Arcanum corallinum, pulvis prin-cipis, panacea merc. rubra, etc.

Pulvis mer-curii cinereus Ph. Ed.

The marine acid has no action on mercury, unless either the mercury be previously dissolved in other acids, or the marine spirit be applied in a very concentrated state and in the form of fume.

Hydrarg. vitriolatus Ph. Lond.

Merc. flav. vulgo turpeth. mine-rale Ph. Ed.

On adding a solution of sea salt to a solution of mercury made in aqua fortis, the nitrous acid quits the mercury, and unites with the alkaline basis of the sea salt; and, at the same time, the acid of the sea salt unites with the mercury, and forms with it a compound difficultly and only partially dissoluble, of which, therefore, great part subsides, on standing for some time, in form of a white powder. This powder, washed with fresh quantities of hot water, till the more soluble parts are extracted, becomes nearly insipid. In this state it is recommended by Boerhaave as one of the belt of the mercurials, and said, in doses of three grains, to purge and vomit gently. It appears however too corrosive for internal use; being so much so, as to be employed by the farriers for the purposes of an escharotic. The preparation is likewise a very unfrugal one, a considerable part of the mercury remaining un-precipitated, and a considerable part of the precipitate being dissolved and carried off in the ablution.

This preparation of mercury, called by M. Scheele, mercurius dulcis made the moist way, is admitted into the new London pharmacopoeia. A solution of half a pound of quick-silver is made in equal its weight of aqua fortis: while boiling hot it is added to a hot brine composed of four ounces of sea salt dissolved in eight pints of water. A white precipitate is thrown down, which, made insipid by repeated washings, is the preparation in question. Its rationale is this. Part of the quicksilver is calcined by the action of the nitrous acid; but part, though dissolved, still retains its phlo-gifton, and is therefore in its proper metallic form. This part, set at liberty by the dereliction of its acid in order to unite with the alkali of the sea salt, joins the freed acid of the sea salt, and with it forms the metallic compound, which being insoluble in water, falls down in form of a precipitate.

Merc. prae-cipitat. alb. Boerhaave. Merc. praec. dulc. Ph. Lond. 1721.

Hydrargyrus muriatus mi-tis Ph. Lond.

If the dry white mass, obtained by infpiffating a solution of mercury in aqua fortis, be powdered and mixed with equal its weight of dried sea salt, the mixture put into a matras or other like vessel, of which it may fill nearly one half, and set in a sand-heat gradually increased; the same transposition of the acids will happen, as in the foregoing case, and nearly all the mercury will now be satiated with the marine acid, and form with it a saline compound, which sub-liming into the upper part of the matras, concretes into a white crystalline mass, called corrosive sublimate. If the vitriolic acid be used instead of the nitrous, that is, if the un-washed turbith be taken and mixed with sea salt, the event will be the same; the mercury subliming with the acid of the sea salt; while the acid, before combined with it, remains behind united with the sea salt's alkali, forming therewith a nitrum cubicum when the nitrous acid has been used, and a sal catharticus when the vitriolic. In like manner, if to four parts of mercury dissolved in as much nitrous acid, and evaporated to dryness, five parts each of calcined sea salt and calcined green vitriol be added, and the mixture submitted to sublima-tion; the same compound will be produced: the acids of the nitre and sea salt are extricated by that of the vitriol: the nitrous acid assists the marine to corrode the mercury: and the mercury, combined with the marine, sublimes, and, if the process is duly conducted, concretes into a crystalline cake, the form in which this compound is expected in the shops. The same preparation is now made in a more simple manner, by boiling together to dryness two parts of quicksilver with as much strong vitriolic acid, then mixing the matter with three parts and a half of sea salt, and subliming with a gradually increased heat.

Mercur. sub-limat. corros. Ph. Ed.

This preparation, undiluted, is a most violent corrosive. A solution of it in lime-water, in the proportion of a dram to a quart, and a stronger solution, made by boiling the same quantity of powdered sublimate, with equal its weight of alum, in a pint of common water, till half the liquor is wafted, are employed for some external purposes, as the cleansing of foul ulcers and suppressing fungosities, and removing obstinate defedations of the skin. The lime-water, like lixivia of fixt alkaline salts, precipitates a part of the mercurial preparation, and hence the impregnation of the liquor cannot be precisely ascertained; for the stronger the lime-water, the more of the sublimate will be precipitated, and the less corrosive will the solution be: at the same time also, the lime in the water, changes its nature, by its coalition with the acid which it absorbs from the sublimate. In the aluminous solution, no sepa-ration happens, both the sublimate and the alum retaining their full force: for on mixing together solutions of the two made separately, no precipitation or turbidness ensued.

Small doses of this corrosive preparation, properly diluted, have been ventured upon internally, Boerhaave relates, that if a grain be dissolved in an ounce of water, and a dram of this solution softened with syrup of violets, taken twice or thrice a day, it will perform wonders in many reputed incurable distempers. VanSwieten brought it into more general use, for the cure of venereal maladies: he dissolves a grain of the sublimate in two ounces of proof spirit, [rectified spirit dissolves it more per-fectly] and gives of this solution from one to two spoonfuls twice a day; continuing the medicine so long as any of the symptoms remain, with a low diet, and plentiful dilution. In the medical observations and inquiries, pub-limed by a society of physicians in London, there are many instances of the success of this method: the sublimate operated chiefly by urine and sweat, though sometimes, for the first two or three days, by stool; and appeared not only safe, but more to be depended on, for the removal of the symptoms, than any of the other mercurials used as alteratives. If it be true, as some have presumed, that the completeness of the cure has any dependence on the quantity of mercury introduced into the blood (a); it would follow, that the cure by sublimate must be less complete than that obtained by any other mercurial preparation, and that those preparations which can be taken without disturbance in con-siderable doses, as five or six grains or more, promise the most lading cures: experience however has now diffidently shewn, that the cures obtained by sublimate are in general perfect.