This equation instructs us to create isosteres (constant
amount sorbed) of ln p versus 1/T, the slope of which gives the
partial molar enthalpy of water relative to the bulk water molar
enthalpy. In surface science literature, a derivation of Eq.(9)
is given by a different approach, and the negative of the enthalpy
terms is referred to as the isosteric heat, which uses the
vapor as the reference state