How do you measure dissolved oxygen content in a river?
The Winkler test is used to determine the concentration of dissolved oxygen in water samples. Dissolved Oxygen, abbreviated D.O., is widely used in water quality studies and routine operation of water reclamation facilities. An excess of Manganese(II) salt, iodide (I-) and hydroxide (OH-) ions are added to a water sample causing a white precipitate of Mn(OH)2 to form. This precipitate is then oxidized by the dissolved oxygen in the water sample into a brown Manganese precipitate. In the next step, a strong acid (either hydrochloric acid or sulphuric acid) is added to acidify the solution. The brown precipitate then convert the iodide ion (I-) to Iodine. The amount of dissolved oxygen is directly proportional to the titration of Iodine with a thiosulphate solution [1]. However, there are dissolved oxygen meters these days that do this test without the use of chemicals.
