Sulphites are compounds containing sulphite ions. In sulphite ion, the sulphur atom is doubly bonded to one oxygen atom and singly bonded to other two oxygen atoms. There is also a non-bonded lone pair of electrons on the sulphur. Sulphites are often used as preservatives in dried fruits, preserved radish and dried potato products.
This video explains how to test the presence of sulphite ion in a given salt.