Arsenic trioxide can be generated via routine processing of arsenic compounds including the oxidation (combustion) of arsenic and arsenic-containing minerals in air. Illustrative is the roasting of orpiment, a typical arsenic sulfide ore.
- 2 As
2S
3 + 9 O
2 → 2 As
2O
3 + 6 SO
2
Most arsenic oxide is, however, obtained as a volatile by-product of the processing of other ores. For example, arsenopyrite, a common impurity in gold- and copper-containing ores, liberates arsenic trioxide upon heating in air. The processing of such minerals has led to numerous cases of poisonings,[18] and after the mine is closed, the leftover trioxide waste will present environmental hazard (as was the case with the Giant Mine, for example). Only in China are arsenic ores intentionally mined.[9]
In the laboratory, it is prepared by hydrolysis of arsenic trichloride:[19]
- 2 AsCl3 + 3 H2O → As2O3 + 6 HCl
As
2O
3 occurs naturally as two minerals, arsenolite (cubic) and claudetite (monoclinic). Both are relatively rare secondary minerals found in oxidation zones of As-rich ore deposits. Sheets of As2O3 stand for part of structures of the recently discovered minerals lucabindiite, (K,NH4)As4O6(Cl,Br),[20] and its sodium-analogue torrecillasite.[21]
https://en.wikipedia.org/wiki/Arsenic_trioxide
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