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EXVI. Ona volatile concrete Oil existing in the Nut-galls of 
the Oak. By Dr. Jos. Brancut, Professor of Chemistry in 
the Imperial and Royal University of Pisa. Contained in a 
Letter from Dr. Brancut to Sig. R. Gurbr, Professor of 
_ Theoretical Physies. 
Waren I spoke to you some time ago of a volatile concrete 
cil which [ had obtained from oak-galls by the same meanis with 
which other volatile oils in general are extracted from aromatic 
vegetables, I prontised to give voua more extensive description 
of it. 1 now fulfil my promise in this letter. In the beginning 
of 1814, having distilled a few ounces of oak-galls broken and 
Steeped in a sufficient quantity of water, I observed swimming 
on the odorous and turbid fluid which had passed into the res 
ceiver some drops of an oil, which in a short time became solid. 
Various occupations, especially those of my professional chair, 
and a series of experiments which I had commenced on the che. 
mical properties of colouring matters, hitherto prevented me 
‘from investigating this fact. But having repeated the distilla- 
tion of galls, I obtained,as before, some drops of oil sensibly yel- 
low, swimming on the surface of a whitish odorous and saporifie 
liquid, which in the space of some hours became sufficiently clear, 
by the precipitation of a whitish substance in flakes heavier than 
‘the liqhid itself. On filtrating the fluid through blotting-paper, 
these thin semitransparent and shining flakes remained, and 
were the same drops of oil which had taken the character of a 
white odorous opaque unctuous matter, and of a consistence 
nearly similar to what is called butter of cocoa. This white 
matter, it appears, differs from the above-mentioned thin flakes 
~ by having less specific gtavity, and by its aspect, which is not 
‘shining; but both have the property of volatile oil—both have’ 
‘the following characters : 
fot Ist. They have a hitter caustic taste, and the same odour as 
galls when pulverized. 
— 2d. They ave slightly soluble in water, which imbibes their 
smell and taste, . 
7 _. 3d. They readily and» copiously dissolve in alcohol. ‘The so- 
BS lation which results ts rendered turbid by a small quantity of 
water, but if more or Jess time it reassumes its transparency by 
the addition of a proportionate quantity of water. 
a 4th. ‘They tnite to fixed oil, as that of olives; and to the vo- 
-latile oils, as turpentitic and lavender. 
oth, Exposed.on a piece of blotting paper (or even writing 
paper) to the action of a slight degree of heat, they liquefy and 
dasine the paper so.as to render it diaphanous, — Continuing 
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Vol. 50, No, 236. Dec, 1817. Ce however 
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