How is ozone estimated?

Explanation

When `O_(3)` is treated with excess of `KI` solution buffered with borate buffer `(pH 9.2), l_(2)` is liberated quantitatively.
`2l^(-)(aq)+H_(2)O(i)+O_(3)(g) - to 2OH^(-)(aq)+l_(2)(s)+O_(2)(g)`
The `l_(2)` thus liberated is titrated against standard solution of sodium thiosulphate using starch as an indicator.
`underset("Sod. thiosulphate")(2Na_(2)S_(2)O_(3) +) l_(2) to underset("sod. tetrathioate")(Na_(2)S_(4)O_(6) + 2Nal)`