Abstract:

Four experimental methods, including two double-indicator methods, the BaCl₂ method and the potentiometric titration method were developed for determining the mass concentration (Mass of components in unit volume of solution) of NaOH, Na₂CO₃ and NaHCO₃ in two types of industrial mixed alkali solutions, i.e., solutions I (NaOH + Na₂CO₃) and II (Na₂CO₃ + NaHCO₃). Errors and standard deviations of the four analytical methods were calculated and compared based on the measurements. Significance tests were also performed on the results of the four methods, and possible factors/causes that led to poor accuracy and significant differences were also discussed. It was concluded from the experimental results that the potentiometric titration offered the highest accuracy and precision, whereas the BaCl₂ method suffered from the lowest accuracy and precision from among the four methods. The results also showed significant differences between the BaCl₂ method and the other three methods. This paper not only provides a reference for the accurate determination of each component in industrial bases, but also supplies a comprehensive experimental protocol for acid-base titration teaching experiments.

Key words: Mixed base, Double indicator method, BaCl₂ method, Potentiometric titration method, Significance test, Comprehensive experimental design