Alcoholometry with a Hydrometer

Determination of Alcohol with a Hydrometer

If the alcohol of a fermenting vinegar is transformed into acetic acid completely, thus loss-free, 1 % ABV alcohol is quite accurately equivalent to 1 % acidity. Therefore it is in principle possible to use the hydrometer for vinegar to quantify the alcohol content, but since the density of vinegar is affected by most of its ingredients, like acetic acid, alcohol, solved sugar, and extract, the indicated acidity value of the hydrometer will usually be considerable wrong. If the deviation from the actual acetic acid content is taken into account, for both, the fermenting and the alcohol-free, fully fermented vinegar, it is possible to calculate the alcohol content. The actual acetic acid content can be determined by, for example, titration. This method of determining the alcohol content is decribed the first time in 1907 by F. Rothenbach.

Depending on the used fermentation process, alcohol losses due to evaporation and formation of mother of vinegar can be enormous. Another result of the alcohol content calculation is the amount of these losses. If the input field for titrated, fermenting vinegar (the optional field) is left empy, the calculation results in the theoretical loss-free acidity and alcohol content.

Measured value of the vinegar spindle:

% acid
% acid

Actual (titrated) acid content:

% acid
% acid

*) optional

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Optional Input Field Is Empty
Indicated Value of the Hydrometer for Vinegar
fermenting vinegar: 11.4 % acidity
fully fermented vinegar: 13 % acidity

Real Acidity Obtained by Titration
fermenting vinegar: —
fully fermented vinegar: 4.7 % acidity

The fermenting vinegar contains 3.9 % acidity.
The alcohol content is at most 0.8 % ABV, if no
losses occurred due to evaporation or
formation of mother-of-vinegar.
ABV: Alcohol By Volume (alc./vol.)

Optional Input Field Is Completed
Indicated Value of the Hydrometer for Vinegar
fermenting vinegar: 11.4 % acidity
fully fermented vinegar: 13 % acidity

Real Acidity Obtained by Titration
fermenting vinegar: 3.4 % acidity
fully fermented vinegar: 4.7 % acidity

The fermenting vinegar contains 3.4 % acidity
and 0.3 % ABV alcohol. The losses of alcohol
caused by evaporation or formation of mother-
of-vinegar are 23 %, thus 1% alcohol results in
0.77 % acidity.
ABV: Alcohol By Volume (alc./vol.)