Calamina Praeparata. Lond. Prepared Calamine

"Calcine the calamine, and beat it to powder; then bring it into the state of a very fine powder, in the manner directed for the preparation of chalk."

Carbonas Zinci impurus praeparatus, Edin. Prepared impure Carbonate of Zinc.

"Impure carbonate of zinc, roasted by those who make brass, being rubbed to powder in an iron mortar, and levigated with a little water on a porphyry, is to be put into a large vessel, and water poured over it, which, after frequently agitating the vessel, is to be poured off loaded with the powder. The fine powder, which subsides after the water has remained at rest, is then to be dried. The coarse, which the water cannot suspend, is to be again levigated, and treated as before."

Zinci Carbonas impurum praeparatum, Dub. Prepared impure Carbonate of Zinc.

"Reduce calcined calamine stone to powder, and separate the very fine parts in manner directed for the preparation of chalk."

Syn. Calamine prepare (F.), Galmei (G.), Kalmei (Dutch), Galmija (Russ.), Calamina (I.), Calamina (S.).

The nature of this ore of zinc has been already stated (Part II.). As it is frequently used in the form of a dry powder to excoriations, ichorous ulcers, and superficial inflammations, dusted on the part, it requires to be rendered extremely fine.

Officinal preparations.- Ceratum Calaminae, E. Unguentum. Calaminaris, D.

Oxidum Zinci impurum praeparatum, Edin. Prepared impure Oxide of Zinc.

"It is prepared in the same manner as the impure carbonate of zinc."

This substance, the nature of which has been already stated (Part II.), is used for the same purposes as the former article

Zinci Oxydum. Lond. Oxide of Zinc

"Take of sulphate of zinc, one pound; sesquicarbonate of ammonia, six ounces and a half; distilled water, three gallons Dissolve the sulphate of zinc and the sesquicarbonate of ammonia separately in twelve pints of the distilled water, then mix them together. Wash the precipitate repeatedly with distilled water, and burn it for two hours in a strong fire."

Oxidum Zinci, Edin. Oxide of Zinc,

"Let a large crucible be placed in a furnace filled with burning coals, in such a manner as to be somewhat inclined to its mouth; and when the bottom of it is heated to a moderate degree of redness, throw into it a piece of zinc, about the weight of one drachm. The zinc is soon inflamed, and converted into white flocculi, which are occasionally to be removed from the surface of the metal by means of an iron spatula, that the combustion may be more complete; and when the inflammation is over, remove the oxide of zinc from the crucible. Throw in then another piece, and let the operation be repeated as often as is necessary, Finally, let the oxide of zinc be prepared in the same manner as the impure carbonate of zinc."

Dublin.

"Take of zinc broken into small pieces any quantity. Throw these, at intervals, into a sufficiently large crucible, heated to whiteness, and placed with its mouth inclined towards the mouth of the furnace. After each piece of zinc is thrown in, invert over the crucible another crucible, but loosely, so as not to exclude the air. Preserve the light, very white, sublimed powder for use.

Syn. Oxide de Zinc (F.), Weisser Zinkoxyd (G.), Perossido di Zinco; Fiori di Zinco (I.).

In the process of the London College, care should be taken not to add too much ammonia, as it redissolves the precipitate. In the first instance, the precipitate is a carbonate of zinc, from which the carbonic acid is expelled by the ignition. In the two other processes the crucible must be heated above

1 The ancients, who were acquainted with it, called it Pomphoryx; and by the early chymists it was named Nihil album, Lana philosophica, and Flores Zinci. Zincum calcinatum, P. L. 1787. In Holland it was prepared as a secret remedy and sold under the names, Arcanum Ludemanni and Lunna fixata, until Gaubius made public its composition.

700° of Fahrenheit, which is the point of ignition of zinc. At this temperature the metal inflames, burning with a dazzling white and green flame; and by attracting the oxygen of the air it is converted into a white oxide, which is partly volatilized in the form of very light flocculi. The elevation of these flocculi, however, is owing to the current of air excited by the force of the combustion; for the oxide itself is not volatile, but accumulates in the crucible so rapidly, that it must be withdrawn to allow the access of the air for keeping up the combustion. If the crucible be sufficiently capacious, there is no necessity for covering it with another, by which the operation is always impeded.1

Qualities. - Protoxide of zinc thus prepared is inodorous, insipid, of a pure white colour, infusible in the fire, insoluble in water and alcohol, entirely soluble in acids, and in the alkalies: it is not soluble in the carbonates of the alkalies; nor is it altered by exposure to the air. According to Proust 100 parts of it consist of 80 of zinc, and 20 of oxygen; or 100 zinc+ 25 oxygen; or of 1 eq. of zinc 32.3 + 1 of oxygen

8; making the equivalent 40.3 (Zn.) It often contains small portions of carbonic acid.2 It is often adulterated with chalk, and sometimes contains white lead. By pouring sulphuric acid on the specimen, the first is discovered by the effervescence which is excited, the second by an insoluble sulphate of lead being formed.

Medical properties and uses. - Oxide of zinc is tonic and antispasmodic; and has been advantageously used in chorea, epilepsy3, and some other spasmodic affections. It has been employed in hooping-cough on the Continent and Loeffler recommends it to be used externally as well as internally in that disease. He employs a liniment, composed of linseed oil and oxide of zinc. It is chiefly used as an external application. (See Ung. Zinci.)

The dose, as an internal remedy, may be from gr. j. to grs. vj., given twice a day.

Officinal preparation. - Ungentum Zinci, L. E. D.