Experiment 10 - Vitamin C Determination

Procedure:

Part B - Standardization of the Iodine Solution

1. Obtain about 100 mL of iodine solution in a clean and dry 250 mL beaker. The oven may be used to dry the beaker.
2. Acclimatize the buret with the iodine solution. Use three 10 mL portions of the iodine solution to rinse the inside of the buret. The small buret funnel should be used when transferring the iodine solution from the beaker into the buret.
3. Fill the buret to the 0.00 mL mark with the iodine solution.
4. Transfer about 50 mL of standard thiosulphate, S₂O₃^2-, ion solution into a clean and dry 100 mL beaker.
5. Pipet 25.00 mL of the standard thiosulphate, S₂O₃^2-, ion solution into a clean 250 mL erlenmeyer flask.
6. Add about 10 drops of starch indicator to the flask.
7. Add the iodine solution to the erlenmeyer flask until the blue end point is reached.
   

   Rinse the erlenmeyer flask occasionally.

   Swirl the solution until the colour end point stays.

   
   

   The blue endpoint of the titration.

   
   
8. Read the buret carefully to determine the quantity of iodine used to reach the end point. Record the volume of the iodine solution used.
9. Repeat steps 3 to 7 until two titration volumes are obtained which agree to within +/- 0.10 mL.