132 Mr. Nicholson on the Composition of Caffein. 



and crystallized from alcohol, and finally dried in the water- 

 bath. 



The crystals from on alcoholic solution are in the form of 

 long needles, of an orange-yellow colour and a very bitter 

 metallic taste; they are soluble in alcohol and water. When 

 boiled in water for a short time, the 'salt is decomposed, a 

 yellow flocculent matter precipitating, which is insoluble in 

 alcohol, ether and water, but soluble in hydrochloric acid. 

 If an aqueous solution is kept on the sand-bath for some 

 hours at a temperature of about 68° C. it is also decomposed, 

 and metallic gold separates in shining scales. 



It is not altered when exposed to light, and when dry may 

 be heated to 100° C. without undergoing decomposition. 



Analysis. — When burnt with chromate of lead — 



I. 0*8530 grm. of substance gave 0*5525 grm. of carbonic 

 acid and 0*1622 grm. of water. 



II. 0*3224 grm. of substance gave 0*1197 grm. of metallic 

 gold. 



III. 0*301 9 grm. of substance gave 0*1115 grm. of metallic 

 gold, which give the following per-centages : — 



I. II. III. 



Carbon . . 17*72 

 Hydrogen .2*11 

 Gold . . . 37*12 36*93 



corresponding to the formula Cjg Hjo N4O4 HCl Au CI3, as 

 may be seen by the following table, where the calculated 

 and quantities found are placed in comparison : — 



Theory. Found. 



16 eqs. Carbon . 96*00 17*98 17-72 



11 ... Hydrogen 11*00 2*06 2*11 



4 ... Nitrogen . 56*00 10*50 



4 ... Oxygen . 32*00 6*01 



4 ... Chlorine . 142*00 26*60 



1 ... Gold . . 196*66 36*85 37*02 



533*66 100*00 



The caffein compounds which I have analysed are there- 

 fore — 



Caffein Cjg Hjo N4 O4. 



Platinum compound Cjg Hiq N4 O4, HCl Pt Clg. 

 Silver compound . Cjg Hjq N4 O4, AgO, NO5. 

 Mercury compound Cjg Hjo N4 O4, 2(Hg CI). 

 Gold compound . . Cjg Hjo N4 O4 HCl, Au CI3. 



There exist several other double compounds of caffein, 

 which I have however not subjected to analysis. 



