Preparation

Chloride of zinc is best prepared by dissolving zinc in muriatic acid, filtering the solution, evaporating it to dryness, melting the residue in a crucible, and pouring the liquid upon a clean surface of stone to harden. The metal combines with the chlorine of the muriatic acid to form the chloride of zinc, and the hydrogen escapes. The remaining steps are merely to obtain the preparation in a convenient form. After solidification, it is broken into pieces, and kept in a well-stopped bottle.

Properties

This salt is translucent, of a waxy softness, a grayish-white colour, inodorous, and of an acrid, astringent, metallic taste. it is soluble in water, alcohol, and ether, extremely deliquescent, fusible, and at a high temperature volatilizable unchanged. it is apt to be impure, in consequence of impurities contained in the zinc out of which it is made. For an account of these, and the methods of detecting them, see the U. S. Dispensatory.

Effects. Chloride of zinc is locally irritant and escharotic. When applied in a state of concentration necessary for the caustic effect, it produces a sensation of warmth, quickly followed by a severe burning pain, which continues for several hours. After the cessation of the pain, if the part be examined, it will be found covered with a white eschar, which soon begins to separate, and usually falls off in about ten days. The action is less rapid and extensive than that of potassa, and the pain is more severe and lasting than that occasioned by nitrate of silver; but it produces a much deeper slough than the latter caustic. it appears to exert a tonic influence on the surrounding tissues, with less inflammation than proceeds from arsenious acid. it is believed to owe its escharotic operation to a chemical union which it forms with the albumen and gelatin of the tissues. it has the advantage over arsenious acid as an escharotic, that it never injuriously affects the system through absorption. While it possesses these caustic properties, it acts as a preservative to dead animal tissues, and corrects foul odours by decomposing the emanations on which they depend, especially hydrosulphate of ammonia.

Uses. For the internal uses of chloride of zinc, see page 421 of the first volume. it is chiefly employed for its escharotic effects, and was introduced into use as a substitute for arsenious acid, which it was thought to resemble in caustic properties, without its dangers. it is especially useful in lupus* but is also employed for destroying cancerous tumours and other heterologous growths, aneurisms from anastomosis, and naevi materni, and has been used successfully in a case of aneurism of the subclavian from a penetrating wound. Other applications of it have been to the cure of fistula in ano and chancre, and for the perforation of the case of new bone in necrosis.

Application. in consequence of its extreme deliquescence, it cannot in general be applied alone, as it would be impossible to limit its operation duly. Dr. Canquoin, of Paris, who was mainly instrumental in introducing it into use as a caustic, mixes it into a paste with wheat flour and water. The paste is of different strengths, according to the effect desired, containing one part of the chloride with from two to five parts of flour, every ounce of which requires about fifteen drops of water. it is applied in layers of from one to four lines in thickness; and, in tumours, successive applications are made, as the eschars separate, until the whole diseased structure is removed.

* Dr. Veiel, of Cronstadt, has used chloride of zinc very successfully in 13 cases of lupus, occupying the alae nasi, the upper lip, the cheek, and the ear. He proceeds as follows. When the epidermis has been destroyed and been succeeded by scabs, these are removed by emollient cataplasms. Should the epidermis remain, it should be removed by means of a blister. After this preliminary treatment, by means of a stick of the chloride pointed at one end, the tissues, hypertrophied or surmounted with tubercles, are deeply penetrated, so that the caustic is brought into contact with all the parts affected: and the same operation is to be performed about the lesion, for an extent of two or three lines in all directions. The surface thus treated exudes first a blackish bloody liquid, and afterwards a more or less deeply coloured serosity, which concretes in a few hours into a firm, smooth scab. On the third or fourth day, the edges of these crusts may be raised, and issue given to the liquid beneath by a few punctures. About the sixth or eighth day, they begin to separate, and by the continued application of cataplasms for several days may be removed. it is rarely necessary to repeat the application more than three times. After ward-, the diseased surfaces are to be treated with cataplasms; but, every three or four days, should be lightly touched with an alcoholic solution of the chloride: and, when the borders of the ulcers begin to retract, the watery solution, which is much weaker, should be substituted, and continued to the end. The strength of these solutions will be mentioned further on in the text. The period requisite for a cure rarely exceeds three or four months. (Arch. Gen. de Med., 6e sér , ii. 217, a. d. 1860.) - Note to the third edition.

M. Maisonneuve has introduced a new mode of cauterization, which may be most conveniently effected with the chloride of zinc. The peculiarity consists in introducing the caustic into the interior of tissues, and thus causing it to act from within outward. Making a paste with one part of the chloride and three of flour, with water, he cuts it into pointed strips, which he calls "arrows," and dries them. They are sufficiently hard to be forced into soft tissues; but, when this cannot be done, they may be introduced into slits made by a bistoury. By being arranged, in the near vicinity of each other, circularly around a tumour, they invest it with a mortified portion of tissue, in consequence of which the supply of blood is cut off, and the tumour perishes. Or they may be thrust in great numbers, and close together, into the tumour itself, and thus destroy it. (Moniteur des Hopitaux, No. 115.)

Dr. Alexander Ure, of Glasgow, obviates the disposition of the caustic to run, by mixing it with finely powdered anhydrous sulphate of lime, which has the property of absorbing the moisture. it is thus more accurately limited than in any other mode; for the paste, made of a suitable consistence, retains its form for a long time. The duration of the pain is thus lessened, as the liquid chloride is prevented from running into the sound parts. When the cuticle is sound over a tumour to be destroyed, it should be removed by a blister, previously to the application of the caustic. Dr. Conway, of Richmond, Va., who recommends the chloride of zinc in chancre, applies the saturated solution formed by its deliquescence directly to the sore, and, if it has been too freely applied, washes it off with water, which may be most readily done by a moist sponge (Va. Med. and Surg. Journ., iv. 473.)

Mr. Stanley, of London, has succeeded in removing cancerous tumours of the breast by the application, on pledgets of lint, of a solution of chloride of zinc, containing fifty grains or a drachm of the chloride to a fluidounce of water. The application was more or less frequently renewed according to the severity of its effects, at first as often as every two or three hours in the day. The caustic, thus applied, is said to be less painful than when used in the solid form. {Med. Times and Gaz., April, 1857, p. 407.)

M. Manoury has found advantage in employing the chloride of zinc incorporated with gutta percha, forming a malleable mass, which at a moderate heat may be moulded into sticks, or any other desirable shape. The preparation is made in the same manner as a similar mixture of gutta percha and potassa. (See page 791.) The form of stick thus made is peculiarly adapted for application to the sinuosities of the ulcers of lupus, and others requiring a caustic action.

M. Veiel has used advantageously an alcoholic solution of chloride of zinc, containing equal parts of alcohol and the chloride, in the cure of inveterate eczema of the eyelids, lips, and parts about the genitals and the anus. The same solution readily also removes the indurations sometimes remaining after psoriasis upon the neck, back, and thighs. The aqueous solution, made with 10 parts of the chloride, 10 of muriatic acid, dad 500 of water, sometimes cures eczema impetigenoides which has resisted all other means, and is very useful also in favus and sycosis after the removal of the hairs. M. Veiel has, moreover, found it beneficial in certain forms of acne, and warty excrescences of a suspicious character, affecting the nose, cheeks, and lips. There is a form of psoriasis pal-maris, accompanied with painful warty indurations, which will yield only to the solid chloride, after a previous removal of the epidermis by means of a blister. {Arch. Gén., Aout, 1860, p. 211.)