244 HALOIDS AND HALOID BASES. 



we can decide whether this conjecture is of any real value. The 

 uses of fatty articles of food would thus assume a new aspect, since 

 they would in this way contribute to the formation of the free acids 

 which act so important a part in many of the processes of animal 

 chemistry. 



How the glycerine in the yolk of egg and in the brain becomes 

 associated with the phosphoric acid, we cannot specially explain, 

 but, considering the frequency with which phosphorus occurs, both 

 in its unoxidised state and as phosphoric acid, there is nothing 

 singular or inexplicable in such a combination. 



SALTS OF OXIDE OF LIPYL. FATS. 



Chemical Relations. 



General Properties. It is especially worthy of remark that the 

 properties of these haloids are almost entirely influenced by the 

 acids contained in them ; while in the salts of oxide of ethyl, most of 

 the properties, including those of the most general character, 

 appear to depend principally on the base, and to be altogether in- 

 dependent of the nature of the acid. Hence we find the properties 

 of the neutral fats to be extremely similar to those of the fatty acids 

 already described (from p. 105 to p. 116.) 



Most of the animal fats are soft and greasy at an ordinary 

 temperature, although some are firm and waxy, and a few liquid ; 

 they almost all correspond, however, in the following points. When 

 exposed to strong cold, especially when in solution in alcohol, they 

 may be obtained in white scales or minute plates of a peculiar 

 lustre ; when perfectly pure, they are for the most part colourless 

 and transparent, they swim on water, render paper and linen trans- 

 parent, are bad conductors of electricity and heat, melt for the most 

 part below the boiling point of water, are altogether decomposed 

 when distilled, unless the process be conducted in vacuo, and are 

 devoid of smell and taste when they are pure and fresh ; they are 

 insoluble in water, but most of them dissolve in boiling alcohol, 

 from which they again separate on cooling ; they are all soluble in 

 ether and in volatile oils ; when perfectly pure they exert no re- 

 action on vegetable colours, but on exposure to the air many of them 

 readily become rancid and acid from the absorption of large 

 quantities of oxygen. When exposed to a strong heat, and free 

 access of oxyen is admitted, they are inflammable, and burn with 

 a clear flame. 



