Molybdate of Lead Enlarge
Dec 1. 1811 published by Jas Sowerby London.
Exotic Mineralogy
Plumbum molybdatum

Molybdate of Lead

  • Syn.
    • Mine de plomb jaune. De Lisle 3. 387.
    • Gelbes bleierz. Emmerl. 2. 403.
    • Plomb en oxide mineralizé par l’acide molybdique. Daub. Tabl. 44.
    • Yellow molybdenated lead ore. Kirw. 2. 213.
    • Plomb molybdaté. Haüy 3. 498. Tabl. 83.

This is usually brought from Bleyberg in Carinthia. It is also said to be found at Sarka in the Bannat, near Freyberg in Silicia, and in France. The specimen here figured is from Bleyberg, and is in the British Museum. The crystals are somewhat opaque, waxy, or like manufactured brimstone, in the dullish yellow colour they generally possess. They are brittle, with sharp edged lamellar fragments; may be easily scratched with a pin. The gangue is a compact Limestone.

Molybdate of Lead is soluble in Nitric acid, and in the Alkalies, also in Muriatic acid, and decomposed by it, it gives a blue tint to hot Sulphuric acid; by the blow-pipe it melts into a yellowish grey mass, and globules of lead are produced. Spec. Grav. 5.486 to 5.706. The primitive form of the crystal, according to Haüy, is a rectangular octaëdron, one pyramid measuring upon the other 76° 70′, but the Count de Bournon considers it to be a rectangular prism. See three varieties in the lower figures. Klaproth first made us acquainted with the constituents of this ore, and found it to contain

Oxide of Lead 64.42
Oxide of Molybdenun 34.25

Our countryman and good friend Charles Hatchet, Esq. completed a most accurate analysis; see Phil. Trans, vol. 86, page 323. The quantity he employed was 250 Grains, which yielded

Oxide of Lead 146  
Molybdic Acid 95  
Oxide of Iron 5.2
Siliceous Earth 0.7
Loss 3.1

The yellow phosphate of Lead from Scotland, has been confounded with the Molybdate of Lead, but may be detected by the blow-pipe.

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