The determination of dissolved oxygen is to bring about the oxidization of potassium iodide with the dissolved oxygen present in the water sample after adding MnSO4, KOH and KI. The basic manganic oxide formed acts as an oxygen carrier to enable the dissolved oxygen in the molecular form to take part in the reaction. The liberated iodine is titrated against standard hypo Solution using starch indicator.

Experimental Procedure:

Take the standard flask with 200 ml of water to that add 2ml of MnSO4 and 2ml of KI + KOH (alkali potassium iodide).Light brown precipitate forms, to this add 2ml of conc.H2SO4 precipitation dissolved into brown colour. Take 100 ml of solution which is in the standard flask and pour it into conical flask. To the conical flask add 1–2ml of starch needed immediately colour changed to blue. Then titrate the solution with hypo solution until the solution becomes colourless. Note down the readings and repeat it. Amount of dissolved oxygen content is obtained in mg/ lit (or) ppm.

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