In order to separate the consituents, pass the gaseous mixture through alkaline solution of ferrous sulphate. As a result, a black precipitate of ferrous sulphide is formed due to `H_(2)S` taking part in the reaction.
`FeSO_(4)+H_(2)S rarr underset("(Black ppt.)")(FeS)+H_(2)SO_(4)`
`SO_(2)` will not react and will escape from the solution in pure form. In order to regenerate `H_(2)S`, treat the black precipitate with dilute `HCl`.
`FeS(s)+2HCl (dil) rarr FeCl_(2)(aq)+H_(2)S(g)`
