We give a general thermodynamic analyzis of the behaviour of the chemical
potential of electrons in metals at a second order phase transition, including
in our analysis the effect of long range Coulomb forces. It is shown, that this
chemical potential can have a kink at Tc, both for fixed sample volume and
fixed external pressure. The Coulomb term transfers the changes in chemical
potential of the electrons into an experimentally observable shift of the
surface potential if the sample is electrically connected to a ground
potential. VSGD.93.9.th1Comment: 6 pages, no figures. Revtex, version 2, Materials Science Center
Internal Report Number VSGD.93.9.th