Olim, Argentum vivum. _Mercury_, or _Quicksilver_.
Mercury, in its metallic state, is never applied to any medical
use,[522] except in visceral obstruction, in hopes of forcing a passage
by its gravity; but under various forms of preparation, it affords a
series of very active remedies. ADULTERATIONS. With the exception of
Peruvian Bark, there is perhaps no active article in the materia medica
more shamefully adulterated; its impurity is at once indicated by its
dull aspect; by its tarnishing, and becoming covered with a grey film;
by its diminished mobility, in consequence of which its globules are
unable to retain the spherical form, and therefore _tail_, as it is
technically expressed. _Lead_ is discovered by dissolving it in nitric
acid, and adding to the solution water impregnated with sulphuretted
hydrogen, when, if lead be present, a dark brown precipitate will ensue.
_Bismuth_, by pouring the nitric solution into distilled water, when it
will appear as a white precipitate. _Zinc_, by exposing the mercury to
heat. _Tin_ is detected by a dilute solution of nitro-muriate of gold,
which throws down a purple precipitate. The presence of lead in mercury
is a most dangerous circumstance; I have once witnessed a case of
_cholica pictonum_ in consequence of it. The usual mode of purifying
quicksilver, by pressing it through chamois leather, will not separate
the lead, if it be, as is generally the case, in combination with
bismuth; for the manner in which the adulteration is effected, is by
melting with a gentle heat these two metals, and adding the alloy to the
mercury; and although this alloy should exceed one-fourth of the whole
bulk, it will pass, together with the mercury, through chamois leather.
On standing, the bismuth will be thrown upon the surface, in the form of
a dark powder, but the lead will remain in solution. The greatest part
of the mercury of commerce comes from Istria and Friuli, and from the
Palatinate, and as it passes through the hands of the Dutch, we must
expect to receive it in a state of alloy. On a superficial examination,
it ought not, when shaken with water, to impart to it any colour; when
agitated or digested with vinegar, it should not communicate a sweetish
taste; and when exposed in an iron spoon to heat, it ought to evaporate
entirely. The French are so well aware of the mischievous extent to
which this metal is falsified, that in their late Codex they direct the
reduction of the _red oxyd_ in order to obtain it; the process however
is too expensive for general adoption. The Italian Jews purify
quicksilver for their barometers, by digesting it in dilute sulphuric
acid, which is by no means an improper process. The mode directed for
the purification of mercury by the London College, (_Hydrargyrum
Purificatum_) is unable to separate it _completely_ from its more
deleterious contaminations. It is a general opinion in Germany, that
mercury, boiled in water, will impart to it an anthelmintic virtue;[523]
this, if it happens, can only depend upon the impurities of the mercury;
but large draughts of cold water are in themselves anthelmintic.
Although metallic mercury in its fluid form exerts no effect upon the
animal system, it, nevertheless, in a state of vapour, manifests
considerable powers; and it is necessary for the practitioner to be
informed that it assumes this condition at the ordinary temperature of
the atmosphere. I have stated several experiments in proof of this fact
in my work on Medical Jurisprudence, _Art_. “_Aerial Poisons_,” to which
the reader may refer.