(1)	$\begin{array}{l}\displaystyle \rho(p, T) = \frac{1}{Z} \cdot \frac{M}{R} \cdot \frac{p}{T}\end{array}$

where

$\begin{array}{l}\rho\end{array}$	Gas density	$\begin{array}{l}p\end{array}$	Gas pressure	$\begin{array}{l}M\end{array}$	Gas molar mass
$\begin{array}{l}Z(T, p)\end{array}$	Compressibility factor	$\begin{array}{l}T\end{array}$	Gas temperature	$\begin{array}{l}R\end{array}$	Gas constant

Despite the name it covers a lot of medium-density liquids as well.

Pure Substances

The Z-factor $\begin{array}{l}Z(p, T)\end{array}$ of pure substances is usually modelled through the reduced fluid properties $\begin{array}{l}(T_r, p_r)\end{array}$ :

$\begin{array}{l}T_r = T/T_c\end{array}$	Reduced Temperature	$\begin{array}{l}T_c\end{array}$	Сritical temperature
$\begin{array}{l}p_r = p/p_c\end{array}$	Reduced Pressure	$\begin{array}{l}p_c\end{array}$	Critical pressure

Below is the list of the most popular Real Gas EOS @models:

Fluid Mixtures

The Z-factor $\begin{array}{l}Z(p, T)\end{array}$ of fluid mixtures is usually modelled through the pseudo-reduced fluid properties $\begin{array}{l}(T_{pr}, p_{pr})\end{array}$ :

$\begin{array}{l}T_{pr} = T/T_{pc}\end{array}$	Reduced Temperature	$\begin{array}{l}T_{pc}\end{array}$	Pseudo-critical temperature
$\begin{array}{l}p_{pr} = p/p_{pc}\end{array}$	Reduced Pressure	$\begin{array}{l}p_{pc}\end{array}$	Pseudo-critical pressure

See Z-factor Correlations @model for the charts, implicit and explicit empirical correlations on fluid mixture Z-factor $\begin{array}{l}Z(T_{pr}, p_{pr})\end{array}$ .

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