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