SUMMARY 105 



transparency and homogeneity. Cellulose bexanitrate is 

 an explosive; cellulose tetranitrate dissolves in alcohol and 

 ether to form collodion; or mixes with camphor to form 

 celluloid. In its original form, as obtained from cotton, 

 trees, or flax, cellulose finds many uses as for cloth, paper, 

 etc. 



The fixed oils are glyceryl salts of the higher fatty acids. 

 They may be liquid or solid, and drying or non-drying, 

 depending on the character of the fatty acid radicle. The 

 drying property is due to the presence of one or more double 

 bonds in the fatty acid molecule, whereby oxygen is absorbed 

 and the oil hardens. These oils decompose on heating, are 

 insoluble in water and in cold alcohol, but are soluble in 

 hot alcohol, ether, and in other volatile organic solvents. 

 They hydrolyze with steam to glycerine and the fatty acids. 

 On treatment with caustic alkalies they "saponify" to a soap 

 and glycerine. The fixed oils are used as foods, for making 

 soap, and for lubricants. 



The volatile oils are never glyceryl salts of fatty acids 

 but may be hydrocarbons; or acids, aldehydes, ketones, and 

 esters of either the aliphatic or carbocyclic series; or may 

 contain sulphur and nitrogen in which case they are sulphides 

 and thiocyanates. They distill unchanged, are insoluble in 

 water, but soluble in cold as well as in hot alcohol and in 

 ether. The volatile oils are used for flavoring, perfumery, 

 and in medicine. 



The resins are solid substances supposed to be derived 

 by oxidation of hydrocarbon volatile oils, and are acids, 

 esters, or resenes. They decompose on heating away from 

 the air, and are soluble in alcohol and in ether. Thev are 

 principally used in making varnishes. 



Rubber, gutta percha, and chicle are similar to resins. The 

 uses of rubber are too well known to need comment. Gutta 

 percha is an excellent insulating material for electric wires, 

 and chicle is used in making chewing gum. 



The nitrogenous compounds are: First, nitrates and 

 ammonia, which are either transitory compounds taken 

 up by the roots, or in the case of ammonia are synthetic or 

 hydrolytic products of proteins. Second, amides and amino- 



