Encyclopædia Britannica, Ninth Edition/Turmeric

TURMERIC, the tuberous root of Curcuma longa, L., an herbaceous perennial plant belonging to the natural order Zingiberaceæ. It is a native of southern Asia, being cultivated on a large scale both on the mainland and in the islands of the Indian Ocean. Turmeric has been used from a remote period both as a condiment and as a dye stuff, and to a more limited extent as a medicine. In Europe it is employed chiefly as a dye, also as an ingredient in curry powder and as a chemical test for alkalies. The root is prepared by cleaning it and drying it in an oven. There are several varieties (Madras, Bengal, Gopalpur, Java, China, and Cochin turmeric), differing chiefly in size and colour and to a slight degree in flavour. Some of these consist exclusively of the ovate central tubers, technically known as " bulbs," and others of the somewhat cylindrical lateral tubers, which are distinguished in trade as " fingers." Both are hard and tough, but break with a short resinous or waxy fracture, which varies in tint from an orange brown to a deep reddish brown.

Turmeric has a characteristic odour and an aromatic taste. The aroma it owes to a complex essential oil, which consists principally of an alcohol called turmerol (formula C₁₉H₂₈0), which differs from carvol in being unable to combine with hydrogen sulphide; the other constituents of the oil have not been determined. The colour is due to curcumin, C₁₄H ₁₄O₄, of which the drug contains about 0·3 per cent. It possesses the properties of an acid, forming red-brown salts with alkalies and being precipitated from alkaline solutions by acids. When pure it forms yellow crystals having a vanilla odour and exhibiting a fine blue colour in reflected light. It is soluble in alcohol, in chloroform, and in alkaline solutions, but only sparingly in water. Paper tinged with a tincture of turmeric exhibits on the addition of an alkali a reddish brown tint, which becomes violet on drying. This peculiarity was pointed out by Vogel in 1815, and since that date turmeric has been utilized as a chemical test for detecting alkalinity. In India the drug is considered to possess cordial and stomachic properties: a decoction made with milk and sweetened is used as a remedy for colds. Externally it is employed in skin diseases and in the form of a cooling lotion for relieving the pain of conjunctivitis; the fumes of the burning tubers directed into the nostrils relieve congestion in cases of coryza. The cultivation of turmeric is carried on most successfully in light rich soil in well-watered districts. The plant is easily propagated by offsets. An acre yields about 2000 lb. Turmeric is said to grow in large quantities on the slopes of hills bordering the plains of the Beni in Bolivia and also in Panama. Several species of Curcuma and of allied genera yield yellowish aromatic roots. In Sierra Leone a kind of turmeric is obtained from a species of Canna.