Quenching of the second excited singlet state of xanthione in inert, nonpolar perfluoro-1,3-dimethylcyclohexane has been studied using picosecond time-resolved fluorescence decay methods.
Fractionally distil it, then 35mL are sealed with about 7g KOH pellets in a borosilicate glass ampoule and heated at 135o for 48hours. The ampoule is cooled, opened, and the liquid is resealed with fresh KOH in another ampoule and heated as before. This process is repeated until no further decomposition is observed. The substance is then washed with distilled water, dried (CaSO4) and distilled. [Grafstein Anal Chem 26 523 1954, Beilstein 5 III 378.] IRRITANT.