Catechu

Catechu, a substance employed in tanning and dyeing and medicinally as an astringent. The catechu of commerce is obtained chiefly from two East Indian trees (Acacia Catechu and A. Suma). The former is common in most parts of India, and also in tropical East Africa, and the latter grows in Southern India, Bengal, and Gujerat. Catechu is known in India by the name kát or kut. Cutch is another form of one or other of these names, and is a common commercial name. The trees are cut down when they are about a foot in diameter, and according to some accounts only the heartwood is used, but other reports say that the whole of the woody part of the trunk is utilised. The catechu is obtained by cutting it into small chips, and boiling it in water, straining the liquid from time to time, and adding fresh supplies of chips, till the extract is of sufficient consistency to be poured into clay moulds; or when of the thickness of tar, it is allowed to harden for two days, so that it will not run, and is formed into balls about the size of oranges, which are placed on husks of rice or on leaves, and appear in commerce enveloped in them. Catechu is of a dark-brown colour, hard and brittle, and when broken has a shining surface. It possesses an astringent taste, but no odour. It is a very permanent colour, and is employed in the dyeing of blacks, browns, fawns, drabs, &c. Ordinary commercial catechu or cutch is composed of catechu-tannic acid, which is soluble in cold water, and catechin or catechuic acid, which is nearly insoluble in cold but soluble in boiling water. The latter can be separated in the state of minute, acicular, colourless crystals. It is often adulterated with earthy substances, but its ready solubility in water and alcohol should at once show the presence of such by leaving them behind in an insoluble state. Areca or Palm Catechu, sometimes called Ceylon Catechu, differs wholly from the above. It is got from the ripe nuts of the Betel palm, which yield, by boiling, a black, very astringent extract, resembling true catechu, but of inferior quality. This substance is rarely exported from India (see ARECA, BETEL).—Gambir (q.v.) may be regarded as a kind of catechu. Terra Japonica, or Japan Earth, is an old name for catechu, not quite disused, given in mistake as to its nature and origin. About 6000 tons of catechu or cutch are annually imported into Great Britain from India.