PH does not measure alkalinity.
Alkalinity measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution.
Alkalinity is sometimes incorrectly used interchangeably with basicity. For example, the addition of CO2 lowers the pH of a solution. This increase reduces the basicity; however, the alkalinity remains unchanged (see example below). For total alkalinity testing, N/10 H2SO4 is used by hydrologists along with phenolphthalein indicator.
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