Define Sample titration for Determination of the Iodine Number of Lipids?
With a clean dry pipette, accurately measure 0.3 mL of oil into a clean and dry iodination flask (Duplicate Jask required). Alternatively, weigh and transfer 0.3 g of the oil into the flask for better accuracy. Add 10 ml CHCI, with a measuring cylinder and mix. Using an automatic pipette, add exactly 25 ml Hanus iodine solution. Mix well. Stopper the flask. Add distilled water in the cup around the stopper to prevent loss of iodine. Keep the flask in the dark for 30-40 minutes. Remove the stopper and let the distilled water in the cup fall into the flask. Add 10 ml of 15% KI solution and 100 ml of freshly boiled and cooled distilled water.
Shake. Titrate the iodine liberated in the process with standard sodium thiosulfate solution (0.1 N) stoppering the flask and shaking vigorously from time to time while titrating until a pale yellow colour is obtained. Now add 2 ml of 0.5% starch solution. Continue the titration until the blue colour disappears. After the blue colour disappears from the aqueous phase, note the chloroform layer in the bottom of the flask which may contain untitrated iodine as indicated by a pink or violet colour. By continuous shaking bring this iodine into the aqueous layer. The end point of the titration is reached when the aqueous layers, as well as, the lower chloroform layer are completely colourless. Titrate the duplicate iodine flask in a similar manner.