Define Blank titration for Determination of the Iodine Number of Lipids?

Using an autopipette, measure 25 ml of Hanus iodine reagent accurately and transfer into a 250 ml iodine flask. Add 10 ml CHCI₃ with a measuring cylinder. Mix. Stopper the flask and add distilled water in the cup around the stopper to prevent loss of iodine. Keep the flask in the dark for 30-40 minutes. Titrate the contents of the flask according to the method described for sample titration. Since there is no oil in the blank flask and no reaction will take place between the oil and Hanus solution, the blank titration could be performed without keeping the flask in dark for 30-40 minutes to reduce the time for analysis. It could also be done with reduced volumes of the reagents as follows: measure accurately 5 ml of Hanus iodine reagent into a 250 ml conical flask, add 2 ml of CHCI₃ and immediately titrate using 1/5th volume of all the reagents used in the sample titration except the oil.