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



the French manufactories, and probably also in the English, 

 the same quantity of these bases has never been extracted with 

 any regularity from equal weights of cinchona even of similar 

 quality : this irregularity will, I think, admit of easy explana- 

 tion from the fact which I have ascertained, that quiha is very 

 soluble in lime water and in the solution of chloride of calcium; 

 hence, when lime is employed to precipitate those bases from 

 their solution in the hydrochloric acid, which is used to extract 

 them from cinchona bark, a part of the quina is re-dissolved, 

 especially should the lime be added in excess even in the 

 smallest quantity. It is true that the re-solution of the quina 

 depends in great measure on an excess of lime being added ; 

 but at the same time it must be admitted, that even should 

 the greatest care be taken by the manufacturer to guard against 

 adding an excess of lime, it would be impossible wholly to 

 prevent the solution of some of the quina, as chloride of cal- 

 cium will inevitably be formed, and consequently a part of the 

 quina will be dissolved in it. 



Considering that such must be the unavoidable result of the 

 process usually followed, and reflecting on the serious, if not 

 insurmountable obstacle which the re-solution offers to the 

 economical manufacture of those important articles, I was led 

 to inquire by experiments whether some other and less objec- 

 tionable means could be discovered of precipitating those sub- 

 stances. 



I first experimented with solutions of caustic ammonia and 

 potash, and soon found that the use of these alkalies was lia- 

 ble to the same objection as that of the chloride of calcium 

 and hydrate of lime, viz. of dissolving a portion of the qui- 

 na when added in excess. But the result was found to be 

 very different when a solution of caustic soda was employed, 

 as this alkali, even when added in excess, dissolves neither 

 quina nor cinchonia. Of this insolubility I satisfied myself 

 by the following experiment. 



I precipitated a mixed solution of the sulphates of quina 

 and cinchonia by caustic soda, and afterwards filtered it; 

 the filtered liquor was next divided in two equal parts, one 

 of these treated for the purpose of ascertaining whether any 

 quina had been re-dissolved by the soda ; with this object 

 in view, I saturated the excess of alkali with hydrochloric 

 acid, and then poured chlorine into the neutral solution and 

 afterwards ammonia. It is well known that if there had been 

 a trace of quina or any one of its salts in the solution, a 

 green colour would have been produced*; but in my experi- 

 ment not the slightest colour was observed. 



* Vide Journal Hcbdomadairc dc Pharmacic (vol. xxii. p. 37). Published 

 by M. Adrien of L}ons. 



