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| Arsenic
Arsenic has been found in Nature since Antiquity. Aristotle makes reference to sandarach (arsenic trisulfide) in the 4th century B.C. In the 1st century A.D., Pliny stated that sandarach is found in gold and silver mines and arsenic (arsenic trioxide) is composed of the same matter as sandarach. By the 11th century three species of arsenic were known, the white, yellow and red - since then recognized as arsenic trioxide, arsenic trisulfide (orpiment) and arsenic disulfide (realgar), respectively. (reference) Albertus Magnus is reputed in the 13th century to be the discoverer of metallic arsenic. However, his documentation is considered vague. It was not until 1649 that J. Schroder clearly reported the preparation of metallic arsenic by reducing arsenic trioxide with charcoal. Thirty-four years later, N. Lemery also observed that metallic arsenic was produced by heating arsenic trioxide with soap and potash. By the 18th century the properties of metallic arsenic were sufficiently known to classify it as semimetal. Toxic Elements: Arsenic, Beryllium, Cadmium, Chromium, Cobalt, Copper, Fluorine, Lead, Mercury, Nickel
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