Reaction CL.—Action of Sulphites and Bisulphites on Substituted Hydrocarbons

Halogens in the side chain of aromatic compounds also undergo this reaction. 

51 gms. sulphanilic acid (100%) are dissolved in 200 c.cs. water a 16 gms. caustic soda. Any aniline which may be present is boiled ov- 

The solution is filtered and cooled, and 35 gms. cone, sulphuric acid are added. The whole is then cooled to 12° (external cooling), and treated with a solution of 21 gms. sodium nitrite in 50 c.cs. water during i hour with continuous stirring until a distinct and permanent reaction is given with starch-iodide paper. The diazo sulphanilic acid separates out as fine crystals, which are filtered off, but not dried. 

—90% theoretical (47 gms.). Crystallises with H O soluble in hot water alkali salts readily soluble important intermediate for dyes. (B., 18, 3172 A., 190, 69.) 

101 gms. dinitrochlorobenzene are dissolved in 250 c.cs. of methylated spirits. To this is added 40 gms. S02, in the form of a cone, solution of sodium sulphite—about 160 gms. NaHSOs, containing 25% S02 mixed with 50 gms. 40% NaOH until alkaline to phenolphthalein. The sulphite may separate out, even when the mixture is hot, but this is of no consequence. The mixture is heated on the water bath to boiling for 5 hours with good stirring. The product is then cooled, and the sodium salt of the dinitrobenzene sulphonic acid separates in glistening, yellow leaflets. 

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