24 Dr. Steuhouse on the dried Coffee-leaf of Sumatra 



logons to kinic acid^ the acid of cinchona barks, for it yields 

 kinone when oxidated by means of sulphuric acid and binoxide 

 of manganese. To observe this property, the coffee is boiled 

 with water and a little slaked lime, the infusion filtered and 

 evaporated down to the consistence of a syrup. The syrupy 

 liquid is then mixed in a retort with four times its weight of 

 binoxide of manganese and one part of oil of vitriol diluted with 

 an equal bulk of water. Sufficient heat is produced by the 

 action of the sulphuric acid upon the other materials to bring 

 over the greater portion of the kinone, and the lamp need not 

 be applied till towards the close of the operation. The distillate 

 consists of yellow crystals of kinone, which usually coat the neck 

 and sides of the retort, and a bright yellow liquid which is a 

 saturated aqueous solution of kinone with a considerable quan- 

 tity of formic acid. Kinone is easily discernible by its volatility 

 and peculiarly acrid odour, which greatly resembles that of chlo- 

 rine. The solution of kinone gives with ammonia a sepia black 

 colour. It is decolorized by sulphurous acid. The beautiful 

 green hydrokinone is obtained by exactly neutralizing the solu- 

 tion of the yellow kinone with sulphurous acid, great care being 

 taken not to introduce the latter in excess. 



" The peculiar acid in Paraguay tea agrees with caffeic acid, 

 to which it is no doubt related, in yielding kinone to similar 

 oxidizing agencies ; so does the acid of the leaves of the common 

 holly. Ilex aquifolium, and the whole of the Cinchona tribe." 



When coffee-leaves are boiled with a considerable quantity of 

 water and a slight excess of milk of lime, the dark brown strongly 

 alkaline liquor is cautiously evaporated to dryness, and then 

 treated in the way already described with three times its weight 

 of black oxide of manganese and one part of sulphuric acid 

 diluted with its own bulk of water, a much larger quantity of 

 crystals of kinone are obtained than can be procured from an 

 equal weight of the coffee-bean. This clearly shows that the 

 leaves are i-icher in caffeic acid than the beans. 



Kinone may, I find, be obtained in small quantity by a similar 

 pi'ocess from a great number of our commonest plants. Thus I 

 also obtained indications of kinone from the leaves and branches 

 of the privet, Lifjustrum vulgare ; from the common ivy, Hedera 

 helix ; from the Quercus Ilex, the evei-green oak of our gardens 

 and shrubberies, a native of Turkey ; from the Quercus robur, 

 the common British oak ; from the Ulmus campeslris, the com- 

 mon small-leaved elm; from the ash, Fraxi7ius excelsior ; and 

 from the bush-tea of the Cape of Good Hope, the Cyclopia lati- 

 folia of DeCandoUe, a plant of the natural order Leguminosa;. 



From numerous plants which I tried I could not obtain a 

 trace of kinone. This was the case among others with laburnum, 



