PRODUCTS DERIVED FROM INDIGO-BLUE. 89 



admits of an explanation, which will probably be allowed 

 to be the correct one. By the fermentation of the sugar 

 contained in the madder and other materials employed, 

 alcohol is generated, which in its turn may yield some 

 acetic acid ; and, alcohol, acetic acid, and a base (lime) 

 being present, nothing further is required for the develop- 

 ment of the process above described. By neutralizing a 

 portion of the lime when necessary, the danger of losing 

 colouring-matter is to some extent obviated ; but I would 

 venture to suggest, as a means of rendering it still less, the 

 avoiding all materials containing much sugar or starch — 

 substances which might, by their decomposition, lead to 

 the formation of alcohol. 



When, in the process above described, formiate of soda is 

 employed instead of.acetate of soda, exactly the same phe- 

 nomena are observed. The indigo-blue gradually disap- 

 pears, and a dark brown alcoholic liquid is obtained, which 

 is found to contain bodies closely resembling those formed 

 by means of acetate of soda. By operating on a tolerably 

 large quantity of material, I was enabled to ascertain the 

 presence in this liquid of anthranilic acid, and of three 

 products corresponding to, and having the same physical 

 properties as, the bodies B, D, and E. They were separated 

 from one another by the same means as the latter, the first 

 being a brownish-yellow resin, easily soluble in alcohol 

 and ether, as well as in alkalies ; the second, a brown powder, 

 soluble in alkalies, but soluble with difficulty in alcohol 

 and ether ; whilst the third was a reddish-brown powder, 

 distinguished by its solubility in a boiling solution of 

 acetate of soda — a property which afforded a ready means 

 of separating it from the others. No compounds insoluble 

 in alkalies, and corresponding to the bodies A and C, were " 

 formed with formiate of soda. The analysis of the com- 

 pound resembling B yielded the following results : — 



