Winkler Method vs. Vernier Method

f) To find the amount of dissolved oxygen within a substance one could use the Winkler Method.  Also known as titration, this method involves the addition of alkaline iodide and manganous sulfate to a water sample.  This process starts when manganeous hydroxide is produced and, upon acidification, is converted to a manganese compound by the oxygen in the water sample.  Then the compound instantly reacts with the iodide to release iodine, which in turn, makes the water sample become dark yellow in color.  This amount of free iodine released is equal to the amount of dissolved oxygen within the sample.  Therefore, the next step of the method is to find out that quantity of free iodine.  To do this, one should first add starch indicator to the sample because it makes it easier to see the titration for it turns the solution a dark purple.  Then one must titrate the iodine with sodium thiosulfate until the sample goes from a dark purple color to clear because the change in color signifies the end point in titration.  The Winkler methods precision range is 0.1 to 0.6%.  Another method, aside from the Winkler method, that can be used for a similar purpose in the Vernier method.  This process is a much simpler way of finding dissolved oxygen in comparison to the Winkler method, and this method can also be used to test for carbon dioxide, pH, temperature, turbidity, nitrate levels, and various other characteristics.  This method involves a small computerized machine, and sensor probes.  Each characteristic utilizes a different probe in which you plug into the vernier.  After submerging the probe into the water sample a reading will appear on the machine, and it provides you with an accurate reading of whatever you are testing.