An equation of state for gases and liquids

We present an equation of state that can represent within experimental error most individual sets of published PVT data for most fluids, whether in the range of vapor at moderate pressures, or compressed liquids, or gases at very high temperatures and densities, any region in fact except the vicinity of the critical point. In terms of pressure the equation is P = DRT 1 + (D/T) (c₁T + c₂D - 1) / (c₃ + c₄T^{$\text{sol1}\text{2}$} + c₅D + c₆D²)] where D = 1/V, the density in mole 1^?1. The coefficients are readily determined by a least squares fit of the data. An additional term is sometimes needed if the D range is very wide, say several times D_c. Different fluids can be simultaneously represented over a limited range, such as the compressed liquid region, by a single reduced form of the equation in which all but three of the constants are the same for all, and these three (a reducing T, 1/c₁, a reducing D, 1 / c₂, and a dimensionless parameter) are characteristic of each individual fluid. The equation can also simultaneously represent many data sets for a single fluid from many labs and covering various T and D ranges. From this, a consistent representation of its thermodynamic properties can be derived.