Preparation and Standardization of Sodium Thiosulphate 0.1 M with potassium bromate
Preparation: Dissolve 25 g of sodium
thiosulphate and 0.2 g of sodium carbonate in carbon dioxide-free water and dilute to 1000 ml with the same solvent.
Standardise the solution in the following manner.
Standardization: Dissolve 0.200 g of potassium bromate, weighed accurately,
in sufficient water to produce 250.0 ml. To 50.0 ml of this solution add 2 g of potassium iodide and 3 ml of 2 M
hydrochloric acid and titrate with the sodium thiosulphate solution using starch solution, added towards the end of the titration, as indicator until the blue colour is discharged.
Re-standardise the solution frequently.
1 ml of 0.1 Msodium thiosulphate is equivalent to 0.002784 g of potassium bromate.