Iodide Of Mercury

Protiodide Of Mercury. - Subiodide Of Mercury.

This may be made by simply rubbing iodine and mercury together in proper proportions, a little alcohol being added to facilitate the process; or by reaction between calomel and iodide of potassium, in which case an interchange of principles takes place, with the formation of chloride of potassium which may be removed by washing, and of iodide of mercury which remains. it sometimes contains deutiodide, from which it may be freed by washing it thoroughly with boiling alcohol.

Properties

iodide of mercury is a heavy, yellowish-green powder, inodorous and tasteless, insoluble in water or alcohol, but soluble in ether, and slightly soluble in solution of iodide of potassium. it is dark" ened on exposure to light. At a high temperature it is volatilized. Mialhe has shown that, though less readily dissolved by the alkaline chlorides than some other mercurials, it is slightly affected by them, and is even more readily affected than calomel by muriatic acid. it probably, therefore, owes its activity to the solvent agency of these substances. (Chimie Appliq. a la Physiolog., Paris, a.d. 1856, p. 420-1.)

Effects on the System

Green iodide of mercury produces the effects of the mercurials generally; but different opinions are entertained of the degree of its activity. M. Gilbert considers it much more active than calomel, but less apt to produce salivation, while it is less poisonous than corrosive sublimate. (ibid., p. 419.) Dr. Pereira says that it is a powerful irritant poison. (Mat. Med., 3d ed., p. 868.) MM. Trousseau and Pidoux consider it a "powerful, indeed very powerful medicine." (Trait, de Thérap., 4e ed., i. 187.) On the other hand, M. Claude took nine grains with no other effect than an evacuation from the bowels more than twenty-four hours afterwards; and M. Ricord carries the amount of it, which he gives daily, to six or eight grains without inconvenience. (Chim. Appliq. d la Physiol., 422.) The probability is that iodide of mercury is of itself not more active than calomel, and when pure may be given in the same doses. But it is frequently contaminated with the deutiodide, which is a very powerful preparation; and its occasional harshness may be accounted for in this way. Besides, it is dissolved by solution of iodide of potassium, thus being rendered much more energetic; and, as the two may often have been given together, it is very possible that its reputation for extraordinary energy may have arisen partly from this cause. M. Mialhe believes that, when acted on by iodide of potassium, it undergoes a change analogous to that of calomel with alkaline chlorides; is converted, namely, into mercury and the deutiodide; so that it is the latter preparation, and not the protiodide that acts. (ibid., p. 423.) The practical inference is, that great care should be taken to use the protiodide thoroughly free from deutiodide, and that the medicine should not be used simultaneously with iodide of potassium.

Therapeutic Application

iodide of mercury has been found very useful in syphilis; being preferred, in some degree probably, under the impression that it is less liable to salivate than calomel. its composition, moreover, obviously suggested its preferable use in cases of that disease associated with scrofula; and this is perhaps its most useful application. The dose is a grain two or three times a day, to be gradually increased until the desired effect is produced, or until some unpleasant symptom shall appear. it is most conveniently given in the form of pill.

An Ointment (Unguentum Hydrargyri iodidi, Lond.) was directed in the London Pharmacopoeia to be prepared by rubbing an ounce of the iodide with two ounces of wax, and six of lard, previously melted together. it is used for certain skin affections of a scrofulous character, as lupus; and as a dressing for scrofulous, or scrofulo-syphilitic ulcers.* it has not, however, been retained in the British Pharmacopoeia

* iodo-chloride of mercury, made by subliming together two equivalents of calomel and one of iodine, is used by M. Rochard, with great asserted success, in the treatment of acne rosacea. The compound is made into pills, containing about one-sixth form of very dilute ointment, it has been used in opacity of the cornea, and obstinate disease of the eyelids.