Notes on the Use of Rare Metals

The Manufacturer and Builder 7, 1876

See page 142 on our June number.

Palladium. - This metal is of great value in preventing silver from tarnishing. When from 15 to 25 per cent of palladium is united with silver, the compound metal may be exposed to any of those chemical agents which blacken silver, without effect. In this way any metal may be protected, and thus palladium will be of great value in many departments of manufacture.

Rhodium. - Some of the salts of rhodium are of a most beautiful red. A solicate of the oxid of rhodium is used to give to glass a fine ruby red, which is as beautiful as that imparted by gold.

Uranium. - The oxid of uranium, when pure, produces a beautiful delicate yellow; but it often contains oxid of iron, and this gives a greenish hue to the glass, which however is not unpleasant. Uranium is generally obtained from a mineral called pitchblende, which is a mixture, in uncertain proportions, of the oxid of uranium, of galena, and of iron pyrites, and the sulphuret and carbonate of copper. Having procured a solution of the nitrate of uranium, the oxid is precipitated as a yellow powder by ammonia, and after being well washed with soft water, it is in a state of purity.

Vanadium. - This metal was first discovered in the slags of teh reducing furnaces of Tabery, in London, and still more in a peculiar lead ore; it is of a silvery luster. Its oxid is occasionally used in giving green color to glass.

Cadmium, which was discovered in some ores of zinc, in 1817, yields an oxid and sulphid of an extremely beautiful orange yellow, of great permanency.

Tungsten. - This metal, which is of an iron-gray color, exists largely in nature, in combination with lime and with iron. In the tin and copper mines of Cornwall, England, it is sometimes found intermixed in such quantities with the tin ores, as to have formerly reduced their market value, wing to the difficulty of separating the tungsten by any process of smelting; later a method was discovered by which the tungsten was separated with great advantage from the tin ores, and xonsequently large quantities of the tungstate of soda, and the oxid of tungsten, (a pale yellow powder,) was formed.

Silver. - As a color, this metal is rarely employed, on account of its liability to change under the action of light. In photography nearly all the sensitive surfaces are produced by salts of silver. The chlorid changes with rapidity from white to gray, and eventually to black, and even the dark olive oxid is, after short time, turned black, with a metallic luster, owing to the separation of the pure metal. In the manufacture of porcelain and glass, the chlorid of silver, produced by adding common salt to a solution of silver in nitric acid, is employed in combination with the salts of gold, to give greater delicacy and variety to the carmines and purples. The utmost precaution must be observed to protect the chlorid of silver from all light during the process of drying, and also to free it from every trace of copper, with which the silver of commerce is frequently alloyed, since the presence of any darkened chlorid, or of any oxid of copper, interferes with the production of the beautiful carmines and purples which may be obtained by its mixture with the purple of Cassius. The processes of preparing silver for silvering, are like those employed for similar preparations from gold and platinum. Silver is used by the glass manufacturer to produce some of the yellow colors, such as used in window-glass.

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