Mixture of volatile components A and B has total vapour pressure (in torr)  p  = 254 — 119 X_A where X_A is mole fraction of A in mixture. Hence ${\mathrm{p}}_{\mathrm{A}}^{\mathrm{o}}$ and ${\mathrm{p}}_{\mathrm{B}}^{\mathrm{o}}$ are (in torr)