The Collaborative International Dictionary of English v.0.48:

Alchemic \Al*chem"ic\, Alchemical \Al*chem"ic*al\, a. [Cf. F.
   alchimique.]
   Of or relating to alchemy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

alchemical
    adj 1: related to or concerned with alchemy [syn: alchemic,
           alchemical]