APPENDIX. 127 



variations in the animals employed in the experiments.^ The circum- 

 stance that theine was found to be more active than caffeine, and to be 

 capable of producing effects not produced by caffeine, tends to support 

 the view that the theine was impure. It is now well known that tea 

 contains other bases than caffeine, the presence of traces of which 

 might be sufficient io account for the observed differences. 



During the preparation of the pure aurochlorides for a comparison 

 of their properties the authors obtained two new and interesting 

 auric derivatives of caffeine. 



r 



^n an aqueous solution of caffeine auro chloride is heated, a 

 yellow, flocculent precipitate is gradually formed^ which is insoluble 

 in alcohol, chloroform, and ether, hut dissolves in hydrochloric acid, 

 reproducing the aurochloride. The substance dried at 100^ forms a 

 pale yellow amorphous powder, which melts at 207° (corr.). Analysis 

 proved it to be aurochlor caffeine C^H'(An01^}N*0^ a substance 

 m which one atom of hydrogen in caffeine is replaced by the group 

 (AuCP). It is pointed out that the ready formation of this remarkable 

 compound from caffeine aurochloride by the loss of two molecular pro- 

 portions of hydrochloric acid-C^Hl^jN^^O^ HCI, AuCP=:2 HCI-[- 

 C'H^ (AuCP) N*0^-is better sho%\Ti by Medicus's formula for 

 caffeincj than by that proposed by Emil Fischer, since in Medicus^s 



Wh 



group 



con- 



tiguous to the doubly -linked nitrogen atom, to which the auric- 

 chloride is attached, 



-By the reaction of an alcoholic solntion of potassium chloraurate 

 (KCl, AuCPj with a solution of caffeine in chlorofoiTU, a salt, 

 crystallizing in the dark red needles, was obtained. This is shown to 

 be caffeine potassium aurochloride (C-'H'*N*0^ KCl, AuCP) which 

 differs from caffeine aurochloride in containing potassium in the 

 place of the hydrogen of hydrochloric acid. This salt melts at 208'' 

 (corr.). It readily dissolves in alcohol and water, forming yellow 

 solutions which appear not to contain the salt itself, but its 

 constituents, caffeine and potassium chloraurate. The salt is 

 nearly insoluble in ether and chloroform, but prolonged contact with 

 these liquids leads to its decomposition into caffeine and potassium 

 choloraurate {W. R. Dunsian and W.F.J. ShcpJieard, from the 



Research Lahoratory of the Pharmaceutical Society — 7'he stih&tance 

 ^f ^ commit nicatio7i made to the Chemiccil Society ^ December Ibth^ 



1892.) 



