ASTM E70

pH of Aqueous Solutions With the Glass Electrode

Applicability: Applies to the electrometric measurement of pH in aqueous solutions, including those containing high concentrations of electrolytes or water-soluble organic compounds. Accurate hydrogen ion activity results are obtained when the pH falls between 2 and 12 and electrolyte or nonelectrolyte concentrations do not exceed 0.1 mol/L; results outside these bounds should be treated as semiquantitative and interpreted with care.

Purpose: Measures pH using a glass electrode in a potentiometric arrangement, specifying apparatus requirements, calibration procedures with NIST-traceable standard buffer solutions, and step-by-step measurement protocols to minimize systematic error. The method details procedures for temperature correction, electrode conditioning, and verification of calibration validity before and after sample measurement. Results are used to characterize solution chemistry, monitor industrial chemical processes, and support quality control programs across pharmaceutical, environmental, food, and laboratory settings.