Sulphurous acid

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Medium-strength acid (international name dihydrogen sulphite), which is formed when sulphur dioxide is introduced into water. Particularly in a warm environment, it tends to oxidise into the much more toxic and stronger sulphuric acid. The salts and esters of sulphurous acid are called sulphites or neutral or secondary sulphites, as well as hydrogen sulphites or formerly bisulphites or primary or acid sulphites.

When sulphur dioxide is added to mash, must or wine, most of it is converted into sulphurous acid, with only a small proportion remaining as sulphur dioxide. The sulphurous acid immediately begins to split into sulphites and hydrogen sulphites. Both form compounds with various substances in the wine. Only when these processes are complete is the so-called free sulphurous acid present. The amount depends on the temperature and the pH value, but is usually around 20%. This means that around 80% of the sulphurous acid is present in the wine in bound form.

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Sulphurous acid

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