20 PRINCIPLES OF FEEDING FARM ANIMALS 



fats are found in plants and animals. Among these the 

 so-called drying and semi-drying oils are of interest, inas- 

 much as they have the power to dry and harden upon ex- 

 posure to air, hght, and moisture. This is especially true 

 of the drying oils, of which Unseed oil is the most important 

 example. Consequently, the drying oils are used in paint- 

 ing. Cottonseed oil and corn oil are examples of semi- 

 drjdng oils. 



When a fat is heated ^vith an alkah, such as caustic soda, 

 the fat is broken up, setting the glycerin free, and the fatty 

 acid is united with the metal of the alkah to form a soap. 

 This process is called saponification. Advantage is taken 

 of this property of fats in the manufacture of common soap 

 on the farm, the alkah in the lye acting upon the fat of 

 the animal refuse with the formation of soap. Potassium 

 soaps are soft, while sodium soaps are hard. By treating a 

 soap with mineral acid the soap is decomposed and the 

 fatty acid is set free. 



When exposed to the action of moisture, air, and hght, 

 fats gradually acquire a disagreeable odor, an acrid taste, 

 and become acid in reaction. They are then said to be 

 rancid. When ground feedingstuffs containing considerable 

 fat, such as corn meal, soybean meal, oil meal, etc., are 

 stored they gradually become rancid and consequently un- 

 palatable to animals. 



The waxes, such as lanolin, or wool fat, beeswax, and 

 sperm oil, are closely related to the fats. They consist of 

 combinations of fatty acids and some of the higher 

 alcohols. 



The phosphatides, also, are closely related to the fats. In 

 addition to containing fatty acids and glycerin, they also 



