This method determines the vitamin C concentration in a solution by a redox titration with potassium iodate in the presence of potassium iodide. Vitamin C, more properly called ascorbic acid, is an essential antioxidant needed by the human body (see additional notes).
When iodate ions (IO3 − ) are added to an acidic solution containing iodide ions (I−), an oxidation-reduction
Due to this reaction the iodine formed is immediately reduced to iodide as long as there is any ascorbic acid present. Once all the ascorbic acid has been oxidised, the excess iodine is free to react with the starch indicator, forming the blue-black starch-iodine complex.
‘This is the endpoint of the titration. The method is suitable for use with Vitamin C tablets, fresh or packaged fruit juices and solid fruits and vegetables.
If you have any questions or comments relating to this
experiment, please contact us. Please note that this
service is for senior school chemistry students in
New Zealand only. We regret we are unable to respond
to queries from overseas.
College of Science
University of Canterbury
Private Bag 4800
Phone: +64 3 364 2178
Fax: +64 3 364 2490
Email: [email protected]