Reaction CLXXI.—Action of Alkali Sulphides and Hydrosulphides on Nitro Compounds

Reaction CLXXI. Action of Alkali Sulphides and Hydrosulphides on Nitro Compounds. 

Excess of Na2S is used, which dissolves the sulphur always formed in the reaction, due to oxidation. The reaction is specially useful in cases of nitro compounds containing more than one nitro group, and conditions can be chosen such that only one nitro group is reduced, e.g., 

The reaction is really an extension of that on alkaline reduction, since the solution of sodium sulphide in water is alkaline. The complete equations are  

This experiment should be performed in a fume cupboard. 

10 gms. picric acid and 3-5 gms. of caustic soda are dissolved in 600 c.cs. water in a large flask and heated up to 55° with vigorous stirring, when a solution of 40 gms. crystalline sodium sulphide (Na2S.9H20) in 100 c.cs. water is gradually added. 

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