[pcm81]

Trying to get a ballpark accuracy check of an ORP probe. Is it possible to mix a diy solution using oxalic acid or KMnO4? Trying to get within 100 mv check without spending $50 of real solution.

[Borek]

Sounds easily doable. 100 mV/59 mV ≈ 1.7, that means 100 mV is more or less equivalent to change in concentration by a factor of 50.

I am not sure permanganate is the best idea though, potential depends quite heavily on the pH ([H⁺]⁸ in the reaction quotient).

[pcm81]

Sounds easily doable. 100 mV/59 mV ≈ 1.7, that means 100 mV is more or less equivalent to change in concentration by a factor of 50.

I am not sure permanganate is the best idea though, potential depends quite heavily on the pH ([H⁺]⁸ in the reaction quotient).

Thanks for the answer. Would oxalic acid be a better choice? Is there some literature I can reference for orp vs concentration material? You gave the equation, but I'd like to learn the rest... are there orp tables that contribute to the orp of the solution? Google search for orp is flooded with links to health nuts trying to sell stuff...

[Borek]

Google Nernst equation, that's the starting point for any redox potentials.