Vinegar Chemical Formula

3D illustration of the chemical structure of acetic acid.
The chemical structure of acetic acid, the primary ingredient in vinegar. Laguna Design / Getty Images

Vinegar is a naturally-occurring liquid that contains many chemicals, so you can't just write a simple formula for it. It is approximately 5-20% acetic acid in water. So, there are actually two main chemical formulas involved. The molecular formula for water is H2O. The structural formula for acetic acid is CH3COOH. Vinegar is considered a type of weak acid. Although it has an extremely low pH value, the acetic acid doesn't completely dissociate in water.

The other chemicals in vinegar depend on its source. Vinegar is made from the fermentation of ethanol (grain alcohol) by bacteria from the family Acetobacteraceae. Many types of vinegar include added flavorings, such as sugar, malt, or caramel. Apple cider vinegar is made from fermented apple juice, beer cider from beer, cane vinegar from sugar cane, and balsamic vinegar comes from white Trebbiano grapes with a final step of storage in special wooden casks. Many other types of vinegar are available.

Distilled vinegar isn't actually distilled. What the name means is that the vinegar came from the fermentation of distilled alcohol. The resulting vinegar typically has a pH of around 2.6 and consists of 5-8% acetic acid.

Characteristics and Uses of Vinegar

Vinegar is used in cooking and cleaning, among other purposes. The acid tenderizes meat, dissolves mineral build-up from glass and tile, and removes the oxide residue from steel, brass, and bronze. The low pH gives it bactericidal activity. The acidity is used in baking to react with alkaline leavening agents. The acid-base reaction produces carbon dioxide gas bubbles that cause baked goods to rise. One interesting quality is that vinegar can kill drug-resistant tuberculosis bacteria. Like other acids, vinegar can attack tooth enamel, leading to decay and sensitive teeth.

Typically, household vinegar is about 5% acid. Vinegar that contains 10% acetic acid or a high concentration is corrosive. It can cause chemical burns and should be handled carefully.

Mother of Vinegar and Vinegar Eels

Upon opening, vinegar may start to develop a sort of slime called "mother of vinegar" that consists of acetic acid bacteria and cellulose. Although it isn't appetizing, mother of vinegar is harmless. It may be easily removed by filter the vinegar through a coffee filter, although it poses no danger and may be left alone. It occurs when the acetic acid bacteria use oxygen from the air to convert remaining alcohol into acetic acid.

Vinegar eels (Turbatrix aceti) are a type of nematode that feeds off of mother of vinegar. The worms may be found in opened or unfiltered vinegar. They are harmless and not parasitic, however, they aren't particularly appetizing, so many manufacturers filter and pasteurize vinegar before bottling it. This kills the live acetic acid bacteria and yeast in the product, reducing the chance that mother of vinegar will form. So, unfiltered or unpasteurized vinegar may get "eels", but they are rare in unopened, bottled vinegar. As with mother of vinegar, nematodes can be removed using a coffee filter.