QUERCUS INFECTORIA. 
269 
other process. The watery infusion reddens tincture of litmus, and 
forms precipitates with solutions of the following substances: — 
isinglass, lime water, subcarbonate of potass, acetate of lead, sul- 
phate of copper, nitrate of silver, sulphate of iron, nitrate of mer- 
cury, tartrate of antimony, and the infusions of columba root, 
cusparia bark, and cinchona bark. The muriate of mercury renders 
the infusion milky and opaque, but no precipitate is formed. 
Nitrous acid, sulphate of zinc, infusion of quassia, ammonia, and 
infusion of saffron occasions no precipitate. The ethereal tincture, 
when evaporated on water, leaves on the side of the glass an opaque 
pellicle, and on the surface of the water small drops of an oily 
resinous-like matter, while the substratum of water becomes charged 
with tannin and gallic acid. The alcoholic tincture reddens litmus, 
and forms precipitates with the same re-agents as the watery infu- 
sion. To what principles these precipitates are owing remains to 
be ascertained. It is observed by Vauquelin, that the infusions of 
nutgalls and of cinchona, agree in precipitating both gelatine and 
tartrate of antimony, and that they precipitate each other. We are 
told by Dr. Duncan that, in his experiments, " a saturated mixture 
of the infusions of nut-galls and cinchona still precipitates gelatine, 
but infusions, separately saturated by gelatine, do not act on each 
other. Hence it appears, that the action of these infusions on each 
other, depends on principles contained in each, compatible with the 
presence of tannin, but re-acting on each other, and that gelatine 
precipitates these principles along with the tannin. 
" It has been generally asserted, that the precipitate of 
tannin and gelatine is insoluble in water, either cold or hot ; but 
I find that in boiling water, it not only becomes soft and viscid, but 
a certain portion is dissolved, which separates again when the solu- 
tion cools." * 
M, Braconnot has discovered in nut-galls a new acid, which he 
has named Ellagic.j- This acid is in the form of a white powder, 
with a slight tinge of red, insipid, inodorous, and insoluble in boil- 
ing water; combined with nitric acid and gently heated, the mixture 
acquires a deep red colour. Galls also yield by distillation with 
water, a small portion of a concrete volatile oil.| 
Medical Properties and Uses of Galls. Galls are the 
* Edinburgh New Dispensatorj'. 
•f- Ann, de Cliim. et Phjs. torn. ix. p. 187. 
i PLil. Mair. 
