Campden tablets are also known as Potassium Metabisulphite, which is used in the de-gassing stage when making wine. Use the tablets to block oxidation or the growth of wild yeast and bacteria that can spoil a batch.
You can also use these in a home-brewer environment to remove chlorine/chloramine from their water. These tablets are meant to be crushed and used as a sterilizer.
*Contains 57% Sulfur Dioxide*