PRODUCTS DERIVED PROM INDIGO-BLUE. 71 



filtration, were added to the resinous matter previously- 

 obtained. The filtered liquid had lost much of its brown 

 colour. I shall return to it presently. 



The products insoluble in water obtained in this manner 

 consist partly of resinous, partly of pulverulent substances. 

 Among these products there are at least five distinct sub- 

 stances, which I have succeeded in separating from one 

 another by the use of various solvents ; but it is probable 

 that small quantities of other substances closely resembling 

 them are also formed at the same time. These bodies are 

 all unfortunately amorphous, and possess very few charac- 

 teristic properties. It is indeed only their origin and mode 

 of formation which impart to them any interest ; and I shall 

 therefore refrain from adding to the already cumbrous 

 mass of terras with which organic chemistry has to deal 

 by inventing names for them, but shall simply distinguish 

 them by the letters of the alphabet. 



The process adopted for the separation of these substances 

 from one another was as follows : — The whole of the mass 

 insoluble in water was first treated with boiling water in 

 order to remove all the sulphate and acetate of soda. It 

 was then dried, finely pounded, and treated with successive 

 doses of ether, as long as anything dissolved. The ethereal 

 liquid, which had a rich reddish-brown colour, was filtered 

 and evaporated, when it left a resin-like residue of the same 

 colour. This residue was digested with weak caustic am- 

 monia, which dissolved a great portion of it. The portion 

 insoluble in ammonia was filtered ofi", washed, dried, and 

 then treated with ether, which generally left a small quan- 

 tity of brown powder undissolved. The filtered ethereal 

 solution was evaporated, and the residue was dissolved in 

 cold alcohol, which left behind a little resinous matter. 

 The filtered liquid left on evaporation a brittle, brownish- 

 yellow resin, which I assume to be an unmixed substance, 

 and shall distinguish by the letter A. The matter dissolved 



