Acid precipitation: Measurement of pH and acidity1

Abstract

The pH and acidity of precipitation are difficult to measure accurately because of the low ionic strength of the samples. Use of measured pH to estimate hydrogen‐ion concentration may err by as much as 50% if activity coefficients, junction and streaming potentials, and non‐Nernstian behavior of the electrode system are ignored. The magnitude of the individual errors is assessed and procedures for measuring pH and acidity to reduce the total error to ±5% are recommended.