The products of the photolysis of neutral aqueous solutions of 9,10-anthraquinone-2-sulfonate or of the action of Fenton's reagent on this quinone have been identified as 1- and 2-hydroxy- and dihydroxy-9,10-anthraquinone sulfonates. High quinone and low oxygen concentrations favor production of monohydroxy-anthraquinone sulfonates, while low quinone and high oxygen concentrations result in preferential formation of dihydroxylated derivatives of the quinone. Photolysis in aqueous NaOH solution gives essentially only 2-hydroxy-9,10-anthraquinone sulfonates.