200mL of KL solution are added to a gas washing bottle equipped with an open gas bubbling
device (tube or diffusor) under a reagent depth of 15 cm or more; (the use of fritted glass
diffusors is not recommended).
· A second identical flask is connected in series as a guard detector for ozone transfer and
reaction in the first flask.
· Process gas containing ozone is bubbled at a flow rate of 1 L/minute or less, until a total
(estimated or expected) quantity of approximately 1 mM O3 (it equals 0.048 g) has passed.
· The iodine formed in the solutions of KI in the flasks, immediately after acidification with 5mL
of the acidifying reagent, is titrated h a freshly standardized sodium thiosulfate solution.
· After titration to a pale yellow color, optionally, 0.5mL of the starch indicator solution can be
added to complete and record the final result. (This addition is recommended, but can be
optional, depending on the skill and experience of the operators).