Noun
a white powdered poisonous trioxide of arsenic; used in manufacturing glass and as a pesticide (rat poison) and weed killer
Source: WordNetArsenic forms colorless, odorless, crystalline oxides As 2 O 3 (" white arsenic ") and As 2 O 5 which are hygroscopic and readily soluble in water to form acidic solutions. Source: Internet
Shortly thereafter, he died of white arsenic poisoning, according to a legend - because of his sister. Source: Internet