Hydrargyrus Pharm. Lond. Hydrar-gyrus, Argentum vivum, Mercurius, Pharm. Edinb. Mercury or quicksilver: an opake silver-coloured metallic fluid, appearing to the eye like melted lead or tin; about fourteen times heavier than an equal bulk of water; not congealable by the greatest known degree of natural cold (a); totally exhaling, by a heat below ignition, in subtile fumes, which condense into running mercury again.

Pilula lunaris.

Quicksilver is sometimes found in the earth in its fluid form, and is then called virgin mercury; but for the moil part it is intimately blended with sulphur or earthy matters into a state of ore. The sulphureous ores are of a more or less beautiful red colour; the earthy or stony ones, grey, yellowish, brown, leaden coloured, etc. From these last, the metallic fluid is extracted by simple distillation: the sulphureous require an addition of quicklime, iron filings, or some other substance that may absorb and keep down the sulphur, which other-wife would rife in conjunction with the mercury. The principal mines of quicksilver, of which we have any account, are in Spain, Hungary, and the province of Friuli in the Venetian territories: considerable quantities are brought also from the East Indies.

This fluid, supposed by the Greeks to be poisonous and corrosive, was introduced into medicine by the Arabians, as an ingredient in external applications, against different cutaneous maladies. This practice was followed by some physicians in Europe towards the end of the thirteenth century, but was not established, or looked upon in general to be safe, till about the beginning of the sixteenth, when the venereal distemper, then lately received from America, was found to yield to mercurial applications alone; and now also the internal use of mercury began to be ventured on, in this and in other diseases.

(a) If is said, that in some late experiments made at Petersburg, with very intense degrees of artificial cold, (produced by mixing snow and spirit of nitre separately brought to great coldness,) pure mercury congealed into a silver-like malleable metal, which quickly melted again on an abatement of the cold; and that in Fahrenheit's thermometer, it funk, before its congelation, to between three and four hundred divisions below o; that is, about as far below the point at which water freezes, as the heat, in which tin melts, is above it.

Pure mercury has no perceptible acrimony, or taste, or smell: there are examples of its having been lodged, for years, in cavities both of the bones and of the fleshy parts, without having injured or affected them (a). . Taken into the stomach in the quantity of an ounce or two, it soon paries through the intestinal tube, unchanged, and unfelt: hence some have been induced to give a pound or more in violent constipations, hoping that this innocent fluid, by its great weight and flipperiness, would force open obstructions, that had resisted the common methods of cure by purgatives, relaxants, and emollients. This practice, so far as I can learn, has not been attended with any remarkable success; nor do the principles, on which mercury has been given in these cases, appear to be just. The flipperiness of this fluid con-Ms only in the mobility of its own parts, not in any power by which it can lubricate the vessels of an animal. Its weight can be of no use, unless where the obstruction lies in some descending part of the tube: and even sup-posing it to act perpendicularly, to the greatest advantage, there is room to fear, that the pres-sure of a pound or two will rather distend the superiour part of the intestine, than be able to force a passage through the obstinate obstruc-tions against which it is recommended.

(a) Mead, Mechanical account of poisons, essay iv.

When mercury is resolved into fume, or altered in its form by fire, or combined with a small portion of mineral acids, or otherwise divided into minute particles and prevented from reuniting by the interposition of proper substances; it operates with great power, and extends its action through the whole habit. In these forms, whether taken internally, or introduced into the blood from external application, it seems to liquefy all the juices of the body, and may be so managed as to promote excretion through all the emunctories. If its power is not restrained, or determined by additions, it tends chiefly to affect the mouth; and having fused the humours in the remoter vessels, occa-sions a plentiful evacuation of them from the salival glands, with considerable swellings, inflammations, and ulcerations of the parts. The salivation is accompanied with a diminution of moil of the other discharges, and an increase of these diminishes the salival flux.

The salutary effects of mercurials have, in many cases, very little dependence on the quantity of sensible evacuation. Venereal maladies, and chronical distempers proceeding from a viscidity of the humours and obstruction of the small vessels, are often successfully cured by mercurials taken in such doses as not to produce any remarkable discharge; especially if assisted by diaphoretics and a warm diluent regimen. In this view, camphor, and the resin or extract of guaiacum, are frequently joined to the mercury; and to the more active preparations, a little opium; which not only promotes the diaphoresis, but prevents the mercury from irritating the first passages and running off by the grosser emunctories.

This appears to be, in general, the mod advantageous method of using mercurials; excepting, perhaps, only in venereal maladies of long standing, or such as have arisen to a great height, or have affected the bones; which demand, for the most part, a full ptyalism. In these cases, the disease has been subdued for a time by the alterative method; but afterwards broken out afresh, and been completely cured by salivation: and, on the other hand, some cutaneous soulnesses, after refitting salivation, have yielded to an alterative course.