Cacodyl
Cacodyl, dicacodyl, tetramethyldiarsine, alkarsine or minor part of the "Cadet's fuming liquid" (after the French chemist Louis Claude Cadet de Gassicourt) (CH3)2As—As(CH3)2 is a poisonous oily liquid with a garlicky odor. Cacodyl undergoes spontaneous combustion in dry air.