do you know about azeotropic mixtures?.
An azeotropic mixture has a boiling opoint that does not change when vapour is removed by evaporaion. The boiling point may be higher or lower than any of the components of the mixture.
toluene / water mixture has bp 85.0oC, but bp toluene is 110.6oC and bp water is 100.0oC. For the toluene-water system, below 85oC the two liquid phases coexist. At 85oC the sum of the vapour pressures of water and toluene = one atmosphere, and boiling starts.
In a mixture of toluene and water, boiling occurs at 85oC and both water and toluene are in the vapour that condenses to form two layers. The bottom layer of water has 0.06% toluene dissolved in it. The top layer of toluene has 0.05% water dissolved in it. The relative volumes are 18% water and 82% toluene. The excess toluene flows back into the flask and distils back over with more water. At 85oC, vapour presure of water = 57.7 kPA and vapour pressure of toluene = 50.6 kPa. Weight of water = (molar mass water /molar mass toluene) X (vapour pressure water / vapour pressure toluene) = (18 / 92) X (57.7 / 50.6) = 0.223 = 20%.
I hope this will clarify your doubt.