Hydrargyrus muriatus Ph. Lond.

Aq. phage daen.

Aq. alumi.-nosa.

Corrosive sublimate consists of mercury, united with so much marine acid, as to be dissoluble in boiling water. If by separating a part of the acid, or adding more mercury, the proportion of acid is rendered so small, as that no part of the compound shall be dissoluble, when finely powdered, by long boiling in water; its corrosiveness will be destroyed, and it may now be taken with safety in doses of some grains. A little volatile spirit or alkaline lye, dropt into the water after the boiling, will discover if it has taken up any part of the mercury, by turning it cloudy or yellow: rain, snow, or rather distilled water, should be employed for this trial, as the common spring waters are themselves made cloudy by alkalies. Spirit of sal ammoniac, or other volatile alkalies, dropt into a filtered solution of sub-limate, absorb a part of the acid; and the mercury, retaining so little as to be indissoluble, renders the liquor milky, and subsides, on (landing, in form of a fine white powder, which, washed by repeated affusions of hot water, becomes insipid. Solutions of fixt alkaline salts, substituted to the volatile spirit, produce a yellow precipitation: but if an equal weight of crude sal ammoniac be dissolved along with the sublimate, fixt alkalies, added to this solution, extricate the volatile alkali of the sal ammoniac, and the precipitate proves the same, as if the volatile alkali alone had been added in its pure state. These precipitates are used chiefly on account of the elegance of their colour, in unguents for cutaneous eruptions: one part of the mercurial precipitate, and eighteen of the simple ointment or pomatum, make the common mercurial application for these complaints. The precipitates have been given internally; but mercurius dulcis, which differs from them only in being more mild, and more equal and certain in its effects, is in this intention greatly to be preferred. It does not appear, that a combination of mercury with so small a proportion of acid, that is, so mild and safe a mercurial, can be obtained by any kind of of precipitation, as by the process by which mercurius dulcis is prepared.

(a) Aftruc, De morbis veneris, tom. i. lib. ii. cap. 12.

Merc. prae-cipit. albus Ph. Ed.

Calx hy-drarg. alba Ph. Lond.

Unguent. calcis hy-drarg. alb. Ph. Lond.

Mercurius dulcis is sublimate made mild, by combining with it so much fresh mercury, as is sufficient to satiate the redundant acid. Four parts of powdered sublimate are ground with three, or three and a half of quicksilver (an operation in which great caution is necessary, to avoid the lighter corrosive particles that fly off) till they are thoroughly incorporated; or, which is much more commodious, digested together in a gentle heat, by which the union will be performed as effectually. The mixture is then sublimed in a glass matras or phial; the subli-med white mass freed from the whitish acrid matter about the mouth of the vessel, and from such mercurial globules as may happen to appear distinct, then pulverized, and sublimed again: the college of Edinburgh directs the su-blimation to be repeated three or four times, that of London four times. By repeated subli-mations, if a sufficient quantity of mercury has not been united at first, the medicine becomes less liable to irritate the first passages and run off by stool; on account of some small part of the acid, or some portion of the compound not fully dulcified in the first operation, being sepa-rated or dissipated by the heat. The dulcifica-tion depends solely on the combination of so much fresh mercury with the sublimate, as may fully satiate the acid: the union of the two is effected by the digestion previous to the subli-mation: and the only use of the sublimation it-self is to separate such part as may remain un-dulcified, this part being the most volatile.

Mercurius dulcis appears to be the best and safest of the mercurial preparations that can be taken in a solid form, whether as a fialagogue or as a general alterant; no one or the mercurials, whose transmission into the blood can be depended on, being so little disposed to affect the first passages. As a fialagogue, five, ten, and sometimes fifteen grains, made into a bolus or pills, are repeated every night or oftener, till the ptyalism begins. As an alterative, it is given from one to two or three grains. It generally answers best in small doses, which may be repeated, with due caution, every evening, for a considerable time, without inconvenience.

Calomelas Ph. Lond.

Merc. dulcis Ph. Ed. Aquila alba.

Mercury, precipitated from aqua fortis by fixt alkali, dissolves totally, by the assistance of heat, in distilled vinegar: on cooling, the salt crystallizes into fine brilliant plates, which float in the liquor like pieces of silver leaf, and are very difficult of solution in water. This salt, as appears from the experiments of Hellot and Others (a), is the basis of an antivenereal medicine which has lately come into great repute abroad, but which does not seem, from the accounts that have been published of it, to be either more safe, or more effectual, than some of the common officinal mercurials. * A salt of this kind, made by dissolving the mercurial precipitate in the concentrated acetous acid procured by distilling verdigris, is received into the late edition of the London pharmacopoeia.

In some obstinate defedations of the skin, mercurials and antimonials, joined together, have frequently better effects than either of them unaffifted by the other. Some triturate quicksilver with twice its weight of crude antimony, till the mercurial globules disappear, and the mixture becomes an uniform aethiops or black powder: others, instead of the crude antimony, use the medicinal regulus, or the golden or precipitated sulphur; and thus obtain an aethiops of more activity. The college of Edinburgh has given a prescription of pills on this principle, composed of three parts of quicksilver, two parts each of golden sulphur of antimony, gum guaiacum and honey, and so much mucilage of gum-arabic as will reduce them into a mass of a due consistence: if a dram of the mass is made into twenty pills, the dole may be increased from one to six or more, according to the operation.

(a) Memoires de l'acad. roy. des sciences de Paris, 1759.

Keyser's pills.

Hydrarg. acetatus Ph. Lond.

aethiops antimonialis.

Some of the mercurial preparations have been said to be oftentimes sophisticated; the cinnabar and red corrosive with red lead, the corrosive sublimate and mercurius dulcis with arsenic. The red lead may be readily discovered by fire; the mercurial part evaporating, while the satur-nine remains behind. With regard to the other abuse, some have affirmed it to be impracticable (a); for if arsenic be mixed with sub-limate, and the mixture set to sublime, the marine acid quits the mercury, and unites with the arsenic; with which it composes, not a solid crystalline, but a soft butyraceous concrete, called by the chemists butter of arsenic. If arsenic should nevertheless, in certain circum-stancess (b), be combinable with the sublimate into a crystalline cake; and if the pernicious artifice should be ever practised, the reports of which we presume to be groundless; the well known properties of arsenic afford sufficient means for detecting it. If a compound of sub-limate and arsenic be mixed with equal its weight or more of fixt alkaline salt, chalk, or vegetable ashes, and exposed to a moderate heat, the arsenic will sublime into the upper part of the glass, and may now be distinguished by its own proper characters. Some recommend alkaline lixivia as a criterion of this abuse: sublimate that contains arsenic being said to give a black colour with the alkali: on what foundation this should happen, I cannot conjecture; for arsenic strikes no blackness with alkalies either fixt or volatile; solutions of it are, on the contrary, by both alkalies made white.

(a) Neumann, Chemical works, p. 142.

(b) Pott. De sale communi, p. 76.

Pil. aethi-opicae Ph. Ed.