Cadet's fuming liquid was a red-brown oily liquid prepared in 1760 by the French chemist Louis Claude Cadet de Gassicourt (1731-1799) by the reaction of potassium acetate with arsenic trioxide.[1] It consisted mostly of dicacodyl (((CH3)2As)2) and cacodyl oxide (((CH3)2As)2O). The reaction for forming the oxide was something like: