AN IMPROVEMENT OF VAN-DER-WAALS-EQUATION OF STATE

van der Waals equation of state has been improved by adding 5 paramete rs as follows, P = RT/(V-b)-(a(0)+a(1)/V+a(2)/V-2)/(V-2-cV) and b =(b( 0)+(b(1)+b(2))/V)/(1+b(2)/V-2), where, P : pressure, R:gas constant, T :absolute temperature, V:molar volume, ao, al, al, bo, bl, b(2), c:par ameters. The equation has showed good applicability to the isothermal PVT data of Helium, Hydrogen methane, Nitrogen and Water in the wide d ensity range of around three times of the each critical density within 0.5% error. The physical meanings of the parameters are discussed.