- an orange-red, crystalline, water-insoluble solid, C20H12O5, that in alkaline solutions produces an orange color and an intense green fluorescence: used to trace subterranean waters and in dyes.
- an orange-red crystalline compound that in aqueous solution exhibits a greenish-yellow fluorescence in reflected light and is reddish-orange in transmitted light: used as a marker in sea water and as an indicator. Formula: C 20 H 12 O 5
