194 MR. E. SCHUNCK ON THE 



treated with strong acids. If sulphuric or muriatic acid be 

 added to its watery solution, no change whatever is per- 

 ceptible for some time. But on heating to near the boiling 

 point, the solution immediately becomes sky-blue. On boil- 

 ing for a short time, the solution becomes opalescent. On 

 continuing to boil it acquires a purple colour, and then, 

 provided the solution is tolerably concentrated, a copious de- 

 posit consisting of dark purplish-blue flocks is formed. The 

 liquid filtered from these flocks retains a yellow colour and 

 contains a peculiar species of sugar, to which I shall return 

 presently. The flocks themselves do not consist of indigo- 

 blue only. After being collected on a filter and washed with 

 water they appear of a dark purple colour, the filter also 

 acquiring during washing a purple tinge. If they be now 

 treated with alcohol, a part dissolves even in the cold, but 

 to a greater extent on heating, the alcohol acquiring a 

 beautiful purple colour. If the flocks remaining undissolved 

 be treated after filtration with an additional quantity of boil- 

 ing alcohol, the latter acquires a more blueish tinge. Each 

 succeeding portion of alcohol with which the flocks are 

 boiled acquires more and more of a blue colour, until at last 

 the colour is a pure indigo-blue. There remains in general 

 a large quantity of indigo-blue undissolved, and the alcoholic 

 liquids on standing deposit the colouring matter contained 

 in them in the shape of bright blue flocks. The purple 

 alcoholic solution leaves on evaporation a reddish-brown 

 residue, which bears the greatest resemblance to, if it is not 

 identical with, the indigo-red of Berzelius. Like the latter 

 substance it is quite insoluble in caustic alkalies, and gives 

 when heated in a tube purple fumes and a small quantity of 

 a white crystalline sublimate. I propose to call this sub- 

 stance Indiruhine. I have found that it is invariably formed 

 along with indigo-blue whenever indican is decomposed by 

 acids. Nevertheless, the quantity of indigo-blue produced 

 is always relatively larger when the indican is pure, than 



