Z = \frac{0.27 \, P_{pr}}{y \, T_{pr}}

R_5 \, y^2 \, (1+ A_{11} \, y^2) \cdot \exp \left( - A_{11} \, y^2  \right)
+ R_1 \, y - \frac{R_2}{y} +R_3 \, y^2 - R_4 \, y^5  +1 = 0

R_1 = A_1 + A_2 \, t + A_3 \, t^3 + A_4 \, t^4 + A_5 \, t^5

R_2 = \frac{0.27 \, P_{pr}}{T_{pr}}

R_3 = A_6 + A_7 \, t + A_8 \, t^2

R_4 = A_9 \cdot ( A_7 \, t + A_8 \, t^2) 

R_5 = A_{10} \, t^3

t= \frac{1}{T_{pr}}