Estimation of DO2 in water sample of investigated pond (Khuta Bandh, Dumka Jharkhand)

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Requirements- 

• Water sample
•  Conical flask
•  Pipette
•  Magnus sulphate solution
•  Alkaline iodide solution
•  Concentrated H₂SO₄
•  Sodium thiosulphate solution (N/40)

Process of Estimation

Water sample was collected from pond in a 250ml of magnus sulphate solution was added in a sample by means of a pipette. Now, 2ml of alkaline iodide solution (KI+KOH) was added by means of pipette. The sample was through shacked. A precipitate was developed in the form of manganese hydroxide which is an oxygen carrier which combines with the oxygen in water to form magnic oxide precipitation. The bottle was kept for few minutes for settling down the precipitate. Now, 2ml of concentrated H₂SO₄ was added by means of pipette and shacked the same again. The basic magnic oxide reacted with H₂SO₄ to liberate nascent oxygen. The nascent oxygen now liberated iodine from KI in the presence of H₂SO₄. The color of the solution became yellow due to the presence of free iodine. The amount of liberated iodine was determined treated sample by sodium thiosulphate solution. 100ml of treated sample was titrated by N/40 by sodium thiosulphate solution. The initial reading was noted due to titration, iodine color was gradually became faint then few drops of freshly prepared starch solution is added as indicator. The blue solution was again titrated till the blue color just disappear. This was the end point. The final reading of sodium thiosulphate was noted. In this way 3 sample where titrated and tabulated. Out of 3, 2 common reading titrated that is volume of sodium thiosulphate solution used during the titration of 100ml sample water into 2. 

The exact volume of sodium thiosulphate consumed was numerically equal to DO₂ contain in ppm (parts per million).