A mixture of two salts was treated as follows :
(i) The mixture was heated with maganese dioxide and concentrated sulphuric acid, when yellowish green gas was liberated.
(ii) The mixture on heating with sodium hydroxide solution gave a gas which turned red litmus blue.
(iii) Its solution in water gave blue precipitate with potassium ferricyanide and red colouration with ammonium thiocyanate.
(iv) The mixture was boiled with potassium hydroxide and the liberated gas was bubbled through an alkaline solution of `K_(2)HgI_(4)` to give brown precipitate.
Identify the two salts, Give ionic equations for reactions involved in the tests (i), (ii) and (iii).