202 MR. E. SCHUNCK ON THE 



in boiling water and is easily soluble in alcohol, but 

 does not crystallise when the solution is evaporated. Like 

 the indirubine from indican it is quite insoluble in alkaline 

 liquids, but dissolves easily when a deoxidising agent, such 

 as grape sugar or a protosalt of iron or tin, is added at the 

 same time. If it be treated for instance with a solution of 

 protoxide of tin in an excess of caustic soda it dissolves 

 rapidly, forming a yellow solution, the surface of which on 

 exposure to the air instantly becomes covered with a film of 

 regenerated indirubine, the appearance being exactly like that 

 of an indigo vat, except that the film floating on the sur- 

 face is purple instead of blue. If a piece of calico be dipped 

 into the solution and then exposed to the air it acquires a 

 purple colour, which is not removed either by acids or soap. 

 This colour has no great intensity, but by working on a 

 larger scale it is probable that shades of purple equal in 

 depth to those produced by indigo-blue might be obtained. 

 When the solution is mixed with an excess of muriatic acid 

 it gives a dirty yellow precipitate, which after filtration and 

 exposure to the air slowly becomes purple. By long con- 

 tinued exposure of the solution to the atmosphere the whole 

 of the indirubine dissolved in it is again deposited as a purple 

 mass, which is sometimes found to consist of small crystalline 

 needles. When heated in a tube with soda-lime the substance 

 emits fumes having a smell like that of benzol and an alkaline 

 reaction, which condense on the colder parts of the tube to a 

 sublimate, consisting partly of oil and partly of crystalline 

 needles. It is not precipitated from its alcoholic solution by 

 acetate of lead, even when ammonia is added at the same time. 

 These reactions seem to me to prove the identity of this body 

 with the indirubine from indican, which if it could be entirely 

 freed from all impurities would no doubt exhibit the same 

 property of crystallising and of volatilising without residue. * 



• When dry woad leaves are extracted with cold alcohol, the sides of the 

 glass vessel containing the extract generally become covered with patches of 



