Measurements of the critical pressure p c , densityρ c , and temperature T c of the pure substanceCH 2 F 2 as well as {xCO 2 + (1 −x)SF 6 }, {xSF 6 + (1 −x)CH 2 F 2 }, and {xCHF 3 + (1 −x)CH 2 F 2 } were performed by observing the critical opalescence in a static equilibrium cell. When possible, the experimental data were compared with values given in the literature. The experimental results for the binary mixtures are described by the Peng–Robinson and the Trebble–Bishnoi–Salim equations of state, using only the experimental critical data of the pure components and those of a mixture with x ≈ 0.5. The equations of state are used to describe the critical loci, the dependence of the supercritical density on temperature and composition, and the excess volume of the binary systems investigated.