2
$\begingroup$

I would like to perform a permanganometric titration of hydrogen peroxide at home following a procedure similar to http://www.titrations.info/permanganate-titration-hydrogen-peroxide, i.e. the reaction:

2MnO4- + 5H2O2 + 6H+ → 2Mn2+ + 5O2 + 8H2O

I do not have sulfuric acid or a licence. Can I use any other acids? I think HCl would release chlorine, and other than that I only have weak household acids such as acetic, ascorbic, citric and tartaric to hand. I can probably get hold of others, but sulfuric is regulated as an explosives precursor here.

$\endgroup$
  • 2
    $\begingroup$ If you use an organic acid, you will probably oxidize this acid with permanganate, with or without $\ce{H_2O_2}$. If you are not allowed to use sulfuric acid, why don't you use phosphoric acid $\ce{H_3PO_4}$? $\endgroup$ – Maurice Mar 25 at 17:08
  • $\begingroup$ Thanks. That's exactly the sort of thing I'm looking for. Would there be any extra interactions between phosphoric acid and the H<sub>2</sub>O<sub>2</sub>? $\endgroup$ – eisd Mar 25 at 17:54
  • 1
    $\begingroup$ No, phosphoric acid is notmoxidisable as P is at its highest oxidation state $\endgroup$ – Waylander Mar 25 at 19:33
  • $\begingroup$ You could also use Nitric acid, although concentrated nitric acid is rather corrosive and produces horrible fumes. Plus, if I'd expect any acid to be labeled as an explosives precursor, It'd be nitric. $\endgroup$ – mpprogram6771 Mar 27 at 21:11
  • $\begingroup$ I would like to accept your comment as the answer, @Maurice. $\endgroup$ – eisd Apr 13 at 12:35
1
$\begingroup$

Don't use the organics!

This will severely mess up your titration because both permanganates as well as H2O2 will oxidize the carboxylic acids into explosive or corrosive things like peroxyacids (-C(O)OOH). Carboxylic acids are also usually weak, and the peroxy versions can be up to 1000 times weaker.

On the bright side, HCl is a strong acid, and you shouldn't have to worry about the production of chlorine gas; the only chlorine product should be MnCl2. However, since so much O2 Is being produced, your MnCl2 might contain a small amount chlorate impurities, so be wary of that if you plan to use the manganese chloride in the future.

| improve this answer | |
$\endgroup$
  • $\begingroup$ I was just wondering whether I should follow up asking whether my assumption about HCl was valid. So, it would be safe? I read it produces Cl2, but this then forms HCl and HOCl rather than being released. Sounds like this could also cause titration errors, but maybe small. $\endgroup$ – eisd Mar 28 at 11:02
  • $\begingroup$ The major products of using the HCl should strictly be Manganese Chloride. However, as I stated, some things like chlorates will be produced, but I'd be very surprised if a measurable amount of chlorine gas formed. $\endgroup$ – mpprogram6771 Mar 28 at 20:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.