What is "arsenic trichloride"

n. (context inorganic compound English) A colourless oily liquid, AsCl₃, used in the synthesis of organic arsenic compounds

Arsenic trichloride is an inorganic compound with the formula AsCl, also known as arsenous chloride or butter of arsenic. This poisonous oil is colourless, although impure samples may appear yellow. It is an intermediate in the manufacture of organoarsenic compounds.