Volumetric method for determining concentrations of ozone have been carried out by
ozonation of 5 mL KI solution of 15 g/L with phosphate buffer pH 7 solvent. KI solution that
has been exposed to ozone was then added with a solution of 0.5 M H2SO4 to pH 2, then
titrated with 0.07 M Na2S2O3 solution that has been standardized [10] until it turned pale
yellow color. Then, 1% starch indicator solution of 0.5 mL was added and the titration
continued until the titration end point, i.e. when a blue color changes to colorless. The
procedure was repeated for the concentration of KI solution of 20 g/L and 25 g/L, as well as
to the volume of KI solution 10, 15 and 20 mL. Determination of the concentration, at each
combination of volume and concentrations, repeated three times, while the ozone
concentration calculated by the stoichiometric equation, i.e. the number of moles of iodine
formed is directly proportional to the number of moles of ozone to oxidize.