Structure of Simpler Organic Compounds. 79 



alcohol, CH 2 : CH CH 2 OH, which can be prepared by the 

 distillation of glycerol with oxalic acid. (The reaction is 

 somewhat complex.) It has the properties both of an 

 unsaturated substance (for example, can give addition pro- 

 ducts) and of an alcohol (can give sodium derivatives, etc.). 



Part IV. The Aldehydes. 



When a primary alcohol is submitted to oxidation 

 under certain conditions, it gives rise to a product known 

 as an aldehyde (see p. 70) 



ECH 2 OH + = H 2 O + R-CHO 



Ethyl alcohol under these conditions gives rise to the 

 typical substance of this class, which is generally known 

 as acetaldehyde 



The oxidizing reagent generally employed for this 

 purpose is a mixture of potassium dichromate and sul- 

 phuric acid. The product of the reaction is a volatile 

 liquid, boiling point 20-8, which possesses a characteristic 

 pungent odour and is miscible with water, alcohol, and 

 ether in all proportions. 



The lower member of the series, which is prepared 

 by the oxidation of methyl alcohol, is known as formal- 

 dehyde, which, in 40 per cent, solution, is sold as a disin- 

 fectant under the name of formalin. This substance is 

 usually prepared by passing the vapour of methyl alcohol 

 mixed with air through a tube containing a copper spiral, 

 or platinized asbestos, heated to dull redness. 



2CH 3 OH + 2 = 2H-CHO + 2H 2 



Formic aldehyde is also a substance of intense pene- 

 trating odour, which is gaseous at ordinary temperatures, 

 but can be condensed to a liquid at 21. It readily 



