# Ag(OH, I, O) -- what to do with it?



## roving_chemist (Mar 7, 2016)

I have ~100g of a mixture of AgI, Ag2O, and AgOH lying around, 99.99% trace metal basis. Is there a good way to reduce this to the metal while keeping the purity? First post, please be kind.


----------



## FrugalRefiner (Mar 7, 2016)

roving_chemist said:


> I have ~100g of a mixture of AgI, Ag2O, and AgOH lying around, 99.99% trace metal basis. Is there a good way to reduce this to the metal while keeping the purity? First post, please be kind.


When you say you have "a mixture of", do you mean you have some of each that are in separate containers, or do you mean they are all mixed together in a single container?

Dave


----------



## roving_chemist (Mar 7, 2016)

They're all homogeneously mixed. We were doing an ion exchange reaction in the lab on a large scale:
R+ I- --Ag2O--> R+ OH- + silver stuff
Instead of throwing it out, I decided to keep it and see if I could get anything useful out.


----------



## solar_plasma (Mar 8, 2016)

I would decompose it by heat, while distilling/sublimating off the iodine for reuse. Once the iodine is gone, the silver oxides will decompose further by more heat in a melting dish and melt to pure silver.

Probably there ist also a soda ash route, which I am not sure about. Maybe others can tell.


----------



## g_axelsson (Mar 8, 2016)

solar_plasma said:


> I would decompose it by heat, while distilling/sublimating off the iodine for reuse. Once the iodine is gone, the silver oxides will decompose further by more heat in a melting dish and melt to pure silver.
> 
> Probably there is also a soda ash route, which I am not sure about. Maybe others can tell.


The silver oxide and hydroxide would just break down from heating, but I don't think you can do the same thing with silver iodide. That's a stable compound even under heating, with a boiling point at 1,506 °C and no mentioning of breaking down on the wikipedia page.
https://en.wikipedia.org/wiki/Silver_iodide

I see two roads ahead, one is to separate the iodide from the hydroxide and treat the two fractions in different ways.
The other is to turn silver iodide into silver oxide first and then melt it. Silver chloride is easily turned into silver oxide by addition of sodium hydroxide. My guess is that the same process works with silver iodide but that's nothing I've ever tried.

Personally I would try the second method but I would start with a couple of test tube experiments.

For more on silver hydroxide this is a good discussion.
https://www.researchgate.net/post/At_what_pH_does_silver_hydroxide_formation_take_place

Göran


----------



## solar_plasma (Mar 8, 2016)

That I can remember so wrong.... :roll: 

I worked with silver iodide. I have to find my old posts to find out how I converted it.


----------



## solar_plasma (Mar 8, 2016)

http://www.chf.de/eduthek/wuchu/1996_3.pdf page 19, "Reduktion der Silbersalze zu Silber"

I tried this method that worked best for me: reduction by iron (recovers 93%), water, excess iron powder, 15 min at 50°C, then remove iron by a magnet, filter, silver washed with HCl, then with water

Sorry I have confused it with decomposing of gold iodide and thanks to Göran!


----------



## g_axelsson (Mar 8, 2016)

Thanks Björn, that was a very good pdf to read, but my German is a bit rusty... 8) 
Saving that for later.

Göran


----------



## Lou (Mar 8, 2016)

Best way of dealing with AgI is fluidized bed and hydrogen gas. The HI can then be reused as a solvent for the PGMs, at which it and HBr truly excel at.


Lou


----------



## upcyclist (Mar 8, 2016)

Lou said:


> Best way of dealing with AgI is fluidized bed and hydrogen gas.


I'm not even going to bother pretending I know what he's talking about


----------



## solar_plasma (Mar 8, 2016)

upcyclist said:


> Lou said:
> 
> 
> > Best way of dealing with AgI is fluidized bed and hydrogen gas.
> ...



I, too, needed to google it :lol: looks like it would work as a coffee machine, too 8) 

Lou, would the silver iodide be suspended in water and would this method work at room temperature? Will the HI stay in that solution, so I can decant from the silver and use this HI solution as is?


----------



## Lou (Mar 8, 2016)

No.

The thermodynamic driving process is the formation of a gas (HI) that is removed from the system. One can easily do this in a quartz tube.

The conversion of AgCl with H2 gas is well documented and has been used by several larger operators. With control of temperature, comes also control of particle size.

Lou


----------



## roving_chemist (Mar 8, 2016)

This one interests me the most. I happen to have a lot of Vycor tubing (96% silica, 4% sodium, super high melting point) and a bunch of quartz wool lying around. Do you think that trace of sodium could lower the purity?

What kind of temperatures are we talking about here? Something that a propane torch could spit out?

I forgot to mention, the stuff isn't really a powder. It's more of a chunky aggregate of fine particles. Would the surface of these chunks reduce to the metal, passivate them, and prevent the rest from reacting?

Also, where do I get the hydrogen?


----------



## solar_plasma (Mar 8, 2016)

Your nick name leads to the assumption you are a chemist, but if you need to ask where to get H2, then it is my impression, you would be better off to use the reduction on iron. The silver salt chunks have just to be powderized, -this should not be a great challenge.


----------



## roving_chemist (Mar 9, 2016)

Wow, that has to be one of the dumber questions I've asked. Strong non-oxidizing acid + metal, aluminum + NaOH, etc. I'm getting too old for all-nighters.


----------



## solar_plasma (Mar 9, 2016)

If you really want to use Lou's advanced method, I think you should have compressed H2 at hand, otherwise the whole setup and spent chemicals and metals, not even considering the treatment of the waste, will be eating up the profit you expect from only 100g of silver salts...what might it be, two or three ounces...20-30$ ?!

If you need half a mol H2 only for the stoichiometry, that's 11.2 L gas, most of the gas will pass unreacted in a simple setup, so it will probably take twice that much or more...just saying.

In fact I have processed silver at higher cost, but since there is a cheap and easy method, I cannot follow you.


----------



## roving_chemist (Mar 9, 2016)

I'm an amateur chemist on the side. I'm not really looking to sell it, I just want to go ahead and make it. It's a case of the thrill of the chase, not the catch itself. If I'm successful, I'll probably end up with an unusual paperweight and bragging rights. As for the cost, you wouldn't believe what I have just lying around left over from previous endeavours.


----------



## roving_chemist (May 18, 2016)

I found a way to dissolve the AgI in a paper about cloud seeding. Here's the relevant bit:



> Although silver iodide is highly insoluble in both water and organic solvents, it is nevertheless quite soluble in water or acetone Solutions of a soluble iodide, such as iodides of sodium, potassium, ammonium, etc. Water solutions containing upwards of 20 percent by weight of silver iodide can be made by dissolving silver iodide in a saturated solution of sodium iodide. However, if these water solutions are diluted by adding water, the silver iodide precipitates out. Therefore, water solutions have the disadvantage that they cannot be readily diluted to any desired concentration. Acetone solutions, on the other hand, can be diluted with acetone to any concentration without precipitation of the silver iodide. Accordingly, acetone solutions are used in all of this work. These acetone solutions can readily be made by dissolving silver iodide and sodium iodide in acetone using about 4 parts by weight of silver iodide to 1 part by weight of sodium iodide.



Now that I can dissolve the iodide in acetone, can someone recommend a good reductant?

As a side note, I now have ~135 grams of the stuff (more coming!), which corresponds to ~97 grams of silver.


----------

