Dissolved Oxygen Lab Abstract

nearby Phillips Academy Andover. We collected our samples in the stream, the pond and the bucket respectively, all repeating the same method. The key point we have learnt for this investigation is not to have any air bubbles in the sampling bottle when collecting water. After adding 8 drops of Manganous Sulfate Solution and Alkaline Potassium Iodide Azide Solution, the water changes to an opaque yellow color. After the shoulder of the bottle is settled, another 8 drops of Sulfuric Acid is added. The sample is then “fixed”. 20ml of the “fixed” sample is added to the test tube. Using the Direct Reading Titrator, fill it with Sodium Sulfate and add it to the "fixed” sample until the orange yellow changes to a faint yellow color. The 8 drops of Starch Indicator Solution added will change the sample to blue color. After titrating the sample, the blue color will disappear. We then have the amount of dissolved oxygen from the Direct Reading Titrator, and having the temperature of the water, the percentage of saturation can be found using the Nomogram. After collecting all the results, we realized that all the groups had similar results making it easy to have an accurate average, however, the bucket has an anomaly (as shown on the table below), the reason for it might be inaccurate drops of any chemicals leading an inaccurate result. Overall, we conclude that in general the lower the temperature, the higher the amount of dissolved oxygen there is; also, higher amount of dissolved oxygen will produce higher percentage saturation. Table 1. Dissolved Oxygen and Saturation Percentage of Stream, Pond and Bucket StreamPondBucketWater Temperature (°C)1217.518Oxygen (ppm)Saturation (%)Oxygen (ppm)Saturation (%)Oxygen (ppm)Saturation (%)Average8.6777.6678.87.648317.6707.6808.49028.2757.17277339827.35738.59048.4778.2858.28658.1787.4788.48868.6808.3857767----685 Graph 1. Amount of Dissolved Oxygen Graph 2. Percentage of Saturation