228 



EXPERIMENTS AND ©BS EK. VATION S ON CINCHONA. 



Experiment VIII, 

 Carbonate of A folutlon of Carbonate of pota(h produced a copious 



Ss^fokS" ^^''^ ^^^y precipitate in the folution of gelatine, which was 

 of gelatine, foluble in boiling water, but was not precipitated from the fo- 

 lution hy infulion of galls, until fome acid was added. 



but not infu- 

 Ifon of cin- 

 chona. 



DiflFerence be- 

 tween gelatin 

 and cinchonin. 



Gelatin forms a 

 jelly with water. 



and is preci- 

 pitated from it 

 by alcohol, car- 

 bonate of pot- 

 aih, and tannin. 



Cinchonin does 

 nor form jelly 

 with water, is 

 not precipi- 

 tated by carbo- 

 nate of potafli, 

 is foluble in al- 

 sohol, and com- 

 bines with 

 ftinnin. 



Experiment IX. 



The folution of carbonate of potaQi changed the colour of 

 the infufion of cinchona to a fine red, without difturbing its 

 tranfparency. 



Thefe fads feem to nie fufticient to prove the difference be- 

 tween gelatine, and the new principle in cinchona, which for 

 the fake of convenience, I fhall venture for the prefent to de- 

 nominate cinchonin. 



Gelatine is foluble in water, and the folution is difpofed to 

 gelatinize. Sixgrainsof ifinglafsjdinblved in one ounceof water, 

 form with it at temperatures below 60** Fahrenheit, a jelly of 

 confiderable firmnefs. From its folution in water, gelatine ii 

 precipitated by alcohol, and a folution of carbonate of potaflu 

 It is precipitated alfo by tannin, and the precipitates form a 

 hard brown tranfparent mafs, 



Cinchonin is foluble in water, but gives it no tendency 

 to gelatinize. From its folution in water, it is not preci- 

 pitated by a folution of carbonate of potafli. It is foluble in 

 alcohol ; it combines with tannin. The componnd is foluble 

 in alcohol, but forms, when water is added, or ufed as a men- 

 flruum, a friable opaque yellowifh precipitate ; but cinchonin 

 does not feparate even from a watery folution of tannin, all 

 that is precipitable by a folution of gelatine. 



ANDREW DUNCAN, Jun. 



Edinburgh, 30ih Oa. 1S03. 



11. Letter 



