A liquid mixture of 50 mol% chloroform(1) and 50% 1,4-dioxane(2) at 0.1013 MPa is metered into a flash drum through a valve. The mixture flashes into two phases inside the drum where the pressure and temperature are maintained at 24.95 kPa and 50°C. The compositions of the exiting phases are x₁ = 0.36 and y₁ = 0.62.

Your supervisor asks you to adjust the flash drum pressure so that the liquid phase is x₁ =0.4 at 50°C. He doesn’t provide any VLE data, and you are standing in the middle of the plant with only a calculator and pencil and paper, so you must estimate the new flash drum pressure. Fortunately, your supervisor has a phenomenal recall for numbers and tells you that the vapor pressures for the pure components at 50°C are P₁^sat = 69.4 kPa and P₂^sat = 15.8 kPa. What is your best estimate of the pressure adjustment that is necessary without using any additional information?