Hydrargyri Cyanuretum. Dub. Cyanuret of Mercury

"Take of cyanuret of iron, six parts; nitric oxide of mercury, five parts; distilled water, forty parts. Mix together the cyanuret of iron and the oxide of mercury, then add the water heated. Boil the mixture for half an hour, constantly agitating it, and filter through bibulous paper. Wash the residue with hot distilled water. Finally, evaporate the liquor, so that, when filtered and cooled, crystals may form."

Qualities.-The bicyanide of mercury is a nearly colourless salt, crystallizing in quadrilateral prisms. It has an acrid, metallic taste; is soluble in water at 60°, and more so at 212° : but scarcely soluble in alcohol. It is soluble in nitric acid without decomposition : but it is decomposed by heat, sulphuric acid; with hydrochloric acid hydrocyanic acid is evolved, and bichloride of mercury formed. It is also decomposed by sulphuretted hydrogen, and the hydrosulphates. Bicyanide of mercury is a compound of 2 eq. of cyanogen = 52.78 + 1 of mercury = 202, making the equivalent 254.78 or 20.4 of cyanogen + 79.6 of mercury in 100 parts (Hg. Cy.)

Medical properties and uses. - This salt is employed in the same diseases, and in similar doses, as the bichloride of mercury. It is also employed for the preparation of hydrocyanic acid.

Officinal preparation. -Acidum Hydrocyanicum, L.

Hydrargyri Iodidum. Lond. Iodide of Mercury

"Take of mercury, an ounce; iodine, five drachms; alcohol, as much as may be sufficient. Rub together the mercury and the iodine, adding gradually the alcohol, until no more globules are visible. Dry immediately the powder in a gentle heat, excluded from the light, and preserve it in a well stopped vessel."

An immediate union takes place between the mercury and the iodine, and a greenish yellow powder is formed, which sublimes by heat undecomposed, in the form of red scales, which acquire an orange yellow colour in cooling. It is insoluble in water, and only partially so in alcohol: but it is soluble in aether. Light decomposes and blackens it; but it is less liable to decomposition when it has been sublimed. It is a compound of 1 eq. of iodine = 126.3+ 1 of mercury = 202, making the equivalent =328.3 (Hg I.) or of 55.5 of iodine + 44.5 of mercury in 100 parts.

Medical properties and uses.- This iodide possesses alterative and stimulant properties, similar to those of the other mercurial salts. It was first introduced as a therapeutical agent in scrofula, and for the cure of syphilitic ulcers in those of scrofulous habits. The dose is from 1/8 to 1/2 a grain in pills.

Hydrargyri Biniodidum. Lond. Biniodide of Mercury

"Take of mercury, an ounce; iodine, ten drachms; alcohol, as much as may be sufficient. Rub together the mercury and the iodine, adding the alcohol gradually, until globules are no longer visible. Dry the powder with a gentle heat, and preserve it in a well stopped vessel."

As in the former preparation, the combination of the iodine and the mercury is in this case immediate. The preparation has a red colour, and sublimes in rhombic scales of a yellow colour, which as they cool, again assume a brilliant scarlet hue. They are insoluble in water, but soluble in alcohol, iodide of potassium, and some acids. When dissolved in a hot solution of pernitrate of mercury it crystallizes out, on cooling, in beautiful red scales. It is a compound of 1 eq. of mercury:=202 + 2 of iodine=252.6, making the equivalent =454.6 (Hg I2.)

Medical properties and uses.-This iodide possesses powerful alterative properties, and may be administered in the same cases as the protiodide. I have found it most beneficial in cases of secondary syphilis, administered at the same time as the iodide of potassium. The dose is gr. 1/11 to gr. 1/4, in pills made up with crumb of bread. An ointment, prepared with grs. x. of the biniodide and j. of lard, is useful in ulcers, similar to those in which the ointment of the bin-oxide of mercury is recommended.