ALCOHOLS. 



Alcohols are hydrocarbons in which a hydrogen atom (or more in 

 the case of the higher members, e.g. glycerol) has been substituted by 

 a hydroxyl or OH group. This relationship is shown : 



1. By the action of water and aqueous alkalies upon the halogen 

 mono-substituted hydrocarbons : 



CH 3 . Cl + HOH = HCl + CH 3 . OH. 



2. By the action of phosphorus pentachloride upon the alcohol : 



CH 3 . OH + PC1 5 = CH 3 . Cl + POC1 3 + HCl. 



All alcohols are designated by the suffix -ol, e.g. methyl alcohol 

 or methanol, ethyl alcohol or ethanol. 



Most of the alcohols are natural substances and serve as the start- 

 ing point for the preparation of other compounds. 



METHYL ALCOHOL. CH 3 . OH. 

 Commercial Methyl Alcohol. 



Preparation. 



Methyl alcohol, together with acetone, acetic acid, methyl acetate 

 and other substances is formed in the dry distillation of wood. The 

 acid. aqueous distillate is known as pyroligneous acid; on standing 

 wood tar separates out The acid liquid contains 1-2 per cent, of 

 methyl alcohol, '!-'$ per cent, of acetone and about 10 per cent, of 

 acetic acid. It is distilled until the distillate has a specific gravity of 

 9-1. The crude wood spirit so obtained is a greenish-yellow liquid 

 with disagreeable odour. It is mixed with about 2 per cent, of lime 

 and again distilled. This retains the acetic acid as calcium acetate, 

 the neutral substances methyl alcohol, acetone, acetaldehyde, methyl 

 acetate passing ovef. This distillate is wood spirit and contains about 

 93 per cent, of methyl alcohol. It is diluted with water to precipitate 

 oily impurities and is again treated with lime and distilled. Basic 

 impurities are removed by distilling it with -I -'2 per cent, of sul- 

 phuric acid and the methyl alcohol boiling at 64-66 is collected. 



Methyl alcohol is also prepared by dry distillation from vinasses- 

 the mass remaining after fermentation of the residues from the pn 



paration of beet sugar. 



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