and of some of its Compounds. 121 



ble salt of platinurrij for in this instance the cafFein is in direct 

 combination with the chloride of mercury, and is exactly 

 analogous to the corresponding compounds of leucoline and 

 aniline investigated by Dr. Hofmann*. The mercurial com- 

 pounds of this kind are generally easily decomposed, but the 

 compound of chloride of mercury and cafFein is so stable, that 

 it may be boiled in water for a considerable time without un- 

 dergoing the slightest change in its properties. It may be 

 dried at 100° C. and loses no M'eight at that temperature. 



I endeavoured to combine the determination of the carbon, 

 hydrogen and mercury of this substance in one combustion, 

 and have perfectly succeeded. The operation was conducted 

 as follows : — The substance was mixed with chromate of lead 

 and introduced into a combustion-tube of at least 26 inches in 

 length. About 6 inches of copper turnings are placed above 

 the mixture, leaving a space of 8 inches from the copper to 

 the anterior end of the tube. A receptacle for the mercury 

 is formed out of the tube itself by contracting it about an 

 inch from the copper turnings, and again so as to leave an 

 elongated bulb of an inch in length. At the close of the ope- 

 ration the tube is cut with a file at the posterior contraction. 

 In order to separate the water from the mercury, the chloride 

 of calcium tube (which has not been detached) is connected 

 with an aspirator and air admitted through chloride of cal- 

 cium, the bulb being kept at a temperature of 100'^ C. 



I obtained in my analysis the following numbers : — 0'7833 

 grm. of substance gave 0*5832 grm. of carbonic acid, 0*1639 

 grm. of water, and 0*3365 grm. of mercury, corresponding to 

 the following per-centage, which I place in comparison with 

 the theoretical numbers : — 



Theoiy. Expt. 



16 eqs. Carbon 96 20*68 20*30 



10 ... Hydrogen 10 2*15 2*32 



4 ... Nitrogen 56 12*11 



4 ... Oxygen 32 6*89 



2 ... Chlorine 70 15*08 



2 ... Mercury 200 43*09 42*91 



464 100*00 



Caffein and Terchloride of Gold. 



This compound is formed when a solution of terchloride of 

 gold is added in excess to cafFein dissolved in dilute hydro- 

 chloric acid. If concentrated solutions are employed, the 

 whole immediately solidifies into a mass of a most splendid 

 lemon-yellow colour; this is to be washed with cold water 



♦ Liebig's Annalen, xlvii. 37. 



