The inversion curve can be found by solving its equation for b / v , and substituting into the vdW equation. This produces p / p ∗ ∗ = − − 1 + 4 ( T / 2 T ∗ ∗ ) 1 / 2 − − 3 ( T / 2 T ∗ ∗ ) , where, for simplicity, a , b , R have been replaced by p ∗ ∗ , T ∗ ∗ .