(Hg. Eq.=100.) Hydrargyrum. Mercury; Quicksilver.

Prep. Mercury is obtained chiefly from its sulphuret, native cinnabar, by distillation with iron; sometimes it is met with in its metallic state, sometimes combined with chlorine, etc. Mercury of Commerce, Appendix A, is ordered to be purified by redistillation and washing with dilute hydrochloric acid.

Prop. & Comp. When pure, mercury occurs as a brilliant white metallic liquid, becoming solid at -39° Fah.; sp. gr. 13.5; entirely vaporized by heat; and when small globules of it are rolled slowly upon a sheet of paper, not the least particle adheres; above 40° Fah. a slight vapour arises from it. It forms two classes of salts, proto- and persalts. It dissolves many metals, as tin, bismuth, zinc, silver, and gold, and forms amalgams with them.

Off. Prep. Liquid mercury is seldom used in medicine, but there are many preparations which owe their value to the presence of mercury in a very highly divided state, caused by long trituration with saccharine and greasy matters, or fine powders.

Hydrargyrum cum Creta. Mercury with Chalk. (Mercury, one ounce; prepared chalk, two ounces. [Mercury, three ounces; prepared chalk, five ounces. U. S.] Rub together until globules are no longer visible.)

Pilula Hydrargyri. Mercurial Pill. (Mercury, two ounces; confection of roses, three ounces; powdered liquorice root, one ounce. Rub the mercury with the confection until globules can no longer be seen; then, the liquorice being added, beat the whole together to form a mass.)

Emplastrum Hydrargyri. Mercurial Plaster. (Mercury, three ounces; olive oil, one fluid ounce; resin, one ounce; litharge plaster, six ounces. Melt the oil and resin, rub the mercury till globules disappear, then add the litharge plaster, previously liquified.)

Emplastrum Ammoniaci cum Hydrargyro. Ammoniac and Mercury Plaster. (Gum ammoniac, twelve ounces; mercury, three ounces; olive oil, one fluid drachm; sulphur, eight grains.)

Unguentum Hydrargyri. Mercurial Ointment. (Mercury, one pound; prepared lard, one pound; prepared suet, one ounce. [Mercury, twenty-four ounces; lard, suet, each twelve ounces. U. S.] Rubbed together thoroughly.)

Linimentum Hydrargyri. Liniment of Mercury. [Not officinal in U. S. P.] (Ointment of mercury, one ounce; solution of ammonia, and liniment of camphor, each one fluid ounce.)

Therapeutics. Liquid mercury, when taken into the stomach, appears to possess no action on the economy, and very large quantities, even pounds, have at times been swallowed without any particular symptoms being produced; now and then, however, the full effects of the metal have ensued, probably owing to partial oxidation and absorption. The vapour of mercury acts with great energy, as seen in the effects on artificers exposed to its influence; the same results may be produced by rubbing mercury in a very highly divided state upon the surface of the body, or taking it internally in a state of minute subdivision. Given in small doses, the first effects of mercurials are observed in the increase of various secretions; and hence sialagogue, cholagogue, diuretic, emmen-agogue, and other properties have been ascribed to this mineral. Its sialagogue power is shown in the increase of the salivary fluid, and mucous secretions of the mouth, together with a peculiar condition of the gums and neighbouring parts; and as these are amongst the first, most constant, and most peculiar of the effects of mercurials, they are generally taken as guides during the administration of the drug, as to the propriety of increasing or .diminish-ing the dose. The sialagogue effects are seldom desired for themselves.

The cholagogue and purgative action of mercurials is exhibited in the increase of the colouring matter and other principles of the bile in the evacuations from the bowels, which are at the same time more liquid in character from an excessive secretion from various other secreting glands, as the pancreas, and mucous membrane of the intestinal canal. The secretions of the kidneys are not unfrequently augmented, also the action of the skin, and occasionally the catamenial discharge; it seems probable, however, that many of these latter effects are not so much due to the direct action of the remedy on the secreting organs, as to the relief of certain morbid conditions of the system, which had given rise to the imperfect performance of these functions. Mercurials cause also the absorption of morbid fluids, either from increasing the activity of the absorbent system, or preventing deposition. In whatever way mercury is administered it becomes absorbed into the blood, where it has been detected; and its presence has also been demonstrated in the milk, urine, saliva, sweat, bile, pus from ulcers; and in the various tissues of the body, as the bones, brain, serous and synovial membranes, cellular tissue, and lungs. Its action on the blood is not well made out; it diminishes the amount of globules, and has some influence on the quantity and quality of the fibrine. Mercurials are employed in the treatment of various diseases, among which the following are the most important.

In internal congestions, as of the liver, kidneys, etc.; to increase secretions, and hence relieve the vessels of the parts.

Acute inflammation of any part is often found to give way when the system is brought under the influence of mercury, probably from its power of increasing the secretions of the part, influencing the capillary circulation, and altering the condition of the blood; sthenic inflammations, with effusions of plastic lymph, are more controlled by the drug than those of an asthenic kind; serous membranes are more influenced than mucous membranes, and the parenchyma of the liver more than that of the lungs. In chronic inflammations mercurials often prove useful in removing the morbid products, such as induration, and fibrinous and other effusions.

Mercury is injurious in erythematous and scrofulous inflammations, and also in any of a low type.

In acute rheumatism mercurials are much employed by some practitioners; it is questionable whether they influence the duration of the disease, but they are generally considered to be useful in the peri- or endo-carditis, which is so frequently present.

In dropsies dependent on inflammation of serous membranes and hepatic disease mercurials are useful, but injurious when arising from granular disease of the kidneys.

In idiopathic fevers mercurials are often useful in keeping up the action of secreting organs and relieving congestions, but they appear to have no influence on the duration of the fever itself.

In syphilis mercurials at one time formed the sole remedy; at the present time they are not considered essential to the cure of the affection, although employed in moderate quantities, both for the primary and secondary forms of the disease: it is probable that the terrible sequences of syphilis, formerly so commonly met with, were often as much dependent on the drug as on the disease itself.

Mercury is very commonly used as an alterative in chronic affections of almost every part of the system, and as a cholagogue purgative in cases of dyspepsia, etc, where the secretion of the liver is defective.

Externally employed, in the form of ointment, etc, mercurials produce a topical stimulant action, causing exalted action of the capillaries; they also become absorbed, and affect the system generally. They are used over indurated and chronically inflamed parts, and sometimes to introduce the mineral into the system.

Effects of over-doses, or the too great action of Mercurials.

Very profuse pytalism, swelling of the tongue and salivary glands, and the whole face, tumefaction and redness of the gums, ulceration of different parts of the mucous membrane of the mouth, loosening of the teeth, and even necrosis of the jaw. Occasionally the flow of saliva and buccal mucus amounts to some pints in the day.

Excessive purging, with very bilious stools.

Certain skin affections, as Eczema Mercuriale.

Inflammation of the periosteum and bone, of parts not connected with the mouth.

A low, febrile condition (mercurial erythism), accompanied with intense prostration of the vital powers.

Affections of the nervous system, such as neuralgic pains, partial paralysis (tremor mercurialis), and sometimes complete paralysis, and death; these symptoms are usually observed in those who are subject to the action of mercurial vapours.

Circumstances influencing the operation of Mercurials.

The age of the patient has great influence; children are much less affected than adults; still, care should be used in administering mercurials to young subjects, as very injurious results sometimes ensue.

Certain individuals appear to be able to resist completely the action of mercurials, others to be very susceptible of their influence; often such idiosyncrasies cannot be explained, but at times they depend on a diseased condition of the system.

The presence of acute sthenic inflammation gives a resisting power to the action of the mercurial preparations, whereas granular disease of the kidney, scrofula, and scorbutus, render the system very sensitive to mercury, and the drug should generally be avoided in such cases.

Dose. Of hydrargyrum cum creta, 5 gr. to 15 gr.; of pilula hydrargyri, 3 gr. to 10 gr.

The unguentum hydrargyri may be rubbed into a part where the skin is thin, as in the arm-pit or inner side of the thigh, in quantities varying from 30 gr. to 120 gr. The inunction should be continued till absorption has taken place.

Adulteration. Other metals, as lead, tin, zinc, and bismuth, are often found in a state of amalgamation with mercury, or dissolved in it: when such are present, the small globules leave a trail when rolled along a sheet of paper: zinc and tin are soluble in the hydrochloric acid, and lead and bismuth would not volatilize, and so could be detected: the process of purification by means of distillation and hydrochloric acid removes these impurities.