Cloves are the dried flower-buds of Eugenia caryophyllata, Thunb." Br.

The clove-tree is a small tree inhabiting the Moluccas Island and Southern Philippines. It has a pyramidal form, is evergreen, and is adorned throughout the year with a succession of beautiful rosy flowers. The stem is of hard wood, and covered with a smooth, grayish bark. The leaves are opposite, petiolate, about four inches in length by two in breadth, obovate-oblong, acuminate at both ends, entire, sinuate, with many parallel veins on each side of the midrib. They have a firm consistence and a shining green color, and when bruised are highly fragrant. The flowers are disposed in terminal corymbose panicles, and exhale a strong, penetrating, and grateful odor.

The natural geographical range of the clove is extremely limited, being confined to the Moluccas or, as they were one time called, Clove Islands. According to Flǖckiger, cloves were known in Western Europe as early as the sixth century, long before the discovery of the Moluccas by the Portuguese. After the conquest of the Molucca Islands by the Dutch, the monopolizing policy of that commercial people led them to extirpate the trees in nearly all the islands except Amboyna and Ternate, which were under their immediate inspection. Notwithstanding their jealous vigilance, a French governor of the Islands of France and Bourbon, named Poivre, succeeded, in the year 1770, in obtaining plants from the Moluccas and introducing them into the colonies under his control. Five years afterwards the clove-tree was introduced into Cayenne and the West Indies, in 1803 into Sumatra, and in 1818 into Zanzibar. At present the spice is cultivated both in the West and East Indies, in tropical Africa, and in Brazil. Approximately seven-eighths of the world's clove supply is grown in Zanzibar.

 The unexpanded flower buds are the part of the plant employed under the ordinary name of cloves. They are first gathered when the tree is about six years old. The fruit has similar aromatic properties, but much weaker. The buds are at first white, then become green, and then bright red, when they must be at once collected, which is done by hand picking, or by beating the trees with bamboos and catching the falling buds. In the Moluccas they are said to be sometimes immersed in boiling water and afterwards exposed to smoke and artificial heat before being spread out in the sun. In Zanzibar, Cayenne, and the West Indies they are dried simply by solar heat. The stems of the flowers also enter commerce. They possess the odor and taste of the cloves, but they are worth only about one-fifth the price of the cloves, as they are deficient in volatile oil. They are largely used as an adulterant in ground cloves, and are used in the manufacture of oil of cloves. In France they are generally known by the name of griffes de girofle.

Although it is stated that as early as 266 B.C., during the reign of the Han dynasty, the Chinese court officers were accustomed to hold cloves in their mouths before addressing the sovereign, that their breath might have an agreeable odor, the spice seems to have been first introduced into Europe in the fourth century, and became a great source of wealth to the enterprising merchants of mediaeval Venice, who obtained it from the Arabians. After the discovery of the southern passage to India, the trade in this spice passed into the hands of the Portuguese, but was subsequently wrested from them by the: Dutch, by whom it was long monopolized. (For detailed information as to method of cultivation, see P. J., June, 1890.)

In commerce the varieties of cloves are known by the names of the localities of their growth, and so closely resemble one another as to be distinguished only by experts. The Penang cloves have been especially esteemed. The Bencoolen cloves from Sumatra are by many druggists deemed equal to them. The Amboyna and Molucca cloves are stated to be thicker, darker, heavier, more oily, and more highly aromatic than those cultivated elsewhere.

Assay. � Proceed as directed under volatile ether-soluble extractive." U. S.

"About fifteen millimetres long, each consisting of a dark-brown, wrinkled, sub cylindrical, somewhat angular calyx tube which tapers below and is surmounted by four thick, rigid, patent teeth, between which are four paler, imbricated petals enclosing numerous stamens and a single style. Odor strong, fragrant and spicy; taste very pungent and aromatic. Cloves emit oil when indented with the finger-nail. Ash not more than 7 per cent." Br.

Their color is externally deep brown, internally reddish; their odor strong and fragrant; their taste hot, pungent, aromatic, and very permanent. The best cloves exude a small quantity of oil on being pressed or scraped with the nail. When light, soft, wrinkled, pale, and of feeble taste and odor, they are inferior. Those from which the essential oil has been distilled are sometimes fraudulently mixed with the genuine. For monograph on the microscopical structure of cloves, clove stems and clove fruit see Winton and Moeller, " The Microscopy of Vegetable Foods." Powdered cloves sometime contain an excess of clove stems, and may be adulterated with allspice, wheat middlings and powdered peas or beans. Occasionally clove stems alone are ground and sold as cloves. It is claimed that an enormous quantity of exhausted cloves are dishonestly marketed. The amount of volatile ether extract is the best criterion of the value of cloves.

The most important constituent is a volatile oil (see Oleum Caryophylli). Trommsdorff obtained from 1000 parts of cloves 180 of volatile oil, 170 of a peculiar tannin, 130 of gum, 60 of resin, 280 of vegetable fiber, and 180 of water. Wm. L. Peabody (1895) found the percentage of tannin in cloves to range from 10 to 13 per cent., and that it has the same chemical composition as gallotannic acid. Lodibert afterwards discovered a green fixed oil, and a tasteless, white, resinous substance which crystallized in silky needles, soluble in ether and boiling alcohol, and exhibiting neither alkaline nor acid reaction. This substance was called by Bonastre, caryophyllin. To obtain it, the ethereal extract of cloves is treated with water, and the white substance thrown down is separated by filtration, and treated repeatedly with ammonia to deprive it of impurities.

Its formula as determined by Mylius (S. Chem, G., 1873) is C₂₀H₃₂O₂. On oxidizing with fuming nitric acid it forms caryophyllic acid, C₂₀H₃₂O₆. Dumas discovered another crystalline principle, which, like caryophyllin, is soluble in alcohol and ether, but differs from that substance in becoming red when touched with nitric acid. Bonastre proposed for it the name of eugenin. (J. P. C., xx, 565.) It has the formula C₁₀H₁₂O₂, and is isomeric with eugenol.

Water extracts the odor of cloves with comparatively little of their taste. All their sensible properties are imparted to alcohol; and the tincture when evaporated leaves an excessively fiery extract, which becomes insipid if deprived of the oil by distillation with water, while the oil which comes over is mild. Hence it has been inferred that the pungency of this aromatic depends on a union of the essential oil with the resin. For an account of the oil, see Oleum Caryophylli. The infusion and oil of cloves are reddened by nitric acid, and rendered blue by tincture of ferric chloride, facts of some interest, as morphine gives the same reactions.

Uses. � Cloves are among the most stimulant of the aromatics, but, like others of this class, act less upon the system at large than on the part to which they are immediately applied. They are sometimes administered in substance or infusion to relieve nausea and vomiting correct flatulence, and excite languid digestion; but their chief use is to assist or modify the action of other medicines. They enter into several official preparations. The French Codex directs a tincture of cloves to be prepared by digesting for ten days, and afterwards filtering, a mixture of three ounces of powdered cloves and sixteen of 80 per cent, alcohol.