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, retains 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 proportion 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.[2] 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 [Illustration: Plate 10. Fragment of Roasted Chicory.] [Illustration: A Fragment of Roasted Coffee, being magnified 140 diameters.] the coffee be pure, it for the most part floats, becomes very slowly moistened, even when shaken up with the water, and communicates scarcely any colour to the liquid; very gradually it imbibes water; the liquid acquires a very pale sherry tint; and at the end of several hours the greater part of the powder is found to have fallen to the bottom of the glass. If, however, it be chicorised, the presence of chicory (genuine or spurious) will be readily detected, by a portion of the suspected powder rapidly sinking and communicating to the liquid a reddish-brown tint, which will be more or less deep according to the amount of chicory present.