Methods of approximate calculation of vapor density on a saturation li
ne for 17 substances within the reduced temperature range from 0.5 to
1 have been analyzed and compared. Eight approximate methods have been
discussed: equations of real gas state (van der Waals, Berthelot, Die
terici, Kamerlingh Onnes, Martin, Roedlich-Kwong, Peng-Robinson) and t
he Krupskii and Eselev equation.