308 CONSIDERATION OF CARBON COMPOUNDS. 



Alcohols correspond in their composition to the hydroxides of 

 inorganic substances ; both classes of compounds containing hydroxyl, 

 OH, which, in the case of alcohols, is in combination with residues 

 containing carbon and hydrogen, in the case of inorganic hydroxides 

 with metals, as, for instance, in potassium hydroxide, KOH. 



If we represent any unsaturated hydrocarbon by ALE. (alcohol 

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



Monatomic alcohol. Diatomic alcohol. Triatomic alcohol. 



/OTT 



Al.Ki-OH ALBtt<7 Al.Eiii OH 



\OH 

 or 



ALKiOH m Al.Eii(OH) 2 ALEUl(OH), 



corresponding to 



KOH Caii(OH) 2 Bim(OH) 3 . 



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

 or uncornbined state, but generally in combination with acids as com- 

 pound ethers. Some plants, for instance, contain compound ethers 

 mixed with volatile oils. The triatomic alcohol glycerin is a normal 

 constituent of all fats or fatty oils, and is therefore found in many 

 plants and in most animals. 



Formation of alcohols. Alcohols are often produced by fermen- 

 tation (ethyl alcohol from sugar), sometimes by destructive distillation 

 (methyl alcohol from w^ood) : they are obtained from compound ethers 

 (which are compounds of acids and alcohols) by treating them with 

 the alkali hydroxides, when the acid enters into combination with 

 the alkali, whilst the alcohols are liberated according to the general 

 formula : 



lc.!> + KOH = Acl> + A1 - E - OH - 



Alcohols may be obtained artificially by various processes, as, for 

 instance, by treating hydrocarbons with chlorine, when the chloride 

 of a hydrocarbon residue is formed, which may be decomposed by 

 alkali hydroxides in order to replace the chlorine by hydroxyl, when 

 an alcohol is formed. For instance : 



C 2 H 6 ^2C1 = C 2 H 5 C1 " + HC1. 

 Ethane. Ethyl chloride. 



C 2 H 5 C1 + KOH = KC1 -f C 2 H 5 OH, 



Ethyl Potassium Potassium Ethyl 



chloride. hydroxide. chloride. alcohol. 



Properties of alcohols. Alcohols are generally colorless, neutral 

 liquids ; some of the higher members are solids, none is gaseous at 



