Atomic Statement
Because pH is logarithmic and depends on acid–base equilibria and activity, arithmetic averaging of pH is not a general mixing rule.
Principle
Because pH is logarithmic and depends on acid–base equilibria and activity, arithmetic averaging of pH is not a general mixing rule.
Evidence And Locators
Brown chapter 17, printed p. 823; Clayden chapter 8, printed pp. 165–166; IUPAC pH definition.
Application
Keep pH, titratable acidity and sensory sourness distinct. Calculate only with a suitable equilibrium model and adequate composition data, or report a method-defined measurement.
Boundary
Aqueous pKa values, electrode calibration and activity approximations need scrutiny in ethanol–water mixtures.