■JIS Dr. Schunck on the Formation of Indigo-blue, 



becomes almost solid without exhibiting a trace of anything cry- 

 stalline. It dissolves in concentrated sulphuric acid in the cold, 

 forming a solution of a greenish-brown Colour, which when 

 heated becomes black and disengages sulphurous acid. It is 

 not much affected by nitric acid of ordinary strength even on 

 boiling, but fuming nitric acid dissolves it readily, even in the 

 cold, giving a dark reddish-yellow solution, which on the addi- 

 tion of water deposits orange-coloured flocks. If the solution in 

 fuming nitric acid be boiled, it gives off nitrous acid, and on eva- 

 poration it leaves a reddish-yellow resinous mass, the greatest 

 part of which, on being treated with boiling water, remains un- 

 dissolved in the shape of a yellowish-red resin, resembling indi- 

 fulvine itself in appearance, but differing from it in being easily 

 soluble in alkaline liquids, and soluble with difficulty in boiling 

 alcohol. The watery liquid filtered from this resin yields on 

 evaporation white needle-shaped crystals, which are not oxalic 

 acid. A boiling solution of bichromate of potash to which sul- 

 phuric acid is added decomposes indifulvine very slowly, the 

 solution becoming green from the reduction of the chromic acid. 

 Chlorine converts indifulvine, when suspended in water, into a 

 body which does not much differ from it in appearance, but is 

 soluble in alkalies. Indifulvine is not precipitated from its alco- 

 holic solution by acetate of lead, even on the addition of ammonia, 

 as indeed might be inferred from its method of preparation. 



Notwithstanding that I worked with tolerable large quantities 

 of the mixed products of decomposition of indican, I obtained 

 only on two occasions a sufficient quantity of pure indifulvine 

 for analysis. The composition on these two occasions was not 

 the same ; so that if the substance was in each case pure, there 

 are, strictly speaking, two bodies having the general properties 

 of indifulvine. Nevertheless the formulae of the two bodies stand 

 in a definite relation to one another and to that of indican, so 

 that in cither case the formation of the substance may easily 

 be explained. 



I. 0-3695 grm., dried at 100° C, gave 0-994.5 grm. carbonic 

 acid and 0-1795 water. 



0-3605 grm. gave 0-4665 grm. chloride of platinum and am- 

 monium. 



These numbers lead to the following composition : — 



