Dissolve 25 gm of sodium thiosulphate and 200 mg of sodium carbonate in carbon dioxide-free water to produce 1000 ml. Standardize the solution in the following manner
STANDARDISATION (TRIPLICATE)
Weigh accurately about 0.2 gm. of potassium bromate and dissolve sufficient water to produce 250 ml. To 50 ml. of this solution add 2 gm. of Potassium Iodide and 3 ml. of 2M Hydrochloric acid and titrate with 0.1M sodium thiosulphate solution using starch solution added towards the end of the titration, as an indicator until the blue colour is discharged to end-point
Every 1 ml of 0.1M sodium thiosulphate is equivalent to 0.002784gm of KBrO3
Calculation
Wt. of potassium bromate(mg) × 50 x Potency of potassium bromate× 0.1
Molarity = ------------------------------------
Volume consumed (ml) x 2.784 x 250 × 100
SODIUM THIOSULPHATE (0.001M)
PREPARATION
Take 10 ml 0.1M of sodium thiosulphate in a 1000 ml volumetric flask and produce 1000 ml with carbon dioxide-free water. Standardize the solution in the following manner
STANDARDISATION (TRIPLICATE)
Weigh accurately about 0.05 gm. of potassium bromate and dissolve sufficient water to produce 500 ml. To 10 ml. of this solution add 2 gm of Potassium Iodide and 3 ml. of 2M hydrochloric acid and titrate with 0.001M sodium thiosulphate solution using starch solution added towards the end of the titration, as an indicator until the blue colour is discharged to a blue coloured end-point
Each 1 ml of 0.001M sodium thiosulphate is equivalent to 0.00002784gm of KBrO3.
Calculation
Wt. of potassium bromate(mg) x 10 x Potency of potassium bromate ×0.001
Molarity = -----------------------------------
Volume consumed (ml) x 0.02784 x 500 × 10