PRODUCTS DERIVED FROM INDIGO-BLUE. 87 



which I made for this purpose,, and which consisted in sub- 

 jecting the body D to the action of caustic soda^ I obtained 

 neither anthranilic acid nor acetic acid, as might have been 

 expected. By evaporating the alkaline solution to dryness, 

 and heating the residue to incipient fusion, the substance 

 was partly converted into a black humus-like matter, in- 

 soluble not only in water and alcohol, but also in alkalies. 

 The alkali was supersaturated with sulphuric acid, and the 

 liquid was distilled, when a trace of what I suppose to be 

 formic acid passed over. The liquid yielded no anthranilic 

 acid. 



In this respect these compounds resemble some of the se- 

 condary products which are formed during the decomposi- 

 tion of indican by acids, and from which no indigo -blue can 

 be obtained, though they must be supposed to contain the 

 elements of that body and of various organic acids, such as 

 formic, acetic, and propionic acids. Indeed, the resem- 

 blance between the two series of compounds extends also 

 to their physical properties. For instance, the body A 

 resembles indifulvine, one of the products derived from 

 indican, both being brownish -yellow resins insoluble in 

 alkalies. B is very similar to indiretine ; and D is so like 

 indifuscine, that the two can hardly be distinguished from 

 one another. There may, in fact, be some analogy in the 

 composition of the two last-named bodies. Indifuscine 

 may, as I have shown on a former occasion, be considered 

 as a compound of indigo-blue and propionic acid minus 

 water, as may be seen by the following equation : — 



Indifuscine. Indigo-blue. Propionic acid. 



C44 H,o N, Oio+2HO=z(Ci6 H, NO,) + 2(0^ H^ OJ. 



In like manner D may be supposed to contain the same 



elements combined in a different proportion, since 



D. Indigo-blue. Propionic acid. 



C,,H,,N,0,o4-ioHO=2(CieH5NO,)-h4(CeHeOJ. 



Analogies such as these, unsupported by experimental 

 proof, may be only fanciful. Nevertheless they may prove 



