Unguentum Oxidi Hydrargyri Cinerei. Edin. Ointment of Grey Oxide of Mercury

"Take of grey oxide of mercury, one part; hog's lard, three parts. Mix."

Syn. Graue Quecksilbersalbe (G.).

As the whole of the mercury in this ointment is oxidized, it might, a priori, be supposed that it would answer all the purposes of the mercurial ointment; but it cannot be so easily introduced by friction, the oxide remaining on the surface of the cuticle after the unctuous matter is absorbed. Dr. Paris justly remarks, that this is owing to its being a mechanical mixture instead of a chymical combination: an opinion, however, which is rendered doubtful by the experiments made to prove the non-oxidation of the mercery in the preparation of the mercurial ointment. It has been too seldom employed to enable a correct judgment to be formed of its efficacy.

Unguentum Hydrargyri Nitratis. Lond. Ointment of Nitrate of Mercury

"Take of mercury, an ounce; nitric acid, eleven fluid drachms; lard, six ounces; olive oil, four fluid ounces. First dissolve the mercury in the acid; then mix the solution while it is hot, with the lard and oil melted together."

Unguentum Nitratis Hydrargyri fortius; vulgo, Unguentum Citrinum, Edin. Stronger Ointment of Nitrate of Mercury.

"Take of purified mercury, one part; nitrous acid, two parts; olive oil, nine parts; hog's lard, three parts. Dissolve the mercury in the acid; then beat up the solution strongly with the lard and oil previously melted together, and nearly cold, in a glass mortar, so as to form an ointment."

Unguentum Nitratis Hydrargyri; vulgo, Unguentum Citrinum, Dub. Ointment of Supernitrate of Mercury.

"Take of purified mercury, an ounce; nitric acid, eleven drachms and a half; olive oil, one pint; hog's lard, four ounces. Dissolve the mercury in the acid; then mix the solution with the oil and lard previously melted together, and form an ointment in the same manner as the ointment of nitrous acid."

Syn. Onguent citrin (F.), Gelbe Quecksilbersalbe (G.), Uuguento Citrino(I.).

Unguentum Nitratis Hydrargyri mitius, Edin. Milder Ointment of Nitrate of Mercury.

"It is made in the same manner as the stronger ointment, with a triple proportion of oil and lard."

In all of these formulae too large a proportion of lard is used; for the excess of acid in the metallic solution oxidizing the fatty matters, occasions them to become too hard and brittle after the ointment has been kept for some time, when more than one sixth of lard is employed. The addition of the metallic solution to the melted mixture of lard and oil should be gradual, and made in a broad flat vessel, so as to expose a large surface to the action of a current of air; while the stirring should be performed with a wooden spatula, and continued until the ointment be perfectly cold.

When prepared in the above manner, and with one sixth part only of lard, this ointment has a beautiful golden colour, and is of the consistence of butter, which it retains if preserved in close pots; but when made with a larger proportion of lard, it becomes hard, brittle, and of a pale, dirty yellow hue, marbled with green blotches.

Mr. Duncan of Edinburgh prepares this ointment with

xij. of nitrous acid, iv. of mercury, xxvjss. of olive oil, and xij. of lard. He pours the solution of mercury, still hot, into the lard melted in the oil, and still hot, and mixes them, assisting the combination by heat if it does not froth up. The vessel should be large, as a violent effervescence takes place. This ointment preserves its colour and consistence.

Medical properties and uses. - This ointment is stimulant and detergent. When moderately diluted with lard it is a local remedy of great efficacy in herpes, psoriasis, porrigo, and other cutaneous eruptions. The weaker ointment may almost be regarded as a specific in psorophthalmia, in the purulent ophthalmia of infants producing ectropium, and in ulcerations of the tarsi. It is applied by taking a little on the finger, liquefying it by the fire or the flame of a candle, and applying it along the inner part of the eyelids.