S88 
Selections, 
[no. 4, NEWSERlESj 
with the addition of a small quantity of oxidizing agent, as chlorine, hypo- 
chlorite of lime, or bichromate of potash, yields an essential oil of a fine 
blue, whilst ordinary copaiba containing soft resin" (I still scarcely 
understand), affords hardly any coloured essential oil. The notice con- 
cludes with pointing out a possible sophistication which appears to me little 
to be feared ; it is, that cold sulphuric acid produces with copaiba a purple 
colouration similar to that obtained with cq i-liver oil, so that, as the 
author supposes, dishonest persons might substitute for the latter, a mix- 
ture of olive oil or of some other fatty oil, mixed with a small proportion 
of copaiba. 
Mr. D. Hanbury informs us in his notice, that Wood Oil is extracted 
from Dipterocarpiis turhinatus by a very peculiar prt-cess, which I will 
state in a few words, in order the better to show the'nature of the product. 
To obtain the oU, a large incision is made in the trunk of the tree at about 
30 inches from the ground, on which a fire is lighted and kept up untU 
the incision is charred : soon after this, the liquid begins to flow. It is 
conducted by a little trough into a vessel placed to receive it. The aver- 
age produce of one of the better trees in a single season, is 30 gallons- 
Roxburgh [from whom this account is taken] ^dds that Wood Oil is also 
produced by Dipterocarpus incamis, D. alatus, and D, costatus. The first 
of these three is reputed to yield the best sort, and in the greatest quan- 
tity. 
The "Wood Oil which forms the subject of Mr. Hanbury 's notice has 
been imported in large quantity from Moulmein in Burmah : when filter- 
ed, it is a transparent liquid of a somewhat dark brown when seen by 
transmitted light, but appearing opaque and of an obscure green if viewed 
by reflected light. It possesses therefore, in a very marked degree, the 
dichroism observable in all resin-oils obtained by the action of fire. I 
particularly notice this character which determines the nature of Wood 
Oil, and shows that it is not simply a natural product like Copaiba ; but 
that it is in part the result of a liquid modification of the Dipterocarpus 
resin, effected by the agency of heat. This Moulmein Wood Oil is of 
somewhat greater consistence than Olive Oil ; it has a sp. gr. of '964, 
and possesses an odour and taste very analogous to those of copaiba. It 
dissolves iij^ twice its weight of absolute alcohol, with the exception of a 
minute residue which is deposited upon repose. 
But the most curious property of this oil, already recognized by Mr. 
Lowe, and afresh observed by Mr. Hanbury, is that of solidifying when 
heated in a closed vial to 266'=' F. ; at this temperature the oil becomes 
turbid and so gelatinous, that it is not displaced upon the inversion of the 
