Obrazy na stronie



Tungsten is obtained from a mineral called wolfram, which contains the oxyds of tungsten, manganese, and iron, with earthy matter. Mineralogists call tungsten a mineral, which contains the oxyd or acid combined with lime. Although several attempts have been made by different chemists to obtain this metal, yet very few have succeeded. It may be produced in the following manner, according to Richter.

Experiment 1. Let equal parts of tungstic acid and dried blood be exposed for some time to a red heat in a crucible; press the black powder which is formed into another smaller crucible, and expose it again to a violent heat in a forge for at least an hour. Tungsten will then be found, according to this chemist, in its metallic state in the crucible.

To produce the metal pure, the following process has been recommended.

Experiment 2. Boil finely pulverised wolfram in strong muriatic acid for some time; separate the solution; the residuum contains a yellow powder; it is to be washed, dissolved in ammonia, evaporated to dry. ness, and mixed with a little fine charcoal powder, and exposed to a very intense heat for about 20 minutes in a covered Hessian crucible. Small grains of pure tungsten will be found at the bottom of the crucible.

Tungsten in its metallic form was first procured by Messrs. D'Ethuryars in 1782.

Remark. Tungsten or Scheelium of the Germans, is of a grayish white colour. Its specific gravity is 17.3. It requires for fusion about 170° Wedgwood. It combines with oxygen, forming a blue and yellow oxyd. The prot oxyd is blue, and the per oxyd is yellow, known by the name of tungstic acid. The former may be obtained by heating the yellow oxyd for some

hours in a covered crucible, and the latter, or tungstic acid, in the following way:

Experiment 3. Boil three parts of muriatic acid on one part of wolfram. Decant the acid, and allow it to settle. A yellow powder gradually precipitates. This powder is to be dissolved in ammonia, the solution to be evaporated to dryness, and the dry mass kept for some time in a red heat. It is then yellow oxyd, or acid in the state of purity.

Sulphur and phosphorus will both unite with tungsten. Silver, copper, iron, lead, tin, antimony, and bismuth will combine with it; but it does not unite with gold and platina. It is not attacked by the sulphuric, nitric, or muriatic acids; nitro-muriatic acid acts upon it very slightly. It is oxydable and acidifiable by the nitrates and super-oxygenated muriates. It colours the vitrefied earth, or the vitreous fluxes, of a blue or brown colour. It is not known what its action will be on water and different oxyds. Its action on the alkalies is likewise unknown. It is not employed yet, but promises real utility, on account of its colouring property, as a basis for pigment, since the compounds it is said to form with vegetable colouring matters afford colours so permanent as not to be acted on by the most concentrated oxygenated muriatic acid, the great enemy of vegetable colours. See Thomson, Murray, Fourcroy, &c.

[ocr errors][merged small][merged small]

This newly discovered metal was first noticed by Mr. Gregor as existing in the state of an oxyd, mixed with iron, manganese, and silica, in a grayish black sand found in the vale of Manachan in Cornwall, and thence named Menachanite, or oxyd of Titanium, combined with iron. It has since been discovered by Klaproth, in an ore named Titanite, or oxyd of Titanium, combined with

lime and silex. It exists also in an ore called Red schori of Hungary, or red oxyd of Titanium,

It is extremely difficult to reduce the oxyd of titanium to the metallic state. However, the experiments of Klaproth, Hecht, and Vauquelin, have proved its reducibility

Experiment 1. According to the two latter, one part of the oxyd of titanium is to be melted with six of potash; the mass when cold is to be dissolved in water. A white precipitate will be formed, which is carbonate of titanium. This carbonate is then made into a paste with oil, and the mixture is put into a crucible filled with charcoal powder and a little alumina. The whole is then exposed for a few hours to the action of a strong heat. The metallic titanium will be found in a blackish puffed up substance, possessing a metallic appearance.

Remark. Titanium has only been obtained in very small agglutinated grains. It is of a red yellow and crystalline texture, brittle, and extremely refractory. Its specific gravity is about 4.2; when broken with a hammer while yet hot from its recent reduction, it shows a change of colours of purple, violet, and blue. In very intense heat it is volatilized. Most of the acids have a striking action on this metal. Nitric acid has little effect upon it. It is very oxydable by the muriatic acid. It is not attacked by the alkalies. Nitro-muriatic acid converts it into a white powder. Sulphuric acid when boiled upon it is partly decomposed. It is one of the most infusible metals. It does not combine with sulphur, but it may be united to phosphorus. It does not alloy with copper, lead, or arsenic; but combines with iron. See Chenevix's paper in Nicholson's Journal, v. 134, and Accum.



To the acidifiable metals, which have been some time known to the chemical world, we have to add one, of a more recent discovery, called Columbium, for which we are indebted to Mr. Hatchett, who discovered it in the year 1802. This accurate analyst, being engaged in examining and arranging some minerals in the British Museum, observed a specimen of ore which greatly resembled the Siberian chromate of iron. It appeared that the mineral in question was sent from the mines of Massachusetts in North America.

A very few facts respecting this metal have been ascertained. It is found to combine with oxygen, and of forming oxyds of different colours.

[ocr errors][merged small][merged small]

This metal has been lately discovered by Messrs. Bergelius and Heisinger of Stockholm, in a mineral from Bastnas, in Sweden, which had been supposed to be an ore of tungsten. This discovery has been since confirmed by the unquestionable testimony of Vauquelin, who, after a careful examination of the mineral, concurs in opinion that it contains the oxyd of an unknown metal. From the planet Ceres, discovered about the same period, it has been called cerium, and the mineral that contains termed cerite.

The tungsten of Bastnas, which is now called cerite, was found in the year 1750, in a copper-mine called Bastnas, or Saint-Gorans Koppargrufva, at RiddareHyltan, in Westmania, of which, with asbestos, it

formed the matrix: but after this time it was imbedded in quartz and mica, to the depth of seventeen toises.

Cerium appears to be susceptible of two degrees of oxydation. The alkalies precipitate a white oxyd from its solution, which is of a yellowish colour in the air, but, when perfectly dried, becomes dark. Exposed to a brisk and long continued fire, it takes a deep brickcolour. The oxalate and acetate of cerium, calcined in vessels not completely closed, yield a white oxyd, which, in an open fire, becomes of the colour of brick. It does not melt by itself.

Treated with borax by the blow-pipe, it melts readily and swells. The globule heated by the exterior flame assumes the colour of blood; which, by cooling, passes to a yellowish green, and at length becomes colourless, and perfectly transparent. Melted by the interior flame, these changes do not take place; it is then reduced into a colourless glass; but exposed for a short time in the exterior flame, the same phenomena are produced. If too much oxyd of cerium is made use of, the glass resembles an opaque yellowish enamel. These changes are more easily manifested with the phosphate of soda and ammonia. If two clear and colourless globules are melted together, one of which is prepared with borax, and the other with the phosphate, they form a transparent glass, which, on cooling, becomes opaque and pearl coloured.

These characters, taken together, sufficiently distinguish the oxyd of cerium from the oxyd of iron. The latter also affords the same changes of colour; but its glass, on cooling, has a deep green colour, which fades. The globules made with borax and the phosphate melt. ed together yield an opaque glass, the colour of which is a little deeper.

When oxyd of cerium is digested with sulphuric acid, these two substances unite, and the result is a red insoluble salt, which is sulphate of cerium at a maximum of oxydation. If the acid is concentrated, it scayce. ly dissolves any of it.

Treated with muriatic acid, the yellow acidulous sulphate of cerium yields part of its oxygen to the acid,


« PoprzedniaDalej »