Chemical Test For Chlorine 3

Action with starch-iodide paper :

Chlorine Gas turns damp starch iodide paper deep blue / blue black coloured complex.

First chlorine reacts with KI (aq) in the starch iodide paper :

Cl₂ (g)     +       2KI (aq)       →       KCl (aq)       +                                         I₂ (aq)

                                                                                       Here I₃^- Ion formed which is actually soluble in water   

Then iodine that is formed will react with starch in the starch-iodine Paper  :

I₂ (aq)      +       Starch  →       blue black / deep blue coloured complex