Zinci Sulphas

Lond. Sulphate of Zinc. "Take of zinc, in small pieces, five ounces; diluted sulphuric acid, two pints. Pour gradually the diluted sulphuric acid upon the pieces of zinc, and the effervescence being finished, filter the solution; then boil it until a pellicle begin to form. Lastly, set it aside to crystallize."

1 This oxide may also be readily prepared by dissolving sulphate of zinc and precipitating by potassa, a process proposed by Marabelli, professor of pharmacy at Pavia, in 1798. The washed precipitate is oxide of Zinc, containing, according to Vauquelin, 0.21 of oxygen,

2 Annales de Chimie, xxxv. 51. The more recent experiments of Dr. Thomson make the proportions to be metal 100+ 24.16 oxygen : Those of Berzelius, metal 100+24.4 oxygen.

3 Duncan's Med. Comment. in. 216. 4 Zincum vitriolatum, P. L. 1787.

Edinburgh.

"Take of zinc, cut into small pieces, three parts; sulphuric acid, Jive parts; water, twenty parts. Mix them, and the effervescence being finished, digest for a short time on hot sand. Then filter the decanted solution through paper, and after due evaporation, set it aside that crystals may be formed."

Dublin.

"Take of zinc, reduced to small pieces, thirteen parts; sulphuric acid, twenty parts; water, one hundred and twenty parts. Pour the acid, previously diluted with the water, upon the zinc; put into a glass vessel; digest for a short time after the effervescence ceases; then evaporate the strained solution to a proper point, and set it aside to crystallize."

Syn. Sulphate de Zinc (.F.), Schwefelsaures Zink (G.), Solfatodi Zinco (I.). Vitriolo bianco (S.).

The directions of the Dublin College for granulating the zinc are to be adopted in preference to those of the other colleges for dividing it. In these processes, the acid enables the zinc to decompose the water, and the metal is oxidized by attracting its oxygen, while its hydrogen is disengaged with effervescence. The oxide thus formed combines with the acid, forming sulphate of zinc, which is obtained in crystals by the subsequent evaporation. The greater part, however, of the sulphate of zinc of the shops is prepared on a large scale, and purified in the manner that shall be immediately noticed. It is denominated white vitriol in the language of commerce, and is manufactured largely both in Germanyl and England. In Germany it is prepared by exposing roasted blende to the air and humidity; by which means the metal is gradually oxidized, and combined with the sulphuric acid also formed from the sulphur contained in the blende. The sulphate thus produced is separated from the earthy parts of the blende by lixiviation; and after being boiled down it is crystallized, or rather concreted, into granular masses, resembling loaf-sugar; which generally contain sulphate of iron, of lead, and of copper.

In England it is prepared generally by the direct combination of its constituents; but although purer than the foreign salt, yet the English sulphate almost always contains iron. Both kinds are purified by solution in water, and then allowing the solution.to evaporate very slowly in an open vessel, containing some granulated zinc; the sulphate of lead will subside, and the other foreign salts be decomposed by the metallic zinc. The purified sulphate of zinc may be then crystallized by lixiviation and evaporation.l

1 Beckman, in his History of Inventions, says, it was first made at Ramelsberg, in Germany, about the middle of the 10th century. He ascribes the invention to Julius, Duke of Brunswick.

Qualities. - Pure sulphate of zinc is inodorous, colourless, and has a slightly acidulous, styptic, metallic taste. It crystallizes in transparent, right rhombic prisms'2, terminated by quadrangular pyramids; it effloresces slightly in the air; is soluble in 2.5 times its weight of water at 60°, and in less than its own weight of boiling water. It is decomposed by the alkalies, earths, and hydrosulphurets: and throws down a dirty-looking precipitate from astringent vegetable infusions, with which, therefore, it is incompatible in prescriptions. According to the analysis of Dr. Wollaston, the constituents of 100 parts of the pure crystallized salt are 28.4 of oxide of zinc, 27.3 of acid, and 44.3 of water: or 1 eq. of protoxide of zinc = 40.3+1 of sulphuric acidz = 40.1 + 7 of water = 63; making the equivalent 144.4. (Zn S.)

Medical properties and uses. - Sulphate of zinc is tonic and astringent, and in large doses emetic. As a tonic, it -is less heating and stimulant than sulphate of iron; and thence is preferable in phthisis, and other diseases attended with great irritability and general weakness. It is also useful in dyspepsia, fluor albus, and some convulsive affections, as pertussis, chorea, and epilepsy; in which diseases it is generally combined with myrrh, bitter extracts, opium, extract of hemlock, or digitalis, according to the circumstances of the case. As an emetic it operates almost instantaneously, and, therefore, is often employed to empty the stomach at the commencement of the paroxysm of intermittent fever, and in other cases in which quick vomiting is required. In large doses it is poisonous.3 As an external application, this salt dissolved in rose-water, in the proportion, of gr. iss. to f j of rose-water, forms an excellent collyrium in the latter stage of ophthalmia, after the inflammatory action has subsided; it is a good injection in gonorrhoea; and a lotion in some kinds of superficial inflammations. The solution, double the strength, is the best application that can be used to scrofulous tumours, after they have suppurated, and the abscess has been discharged.

The dose to produce vomiting, is from grs. x. to 3 ss., and as a tonic from gr. j. to grs. ij. may be given twice a day. Officinal preparations. - Solutio Sulphatis Zinci, E. Liquor Aluminis compositus, L. Solutio Acetatis Zinci, E. D.

1 Aikin's Dictionary of Chemistry. 2 Phillips's Trans, of the Pharm. 1824.

3 It is a singular fact, that the Aranea scenica devours sulphate of zinc, and deprives it of its acid.