58 Transactions. 



To separate the cinchonidine from the cinchonine the 

 neutral solution from the quinine-sulphate is treated with 

 excess of Eochelle salt and stirred vigorously. After an hour 

 the precipitation is complete. It is usual to weigh the pre- 

 cipitate of cinchonidine-tartiate in the same manner as the 

 quinine-sulphate. It is more rapid and convenient, however, 

 to dissolve the precipitate in a little dilute nitric acid, and to 

 titrate directly with sulphocyanide. 



The cinchonine, which is left after the removal of the 

 quinine and cinchonidine, is estimated by acidifying the solu- 

 tion and titrating in the usual manner. Care, however, must 

 be taken to have excess of nitric acid when the silver-nitrate 

 is added. 



The remaining 50 c.c. of the original solution is now 

 titrated, and in this manner the amount of total alkaloid can 

 be determined. In the red bark, owing to the small amount 

 of quinine present, 1 c.c. sulphocyanide = - 097 total alka- 

 loid ; in the yellow bark, 1 c.c. sulphocyanide = 0-095 total 

 alkaloid. 



If the method is accurate the total alkaloid (b) should be 

 equal to the sum (a) of the quinine, cinchonidine, and cincho- 

 nine. That this is the case is seen from the following deter- 

 minations made with a specimen of red bark. 



Quinine 



Cinchonidine 



Cinchonine 



Total alkaloids 



The same bark was also analysed according to the B.P. 

 method, in which the quinine and cinchonidine are pre- 

 cipitated together as tartrates and the mixture weighed on a 

 tared filter. The cinchonine was estimated by treating the 

 filtrate with ammonia, extracting with chloroform, and heat- 

 ing to dryness. 



The results are given below, and compared with those 

 obtained by the titration method. 



P.B. Method. Titration Method. 



$ uin i ne .,. I ... 4-0 3-8 4-0 



Cinchonidine i 



Cinchonine ... 1*2 1 09 



Total alkaloids 5-2 4-8 4-9 



51 50 



