Description

This variety of benzoin is collected in the Siamese province of Luang Prabang, in the neighbourhood of the Mekong new wood in which a ring (or sometimes two rings) of oleo-resin ducts are formed. By the breaking down of the tissue intervening between the ducts large schizolysigenous ducts are produced in which considerable quantities of oleo-resin are secreted. These ducts open on to the wounded surface over which their secretion is discharged. Similar ducts are also formed in the bark. The benzoin thus formed partly accumulates between the bark of the tree and the trunk and partly exudes from the incisions; it is allowed to get firm and is then collected, bought by Chinese traders, softened by heat or hot water, and packed in oblong boxes, being often, it is said, mixed with vegetable debris in the course of repacking.

Sumatra benzoin occurs in masses consisting of opaque, white tears embedded in a dull, greyish-brown, or sometimes reddish-brown matrix. It possesses an agreeable, though not very powerful odour, recalling storax, and a slightly acrid taste. When cautiously heated it melts and evolves whitish irritating fumes of benzoic and cinnamic acids. When a little of the crushed resin is warmed with alkaline solution of potassium permanganate benzaldehyde is evolved, indicating the presence of more than traces of cinnamic acid in the drug.

Sumatra benzoin is frequently contaminated with pieces of bark and other debris, especially in the angles and round the sides of the box in which it is packed.

Good Sumatra benzoin should not contain more than 10 per cent. of substances insoluble in alcohol, whilst inferior qualities often yield up to 30 per cent.; it should also not afford more than 5 per cent. of ash.

Constituents

Sumatra benzoin consists principally of two alcohols combined with cinnamic acid, and associated with free benzoic and free cinnamic acid. Of the two alcohols, one, benzoresinol, is probably identical with the siaresinol of Siam benzoin; the nature of the other is not definitely known; it has been stated to be sumaresino-tannol, but this alcohol may have been produced from the alcohol originally present (? lubanol) by oxidation during the extraction (compare Siam benzoin). The drug contains, in addition, traces of benzaldehyde, vanillin (1 per cent.), phenylpropyl cinnamate, styrol, and styracin, all of which combine to produce its particular fragrance.

The total amount of aromatic acids present in the commercial drug, freed from vegetable debris and moisture, averages 26 per cent., free cinnamic acid 10.3, combined cinnamic acid 7.3, free benzoic acid 6.5 and combined benzoic acid 2.5.