The Chemistry Behind Alcohol Distillation

The chemistry behind alcohol distillation

Distillation of alcohol is relatively straightforward. The key is that more volatile alcohol has a lower boiling point than water, meaning it evaporates faster and separates from other components in solution faster than usual – leading to collection and condensation into liquid form with much higher concentrations of alcohol than previously present in original mix. This process forms the basis of all forms of distillation including beer brewing and whiskey distilling.

Raoult’s law and Dalton’s law both dictate that in an ideal system at constant pressure, Raoult’s and Dalton’s laws dictate that the ratio of liquid-to-vapor composition will remain unchanged – an equilibrium state. Unfortunately, distillation does not work this way in practice: lighter volatile components (like fruity esters) always vaporize before heavier ones, so mixture will never become completely clean.

Distillation alone cannot guarantee ultra-pure products, so additional chemical separation methods must also be utilized. Batch distillation and fractionation are two proven ways of reaching this goal.

Distillation takes place in a still, or pot. Fermented mash is transferred into the still and heated to low temperatures until alcohol begins evaporating from its molecules, then collected and condensed back into liquid form with much higher alcohol concentration than was present initially in its mixture.

Step Two entails repeating this sequence to achieve increasingly pure product. In order to do this, a distiller must constantly monitor the ratio of vapor-to-liquid flow in the column, the reflux-to-product flow rate to control discharge temperature and alcohol vapor concentration, and how much heat is being applied to reboiler.