Volumetric Determination of Chlorate

Pipette 25.0 cm of 0.05 M potassium chlorate solution into a conical flask provided with a stopper. Add 3 cm conc.HCl followed by two portions of 0.3 g sodium 

The reaction between iodate and iodide in acid solution produces iodine according to  

The iodine reacts with thiosulphate according to l2+2S203 - S406 +2I  

When an excess iodide and an excess thiosulphate are added to an iodate solution, the latter can be titrated against an acid using an acid base indicator. At the end point the indicator will change from the basic to the acidic form when an extra drop of acid had been added. 

Pipette 25.0 cm of M/60 iodate solution into a 250 cm conical flask, add 0.5 g KI and 1 g sodium thiosulphate and a few drops of methyl red indicator and shake to dissolve. Titrate with standard 0.1 M HCl with constant stirring until the colour changes sharply from yellow to red. Repeat and calculate from the average titre, the iodate concentration in mol dm  

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