Campden have multiple uses in homebrewing and are a versatile tool in both winemaking and beer making. Campden tablets are one of 2 chemicals, either sodium or potassium metabisulfite which have unique attributes useful to the brewer.
Firstly they are used to sanitise wine musts and juices as well as equipment but can also be used during racking as both a measure to prevent bacteria from spoiling the wine and also as an antioxidant to keep air from staling the wine. Along with this, they can be used in removing chlorine or chloramine from water sources which is particularly useful to beer makers. Chlorine in water reacts with compounds in malted barley and can create unpleasant off flavours. Dissolving a crusheCampdenen tablet in up to 20 litres or 5 gallons of water is an effective way to reduce the chlorine to negligible levels.