When an aqueous solution of a colourless mixture of two salts is treated with a drop of chlorine water, the solution becomes brown. Some chloroform is added to the brown solution and the resulting mixture is shaken wel. The chloroform layer becomes violet. (ii) When chlorine water is again added dropwise to the above mixture, the chloroform layer becomes colourless. (iii) On being heated with solid K_(2)Cr_(2)O_(7) and concentrated H_(2)SO_(4), the solid mixture gives vapours of a dark colour which form a yellow solution with aqueous NaOH. On acidification with acetic acid followed by treatment with lead acetate, the yellow solution gives a yellow precipitate. (iv) When boiled with an NaOH solution, the mixture gives a gas that produces thick white fumes with HCl vapours and turns nessler's reagent brown. the mixture does not respond to any other test for cations. (v) The mixture, on being heated, gets completely sublimed. Q. Which of the following reactions takes place in (ii) ?