# Problem converting silver chloride to elemental



## elfixx (Jan 8, 2009)

Ok ill start from the begining. I runned a 6k gold batch in hot pure sulphuric acid to remove silver and then process the remaining gold in AR(I had no nitric left.... and i'm still waiting for it :\ ) The solution yeilded a mix of silver chloride and powdered-honeycombed gold. I then decanted and washed this powder and processed it directly in AR. I then nutralised with urea, filtered most of the silver chloride and puted it away, drop gold using storm precipitant, etc... Then I converted the chloride using 10% HCL and Aluminium foil, decanted and puted the remaining supposed silver in a crucicble. I then tryed to melt this powder but it wont melt using a strong oxy-acet torch, it instead form sponge like stuff. Anything I've done wrong or some kind of chemical reaction because of the sulphuric or AR I missed?? Anyone got a idea what I could do to recover the silver?


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## peter i (Jan 9, 2009)

Adding a little borax when melting silver powder is a very good idea. It makes it flow nicely.
Sometimes silver powder behaves a little funny when melting. I think that remaining silver chloride and probably some aluminium oxide covering the powder is responsible. These should dissolve in the flux, making the silver flow.

If you have sulphate ions and silver ions, they are very likely to precipitate as silver sulphate, which is rather insoluble.
It should still melt at around 650°C, so that's probably not your problem.


Flux and heat should do the trick.


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## elfixx (Jan 9, 2009)

Ill try this right away and come back to you with result


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## elfixx (Jan 9, 2009)

Adding borax flux isn't working... it stays in this kind of sponge form


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## elfixx (Jan 9, 2009)

Wow sumthing realy wierd just happened... I tryed to melt this thing up once again with a very very strong flame, a liquid formed in my crucible and when I tryed to drop it into water IT EXPLODED! no joke.... can anyone tell me what the h""" was that?


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## qst42know (Jan 9, 2009)

You should cement your silver chloride to silver metal before you try to melt. Watch Steve's videos and read the posts on the process.


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## butcher (Jan 9, 2009)

some silver compounds make expolsives temperature and shock sensitive,
gold and most metals can be made into explosives but I think silver and mercury may just be easier Im not well educated to give many details.


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## qst42know (Jan 9, 2009)

I recall reading that vapors from some silver compounds when melted can cause permanent blindness, though I don't remember which ones. Perhaps I am mistaken? 

This alone should be compelling enough to learn to cement silver to metal before melting.

Anyone recall this as a safety issue with silver? 

Lou?

I did not hit on the melting exactly however if you work with silver you should read this.

http://books.google.com/books?id=nDhpLa1rl44C&pg=PT146&lpg=PT146&dq=blindness+silver&source=web&ots=zKUiTTHthP&sig=IqSKwae2-jP9AQcWTWwsivvL8GY&hl=en&sa=X&oi=book_result&resnum=9&ct=result

I have been reading this book and though it will take some time to get through it seems many of the metals and their compounds that refiners come in contact with are covered. Definitely worth a look.


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## SilverNitrate (Jan 9, 2009)

you may have silver chloride... try melting this (mystery silver substance) with baking soda. 
Silver chloride will like explode if moisture is in and you're heating to very high temps very quickly... 
On large scale silver chloride and soda mix should be held about 350f for 24h or longer (because silver chloride don't dry easily)
Cementing silver chloride should be done the sulfuric acid/iron or sulfuric acid/aluminum method


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## elfixx (Jan 10, 2009)

Nvm.. i'm a newb lol... Iwas using my new set of torch i just received and wasn't used to it. I just didn't set the flame properly to acheive high enough temp.... I tryed again to melt my silver and it worked fine. In fact the explosion I experienced was overheated borax flux I added previously wich turned to liquid glass and when dropped in cold water it kinda exploded... I guess... and my silver was cemented metalic silver, I dont usualy try to melt silver chloride because of the dangerous gas formed and when I do, I do it under my fume hood. Safety first :wink:


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## Lou (Jan 10, 2009)

Looks like it's time to clear up some bad ideas!


qst42know,

You speak of silver nitrate--it reduces itself to a black film of silver metal on your eyes, giving you ''black eye''. This is what happens when you get dust of luna salts in your eyes, or even when you melt it. 

My great concern would be handling silver chloride--to me that would seem the most likely to cause blindness and this is why:

To the rest of you--

Melting AgCl is asking for trouble. When you melt silver chloride, don't think that it just sits there; it has a vapor pressure and it is evaporating into the air and it's likely attaching itself to various parts of your mucous membranes. Now one might be thinking that it's very insoluble and extremely stable and that Ag+ ion isn't _that _poisonous. However, it's the physical damage that little pieces of AgCl can do to your lungs, eyes, and nose that you should be worried about. It gets stuck onto these surfaces very easily and is an irritant--it doesn't like to come off, and its insoluble enough that it's hard to remove via your body's natural processes. Just because you can't see the AgCl in the air you breath doesn't mean that it isn't there (although usually there's a white smoke). If you're going to melt AgCl or do a process (i.e. Miller Chlorine) that produces it, you are well advised to do it in the drought of a hood or else do it with a SCBA. 

SilverNitrate gives good advice--it is far better to hold any mixture of silver chloride at a moderate heat before drastically raising its temperature. AgCl loves to soak up moisture and doesn't release it. That's why it's notoriously hard to dry it and you run the risk of a steam explosion if you heat it suddenly.


One thing that I advise against is using aluminum of any type to cement out silver. Keep aluminum out of it. Aluminum is difficult to completely remove from any metal that we process as refiners. It will require the use of excess flux to dissolve the alumina formed as the hydrolysis product. 

I greatly prefer zinc to anything else for reducing because it's quick, clean, and easy to remove residuals.


Lou


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## Juan Manuel Arcos Frank (Jan 10, 2009)

Yeah,Lou is right...zinc will work lovely to reduce the silver chloride.Another option is using iron (i. e.common nails) with a little bit of sulphuric acid (common acid battery),here is the process:

Using all the safety recommendations,add the nails to the silver chloride,add a little bit of water then,carefully, add some sulphuric acid,stirr until all the white silver chloride changes to a dark mud,wich is pure silver,remove the nails,wash the dark mude with tap water,dry and melt...you will get pretty fine pure silver.

Manuel


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## Harold_V (Jan 10, 2009)

I used aluminum routinely for converting silver chloride to elemental silver and can attest, it's difficult to rinse from the solution, although not impossible. I allowed plenty of time for the silver to settle, then would decant via a hose. I rinsed my silver no less than a half dozen times, then I'd dry it for melting. I had no problems in melting, although it was important to melt with some borax. 

Given a choice, I'd avoid using aluminum, although my experiences were not troublesome. That would not have been the case had I tried to filter instead of rinse well and decant. Solutions that contain dissolved aluminum border on the impossible to filter, at least in my experiences. 

Harold


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## hrushi (Jan 11, 2009)

Read my post Recovering Silver from Silver Chloride


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## Juan Manuel Arcos Frank (Jan 11, 2009)

Harold_V:

Can we use an aluminum slab dipped in the silver chloride for convert it in pure silver?.

Do you recommend us a special aluminum shape?.Do we need to add any acid?.

Harold,thanks in advance for sharing with us your great experience.

Regards.

Manuel


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## Lou (Jan 11, 2009)

I'd recommend against aluminum for many reasons. I covered most of them here:

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=3681&highlight=aluminum

I'd stick with zinc, iron, or copper. Zinc is my personal favorite because it washes out the best.


Lou


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## peter i (Jan 11, 2009)

I used to use the silver chloride-aluminium method, but has seen the light, and use copper cementing now.
The silver powder from aluminium reduction was a pain, but usually behaved after addition of quite a bit of HCl and some boiling.... compared to copper: Not worth the trouble.

If I have some very dirty silver, I may still precipitate as chloride (that can be washed thoroughly), but after that I will use zinc strips to reduce it to the metallic state.


IMHO silver chloride- washing- zinc reduction-wash with HCl has a role for people who want to reclaim small amounts of silver, as they will get a reasonably pure product (e.g. to alloy for casting).
Cementing with copper will leave quite a bit of copper in the silver, and has to be followed by an electrolytic refining (after which a top grade product is obtained).
But setting up even a small cell is not something you just do, unless you have quite a bit of metal to refine.


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