Macro and semimicro determination of inorganic bromide by cerium(IV) oxidimetry

Aqueous solutions containing 1-200 mg of inorganic bromide in 25-100 ml of solution are quantitatively analysed at room temperature by direct titration with ammonium hexanitratocerate(IV) in 2M perchloric acid. The titration medium is perchloric acid at a concentration of at least 4M. End-points are determined from potentiometric (Pt vs. S.C.E. electrodes) titration plots, the potential break at the end-point being 300 mV. Iodide up to at least 0.02N and sulphate up to 0.01N do not interfere. Chloride depresses the end-point potential break but a satisfactory titration curve is still obtained in the presence of 0.04N chloride. Standard deviations are +/- 0.068 mg of bromide in the 1- to 20-mg range [0.02M cerium(IV) titrant] and +/- 0.45 mg of bromide in the 20- to 200-mg range [0.1M cerium(IV) titrant].