The ring test is shown by compounds having:

Explanation

The brown ring test is a qualitative analysis technique used to detect the presence of nitrate ions. When a solution containing nitrate ions is treated with freshly prepared ferrous sulfate and then carefully added to concentrated sulfuric acid, a brown ring forms at the interface between the two layers. This indicates the presence of the nitrate radical. Sulphate and chloride radicals do not produce such a ring. The sulphate radical is typically detected by forming a white precipitate with barium chloride, while the chloride radical forms a white precipitate with silver nitrate.