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XXIII. Experijnents Tipnn the various Species of Cinchona. 

 By M. Vauguelin. 



[Concluded from p. 53.] 



FhcBUomena presented on a close)- Analysis of the JMacera- 

 tion and Decoction of some Kinds of Cinchona, which 

 precipitate neither the Infusion of Tan nor Emetic. 



X HESE kinds of cinchona communicate to cold water a red 

 colour, often of a yellowish, and sometimes of a biiownish 

 cast. The water thus saturated with the soluble part of these 

 cinchonas becomes frothy upon agitation, like beer yeast ; 

 it has then a bitter taste, with more or less astringency, ao- 

 cording to the kind. 



Left to subside in a close or open vessel, provided it is,iiot 

 full, this cinchona water becomes speedily mouldy, and is 

 covered with a greenish pellicle. 



Some of them redden very sensibly turnsole tincture j 

 which indicates the presence of a free acid. 



Alcohol mixed with these infusions of cinchona, in the 

 proportion of two parts to one, prtcipitaies from it a grayish 

 matter, which becomes black upon drying; the liquor is 

 then clearer, and of a purer red : this phcenomenon an- 

 nounces the presence of a mucous matter. 



A small quantity of caustic alkali forms, in such of these 

 waters as are acid, a red precipitate inclining to violet; but 

 a greater quantity of this rc-agent redissolves the matter, 

 and gives the liquor more iiitensencss of colour. 



Submitted to eva])oration they become deeper in colour, 

 and deposit upon cooling, after having been concentrated, 

 a very bitter brown substance, which is easily dissolved in 

 alcohol, particularly with the assistance of heat, and which 

 water precipitates from it, if the sjjution is sufficiently con- 

 centrated. Water itself redissolves this matter, although it 

 abandons it on evaporation : but it requires a far greatcT 

 quantity than when it is accompanied with ,the other prin- 

 ciples of cinchonas : this seems to prove that these same 

 principles favour the solution in water. 



I3 If 



