92 ANIMAL BASES. 



Digest it in absolute alcohol, a portion is dissolved. This por- 

 tion is fuscin. When the alcohol is evaporated, we obtain the 

 fuscin in a brown coloured mass, cracked in all its dimensions. 



Fuscin is solid, has a brown colour, and is insoluble in water. 

 The acids dissolve it, and when the solutions are evaporated a 

 brown matter remains, which is soluble in water and in aqueous 

 alcohol ; and which, while in a solid state, may be exposed to 

 the atmosphere without undergoing any alterations. The com- 

 pounds of fuscin with succinic and benzoic acids constitute an ex- 

 ception to this solubility in water ; for they are insoluble in that 

 liquid. When any of the solution of salts of fuscin is mixed with 

 potash, fuscin precipitates, which, when washed and dried, has 

 the form of a brown powder. It does not melt when heated, but 

 is charred, and gives out a smell similar to that of burning horn. 



Fuscin, whether in the state of a dry powder, or in solution, 

 in acids gradually absorbs oxygen from the atmosphere, and as- 

 sumes a red colour. The solutions in that case contain the same 

 substance which alcohol leaves undissolved when digested on 

 the brown matter precipitated by alkalies from the acetic acid 

 solutions mentioned in the process for procuring fuscin. This 

 substance, as well as fuscin, combines with the acids. But it soon 

 loses this property, and assumes the form of a brown powder, 

 insoluble in all menstrua. * 



CHAPTER VII. 



OF CRYSTALLIN. t 



THIS substance was obtained by Unverdorben from indigo ; 

 but its analogy to the five preceding bases is so strong, that it was 

 deemed better to place it here than among the products of vege- 

 table substances. 



When indigo is distilled per se it gives first water and oil, 

 and then oil holding resin in solution passes over. The oil 

 is colourless and volatile, and has not an empyreumatic smell, 

 but one similar to that of indigo when strongly heated. This 

 oil, when left exposed to the air, becomes yellow, and then con- 



* Unverdorben, Poggendorfs Annalen, viii. 261. 



t So called because its salts are capable of crystallizing, which is not the case 

 with those of any of the preceding five bases. 



