QUALITIES. _Form_, long pieces, sometimes flat, as if they had been
compressed; they are heavier, harder, and more compact than those of the
preceding species, and are seldom perforated with holes; _Odour_,
stronger; _Taste_, more nauseous; white streaks less numerous, and they
afford a powder of a redder shade than those of _Turkey_ rhubarb.
CHEMICAL COMPOSITION. It differs from the _Turkey_ in containing less
tannin and resin, and according to the experiments of Mr. A. T. Thomson,
less oxalate of lime, in the ratio of 18 to 26. It contains however more
extractive and gallic acid. SOLUBILITY. Water takes up one half of its
weight, but the infusion, although more turbid, is not so deep coloured
as that of Russian rhubarb; alcohol extracts 4 parts in 10. It habitudes
with acids, alkalies, and neutral salts, differ likewise from those of
the Russian variety, as Mr. A. T. Thomson has exhibited in a very
satisfactory manner. (_London Dispensatory, Edit. 3, p. 474._)
ADULTERATIONS. The inferior kinds of _Russian_, _East Indian_, and even
_English_ rhubarb, are artfully dressed up and sold under the name of
Turkey rhubarb. I am well informed that a number of persons in this
town, known in the trade by the name of _Russifiers_, gain a regular
livelihood by the art of dressing this article, by boring, rasping, and
then colouring the inferior kinds; for which they charge at the rate of
eighteen-pence per pound. The general indications of good rhubarb are,
its whitish or clear yellow colour, and its possessing the other
characteristic properties as above mentioned; it ought also to possess
in an eminent degree the peculiar odour, for when this is dissipated,
the powers of the medicine are nearly destroyed. In the form of powder,
rhubarb is always more or less mixed with foreign matter; the detection
of which can be alone effected by a trial of its efficacy.