The Equilibrium of a Metal and an Electron Gas

The quantity L represents, here, the heat absorbed when a mole of electrons is evaporated at temperature T. That is, it is the change in enthalpy, or T times the change of entropy, on evaporation, or is the change of internal energy plus PVf since wo can neglect the term PV for the electrons in the metal. Thus it is the latent heat of evaporation of electrons at temperature T. Then we can interpret the quantity No(dCp/dN) merely in terms of the change of latent heat with temperature, a change that can actually depend on many factors. We may 

Finally the quantity i in Eq. (2.2) is the chemical constant of an electron gas. This is given by Eq. (3.16), Chap. VIII  

All the quantities in Eq. (2.4) are familiar except g0, which we now discuss. As we saw in Chap. XXI, Sec. 2, the orientation of the electron spin is quantized in space, so that it has two possible stationary states of orientation, in which the spin is directed in either of two opposing directions. This results in having g0 the a priori probability of the lowest stationary state, equal to 2, so that we have 

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