Determination of Cl- and SO42- in Boric Acid

Abstract

Microcontents of Cl- and SO42- in boric acid were determined by photoelectricity turbidimetry with acid as medium. The effects of stabilizer, acidity of solution, content of precipitant, heating time and temperature as well as measuring time on the turbidity of the solution were studied. After above experiment parameters were optimized, in the measurements to determine SO42- in boric acid, the stabilizer was glycerine-ethanol (1:4), the precipitant was acidic BaCl2. The solution was shaked and heated, as a result, the adding sequence of reagents had no effects on results. The detection limit was 0.10mg/L, relative standard deviation (RSD) was less than 3%, recovery rate was 98.85%~103.00%, and measuring time last over 40min. SO42- concentration in the range of 0.33 mg/L ~0.83mg/L showed a linear relationship with turbidity. In the determination of chlorine, the stabilizer was glycerine, measuring time held in 40min, detection limit was 0.03mg/L, RSD was less than 4%, and recovery rate was 102.2%~106.5%. Cl- concentration in the range of 0.10 mg/L ~0.25mg/L showed a linear relationship with turbidity. Photoelectricity turbidimetry improve the precision and accuracy of the measurements. The method of turbidimetry to determine Cl- and SO42- in boric acid is simple, reliable, innocuous and applicable in practice.