PRODUCTS DERIVED FROM INDIGO-BLUE. 73 



caustic soda-lye, in which one of the three was found to be 

 insoluble. The alkaline liquid, which was of a dark-brown 

 colour, was filtered, and the residue left undissolved was 

 again treated with alkali in order to remove the whole of 

 the soluble portion, and it was then treated with a boiling 

 alcoholic solution of caustic soda, in which the greatest part 

 dissolved with ease. The dark-brown solution was filtered 

 and then mixed with an excess of hydrochloric acid, which 

 precipitated the greatest part of the substance as a dark- 

 brown powder. This was collected on a filter, washed with 

 alcohol until all the acid and chloride of sodium were re- 

 moved and dried. This body I will distinguish by the 

 letter C. The caustic soda-lye contained the two other 

 substances in solution, and it was accordingly mixed with 

 an excess of acid, which produced an abundant brown 

 flocculent precipitate. This was collected on a filter, well 

 washed with water, and then treated with a boiling solu- 

 tion of acetate of soda, which dissolved part of it, thereby 

 acquiring a brown colour. The liquid was filtered boiling 

 hot, and the residue was treated with fresh solution of 

 acetate of soda, the process being repeated as long as the 

 boiling liquid acquired any colour. The residue left un- 

 dissolved by the acetate of soda was treated with boiling 

 alcohol containing a little ammonia, in which it dissolved 

 with ease, forming a dark-brown solution, from which the 

 greatest part was again precipitated on the addition of an 

 excess of hydrochloric acid as a brown powder. This was 

 filtered ofi', well washed with alcohol,»and dried. This body 

 may be denoted by the letter D. The substance held in 

 solution by the acetate of soda was precipitated by sul- 

 phuric acid in brown flocks, which were filtered off, well 

 washed with water, and then treated with boiling alcohol, 

 in which they dissolved completely. The alcoholic solution 

 deposited, on cooling, a brown powder, which was collected 

 on a filter, washed with a little cold alcohol, and dried. 



