Redox Titration
... Starch solution will be used as a indicator in this experiment, in which deep blue colour will be shown in the presence of iodine; however, it¡¦s added near the end of the titration when the solution is straw-coloured, because a black precipitate will be formed in the solution, in which it can¡¦t be dissolved easily EVEN if there is extra thiosulphate solution. The end-point for this titration is the point when the addition of one drop of sodium thiosulphate causes the disappearance of the deep blue colour. ... For example, the tip of burette is blocked, and the titration can¡¦t be carried out. „« During the titration, burette was rinsed with sodium thiosulphate solution and its tap was switched on and allowed solution to pass through it before the beginning of the experiment.