Unguentum Hydrargyri Fortius. Lond. Strong Mercurial Ointment

"Take of purified mercury, two pounds; prepared lard, twenty-three ounces; prepared suet, an ounce. First rub the mercury with the suet, and a little of the lard, until the globules disappear; then add the remainder of the fat, and mix.

Two drachms of this ointment contain one drachm of mercury.

Unguentum Hydrargyri, Edin. Mercurial Ointment.

"Take of mercury, mutton suet, of each one part; hog's lard, three parts. Rub the mercury diligently in a mortar, with a little of the hog's lard, until the globules disappear; then add the remainder of the lard.

"It may also be made with double or treble the quantity of mercury."

One drachm of this ointment contains twelve grains of mercury.

Dublin.

"Take of purified mercury, prepared hog's lard, equal weights. Rub them together in a marble or an iron mortar until the globules disappear."

Syn. Onguent Mercuriale (F.), Quecksilbersalbe (G.), Unguento Mercuriale (I.).

One drachm of this ointment contains thirty grains of mercury.

Unguentum Hydrargyri Mitius. Lond. Dub. Milder Mercurial Ointment

"Take of the stronger mercurial ointment, a pound; prepared lard, two pounds. Mix them."

1 Ung. caeruleum fortius, P. L. 1745.

2 Unguentum caeruleum mitius, P. L. 1745.

One drachm of this ointment contains ten grains of mercury; but prepared according to the Dublin Pharmacopoeia, with two parts of lard to one of mercury, one drachm contains a scruple of mercury.

The preparation of the stronger mercurial ointments requires much labour, care, and patience. During the trituration the mercury is mechanically divided into minute globules, which are prevented from running together again by the viscosity of the suet. They are by some supposed to be gradually oxidized, during the trituration, by the atmosphere; the lard, the extension, and the constant renewal of the surface exposed, favouring very much this effect. The fact of the oxidize-ment of the metal in this process, however, has been often questioned; and some experiments of M. Roux have thrown much light on the subject. That chymist triturated mercury and maltha, a species of pitch, in a vacuum, and produced the extinction of the metal as well as if the operation had been performed in the air; thence he concludes that the metal is not oxidized, but merely mechanically divided in the ointment. There are still, however, some difficulties in deciding this point. Whatever tends to favour oxidation, as for instance a slight degree of rancidity of the lard, or the oil of eggs, shortens the time, and lessens the labour, required for the preparation of the ointment.

It is not uncommon, however, to use other means, which are not admissible, to facilitate the process, such as the use of sulphur or turpentine. The first may be detected by the very black colour of the ointment, which is produced by the sulphuret of mercury; and also by the sulphurous odour exhaled, when a paper covered with a little of it is held over the flame of a candle; and the turpentine is detected by its odour also, when the ointment containing it is treated in the same manner. When newly prepared, mercurial ointment has a light grey or bluish colour; this has been ascribed to its containing some unoxid-ized metal, which separates in globules when it is liquefied by a gentle heat; when kept for some time the colour is much deepened, and less metallic mercury subsides, owing to the more complete oxidizement of the metal. As it is of great consequence to procure so important a preparation always of the same degree of strength, and as this can never be accomplished by the present method of preparing the ointment, Mr. Donovan has proposed to prepare it by using black oxide of mercury, at the temperature of 350° Fahrenheit, continuing the friction for two hours.

By this method of proceeding, Mr. Donovan found that every ounce of lard dissolves and combines with twenty-one grains of oxide; that the ointment thus prepared can be introduced into the habit in one third of the time required by the common ointment; and that it is equally efficient with the officinal preparation.

Medical properties and uses.- The strong mercurial ointment rubbed upon the skin introduces a large quantity of mercury into the system. About 3 j. is rubbed upon the inside of the thighs, or any other part of the body where the cuticle is thin, every night and morning, until the system is affected. The ointment is absorbed during the friction, which slightly abrades the cuticle, and admits it to the mouths of the absorbents, so as to permit it to be carried into the habit; where it produces the same effects as those which result from taking mercurials by the mouth, without the unpleasant affection of the bowels that very commonly follows the introduction of preparations of mercury into the stomach. In order, however, to produce the full effect of the friction, it must be continued until every particle of the ointment disappear; and the operation should be performed by the patient himself. The stronger mercurial ointment is used in this form as an antisyphilitic, as a deobstruent in hepatic affections, and to excite the absorbents in hydrocephalus. The weaker ointment is used only as a topical dressing in venereal sores.

During a course of mercurials the patient should be kept in a moderately warm and dry, but airy chamber; and his diet should be chiefly weak broths, milk, and gruel.

The following table shows at one view the quantity of mercury contained in each of the different ointments ordered by the British Colleges.