The Collaborative International Dictionary of English v.0.48:

Croconic \Cro*con"ic\ (kr?-k?n"?k), a. [Gr. ???? saffron.]
   1. Of, pertaining to, or resembling saffron; having the color
      of saffron; as, croconic acid.
      [1913 Webster]

   2. Pertaining to, or derived from, croconic acid.
      [1913 Webster]

   Croconic acid (Chem.), a yellow crystalline substance,
      C5O3(OH)2, obtained from potassium carboxide, rhodizonic
      acid, and various phenol and quinone derivatives of
      benzene, and forming yellow or orange colored salts.
      [1913 Webster]