70 DR. EDWARD SCHUNCK ON SOME 



after some time the liquid acquired a dark-brown colour, 

 and deposited nothing on exposure or agitation. The 

 process was then completed. There sometimes remained 

 a residue of indigo-blue^ which obstinately resisted the ac- 

 tion of the boiling liquid ; but, on pouring off the latter, 

 and adding fresh materials, it generally disappeared rapidly. 

 I found it advisable to employ only a small quantity of 

 indigo-blue at a time, as the process is a slow one, and 

 requires a great excess of alcohol and acetate of soda. 

 The presence of caustic alkali I found to be quite essential, 

 as no perceptible action took place without it; but the 

 quantity required was not large. The stronger the alcohol, 

 and, generally speaking, the freer from water all the sub- 

 stances employed were, the more rapidly was the process 

 completed. 



In order to obtain the products resulting from this 

 process, I proceeded as follows : — The dark-brown alcoholic 

 liquid containing them was first mixed with sulphuric acid 

 until it had acquired a slightly acid reaction, and it was 

 then evaporated. During evaporation, brown resinous 

 masses were deposited ; and on adding water, when the 

 evaporation was nearly completed, a fresh quantity of resin- 

 like matter was thrown down. The liquid filtered from 

 this matter was still brown. It was evaporated to a syrup, 

 which, after standing some time, became solid from the 

 formation of crystals, consisting chiefly of acetate of soda. 

 The whole mass of crystals was then dissolved in boiling 

 alcohol, and tolerably strong sulphuric acid was added to 

 the solution, until no more sulphate of soda was precipitated, 

 care being taken to avoid an excess of the acid. The Kquid, 

 after standing some time, was filtered and evaporated, so 

 as to drive off the acetic acid as well as the alcohol. When 

 the evaporation was nearly completed, water was added, 

 which threw down a large quantity of a brown pulverulent 

 substance, as well as a little brown resin, which, after 



