at those conditions (21 C, 1 Bar) a std. EOS can provide good accuracy,
however if you increase pressure you may observe deviations, as example consider the experimental data points for Carbon Dioxide density reported by DDB
herebelow the values for density calculated with a few methods available in REFPROP and PRODE,
T = 290.70 K P = 5066.250 KPa DENS = 149.694 KG/M3
(NIST) REFPROP = 150.65
(Prode) MBWR = 150.9
(Prode) GERG 2008 = 150.6317
(Prode) Lee Kesler Plocker = 152.7519
(Prode) Peng Robinson = 153.6083
T = 292.95 K P = 5572.88 KPa DENS = 181.111 KG/M3
(NIST) REFPROP = 179.99
(Prode) MBWR = 182.3
(Prode) GERG 2008 = 179.99
(Prode) Lee Kesler Plocker = 183.2054
(Prode) Peng Robinson = 183.255
T = 423.15 K P = 27864.4 KPa DENS = 463.263 KG/M3
(NIST) REFPROP = 461.37
(Prode) MBWR = 461.73
(Prode) GERG 2008 = 461.0108
(Prode) Lee Kesler Plocker = 452.8833
(Prode) Peng Robinson = 446.3791
hoping this helps
