The Collaborative International Dictionary of English v.0.48:

Metacetone \Me*tac"e*tone\, n. [Pref. met- + acetone.] (Chem.)
   A colorless liquid of an agreeable odor, C6H10O, obtained
   by distilling a mixture of sugar and lime; -- so called
   because formerly regarded as a polymeric modification of
   acetone.
   [1913 Webster]