P- and M-alkalinity Titration

Definition

Two titration measurements that, compared together, reveal which alkalinity species are present in water.

M-alkalinity is titrated to about pH 4.3 and represents total acid-neutralizing capacity from hydroxide, carbonate, and bicarbonate. P-alkalinity is titrated to about pH 8.3 (the phenolphthalein endpoint) and includes all hydroxide plus half the carbonate but no bicarbonate, because during the P titration hydroxide is neutralized and carbonate is only converted to bicarbonate. Comparing P to M lets an operator infer the hydroxide, carbonate, and bicarbonate split, turning routine titration into chemical reconnaissance.

Related concepts

Alkalinity · Half-Carbonate Behavior · P-alkalinity

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Part of The Blueprint of Water · 📏 measurement