How is ozone estimated?

Explanation

(1)The quantitative estimation of ozone, `O_(3)` is carried out by redox
titration.
(2) Since ozone is a very good oxidising agent, it is allowed to
oxidise potassium iodide (KI) solution containing borate buffer
`(pH = 9.2)` to liberate iodine.
`2KI_((aq)) + H_(2)O_((1))+ O_(3(g)) overset(pH=9.2)(rarr)2KOH_((aq))+I_(2(g))+O_(2(g))`
(3) Liberated iodine is titrated with a standard solution of sodium
thiosulphate, `Na_(2)S_(2)O_(3)` using starch as an indicator.
`I_(2) + 2Na_(2)S_(2)O_(3) rarr 2NaI+Na_(2)S_(4)O_(6).`
From the amount of liberated iodine, the ozone content can be
estimated, since 1 mol of `I_(2)` is produced by 1 mol of `O_(3)`.