copper formed brass. Besides being mentioned by Pliny, it also occurs in the writings of Albertus Magnus, who died in 1280. The word zinc also occurs in the writings of Paracelsus, who died in 1541. Zinc is also known by the name of spelter. Henkel, Von Swab and Margraff, pointed out the means of obtaining it from its ore. It has been obtained in the United States from the sulphuret of zinc, which is found at Perkiomen, and in some other places in this country.

Its

Zinc is a white metal, whose hardness is 61⁄2, and whose specific gravity varies from 6.8 to 7.1. malleability is by no means to be compared to some of the other metals. When heated somewhat above 212° it becomes very malleable. When carefully annealed it may be made into thin plates. At 400° it becomes extremely brittle, and may be reduced to powder in a mortar. It possesses some degree of ductility. Its tenacity is such, that a wire whose diameter is th of an inch, is capable of supporting a weight of 26 pounds.

Experiment 5. If zinc be heated to the temperature of about 680°, fusion will take place; and,

Experiment 6. If the heat be increased, the metal evaporates, and may be collected in close vessels.

Experiment 7. If melted zinc be allowed to cool slowly, quadrangular prismatic crystals will be obtained.

Experiment 8. If the vapour of water be made to pass over zinc at a very high temperature, the metal will become oxydized, and hydrogen gas emitted.

Rationale. The water is decomposed; its oxygen unites with the zinc, and its hydrogen is disengaged in the form of gas.

Experiment 9. If zinc be melted in an open vessel, exposed to the air, its surface will become covered with a gray coloured pellicle, and the whole is gradually changed to a gray powder, being the gray oxyd of zine.

Experiment 10. If zinc be exposed to a strong heat in an open vessel, it will take fire and burn with a

brilliant white flame, emitting a quantity of white flakes, known by the names of pompholyx, nihil album, lana philosophica, and flowers of zinc.

Rationale. In combustion, zinc combines with oxygen, forming a white oxyd, and the gas gives out caloric and light.

Experiment 11. If sulphate of zinc be decomposed by the addition of potash, a white precipitate will be obtained, which, when washed and dried, forms the per oxyd, or white oxyd of zinc.

Rationale. Zinc combined with sulphuric acid in the sulphate, is oxydized to the maximum; if this compound be decomposod by potash, the sulphate of that alkali is formed, and the per oxyd of zinc is precipitated. The per oxyd contains 20 per cent. of oxygen.

Experiment 12. If the per oxyd of zinc be exposed to a strong heat in an earthen-ware retort, or covered crucible, it assumes a yellow colour, and is reduced to the state of prot oxyd.

Rationale. The exposure to heat expels a portion of oxygen from the per oxyd, forming thereby the prot oxyd.

Experiment 13. Take a phial with a solution of sulphate of zinc, and another containing a little liquid ammonia, both transparent fluids. By mixing them, a curious phenomenon may be perceived: the zinc will be immediately precipitated in a white mass, and, if then shaken, almost as instantly re-dissolved.

Rationale. The ammonia precipitates the zinc in the form of oxyd, and produces sulphate of ammonia; the oxyd is then dissolved by another portion of the ammonia, forming the ammoniaret of zinc.

Experiment 14. Mix equal parts of nitrate of potash and filings of zinc, and project the mixture by spoonfuls into a crucible which has been brought to a state of ignition. When the powder has acquired a certain degree of heat, a strong detonation suddenly takes place; as soon as it ceases throw another spoonful of the mixture into the vessel, and repeat the ope

ration till the whole quantity is consumed. duum will be an oxyd of zinc.

The resi

Remark. This experiment requires caution, to pre

vent accidents.

Experiment 15. When a few grains of fine zine filings and oxygenated muriate of potash are struck on an anvil, a violent detonation takes place, with a white flame.

Experiment 16. Distil two parts of muriate of mercury and one of zinc, in a glass retort; a salt which crystallizes in small needles united together will be sublimed, and the mercury will remain fluid in the retort. This salt is muriate of zinc.

Experiment 17. If zinc be melted, and small pieces of phosphorus dropped into it while in fusion, a compound called phosphuret of zinc will be formed.

Experiment 18. If 12 parts of oxyd of zinc, 12 parts of phosphoric glass, and 2 parts of charcoal powder, be mixed and distilled in an earthen retort in a strong heat, a phosphuretted oxyd of zinc will be the result

Experiment 19. If sulphur be melted with oxyd of zinc, a combination is formed, called the sulphuretted oxyd of zinc.

The alloys of zinc have already been mentioned. 1. With gold: it has been proposed by Mr. Hellot as very proper for the specula of telescopes. Gold.

See

2. With platinum it forms a brittle alloy. See Platinum.

3. With silver it forms an alloy of a bluish white colour. See Silver.

4. With mercury it forms amalgams of different degrees of hardness. See Mercury.

SECTION XVI.

OF BISMUTH.

Experiment 1. If the ore of bismuth be fused with an eighth part of white flux in a well closed vessel, the metal will be obtained.

Remark. Bismuth thus obtained is not pure, but constitutes the metal of commerce. In order to purify it, the following process is necessary.

Experiment 2. Powder the product of Experiment 1, and dissolve it in pure nitric acid, and precipitate by adding water to the solution, collect the precipitate, form it into a paste with oil, and rapidly fuse it with black flux in a closed crucible.

Rationale. The solution of the bismuth of commerce in nitric acid not only dissolves that metal, but others, with which it may be mixed, and the oxyd thrown down by water on being treated with a carbonaceous flux is reduced to the state of metal.

Remark. The German miners appear to have discovered this metal, and to have given it the name of bismuth; they also called it tectum argenti. A number of Essays were written on it at different times. The metal is of a reddish white colour, extremely brittle, and can not be drawn out into wire. Muschenbroeck says, that a rod th of an inch in diameter will sustain a weight of 29 pounds. It melts at 476° and may be volatilized by continuing the heat. On exposure to the air, it loses its lustre. The yellow oxyd may be obtained in the following manner:

Experiment 3. If bismuth be raised to a strong red heat it takes fire, and emits a yellow smoke, which, when collected, condenses into a yellow powder.

Rationale. During combustion it unites with oxygen, forming an oxyd, which is disengaged in the form of smoke.

Experiment 4. If the powder of bismuth be thrown into oxymuriatic acid gas, it will take fire, and exhibit a beautiful phenomena. See the Properties of Oxymuriatic acid gas.

The compound thus formed consists of the metal oxydized to the maximum, and muriatic acid, and is called butter of bismuth, but Mr. Davy calls it bismuthane.

Experiment 5. If bismuth be dissolved in nitric acid, and water poured into the solution, a white powder will fall, which, when collected, and washed in the usual manner, forms the white oxyd used in medicine, or the magistery of bismuth, known also by the name of pearl or flake white.

Rationale. See Experiment 2. This oxyd is the per oxyd; but some consider it a sub nitrate, and others a hydrate of bismuth.

Experiment 6. If the white oxyd of bismuth be placed in an atmosphere of sulphuretted hydrogen gas, it will become tarnished, forming a sulphuretted oxyd. Hence the impropriety of using this oxyd as a cosmetic. Ladies, in the habit of using it, on going into waters containing that gas, have become dark tawnies. Some idea may be had of this fact from the following experi

ment.

Experiment 7. A letter written with a diluted solution of bismuth, becomes, when dry, illegible, but a feather dipped into a solution of sulphuret of potash, will instantly blacken the oxyd, and revive the writing.

Rationale. The acid of the solution of bismuth first unites with the potash of the sulphuret, and the sulphur then combines with the oxyd, forming a black sulphuretted oxyd.

Experiment 8. Write on paper with a solution of nitrate of bismuth; when this is dry the writing will be invisible; but if the paper be immersed in water, it will be distinctly legible.

Rationale. The nitrate of bismuth being insoluble in water, on coming in contact with that fluid is decomposed; the oxyd of bismuth is therefore separated.