Dissolve 25 g of sodium thiosulphate and 0.2 g of sodium carbonate in sufficient carbon dioxide-free water to produce 1000 ml.
To 20 ml of 0.0167M potassium bromate VS add 40 ml of water, 10 ml of potassium iodide solution and 5 ml of 7M hydrochloric acid. Titrate with the sodium thiosulphate solution using 1 ml of starch solution, added towards the end of the titration, as indicator. Each ml of 0.1M sodium thiosulphate VS is equivalent to 2.784 mg of KBrO3.
Perform a duplicate and calculate the molarity factor (MF)
Note down the average value
1) Restandardise before use
2) Discard the solution after 30 days.
3) For storage and labeling follow the general procedure.