The advanced two-plate mathematical model of electrochemical hydrogen evolution/dissolution process has been presented and discussed. The model, with Langmuir adsorption equation, has been experimentally verified by the use of the glassy carbon/Pd layer electrode system at different scan rates. The two cathodic-anodic stages of hydrogen evolution/dissolution process in 0.1 M and 0.001 M HCl solutions have been interpreted and discussed. The thickness of the layer and the way of deposition were also investigated. The fundamental kinetic problem of a change of electrode properties during electrode process as an effect of the elementary hydrogen presence in the solid electrode is presented and interpreted. The isopotential point phenomenon, an electrochemical analog of isosbestic point in absorption spectroscopy, was unexpectedly discovered as experimental effect of hydrogen adsorption and alpha variability. (C) 2010 Elsevier Ltd. All rights reserved.