372 STYRACE. 
the microscopical examination of splinters of the resin under 
oil of turpentine. 
‘¢ Siam berizoin is imported in cubic blocks, which take their 
form from the wooden cases in which they are packed while 
the resin is still soft.” 
“Sumatra Bznzoin.—Prior to the renewal of direct com- 
mercial intercourse with Siam in 1853, this was the sort of 
benzoin most commonly found in commerce. 
“Tt is imported in cubic blocks exactly like the preceding, 
from which it differs in its general greyer tint. The mass, 
however, when the drag is of good quality, contains numerous 
opaque tears, set in a translucent, greyish-brown resin, mixed 
with bits of wood and bark. When less good, the white tears 
are wanting, and the proportion of impurities is greater. We 
have even seen samples consisting almost wholly of bark. In 
odour, Sumatra benzoin is both weaker and less agreeable than 
the Siam drug, and generally falls short of it in purity and hand- 
some appearance, and hence commands a much lower price. 
The greyish brown portion melts at 95°, the tears at 85° C.” 
Chemical composition.—Benzoin consists mainly of amorphous 
resins perfectly soluble in alcohol and in potash, having slightly 
acid properties, and differing in their behaviour to solvents. 
If two parts of the drug are boiled with one part of caustic lime 
and twenty parts of water, benzoic acid is removed. From the 
residue the excess of lime is dissolved by hydrochloric acid, 
and the remaining resins washed and dried. About one-third | 
of them will be found readily soluble in ether, the prevailing 
portion dissolves in alcohol, and a small amount remains 
undissolved. Subjected to dry distillation, benzoin affords as 
chief product Benzoic acid, C7H®O*, together with empy- 
reumatic products, Benzoic acid exists ready formed in the 
drug to the extent of from 14 to 18 per cent., its extraction is 
easily accomplished by the aid of an alkali, most advantage- 
ously by milk of lime, which: does not combine with the 
amorphous resins. Most pharmacopceias require not the in- 
odorous acid obtained by a wet process, but that afforded by 
‘sublimation, which contains a small amount of fragrant iid 
