# Deriving the equation for lines of constant enthalpy

1. ### djkuehlos14

1
How would one derive the equation for (dP/dV)H? That is the partial of P over the partial of V, holding H constant. I've tried many different things, triple product rule, maxwell relationships, and nothing seems to work. I appreciate any advice.

### Staff: Mentor

$$dT=(\frac{\partial T}{\partial P})_VdP+(\frac{\partial T}{\partial V})_PdV$$
$$dH=C_PdT+(V-T(\frac{\partial V}{\partial T})_P)dP$$