and also a specific range of and :

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

1 + T_1 \, y  +T_2 \, y^2 + T_3 \, y^5 + T_4 \, y^2 \, (1+ A_8 \, y^2) \cdot \exp \left( - A_8 \, y^2  \right)  - \frac{T_5}{y} = 0

T_1 = A_1 + \frac{A_2 }{ T_{pr} } + \frac{A_3 }{ T_{pr}^3 }

T_2 = A_4 + \frac{A_5 }{ T_{pr} }

T_3 = \frac{A_5 \, A_6 }{T_{pr}}

T_4 = \frac{A_7 }{T_{pr}^3}

T_5 = \frac{0.27 \, P_{pr} }{T_{pr}}

where

Z-factor
fluid temperature	pseudo-reduced temperature (or reduced temperature in case of pure substances)	pseudo-critical temperature (or critical temperature in case of pure substances)
fluid pressure	pseudo-reduced pressure (or reduced pressure in case of pure substances)	pseudo-critical pressure (or critical pressure in case of pure substances)