M 2246 (OTTO) Methyl thymol blue sodium salt Cas 1945-77-3 - used as thymol-containing organic dye. M 2246 (OTTO) Methyl thymol blue sodium salt Cas 1945-77-3 - used as an indicator for complexometry. M 2246 (OTTO) Methyl thymol blue sodium salt Cas 1945-77-3 - used in determination of sulfate in rainwater.