A new static high pressure(0-10 MPa)equilibrium cell with viewing window was established. The volumes of both vapor and liquid phases can be accurately determined from the window. The degassed pure liquids can be fed continuously

therefore

one half of a phase diagram can be determined in a single run of experiment. Vapor pressures of pure dichloro-difluoromethane

diethyether and acetone above ordinary boiling point and isothermal vapor-liquid equilibria of two binary systems

dichlorodifluoromethane-diethylether and diethylether-acetone were measured. Temperature T

total amount nT and total composition z of the system

total vapor pressure p and volume of vapor phase Vg were taken directly from the experiment. With the use of material balance and the method of calculating vapor compositions y from T

p and x

equilibrium liquid and vapor composition x and y of these binaries were obtained. The fugacity coefficients needed during the calculations were estimated by the modified Peng-Robinson equation of state.