Campden Tablets (Potassium Metabisulfite)

In wine, used to kill naturally occurring microorganisms and prevent spoilage. Also works as an antioxidant. Add at a rate of 1 tab/gallon to achieve 75 ppm free SO2.  These tablets use potassium metabisulphate as opposed to sodium metabisulphate.  This is generally preferred by winemakers who do not want to add sodium into their wine.  

Can also be added to water to remove chloramine (1 tab is sufficient for roughly 5-20 gallons)