226 MR. E. SCHUNCK ON THE 



Action of Alkalies on Indican. 



In the first part of this paper I have described in general 

 terms the effect produced on indican by alkalies. I shall 

 now proceed to give a more detailed account of this process 

 of decomposition and of the products, to which it gives rise. 



When a watery solution of indican is mixed with caustic 

 soda it turns of a dark yellow colour, but no further apparent 

 change takes place. If however, after the mixture has been 

 left to stand for several days, a portion of it be mixed with an 

 excess of sulphuric acid and boiled, it deposits dark flocks, 

 which after being collected on a filter and washed are found 

 to contain no indigo-blue and to be entirely soluble in boiling 

 alcohol. The alcoholic solution has a fine purple colour and 

 gives only a slight precipitate with acetate of lead. Hence 

 it follows that by the action of the alkali indican is converted 

 into a body which by decomposition with acids yields indiru- 

 bine. This body may be prepared in the following manner. 

 A watery solution of indican having been mixed with baryta 

 water is left to stand, until a portion of it on being boiled 

 with an excess of muriatic acid no longer yields indigo-blue 

 but only indirubine. The baryta is then precipitated with 

 sulphuric acid, the excess of the latter is removed by means 

 of carbonate of lead, the liquid is filtered and after sulphu- 

 retted hydrogen has been passed through it, it is filtered 

 again from the precipitated sulphuret of lead and then eva- 

 porated by means of a current of air in the apparatus above 

 described. The dark yellow syrup left after evaporation is 

 treated with alcohol in which a great part dissolves, and the 

 alcoholic solution is then mixed with twice its volume of 

 ether, which causes a milkiness and produces a syrupy de- 

 posit consisting chiefly of indiglucine. The liquid after it 

 has become clear is evaporated spontaneously when it leaves 

 a yellow transparent glutinous residue, having a bitter taste, 

 which cannot be distinguished in outward appearance from 

 indican itself. This residue when dissolved in water and 



