EMPYREUMATIC OILS, ETC. 385 



crystallises in small rhombohedra or tablets, which melt at 82° and 

 sublime at 100'^ C. It forms a bluish-red solution in sulphuric 

 acid, and its aqueous solution is coloured deep-blue by ferric 

 chloride. Saligenin is sometimes called SnMcylic alcohol. 



Caffeic acid, or more correctly Cafdannic acid (synonymous 

 with Chlorogenic acid.)* This acid exists in raw coffee berries to 

 the amount of from 3 to 5 per cent, as a calcium and magnesium 

 salt ; according to Payen as a double salt of caffeine and potassium. 

 According to Eoehleder it is also found in Paraguay tea. It is 

 prepared by mixing an alcoholic infusion of coffee or Paraguay tea 

 with water to separate the fatty matter, then boiling the liquid, 

 adding acetate of lead, decomposing the precipitate with sulphur- 

 etted hydrogen and evaporating the filtered liquid. It forms a 

 yellowish brittle mass, which may with difficulty be obtained 

 colourless in mammelated crystalline groups. It dissolves easily 

 in water, less in alcohol ; has an astringent taste, and reddens 

 litmus strongly. It melts when heated, then chars, and gives off 

 the odour of roasted coffee. Eoehleder states that by dry distilla- 

 tion it yields water and a thick oil which solidifies on cooling, and 

 consists of " oxyphenic acid." Pfaff' states that the aroma of coffee 

 is dependent on the products of decomposition of caffeic acid. 

 There appears to be here an opening for experimental research. 

 During the process of roasting coffee no considerable escape of 

 oil vapour occurs until the berries turn brown. When they have 

 acquired a chocolate brown colour they are turned out and exposed 

 to the air so as to cool them very rapidly and prevent their 

 burning. The oil vapour is thus lost, but might be saved by 

 connectinsf the roastincp drum with an exhauster, which would 

 prevent the risk of the berries catching fire, and by attaching a 

 condenser between the exhauster and the drum, it would be 

 possible to collect and condense the vapour of the oil, which would 

 be valuable as a genuine " essence of coffee." Or, in a more 

 concentrated form, the pure caffeone abstracted from the crude 

 empyreumatic oil could be combined wuth the proportionate 

 quantity of caffeine and tannic acid, and employed either in the 

 liquid form as an essence, or combined with sugar as a syrup or a 



* Rochleder, Ann. Chera. Pharni., lix., p. 300, Ixiii., p. 193, Ixvi., p. 35 ; 

 Ixxxii., p. 196; Liel»ich, ibid., Ixxi., p. 97; Stenhouse, ibid., Ixxxiii., p. 2'4-4 ', 

 Payen, Ann. Chini. Phys. [3], xxvi., p. 108. 

 BB • 



