For quenching thirst during active exercise, and rendering possible prolonged exertions, tea is unsurpassed.
Coffee is the seed of the berry of the _Caffea Arabica_. Each berry contains two seeds, or beans as they are sometimes incorrectly called. The coffee is prepared by roasting the seeds until they assume a reddish-brown colour, in which process they lose 15 per cent. in weight and gain 30 per cent. in bulk. During the process of roasting, a volatile oil having a powerful aromatic smell is developed. This is not produced in such large quantities from fresh seeds; the best time for roasting varying, however, for different varieties of coffee.
The amount of =Volatile Oil= in coffee is much less than in tea. As it is elicited during the process of roasting, this should be done with nicety and care. It is effected in an iron cylinder made to revolve over a fire. After the roasting, the sooner the seeds are ground the better the coffee. When it cannot be immediately used, it should be kept in closed canisters, and not in paper or open jars.
In addition to the volatile oil, which is contained in roasted coffee in the proportion of about 1 part in 50,000, coffee contains =caffeine=, of which there is 3∕4 to 1 per cent., and an =astringent acid=, called caffeo-tannic or caffeic acid, which differs from ordinary =tannin= in that it does not blacken a solution of an iron salt.
The chief adulteration of coffee is =Chicory=, which is thought by some to improve the coffee. It is generally harmless, though in some people it produces heartburn and diarrhœa. Chicory is prepared from the root of the wild endive. It contains a volatile oil and a bitter principle, but no caffeine. It is, therefore, of no utility as a stimulant. Its presence can be detected by shaking a little of the suspected coffee on to the surface of the water in a wine-glassful of cold water. Coffee swims on the surface, and gives little or no colouration to the water; while chicory sinks, and gives a deep red tint. The aqueous extract of pure coffee (extracted by boiling water) is, when evaporated, 25 to 30 per cent. of the weight of the original decoction of coffee; while that of chicory is 65 to 70 per cent.; and on this basis, as well as on the fact that a filtered decoction of 10 grammes of coffee in 100 c.c. of distilled water, cooled to 60° F. has a specific gravity of 1009, while that of a similar solution of chicory would be 1021, the proportion of chicory in a mixture of coffee and chicory can be calculated. The microscopical appearances of the two powders differ, coffee showing hexagonal cells and no laticiferous vessels, unlike chicory. There is no law against selling mixed coffee and chicory, if the fact that it is a mixture is stated; and the proportion of the two unfortunately is not required to be stated. As a pound of coffee costs five times as much as a pound of chicory, it is obviously to the purchaser’s advantage to make his own mixture in the proportions desired.