Coffea Arabica. Coffee.
Nat Ord. — Cinchonaceae. Sex. Syst. — Pentandria Monogynia.
Description. — Coffee tree is an evergreen shrub, growing from twenty to thirty feet in night, with an erect stem, covered with a brownish bark. The branches are opposite, the lower spreading, the upper somewhat declining, and gradually diminishing in length as they ascend, so as to form a pyramidal summit, which is covered with a green foliage throughout the year. The leaves are opposite, ovate-lanceolate, entire, acuminate, smooth and shining, bright-green above and paler below, four or five inches long, on short petioles, and accompanied with a pair of small, undivided, subulate stipules. The flowers are white, having an odor similar to jasmine, sessile, and are in clusters of four or five together, in the axils of the upper leaves ; peduncles short. The calyx is very small, superior, five-toothed. The corolla is funnel-shaped, with a flat border divided into five spreading, lanceolate, pointed segments. The stamens are inserted into the tube of the corolla, and have yellow, linear anthers. The ovary is inferior, ovate, and supports a simple style, with two awl-shaped, reflexed stigmas. The fruit or berry is globular, about the size of a cherry, umbilicated at the summit, deep-purple, two-celled, two-seeded, and containing a yellowish pulpy matter. The seeds are hemispherical, convex on one side, and flat on the other with a longitudinal furrow, of a pale glaucous color, and invested in a thin, elastic, somewhat translucent arillus ; they constitute the coffee of commerce.
History. — Coffee is a native of Southern Arabia and Africa, and is cultivated in various parts of the world, between the latitudes of 55° north and south. The tree is raised from the seeds, which are sown in proper soil, and germinate in less than a month, producing plants which are sufficiently large for transplanting at the end of the year. They are then placed in rows, and begin to bear fruit in three or four years. The seeds are known to be ripe when the berries assume a dark-red color, and if not gathered will drop spontaneously. When gathered, they are dried, and their papyraceous envelope removed.
There are many varieties of coffee in commerce, the characters of which depend upon the soil, the climate, and the mode of culture. The Mocha Coffee is esteemed the best, and the Java next ; but the principal supply in this country is from the West Indies and South America. Good coffee should be hard, and so heavy as to readily sink in water; age improves its flavor ; soft, light, black or dark-colored, or musty grains are of inferior quality.
Coffee has a faint, peculiar odor, and a slightly-sweetish, somewhat austere taste. It contains cellulose, hygroscopic water, fatty matter, glucose, dextrine and a vegetable acid, legumin, chlorogenate of potassa and caffein, free caffein, concrete volatile oil, fluid volatile oil, and mineral substances. Caffein may be obtained in the following manner: Exhaust bruised coffee by two successive portions of boiling water, unite the infusions, add acetate of lead in order to precipitate the principles which accompany the caffein, filter, decompose the excess of acetate of lead in the filtered liquor by sulphureted hydrogen, and evaporate to the point of crystallization. Concentrate by evaporation, and neutralize with ammonia. The crystals which form upon cooling, may be redissolved in water, treated with animal charcoal, and the solution be again evaporated.
H. J. Versman states the following to be the most profitable and simple mode of obtaining caffein : " Ten parts of bruised coffee are mixed with two parts of caustic lime, previously converted into hydrate of lime. This mixture is placed in a displacement apparatus, with alcohol of 80°, until the fluid which passes through no longer furnishes evidence of the presence of caffein. The coffee is then roughly ground, and brought nearly to the state of a powder, and the refuse of the already once digested mixture from the displacement apparatus dried, and ground again, and, mixed with hydrate of lime, is once more macerated. The grinding is more easily effected after the coffee has been subjected to the operation of the alcohol, having lost its horny quality, and the caffein is thus certainly extracted. The clear alcoholic fluid thus obtained is then to be distilled, and the refuse in the retort to be washed with warm water to separate the oil. The resulting fluid is then evaporated until it forms a crystalline mass, which is to be placed on a thick Biter, and the moisture expressed. The moisture, after evaporation, still furnishes some caffein. The impure caffein is freed from oil by pressure between folds of blotting-paper, and purified by solution in water with animal charcoal, and then crystallized by evaporation. Good Brazilian coffee, thus yields 0.57 per cent, of caffein.
Caffein crystallizes by the cooling of its concentrated solution, in white, opake, silky, flexible needles ; by slow and spontaneous evaporation, in long, transparent prisms. It has a feebly bitter and disagreeable taste, is soluble in water, alcohol, and ether, melts when exposed to heat, and at a higher temperature sublimes, without residue, into needles analogous to those formed by benzoic acid. It is precipitated from its aqueous solution by no reagent except tannic acid, and is remarkable for containing a larger proportion of nitrogen than any other proximate vegetable principle ; and in this respect equals some of the most highly animalized products. It is a feeble base, but forms very large crystalline salts with sulphuric and muriatic acids. Its composition is considered to be C8 N2 H5 O2, and it is believed to be identical with thein, the peculiar principle of tea.
Notwithstanding the quantity of nitrogen in its composition, caffein does not putrefy, even when its solution is kept for some time in a warm place.
The Hanoverian Pharmacopoeia directs caffein to be made by precipitating a decoction of coffee with acetate of lead, filtering and washing the precipitate, evaporate the liquids to dryness, and after mixing the powdered extract with sand, the mass is sublimed in a Mohr's apparatus, just as in making benzoic acid.
Coffee undergoes considerable change during the roasting process. It swells up very much, acquiring almost double its original volume, while it loses about 20 per cent, of its weight. It acquires, at the same time, a peculiar odor entirely different from that of the unaltered grains, and a decidedly bitter taste. A volatile oil is developed during the process, and according to Chenevix, a portion of tannin. The caffein does not appear to undergo material change, as, according to Garot, it may be extracted unaltered from the roasted coffee. The excellence of the flavor of roasted coffee depends much upon the manner in which the process is conducted, and the extent to which it is carried. It should be performed in a covered vessel, over a moderate fire, and the grains should be kept in constant motion. When these have acquired a chestnut-brown color, the process should cease. If too long continued, it renders the coffee unpleasantly bitter and acrid, or by reducing it to charcoal, deprives it entirely of flavor. The coffee should not be burnt long before it is used, and should never be kept in the ground state, as it loses much of its agreeable flavor and activity.
Properties and Uses. — An infusion of roasted coffee is an agreeable stimulant, antisoporific, and antiemetic. It moderately excites the circulatory system, and stimulates the digestive function; though if taken in large quantities it produces troublesome nervous and dyspeptic affections. A cup of strong coffee will cause a degree of wakefulness for several hours, and it may be administered for the purpose of resisting, to a certain extent, the intoxicating and soporific influence of opium and alcohol. In poisoning from opium, it should always be given. It has also proved temporarily useful in light nervous headaches, asthma, hysteria, obstinate chronic diarrhea, and also calculous nephritis. It is contra-indicated in all inflammatory affections of a high grade. Dr. A. Brown, of Cincinnati, has found a strong decoction of the pulverized, unroasted coffee, a superior remedy in some forms of chlorosis and amenorrhea. When fullness of the head, and pain in the back are present, he gives a gentle purgative, then uses the warm foot-bath, and administers the decoction in wineglassful doses every half hour or hour.
Coffee has also been used with much success in hooping-cough, in the form of syrup, made with the extract of coffee prepared without heat, or a strong infusion by percolation, given in small and repeated doses. Dr. L. Delahage gives the following formulae as almost infallible : Take of syrup of extract of coffee four pounds, extract of belladonna, extract of ipecacuanha, of each two scruples. Mix together. Dose, two fluidrachms or a dessertspoonful, morning and noon, and double this dose at night on going to bed, for children of three to five years old; it should be taken in two or three tablespoonfuls of warm water.
The Citrate of Caffein, recommended as a remedy for the idiopathic headache, called migraine, (pain in the forehead), may be obtained by two processes ; the most simple consists in infusing finely-ground raw coffee in a very weak solution of citric acid, at the temperature of 176° F., filtering the liquid while yet hot, adding two-thirds of its volume of ether, and agitating the mixture strongly, to remove the chlorogenic acid from the watery solution. The latter is separated from the supernatant ether, and is carefully evaporated with a gentle heat. The citrate of caffein crystallizes in long needles, which, when redissolved in distilled water and again evaporated, are obtained in beautiful, long acicular white silky crystals, in radiating groups.
The second process consists in making the compound by the direct union of its constituents, the caffein being dissolved in a weak solution of citric acid at the temperature of 112° F., and the solution evaporated till the citrate crystallizes.
This salt is very soluble in water, and is assimilated much more readily than pure caffein when taken into the stomach. It consists of one equivalent of caffein, three of citric acid, and two of water. It may be made into a pill mass with some simple extract, say eight grains of the salt to fifteen of the extract, and divided into ten pills, of which one pill may be given every hour or two. Or, two drachms and a half of the salt may be dissolved in four ounces of simple syrup, of which one tablespoonful may be given as above, according to the violence of the attack.