part hi. Metallic Preparations. — Mercury.

533

approaching to a white, in which state it contains the triplesalt above mentioned. When prepared according to the Lon-don formula, it has been supposed *, that the lime not beingable to abstract the whole of the acid, the product is strictly asubmuriate of mercury. We find, from experiment, thatthis is actually the case, and it is not improbable that a minuteportion of the lime may also be precipitated in the state ofcarbonate. The constituents of the grey oxide are supposedto be 96 parts of mercury, and 4 of oxygen, in 100 parts. 3

Medical properties and uses. — The grey oxide of mercury,when well prepared, may be used as a substitute for the oxideprepared by trituration; and as it is more likely to be alwaysof an uniform strength, it may of course be more depended onthan that preparation. It has been, however, objected to forforming ointment for the purposes of mercurial frictions;(see Ung. Oxydi Hydrargyri cinerei) — but perhaps the objec-tions have originated from that form of the preparation havingbeen used which contains the triple sail. We have seenit used with advantage for fumigation, both locally appliedto assist the healing of venereal ulcers; and, generally, tobring the habit under the influence of mercury, when it couldnot be introduced by the ordinary mode. The dose of thisoxide is from gr. i. togrs. iij. given in the form of pill twicea day.

Officinal preparation. TJnguentum Oxidi Hydrargyri ci/ierei. E.

HYDRARGYRI OXYDUM RUBRUM. Lond. 3 BedOxide of Mercury.

" Take of purified mercury, a pound. Put the mercury intoa glass vessel with a narrow mouth and broad at the bottom.Expose this vessel open to a heat of 600°, until the mercury beconverted into red scales; then rub these to a fine powder."

Oxydvm Hydrargyri. Dub. Oxide of Mercury.

" Take of purified mercury, any quantity. Put it into anopen glass vessel with a narrow mouth and a broader bottom,and expose it to a heat of about 600°, until it be converted intored scales."

In this process the mercury is brought nearly to the boilingpoint 4 , so as to be volatilized, in which state it decomposesatmospherical air attracting its oxygen, and is converted intoa red oxide. A small quantity of mercury requires severalweeks to be thus oxidized; and therefore as much only isintroduced into the vessel as can cover the bottom of it; and

y Murray's System of MuUria Medica, \\. 3*26. z Fourcroy.

i Hydrargyria calcinauis, P. L. 17S7- Oxide de Mercure rouge par le feu (F.)Koihes Quecksilberotfyd [G.) Perosrido rosso dj Merctirio (3.)

* Irvine makes the boiling point of mercury to be 672°; Crichton, 6J5°; andDalron, 660°.

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