Distillation and liquid layers

Simple distillation recovers a solvent from a solution containing a non-volatile solute. Heat salt water: water vaporises, enters a condenser, cools and becomes liquid distillate. Salt remains in the flask. Place the thermometer bulb near the side-arm to measure the vapour entering the condenser. Cooling water enters the condenser at the lower end and exits at the upper end to keep the jacket full.

Fractional distillation separates miscible liquids with different boiling points, especially when those boiling points are close. A fractionating column provides repeated evaporation and condensation. The vapour reaching its top is richer in the more volatile, lower-boiling component. Collect fractions over suitable temperature ranges. Crude oil is separated into groups of hydrocarbons this way; a fraction is generally a mixture, not one pure compound.