# Silver Oxide and Hydrogen Peroxide



## MysticColby (Sep 18, 2013)

Background:
I have films that might contain silver. They are 8"x10", used for western blots. I took 1000 of them, put them in a 5-gallon bucket, filled with water, added 100g sodium hydroxide, stirred, waited, added another 100g sodium hydroxide, stirred, waited. When there was no more visible spots on the films, I rinsed them in another bucket of water and pooled the buckets. I let it settle for a week (very slow to settle...), then decanted it through a filter, then transferred the black muck at the bottom into a 1L beaker.
Before I started this, I did some reading. During that time, it was suggested that you could add hydrogen peroxide to silver oxide to convert it to metallic silver (as an alternative to karo syrup).
I wanted to try this, as I've never been able to get karo syrup to work, so I added 100ml 30% hydrogen peroxide to the beaker a little at a time with stirring in between. It bubbled a lot and for a long time and got warm. I let it settle overnight, and now there is about 150ml of silvery/grey powder precipitated. I'm optimistic it's silver.

That's where I am at now. My questions: has anyone else used hydrogen peroxide like this before? how does people's experiences with karo syrup compare? how much hydrogen peroxide is needed? (this time I pretty much just kept adding it until there was much less bubbling from further additions)

edit:
Also, what's going on molecularly? My guess:
silver-halide + NaOH -> AgOH + Na-halide
2AgOH -> Ag2O + H2O
Ag2O + H2O2 -> 2Ag + O2 + H2O

based on this, it's 1:1 silver oxide and hydrogen peroxide.
100g silver oxide / 231.735 g/mol = 0.4315 mol
0.4315 mol hydrogen peroxide * 34.0147 g/mol = 14.678g hydrogen peroxide
14.678g hydrogen peroxide / 1.135 g/ml = 12.932 ml 100% hydrogen peroxide
12.932 ml 100% hydrogen peroxide / 0.3 = 43.1ml 30% hydrogen peroxide
100g silver oxide = 93.096g silver
but silver will increase the rate of decomposition of hydrogen peroxide. how much is required is probably proportional to how quickly you add it.


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## butcher (Sep 19, 2013)

Great post.
I have noticed when adding the H2O2 to the top of the powders and too fast, the reaction can be almost violent with a cloud oxygen and steam gases, and heat of the reaction assists to drive off the gases, adding the H2O2 with a pipette the solution evolves gas as soon as it touches the surface of the powdered solution, my point is how it is added can be a big factor in how much of the H2O2 would be needed, and how well the H2O2 could mix with the silver powders.

Dumping the hydrogen peroxide seems to just react strongly with the top layer of powders, and seems to gas off much of the H2O2 as steam and oxygen without reacting with the silver powder under this top layer.

I found stirring to create a whirlpool of solution, and using a pipette to slowly drip the H2O2 solution into the bottom of the jar or into this whirlpool which quickly stirs the drops of peroxide into the powders, helps to keep the H2O2 in solution longer to react better with the silver chloride and sodium hydroxide,


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## goldsilverpro (Sep 19, 2013)

If the film has been developed and is, therefore, black, the silver on the film is in the form of silver metal. If that is the case, there are no chlorides of bromides present, and, therefore, no silver chloride or silver bromide will be formed. Therefore, neither Karo or H2O2 will be needed.


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## MysticColby (Sep 19, 2013)

gsp, that is very good to know! about half of the films were already developed, some with more black than others (I'm surprised with how many undeveloped films are thrown away at my work)
when I added the H2O2: beaker with 500ml liquid with powders in suspension. stir to resuspend, pour in a little H2O2, stir again, let sit. It seemed to take about 5 min before anything apparent happened, then it looked like it was simmering (mild boil) and got warm. I guess I didn't add enough to get the instant hot gasses. Or most of it was already silver (regarding gsp's post).
Currently I'm letting it settle, then will decant through a filter, then filter the powders, then melt. Unfortunately, it clogs filters much faster than, say, cemented silver. finer particles? presence of gelatin?
I'm looking forward to getting silver from work waste.


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## goldsilverpro (Sep 21, 2013)

The gelatin is what makes it hard to filter.


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## Lino1406 (Sep 27, 2013)

Hydrogen peroxide acts as a reducer?
More rational the product seems to be Ag2O, not Ag


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## butcher (Sep 27, 2013)

H2O2 can act as a reducer for silver in caustic solution.

2 AgCl (s)+ 2 NaOH (aq)--> Ag2O (s)+ 2 NaCl (aq)+ H2O (l)
then
Ag2O (s) + H2O2 (aq) --> 2Ag (s) + H2O (l)+ O2 (g)


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## Lino1406 (Sep 27, 2013)

Sorry indeed in alkaline environment, the couple Ag/Ag2O is indeed
cathodic to HO2-/O2 by 0.4v


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## Westerngs (Sep 27, 2013)

> Unfortunately, it clogs filters much faster than, say, cemented silver. finer particles? presence of gelatin?



You might try mixing in some diatomaceous earth before you filter. It sometimes helps hard-to-filter solutions filter easier.


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## goldsilverpro (Sep 28, 2013)

I used to leach the emulsion/silver film sludge with about a 15% (by volume) sulfuric solution. I'm thinking I added the necessary dilution water to the sludge in a bucket, stirred it, added the correct amount of sulfuric, slowly stirred it, and let it sit for a day, or so. Put the bucket in a plastic tray while doing this. It can get quite hot. Don't try to filter it hot. It neutralizes the NaOH in the sludge, solubilizes some of the emulsion, decreases the sludge volume, and tends to make the filtering go faster. I think I got the idea from a patent. Try a small sample to see how it goes. Rinse several times before drying and incinerating.


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