£10 0N VARIOUS SPECIES OP CINCHONA. 



it is evaporated to n certain point, left to grow cool that it 

 may deposit a sediment, this resiniform sediment is separated 

 from the liquor, and the evaporation and refrigeration are re- 

 peated, till the liquor no longer becomes turbid, and has only 

 a pale yellow colour. It is then dried on plates by the heat 

 of a stove. By operating thus a very small quantity of re- 

 siniform matter only remains in the water, with a gum, and a 

 salt with a calcareous basis, the efficacy of which in the cure 

 of fever is very questionable. 



Co?vparativc examination of the resin of these cinchonas iciih 

 other known vegetable substances. 



j g the matter I s tqere in the vegetable kingdom any immediate principle, 

 soluble in alco- with which this can be classed? Is it to be placed among 

 the resins, as has hitherto been done? It is true that chemists 

 and apothecaries formerly arranged together so many sub- 

 stances under this genus, that, if we looked to some of its 

 properties only, we might also rank this among them: but if 

 we apply the name of resin only to those substances, which 

 are absolutely entitled to it, those of cinchona and many 

 other vegetables must be separated from the resins properly so 

 called. 

 ^ . If the resiniform matter of these cinchonas resemble resins 



by its solubility in alcohol, it differs from them by its solubi- 

 lity in water, acids, and alkalis, and particularly by its pro- 

 perty of precipitating metallic salts, and fixing in cloth. I 

 but a peculiar believe then it maybe considered as a peculiar vegetable 

 principle. principle, the properties of which have not hitherto been well 



understood by chemists. This principle is not the same in 

 every species of cinchona : it differs in those that precipitate 

 infusion of tan and tartarised antimony, and in those that pre- 

 cipitate isinglass only. 

 Perhaos simi- It is probably a principle extremely analogus to it, that 



lar to v.hat most commonly imparts a bitter taste to vegetables . 



gives bitter- . 



ness. 



Recapitulation of the properties of cinchonas. 



General pro- 1. The different species of bark may be divided into three 



hTk* 3 ° [ classes with respect to their chemical properties. 



In 



