Hydrargyrum Cum Creta. Lond. Mercury with Chalk

1 Mercurius alkalizatus, P. L. 1745.

"Take of mercury, three ounces; prepared chalk, five ounces. Rub them together until globules are no longer visible."

Hydrargyrum cum Creta, Dub. Mercury with Chalk.

"It is prepared in the same manner as the mercury with magnesia, only instead of carbonate of magnesia employing precipitated chalk."

In these processes the mercury is oxidized during the trituration, and is left in the state of the binoxide. Mr. Phillips says, that he knows from good authority that a little water greatly facilitates the process.

Medical properties and uses. - It is alterative, and is occasionally prescribed in mesenteric affections, in porrigo, and other cutaneous affections. It merits attention as a mild alterative for children. The dose may be from grs. v. to 3 ss. given twice a day, mixed in any viscid substance.

Hydrargyrum Cum Magnesia. Dub. Mercury with Magnesia

"Take of mercury, manna, of each, two parts; carbonate of magnesia, one part. Triturate the mercury with the manna in an earthen mortar, adding as many drops of water as will give to the mixture the thickness of syrup, and continue the rubbing until the metallic globules completely disappear; then add, still triturating, one eighth part of the carbonate of magnesia; and after the whole is well mixed together, add sixteen parts of hot water, and agitate the mixture. Allow the mixture to remain for some time at rest, in order that the sediment may subside, from which the fluid is to be decanted. Repeat the washing a second and a third time, that the whole of the manna may be removed; and add the remainder of the magnesia to the sediment while it is still moist. Finally, dry the powder upon bibulous paper."

The addition of the manna in this process, and in the for-mer preparation with chalk of the Dublin College, is intended only to facilitate the oxidizement of the mercury, and therefore, it is afterwards removed by the subsequent washings, so that the product is supposed to remain a grey or black oxide of mercury, mixed with magnesia. It is a preparation which might well be rejected.

Hydrargyri Oxydum. Lond.1 Oxide of Mercury

"Take of purified mercury (by weight), three pounds; nitric acid (by weight) a pound and a half; distilled water, two pints. Mix them in a glass vessel, and boil until the mercury be dissolved, and a white mass remain after the evaporation of the water. Rub this into powder, and put it into another vessel, very shallow; then expose it to a gentle heat, and gradually raise the fire until it cease to emit red vapours."

1 Hydrargyrus nitratus ruber, P. L. 1787.

Oxydum Hydrargyri Rubrum Per Acidum Nitricum. Edin. Red Oxide of Mercury by Nitric Acid

"Take of purified mercury, three parts; diluted nitrous acid, four parts. Dissolve the mercury, and evaporate the solution over a gentle fire to a white, dry mass, which, being rubbed to a powder, is to be put into a glass cucurbit, and covered with a thick plate of glass. Then adapt a capital to the vessel; and, having placed it in a sand bath, let the contained matter be roasted with a fire gradually raised until it pass into small very red scales."

Hydrargyri Oxydum nitricum, Dub. Nitric Oxide of Mercury.

"Take of purified mercury, two parts; diluted nitrous acid, three parts. Dissolve the mercury, and let heat be applied until the dried matter be converted into red scales."

Syn. Oxyde Mercure rouge par l' Acide nitrique (F.), Rother Pracipitatat (G.), Mercurio precipitato rosso (I).

In this process, the mercury is first oxidized at the expense of part of the acid employed; and the oxide, which is in a high state of oxidizement, combines with the undecomposed acid, so as to form a nitrate of mercury. By augmenting the heat, this nitrate is decomposed, and also the acid, whilst the oxide is left of a bright red colour, as a binoxide, combined with a small portion of undecomposed nitrate. However simple the process may appear to be, yet it has been always found difficult to produce the bright red scaly appearance, which the product should have when it is properly prepared. Much of the success depends on the purity of the acid; the proper regulation of the heat, which, at the utmost, should not be 600°1; and the scale on which it is formed, the heat being more steadily maintained, and acting with more uniformity, on a large than on a small quantity of materials. On this account, the red precipitate prepared in Holland has always been considered better than any prepared in this country.

The proportions used by the Dutch chemists are fifty pounds of pure mercury, and seventy of pure nitrous acid of a specific gravity 1/3. The decomposition is conducted in very large flat vessels, the fire being raised when the gaseous nitrous fumes cease to be sensibly disengaged; and the test of its perfection is the inflammation of a match which has been just blown out, by introducing it into the vapour arising from the decomposing oxide.1

1 Higgins, Essays, i. 133.

Qualities. - When properly prepared, this is a binoxide mixed with a trace of nitrate of mercury. It is in small scales of a bright red colour, very acrid and corrosive; insoluble in water, but totally soluble in nitric acid without effervescence. It is completely volatilised in a red heat, and at the same time decomposed. We have found the observation of Dr. Murray correct, that " if the preparation be boiled for a short time with five or six times its weight of water, the liquor, when filtered, has the styptic, metallic taste, and gives a white precipitate with water of ammonia or carbonate of potassa; a plain proof that it holds dissolved nitrate of mercury."2 According to Paysse, 100 parts contain 82 of mercury and 18 of oxygen; but according to Mr. Phillips3, the proportions are mercury 92.7, oxygen 7.3, or 1 eq. of mercury = 202, and 2 of oxygen (2x8) =16, making the equivalent 218 (Hg). It is sometimes adulterated with red oxide of lead, which may be detected by dissolving one part of the suspected oxide in four parts of acetic acid: if the oxide of lead be present, the solution has a sweetish taste; and when the oxide is subjected to the flame of a spirit lamp on a piece of charcoal, a button of lead is procured; whilst in its pure state it is perfectly volatilised.

Medical properties and uses. - Nitric oxide of mercury is stimulant and escharotic. It is an external application only, being used, when rubbed into a fine powder, as a stimulant to old sores, and for destroying fungus. As a powder, in the proportion of gr. ss. to grs. iv. of sugar, it is blown into the eye to remove specks on the cornea; and formed into an ointment with lard, it is a useful application to ulcerations of the eyelids, and to chancres.

Officinal preparation. - Unguentum Hydrargyri Nitrico-oxidi, L. E. D.