Distilled vinegar was used in the titration portion of the lab

The total acidity can be measured by titrating against sodium hydroxide. Look up a table to get the best indicator (weak acid, strong base). The photos below shows Jennifer and Rachel - Yr 11 Chem students from Moreton Bay College - turning wine into vinegar.

The percent acidity (percentacetic acid) in a sample of vinegar is calculated by the Equation 1.
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4) grams of acetic acid = (moles of acetic acid)(MW)By assuming the density of the vinegar sample to be 1.00 g/mL, the gramsof vinegar solution can be calculated by multiplying the volume of vinegarby the density.


Titration of acetic acid in vinegar; ..

Calculation of pHin the titration of weak acids with weak bases is more difficult.
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1. "The pH and titratable acidity of wine are two measures of the same thing".

2. "You can calculate pH of wine if you know its titratable acidity".

3. "A chemist can measure change in wine as the ethanol is oxidized to acetic acid". As the tannins produce hydrogen peroxide the colour changes and then the peroxide changes the ethanol to ethanal and then on to acetic acid. The colour will change, the smell will be different, the ethanol decreases, the titratable acidity will increase.. and so on.


Volumetric Analysis Titration of Vinegar

I din't want to filter out the acetobacter so I just added 2.0 mL of the vinegar to a beaker-full of wine. This would change the pH and titres I know but I though I should try. I put one sample in a sealed air-free bottle and the other in a beaker on the bench. After a week I titrated them against the 0.100 M NaOH as mentioned above. The sealed wine gave a titre of 18.15 mL and the air-exposed wine gave a titre of 24.95 mL. So, this wine oxidized too. I didn't do the pHs as there was no point. Great for an EEI.

AQA | GCSE | Chemistry | Subject content

We will see how the acidity of substances is measured; we will learn about some acid-base indicators; we will produce pH indicating papers; we will do a titration of vinegar; we will search for natural indicating substances and we will determine the color scale of them.

Classroom Resources | Argonne National Laboratory


1. Temperature
The optimum growth temperature for is 25-30°C, with no growth observed at 40°C. Weak growth was observed even as low as 10°C, but none at 8°C.

2. Acidity or pH
Perhaps add some tartaric acid to have a range of starting pHs (the optimum pH for the growth of acetic acid bacteria is 5.5-6.3, however, these bacteria can survive at the low pH values of between 3.0 and 4.0 found in wine). A pH of 3.3 and lower is inhibitory to most bacteria in wine, but not to acetic acid bacteria. Maybe try pHs of 2, 3, 4, 5, 6.

3. Ethanol concentration
.
Ethanol is a good carbon source for acetic acid bacteria, but is also inhibiting at concentrations that are too high. One report I saw said that in wine containing 5% ethanol, only 58% of the was active and that this was reduced to only 13% in wine containing 10% ethanol. At 15.5% it seems all activity is inhibited (stopped).