By using the unifying reference states proton gas (1 bar => pHabs) and electron gas (1 bar => peabs), the thermodynamic relations of any reaction with transfer of protons and / or electrons in any medium (gas or
condensed phases) may be compared, best on the protoelectric potential map PPM. It is a 2D plot of pHabs vs. peabs, i.e. a unified solvent-independent window. The
definitions of pHabs and peabs are based on the chemical potentials of the proton and electron, as well as their conversion into the conventional scales as defined by
Sørensen. Eabs is the absolute electrode potential ET as identified by
Trasatti. The useful pHabs,water-value is the continuation of the aqueous pH scale to non-aqueous media and connected to the Eabs,water- and peabs,water-values.