What is solution distillation? Since x solvent in the solution is less than 1, the vapor pressure of the solvent in the solution is always lower than that of the pure solvent. Distillation curve of sucrose aqueous solution. Curve 1 and curve 2 represent the temperature-vapor pressure curves of water and sucrose aqueous solutions, respectively. The presence of sucrose molecules in the solution will reduce the concentration of water molecules on the surface of the solution, thereby reducing the vapor pressure of the solution. Therefore, the vapor pressure of the solution (point B) is lower than the vapor pressure of water (point A) at the same temperature. Water will boil at 100°C (under 1 atmosphere), but the solution will not boil yet. Only at a higher temperature (point B') the solution will boil. For this type of solution, distillation is either used to recover pure solvent or to obtain solid solute.

When the mole fraction of the solution containing non-volatile components is distilled, the solvent vapor is led out from the condenser, and the non-volatile components remain in the residual liquid in the bottle. A simple distillation can vaporize most of the solvent to achieve the purpose of separation. . According to Raoult's law, under a certain pressure, the vapor pressure of the solvent in the dilute solution is equal to the vapor pressure of the pure solvent multiplied by the mole fraction of the solvent in the solution: p solvent = po solvent x solvent where p solvent and po solvent are respectively Is the vapor pressure of the solvent in the solution and the vapor pressure of the pure solvent.