Arsenic+Trioxide


 * Arsenic trioxide** is the [|inorganic compound] with the [|formula] As2O3 . This commercially important [|oxide] of [|arsenic] is the main precursor to other arsenic compounds, including [|organoarsenic compounds]. Approximately 50,000 [|tonnes] are produced annually. Many applications are controversial given the high toxicity of arsenic compounds.

Arsenic trioxide can be generated via many 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 As2S3 + 9 O2 → 2 As2O3 + 6 SO2 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.[|[][|4][|]] Only in China are arsenic ores intentionally mined.[|[][|3][|]] Arsenic trioxide is an [|amphoteric] oxide, and its aqueous solutions are weakly [|acidic]. Thus, it dissolves readily in alkaline solutions to give [|arsenites]. It is less soluble in acids, although it will dissolve in [|hydrochloric acid], giving chloro compounds, ultimately [|arsenic trichloride] with concentrated acid. Only with strong [|oxidizing agents] such as [|ozone], [|hydrogen peroxide], and [|nitric acid] does it give [|arsenic pentoxide], As2O5. Reduction gives elemental arsenic or [|arsine] ( AsH3 ) depending on conditions. In this regard, arsenic trioxide differs from phosphorus trioxide, which readily combusts to [|phosphorus pentoxide].