Kobertson. — Detection and Estimation of Alkaloids. 59 



The Composition of the Double Sulphocyanides. 



(a.) Zinc. 



Ten c.c. of the solution of the alkaloid were precipitated 

 in the usual manner with sulphocyanide in the presence of a 

 known excess of zinc-sulphate. The liquid was filtered, and 

 the zinc in the filtrate was estimated by precipitation with 

 sodium-carbonate. From this the amount of zinc which 

 combines with a known amount of alkaloid could be found 

 by difference. The following are the results : — 



(1.) Quinine - ammonium - zinc - sulphocyanide : 10 c.c. ^ 

 quinine required 00424 gram zinc. Calculated for 3 B, 2 Zn 

 (CNS),— 0-0424 gram zinc. 



(2.) Cinchonine-ammonium-zinc-sulphocyanide : 10 c.c. ^ 

 cinchonine required 0-0486 gram zinc. Calculated for 4B, 

 3 Zn (CAS) 2 — 0-0487 gram zinc. 



(3.) Cinchonine -potassium -zinc -sulphocyanide: 10 c.c. ^ 

 cinchonine required (a) 0-0472 gram zinc, (b) 0-0494 gram 

 zinc. Calculated for 4B, 3 Zn (CNS) 2 — 0-0487 gram zinc. 



(4.) Cocaine - ammonium - zinc - sulphocyanide : 20 c.c. ** 

 cocaine required (a) 0-0210 gram zinc, (b) 0-0232 gram zinc. 

 Calculated for 3 B, Zn (CNS) a — 0-0217 gram zinc. 



(b.) Ammonia. 



Precipitation was caused by a definite volume of normal 

 ammonium-sulphocyanide in the presence of excess of zinc- 

 sulphate. After washing the precipitate with a small quantity 

 of a dilute solution of zinc-sulphate, the ammonia in the 

 filtrate was estimated by distillation with caustic soda. It 

 was thus possible to determine the amount of ammonia in the 

 double salt. 



The method of operation will be illustrated by means of 

 the detailed analytical results obtained in the case of quinine. 



Preliminary Test Experiment. — 10 c.c. N ammonium-sul- 

 phocyanide on distillation with caustic soda gave ammonia 

 = 10 c.c. N acid. The filtrate from 10 c.c. ^ quinine and 

 10 c.c. N ammonium-sulphocyanide gave ammonia = (i) 9-5 

 c.c. N acid, (ii) 95 c.c. N acid. .*. Ice. N quinine combines 

 with 0-5 c.c. N ammonia. 



(c.) Sulphocyanide. 

 The method has already been described and explained. 



The following is a summary of the results obtained in the 

 determination of ammonia and sulphocyanide : — 



(1.) Quinine - ammonium - zinc - sulphocyanide : 10 c.c. ^ 

 quinine required (a) 05 c.c. N ammonia and 3-5c.c. :;: sulpho- 



* The mean of a large number of closely concordant determinations. 



