118 Mr. Nicholson on the Composition of Caffein, 



which agrees with Professor Liebig's formula, as is seen by 

 the following : — 



Mean of 

 experiments. 

 49-42 

 5-28 



Caffein and Bichloride of Platinum, 



On precipitating a solution of cafFein in hydrochloric acid 

 with bichloride of platinum, as Dr. Stenhouse has shown, a 

 precipitate of an orange-yellow colour is obtained. If the two 

 solutions are mixed hot, the fluid on cooling deposits the com- 

 pound in beautiful granular crystalline tufts, which, when 

 thrown on a filter and washed with alcohol, are perfectly pure. 

 This double salt is only sparingly soluble in alcohol, aether, 

 and water. It does not alter when exposed to light, nor does 

 it lose in weight when kept at 100° C. for a considerable time. 



The analyses of salts, all prepared at different periods and 

 dried at 100° C, gave the following results: — 



I. 0'5382 grm. of substance, burnt with chromate of lead, 

 gave 0-4765 grm. of carbonic acid, and 0-1387 grm. of water. 



II. 0*4881 grm. of substance gave 0*1196 grm. of platinum. 



III. 0-4779 grm. of substance gave 0-1172 grm. of pla- 

 tinum. 



IV. 0*6022 grm. of substance gave 0-1482 grm. of pla- 

 tinum. 



V. 0*5781 grm. of substance gave 0-1425 grm. of pla- 

 tinum. 



VI. 0-5246 grm. of substance gave 0*1293 grm. of pla- 

 tinum. 



VII. 0-3847 grm. of substance made of caffein of my own 

 preparation, gave 0-0945 grm. of platinum. 



Which give the following per-centages : — 



I. II. III. IV. V. VI. VII. 



Carbon . 23-80 

 Hydrogen 2-86 

 Platinum ... 24-51 24-52 24-60 24*64 24-64 24-56 



leading exactly to the formula given by Dr. Stenhouse, viz. 



Ci6H,oN4 04HCl,PtCl2, 



as is seen when placed in comparison with the calculated 

 numbers. 



