A Unified pH Scale for All Phases†
The work of D.H., S.K.G., and I.K. was supported by the Deutsche Forschungsgemeinschaft, the Freiburger Materialforschungszentrum (FMF), the Albert-Ludwigs-Universität Freiburg, and the Fonds der Chemischen Industrie. We thank Dipl.-Chem. Philipp Eiden for help with the computer programming. The work of I.L. was supported by the Estonian Science foundation (grant 7374).
Graphical Abstract
One for all! On the basis of the absolute chemical potential of the proton, a unified absolute pH scale is introduced that is universally applicable in the gas phase, in solution, and in the solid state. With this scale, it is possible to directly compare acidities in different media, and to give a thermodynamically meaningful definition of superacidity. This scale can be used in all areas with variable proton activity.