The difficulty of solution in the vegetable astringents has been
complained of by various writers on the _Materia Medica_. Water and
alcohol are the menstrua in use; but great quantities of each are
necessary to procure even a slight impregnation, and much heat and
long boiling are said actually to destroy the astringent quality, and
vegetable texture.[t] As a menstruum capable of dissolving them with
greater facility appeared to be a desideratum, not only in pharmacy,
but in other arts, particularly in that of dying blacks, I resolved to
try Dr. Macbride's method of increasing the solvent power of water, by
means of quick-lime. But as I was aware that the quantity of lime he
made use of in obtaining an aqueous tincture of Peruvian bark, would
be too great for the dyer's use, I wished to use only such a quantity
as would be sufficiently saturated with the air contained in the
vegetable, to be itself precipitated; and to compare the tinctures thus
made, with a standard prepared with simple water.
[t] Vid. Lectures on the Materia Medica, as delivered by William
Cullen, M.D. p. 195.