Winkler Method vs. Vernier Method

     The Winkler method and the Vernier method both were used to determine the amount of dissolved oxygen our water samples. Both methods also yielded similar results. For example, when using the Winkler method, two groups’ dissolved oxygen levels were 0.4 mg/L and 0.6 mg/L when the water sample temperature was 22 degrees Celsius. Using the Vernier method we also discovered that the dissolved oxygen content was 0.7 mg/L when the temperature was 22 degrees Celsius. Both of these levels are very similar to each other as well as to the ideal data, which had a dissolved oxygen level of 6.3 mg/L when the temperature was 20 degrees Celsius. These results are pretty close to the results we obtained using the Winkler and the Vernier methods.
    The Winkler method involves a methodical process involving many chemicals. First you must collect your water sample in a bottle and be careful to make sure that as little as possible outside oxygen enters it. Then you add eight drops of manganous sulfate to the bottle, then add eight drops of alkaline iodide to the sample. Then you carefully cap the bottle and invert it several times. When finished, set it down on the table and wait until the precipitate settles to below the shoulder of the bottle. Then your instructor has to add the sulfamic acid and you must close the bottle again and invert it several times. Then add eight drops of starch indicator to the bottle. Measure out 20 ml of the solution into a titration vile and cap it. Fill a titration syringe with thiosulfate and begin the titration process. This titration requires a fair amount of time and patience because you must go one drop at a time.
     The Vernier method is much simpler than the Winkler method. You just get the desired probe, clean it with distilled water, connect it to the Vernier device, and stick the probe in your beaker filled water sample. Then you just wait for the reading to be produced by the Vernier device.