200 MR. E. SCHUNCK ON THE 



The green muddy liquid was then strained as quickly as pos- 

 sible through canvas, and left to stand exposed to the air in a 

 shallow vessel. The surface of the liquid soon became covered 

 with a purple pellicle, which was carefully skimmed off and 

 was succeeded by another, which was in its turn removed, 

 the process being repeated as long as anything formed on the 

 surface. The purple matter was then dissolved a second time 

 in an alkaline solution of protoxide of tin and the solution 

 was again left exposed to the atmosphere. The pellicle 

 which was formed by the action of the oxygen was removed 

 this time by means of blotting paper, to which it adhered 

 without much of the liquid underneath being removed with 

 it. The substance was separated from the paper by agitation 

 in water, collected on a filter, treated with boiling caustic soda 

 to dissolve a little adhering fatty matter, filtered off again, 

 washed with acid, then with water, and lastly dissolved in 

 boiling alcohol. The alcohol acquired a splendid purple 

 colour and on cooling deposited a quantity of crystalline 

 needles, consisting, as I believe, of indirubine in a state of 

 purity. When thus prepared it is found to have the follow- 

 ing properties. 



It crystallises from its alcoholic solution in small needles 

 forming when dry a silky mass of a colour between purple 

 and chocolate, which on being rubbed with a hard body shows 

 a slight metallic lustre, resembling that of bronze. When 

 heated on platinum foil it emits red vapours, then melts and 

 burns with a yellow smoky flame leaving some charcoal. 

 W T hen carefully heated between two watch-glasses it gives 

 a yellowish-red vapour, resembling that of bromine, which 

 condenses on the upper glass in the form of beautiful long 

 crystalline needles. These needles are plum or garnet- 

 coloured, they possess a somewhat metallic lustre, which is 

 however much inferior to that of sublimed indigo-blue, and 

 seem to consist simply of the original substance, which has 

 been volatilised without change. When the process of sub- 



