688

Metallic Preparation*. — Mercury. part hi.

portions of the Edinburgh formula ai - e productive of a very un-necessary waste of acid.

Qualities. — Subsulphate of mercury is inodorous, andacrid to the taste. It is obtained in the form of a beautifulbright yellow powder, of a specific gravity of 6*444, and nearlyinsoluble in water, requiring 2000 parts at 60°, and 600 at 212°,for its solution, which is colourless. By trituration with mer-cury it is changed into the black oxide; and at a red heat isdecomposed, the oxygen being given out and the metal reduced.According to the analysis of Braumcamp and Segueira, itsconstituents are 84*7 parts of oxide of mercury, 15 of sulphuricacid, and three of water 1 ; while Fourcroy makes them 87 ofoxide, 10 of acid, and three of water.

Medical properties and uses. — This preparation is emetic,discutient, alterative, and errhine; but from the violence of itsaction it is seldom administered as an internal remedy. As anerrhine, however, it has been found extremely useful in chi'onicophthalmia, and diseases of the head; but even for this purposeits acrimony requires to be sheathed with some bland powder,as starch, or liquorice root powder, in the proportion of grs. t.to gr. j. of the subsulphate. In doses of gr. v. it operates as avery powerful emetic.

HYDRARGYRUM CUM CRETA, Lond. Mercmywith Chalk. °

" Take of purified mercury, three ounces; prepared chalk,

Jive ounces. Rub them together until the globules disappear."

Hydrargyrum cum Creta, Dub. Mercury "with Chalk.

" It is prepared in the same manner as the mercury with

magnesia, only instead of magnesia employing precipitated

chalk."

In these processes the mercury is slightly oxidized duringthe trituration, and is in the state of the black oxide, 100 partsof which, according to Fourcroy, contain, when, well prepared,about 4 of oxygen.

Medical properties and uses. — It is alterative, and is occa-sionally prescribed in tinea capitis, and other cutaneous affec-tions. It merits attention as a mild alterative for children.The dose may be from grs. v. to gss. given twice a day, mixedin any viscid substance.

HYDRARGYRUM CUM MAGNESIA, Dub. Mer-cury inith Magnesia.

" Take of mercury, manna, of each an ounce; magnesia,half an ounce. Triturate the mercury with the manna in anearthen mortar, adding as many drops of water as will give tothe mixture the thickness of syrup, and continue the rubbinguntil the metallic globules completely disappear; then add,

1 Annates de Chimie, liv. 123.2 Mercurim alkalizatus, P. L, 1745.