As shown in Figure , a pH range of 2.0 -4.0 was determined to be a viable range for significant production of iron(III) through the Fenton reaction. A pH of 2.0 was determined to be ideal for the highest production of Fe 3+ ions while a pH of 3.0 was determined to be ideal for the highest production of hydroxyl radicals. This discrepancy can be explained by the reaction between protons and hydroxyl radicals. In highly acidic solutions, these radicals are "scavenged" by hydrogen ions . This can explain the difference in optimal pH values between the two methods.