Medical Definition of arsenic trioxide
: a poisonous trioxide of arsenic As2O3 or As4O6 that is administered intravenously to treat some forms of leukemia and in minute doses is used as a homeopathic remedy ◆Arsenic trioxide is typically obtained as a by-product from the roasting of arsenic-containing ores and is used especially as a rodenticide and weed killer. —called also arsenic, arsenious acid, arsenious oxide, white arsenic
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