How is the presence of `SO_(2)` detected ?

Explanation

`SO_(2)` has a pungent odour. Two tests to detect the presence of `SO_(2)` are as follows :
1. `SO_(2)` decolourises acidified `KMnO_(4)` solution.
`5SO_(2)+underset("Violet")(2MnO_(4)^(-))+2H_(2)O to5SO_(4)^(2-)+4H^(+)+underset("Colourless")(2Mn^(2+))`
2. `SO_(2)` Changes the colour of acidified potassium dichromate solution from orange to green.
`3SO_(2)+underset("Orange")(Cr_(2)O_(4)^(2-)+2H^(+)to3SO_(4)^(2-)+underset("Green")(2"Cr"^(3+))+H_(2)O`