vulgo. _Calomel_.[529]
This preparation has been known in pharmacy for upwards of two centuries
under a variety of fanciful names, such as _Draco mitigatus_; _Aquila
alba_; _Aquila mitigata_; _Manna metallorum_; _Panchymagogum minerale_;
_Panchymagogus quercetanus_; _Sublimatum dulce_; _Mercurius dulcis
sublimatus_; _Calomelas_; and yet there is not a name in this list that
is so objectionable as the one at present adopted by our colleges: for
whether we adhere to the theory of muriatic acid being the _simple_
body, or accede to the new views of _chlorine_, the name is equally
inappropriate; if we regard it as a compound of muriatic acid and oxyd
of mercury, it is not a _sub_-muriate, but as much a _muriate_ as the
corrosive sublimate; the only difference depending upon the degree of
oxidizement of the mercury, which is at a _minimum_ in calomel, and at a
_maximum_ in sublimate. According to the new views respecting chlorine,
calomel must consist of one proportional of chlorine with one
proportional of metal, and is therefore a _chloride of mercury_.
(“_Proto-chloruretum Hydrargyri._” Codex Med. Paris.)
QUALITIES. _Form._ A semi-transparent mass, consisting of short
prismatic crystals;[530] inodorous, insipid, and of an ivory colour,
which deepens by exposure to light. SOLUBILITY. It is considered as
being insoluble, since according to Rouelle, one part requires 1152 of
water, at 212° for its solution. INCOMPATIBLE SUBSTANCES. _Alkalies_ and
_lime water_ decompose it and turn it black, in consequence of
precipitating the black oxyd of the metal; it is also decomposed by
_soaps_, _sulphurets of potass and antimony_; and by _iron_, _lead_, and
_copper_; hence it is improper to employ any metallic mortar for
dispensing medicines which contain it. There seems to be reason for
supposing that this preparation may undergo decomposition _in transitu_,
and that therefore some substances may be _chemically_, and yet not be
_medicinally_ incompatible with it. If calomel be boiled for a few
minutes in distilled water to which alcoholized potass has been added,
it is completely decomposed, a _muriate of potass_ and _black oxyd of
mercury_ being the new products. Calomel is not affected by sulphuric
acid in the cold, but, at a boiling temperature, corrosive sublimate,
and deuto-sulphate of mercury are formed. MEDICINAL USES.[531] This
mercurial preparation is more extensively and more usefully employed
than almost any other article of the materia medica. It is capable of
curing syphilis in every form, provided it does not run off by the
bowels; and in obstructions and hepatic affections, it is in
well-regulated doses a most valuable remedy; in combination, it probably
merits the appellation of _Dirigens_, more decidedly than any other
remedy with which we are acquainted, for when combined with certain
diuretics, it is diuretic, (_Form. 103, 104_) and in diaphoretic
arrangements, it is diaphoretic: it moreover imparts force to many of
the mild, and moderates the severity of drastic medicines: whenever we
wish a strong and permanent impression to be made on the alimentary
canal, and through it on the neighbouring viscera or the system
generally, Calomel by universal consent is adopted for such a purpose.
(_Form. 81, 88, 119, 161._) In larger doses it is one of the most
efficient purgatives which we possess, especially when in combination
with other cathartics: it appears to be particularly eligible in the
diseases of children; and it is singular that infants can generally bear
larger doses of it than adults. DOSE, as an alterative, from gr. ss to
j, night and morning; as a purgative, from gr. ij to gr. x, or in some
cases even to gr. xv, or ℈j. FORMS OF EXHIBITION. That of pill; its
insolubility and specific gravity render any other form ineligible.
OFFICINAL PREPARATIONS. _Pil. Hydrargyri submuriat. comp:_ L.
IMPURITIES. _Corrosive sublimate_ may be detected by precipitation being
produced, by the carbonate of potass, in a solution made by boiling the
suspected sample with a small portion of muriate of ammonia, in
distilled water; calomel ought also, when rubbed with a fixed alkali, to
become intensely black, and not to exhibit any trace of an orange hue.
HOWARD’S OR JEWEL’S _Hydro-sublimate_. Instead of subliming so as to
obtain the calomel in a concrete state, as directed by the Pharmacopœia,
the salt in the act of sublimation is exposed to aqueous vapour, and
received in water. Being in a state of very minute division, it is
lighter than common calomel in the proportion of three to five, and it
cannot contain any corrosive sublimate. The French in their late _codex_
have introduced a similar formula, under the title of “Murias Mercurii
dulcis mediante aqua subtilissime divisus, _juxta Methodum Josiæ
Jewel_.”
This _Patent Calomel_ of Howard is undoubtedly to be preferred, and
appears, in consequence probably of its minute division, to affect the
system more readily than that made according to the Pharmacopœias.
SUB-MURIAS HYDRARGYRI PRÆCIPITATUS. E.D. This is produced by
precipitating a nitrate of mercury by muriate of soda; the preparation
will generally contain a small portion of _sub-nitrate_, and it is on
that account more liable to run off by the bowels in small doses: in
other respects it is essentially the same as that procured by
sublimation.