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_{11} \, y^2) \, \exp (- A_{11} \, y^2) - \frac{T_5}{y} = 0

T_1 = A_1 + \frac{A_2}{T_{pr}} +  \frac{A_3}{T_{pr}^3}  +  \frac{A_4}{T_{pr}^4}  +  \frac{A_5}{T_{pr}^5}

T_2 = A_6 + \frac{A_7}{T_{pr}} +  \frac{A_8}{T_{pr}^2}

T_3 = - A_9 \cdot \left[
 \frac{A_7}{T_{pr}} +  \frac{A_8}{T_{pr}^2}  
\right]

T_4 =\frac{A_{10}}{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)

and

Reference

See also