Assay of high-purity sodium oxalate traceable to the international system of units by coulometric titration and gravimetric titration

Reliability in Standardization of Iron(III) and Titanium(III) Solutions in Volumetric Analysis

“…The indicator current proportionally decreased with the titration proceeding near the end point and the current was kept at zero amperes after the end point. The end point was the intersection between the linear regression curve of indicator currents versus the amounts of the sodium thiosulfate solution used and the baseline (0 μA) …”

“…The end point was detected by potentiometry with a Pt–Ag/AgCl combination electrode. The inflection point calculated by third-order polynomial approximation was decided as the end point …”

“…The end point was the intersection between the linear regression curve of indicator currents versus the amounts of the sodium thiosulfate solution used and the baseline (0 μA). 22 Experimental Procedure−Iron(III) with Titanium(III). An approximately 250 mol kg −1 solution of titanium(III) sulfate was prepared by diluting a titanium(III) sulfate solution (20% in 1 to 4% sulfuric acid) two times with 2 mol L −1 sulfuric acid.…”

“…The inflection point calculated by third-order polynomial approximation was decided as the end point. 22 Approximately 1.6 g of ammonium iron(III) sulfate dodecahydrate was placed in a 50 mL beaker and dissolved with 20 mL of 2 mol L −1 sulfuric acid. The iron(III) solution was gravimetrically titrated with the titanium(III) solution on heating around 50 °C.…”