The Oxidation of Hydrogen Sulphite Ions by Potassium Iodate

3 The oxidation of hydrogen sulphite ions by potassium iodate 

Here iodate is reduced by sulphite to give iodide which is oxidised by iodate which is reduced to iodide by sulphite. 

Prepare a solution 0.02 M in potassium iodate (A) and another solution 0.02 M in sodium hydrogen sulphite (B). Mix the following suggested volumes of A and B and msdce up to 100 cm (where applicable), adding a few drops of 1% starch solution. 

Place each mixture in a shaking thermostat at 25 C (or a large 2-4 dm beaker containing water at room temperature) as quickly as possible after mixing and note the time on a stopwatch when the blue colour of iodine/starch adsorption complex appears. Plot the time against l/[A][B]. 

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