How is the presence of `SO_2` detected?

Explanation

`SO_(2)` is a colourless and pungent smelling gas.
It can be detected with the help of potassium permanganate solution. When SO2 is passed through an acidified potassium permanganate solution, it decolonizes the solution as it reduces `MnO_(4)^(-)"ions to " Mn^(2+) "ions"`.
`5SO_(2) + 2MnO_(4)^(-) + 2H_(2)O to 5SO_(4)^(2-)+ 4H^(+)+ 2Mn^(2+)`