Iodometric titration analysis for SrFe1-xCoxO3-δ (x = 0, 0.2, 0.4, 0.6, 0.8)

The determination of oxygen nonstoichiometry in the series of SrFe1-xCoxO3-δ (x = 0, 0.2, 0.4, 0.6, 0.8) compounds was carried out using the iodometric titration method.
The procedure steps were as following: (1) purging the flask with argon for 20 minutes to remove air, after which the powdered material (15-20 mg), along with KI (0.2 g), was dissolved in 2 M hydrochloric acid; (2) 0.01 M Na2S2O3 was added to the solution; (3) 1 wt.% starch water solution was incorporated towards the end of the titration.
The amount of I3- ions released was evaluated based on the volume of sodium thiosulfate used in the titration, which allowed for the determination of oxygen nonstoichiometry.