The Collaborative International Dictionary of English v.0.48:

Eikonogen \Ei*kon"o*gen\, n. [Gr. e'ikw`n, e'iko`nos, image +
   root of gi`gnesqai to be born.] (Photog. & Chem.)
   The sodium salt of a sulphonic acid of a naphthol,
   C10H5(OH)(NH2)SO3Na used as a developer.
   [Webster 1913 Suppl.]