The sal sedativus mercurialis is another modern preparation; not, we suspect, of superior value, since its authors wish to confine it to external use. The nitrated mercury is precipitated by a solution of borax; and the salt, which is at first yellow, by the access of air becomes greenish. It is scarcely soluble in watery fluids, and when sublimed is of an orange colour. Journal dc Physique, ix. 343. x. 411.

The union of mercury with the benzoic acid (mercurius benzoinus) was first mentioned, we believe, by Tromsdorf in his Chemical Annals for 1790. The flowers of Benjamin, dissolved in water, are employed to precipitate nitrated mercury. The salt is of a brown colour; but, carefully washed and dried, is white and shining, unchanged in the air, with difficulty dissolved in water, somewhat more readily in spirit of wine. It is with some regret we add, that, except its author, the only authority we can find for its having been advantageously employed is the suspicious one of M. Mittie.

The mercurial salts offer some facts and preparations of curiosity, if not of importance. Lavoisier and Cornette, in the Memoirs of Medicine, have informed us that the mild alkalis will dissolve the calces of mercury; and Quercctanus long since described the preparation of a spiiritus mercurialis, which consisted of an alkaline solution of mercury; and Rit-ter speaks with commendation of an essentia mercurii, which contained the metal, joined with a caustic alkali. The neutral salts, however, have a greater power, and the most active of these is the muriated ammonia. The mercurial tincture of Garaye is prepared by triturating the dry sal ammoniac with mercury, suffering it to deliquesce, then again drying, and repeatedly triturating, deliquescing, and drying it. The process is shortened by triturating the brown or the red precipitate with the salt, and then subliming it.

Monnet and Paecken long since informed us, that mercury triturated with cream of tartar would be completely united with it; and if some syrup was added, the union would be so complete, that the addition of powders capable of absorbing the moisture would not affect it. Cream of tartar, though it does not dissolve the metal in its shining state, will dissolve its calces; and we once saw salivation induced, by digesting in cold water AEthiops mineral, sulphur, and cream of tartar, and giving the solution. If a little borax or sedative salt is added, the union will be more complete. This preparation, called mercurius, and sometimes AEthiops tartarisatus, and dissolved in water, the eau vegetable mercurielle, is considered as a very useful medicine, but it seems to have no claim to any extraordinary powers. The pure acid of tartar, as we are informed by Meyer and De Morveau, dissolves the mercury more readily, and in a larger proportion.

Rhenish wine, cyder, verjuice, and vinegar, have been employed as solvents of mercury. The liqueur fondante of Diennert, the hydrargyrum acetatum, and the terra foliata mercuria/is-of Defourcy, are preparations of this kind; but the acid dissolves only the calces of mercury, and the preparations differ in activity according to the calx employed.

We find, in the works of foreign surgeons, very caustic topical remedies resulting from the union of mercury with the nitrous acid. Of this kind are the liquor exfoliatus Bellostii, liquor mercurii vivi of Mynsicht, and the aqua grisea of the Wirtemburg Pharmacopoeia. The mercurius nitrosus of Selle forms white crystals, prepared by dissolving mercury in the nitrous acid. These are dissolved in four times their weight of water, and two drops of the solution are given morning and evening.

The muriated mercury is the foundation of the different mercurial waters employed externally. Hor-stius's aqua mercurialis pro scabiosis contains equal parts of corrosive sublimate and euphorbium, with a larger proportion of arsenic than his menstruum will dissolve. Grunlingius's linimentum ad serpiginem consists of sublimate and alum, of each half a dram, and an ounce of gum tragacanth, dissolved in plantain water. We may here remark that alum is often useful in itch, and is an active ingredient in many of the secret remedies which profess to cure it in a very short time. Zwelfer adds to his aqua mercurialis a portion of aloes for venereal ulcers and cutaneous eruptions; and Jung-ken, in a similar water, adds ceruse, alum, nitre, sal ammoniac, vinegar of litharge, etc. A preparation nearly of the same kind occurs in the Wirtemburg Pharmacopoeia, which was, for many years, the standard pharmaceutical work of Germany; but, more scientifically combined, Vogler's liquor mundificans contains the sublimate, with dock root, brown flowers, the leaver of juniper and savine, and the root of the acorus calamus. The most singular external preparation of this is the oil of mercury, for warts and corns, of Fausius; an equal quantity of candied sugar and of sublimate, with a very small proportion of filings of iron, are exposed first to a gentle and then a violent heat in close-vessels. The iron, however, in part, decomposes the muriated mercury.

Such are the most curious or important preparations of mercury, not admitted into our pharmacopoeias; but we cannot conclude this account of external mercurial applications, without guarding the more inexperienced practitioner from too free and indiscriminate employment of them. The records of medicine are full of the most dreadful instances of death, in its most painful shape, following their use; and, though the subject led us to enumerate and explain the principles of their several combinations, we have carefully avoided those particulars which would lead, on the one hand, to rash empiricism, or add to the already too numerous list of quack medicines.

As a medicine, there is scarcely an indication that mercury cannot supply. There is no more certain and active emetic than the mercurius vitriolatus; a more powerful laxative than the calomel; a more effectual and steady diaphoretic and stimulant than the mercurius muriatus; a more certain emmenagogue than calomel; a more effective errhine than the turpeth mineral; a more infallible sialogogue than either of its preparations. If we look at the principle by which these different changes are effected, we shall find it to be a steady and permanent stimulus. When applied to the extremities of the excretory ducts, it excites the action of the various glands; when, on the contrary, it is determined from the mass of blood, to the first branches of the glandular system, it is equally powerful. When no glandular system intervenes, it excites the action of the extreme vessels over the whole body.