174 M. Calvert on the Preparation of Quina and Cinchonia. 



sulphate of quina, and the other with very pure sulphate of 

 cinchonia; I found that 10 grammes of water contained 0'033 

 of sulphate of quina, and that the same quantity of water 

 contained 0'165of the sulphate of cinchonia, or five times the 

 proportion of sulphate of quina ; therefore, in order to act on 

 the same quantities of each salt dissolved in the same quantity 

 of water, I took 10 grammes of the solution of sulphate of 

 quina, or 0*033, and only 2 grammes of the saturated solu- 

 tion of sulphate of cinchonia, and to this latter solution I 

 added 8 grammes of water, and thus in both cases I acted on 

 0*033 of solid salt in 10 grammes of water. 



1st. The solution of the sulphate of quina gave a preci- 

 pitate with chloride of lime, which was immediately re-dis- 

 solved by the addition of an excess of the reagent. 



The solution of the sulphate of cinchonia, on the contrary, 

 gave a precipitate which was not re-dissolved on the addition 

 of even a large excess of the reagent. 



I afterwards mixed the solutions of the sulphates of quina 

 and cinchonia in equal quantities, and poured into the mix- 

 ture chloride of lime; a precipitate was formed, of which one 

 half was re-dissolved on the reagent being added in excess ; 

 the precipitate which was re-dissolved was quina: hence it 

 appears, that sulphate of quina, mixed with an equal quantity 

 of sulphate of cinchonia, could be separated from it, and the 

 quantity of cinchonia ascertained^ 



I next experimented on a mixture containing two parts of 

 sulphate of quina and one of sulphate of cinchonia, and a 

 similar result was obtained; that is, a precipitate was produced 

 on the addition of chloride of lime, a portion of which, equal to 

 the proportion of sulphate of quina, was again re-dissolved 

 on the reagent being added in excess. 



When the small quantity of sulphate of cinchonia upon 

 which I experimented is considered, it will be perceived how 

 easily, by means of these reagents, any adulteration of the 

 sulphate of quina by sulphate of cinchonia may be de- 

 tected, and the smallest quantity of the substance discovered, 

 as quina has no influence on the result of the experiment, 

 provided the liquor is sufficiently diluted to guard against the 

 precipitation of sulphate of lime. 



In applying the tests the greatest care was taken to pre- 

 vent the precipitation of the sulphate of lime ; and the best 

 proof that can be adduced of this source of error having been 

 avoided was, that if the precipitate had been sulphate of lime, 

 it would not have disappeared in the experiment made with 

 the pure solution of sulphate of quina, and remained in that 

 of the sulphate of cinchonia. 



