citrination
/sɪtrɪˈneɪʃn/Alchemy. Now historical
noun
The turning of a substance (especially silver) yellow in colour, supposed to indicate a stage of greater perfection or transformation (into gold).
Origin
Late Middle English; earliest use found in Geoffrey Chaucer (c1340–1400), poet and administrator. From post-classical Latin citrination-, citrinatio from citrinat-, past participial stem of citrinare to turn yellow + classical Latin -iō.