Australia's Science Forum

Has anyone done the Vitamin C prac from Science Focus 4 ?
I am getting a colour change with the different orange juices but no change in the starch/iodine solution with DCPIP
There is a colour change when I add the OJ to the DCPIP so am baffled why there is no change with the starch and DCPIP
Any ideas ?

i thought that starch and DCPIP is test for vitamin C, and iodine for starch

We never did this experiment but I searched and apparently you need to do titration
http://biology.clc.uc.edu/fankhauser/la ... tocol.html

Its a starch suspension with iodine added for purple colour......then add DCPIP drop by drop until colour changes to clear. My DCPIP is bright blue when made up...is that right ?
Then test each OJ by the same method. Colour should then be clear.
When I add OJ to DCPIP the colour goes to clear...so it works in reverse.

Do you allow the students to do this? Only that according to CSIS DCPIP is an orange dot and therefore can only be used with seniors. Just curious to what everyone does, as I used to make it up, thinking that the solution would be OK for juniors, but it doesn't actually say that in CSIS, so I stopped making it for them. They have to use the starch method now.

Hi Smeee, I'm confused why should the DCPIP have the same colour change with the starch as the OJ does? And why do you need it to? Aren't the starch and DCPIP tests just 2 different methods for testing the same thing? They are for measuring vitamin C in the OJ. Neither the iodine solution nor the DCPIP contain vitamin C so I imagine they wouldn't go clear when added together. But, perhaps I've got it wrong...

Hi Dime
We only use it for 11& 12 here

Thanks lurra