186 MB. E. SCHUNCK ON THE 



more fully described below. The alcoholic liquid after being 

 poured off is mixed with about twice its volume of ether, 

 when it becomes milky and deposits a substance of a syrupy 

 consistence, which contains an additional quantity of the body 

 just referred to and also some of the peculiar kind of sugar 

 which is formed by the decomposition of indican. After the 

 mixture has stood for several hours there is usually found 

 deposited on the surface of the syrup and attached to the 

 sides of the glass a quantity of white crystalline needles, 

 which also consist of a product of the decomposition of in- 

 dican. After the ethereal liquid has become clear, it is poured 

 on a filter and then evaporated as before, when it leaves a 

 clear brown syrup, consisting of indican in as high a state of 

 purity as 1 have been able to obtain it. The only impurity 

 which may still attach to the indican as thus prepared is a 

 small quantity of fatty matter, the last traces of which it is 

 extremely difficult to remove. When an alcoholic extract of 

 woad is evaporated and water is added to the residue, the 

 filtered liquid, though it may appear tolerably clear, still 

 contains a quantity of fatty matter, in a state either of solu- 

 tion or, as seems more probable, of mechanical suspension. 

 On adding acid to it, this fatty matter separates in greenish 

 masses, which melt when the liquid is heated. The greatest 

 part of this fatty matter is carried down by the oxide of 

 copper used in the process just described, and the remainder 

 is generally removed, when sulphuretted hydrogen is passed 

 through the filtered liquid, by the precipitated sulphuret of 

 copper. A little more separates occasionally in small 

 white grains during the evaporation of the liquid filtered 

 from the sulphuret of copper, especially if the temperature 

 of the current of air passing over its surface be low, as in 

 winter. If, however, the residue left after evaporation of the 

 -alcoholic extract be stirred up and agitated for some time 

 with water, so large a quantity of fatty matter becomes sus- 

 pended in the liquid as to render its separation without de- 



