These are waters impregnated with the essential oils of vegetables, and
are principally designed as grateful vehicles for the exhibition of more
active remedies; ample directions for preparing them are given in the
several Pharmacopœias, and if they be rectified by redistillation they
may be kept for several years; the usual mode of preserving them is by
adding spirit, which has also the incidental advantage of preventing
them from being frozen during the winter season. Some recommend a film
of the essential oil to be diffused over the water’s surface. They may
be extemporaneously prepared by adding to water what have been called
_Essences_, which consist of essential oil and alcohol, or by rubbing
any essential oil with ten times its weight of sugar, or, what answers
still better, of magnesia: when however they are so prepared they never
retain their transparency. The college, in the present Pharmacopœia,
have directed the distillation off the essential oil, as well as off the
recent herb; this alteration is one of practical convenience. The
properties of each water may be learnt by referring to the vegetable
from which it is distilled.
AQUÆ MINERALES. Mineral Waters.
Although all waters that flow from the earth, are, as they contain
mineral bodies in solution, strictly speaking, _mineral_ waters, yet
this term is conventionally applied to such only as are distinguished
from spring, lake, river, or other water, by a peculiarity in colour,
taste, smell, or any obvious properties, or by the medicinal effects
which they produce, or are known to be capable of producing.
To the medical practitioner the history of these waters is most
interesting and instructive, involving highly important subjects of
chemical and physiological inquiry. These waters are without doubt
indebted for their medicinal virtues to the operation of the substances
which they hold dissolved, but this is so materially aided by the
peculiar state of dilution in which they exist, as well as by the mere
bulk and temperature of the water itself, as to render extremely
doubtful the success of every attempt to concentrate their powers by
evaporation. To what extent dilution may modify the chemical condition
of saline solutions has been satisfactorily demonstrated by the
researches of Dr. Murray (see _Aqua Marina_), and to what degree an
increase in the solubility of any remedy may influence its medicinal
properties has been considered at some length in the first part of this
work, (_page 172_.) It is certain that, in general, soluble salts are
capable of exerting a much more powerful effect upon the animal economy,
than those which are insoluble; on which account, the earthy muriates,
especially that of lime, are amongst the most active ingredients of
mineral waters. Although chemical analysis has frequently from its own
imperfection failed in ascertaining their presence, it seems probable
that _muriate of lime_ and _sulphate of soda_ exist in all those springs
that furnish, by the usual methods of examination, _sulphate of lime_
and _muriate of soda_; for the same reasons it is equally probable that
iron, which in certain waters has been supposed from the analysis to
exist as a _carbonate_, is in its native solution a true _muriate_; this
is undoubtedly the fact with respect to the Bath waters. Is it then
surprising, that medical practitioners should hitherto have failed in
their attempts to emulate, by artificial arrangements, the medical
efficacy of active and mineral springs? For the investigation of the
true composition of mineral waters the researches of Dr. Murray furnish
a simple and elegant formula. _Determine by precipitants the weight of
the acids and bases, suppose them united in such a manner that they
shall form the most soluble salts, and these salts will constitute the
true saline constituents of the water under examination._
Mineral Waters admit of being divided into four classes, viz.
1. ACIDULOUS; owing their properties chiefly to carbonic acid; they are
tonic and diuretic, and in large doses produce a transient exhilaration;
the most celebrated are _Pyrmont_, _Seltzer_, _Spa_, _Carlsbad_, and
_Scarborough_.
2. CHALYBEATE; containing iron in the form of _sulphate_, _carbonate_,
or _muriate_;[391] they have a styptic, inky taste: _Hartfell_ near
_Moffat_, _Peterhead_, _Tunbridge_, _Brighton_, _Cheltenham_, _Bath_,
_Lemington Priors_, _Castle Horneck_, near _Penzance_, &c.
3. SULPHUREOUS WATERS derive their character from sulphuretted hydrogen,
either uncombined, or united with lime, or an alkali: _Engien_, _Aix la
Chapelle_, _Harrowgate_, _Moffat_.
4. SALINE; mostly purgative, and are advantageously employed in those
hypochondriacal and visceral diseases that require continued, and
moderate relaxation of the bowels; _Cheltenham_, _Leamington_,
_Seidlitz_, and all brackish waters.
Some springs, as those of _Bath_, _Matlock_, and _Buxton_, owe their
virtues rather to temperature than to any other cause, and others, as
_Malvern_, to the diluent power of the water.
In the Codex Medicamentarius of Paris, formulæ are introduced for the
preparation of several of the more distinguished mineral waters, under
the head “_Aquæ Minerales Arte Factæ_.”[392]
ARGENTI NITRAS. L. Nitras Argenti. E.D.
_Fused Nitrate of Silver_, olim, _Lunar Caustic_.
QUALITIES. Fused nitrate of silver is in small cylinders of a dark grey
colour, and presenting, when broken across, a crystalline structure.
_Odour_, none; _Taste_, intensely bitter, austere and metallic; it
tinges the skin indelibly black; when perfectly free from copper, it is
not deliquescent. CHEMICAL COMPOSITION; oxide of silver 70, nitric acid
30, or one atom of oxide and one atom of acid. SOLUBILITY. In an equal
weight of water, at 60°; it is also soluble in alcohol. The solution
readily yields transparent colourless crystals, the primary form of
which is a _right rhombic prism_. INCOMPATIBLE SUBSTANCES. _Fixed
alkalies_ and _alkaline earths_, the _muriatic_, _sulphuric_, and
_tartaric_ acids, and all the salts which contain them; _Soaps_,
_arsenic_, _hydro-sulphurets_, _astringent vegetable infusions_,
_undistilled waters_. The solutions of nitrate of silver are not
disturbed by ammonia, the _ammoniuret_ being very soluble; the carbonate
of ammonia, however, produces a precipitation. Nitrate of silver tinges
the skin and hair black, and has been frequently employed for the latter
purpose;[394] it likewise forms the basis of permanent ink.[395]
MEDICINAL USES. Tonic, antispasmodic, and escharotic; it is said to
prove efficacious in epilepsy, but during a trial for several years in
the Westminster hospital, I never could discover its virtues; many of
the cases in which it has been supposed to have been successful,
probably derived advantage from the purgative medicines which were
simultaneously administered. It possesses a bitter taste, and it has
been said to act like vegetable bitters upon the digestive organs, and
to offer a resource in dyspeptic complaints. It is principally useful as
an external application, and may be considered as the strongest and most
manageable caustic that we possess;[396] whilst in solution it acts as a
useful stimulant in indolent ulcers; and being possessed of the power of
coagulating animal matter, it does not spread to any extent, and is
therefore extremely convenient where a large eschar is to be avoided. A
weak solution of this metallic salt has lately been strongly recommended
by a French surgeon, as a remedy for piles of long standing; it also
forms an excellent lotion to excite the weak granulations of fungous
ulcers. It is, moreover, said to be highly useful as an injection in
cases of puriform discharges from the ear; before we direct however such
an application, it is highly necessary that we should ascertain the
tympanum to be entire, or the liquid may escape into the internal ear,
and occasion very alarming irritation; an event which unhappily
occurred, not long since, in the case of a noble duke of high military
renown. FORMS OF EXHIBITION. For internal use, in pills made with crumb
of bread, with the addition of some sugar, to prevent the mass from
being too hard. Dose, gr. 1/8, gradually increased to gr. j.
ADULTERATIONS. _Copper_ may be always suspected when it deliquesces, and
is to be immediately detected by its solution assuming a blue colour,
when supersaturated with ammonia. The sticks should be preserved in
closely stopped phials, and covered with soft and dry paper. ANTIDOTE.
When this substance has been taken in excess, muriate of soda is its
true antidote; indeed, so completely does it decompose, and separate it
from water, that if a saturated solution of nitrate of silver be
filtered through common salt, it may be afterwards drunk with impunity.
This circumstance alone, would of necessity render nitrate of silver a
very uncertain remedy; and yet it is evident that the basis of this salt
is occasionally absorbed, for there are several cases upon record, in
which the oxyd of silver has been deposited in the rete mucosum, and
given a purple hue of a very singular appearance to the patient; I have
lately witnessed an instance of this kind in a lady who had taken large
doses of the nitrate, for the purpose of curing a dyspeptic complaint;
and several other similar cases stand recorded in different works.