At what pH does the bicarbonate equivalence point normally occur?
The bicarbonate equivalence point for most environmental water samples occurs near a pH of 4.5, plus or minus about 0.5. However, the equivalence point can occur outside this range. For example, a sample with a low alkalinity and a low concentration of inorganic carbon (carbonate plus bicarbonate plus carbonic acid) from a pristine headwater stream can easily have a bicarbonate equivalence point above pH 5.0. Your best guide is experience; be careful not to overshoot the endpoint by titrating too quickly. If you do overshoot the endpoint, just keep going well beyond the endpoint and analyze your data with Gran’s method.
