84 CAFFEIN-VIELDING PLANTS. 



The coffee plant contains in all parts a special tannin, 

 called coffee tannic acid (3-5 per cent, in the unroasted beans). 

 It is sharply distinguished from all other tannins by not coagu- 

 lating the gelatine and not precipitating tartar emetic, even on 

 addition of sal ammoniac. It stains ferric salts grass-green. 



The most prominent reaction of infusions from all parts of 

 the coffee plant not yet mentioned in the books is the golden 

 yellow colouration, with alkalies and cyanide of potassium. 

 Adulterated coffee can easily be found out on application of this 

 test, as only brown tints are found with chicory and other 

 substances. Acetate of copper is greenish with coffee tannic 

 acid, and yellow on addition of ammonium carbonate. Lime 

 water makes a greenish, lead acetate a greenish -yellow, ammo- 

 nium molybdate in nitric acid a reddish-yellow precipitate. 

 Ferro-cyanide of potassium in ammonia gives a greenish -brown 

 reaction. 



By the roasting process a part of this coffee tannic acid is 

 changed into cafleol, and if the roasting is too strong, into 

 catechol and phenol (carbolic acid), both of which I detected in 

 the smoke of the roasting beans and in the fried beans them- 

 selves. The cafleol is an oily liquid to which the agreeable 

 smell of the roasted coffee is due. It is said to be antagonistic 

 in its action to the caffein, which explains the difference of the 

 physiological effects of tea and coffee. The leaves of the coffee 

 plant contain 63 per cent, of water. The dry leaves contain at 

 least as much caffein as the dry beans. An analysis of the fresh 

 leaves gave — water 63, coffee tannic acid 2*0, caffein 0*6, extract 

 10*0, insoluble matter 24-4. The leaves of the coffee tree have 

 been roasted and used like coffee beans during the last twenty 

 years with satisfactory results. 



The Queensland coffee is at least equal to the Brazilian 

 product sold in Europe, if not superior to it. In open bush land, 

 with a deep soil, cultivation of the coffee tree would not be a 

 failure, as the native trees would supply the shade so necessary 

 for the young plajits. 



The Tea, Camellia thea, still grows wild in Assam. It wants 

 a hot and damp^ and therefore an unhealthy climate, as Mr. 

 Bemays points out, and our dry country is not very suitable for 

 tea-growing. Nevertheless there are good shrubs to be found in 



