pH standard

https://doi.org/10.1351/goldbook.P04661
See: operational pH standard, primary pH standard, reference value pH standard
Source:
PAC, 1985, 57, 531. 'Definition of pH scales, standard reference values, measurement of pH and related terminology (Recommendations 1984)' on page 540 (https://doi.org/10.1351/pac198557030531)