A 2497 (OTTO) Anthraquinone-2-sulphonic acid sodium salt, monohydrate, GR 98% Cas 153277-35-1 - used as a catalyst in production of alkaline pulping in the soda process. A 2497 (OTTO) Anthraquinone-2-sulphonic acid sodium salt, monohydrate, GR 98% Cas 153277-35-1 - used as an in situ photochemical fluorescence probe.