Two liquids, A and B, show partial miscibility below 52.4°C. The critical concentration at the upper critical temperature is x = 0.459, where x is the mole fraction of A. At 40.0°C the two solutions in equilibrium have x = 0.22 and x = 0.60, respectively, and at 42.5°C the mole fractions are 0.24 and 0.48. Sketch the phase diagram. Describe the phase changes that occur when B is added to a fixed amount of A at

(a) 48°C,

(b) 52.4°C.