Distillation - determination ofthe alcohol content of wine

Principle

If the alcohol content of a wine is determined directly with an alcohol meter (hydrometer), the resulting alcohol content reading is approximately 0% by volume. This is due to the composition of the wine. The effect of the alcohol on the density is cancelled out by other components such as sugars, acids, essential oils, etc..
For this reason, in order to determine alcohol content by density, the alcohol must be separated out by means of distillation prior to the determination. This corresponds to the official method which currently applies for measuring alcohol in wines. First the wine is titrated to neutrality against bromothymol blue. After transfer to the distillation apparatus, two thirds of this wine sample is distilled off into the receiver flask. Subsequently the distillate is filled back up to the original volume again. Now the density is measured with a pycnometer or hydrometer.

Benefits

• Stable and safe setup on demonstration board
• Illustrative presentation of the distillation process including digital datalogging

Tasks

Distillate a sample of wine to determine the content of ethanol.

Learning objectives

• Ethanol
• Distillation