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At what temperatures do ethanol and water boil during alcohol distillation?

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distilled spirit The fermentation and distillation process for producing whiskey. The production of whiskey begins with grinding grain into a meal, which is cooked. Malt is introduced to the meal, which results in mash that is cooled and pumped into a fermenter, where yeast is added. The fermented mixture is heated in a still, where the heat vaporizes the alcohol. The alcohol vapours are caught, cooled, condensed, and drawn off as clean, new whiskey. This liquid is stored in a cistern room, and water is added to lower the proof (absolute alcohol content) before the whiskey is placed in new charred oak barrels for aging and later bottling.

In the context of alcohol distillation, it is important to clarify that ethanol and water do not have a single, fixed boiling point when mixed. Instead, their boiling behavior is determined by their interaction as a liquid mixture.12

At standard sea-level atmospheric pressure, the individual boiling points are:
* Water: 100 °C (212 °F)341
* Ethanol: 78 °C (173 °F)1

During distillation, the mixture's boiling point depends on the concentration of these components. Because ethanol is more volatile than water, the vapor produced above the liquid mixture is richer in ethanol, which allows for separation through distillation.12

However, this process is limited by the formation of an azeotrope—a specific mixture of approximately 95.57% ethanol and 4.43% water. This azeotropic mixture boils at a constant temperature of 77.95 °C (172.31 °F), which is lower than the boiling point of either pure component. Because the vapor of an azeotrope has the same composition as the liquid, it cannot be further separated by simple distillation. Achieving higher concentrations of ethanol requires specialized techniques, such as using entrainers or pressure-swing distillation.1