The Collaborative International Dictionary of English v.0.48:

Allotropic \Al`lo*trop"ic\ ([a^]l`l[-o]*tr[o^]p"[i^]k),
Allotropical \Al`lo*trop"ic*al\ (-[i^]k*al), a. [Cf. F.
   allotropique.]
   Of or pertaining to allotropism. -- Al`lo*trop"ic*al*ly,
   adv.
   [1913 Webster]

   Allotropic state, the several conditions which occur in a
      case of allotropism.
      [1913 Webster]