MOLYBDENUM is a metal of a grey ish white colour, in the form of brittle in fusible grains. Formerly two substances were confounded together, which being examined by the industrious and accurate Scheele, he gave to the one the name of Plumbago, which is composed of carbon and iron; the other he called molybde num. In colour it resembles lead, but in the analysis was obtained sulphur, and a whitish powder, which possesses the pro perties of an acid. This, Bergman sus pected to be a metallic oxide, which has since been demonstrated to be the case. Hitherto this metal is only obtained in grains, the greatest heat has not been suf ficient to melt it into a button; its speci fic gravity is 7.4. When exposed to heat in an open vessel, it gradually combines with oxygen, and is converted into a white oxide, which is volatilized in small brilliant needle form crystals. This oxide, having the properties of an acid, is called the molybdic acid.
Molybdenum is capable of combining with four different proportions of oxygen, and of forming four oxides, the black, the blue, the green, and the yellow or white. To the green is given the name of molybdous acid. It combines readily with
sulphur, and in that state it is called mo lybdena, the sulphuret of molybdenum. This may be formed by distilling together one part of molybdic acid and five parts of sulphur. It will also combine with phosphorus. Muriatic acid has but little effect on the metal ; but it dissolves the oxide. Molybdenum will unite with many of the metals, forming with them alloys.
Molybdena, or sulphuret of molybde dum, occurs massive, disseminated, and rarely crystallized. Its colour is like that of fresh cut metallic lead. It occurs in granular distinct concretions; it is opaque, stains the fingers, leaves shining traces when drawn over paper ; it is very soft, and easily divisible in the direction of its laminz. Specific gravity 4.5 to 4.7. It is infusible before the blow-pipe, but ex hales a sulphureous odour; at a very high beat it melts, gives out white fumes, and burns with a blue flame : it consists of Molybdic acid - - - - 45 Sulphur 55 100 It is found in Norway, Sweden, Saxony, and in Mount-Blanc in Switzerland.