Science Buddies: "Ask an Expert"

Does the level of vitamin C change as the juice gets closer to the expiration date? Can you use baking soda as a starch solution for titration with iodine?

Hi,

Vitamin C is very easily destroyed by the oxygen in the air, so when the orange juice container is opened the vitamin C content will start to drop. If any air is in the container or can get in during storage the same thing will happen, so, to answer your first question, yes the vitamin C content will probably drop as the expiration date is approached.
I am somewhat confused by your second question. Are you trying to use baking soda instead of starch in the titration of vitamin C by iodine? If so, I do not think it will work. The titration end point is detected by the formation of a starch iodine complex that would not form between iodine and bicarbonate. Here are some descriptions of the assay:

http://www.outreach.canterbury.ac.nz/ch ... iodine.pdf

Here is a science buddies blog on the experiment from an earlier year:

https://www.sciencebuddies.org/science- ... ?f=1&p=670

Hope this answers your question.

Best wishes,

Barrett Tomlinson