How to Calculate Winkler Titrations

Lajos Winkler Titrations

• 1

  Fill the sink with water.

• 2

  Lower the glass bottle into the sink, filling it with water.

• 3

  Add 2 ml of manganese sulfate to the water in the glass bottle.

• 4

  Add 2 ml of alkali-iodide-azide reagent to the water in the glass bottle.

• 5

  Place a bottle stopper over the bottle.

• 6

  Check for air bubbles. Discard and start over if any bubbles are discovered.

• 7

  Mix the substance by turning the bottle upside down several times.

• 8

  Add 2 ml of concentrated sulfuric acid.

• 9

  Use the glass flask to mix the substance with sodium thiosulfate and titrant solution.

• 10

  Add 2 ml of starch. The substance should turn blue.

• 11

  Add more titrant solution until the substance turns clear.

• 12

  Calculate the following: mg/L=K x 200 x 0.025 N thiosulfate used in titration. K=Vol. of bottle/(Vol. of bottle-Vol. of reagents). The concentration of dissolved oxygen in the sample is equal to the number of milliliters of titrant used, where each ml of sodium thiosulfate is equal to 1mg/L of dissolved oxygen.