Summary
Highlights
Simple distillation is a technique used to separate a liquid from a solution, for example, obtaining pure water from seawater. The process involves heating the solution to evaporate the desired liquid, which then condenses back into liquid form and is collected separately.
The equipment includes a flask for the solution, sealed with a bung and a thermometer to monitor temperature. A condenser cools the vapor back into liquid using a water jacket with continuously flowing cold water, and a beaker collects the pure liquid. A Bunsen burner provides the heat.
The mixture is heated, causing the liquid to evaporate. The vapor rises and is forced into the condenser. Inside the condenser, the cold water causes the vapor to cool and condense into a liquid, which then collects in the beaker. For instance, heating seawater yields pure distilled water, leaving the salt behind.
Simple distillation is ineffective for separating liquids with similar boiling points. In such cases, fractional distillation is used, which is designed to separate mixtures of liquids, such as methanol, ethanol, and propanol.
Fractional distillation equipment is similar to simple distillation, but it includes a fractionating column between the flask and the condenser. This column contains glass rods to provide a large surface area and is designed to create a temperature gradient, being cooler at the top than at the bottom.
When separating liquids like methanol, ethanol, and propanol, the mixture is heated to the boiling point of the liquid with the lowest boiling point (e.g., methanol at 65°C). As this liquid evaporates and rises up the fractionating column, other liquids that may have evaporated will condense on the cooler glass rods and fall back into the flask, ensuring only the purest form of the desired liquid reaches the condenser and is collected. This process is repeated at increasing temperatures for other liquids.
After collecting methanol, the temperature is raised to the boiling point of ethanol (e.g., 78°C) to collect pure ethanol. Finally, the remaining liquid in the flask is assumed to be pure propanol, or the temperature can be further increased to distill the propanol.