arsenic trioxide

noun

ar·​se·​nic trioxide ˌärs-nik-, -ᵊn-ik- 

: 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

Note: 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