94 THE CHEMISTRY OF CATTLE FEEDING 



origin, might be mentioned, but the examples given above 

 must suffice, as they are of minor importance from the present 

 point of view. 



Waxes. Waxes are unctuous substances very similar to 

 the fats in appearance and general properties. The specific 

 gravity is low, but is generally higher than that of the fats, and 

 the melting points are usually higher. The vegetable waxes 

 are found chiefly as a thin covering, or bloom, on the surfaces 

 of leaves, fruits, and seeds wheat, maize, peas, etc. and in 

 larger amounts in the substance of bark and cork. Their 

 presence serves to protect the tissues from the solvent action 

 of water and to increase resistance to hydrolytic changes. 

 They are insoluble, but readily form emulsions in water, and 

 they can be softened by admixture of considerable quantities 

 of that substance. 



Waxes are often defined as ethereal compounds of fatty 

 acids with monatomic alcohols of high molecular weight. The 

 natural waxes, however, are not as a rule homogeneous com- 

 pounds, but mixtures. Various hydrocarbons, free fatty acids, 

 and alcohols are often associated with the ethereal compounds. 

 The ethereal compounds are, of course, saponifiable by the 

 action of alkalis. They yield soaps, but no glycerine. 



The fatty acids which are most commonly present belong 

 to the acetic series, and contain from about 12 to 30 atoms 

 of carbon ; unsaturated and hydroxy acids also occur. The 

 alcohols have a similar range of carbon atoms, and most of 

 them are saturated compounds. Some waxes, however, contain 

 unsaturated alcohols, and dihydric compounds (glycols) are 

 also known to occur. Spermaceti, which is regarded as a typical 

 wax, consists mainly of cetyl palmitate, C 16 H 31 O 2 .C 16 H33. 

 The ethereal compound which forms the larger part of Chinese 

 wax is known as ceryl cerotic ester, of which the formula is 



27^5302^27^5. 



Waxes are normally present in admixture with many of the 

 natural fats. To a large extent they are soluble in the same 

 solvents. Fats and waxes are, therefore, extracted together, 

 and are not easily separated. The crude ether extract, 

 obtained in the ordinary course of analysis of feeding stuffs 



