S 1858 (OTTO) Sodium 3,5-dichloro-2-hydroxy benzene sulphonate Cas 54970-72-8 - used in conjunction with 4-aminoantipyrine (4-AAP) and hydrogen peroxide (H2O2) for chromogenic quantitation of peroxidase in coupled enzymatic reactions.1,2 Component of Trinder reagent for use with peroxidase to measure generation of hydrogen peroxide in automated systems.3,4