One of two compounds which may be used to sanitize winemaking equipment and utensiles (the other being sodium metabisulfite). Potassium metabisulfite is the active ingredient in Campden tablets. Its action, in water, inhibits harmful bacteria through the release of sulfur dioxide, a powerful antiseptic. It can be used for sanitizing equipment and the must from which wine is to be made. For equipment, a 1% solution (10 grams disolved in 1 liter of water) is sufficient for washing and rinsing. After using the solution, the equipment should not again be rinsed. For sanitizing the must, a 10% solution is made (100 grams dissolved in 1 liter of water). Three milliliters of this 10% solution added to a U.S. gallon of must will add approximately 45 ppm of sulfur dioxide (SO2) to the must. One should wait at least 12 hours after sanitizing the must before adding the yeast. Both bottles of solution (1% and 10%) should be clearly labled as to strength and active compound to prevent disasterous mistakes, and both may be stored in a cool place for up to one year without effecting potency. Also see Campden Tablet and Sodium Metabisulfite.