ON VARIOUS SPECIES OF CINCHONA. Q03 



VII. 



Experiments on the various Species of Cinchona: by Mr. Vau- 



QUELIN. 



(Concluded from page 120. J 



appearances exhibited on a more minute examination by tJte infu- jj ar k s thatpre- 

 sion and decoction of different sptcies of cinchona, that prcci- cipitate nei- 

 pitate neither infusion of tan nor tartarised antimony. emetic tartar. 



X HESE sorts of bark impart to cold water a red colour, Macerated in 

 frequently a yellowish red, sometimes a brown red. Water water, 

 thus loaded with the soluble part of these barks frolhs on 

 agitation like wort. Its taste is bitter, and more or less as- 

 tringent, this differing in the different sorts. 



Left to stand in an open vessel, or in a close one if not 

 full, it soon grows mouldy, and is covered with a greenish 

 pellicle. 



Some of them are perceptibly reddened by infusion of lit- Some of them 

 mus, which announces the presence of a free acid. acid - 



Alcohol, mixed with these infusions in the proportion of two p rec jpi tate dby 

 parts to one, precipitates a grayish substance, which grows alcohol, 

 black on desiccation. The fluid is left more clear, and of a 

 purer red. This indicates the presence of mucous matter. 



In those infusions which have an acid a small quantity of By alkali. 

 caustic alkali lorms a red precipitate inclining to violet : but 

 a large quantity of the reagent redissolves this precipitate, and 

 renders the colour of the infusion more intense. 



Subjected to evaporation they become higher coloured ; E vaporate( i 

 and, attei being thus boiled down, they let tall on cooling a form a deposit 

 very bitter brown substance, which dissolves readily in alco- on co ° * 8- 

 hoi, particularly with the assistance of heat, and is precipi- 

 tated from it by water, if the solution be sutiicienrly satu- 



quantiryj the series of capacities will be in arithmetical progression, and 

 th« half sum of any two terms equidistant from the same middle (degree 

 or) term will be equal ; and the result might therefore be mistaken to 

 indicate an equality of the capacities. N. 



rated 



