Oxygen sampling and measurement at geothermal wells

Content of dissolved oxygen in geothermal fluid is very important to control the corrosion rate of the pipes. Because of the volatility of the oxygen, this compound must be fixed immediately in the sampling site after its collection. Then, the fixed solution must be titrated immediately to get accurate results.

Here are some illustrations of the fixation method and titration technique.

O2_fijation_titration

Dissolved oxygen is fixed immediately after collection with Mn(II) as manganese oxide (II), MnO2, which is a brown solid. The browner the solution, higher dissolved oxygen content in the sample. The brown solution is titrated immediately with a known concentration of tiosulphate in present of starch. The colour of the solution changes from purple to a light purple, when approaches to the end point of the titration.

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