[spirochete]

These questions relate to the secondary coulometric titration of vitamin C.  In this titration an applied voltage is used to generate a current that oxidizes Iodide to I₂.  I₂ then oxidizes vitamin C.  A starch indicator detects excess I₂ via the formation of I₃^-

My questions are:

1) What direction does the current flow in this type of experiment?  I would think from the voltage source, to the anode, then to the cathode then to the amperometer (sp?) then back to the voltage source? 

2)   What is happening at the cathode here?  I know at the anode Iodide is oxidized.  But I can't figure out what's going on at the cathode.

3) If the leads are reversed, what happens at the anode?

Thanks!

[Borek]

What material are electrodes made off, what other substances (apart from vitamin C and iodides) are present in the solution.

[spirochete]

Water, K+ ion and starch indicator.  The starch just reacts with the triodide though.

I assumed the electrodes were inert?  Do I need this info to answer the questions?

[Borek]

Water, K+ ion and starch indicator.  The starch just reacts with the triodide though.

So the only thing that can react on the other end is water.

I assumed the electrodes were inert?  Do I need this info to answer the questions?

If they are inert - no.