The Cross and Bevan Color Reaction

A chlorine solution is prepared by bubbling chlorine gas into ice-cold water. This solution is added to wood meal or wood slices in a small glass-stoppered Erlenmeyer flask. After 10min, the solution is discarded and the sample is rinsed twice with water. On subsequent treatment with 4% sodium sulfite solution, color appears which is similar to that observed in the Maule reaction, 

4 Color Reaction with Tosyl Chloride I Pyridine, p-Nitrosodimethylanilinel Potassium Cyanide 

Freshly prepared wood slices are treated with a solution of tosyl chloride (2 g) in pyridine (20 ml) for 24 h at room temperature. The wood slices are washed successively with benzene, ethanol, dilute hydrochloric acid, and water, and then treated with a solution of p-nitrosodimethylaniline (1.1 g) and potassium cyanide (0.9g) in 85% aqueous ethanol (20ml) for 1.5h. The wood slices turn reddish purple (2max 475 nm) and, after they are washed successively with ethanol and benzene, the color is recorded while the material is still wet with benzene. 

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