The density series virial equation of state truncated at the third virial coefficient has been evaluated for describing the fluid nonideality of systems of pure solids in equilibrium with near-critical CO2 including systems with cosolvents. The function [In (z phi(1))]/rho is found to be linear with rho for pressures up to 400 bar for 16 solutes, eleven of which also involved 8 different cosolvents for temperatures from 300 to 523 K. As required, when the virial series is applicable, the zero-density intercepts obtained from high-pressure data agree with those from low-pressure data. The method shows how cosolvent contributions via composition and density can be explicitly separated. Prediction of second cross virial coefficients along with fitting the third virial to a single data point on the isotherm can be at least as successful as other models. Sensitivity to variations in sublimation pressure, solid molar volume, and fluid density has been tested.