Determination of major components in industrial sodium hydroxide by automatic potentiometric titration

An automatic potentiometric titration method was established for the determination of sodium hydroxide and sodium carbonate in industrial sodium hydroxide.The titration mode,main titration parameters and the judgment of equivalent point were tested and selected.Under the dynamic titration mode of automatic potentiometric titrator,the optimized main titration parameters were: minimum increasing volume of 30 μL,measurement point density of 4 and signal shift criterion of 50 mV/min.The equivalent points at pH 8-9 and pH 5 were used to evaluate the trueness of this method.The manual titration operation was replaced by automatic potentiometric titrator.The determination results of sodium hydroxide and sodium carbonate in industrial sodium hydroxide were consistent with the GB method and dual-indicator method.The relative standard deviations(RSD,n=5) for sodium hydroxide and sodium carbonate were 0.03 %-0.05 % and 0.74 %-0.90 %,respectively.The recovery rate of sodium carbonate was 99.0 %-100.5 %.