TARTARIC ACID was first obtained in a separate state by Scheele ; it exists in several vegetable products, but principally in bi tartrate of potash, which is usually called cream of tartar, a salt which is deposited from wine.
Tartaric acid is colourless, inodorous, and very sour; it occurs in crystals of a consider able size, the primary form of which is an oblique, rhombic prism; it suffers no change by exposure to the air ; water at 60° dissolves about one-fifth of its weight, and at 212° twice its weight. It combines readily with alkalies, earths, and metallic oxides ; and these salts are called tartrates : many of them are usefully applied in the arts.
Tartaric acid is largely employed as a dis charge in calico printing, and for making what are called sodaic powders, which are imitations of soda-water.
Tartaric acid is entirely confined to the vegetable kingdom, and is found free or un combined in tamarinds, in the unripe grape, and in pepper; and in combination in tama rinds, ripe grapes, gooseberries, mulberries, squill, dandelion, chenopodium vulvtuia, in various species of pines, and as tartrate of lime in the fruit of the Rhus typhina.
TEA. Though now so extensively employed, the introduction of tea into Europe is of com paratively recent origin. Pepys in his' Diary,' writes, Sept., 25, 1661, I sent for a cup of tea (a Chinese drink), of which had never drank before.' The Dutch East India Com pany probably first introduced it into Europe, and from Amsterdam it was brought to London.
The species of the genus Thea are few in number. Some botanists are of opinion that even these are varieties of a single species called Thea Chinesis ; but there are usually said to be two species yielding green and black tea respectively. The Asam tea-plant, which has lately attracted so much attention, seems to partake of the characters of both of the foregoing, and is regarded by some botanists as a distinct species. Tea is cultivated in China over a great extent of territory. Dr. Wallich mentions it as being cultivated in Cochin-China, in 17° N. lat. We know it is cultivated in the southern provinces of Yunnan and of Canton. If we proceed north we find the principal cultivation of teas for the foreign trade is between 27° and 31° N. Lat.; but tea
is said to be produced in several places to the northward of 31° ; even in and also in the Japanese Islands, which extend from 30° to N. lat.
The culture of the tea-plant in China seems simple enough. The plants are raised from seeds, sown in the places where they are to remain. Several are dropped into holes four or five inches deep and three or four feet apart, shortly after they ripen ; or in Novem berand December, as they do not preserve well, from their oiliness. The plants rise up in a cluster when the rain comes on, and require little further care, except that of removing weeds, till they are three years old, when they yield their first crop of leaves. They are seldom transplanted, but sometimes four to six plants are put close together, so as to form a fine bush. After growing seven or ten years they are cut down in order that the numerous young shoots which then spring out may afford a more abundant supply of leaves. In some districts the bushes grow unrestrained, in others they are regularly pruned, to keep them low. The gathering of leaves is performed with great care : they are usually gathered singly, first in March or May (according to the district), when the young leaves are scarcely expanded ; the second about two months later, or May and June; and the third in August, or about six weeks after the second; but the times neces sarily differ in different districts, as well as the number of crops which are obtained, some avoiding the third for fear of injuring the hushes. When the leaves are gathered they are dried in houses which contain small furnaces, on each of which there is a flat iron pan, and upon this, when heated, the leaves, partially dried by exposure to the sun, are thrown ; the leaves require frequent shifting and turning. When All are properly dried, they are quickly removed either by the hand or with a shovel, and either thrown upon a mat or into baskets which are kept ready. to receive them. They are then removed to a table where they are rolled and cooled, and the process is repeated; after which they are sifted and sorted into several varieties.