## reference value pH standard

https://doi.org/10.1351/goldbook.R05234
An aqueous solution of $$0.05\ \text{mol}$$ potassium hydrogen phthalate per kg water which is the reference value for the definition of pH(RVS) values in the temperature range $$0$$-$$95\ ^{\,\unicode{x26ac}}\text{C}$$.
operational pH standard
,
primary pH standards
Source:
PAC, 1985, 57, 531. (Definition of pH scales, standard reference values, measurement of pH and related terminology (Recommendations 1984)) on page 540 [Terms] [Paper]