20 



which, on comparison with the quinidin salt, will be found to 

 possess 1 atom additional iodine, and 1 atom more water, but a 

 deficiency of 2 atoms oxygen, the latter, apparently, in consequence 

 of the original difference in the type of the alkaloids employed ; and, 

 like that salt, it differs in its organic base by the loss of C 5 H 5 from 

 the constitution of the alkaloid originally employed, if we take the 

 formula C 40 H 24 N 2 O 2 , as given by Gerhardt, for that of cinchonine. 



The cinchonine and quinidin salts further agree in containing 

 only 1 atom sulphuric acid, whereas the quinine and cinchouidin 

 salts contain 2 atoms. 



These investigations appear to show that the alkaloids in each 

 instance undergo some modification, but not analogous to substitu- 

 tion ; it appears more like a splitting-up into different molecular 

 groups, and a rearrangement of these amongst themselves, as the 

 formulae of the organic bases differ much from those of the original 

 alkaloids. 



All these iodo-salts possess double refractive properties. 



When the acid sulphates of the mixed alkaloids, quinine, quinidin, 

 cinchonine and cinchonidin, are dissolved in dilute spirit, and the 

 temperature increased to 80 or 120, treatment with tincture of 

 iodine readily separates the quinine salt first. 



Subsequent further treatment in the same manner produces the 

 cinchonidin salt, more or less mixed with the quinine salt. 



On still further treatment, the quinidin salt is formed with its 

 well-marked characters. 



The cinchonine salt is by far the most soluble in spirit ; and 

 when a large quantity of cinchonine exists, this compound will also 

 appear along with the quinidin salt. 



This test is a beautiful and ready method of proving the presence 

 of cinchonidin in cinchonine, which would otherwise be considered 

 pure, Brandes' test having shown the absence of quinine and quini- 

 din. In the same way, this test is an easy method of detecting 

 mixtures of quinine and quinidin, the optical characters of the two 

 salts being so well marked, that no difficulties can exist in their 

 discrimination. 



It does not offer such facilities for the separation of quinine from 

 cinchonidin ; the two salts go down together, especially if large 

 quantities of cinchonidin exist with mere traces of quinine. 



