# Can I re-use HNO3+H202



## pimpneightez (Apr 30, 2012)

Im planning on using a 50/50 blend of HN03 and H2O2 to strip a bunch of keyboard mylars. I was just wondering if I could also use this solution for silver plated items and contactor points. Would it be wise of me to drop the silver after the mylars? Then can I still use the solution for my silver plated items and contact points or should I do them seperatly too? Do I need to treat the solution with anything before re-claiming more silver?


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## goldsilverpro (Apr 30, 2012)

Most silver plating is done on copper based objects. You can't use nitric to strip the silver because it will eat copper base metals faster than it will eat the silver. You can use it for contact points.


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## MysticColby (Apr 30, 2012)

After you use nitric/H2O2 to dissolve silver from mylars, you could probably still use that nitric/H2O2 on other silver items. It's good to be used until it runs out of nitric. If you were going to drop the silver with copper cementation or nacl, do that after using all of the nitric (not between steps). adding copper will consume all of the nitric before it cements silver. adding nacl will precipitate the silver, but also immediately precipitate any future silver added

"50/50 blend of HN03 and H2O2" - is this equal volumes of 70% HNO3 and 3% H2O2? I've always wondered what proportions of these should be used.


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## pimpneightez (Apr 30, 2012)

ok, makes sense. what's the best method for plated silver dinnerware a silver cell?


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## goldsilverpro (Apr 30, 2012)

Are you sure you don't mean H2O (water) and not H2O2 (hydrogen peroxide)?

Some on the forum have had some success with the sulfuric cell and a few other methods. I guess you'll have to search for them.


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## pimpneightez (Apr 30, 2012)

I am under the impression that H202 is better to use than water because it surpresses any NOx gases. I could be wrong but distilled water will work just fine as well.


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## samuel-a (May 1, 2012)

pimpneightez said:


> I am under the impression that H202 is better to use than water because it surpresses any NOx gases.



Yes, to some extant H2O2 is more usefull to suppress the NOx then plain H2O. It does so effectively until all H2O2 is depleted. H2O2 will be used up by the reaction it self, but also decompose slowly in time. Heat also rapid the H2O2 decomposition.

Silver reaction to nitric acid:
3 Ag + 4 HNO3 = 3 AgNO3 + *NO* + 2 H2O

The NO(g) generated by the reaction with Silver, is re-oxidized by the water (or H2O2) to form back Nitric acid and hydrogen.
There are many side reactions going on, so i'm not sure i can cover or even understand how the entire dynamics works.
But if you simplfy that to just the reaction of NO(g) with water or peroxide, you could see that H2O2 is more efficiant then plain water in terms of Nitric acid regeneration by factor of 2:1:
NO + 2 H2O = HNO3 + 1 1/2 H2
NO + H2O2 = HNO3 + 1/2 H2

Meaning, it takes half as much Peroxide molecules then Water molecules to produce the same amount of Nitric acid molecules.



pimpneightez said:


> I could be wrong but distilled water will work just fine as well.


Chemically speaking, that would be wrong.
Though, given the prices of H2O2, i think it can be either right or wrong, that depends on the operator's other costs (of nitric acid) and demands (pollutants).

While dissolving pure Silver (such in mylars) in cold 50/50 nitric/water solution, NOx discharge is minimal.
Silver, having monovalent propeties is special in that way. Even if the solution is very hot, NOx discharge is negligible compared to if you would have dissolved Copper /Nickel or other base metals having divalent or trivalent properties, so as the acid consumption.

-----------------
As a side note i would also add, that the silver is quite pure on them mylars, i see no reason to cement it with copper and therefore severely contaminate it.
The best way i have found to treat pure silver in nitrate medium is to precipitate Ag2O with NaOH and reduce it with sugar. 
I'v also had good sucsess evaporating AgNO3 solution to dryness and direct melting of the crystals from there, though it requires ventilation and scrubbing of the NO2 fumes coming off the furnace.


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## philddreamer (May 1, 2012)

Hi Sam!


> As a side note i would also add, that the silver is quite pure on them mylars, i see no reason to cement it with copper and therefore severely contaminate it.
> The best way i have found to treat pure silver in nitrate medium is to precipitate Ag2O with NaOH and reduce it with sugar.
> I'v also had good sucsess evaporating AgNO3 solution to dryness and direct melting of the crystals from there, though it requires ventilation and scrubbing of the NO2 fumes coming off the furnace.



Can the silver nitrate, after properly filtered, be used in a silver cell, thus recovering the pure silver crystals?

Just a thought.

Phil


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## samuel-a (May 1, 2012)

philddreamer said:


> Can the silver nitrate, after properly filtered, be used in a silver cell, thus recovering the pure silver crystals?
> 
> Just a thought.
> 
> Phil



Sure, i see no reason why not to.
But you need to know the concentration, give or take.


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## butcher (May 1, 2012)

I believe, but I could be wrong:
If dealing with silver from Mylar you may use more solution than needed, unless the solution was saturated with silver, from heating and adding Mylar till no more silver would dissolve, so there can be possibly un-reacted nitric for the cell (you could add more silver to this solution if needed).

I would think AgNO3 solution if there was no free nitric in solution would contain a certain amount of silver per weight of solution, water being the only factor throwing this off, which if you knew the concentration of the acid to begin with, you should have a clue of the silver concentration of the silver nitrate solution, as long as no free HNO3 was involved (of course some loss from gas and heating in the reaction but I would think that this should not throw off figures too much.

Dirt and oils from the Mylar would be a concern I would have, this may not be that much of a problem if your careful in handling the Mylar’s (I do not know).


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