Dosage varies when used to kill wild bacteria in must, halt fermentation, or preserve finished wines against oxidation. The addition of 1/4 teaspoon of potassium metabisulfite to 5 gallons contributes approximately 50 ppm of free SO2.
To make a sanitizing rinse for equipment, dissolve 8 teaspoons of potassium metabisulfite into 1 gallon of water. High concentrations of sulfur dioxide gas are irritating and toxic, so use in a well ventilated area. After applying the solution to your equipment, the items must be rinsed with clean, cold water.