100 



The brown colouring , matter of roasted coffee, on the other 

 hand, acquires, from the same reagent, a green colour, and 

 a brownish-green flocculent precipitate is formed. These 

 two different reactions may be applied, not only for distin- 

 guishing the pure infusion of coffee and of chicory, but also 

 those which contain a mixture of the soluble principles of 

 the two alimentary substances. 



Infusion of pure coffee acquires a green colour, more or 

 less intense, on the addition of some drops of persulphate of 

 iron. 



Infusion of pure chicory, under similar circumstances, re- 

 tains its brownish-yellow colour, which becomes more intense, 

 and acquires a slight greenish tint. 



A mixture of the two infusions, containing one-half, a 

 fourth, or a fifth of its volume of infusion of chicory, may be 

 recognised by its brownish-yellow colour, which remains 

 after the deposition of the precipitate produced by the salt 

 of iron, together with part of the colouring matter of the 

 coffee. This separation may be expedited by rendering the 

 coloured liquor slightly alkaline by the addition of a small 

 quantity of weak solution of ammonia, and allowing it to 

 stand in tubes closed at one end. The supernatant liquor, 

 after the precipitate has deposited, will possess a brownish - 

 yellow tint by refracted light, which will be deeper in pro- 

 portion to the quantity of chicory present. 



If the experiment be first made with infusion of pure 

 coffee of a certain strength, and afterwards with additions of 

 known quantities of chicory, keeping these for comparison, 

 the quantity of chicory in a mixed sample may be thus 

 determined.* 



A simple means of detecting the chicory in ground coffee 

 is as follows : 



Throw about a tea-spoonful of the suspected coffee in a 

 wine-glass of water, and stir the mixture with a spoon. If 



* M. Lassaigne, in " Journal de Chimie Medicale." 



