Simultaneous Determination of Sodium Azide and Alkali Halides in Their Mixtures by Short-circuit Amperometric Titration

Abstract

The argentometric titration of azide ions by the short-circuit amperometric technique using a rotating platinum wire electrode (1000 rpm), and the differential titration of azide and halide ions have been studied. Potassium nitrate, sodium nitrate or sodium acetate is suitable for the supporting electrolyte. Azide ion in the presence of O. O^2-% gelatin can be determined at its concentrations from O.0001 to 0.01 moll/. The determination is the most precise at the concentration of 0.01 mol//; either the relative error or the variation coefficient is less than 0.1%. The whole procedure requires only 10 minutes.
A recommended procedure for the differential titration of azide and halide ions is as follows. Potassium nitrate and gelatin are added to a mixed solution of sodium azide and one of halides (sodium chloride, potassium bromide, and potassium iodide). The solution is diluted so that the concentrations are made 0.1 moll/ in potassium nitrate and 0. O^2-% in gelatin. The titration at the potential of SCE with 0.1 moll/ silver nitrate gives the sum of azide and halide ions. The content of latter can be found by titrating an aliquot of the sample solution up to the end-point for halide, the pH of which is previously adjusted below 2 with nitric acid. The relative errors are about 0.9% for 0.005 mol/l sodium azide and about 0.5% for 0.0O^2- mol/l sodium chloride.