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Arsenic trioxide facts for kids

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Arsenic trioxide
Arsenic trioxide

Arsenic trioxide, also known as white arsenic, arsenic(III) oxide, or arsenious oxide, is a chemical compound. Its chemical formula is As2O3. It has arsenic and oxide ions in it. The arsenic is in its +3 oxidation state.


Arsenic trioxide is a white solid. It dissolves in water to make an acidic solution of arsenious acid. It dissolves easily in bases to make arsenites. It reacts with concentrated hydrochloric acid to make arsenic trichloride. It reacts with very strong oxidizing agents to make arsenic pentoxide. It reacts with reducing agents to make arsenic or arsine. It sublimes much easier than metal oxides, making it easy to separate by heating the mixture.

Occurrence and preparation

Arsenic trioxide is rarely found as a mineral. It is normally made from orpiment or realgar, arsenic sulfide minerals. About 50,000 tons of arsenic trioxide are made each year. Arsenic trioxide is made by burning arsenic in air, reacting arsenic with concentrated sulfuric acid, or the roasting of arsenic sulfide ores.


It is used to make elemental arsenic. It was used as a pigment (in Paris green) and as a wood preservative but was banned in many countries because it is so toxic. Arsenic trioxide is used to fight cancer.


Arsenic trioxide is highly toxic when eaten. It also can be toxic if on the skin for long amounts of time. It affects the digestive system when eaten. Workers exposed to arsenic trioxide fumes in their job can be poisoned as well.

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Kids robot.svg In Spanish: Óxido de arsénico (III) para niños

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