The dissolved oxygen in a water sample is generally estimated by modified Winkler method. Accordingly, approximately 200 ml volume of dissolved-oxygen-fixed solution shall be titrated with
1
Sodium thiosulphate reagent using soluble starch as an indicator
2
Sodium thiosulphate reagent using ferroin as an indicator
3
Ferrous ammonium sulphate reagent using soluble starch as an indicator
4
Ferrous ammonium sulphate reagent using ferroin as an indicator