THE CARBON dioxide-methylene chloride system is of interest for possible propellant applications in aerosol packaging, but none of the required equilibrium data were found to be available in the literature. Equilibrium values of total pressure, liquid composition, and liquid density at 7P F. and from 15 to 300 p.s.i.a. were measured. To obtain these data within the desired accuracy, an equilibrium cell was designed which would ensure attainment of true static equilibrium hetween gas and liquid phases under carefully measured total pressure, and provide for sampling the equilibrium liquid phase only (without changing the equilibrium composition due to the sampling procedure itself), for determination of liquid density and composition. Thus, a by-product resulting from this work an apparatus and technique which are applicable, in general, to the determination of similar equilibrium data in gas solubility work at high pressures where conventional glass systems cannot be used.