Winkler method

1. Title: The Winkler method 2. Instruments: -Winkler bottle - calibrated pipette - Erlenmeyer flask - volumetric pipette - propipette 3. Chemicals: -manganese sulfate -potassium iodide -concentrated sulfuric acid -sodium thiosulfate -starch solution 4. Procedure: -We have used the Winkler method to determine dissolved oxygen in tapped water -a sample Winkler bottle is filled completely with water. -the dissolved oxygen in the sample is "fixed" by adding manganese sulfate and potassium iodide -the sample is mixed by inverting several times and checked for air bubbles -then concentrated sulfuric acid is added via a pipette and inverted several times to dissolve the floc -after leaving the solution settle in the Winkler bottle, solution is pipetted with volumetric pipette to Erlenmeyer flask -we titrated our sample with solution of sodium thiosulfate to a pale straw color -we added starch solution so a blue color forms and titrated again until the sample turns clear 5.Result: -we calculated the concentration of dissolved oxygen in the sample by formula using the number of milliliters of titrant sodium thiosulfate 6.Made by: Ivona Milićević, Klara Perović, Nevena Milčić, Iva Pavičić, Dora Štern-Vukotić