OXIDATION PRODUCTS OF ALCOHOLS 49 



a solution of potassium permanganate. What does the loss of color 

 of the permanganate show? When formic acid is heated to decom- 

 position with dehydrating agents, it breaks up as follows: 



H-(CO)OH^-CO +H2O 



In the presence of an oxidizing agent like potassium permanganate 

 this decomposition takes place more easily, the CO being oxidized to 

 CO2. 



Acetic Acid 



Acetic acid in addition to its occurrence in nature in the form 

 of esters is produced on a large scale by the oxidizing fermen- 

 tation of the alcohol obtained as the result of fermenting fruit 

 juices, especially apple juice or cider. When cider ferments, 

 due to the action of the enzyme zymase, alcohol is produced. 

 This alcohol is then oxidized through the activity of bacterial 

 organisms, acetic acid bacteria, which are present naturally in the 

 fruit juice, and the product is acetic acid. 



Sugar + Zymase -> Alcohol -f CO2 



CH3 - CH2OH + O2 -^ CH3 - COOH + H2O 



Alcohol Atmospheric Acetic acid 



oxygen + 

 bacterial action 



Glacial Acetic Acid. — This form of the acid has the same 

 relation to ordinary acetic acid that absolute alcohol has to 

 ordinary alcohol, i.e. it is 100 per cent pure. It is obtained 

 from strong acetic acid by fractional distillation. Pure acetic 

 acid crystallizes at 16.7°, and hence its name glacial acetic acid. 

 It is a liquid, boiling point 120°, with a sharp odor and irritating 

 effect upon the skin similar to formic acid, but not so strong. 

 The salts of acetic acid are mostly crystalline compounds, the 

 important ones being those of sodium, potassium, ammonium, 

 calcium, iron, aluminium, copper and lead. The iron and 

 aluminium acetates are used as mordants in dyeing. The 

 copper acetate is a constituent of several insecticides (Paris 

 green, etc.), and the lead acetates are used in medicine. 



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