The reduction of 4,4’-bipyridine (BPH22+) on mercury in an acid medium gives a very narrow sharp tail-less reversible voltammetric peak that can be ascribed to the formation of a two-dimensional (2D) phase of the cation radical BPH2.+ at the electrode according to the reaction BPH22+ + e(-) reversible arrow BPH2.+(2D) The corresponding oxidation peak possesses similar properties and arises from the destruction (fusion) of the 2D phase. In this work we studied the influence of some experimental variables, namely the type of anion present in the medium, the concentration of 4,4’-bipyridine and temperature on the 2D phase transition peaks. Also, we tested various analytical criteria to validate this assignation and fitted both voltammetric peaks numerically to the theoretical model developed for this purpose.