The relationship between the experimental zero charge potential, E(pzc), of indium and thallium amalgams and their electronic work function, Phi, is studied and discussed. For indium amalgams, the linear relationship, E(pzc) = Phi-const., is found to be obeyed in the surprisingly wide composition range of 0.02 < x(In) < 0.6. The data for pure mercury do not fit on the line, presumably because of its low electronic density of states. Potentials at constant negative charge density, E(p sigma c), depend on the work function in a characteristic manner, which is interpreted by taking into account the desorption of indium from the metalsolution interface and the degree of water orientation in the compact double layer. Also, the experimental data are used to discuss the concept of "electrochemical work functions" determined as the shift between two parallel charge densities vs. potential curves. Using electrochemical work functions determined for the thallium amalgams, their behaviour is found to be quite similar to that of the indium amalgams. It appears that these amalgams constitute a most useful continuous series of metal phases to study the metal dependency of interfacial properties.