In the titration of I₂ (aq) by ${\mathrm{S}}_2{\mathrm{O}}_3^{2-}$ (aq) using the starch indicator, the end point is indicated by 

In an iodometric titration, a starch solution is used as an indicator since it can absorb the I₂ that is released. This absorption will cause the solution to change its colour from deep blue to light yellow when titrated with standardised thiosulfate solution. This indicates the end point of the titration.