Chap. 10.]

METALS.

339

lime and antimony a, and the tartrate of potass and antimony. The first has been found native, What are the uses of antimony?

Antimony is combined with some other metals in making printers' types, and specula for telescopes. Its oxides are employed in medicine, and in colouring glass. In times of remote antiquity it was used by females as a black pigment, for staining the eye-lashes.

What is the nature of bismuth?

BISMUTH is of a yellowish white colour, of a lamellated texture, and moderately hard, but not

of algaroth, is made by merely dropping this solution into pure water. Muriate of antimony has been found native in Bohemia.

The well-known medicine, called James's powder, is a phosphate of lime and antimony. It is a triple salt, in the form of a white powder. For a method of preparing it, consult Phil. Mag. vol. xi.

b Emetic tartar is a tartrate of potash and antimony, composed of about 56 parts tartrate of antimony, 36 tartrate of potass, and 8 of water.

• Perhaps we have no metal more valuable as a medicine than antimony, or one that is applied in such various ways. For particulars, consult the New Edinburgh Dispensatory, by Dr. Duncan, jun.

Kermes mineral, and what was called golden sulphur of antimony, are both made from the sulphuret of this metal, by means of potass. The first took its name from its resemblance in colour to the kermes insect, used in dyeing. The sulphuret, and some other preparations of antimony, are given to horses and cattle, more than any other medicines. They act as alteratives, and are generally to be depended upon for the certainty of their effects.

d If water be added to a solution of bismuth in nitric acid, the oxide will be precipitated of a pure white colour; but if a little tincture of galls be poured into a similar solution, a brown precipitate will be produced. This is the distinctive characteristic of this metal.

malleable. It is so brittle that it breaks readily under the hammer, and may be reduced even to powder a

How is bismuth procured?

Bismuth is generally found with cobalt in the cobaltic ores of Saxony and England. Native bismuth and sulphuret of bismuth are also found upon the continent, but this is not an abundant metal.

What is the effect of oxygen upon bismuth?

Bismuth is gradually oxidized by fusion in atmospheric air; and may be thus converted into at least two varieties of oxides b.

a Bismuth has the singular property of expanding as it cools. Hence, probably, its use in the metallic composition for printers' types; as from this expansive property are obtained the most perfect impressions of the moulds in which the letters are cast. In manufactories this metal is known to the workmen by the name of tin-glass. Its sp. gr. is 9.8227. The Jarger kind of printers' types are generally made with lead and antimony only; in the proportion of 4 parts of the former, to one of the latter. It surely is not possible to contemplate the advantages that the world has derived from the invention of printing, without very peculiar emotions!

"Sad Superstition wails her empire torn,

Art plies his ore, and Commerce pours her horn." Bismuth is one of the metals that will inflame when thrown into oxymuriatic acid.

Pearl-white is an oxide, or rather a sub-salt, of this me tal. Ladies use it for painting the skin, to which it imparts a beautiful white; but it has the inconvenience of becoming black by the contact of sulphuretted hydrogen gas, or the fumes of fetid substances. The gas which arises from the burning of mineral coal will have the same effect. It is related of a lady of fashion, who had incautiously seated herself too near the fire at a quadrille table, that her countenance changed on a sudden from a delicate white to a dark tawny, as though by magic. The surprise and confusion of the whole

What salts are there of bismuth?

Several salts of bismuth have been formed, but their properties have not been much examined by chemists. The nitrate and muriate of bismuthb are occasionally prepared, but no salts of this

metal have been found in a native state.

What are the uses of bismuth?

Bismuth is used with other metals not only to form printers' types, but also to make pewter, and for some other compounds. It remarkably contributes to the fusibility of some alloys;

party had such an effect upon the disfigured fair one, that she was actually dying with apprehension, when the physician dispelled their fears, by informing his patient that nothing more was necessary than for her to wash her face, to abstain from the use of mineral cosmetics, and to trust in future to those charms which nature had bestowed upon her.

Some of the French chemists recommend the use of the oxides of bismuth for dyeing, to fix some particular colours, Pomatum prepared with the oxide of bismuth turns the hair black.

a Nitrafe of bismuth does not dissolve in water like other metallic salts, but becomes decomposed, forming one of the most delicate white precipitates; hence, this metal is readily distinguished from most others. This precipitate, washed and dried, is what has been called magistery of bismuth, or pearl white.

b Butter of bismuth, as it was formerly called, is a muriate of this metal.

The common mixture for pewter is 112 pounds of tin, 15 pounds of lead, and 6 pounds of brass; but many manufacturers use also bismuth and antimony to compose this metal. Bismuth is likewise generally mixed with tin for vessels of capacity, &c., as it gives to that inetal a greater degree of bril liancy and hardness. From its property of rendering lead more. fusible, it is too often employed with that metal to adulterate quicksilver.

dIf 8 parts of bismuth, 5 of lead, and 3 of tin be melted together, the mixed metal will fuse at a heat no greater than 212°. Tea-spoons made with this alloy are sold in London, to surprise those who are unacquainted with their nature. They have the

hence, it is employed to make solder. Bismuth is likewise given in medicine, though, now, very rarely.

a

What is the nature of arsenic?

ARSENIC is generally found in combination with acids, sulphur, or oxygen. When reduced to its pure metallic state, it is a friable, brilliant metal, of a blueish white colour, easily tarnishing, that is, oxidizing by exposure to the aird. In all its states it is extremely poisonous.

appearance of common tea-spoons, but melt as soon as they are put into hot tea A composition of lead, zinc, and bismuth, in equal parts, will melt with so small a portion of caloric, that it may be kept in fusion upon paper over a lamp.

a Arsenic may be known by the smell of garlic, and by the white fumes which it exhales when thrown on a piece of redhot coal. Its sp. gr. is 8.310.

b Nitrate of arsenic will precipitate the salts of copper of a beautiful green colour. This precipitate is exactly the same as the native arseniate of copper found in the mines of Cornwall.

The oxides of arsenic in solution are discovered by sulphuretted hydrogen, which produces a yellow-coloured precipitate. This precipitate is the same as that beautiful ore called orpiment (sulphuret of arsenic).

d If arsenic, in its pure metallic state, be kept covered with alcohol, its metallic brilliancy will be preserved.

If metallic arsenic be previously inflamed in oxygen gas, it will burn till the whole is consumed. The combustion is very brilliant, and forms a striking experiment.

e Dr. Pearson has said, that white arsenic, in the quantity of one sixteenth part of a grain, is as harmless as a glass of wine, and, in that dose, is a remedy for inveterate agues. See Dr. Pearson on Sulphate of Iron, &c. Phil. Magazine, vol. xxi. 56. But it is so poisonous that if one grain, in complete solution, were administered at one time, it might occasion death.

Whenever arsenic has been taken internally, by design or mistake, the best medicine is sulphuret of potash (liver of sulphur) dissolved in water. A few scruples should be dissolved in half a pint or a pint of water, and administered a little at a time as the patient can bear it.

Where is arsenic found?

Arsenic is found in Bohemia, Hungary, Saxony, and other places on the continent. It is united with, and contaminates, many of our metallic ores in England.

What is the effect of oxygen upon arsenic?

Arsenic has a great affinity for oxygen, of which it admits of various doses, till it becomes at last arsenic acidc.

What salts of arsenic are there?

The salts which have been formed with this

a The arsenic of commerce is prepared in Saxony in the operation of roasting the cobalt ores for the manufacture of zaffre. The reverberatory furnace in which the ores are roasted terminates in a long horizontal chimney; and in this chimney the arsenical vapours are condensed, forming a crust, which at stated times is cleared off by criminals, who are condemned to this work for crimes for which they would otherwise have suffered death. White arsenic is prepared by mixing the common oxide with potash, and submitting it to sublimation. By this process the arsenic is separated, and sublimed, leaving its sulphur behind, united to the potash.

In analysing the ores of arsenic, or the ores of any of the metals whose oxides are volatile, the upper part of the crucible should always be filled with charcoal; so that whatever is volatilized may be caught by the charcoal, and immediately reduced.

b

↳ Arsenic is frequently found in martial pyrites, and in copper ores. See Gellert's Metallurgic Chemistry, and Henkel's Pyritologia.

Lead, when contaminated by arsenic, may be purified by melting it with a few iron filings. The iron combines with the arsenic, and these, being lighter than the lead, float on the surface, from which it may be readily skimmed off.

Arsenic is capable of combining with so large a portion of oxygen as to become changed into a perfect acid. See p. 193. There are four other metals which are completely acidifiable; viz. chromium, molybdenum, tungsten, and columbium: there is, however, some doubt respecting the acidifiable nature of tungsten.