Calculate gas density from critical pressure, critical temperature and acentric factor data for organic and inorganic fluids (Yaws).
The compressibility factor can be calculated from either the Peng Robinson, Soave, Redlich Kwong, or van der Waals cubic equation. The compressibility factor calculation is valid for gas phase only. The gas specific gravity is approximately equal to the ratio of the gas molar mass over the molar mass of air (28.964 g/mol).
Reference : Yaws Chemical Properties Handbook, McGraw Hill