Origin and Properties. The oxide of zinc is prepared either by burning the metal, and condensing the vapours, or by heating the carbonate of zinc strongly, and thus driving off the carbonic acid. Procured by the former method, it has been called flowers of zinc. In composition it is a protoxide, consisting of one equivalent of each of its ingredients. It is a white powder, without smell or taste, unalterable in the air, insoluble in water, but readily dissolved by most of the acids.

Effects on the System

Oxide of zinc is probably inert in its uncom-bined state; but, as there is very often free acid in the alimentary canal, with which it may react so as to form soluble salts, it is capable of producing the characteristic effects of the preparations of zinc on the system. The experiment of Orfila, who gave to a small dog from three to six drachms, without producing any other observable effect than vomiting, is not to be received as a sufficient proof of the inactivity of the oxide; for there may have been no acid present in the stomach, or too little to generate any considerable proportion of soluble salt. Given largely to men, it is said sometimes to have produced vomiting and purging; and even giddiness and intoxication have been mentioned among its effects. As already stated, in the general remarks on the metal, it is capable of acting injuriously when used freely and for a long time. Having recently been largely employed as a substitute for white lead in painting, in consequence of retaining its white colour when exposed to the action of sulphuretted hydrogen, it is a very happy circumstance that, if not absolutely innoxious, it should have proved so much less injurious than that paint. Its general effects on the system, so far as it acts at all, may be considered as identical with those of the preparations of zinc already described.

Therapeutic Application

This medicine has been used in all the nervous affections to which the preparations of zinc are deemed applicable; namely, epilepsy, catalepsy, chorea, hysteria, hooping-cough, neuralgia, and gastric spasm; but it is in the treatment of epilepsy that it has enjoyed the highest reputation. If some accounts which have been published of its efficacy are to be relied on, it is capable of curing a very considerable proportion of cases; but they who are familiar with this disease, and know how obstinately, when once established, it v< every variety of treatment, are prepared when they read such reports to make many allowances for failure in diagnosis, for the deceiving effects of preconception, and for the fact, almost universally noticed, that the paroxysms of epilepsy are often suspended, and sometimes kept long at bay, by anything calculated to excite the hopes and occupy the attention of the sufferers. When the disease is purely functional, it may often, no doubt, be cured, if submitted to treatment at an early stage; and there is as little doubt that it has not unfrequently given way under the use of oxide of zinc; but the number of failures, taking all the cases into consideration, will probably greatly exceed the cures effected by this remedy. It has the advantage over the sulphate, that it is less disposed to irritate the stomach and bowels; and it may, therefore, be used preferably when these organs are peculiarly delicate.

Since the publication of the first edition of this work, the oxide of zinc has acquired some reputation in the treatment of the night-sweats of phthisis. My own trials with it have not been so satisfactory as to induce me to join in its recommendation from personal observation.

The dose is from two to eight grains or more, given three times daily. It should not be indefinitely increased; as conditions of the alimentary canal, in which it may be innocent at one time, may be so changed that it shall prove highly irritant at another. I do not think that the dose of twenty grains should be exceeded; and, should irritant effects be experienced, the smaller doses mentioned should be diminished, or withheld for a time. It may be given in pill, or in powder mixed with syrup.

External Use

As in the case of the carbonate, this preparation may possibly be dissolved, in minute quantities, in the liquid secretion proceeding from diseased surfaces, and thus rendered positively efficient in its action on such surfaces. In the form of powder or ointment, the oxide has been much used as an absorbent, desiccant, and alterative, in cutaneous eruptions characterized by copious liquid extravasation, as in eczema and impetigo, in excoriations of all kinds, superficial burns, blisters, chapped hands, lips, and nipples, and profusely secreting ulcers. In chronic ophthalmia, it has been recommended in the form of a collyrium, made by diffusing a drachm of the powder equably in three or four fluidounces of mucilaginous liquid; and the same method of preparation has been recommended in cutaneous affections, and for injections in gonorrhoea and leucorrhoea.

Ointment of Oxide of Zinc (Unguentum Zinci Oxidi, U. S.) is made by mixing one part of the oxide with six parts of lard. It was intended as a substitute for the old tutty ointment (unguentum tutiae) prepared in the same manner from tutty, which is an impure oxide of zinc, of uncertain strength, formerly much used, but now nearly abandoned.