The distribution potential established when two liquids are placed in contact has been measured using a streaming technique. In particular the contributions from the diffusion potentials have been quantified. On the basis of the experimental results, the concept of distribution potentials upon the partition of a salt between two phases is revisited. We also compare Galvani potential differences for solutions in equilibrium and for situations where two liquids are placed in contact, as encountered in micro-TAS systems and micro-reactors. Finally, it is shown that in potentiometry we can define, as in traditional amperometry, a half-wave potential that takes into account the mass transfer of the salt to the interface.