Arsenic

Arsenic is a chemical element in the periodic table that has the symbol As and atomic number 33. This is a notorious poisonous metalloid that has three allotropic forms; yellow, black and grey. Arsenic and its compounds are used as pesticides, herbicides, insecticides and various alloys.

Applications

Lead arsenate has been used, well into the 20th century, as an herbicide on fruit trees (resulting in neurological damage to those working the sprayers), and copper arsenate has even been recorded in the 19th century as a coloring agent in sweets. In the last half century, monosodium methyl arsenate (MSMA), a less toxic organic form of arsenic, has replaced lead arsenate's role in agriculture.

Related Topics:
Lead - 20th century - Herbicide - Fruit tree - Copper - 19th century

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The application of most concern to the general public is probably that of wood which has been treated with copper arsenate ("CCA", or "Tanalith", and the vast majority of older "pressure treated" wood). CCA timber is still in widespread use in many countries, and was heavily used during the later half of the 20th century as a structural, and outdoor building material, where there was a risk of rot, or insect infestation in untreated timber. Although widespread bans followed the publication of studies which showed low-level leaching from in-situ timbers (such as children's playground equipment) into surrounding soil, the most serious risk is presented by the burning of CCA timber. Recent years have seen fatal animal poisonings, and serious human poisonings resulting from the ingestion - directly or indirectly - of wood ash from CCA timber (the lethal human dose is approximately 20 grams of ash - roughly a tablespoon). Scrap CCA construction timber continues to be widely burnt through ignorance, in both commercial, and domestic fires. Safe disposal of CCA timber remains patchy, and little practiced, there is concern in some quarters about the widespread landfill disposal of such timber.

Related Topics:
Wood - Copper arsenate - 20th century - Building material

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During the 18th, 19th, and 20th centuries, a number of arsenic compounds have been used as medicines, including arsphenamine (by Paul Erlich) and arsenic trioxide (by Thomas Fowler).

Related Topics:
Arsphenamine - Arsenic trioxide

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Arsphenamine as well as Neosalvarsan was indicated for syphilis and trypanosomiasis, but has been superseded by modern antibiotics.

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Arsenic trioxide has been used in a variety of ways over the past 200 years, but most commonly in the treatment of cancer. The FDA in 2000 approved this compound for the treatment of patients with acute promyelocytic leukemia that is resistant to ATRA.{{an|ArsTriChemo}}

Related Topics:
FDA - Acute promyelocytic leukemia - ATRA

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Other uses;

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• Various agricultural insecticides and poisons.
• Gallium arsenide is an important semiconductor material, used in integrated circuits. Circuits made using the compound are much faster (but also much more expensive) than those made in silicon. Unlike silicon it is direct bandgap, and so can be used in laser diodes and LEDs to directly convert electricity into light.
• Arsenic trioxide is used in Australia for treating termite infestations in houses.
• Also used in: bronzing, pyrotechny