Although this equation calculates the chemical potential of
water vapor relative to vapor at the saturation pressure at temperature
T, if the water sorption experiment allows equilibrium
to be established, the chemical potential of sorbedwater is equal
to that of the vapor, in which case, the equation also calculates
the chemical potential of water in the solid relative to the vapor
at p0. Also, as the chemical potential of pure liquid water
is the same as water vapor at saturation (p0), the equation can
be expressed more specifically to denote the condensed phases
involve