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Sulfur Dioxide

Sulfur dioxide (SO2) is a chemical compound used in food preservation and winemaking.

In the winemaking process, winemakers add sulfur dioxide (SO2) to wine in order to inhibit bacteria and wild yeast growth, although this is typically considered only if malolactic fermentation isn’t intended. Later in the process after fermentation SO2 is added to wine as an antioxidant and for its anti-microbial properties. As an antioxidant SO2 helps preserve the color, flavor, and stability of the wine. As an antimicrobial SO2 interferes with the metabolic pathways of yeast and bacteria.

When SO2 is added to wine, a portion of it becomes immediately bound while a remaining portion is unbound SO2. The portion that is unbound is also called free SO2 and it is responsible for protecting the wine. The bound and free SO2 together are referred to as total SO2.

Hanna offers titration systems for the potentiometric titration of sulfur dioxide. These systems include an application-specific version minititrator that simplifies the measurement for winemakers. Titrators are available to be programmed with multiple methods including one specific for wine that can also measure acidity, reducing sugars, and YAN.

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Titration systems with precision dosing pumps are available to perform a sulfur-dioxide titration. There are options for titrators with two analog inputs and two dosing pumps. This configuration allows for one channel to be used with a pH electrode and titrant for acid/base titrations and the other channel for a ORP probe and titrant for the titration of sulfur dioxide.


An application specific titrator for wine is available for the measurement of sulfur dioxide. This meter uses pre-standardized titrants and pre-packaged reagents to simplify the measurement. With this system everything is included to measure free or total sulfur dioxide in two ranges.

Electrodes and Probes

The following are ORP electrodes for use when performing the redox titration for sulfur dioxide. In this category is the ORP probe with the Hanna Clogging Prevention System (CPS) technology that prevents clogging of the reference junction by solutions with a high solids content.


Accessories for sulfur dioxide titration include spares for the minititrators. The spares include the replacement tubing set and valve, plastic beakers, and magnetic stir bars used for mixing.