Deriving relations ships using partial differentiation: Enthalpy is a function of pressure (p) and temperature (T). Write the total differential for dH. Enthalpy is also a function of entropy and pressure: dH=Vdp+TdS use this to derive an equation for ?H/?P at constant T. Combine your result from b with (?H/?T)_P=Cp to write an equation for dH in terms of changes in T, p and V all measurable quantities.