The role of the potential of zero charge (PZC) and of the potential of maximum adsorption E-m during the adsorption of neutral molecules at the electrode surface is not yet well understood. The phase transition of the adsorbed molecules to a condensed state adds further complications. But under certain circumstances this process can be utilized to obtain additional information about the adsorbate system and the electrochemical double layer. On these grounds a new method for the determination of the potential of maximum adsorption in condensed layers is proposed. This method is based purely on a qualitative analysis of the shape of current-time transients, which change their sign at the potential of maximum adsorption and become inverted. From this datum and the corresponding capacity-potential curves of the adsorbate system and of the pure electrolyte one can construct the true charge-potential characteristics of the system and obtain the value of the PZC. This method was applied to the system thymine/mercury/0.1 M NaClO4. One result is that in this system the potential of maximum adsorption is a function of the temperature, the pH-value, and the prepolarization potential. This latter result can only be explained in terms of a kinetic argumentation.