It is totally volatile in the fire by heat not much greater than that of boiling water, and by a far less heat it is calcined into a red powder. The fumes raised by fire are scarcely visible; and yet, by being received into cold water, may be reduced to the state of pure quicksilver. It rises also in vapour, in the vacuum of the Toricellian tube.

It amalgamates most readily with gold, and in succession with lead, silver, and tin; scarcely at all with iron or copper. By the assistance of trituration, or of heat, it dissolves all metallic bodies except iron.

The vitriolic acid hath no effect upon it until concentrated by heat; the nitrous acid acts quickly upon it; and the muriatic scarcely at all until it is oxidated: fixed salts, vegetable acids, and neutral salts, scarcely alter it in any way. It is allowed to be pure when a little held over a fire, in an iron ladle, totally evaporates.

It is often adulterated with lead; a large quantity of which may be incorporated with it by the intervention of bismuth in a moderate heat; and in this case the lead cannot be separated by pressure through leather. This abuse may be discovered by the mercury staining paper blackish; by its not running into round globules;' by its leaving a powdery matter or a coloured spot on the bottom of the vessel; and by its producing a turbid milkiness during its solution in aqua fortis.

As a medicine, it is used to promote the secretions in general, particularly the saliva. The more perfectly it is divided, the more powerful and penetrating is its action, which is chiefly exerted in the small vessels. Whether used internally or externally it affects all the vessels in our bodies, and may be so managed as to promote excretions through all the emunctories. If not restrained, it is determined to the mouth, and causes inflammation, tumours, ulcerations, and constantly an increased discharge of saliva.

Mercury, like antimony, has been tortured in many different ways, but the result of the chemists' and alchemists' labours has been fortunate. We have obtained by their means a considerable variety of active preparations, which are of the greatest importance in the healing art. We shall, as in the article of Antimony, first examine the preparations retained by the colleges of these kingdoms, and then notice some of the more important formulae formerly recommended, or still valued. The mind will not in this way be distracted by a multitude of objects, and what the enquirer chiefly wants he will readily find.

Mercury is employed

I. Purified by distillation.

Hydrargyrum purificatum (Dublin. London).

II. Slightly oxidated

α By precipitation of nitrated mercury by means" of ammonia. Oxidum hydrargyri cinereum (Ed.). Pulvis hydrargyri cinereus (Dublin). β By trituration.

1. With unctuous substances. Unguentum hydrargyri (Ed.).

------------------------------fortius (Lond. Dublin).

------------------------------mitius, ibid.

Emplastrum ammoniaci cum hydrargyro.

----------------- lithargyri cum hydrargyro.

----------------- hydrargyri (Ed.).

2. With saccharine substances.

Pilulae hydrargyri (Lond. Dub. Ed.). 3. With aerated lime.

Pulvis hydrargyri cum creta. (Lond.).

III

Considerably oxidated α By heat and air.

Hydrargyrum calcinatum (Lond. Dublin. Z 2

β By nitrous acid.

Oxidium hydrargyri rubrum per oxidum nitricum (Edin.). Hydrargyrum subnitratum (Dublin). Hydrargyrus nitratus ruber (Lond.). Unguentum oxidi hydrargyri rubri (Edin.). IV. Oxidated and combined with acids. 1. More slightly. α With the nitrous acid.

Unguentum hydrargyri nitrati (Lond. Dub. Edin.). β With sulphuric acid.

Subsulphas hydrargyri (Edin.). Hydrargyrum subvitriolatum (Dub.). Hydrargyrus vitriolatus (London). y With muriatic acid.

1. Sublimation.

Submurias hydrargyri (Edin.). Hydrargyrum muriatum mite sublimatum

(Dublin). Calomelas (London).

2. By precipitation.

Submurias hydrargyri praecipitatus (Edin.). Hydrargyrum muriatum mite praecipitatum

(Dublin). Hydrargyrus muriatus mitis (London). δ With acetous acid.

Acetis hydrargyri (Edin.). Hydrargyrum acetatum (Lond. Dub.). 2. More completely. Muriats.

Murias hydrargyri (Edin.). Hydrargyrum muriatus (London). Hydrargyrum muriatum corrosivum (Dub.). With ammonia.

Calxhydrargyri alba (London). V., Combined with sulphur. 1. By trituration. Sulphuretum hydrargyri nigrum (Edin.). Hydrargyrum sulphuratum nigrum (London. Dublin). Z. By sublimation.

Hydrargyrum sulphuratum rubrum (London. Dublin). Mercury differs from antimony in one important respect, viz. that its calces are not inert in proportion to their degree of oxidation: in fact, the more highly oxidated metallic salts and calces are among its more active preparations. In the first stage of oxidation we find mercury assume a grey colour; and in this state, as appears by the table, it exists in plasters and ointments, and formerly existed in some other preparations now chiefly confined to private practice. The only remaining preparations of this kind arc, the pulvis hydrargyri cum creta, and the pillule hydrargyri., of the three colleges. The latter differ only in the proportions; for one grain of mercury is contained in four grains of the Edinburgh pill, three in that of London, and two and a half in the Dublin form. It has occasioned some anxiety to learn in these preparations the source of the acid, for an acid was thought necessary. We now find that oxygen is chiefly required; yet it has been discovered that electricity has, or possibly the Galvanic fluid, some share, since the preparation differs according to the nature of the vessels employed. A similar powder is the result of agitating pure quicksilver in water, but the source of the oxygen is there sufficiently obvious.

The difficulty of obtaining a complete extinction of the quicksilver by trituration, induced the Edinburgh and Dublin colleges to precipitate the mercury from its solution in the nitrous acid by means of ammonia. The oxidum hydrargyri cinereum, and pulvis hydrargyri ciniereus, are the results of this plan. The oxide is, however, not pure, for it contains the oxide of mercury with ammonia not saturated with nitric acid. Fourcroy has remarked, that a part of this salt is soluble in the acetous acid; and the remainder, a pure subnitrate of mercury and ammonia, crystallizes in brilliant polyhedral crystals, extremely styptic, and scarcely soluble in water; consisting of 68.2 of oxide, 16 of ammonia, and 15.8 of nitric acid. Though this be different from, the grey oxide, yet we think it deserves a trial. The black oxide may be prepared also by triturating the calomel (in modern language the sublimed submuriate of mercury) in lime water. The decomposition is said to be more complete if the precipitated submuriate is employed; the preparation generally known by the name of calomel in the humid way.