The degradation of methyl orange (MO) served as a secondary measure of determining the extent of the Fenton reaction through visible spectroscopy. To detect the presence of hydroxyl radicals, MO was added to the solution and its absorbance was measured over time. MO rapidly reacts with hydroxyl radicals to form organic acids Though MO is not a DNA base, its degradation demonstrates the reactivity of hydroxyl radicals in the presence of organic molecules.