Crossover pH Values

Definition

The approximate pH thresholds where one carbonate species hands dominance to the next.

Below about pH 6.3 dissolved CO2/H2CO3 predominates; from roughly 6.3 to 10.3 bicarbonate predominates; above about 8.3 carbonate becomes operationally relevant; above about 10.3 carbonate predominates. The CO2/HCO3- crossover sits near pH 6.3 and the HCO3-/CO3 2- crossover near pH 10.3. These thresholds let an operator predict scaling and corrosion risk directly from a pH reading.

Related concepts

pH (Lever) · Carbonate Speciation · P- and M-alkalinity Titration

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Part of The Blueprint of Water · 📏 measurement