dumasin

from The Collaborative International Dictionary of English v.0.48

Mesityl \Mes"i*tyl\, n. (Chem.)
   A hypothetical radical formerly supposed to exist in mesityl
   oxide.
   [1913 Webster]

   {Mesityl oxide} (Chem.), a volatile liquid having the odor of
      peppermint, obtained by certain dehydrating agents from
      acetone; -- formerly called also {dumasin}.
      [1913 Webster]