Precise coulometric titration of antimony(III) in a highly acidic solution

Abstract

The accuracy of the coulometric titration of antimony(III) in 3 mol dm^–3 hydrochloric acid by electrogenerated iodine was studied. It was considered how to add antimony(III) to an electrolyte solution. The Dependencies of the titration results on the pH value of the electrolyte solution, the electrolysis current, the delay time between sampling and starting the electrolysis, and the amount of antimony(III) were measured. The accuracy of the coulometric titration reached a high level, limited by the uncertainty (0.02%) of the relative atomic mass of antimony. Moreover, with arsenic(III) oxide of known purity, no systematic error in the coulometric titration system was ascertained.