GAMBOGE (gam-boon (from Camboja, a name of the district whence it is obtained), a gum-resin from Garcinaa Han burii (Nat. Ord. Guttiferae), a dioecious tree with leathery, laurel like leaves, small yellow flowers, and usually square-shaped and four-seeded fruit, indigenous to Cambodia and parts of Siam and the south of Cochin China, formerly comprised in Cambojan terri tory. The juice, which when hardened constitutes gamboge, is contained in ducts in the middle layer of the bark, and from this it is procured by making incisions, bamboo joints being placed to receive it as it exudes. Gamboge occurs in commerce in cylindrical pieces, known as pipe or roll gamboge, and also, usually of inferior quality, in cakes or amorphous masses. It is of a dirty orange externally ; is hard and brittle, breaks with a conchoidal and reddish-yellow, glistening fracture, and affords a brilliant yellow powder; is odourless, and has a taste at first slight, but subsequently acrid ; forms with water an emulsion ; and consists of from 20 to 25% of gum soluble in water, and from 7o to 75% of a resin. Its commonest adulterants are rice flour and pulverized bark.
Gamboge is a drastic hydragogue cathartic, less active only than Croton oil and elaterium. A small quantity is absorbed, adding. a yellow ingredient to the urine and acting as a mild diuretic. Its irritant action on the skin may cause the formation of pustules. Gamboge is used as a pigment, and as a colouring matter for varnishes. It appears to have been first brought into Europe by merchants from the East at the close of the 16th century.