The Collaborative International Dictionary of English v.0.48:

Mesitylene \Me*sit"y*lene\, n. (Chem.)
   A colorless, fragrant liquid, C6H3(CH3)3, of the benzene
   series of hydrocarbons, obtained by distilling acetone with
   sulphuric acid. -- Me*sit`y*len"ic, a.
   [1913 Webster]