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XV.—On the Constitution of Oil of Cajeput. By Maximitian Scumipt, Assistant 
to Professor ANDERSON in the Laboratory of Glasgow College. 
(Read 17th April 1860.) 
The constitution and properties of the essential oils attracted considerable 
attention during the earlier period of the investigations in organic chemistry, and 
several of them have contributed in no small degree to the development of the 
general doctrines of that department of the science. A majority of these sub- 
stances, however, may be said to be still almost unknown, all the information we 
possess regarding them being restricted to a single analysis, made on what was 
obviously a mixture, or to a few observations of a general and often indefinite 
character. The complex nature of many essential oils, and the want of experience 
and easy processes for the separation of their constituents, have hitherto deterred 
chemists from attempting their minute examination, but the progress of the 
science has increased our knowledge of the methods of investigating these sub- 
stances, and renders it important that their true constitution and position in the 
chemical system be definitely fixed. With this object I have taken up the investi- 
gation of Oil of Cajeput ; our information regarding which is confined to a single 
analysis made by BLANCHET and SELL, some five and twenty years ago. 
Oil of Cajeput is prepared in the East Indies, by distilling along with water the 
leaves of Melaleuca Leucadendron ; it was formerly used to a great extent as an 
external and even internal medicine, but has now become more or less obsolete, and 
is seldom met with in a pure or unchanged state, except in the hands of wholesale 
druggists. As introduced into Europe, it possesses a light-green colour resembling 
a dilute solution of chloride of chromium, which is caused by a resinous colouring 
matter dissolved in it, but in so small a proportion, that I have hitherto failed to 
obtain it in sufficient quantity and pure enough for elementary analysis. I sus- 
pected, in common with other observers, that this coloration might be due to a salt 
of copper; but although I always detected this metal in the crude oil, by treating 
it with nitric acid, when, after its total destruction, the blue nitrate of copper 
was left behind, or by the still simpler process of passing sulphuretted hydrogen 
through the oil, when a black precipitate of sulphuret of copper was immediately 
formed; I nevertheless satisfied myself that it possessed a green colour of its own; 
since, after the removal of the sulphuret of copper, it exhibited the same appear- 
ance, and, on distillation, the latter fractions which passed over had a decided 
green colour, which could not be due to any salt of copper, as none of its com- 
_ pounds volatilise at the temperature at which these fractions distilled; nor 
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