22 Dr. Stenhouse on the dried Coffee-leaf of Sumatra 



reumatic odour. In this respect they pretty closely resemble 

 Paraguay tea, the leaves and twigs of the Ilex paraguayensis, 

 which is subjected to a somewhat similar process. The coffee- 

 leaves when digested with boiling water yielded a deep brown 

 infusion, which in taste and odour closely resembled an infusion 

 of a mixture of coffee and tea. On the addition of milk and 

 sugar, it formed a very tolerable beverage ; and as the roasted 

 coffee-leaf can be imported into Europe for rather less than two- 

 pence per pound, the poorer classes of society are likely to find 

 it a very useful substitute for tea and coffee. Should a more 

 moderate temperatiu-e be employed in drying the coffee-leaf, I 

 think its flavour would be greatly improved. 



The coffee-leaf, as might almost have been expected, contains 

 the two characteristic constituents of the coffee-bean, viz. theine 

 or caffeine, and caffeic acid. In this respect the coffee-leaf dif- 

 fers essentially from chicory or any of its adulterations, such as 

 roasted turnips, mangelwurzel, carrots, &c,, the usual substitutes 

 for coffee, which do not contain a trace of either of these prin- 

 ciples. 



The theine or caffeine was extracted from the coffee-leaves in 

 the usual way, by precipitating the colouring matter and other 

 impurities, first by acetate and then by subacetate of lead. The 

 acetate of lead threw down a dark brown precipitate -containing 

 all the caffeic acid, and the subacetate produced a scanty bright 

 yellow precipitate. The excess of lead was then removed from 

 the clear solution by sulphuretted hydrogen, and the sulphide of 

 lead having been collected by filtration, the theine crystallized 

 when the liquid, after being sufficiently concentrated, had been 

 set aside in a cool place for some days. 



The crystals of theine as first obtained were of a brownish 

 colour, but after being strongly pressed between folds of blotting- 

 paper and repeatedly crystallized, they were rendered nearly 

 colourless. 



I. 1000 grains of dried coffee-leaves, when treated in the way 

 just described, yielded 12*5 grains theine =1-25 per cent. 



II. 1000 grains of coffee-leaves in a subsequent trial gave 

 11'54 grains =1'15 per cent. 



The amount of nitrogen in the dried coffee-leaves was also 

 determined by Will's method. 



1-344. grm. substance gave 0-.2005 platinum =2-118 percent, 

 nitrogen. 



0*7775 grm. gave 0-1185 platinum =2-165 per cent. 



Now it has been ascertained as the result of numerous experi- 

 ments*, that " coffee contains from 0*80 to 1 per cent, of theine, 



* See the 32nd page of " The Chemical Report on the mode of detect- 

 ing Vegetable Substances mixed with Coffee for the purposes of adultera- 



