Dear Jirka,

There is NO effect of dissolved oxygen on the pH of pure water.

NO pka of oxygen was determined.

Hoping this will be helpful,

Rafik

I though so, but could you please explain this. We use pure oxygen for our fermentation process (pulse dosing, so there some oscillation around set point). pH rises with every oxygen dose (just about 0.5). There is bicarbonate buffer, so is it possible that oxygen supplement removes carbon dioxide from medium, so the pH rises? Can it be like this?

Dear Jirka,

This is feasible and I think this might be the reason since If CO2 is removed the solution will be more basic (higher pH).

Rafik

The oxidation of organic matter leads to changes in dissolved inorganic carbon, and hence in changes in pH depending on buffering and kinetics

Does oxidation of organic matter lead to CO2? If so, than pH should drop. But I observe increase in p value.

One would expect a stoichiometric change in the molar concentration dissolved in a solution containing labile organic matter (all things being equal, normal conditions). If O2 is not limiting in seawater, for example, then labile organic matter should remineralize following Redfield ratios (approximately). In other words, one would expect that a decrease in O2 being consumed solely in the process of oxidazing organic matter leads to an increase in DIC and Nutrients dissolved in the aq. The reverse process is not expected based on thermodynamics.

Dear Jirka,

CO2 reacts with moisture to generate H2CO3, which is an acid. Hence the pH will drop (a decrease in pH).

Rafik

Aerating water drives off Carbon dioxide, hence a rise in pH. This happens until equilibrium is attained coz of the presence of bicarbonate buffer.