperature of the body, stearin e and margarine, are 

 easily dissolved by oleine, which is liquid. 



The most marked distinction between the varieties of fat 

 is in their consistence. Oleine is liquid at the temperature 

 of the body, and even at the freezing point of water. Mar- 

 garine is liquid at or above the temperature of 118, and 

 stearine at the temperature of 143 Fahr. The difference in 

 the consistence of adipose tissue of different animals depends 

 upon the relative proportion of the various kinds of fat. 



Saponification. When fat is boiled for a certain time 

 with an alkali, in the presence of water, it undergoes a pecu- 

 liar decomposition which is called saponification. A portion 

 of the water is appropriated, and the fat is converted into 

 glycerine and an acid. The acid is called oleic, margaric, 

 or stearic acid, as it is formed from oleine, margarine, or 

 stearine. In this process the glycerine remains uncombined, 

 and the acid unites with .the alkali to form what is commonly 

 known as a soap. 



This kind of decomposition is called saponification by a 

 base ; but technically, saponification is regarded as any pro- 

 cess by which a fat is decomposed into its acid and glycerine. 

 This may be effected by passing the vapor of water through 

 fat which has been raised to a temperature of 572 Fahr. The 

 action of the strong acids is also to decompose fat. When a 

 small quantity of acid is used, it unites with the glycerine; 



