BENZOIN or GUM BENJAMIN, a balsamic resin ob tained from Styrax Benzoin, a tree of considerable size, native to Sumatra and Java, and from other species of Styrax. It is obtained by making incisions in the bark of the trees, and appears to be formed as the result of the wound, not to be secreted normally. There are several varieties of benzoin in commerce : (I) Siam ben zoin, which apparently comes from S. tonkinese is the finest and most aromatic. The odour of Siam benzoin is partly due to the presence of vanillin, and it contains as much as 38% of benzoic acid but probably no cinnamic acid. (2) Sumatra benzoin occurs only in masses formed of dull red resin enclosing small white masses. It contains about 20% of cinnamic acid in addition to 18 or even more of benzoic. (3) Palembang benzoin, an inferior vari ety, said to be obtained from Styrax Benzoin in Sumatra, consists of greyish translucent resinous masses, containing small white opaque masses. It does not appear to contain cinnamic acid. Large quantities of benzoin are used as incense. Its medicinal uses de pend on the contained benzoic acid (q.v.). Compound tincture of benzoin is used in treatment of respiratory diseases, etc.
Benzoin, in chemistry, is a colourless, crystalline solid, readily soluble in alcohol and ether, melting at 137° C. and boiling at C. It owes its name to the circumstance that it is a poly meride of benzaldehyde, which in turn derives its name from benzoic acid (q.v.). This acid was first discovered in Gum benzoin (16o8) from which material the acid may be obtained by sublimation (acidum benzoicum ex resins). It partakes of she structure and properties both of a ketone and an alcohol (qq.v.), having the structural formula It may be prepared by boiling an alcoholic solution of benzaldehyde with potassium cyanide; by reducing benzil with zinc and acetic acid ; or by the oxidation of hydrobenzoin Owing to the readiness with which it is oxidized, it acts as a reduc ing agent, giving a red precipitate of cuprous oxide with Fehling's solution in the cold. Chlorine and nitric acid oxidize it to benzil; chromic acid mixture and potassium permanganate, to benzoic acid and benzaldehyde. On heating with zinc dust, desoxybenzoin is obtained; sodium amalgam converts it into hydrobenzoin ; and fuming hydriodic acid at I 30° C. gives dibenzyl (C6H5CH2•CH2•C6H5)•