Abstract: The article describes a method of simultaneous determination of micro phosphorus and arsenic by differential reaction-rate method. The proportional coefficients of K_3min(P),K_3min(As), K_9min(P) and K_9min(As) in solutions containing 0.3755mol·L^-1 of sulphuric acid and 0.4% ammonium molybdate at 65℃ are reported. The method described is suitable for simultaneous determination of phosphorus and arsenic in a ratio of (P:As) more than 1.5. The relative error and relative standard deviation are within 1.0%.

Key words: Differential reaction-rate method, A method of proportional equation, Determination of micro phosphorous and arsenic