The potential difference E m between two saturated
KCl bridges inserted into two solutions separated by a membrane. The solutions need not be in equilibrium with one another and need not contain any colloidal material.
Source:
PAC, 1972, 31, 577. 'Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry' on page 619 (https://doi.org/10.1351/pac197231040577)