THE ALUMNI JOURNAL 111 



The present test for heavy metals (in alkaline solution) is objec- 

 tionable, owing to the fact that a yellowish coloration always re- 

 sults upon the addition of H.S solution to the alkaline solution of 

 the pure salt. It is also exceedingly difficult to obtain a sample of 

 caustic soda which itself does not react for heavv metals. How- 

 ever, owing to the small dosage, the presence of heavy metals 

 would not necessarily interfere with its medicinal use. 



. Merck's Report. 



THE ESTIMATION OF QUININE IN CINCHONA BARK.* 



By N. H. Cohen. 



My attention has been directed by Dr. M. Greshoff to the inter- 

 esting communication by Mr. W. Duncan in The Pharmaceutical 

 Journal of March 27. page 429, on the estimation of quinine in 

 cinchona bark. The process described consists in precipitating the 

 quinine as sulphate from a neutral sodium sulphate solution. In 

 the discussion of the method in this journal, it has already been 

 stated by Mr. Hill that "it is remarkable that quinine alone should 

 be precipitated." Surely other alkaloids are precipitated as well. 

 Some time ago I studied in this laboratory Florence's new method 

 of estimating the total alkaloid and the quinine in cinchona bark 

 (vide Pharmaceutisch Weekblad, 1908, 1089), and pointed out that 

 his estimation of the total alkaloid gives reliable results, but that 

 this is not so in the case of the quinine estimation, because, when 

 the quinine oxalate is precipitated, the other alkaloids are partly 

 carried down with it. so that the result largely depends on the 

 nature and amount of the alkaloids, other than quinine, which are 

 present. The same difficulty arises in the case of Mr. Duncan's 

 method ; were this not so, it would certainly be a very elegant and 

 practical one. as a simple method for the estimation of quinine in 

 cinchona bark is still much wanted. But just as in the case of all 

 the other methods of cinchona bark assay, depending on the pre- 

 cipitation of the quinine in the form of a salt, and thus giving 

 quinine salts which are always more or less contaminated with 

 other alkaloids, it also seemed highly probable in the case of Dun- 

 can's new method that it could not give pure quinine sulphate. 



*Phartn. Journ. 



