Rectified spirit contains 95.6% ethanol and 4.4% water. This mixture of ethanol is known as an azeotropic mixture. The percentage of ethanol cannot be increased by using distillation method. Because when the mixture boils the composition of the components remain same in vapour state. But if we change this composition by adding another component then rectified spirit can be converted to absolute alcohol by distillation method. Here if we add lime (CaO) to the rectified spirit then water of the mixture can be absorbed by the lime. As a result the percentage of ethanol will be changed. So the mixture will not act as an azeotropic mixture. In this way we can prepare absolute alcohol by using distillation method from rectified spirit.
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