# Trouble processing silver with sulfuric acid



## Silverdan (Aug 27, 2020)

I am hoping someone can help me as I think I may have screwed up bout 100 ounces of sterling silver. So when I dissolved the items in the sulfuric acid I wound up with nothing but a gray sludge I even added a lot more acid and still the same. Can someone please help me in the right direction?


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## Refining Rick (Aug 27, 2020)

Why did you use sulfuric acid and not nitric acid?


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## galenrog (Aug 27, 2020)

I am with Rick on this. Why sulfuric acid? It makes no sense to my stroke addled brain.


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## Silverdan (Aug 27, 2020)

Unfortunately I ordered the wrong stuff and it was an oversight. I have ordered nitric acid, what can I do to recover?


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## conglioa (Aug 27, 2020)

Silverdan said:


> I am hoping someone can help me as I think I may have screwed up bout 100 ounces of sterling silver. So when I dissolved the items in the sulfuric acid I wound up with nothing but a gray sludge I even added a lot more acid and still the same. Can someone please help me in the right direction?



Can you provide some pictures?
I'm not sure what you did, but maybe you should do it this way with sulfuric acid:
1. Completely dissolved with concentrated sulfuric acid.
2. Heat until all mixture is white fuming and thickens.
3. Allow to cool and mix the thick mud with 5 parts water, heat for a few hours.
4. Filter to extract the solution and then your silver will be in the form of Ag2SO4 solution.
You can separate silver from solution in several ways such as copper cement or AgCl precipitation
You must ensure absolute safety because hot thick sulfuric acid is dangerous you probably understand that too.


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## Lino1406 (Aug 27, 2020)

I wonder what was your plan, but silver dissolves in hot sulfuric, much like nitric acid. If precipitation is next, same way


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## nickton (Aug 28, 2020)

Supposedly Hoke mentions it somewhere, and here's a link to one of Sreetips' videos on using sulfuric for silver refining: https://youtu.be/pdzSmGYbzqk.


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## Martijn (Aug 28, 2020)

Suggesting a new member should try experimenting with a large volume of hot (concentrated :shock: ) sulphuric is not something I would do. 
Maybe recovering the silver the way Hokes describes? Other members may have more suggestions on how to proceed. 
Study and read a bit more first. The silver will stay there waiting for you with a plan. 
The fact that you did not notice or checked your acid tells me you have some more to learn first. (and not from You-Tube)
When you try something, use small amounts in test tubes. You won't mess up a lot and keep it safe to get familiar with the reactions. 
How strong is the sulphuric acid you used? Silver sulphate is not very soluble in water, like half a gram in 100ml, I don't know how much concentrated sulphuric can hold. It may have all reacted and then dropped out because of oversaturation. not sure.
https://en.wikipedia.org/wiki/Silver_sulfate
I guess the sludge in the bottom is silver sulphate with some base metal sulphates. 
Be very carefull with sulphuric acid.

Martijn.


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## Silverdan (Aug 29, 2020)

I have processed it with 98% sulfuric, it is cemented I think into a dark gray semi hardened state. I have 2 different batches. This one in the picture I stopped because I thought when it was processed the acid was supposed to be clear? And as far as experimenting with hot sulfuric acid I’ve already had my trial and error experiences. 
What do you suggest filtering with?
What is the process after filtering?


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## geedigity (Aug 29, 2020)

Concentrated sulfuric acid will dissolve silver, however, the amount of silver dissolved is less than desirable. It is also possible that the sulfuric acid while dissolving the silver will make a silver mud. In order to clean up the issue, I would dilute the solution with the silver mud using some distilled water, and filter the mud from the liquid. Save the liquid and rinse the mud several times using distilled water all while accumulating the liquid. I would then add HCl to the accumulated liquid to make silver chloride and convert the silver chloride using the many options available. I would then mix in some sodium carbonate in with the silver mud and melt the mixture and pour off the molten silver and form a bar. Then I would dissolve the silver bar using nitric acid and distilled water.


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## Martijn (Oct 2, 2020)

Silverdan, how did things go? I sure hope you diluted the acid by pouring it in cold water, not pouring water in the concentrated acid....


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## gagan7741 (Dec 26, 2020)

I faced a similar issue today. i refine silver clad on copper scrap here using hot concentrated sulphuric acid that leaves the copper almost as it was and just dissolves the silver. i was taught this method by someone who didnt warn me about silver sulphate then. the sludge at the bottom is indeed silver sulphate and as everyone here knows it doesnt dissolve in water so much. i precipitated the silver from the solution using copper while leaving the white sludge in the solution only. Then after washing and drying the silver cement i went on to melt it while setting the furnace temp to 1100 c.after sometime i noticed the silver(or silver sulphate) was vigorously boiling and very strong sulphuric fumes coming from the furnace.i immediately cooled the crucible down and started googling as i was sure i had thoroughly washed the silver powder and no sulphuric acid should be remaining.now that i know that it was silver sulphate boiling at above 1085 c ,im worried about how much of my silver went up in smoke. the lot that i was refining had about 15 kg of silver, will now dissolve this silver sulphate molten mass in nitric acid and see how much i have lost.
any tips before i go on and try recovering using nitric acid ?


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## Lou (Dec 27, 2020)

If ever you melt any silver from sulfate processing, it is most wise to use borax cover and several pieces of rebar:

The iron turns silver sulfate to silver metal and iron sulfide slag is the final product.


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## conglioa (Dec 28, 2020)

The white sludge is anhydrous sulfate salts caused by the sulfation of sterling silver coins.
Dissolve it in water and heat it up to 90-100 degrees for a few hours.
All the silver sulfate will dissolve into the water into a silver sulfate solution, then you can proceed to filter to separate the insoluble precipitate.
Silver sulfate solution you can cement it with clean copper or precipitate silver in the form of silver chloride and do the next job so that it becomes cement silver easily with Lye + sugar or Zinc + HCl.
Hopefully that little bit of advice can be of help, as I'm working on restoring a huge amount of silver with hot concentrated sulfuric acid.
Wish success.


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## kadriver (Jan 10, 2021)

Silverdan said:


> I am hoping someone can help me as I think I may have screwed up bout 100 ounces of sterling silver. So when I dissolved the items in the sulfuric acid I wound up with nothing but a gray sludge I even added a lot more acid and still the same. Can someone please help me in the right direction?


I used sulfuric to dissolve silver. But the silver needs to be rolled very thin. I boiled the thin silver in 93% sulfuric acid until it dissolved completely. Then I used fiberglass filters (pricey) to filter the solution clear of solids. Then I added hydrochloric acid to the filtered solution, slowly because it spattered hot acid. Once all the silver chloride dropped I added water (yes, water to acid) very slowly until it turned a blue color. Rinsed the silver chloride real good with hot water then converted to high purity silver with lye and sugar. Didn’t use one drop of nitric acid. Here is a video that I made of the entire process: https://youtu.be/BocqoUyw1CI


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## gagan7741 (Mar 14, 2021)

https://www.youtube.com/watch?v=IeLczpPCqV8
This guy just added NaOH to silver sulphate and says that it converts to silver oxide which can then be processed with sugar to get pure silver.
I just never got the confidence to put silver obtained from sugar lye method in my melting furnace because during my early days some local 'refiner' who i had hired to help, went and ahead and blew away almost 2kgs of silver by trying to melt silver chloride .That loss i will never forget.
So we have been using pure copper strips to drop silver and produce silver powder.
But i guess there's no easy way to process silver sulphate but to use sugar/lye method.
I tried dissolving silver sulphate in water but this stuff is really tough to dissolve.


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