268 CONSIDERATION OF CARBON COMPOUNDS. 



by removal of one or more hydrogen atoms ; methane, CH 4 , 

 for instance, is converted into methyl, CH 3 , which, upon com- 

 bining with hydroxyl, forms methyl alcohol, CH 3 HO. 



Running parallel to the various series of hydrocarbons, we 

 have, therefore, homologous series of alcohols. 



If hydroxyl replaces but one atom of hydrogen in a hydro- 

 carbon, the alcohol is termed monatomic; diatomic and tri- 

 atomic alcohols are formed by replacement of two or three 

 hydrogen atoms respectively. (Diatomic alcohols are also 

 termed glycols.} As an instance of a diatomic alcohol may be 

 mentioned ethylene alcohol, C 2 H 4 2HO, while glycerine, C 3 H 5 3HO, 

 is a triatomic alcohol. 



Alcohols correspond in their composition to the hydrates 

 (or hydroxides) of inorganic substances ; both classes of com- 

 pounds containing hydroxyl, HO, which, in the case of alcohols, 

 is in combination with residues containing carbon and hydrogen, 

 in the case of inorganic hydrates with metals, as, for instance, 

 in potassium hydrate, KHO. 



If we represent any unsaturated hydrocarbon by Al.R. (alco- 

 hol radical), the general formula of the alcohols will be : 



Monatomic alcohol. Diatomic alcohol. Triatomic alcohol. 



/HO 

 HO 

 \HO 

 Or 



AIR'HO A1R.2HO A1RW3HO 



corresponding to 



K'HO Ca2HO Bi iji 3HO. 



Occurrence in nature. Alcohols are not found in nature in a 

 free or uncombined state, but generally in combination with 

 acids as compound ethers. Some plants, for instance, contain 

 compound ethers mixed with volatile oils. The triatomic alco- 

 hol glycerine is a normal constituent of all fats or fatty oils, and 

 is therefore found in some plants and in most animals. 



Formation of alcohols. Alcohols are often produced by fer- 

 mentation (ethyl alcohol from sugar), sometimes by destructive 

 distillation (methyl alcohol from wood) ; they are obtained from 

 compound ethers (which are compounds of acids and alcohols) 



AIR' HO A1R"< X A1R> HO 



