Modifications of the kinetic method of thiocyanate determination by Landolt reaction of methyl orange with potassium bromated

Various modifications of the kinetic method have been studied in order to optimize the conditions of Landolt reaction of methyl orange with potassium bromate, used for determination of thiocyanate in aqueous solution (fixed time method, induction period measurement, tangent method, and differential curves of two kinds). Tangent method offers some advantages. Optimal conditions are: 0.28 M HCl, pH 1.02, 8•10 -5 М KBrO 3, 10 mg/L methyl orange. Calibration curve is linear in (0.2-7)•10 -5 M range, reproducibility is 4.0 %, relative error is 4.1 %.