In the microscale oxidation of a Xylene to a Phthalic Acid, 825 mg potassium permanganate, 100 mg sodium carbonate, 3 mL water were put in flask and warmed then 125 microliters of unknown xylene and 10 mg detergent were refluxed for 45 minutes. Then we added sodium bisulfite until the purple color was gone for one step. What is the role of sodium bisulfite in such a procedure?