RogueRose
International Hazard
Posts: 1585
Registered: 16-6-2014
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Catalyst (acid?) for oxidizing with NaOCl - Does this help and what would be best?
I was doing some tests with how effective 12.5% NaOCl is at oxidizing various metals and compounds and am working with Cu, Pb and "red lead" (Pb3O4).
I added some NaOCl to Cu wire and got a blackish solution and in another beaker (Cu wire) I added a few drops of 54% H2SO4 (to about 50ml of NaOCl)
and the solution turned blue/greyish and looked like it had floating chalk that eventually disappeared - the solution started to emit bubbles from the
wire and the grey solution eventually turned more black.
I'm guessing the H2SO4 made some CuSO4 which was eventually broken down to CuO but it still seemed to work faster than the mix without the few drops
of H2SO4.
I'm wondering if trying to oxidize with NaOCl, does the acid work as a catalyst or is it a side reaction? Is there something that will speed the
reaction - if it is an acid, what would be best (not HNO3 - an alternative as I don't have any now)?
When I did add the drops, the localized area bubbled fiercely and I thought it might have been wasted. Should a more dilute H2SO4 be added or is this
alright?
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Sulaiman
International Hazard
Posts: 3558
Registered: 8-2-2015
Location: 3rd rock from the sun
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hydrogen peroxide may help as it is slightly more electropositive than hypochlorite, permanganate may also help.
Pb(IV) is just a little more electropositive than ClO- so it is not surprising that the reaction did not work as expected.
https://en.wikipedia.org/wiki/Standard_electrode_potential_(data_page)
EDIT: if you have sulphuric acid and a nitrate then you have nitric acid 
i.e. it may be that adding a nitrate salt to the mixture will generate nitric acid in-situ, which would make lead dissolve more quickly,
nitric acid is an oxidising acid and forms lead nitrate easily, the stronger sulphuric acid then forms lead sulphate, regenerating nitric acid.
So the least contaminating nitrate to try would be lead nitrate.
All guesswork, never tried.
[Edited on 23-5-2017 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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