When chlorine water is added to an aqueous solution of potassium halide in the presence of chloroform, a colour is developed but on adding more of chlorine water the colour disappears, and a colourless solution is obtained. This test confirms the presence of the following in aqueous solution :

When chlorine water is added to an aqueous solution of sodium iodide in presence of chloroform, ${\mathrm{Cl}}_2$ displaces iodine from sodium iodide and gives violet colouration to the chloroform layer, When more chlorine water is added, the violet colour disappears and the solution becomes colourless due to the formation of ${\mathrm{HIO}}_3$.

$\begin{array}{l}2\mathrm{NaI}+{\mathrm{Cl}}_2⟶2\mathrm{NaCl}+{\mathrm{I}}_2\\ {\mathrm{I}}_2+5{\mathrm{C}}_2+6{\mathrm{H}}_2\mathrm{O}⟶\underset{\text{ (colourless) }}{2{\mathrm{HIO}}_3+10\mathrm{HCl}}\end{array}$