pH (Lever)

Definition

The lever, and usually the dominant one, by which hydrogen ion concentration decides which carbonate species are allowed to exist.

At low pH hydrogen is abundant and pushes the chain left toward CO2/H2CO3; at intermediate pH bicarbonate dominates and acts as a buffer; at higher pH hydroxide pulls the system toward carbonate. Above about pH 8.3 carbonate becomes operationally relevant for scale, and above about pH 10.3 it becomes the dominant species. pH does not cause scale, but it gives carbonate permission to exist.

Related concepts

The Four Levers · Carbonate Speciation · Crossover pH Values

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Part of The Blueprint of Water · 🧪 chemistry