Which of the following statements regarding the nitrate ion test is incorrect?
| 1. | A dark brown ring is formed at the junction of the two solutions. |
| 2. | A ring is formed due to the formation of nitroso ferrous sulphate complex. |
| 3. | The brown complex is \([Fe(H_2O)_5~(NO)]SO_4.\) |
| 4. | Upon heating the nitrate salt with conc. \(H_2SO_4,\) light brown fumes are evolved. |