derived from Indigo-blue. 297 



Among these products there are at least five distinct sub- 

 stances, which I have succeeded in separating from one 

 another hy 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 character- 

 istic properties. It is indeed only their origin and mod.e of 

 formation which impart to them any interest; and I shall 

 therefore refrain from adding to the already cumbrous mass of 

 terms with which organic chemistry has to deal by invent- 

 ing 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 off, washed, dried, and 

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

 tity of brown powder undissolved. The filtered ethereal so- 

 lution 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 by the am- 

 monia was precipitated by acid in thick flocks, which, after 

 being filtered off, washed, and dried, were treated with ether. 

 The ether left some brown powder undissolved, which was 

 separated by filtration. The liquid was evaporated, and the 

 residue was treated again with ether, in order to separate 

 a little more of the brown powder. The substance was then 

 introduced into a hot solution of carbonate of ammonia, which, 

 if not too concentrated, dissolved the greatest part of it, leaving 

 only some brown powder behind. If, as sometimes happened, 

 the solution of carbonate of ammonia was not sufficiently di- 

 lute, very little was dissolved by it, the greatest part of the 

 substance sinking to the bottom of the vessel as a viscid resi- 

 nous mass, which dissolved, however, almost entirely on pour- 

 ing off the liquid and adding pure water. The addition of 

 acid to the filtered solution produced a brown flocculent pre- 

 cipitate; which was filtered off, washed with water, and treated 



