Washing Silver Cement

[Alentia]

I have made somewhat an experiment today and obtained very positive results.

After washing my silver cement (came from silver ore) multiple times with hot water it was not in the condition I wanted it to be: muddy dark grey mass.

I have decided to wash it with diluted H2SO4. We know that Copper Nitrate (always left in the cement, no matter how good are you wash) reacts with H2SO4 produces HNO3. Well...

1. The silver came out to be chunky and light grey color, mud has disappeared. Result is very similar when washing gold with HCl.
2. Solution became a bit greenish
3. After washing and filtering all my silver cement (about 2-3 kilos) I have decided to see if any silver got dissolved by HNO3. I dropped copper pipe into the bucket with wash solution and to my surprise no silver has cemented on copper.
4. It looks like the amount of HNO3 created was either negligible (most likely the case) or H2SO4 and HNO3 digested other more reactive "crap" first and had no strength left to eat the silver.
5. I am expecting for cement (by the way it looks) to be 99% or bit more pure.
6. Will let you know if I find any "blue" residue after drying up the cement. I would hope not, as most of it should have been converted into CuSO4, which is highly soluble in water.

 

[Alentia]

No blue residue (Copper Nitrate) observed after drying up silver cement.

 

[9kuuby9]

Wow thanks for sharing; this experiment is worth it's weight in gold :mrgreen:

I will try this in the near future and see how it works out.

 

[solar_plasma]

Nice! Thanks for sharing! Have you already melted it or testet its purity?

 

[Alentia]

Silver came out much "whiter" than usual. Normally it had a tint, but after treating it with H2SO4 it is almost clean, bright and shiny. There are black dots, here and there, but they might be simply from older melts in those crucibles used for non pure PMs and inquartation. It is looks like 99% pure. Other 20oz bars came out looking even better, by they are already in the cell being refined to 999.

 

[mikeinkaty]

It would be interesting to know what other metals might be in the bars before electrolysis. Anyway you could get someone to shoot one with a xrf gun? Mike

 

[torscot]

You mention in your opening post that you are recovering your silver from ore. I assume when you drop your silver you are using the copper bar method, and are coming up with other impurities, a lot of copper, and if I may guess some cobalt, nickel and AS. The AS gives a very dark grey colour to your bars, and makes them unsalable to a refiner. A lot of "crap" seems to drop when I used the copper. I too have been recovering from silver ore. All from Northern Ontario. I have found the copper bar method rather tricky to master. I drop the silver with HCI into chloride. It's done in an instant. and is almost foolproof. Those ores don't have a lot of natural copper in them. Rinse the chloride several times with hot water, convert to silver metal with Lye and corn syrup. and melt into bars. I have had this assayed. 96.6% silver, 0%AS, it stays in solution. Good enough for the refiner. I have treated the chloride with ammonium hydroxide to remove even more impurities. this assayed at 99.3%. I am just setting up my own electrolysis system now using the stainless bowl system shown on this site. It's so simple I have to try. You may want to give the chloride method a try. When you are recovering with nitric, are you getting a green substance floating in your acid as it works? It's silver/ copper chloride created just from the natural chlorides in the rock, I you don't capture this you're losing a huge amount of silver. Dropping with the copper bar you now have silver chloride mixed with your silver meta in your cement, or if you have filtered you now have silver trapped in your filter. At least I had. that's a nasty mixture to convert into bars. You are the first person I have seen on the site recovering from ore. I have been working on a method using the formulas shown on this forum for a year and tweeking them for this job, and can now say it works. I've lurked around this site for quite some time reading, reading, reading and learning. Without it I would never have recovered any silver. This is my first post.

 

[butcher]

torscot,

I am impressed with your first post.

 

[Alentia]

Torscot,

What I have learned during the process is to treat ore with H2SO4. First time around I had treated it in the middle of the process, using iron already existed in the ore to convert any silver chlorides back to silver and then re-digest with HNO3. Effectively any nitrate salts are converted back to nitric acid.

I understood that treating ore with H2SO4 at the beginning and in the middle stage might be even better, but I have to give it some thought, as I want some iron still be present to get rid of the chlorides. My mistake was to actually use copper to cement, I should have used iron. As you correctly pointed, there is not much copper if any present in the ore itself. Washing cement with H2SO4 took care of almost any "crap" in the cement.

I did not get any "green" salts and am 99% sure I have recovered all the silver there left, as last attempt did not get anything dissolved. I had ran some other experiments with the ore to see if any valuables are left. None so far.

The ore came from Northern Ontario and has lots of Nickel and Cobalt in it besides silver.

 

[torscot]

Thank you for welcoming me to the forum Butcher. I have been doing a lot of reading and learning here, and finally I have found a topic that I have some experience with.

Alentia, I never thought of using that acid in the recovery process , except to remove the last bits of flux from my bars to clean them up. You are trying your best to get rid of the chlorides, and I am doing my best to turn it to chloride. but, we both get the same outcome. Silver bars, Cool. I have made some notes in my book of formulas and will play with it when I have some time, I'll try almost anything once. One other little trick I use with this ore is to crush as fine as possible, If it doesn't go though a window screen it's too big, then gravity concentrate, this takes out a lot of the calcite. then pour in hydrochloric acid to the crushed rock and heat till there's no more reaction. All the calcite that destroys your nitric is gone, I use it on the bigger pieces too just to remove the calcite. Wash and rinse really, really good, use an ammonia based cleaner in your rinse water because you might get a chloride coating on your silver, the ammonia will look after that. The particle size is so small the acid will bite its way through the thin coating of chloride that has formed that the ammonia didn't remove, and the particle is dissolved. You get a really fast recovery with the nitric because of the small size .

I have collected minerals in the historic silver camps of Northern Ontario for years, and am more interested in silver mineral specimens than the metal. But, I had so many poor quality specimens that I had to try to recover the silver from it, just so I can say I did it. Profit, not in the equation for me. If other members of the forum read this and are interested in seeing some fine specimens of native Ontario silver just ask and I'll post them in the photo section.

 

[Westerlund]

Hello All,

I would like to ask a question.

I have plenty of experience with refining silver, but now I want to refine fine silver with rests of vitreous lead-bearing enamel on it. I manually removed as much of the enamel as I could and heated, almost to melting point, the silver with salt and cream of tartar on top of it. Still, there is some enamel left. Aside from lead, it is possible that the enamel contains cadmium or arsenic or antimony.

I proceeded as usual, dissolving the silver in nitric acid. The solution turned dark grey, even blackish. This never happened before. I precipitated with copper. The solution turned blue, the silver came down as expected. I then filtered to get as much of the nitrate out as possible and then I made a solution of distilled water and sulphuric acid. This solution was very weak, I guess 8 – 10%. The silver cement looks exactly as it should now. But I am not completely sure. I made some mistakes before. Actually one: not washing well enough and then I find that it becomes practically impossible to melt the cement. This was a very bad experience. I use a propane-oxygen torch and a silica crucible.

Should I proceed with the melt?
Should I add a pinch of sugar to the borax, as I read in one of the posts?

Thank you for reading,

Dordi Westerlund

 

[James Ball]

There’s nothing new under the sun when it comes to silver refining. I saw on YouTube, where a guy, I forgot his name, boiled his cement silver with dilute sulfuric acid. So I tried it. I washed my cement silver until it was colorless. Then I added dilute sulfuric acid (10%) and the solution turned blue. I boiled it and washed out the sulfuric acid (kept the first wash to check for dissolved silver (Ag₂SO₄). Rinsed it with dilute sodium bicarbonate until it stopped fizzing, rinse it again to get rid of the sodium bicarbonate. I melted the cement silver into silver shot and it was a really fine looking silver. I’ve put this into my silver cell, I am almost through with his batch, and I see absolutely no blue color in my electrolyte . I’m trying this again with a new batch of silver that I got from digesting junk sterling silver. Same thing so far I got a deep blue solution after the washing/boiling the cement silver with sulfuric acid. Below is a photo of the solution in sulfuric acid after it’s been washed with distilled water. I’m going to add this sulfuric acid wash/boil to my procedure from now on. I think I can make my electrolyte last longer using this procedure. Takes a lot more distilled water, however.

 

[Yggdrasil]

There’s nothing new under the sun when it comes to silver refining. I saw on YouTube, where a guy, I forgot his name, boiled his cement silver with dilute sulfuric acid. So I tried it. I washed my cement sober until it was colorless. Then I added dilute sulfuric acid (10%) and it turned blue. I boiled it and washed out the sulfuric acid. Rinsed it with dilute sodium bicarbonate until it stopped fizzing rinse it again to get rid of the sodium bicarbonate. I melted the cement silver into silver shot and it was a really fine looking silver. I’ve put this into my silver cell, I am almost through with his batch, and I see absolutely no blue color in my electrolyte . I’m trying this again with a new batch of silver that I got from digesting sterling silver drunk sterling silver. Same thing so far I got a deep blue solution after the washing the cement silver I will try to post a photo of the solution in sulfuric acid after it’s been washed With distilled water. I’m going to add this Sophia acid wash to my procedure from now on. I think I can make my electrolyte last longer using this procedure.

You need to have some Copper in your electrolyte to achieve dense good crystals.

 

[James Ball]

I am getting quite abit of crystals with a 2.3-2.4 amps at 3.5 v. Does the lack of copper affect the purity of the silver crystals? How much copper does this cell need?

On a side note. I was worried that the sulfuric acid wash would lower my silver yield because of silver sulfate formation. I kept the sulfuric acid wash (~1.1 L) and added 50 ml conc HCl. To my relief there was not a hint of a white precipiate. Just to be sure I could recover any silver in this solution I added a drop of my silver nitrate electroyte solution and got the typical silver chloride white flocculant precipitate. It does not look like 10% sulfuric acid has any affect on silver.

This brings up a new question. Is the silver from this procedure as pure as the silver from the silver cell? I am seeing some gray slime in my silver cell basket so I think the answer would be no. It would be fun to do some ICP-MS of both samples.

 

[FrugalRefiner]

I am getting quite abit of crystals with a 2.3-2.4 amps at 3.5 v. Does the lack of copper affect the purity of the silver crystals? How much copper does this cell need?

The copper doesn't affect the purity (unless it gets too high) so much as it affects the form. If there is no copper in the electrolyte, the crystals tend to grow long and thin, so they can grow quickly toward the cathode and short in out. With some copper in the solution, the crystals will grow a little fatter, and not get as long as quickly. The copper also helps to keep any lead in the slimes instead of going into solution.

Now, if the copper level gets too high, it will start to co-deposit on the cathode along with the silver, and that will definitelyu lower the purity of the silver crystals.

This brings up a new question. Is the silver from this procedure as pure as the silver from the silver cell? I am seeing some gray slime in my silver cell basket so I think the answer would be no. It would be fun to do some ICP-MS of both samples.

Go for it! And please let us know. Most of us don't have access to ICP-MS.

Dave