The Collaborative International Dictionary of English v.0.48:

Tridecatoic \Tri`dec*a*to"ic\ (tr[-i]`d[e^]k*[.a]*t[=o]"[i^]k),
   a. [Pref. tri- + Gr. de`katos tenth.] (Chem.)
   Of, pertaining to, or designating, that acid of the fatty
   acids heterologous with tridecane. It is a white crystalline
   substance.
   [1913 Webster]