466 RESINS 



River. Part is exported to London via Singapore, but much reaches 

 the market by way of France. It appears in commerce either as 

 separate tears or in the form of masses composed of tears more or less 

 firmly cemented together by a dark reddish brown, transparent resin. 



The tears vary considerably in size, but seldom exceed 5 cm. 

 in length, by 1 cm. in thickness ; usually they are much smaller. 

 They are flattened, or sometimes, if large, concavo-convex, this shape 

 being evidently caused by the resin accumulating between the trunk, 

 and bark of the tree. They are opaque, brittle, and milky-white 

 internally, but are usually covered with a thin coating of brownish 

 resin, which increases as the tears are kept, being produced from the 

 opaque tear by oxidation. 



Block Siam benzoin consists of small tears cemented together by 

 a glassy, reddish-brown, transparent or translucent resin, which gives 

 them a peculiar varnishy appearance. In this case also the proportion 

 of the red, transparent resin increases as the drug is kept until it 

 becomes its most prominent feature. 



Both varieties of Siam benzoin are characterised by their agreeable 

 fragrant odour, recalling vanilla ; they are almost entirely soluble 

 in alcohol and in ether, yielding only about 2 per cent, of insoluble 

 residue. When quite pure Siam benzoin affords only traces of ash. 



Good commercial samples of Siam benzoin should not yield more 

 than 3 per cent, of substances insoluble in alcohol or more than 1 per 

 cent, of ash. 



Constituents. The white tears of Siam benzoin are crystalline and 

 consist chiefly of the benzoate of a resin alcohol, lubanol. When 

 warmed 'to about 50 the white tears become yellow, red and brown 

 and lose their crystalline character, a change due to oxidation. In 

 addition the drug contains siaresinol benzoate which also is crystalline 

 and an amorphous benzoate which in alkaline solution, readily oxidises. 



Further constituents are vanillin and an oily aromatic liquid, 

 probably an ester of benzoic acid. Siam benzoin contains about 

 39 per cent, of total aromatic acids (about 23 per cent, free and 16 

 per cent, combined), 36 per cent, being benzoic acid and 3 per cent, 

 cinnamic acid (Cocking and Kettle, 1914). This proportion of cin- 

 namic acid is so small that it cannot be detected by the official 

 test (heating with solution of potassium permanganate) . 



PENANG BENZOIN 



Two distinct varieties of Sumatra benzoin have been known under 

 this name. The one, now generally termed storax-benzoin, has a 

 very agreeable odour resembling storax ; the other, known as ' glassy 

 Penang ' or simply * Penang ' benzoin, is distinguished by its glistening, 

 glassy fracture and slight odour. Both varieties are packed like 

 Sumatra benzoin. 



