Calibration of Na_2S_2O_3 Standard Solution by Coulometric Titration

Concentration of Na2S2O3 standard solution was determined by coulometric titration.During determination,mixed liquid of 1 mol/L KI and 1 mol/L H3PO4(1︰1) was used as the electrolyte,I2 from electrolysis process reacted with Na2S2O3,the titration end-point was controlled by dead-stop method.The results show that the determination data with above method is consistent with result of common titration analysis,precision of the method can reach to 0.1%.This method is rapid and accurate,and it can be used to detect Na2S2O3 standard solution concentration instead of the common titration analysis.