190 lOt. E. SCHUNCK ON THE 



of the two formulae given above, the first, viz., C 52 H 3l N0 34 

 approaches nearest to, if it is not a correct representation of 

 its true composition. The formula C 52 H^ NO^ may then 

 represent a mixture of indican with a small quantity of what 

 may be called its hydrate, or it may show the composition of 

 indican in the first stage of its hydration before it has lost 

 the property of yielding indigo-blue by decomposition. As 

 far as regards the explanation of the different processes of 

 decomposition which the substance undergoes, it is of course 

 immaterial which formula is adopted. 



Action of Acids on Indican. 



In the first part of this memoir I have given a general 

 description of the process of decomposition which indican 

 undergoes by the action of acids and of the products thereby 

 formed. I shall now proceed to give an account of the results 

 obtained in a more minute investigation of this process, per- 

 formed with larger quantities of material than had previously 

 been at my disposal. 



Sulphuric and muriatic acids are not the only acids capable 

 of effecting the decomposition of indican. If to a watery 

 solution of the latter a small quantity of nitric acid be added, 

 the quantity of the acid not being large enough to enable it 

 to exert any oxidising action on the indican, the solution im- 

 mediately becomes green and turbid, and on standing it 

 deposits flocks of a dark colour, while the surface becomes 

 covered with a blue pellicle. The deposit is found to consist 

 principally of indigo-blue with a little indirubine and a trace 

 of other products of decomposition. The filtered liquid on 

 being boiled becomes muddy and deposits some brown flocks, 

 which contain no indigo-blue. The quantity of indigo-blue 

 formed by the action of nitric acid seems indeed to be compara- 

 tively larger than when sulphuric or muriatic acid is employed. 

 It is hardly necessary to add, that if this be really the case, it 

 cannot be ascribed to any oxidising effect produced by the 



