Plumbum sulphatum Enlarge
June 1. 1808. Publish’d by Ja.s Sowerby. London.
British Mineralogy
CCLXX
Plumbum sulphatum

  • Class 3. Metals.
  • Order 1. Homogeneous.
  • Div. 3. Amorphous.

This curious, apparently new, decomposition of Galæna is so remarkable in its property of burning with a blue flame, like Sulphur, that it seems a prodigy, and has from that circumstance been called inflammable Lead Ore.

The upper figure shows some remains of the cubic forms of the Galæna, the outside having been so affected as to have blunted and in some parts obliterated the angles.

The lower specimen is more compact, and is striated with more or less zigzag lines, and has a few blotches of Galæna about it. The outside is generally whitish with a granular texture passing to crystallization. Inwardly it is generally somewhat darker and often of a dense gray, with a horny appearance and flinty fracture. It shines upon being slightly rubbed with the finger nail, and may be easily scraped.

As this substance is scarcely known, of course there is no analysis recorded. Having examined it by the blowpipe, we annex a short account of the changes it underwent. A piece being laid on Charcoal, and the flame gently applied by the blowpipe, it became red-hot, the Sulphur sublimed from the interior and melted with a greasy aspect, and a trifling blue flame, leaving the substance rather lighter in colour when cold. On further urging the flame, white Sulphate of Lead appeared on the surface which bubbled and blistered, and on cooling showed some signs of facets and spiculæ. After a while it was reduced to a globule of Lead. On further examination we find it to be composed of Sulphate of Lead, and about 10 per cent. of Sulphur.

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