Did anybody actually check the pH before and after autoclave? Is there a certain degree of decrease in pH caused by autoclave?
Thanks
Yes, sure, pH changes are frequently observed during a treatment in autoclave, as many reactions are prone to occur (hydrolysis, condensation, precipitation, depolymerization, etc.), most of them producing or consumming protons. It is difficult to say more without knowing what has been autoclaved (organic or inorganic matter ?) and in which conditions (mild hydrothermal conditions or high pressures and temperatures at which water behaves like a molten salt ??)
Alain
There are many reasons, but I think that the main reason is the reaction. Could be the oxidation reaction by the pressure into the autoclave; generating acid and an acidic environment, Then the results will be a less pH value after autoclave operation or in the product discharged.
Among other possible reasons, pH may change due to increased solubility of dissolved gases at high pressure. Dissolved O2 may possibly participate in solution redox equilibria, what may alter OH- concentration, and hence the pH, while if the solution or the autoclave athmosphere contains CO2, higher solubility can be expected for higher pressure as compared with normal atmospheric pressure. This may originate a tendency for lowering the pH, due to right-hand displacement of the following equilibrium: 2H2O + CO2 ↔ H3O+ + HCO3-.
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