ORGANIC COMPOUNDS 23 



forming >by weight about 75 per cent., while oxygen is 

 present in very small amounts. The fat found in 

 animals is a mixture of three neutral fats stearin, 

 palmitin, and olein. Each fat is derived from glycerin 

 and the acid indicated by its name e. g., oleic acid, 

 in the case of olein, etc. 



When we speak of saponification we mean that a neu- 

 tral fat has been treated with a superheated steam 

 or saponified i. e., broken up into glycerin and a 

 fatty acid, as stearic, oleic, or palmitic, the resulting 

 acid depending on the neutral fat used. 



Soaps. Soaps are formed when saponification takes 

 place in the presence of an alkali e. g., potassium or 

 sodium hydroxid the acid combines with the alkali 

 to form a salt known as soap, the glycerin remaining 

 in solution. 



Soaps are salts. Soaps made with sodium hydroxid 

 are hard, those with potassium hydroxid are soft. 

 Those derived from stearin and palmitin are harder 

 than those made with olein. 



The Animal Fats. Butter, cream, lard, suet, oleo- 

 margarin, cottolene, butterine, cod-liver oil, and 

 bone-marrow are the animal fats of the most import- 

 ance. 



The Vegetable Fats. Those most commonly em- 

 ployed are olive oil, cotton-seed oil, linseed oil, 

 cocoa-butter, and the oils derived from nuts, such 

 as cocoanut oil, peanut oil, and almond oil. 



The Proteins. Proteins are found in both animals 

 and vegetables, and contain most of the nitrogenous 

 compounds essential for their physiologic needs. In 

 the former they are found as constituents of the blood, 

 tissues, bones, muscles, nerves, glands, and all other 

 organs; in the latter, in nearly all parts of plants 

 and seeds. They are represented in the vegetable 

 food which we eat, as constituents of gluten of grain, 

 etc. ; in the animal food, as the lean and gristle of beef, 

 the white of egg, casein of milk (the curd), etc. 



