Separating a liquid from a mixture – fractional distillation
In fractional distillation a mixture of several substances, such as crude oil, is distilled and the evaporated components are collected as they condense at different temperatures. is a method for separating a liquid from a mixture of two or more liquids. For example, liquid The alcohol which is produced as a result of fermentation of sugars by yeast. can be separated from a mixture of ethanol and water by fractional distillation. This method works because the liquids in the mixture have different boiling points. When the mixture is heated, one liquid evaporates before the other.
Image caption, A water and ethanol mixture is heated in a flask using an electric heater. Vapour forms in the air above the mixture in the flask.
1 of 3
One way to check the purity of the separated liquids is to measure their boiling points. For example, pure ethanol boils at 78°C and pure water boils at 100°C.