on the constituent Parts of astringent Vegetables. 251 
but I am inclined to attribute this effect, not to any absorption 
of gallic acid by the skin, but rather to the decomposition of it 
by the long continued action of the atmosphere; for much in- 
soluble matter had been precipitated, during the process of 
tanning, and the residuum contained a small portion of acetous 
acid. 
In ascertaining the quantity of tannin in galls, I found that 
500 grains of good Aleppo galls gave, by lixiviation with pure 
water till their soluble parts were taken up, and subsequent slow 
evaporation, 185 grains of solid matter. And this matter, exa- 
mined by analysis, appeared to consist. 
Of tannin - - - 130 grains. 
Of mucilage, and matter rendered insoluble by 
evaporation - - - 12 
Of gallic acid, with a little extractive matter - 31 
Remainder, calcareous earth and saline matter 12 
The fluid obtained by the last lixiviation of galls, as M. 
Deyeux observed, is pale green ; and I am inclined to believe, 
that it is chiefly a weak solution of gallate of lime. The ashes 
of galls, deprived of soluble matter, furnish a very considerable 
quantity of calcareous earth. And the property which M. 
Deyeux discovered in the liquor of the last lixiviations, of be- 
coming red by the action of acids, and of regaining the green 
colour by means of alkalis, I have observed, more or less, in all 
the soluble compounds containing gallic acid and the alkaline 
earths. 
Kk 2 
