The Collaborative International Dictionary of English v.0.48:

Citrination \Cit`ri*na"tion\, n. [See Citrine.]
   The process by which anything becomes of the color of a
   lemon; esp., in alchemy, the state of perfection in the
   philosopher's stone indicated by its assuming a deep yellow
   color. --Thynne.
   [1913 Webster]