404 On a volatile concrete Oil 
brown ; not entirely smooth, but with protuberances sufficiently 
considerable : and their cellular tissue is in general of a medium 
consistence between that of the Italian and the Istria galls. . 
These galls yielded a fluid saporific, odorous, a little whitish, and 
without a drop of oil. After settling, there appeared visible, near 
its surface, a very small part swimming, which, with agitation, be- 
came more conspicuous. Separating this by filtrating paper, and 
then exposing the paper to a moderate heat as usual, an odorous 
vapour arose, but less copiously. I have obtained a similar re- 
sult from another kind of Aleppo galls, which differed from the 
preceding in being all of a greenish colour. 
From these experiments, therefore, it appears that the volatile 
oil here spoken of is contained in all the above kinds of gallsy. 
but not in the same quantity ; and it is to be observed, that those 
called Istria galls and black Istria galls, which yielded the 
greatest quantity, are also those which have more odour when 
pounded. 
I have twice repeated the same experiment without the least 
essential difference*. The odorous fluids, which reddened more 
or less the paper tinged with turnsole, by containing a greater or 
less dose of acetic acid, sometimes became limpid ia a short 
time, and sometimes remained turbid many days. Some have 
had no sensible colour, nor did they blacken the solution of sul- 
phate of iron; others were slightly yellowish, and evinced by 
means of this sulphate that they contained a small quantity of 
_gallic acidt. Perhaps these last characters were in consequence 
_of some little of the powder of the galls remaining in the neck 
of the retort, notwithstanding the pains which I took in clear- 
ing it. ’ 
‘The bark of oak and the gland seem to contain a very small 
quautity of our volatile oil, as, having submitted them separately 
to the same process of distillation , they yielded a fluid some- 
* In the second distillation of six ounces of Istria galls I obtained some- 
_what less than a grain of volatile oil, and a little more than a grain from the 
same quantity of Istria black galls. It is also to be remarked, that the li- 
quor in the former was less turbid than in the latter, and that the volatile 
oil separated from the last did not appear in the receiver like drops, but 
formed on the surface of the liquor a thin film which hecame more opaque 
as it cooled. Deyeux from the same quality and quantity of galls did not 
always obtain the same quantity of extract, but sometimes more and some+ 
‘times less. ; 
4 This liquid, which I filtered and preserved in bottles with ground-glass 
stoppers, became more or less altered in the course of a month. Such an 
aiteration, and particularly in odour, appeared very conspicuous on com- 
" paring it with that recently distilled. 
{ For the distillation of six ounces of bark, eighteen ounces of water 
pee eecessary to have some superabundant, and fourteen ounces for tlie 
glands. 
what 
