_Jalap._
QUALITIES. This root is pulverulent, furnishing a powder of a pale
brownish yellow colour. _Odour_, peculiar; _Taste_, sweetish and
slightly pungent. _Chemical Composition._ Resin, gum, extractive,
fecula, lignin, and some salts. The combination of the three first
principles appears requisite for the production of its _full_ cathartic
effect. The gum has been supposed to possess diuretic properties. Very
lately a saline principle has been obtained from Jalap by Mr. Hume,
jun.: but I am not aware that its medicinal properties have been
ascertained. It is procured by macerating the powdered root for twelve
or fourteen days in acetic acid, by which a solution is obtained, which
must be filtered, and then saturated with ammonia; the mixture is to be
shaken violently, when a _sabulous_ deposit will take place, and a few
crystals be collected on the sides of the vessel; both of these must be
collected, and washed in distilled water; and then redissolved in
concentrated acetic acid, and reprecipitated by ammonia added in excess.
By which means, small white acicular crystals are thrown down, to which
the name of _Jalapine_ has been given. SOLUBILITY. Proof spirit is its
appropriate menstruum. MED. USES. It is a cathartic of a stimulating
description, acting principally upon the colon, and, notwithstanding the
tormina it may sometimes induce, it is no less safe than efficacious; as
a hydragogue purgative it has been greatly extolled, but for such a
purpose it will answer better in combination, as in _Form. 73_. Its
action is said to be promoted by the addition of Ipecacuan, or
tartarized antimony. (_Form. 84._) In dropsy its union with
super-tartrate of potass is calculated to promote its beneficial
operation. FORMS OF EXHIBITION. That of powder is the most eligible,
especially when combined with some other powdered substance:
pulverization increases its activity, see _Pulveres_. Van Swieten
advised it to be pulverised, and mixed with sugar, and a small quantity
of some aromatic. The addition of Soap is supposed to render its
operation much milder, and the Prussian Pharmacopœia contains a formula
for such a combination, which is said to operate mildly and promptly. To
this preparation the name SAPO JALAPINUS[546] is given. DOSE, grs. x to
ʒss. OFFICINAL PREPARATIONS. _Pulv. Jalap. comp._ E. _Extract._ _Jalap_.
L.E.D. _Tinct. Jalap_. L.E.D. _Tinct. Sennæ comp._ E. (=B=).
ADULTERATIONS. _Briony root_ is sometimes mixed with that of jalap, but
it may be easily distinguished by its paler colour and less compact
texture; and by not easily burning at the flame of a candle. When the
_teredo_ has attacked it, it should be rejected.