# Silver Cell Slimes - Palladium with silver in solution



## kadriver (Dec 30, 2011)

I had some silver cell slimes that I had never processed - because I did not know what to do with them.

I rinsed the slimes into a beaker and added some nitric acid - probably too much.

The beaker has been sitting in my lab for about a month or more.

Adding nitric acid probably formed more silver nitrate and possibly dissolved some palladium into palladium nitrate (I am just guessing here).

I siphoned off the clear liquid into a seperate beaker (see photo).

Then I tested with stannous chloride and got a reaction indicating platinum group metal was present (I dont think it can be gold).

I put some of the orange liquid in a spot plate and added a drop of HCl. Lots of precipitate which is probably silver chloride.

I know that there is probably very little PGM due to the color of the solution.

Also, some black powder remains in the beaker that contained the slimes, treated with nitric acid.

I am thinking there is palladium nitrate and silver nitrate in this orange solution.

The black powder left in the orignal beaker may be platinum (or maybe just dirt).

I would like to know how to seperate the silver from the solution. I don't know what to do next. I'll read some more and see if I can find a way described in Hoke.

Any help would be appreciated.

Thanks - kadriver


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## kadriver (Dec 30, 2011)

here is what is left in the beaker after it was treated with nitric acid - looks like black powder - or it could just be dirt. I'll get some out, wash it and dissolve it with with few drops of AR in the spot plate and then test for platinum.


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## kadriver (Dec 30, 2011)

The sample on the right in the spot plate is of the orange solution tested with stannous chloride. The sample on the left is orange liquid tested with HCl.


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## kadriver (Dec 30, 2011)

I put a few drops into a test tube and added some DMG - it clouded up just a little.

I am inexperinced with use DMG so I could not tell if the DMG test was positive or not.


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## nickvc (Dec 30, 2011)

Kevin if your original source of silver included modern jewellery it's possible you have Rhodium in the mix it's become very popular to give silver that white gold or platinum look. I'm afraid I'm a complete dork when it comes to PGMs but thankfully we have several members who are experts, Lou and Steve leap to mind, if your looking to refine them, personally I'd just recover, melt,assay and sell as mixed PGMs but as you know I have access to cheap assays.


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## Harold_V (Dec 30, 2011)

I processed my slimes by dissolving with dilute (distilled water) nitric, then when everything that would dissolve had done so, I separated the solution from the solids, which should be gold and platinum. Rinse well, and add the settled rinse water to the golden solution. When you've finished the rinse, add HCl to the solution, which will precipitate the silver as silver chloride. Rinse the silver chloride well, returning the rinse water to the main solution. You can then either send the solution to the stock pot, or it can be evaporated for recovery of the palladium with ammonium chloride and sodium chlorate. You may also wish to cement the values using zinc. By doing so, you can avoid the evaporation process. 

Convert the silver chloride to elemental silver by one of the metallic processes (use scrap iron or aluminum). That way you'll also recover traces of palladium what won't have been recovered by rinsing. It will report in the slimes when you part the resulting silver. Do keep the palladium at a low level, otherwise you have issues in the silver cell. 

You can now dissolve the remaining solids (gold and platinum) using AR, then process as you normally would to recover the gold, then the platinum. I tend to recover gold first, because it's much easier to wash than platinum that is recovered with ammonium chloride. 

Harold


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## kadriver (Dec 30, 2011)

Harold:

Thank you.

Here is my plan for this small amount:

1) rinse left over solids with distilled water, allow to settle, then add rinse to main solution, save the solids as gold & platinum to process later.

2) add HCl to main solution to precipitate silver chloride.

3) allow the silver chloride to settle and pour off the main solution.

4) rinse the AgCl with more water and add rinse back to main solution.

5) add solution to stock pot or process with ammonium chloride and sodium chlorate - or cement with zinc.

6) process the silver chloride using a metalic method in order to recover traces of palladium (I only know NaOH & sugar, the others are a mystery to me - I'll search the forum for more infor here.) I have some powdered aluminum.

7) process the black powders in AR - gold first, then Pt.

Now I have a good sense of direction with this little batch.

Thank you! - kadriver


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## kadriver (Dec 31, 2011)

nickvc:

whne the time comes, I would like to be able to seperate the two metals (platinum & palladium). I have Steve's DVD and I think I can accomplish this.

When it comes to melting, I may just send in the sponge instead.

On the other hand, I would like to hold a button of pure platinum in my hand.

Thanks - Kevin (kadriver)


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## Harold_V (Dec 31, 2011)

kadriver said:


> 6) process the silver chloride using a metalic method in order to recover traces of palladium (I only know NaOH & sugar, the others are a mystery to me - I'll search the forum for more infor here.) I have some powdered aluminum.


It's a simple process, and I'd likely advise the use of scrap steel in lieu of using aluminum (in spite of the fact I used to use aluminum. It's impossible to filter the resulting solution). 

I believe lazersteve has reported on the scrap steel process. 

Harold


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## lazersteve (Dec 31, 2011)

Using scrap steel is a very straight forward route to converting silver chloride.

Check out the converting silver chloride videos in the Silver Section on my website for details.

Steve


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## kadriver (Dec 31, 2011)

I'll check there Steve - thanks.


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## kadriver (Jan 1, 2012)

Amazing video - I had no idea that this method was available.

I have been collecting old computers - my shop is now full of them. I have many old aluminum heat sincs from the CPUs.

Could I use the aluminum heat sinks instead of the pieces of iron?

I have a 3 liter jar about 1/4 full of clean silver chloride.

Thanks - kadriver


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## kadriver (Jan 1, 2012)

Harold, I missed your reference to filtering problems when using aluminum to convert silver chloride. I'll stick to iron for now and maybe experiment with some aluminum later.

Thank you - kadriver


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## meng2k7 (Jan 1, 2012)

kadriver said:


> Harold, I missed your reference to filtering problems when using aluminum to convert silver chloride. I'll stick to iron for now and maybe experiment with some aluminum later.
> 
> Thank you - kadriver




hi kadriver,

please be informed that some of aluminum heatsinks are anodized,anodized aluminum won't attacked by sulfuric acid because of protective layer from the surface of the metal.

if it is anodized, Lye or HCL will dissolve that protective film, rinse it.

its just my two cents. 

thank you.

meng


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## kadriver (Jan 2, 2012)

Thanks for pointing that out. If i decide to use these pieces of aluminum, then I will make sure to get that protective layer off first.

Thanks! - kadriver


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## kadriver (Jan 23, 2012)

I have more silver cell anode slimes to work with. This is from the last anode baskets. I had about 200 troy ounces of silver that left behind the solids in this photo.

This material includes the batch of silver cell electrolyte that became contaminated with palladium a while back - so there should be some of that plus gold and platinum.

I tested this in a spot plate - positive for silver (of course) and PGMs.


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## kadriver (Jan 23, 2012)

Here is a photo of the solids after being seperated from the settled solution. I washed and settled, removing the liquid with a pipette.

The last wash contained no more silver - a test with HCl remained clear.


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## kadriver (Jan 23, 2012)

I filtered the solution (this is the cell slimes treated with dilute nitric acid - the resulting solution). It was crystal clear ready for the HCl.

Then I added hydrochloric acid, to precipitate silver chloride from the silver that was in the solution.


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## kadriver (Jan 23, 2012)

I store it inside a cabinet with doors shut to keep the light off of the silver chloride while it settles.

When it settles completely, I will siphon off the palladium solution and rinse the silver chloride free of color - adding the rinse water to the yellow solution.

Then I will evaporate some of the liquid by slowly heating it to reduce the volume and add to the PGM stock pot for later recovery.

I have one question maybe someone can answer - Am I losing any values by heating the solution to evaporate off some of the liquid? I do the evap with very low heat - never boiling.

Thank you - kadriver


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## kadriver (Jan 23, 2012)

Harold_V said:


> You may also wish to cement the values using zinc. By doing so, you can avoid the evaporation process.
> 
> Harold



Once the silver chloride has been removed, then I can precipitate the mixed PGMs from the remaining golden solution with zinc?

This seems like the way to go as I already have mixed black powder already.

If I can used powdered zinc to precipitate PGMs from the golden solution, then that would allow me to proceed immediately. 

Also, Steve has refered me to a post by Lou that describes a stream-lined way to seperate the metals:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=8742&p=82338#p82338

This is all starting to come together for me now. I am having a ton of fun here. Thanks for all your help!

kadriver edit spelling


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## Harold_V (Jan 23, 2012)

kadriver said:


> Harold_V said:
> 
> 
> > You may also wish to cement the values using zinc. By doing so, you can avoid the evaporation process.
> ...


Correct. If you have an excess of acid present, it will dissolve some of your zinc, but you'll recover the values eventually. Just keep adding small amounts of zinc until the solution tests barren. 

Harold


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## kadriver (Jan 23, 2012)

Perfect - today I'll rinse the silver chloride, allow to settle, and return the rinse to the main solution, then precipitate the PGMs with zinc powder.

I am anxious to dissolve the solids in AR - maybe I can get some gold (probably not much) from the dissolved solids.

I am ready to do both processes today.

Thanks for your help - kadriver


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## kadriver (Jan 23, 2012)

To conserve my zinc, can I add some sodium carbonate to the solution (say a couple of spoon fulls) to get rid of some of the acid before I precipitate with zinc powder?

I did this with HCl/Cl leach solutions and it worked fine.

kadriver


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## kadriver (Jan 24, 2012)

here is a shot of the settled silver chloride - I poured off the clear golden liquid (containing palladium) and added some water to the silver chloride to rinse.

Note that there is some tiny crumbs of silver chloride in the bottom of the 4 liter beaker. It came over (stuck to the side of the beaker) when I poured it off.

Can I go ahead and precipitate with zinc with this tiny amount of silver chloride present? Or should I take the time to make sure that it all gets removed before I precipitate the palladium with zinc? (no brainer - of course I should).

I was thinking that I could add some ammonium hydroxide to the black powder after I precipitated it to dissolve the little bit of silver chloride - but this creates extra steps - not necessary if I just get it out now while it is easy to remove.

When the silver chloride settles (tomorrow) I will pour the clear liqiud off and add it to the main golden solution in the 4 liter beaker.

kadriver


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## nickvc (Jan 24, 2012)

Kevin I'm glad you answered your own question about removing the silver chloride, you knew that by leaving it in the solution it was going to cause you problems at the final stage, especially as knowing you, you will want a high purity final product.
In most of the steps of refining we aim to remove all but the value we are actually after that's why we remove base metals from karat scrap before precipitating gold and for high purity a second refining of the powder is often needed, shortcuts can be used but only when you know how to solve any the problems they can and frequently do produce.


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## Harold_V (Jan 24, 2012)

Any silver chloride that remained in the solution would be converted to elemental silver with the added zinc. That's one of the methods of reducing silver chloride. If your objective is purity, I'd suggest it be removed. 

Harold


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## kadriver (Jan 24, 2012)

Harold_V said:


> Any silver chloride that remained in the solution would be converted to elemental silver with the added zinc. That's one of the methods of reducing silver chloride. If your objective is purity, I'd suggest it be removed.
> 
> Harold



Yes - I overlooked the fact that the silver chloride would turn to silver metal (iron would do the same thing as per lazersteve's website video).

So my plan to remove the silver chloride after precipitating the PGMs was a wrong approach anyway from that angle as well.

It will be easy to get it out. I will siphon off the clear golden liquid, leaving as little liquid as possible with the crumbs of silver chloride. Then add that to the silver chloride container for additional washing.

Thank you - kadriver


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## kadriver (Jan 24, 2012)

The solution was drawn off with a large pipette, leaving the crumbs of silver chloride behind.

I should have used the pipette in the first place. Pouring the solution caused the silver chloride to carry over, drawing with the pipette would have prevented this carry over.

I used a small pipette to get nearly all the solution, adding the bits of silver chloride to the settling jar.


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## kadriver (Jan 24, 2012)

And now for the fun part - precipitating the mixed PGMs with zinc powder.

I bought the zinc powder from this Ebay seller:

http://www.ebay.com/itm/Zinc-Metal-Powder-2Lb-3000-Mesh-LOWEST-PRICE-EBAY-/120793602791?pt=LH_DefaultDomain_0&hash=item1c1fdc1ae7

He assured me that it is pure zinc with no additives (like anti-caking cabosil)

It is very caked and clumped together, but powders fine with a mortar & pestle.

It reacts very fast and the PGMs drop out right quick.

I have some more black powder from an HCl/Cl leach - I have two processes going at one time.

I have more solutions being prepared for precipitation - once they are all precipitated I will begin the process of seperating the metals starting with a bath of the black PGM powder in sodium hydroxide 20% solution (20 grams NaOH red devil lye dissolved in 100 ml water at room temperature).

Hopefully, the NaOH bath will remove any zinc that carried over from the precipitation.

Thanks for looking. Of course criticizm and comments are alway wecome!

kadriver


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## kadriver (Jan 25, 2012)

Here is a short video of the palladium precipitation using zinc powder - looks like a tornado in a jar!

[youtube]http://www.youtube.com/watch?v=FG2dn_pRMQk&context=C3c0f440ADOEgsToPDskJ_kOtcwYJqoLQIwh7dJxxs[/youtube]

kadriver


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## kadriver (Jan 25, 2012)

I almost forgot - I still have some material from the silver cell slimes that has been treated with nitric acid only - it needs to be dissolved and PGMs precipitated.

The earlier nitric treatment removed most of the palladium (that is what was precipitated above in this post).

The rest of the material from the silver cell slimes should now be gold and platinum (maybe a little rhodium).

I will digest this tomorrow. I am going to use HCl/Cl instead of aqua regia so I won't have to de-noxx (evaporate to remove nitric acid).

Does anyone see a problem with using HCl/Cl instead of AR?

Any advantage to using AR here?

Is there an advantage to using Hcl/H2O2 instead?

I have some 12% H2O2.

Input from the forum would be welcomed - please, this is all new to me.

kadriver


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## kadriver (Jan 25, 2012)

Today I was able to process the solids from the silver cell slimes. The palladium and silver (most of it) was removed with dilute ntric acid treatment.

I added about 100 ml hydrochloric acid (some silver chloride did form). Then placed the mixture on the heat.

I then carefully added nitric acid a little at a time - only took about 4 or 5 ml of nitric to dissolve all the solids.


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## kadriver (Jan 25, 2012)

Spot plate tests:

top photo is three seperate dissolutions tested with stannous chloride:

Top left: gold waste cemented on copper - dissolved in AR.

Top Middle: More gold wastes cemented on copper - dissolved in AR.

Top right: Silver cell slimes solid material dissolved in AR

Bottom row, same dissolutions but tested with ferrous sulfate crystals.


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## kadriver (Jan 25, 2012)

Notice the bottom left cavity. The ferrous sulfate crystal produced a brown cloud, but then it dissapeared after about 5 minutes.

The solutions have not been evaporated to remove excess nitric yet. The AR left from the reaction probably re-dissolved the brown cloud from the ferrous sulfate test.


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## kadriver (Jan 25, 2012)

The center solution was green so I tested for iron with ammonium thiocyanate and potassium thiocyanate. Neither one gave a blood red color.


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## kadriver (Jan 28, 2012)

The three solutions settled over night. Then evaporated down to syrup for denoxx.

The rehydrated and settled solutions were tested with SnCl and a ferrous sulfate crystal


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## kadriver (Jan 28, 2012)

I excluded the green solution to do by itself.

The two amber colored solutions were combined into one beaker.

The combined solutions were filtered using a whatman number 5 filter.

The filtered solution was put in a larger beaker for precipitation.


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## kadriver (Jan 28, 2012)

I added a crystal of ferrous sulfate to test for gold.

Got a very weak reaction - very little gold in this solution.

I am stuck right here.

I know there is a trace of gold in there, and I want to get it out (maybe not for the value, but for the purity of the PGMs).

I do not know how to proceed from here.

Can I add some SMB to get the gold to precipitate and remove it through a filter?

Any input would be very welcome.

Thank you - kadriver


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## Geo (Jan 29, 2012)

SO2 would selectively precipitate the gold. you can make a diluted SMB solution and add, wait 24 hours and any gold should settle out in that time. if you expect trace amounts add less than a half gram of SMB to reduce salts in the solution (not sure it would be an issue anyway).


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## kadriver (Jan 29, 2012)

I don't have SO2 gas (yet). Airgas says they can get it, but they want a rental fee of $.50 per day for the tank.

I don't want to fool around with making my own, even though I probably could.

I have already considered adding some Sodium MetaBisulfite to the Platinum Group Metal solution. My question is this;

Hoke makes no mention of SMB, will the PGMs tend to precipitate with SMB, or will SMB selectively and exclusively drop the gold only?

I am concerned (by lack of experience) that adding SMB to the PGM solution will be an irreversible mistake.

kadriver


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## Geo (Jan 29, 2012)

ferrous sulfate should precipitate the gold only. if any PT or PD reports with the gold it will be due to drag down and will only be in trace amounts.the gold will be contaminated with iron but i don't think that would be an issue for this purpose.


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## lazersteve (Jan 29, 2012)

Here's a chart I made and posted in the past:

Precipitants Chart

Steve


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## Geo (Jan 29, 2012)

hey, ferrous sulfate. i got one right. :lol: 

naw, i remember reading that in Hokes, the chapter pertaining to PGM's i think.


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## kadriver (Jan 29, 2012)

Looking at the chart I would say oxalic acid would be the best chemical to use to get the gold out while leaving everything else behind.

I'll order some today - thank you Steve

kadriver


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## kadriver (Jan 29, 2012)

I did order some oxalic acid this evening so I will have it onhand.

I am going to use Geo's recommendation and add about half a gram of copperas (ferrous sulfate) to the solution to get the gold to drop out of this soution.

Funny - gold is undesirable here. Of course I will get the tiny amount of gold and trap it in a filter paper for recovery later.

Once the gold is out, I can precipitate the PGM solution and get the black powder (that I so desperately desire) and add it to my growing black powder wash bottle.

Once this solution is precipitated, I will be ready to start seperating the metals from the mixed black powder.

kadriver


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## Geo (Jan 29, 2012)

Oxalic acid is sold in most supermarkets sold as rust remover like CLR (not sure if thats the same formula) also deck cleaner or wood bleach. check labels but i have found it at places like Dollar Tree before.


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## kadriver (Jan 29, 2012)

They sell it at the grocery store where I shop CLR (Calcium, Lime, Rust).

Is this product suitable for refining?

Very helpful information here - Thanks Geo.

kadriver


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## qst42know (Jan 29, 2012)

Do you have an Ace hardware near you kadriver?

They sell oxalic as wood bleach. Ace was the only place local I could find it around here.

From Steve's chart the copperas isn't any more selective than SMB.


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## kadriver (Jan 29, 2012)

Yes - wood bleach huh? Acehardware is right up the street from me. I'll check with them tomorrow

Thank you - kadriver


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## qst42know (Jan 29, 2012)

It says Oxalic acid right on the tub. Don't forget the MSDS while you're there.


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## kadriver (Jan 30, 2012)

I added a gram of ferrous sulfate to get the gold out of the solution.

It will settle over night and then I'll draw off the solution and add zinc powder to precipitate PGMs.

kadriver


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## kadriver (Jan 30, 2012)

I finally got a little metal from my silver slimes - the gold precipitated out nicely using ferrous sulfate - thanks Geo for that recommendation.

I drew off the golden solution and got the gold trapped in a filter paper.

Then I torn the paper up, placed it in a small melt dish, added a generous amount of borax, and melted a tiny bead of gold.

This is the first bit of metal from silver slimes for me - ever!

I was very pleased and felt lifted up from this insignificant success.

kadriver


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## kadriver (Jan 30, 2012)

But then I went back to work on the platinum & palladium.

I had some solution that was still testing positive, so I added more zinc powder and got a nice fluffy black powder precipitate.

I allowed it to settle, but after settling, the black powder shrunk to almost nothing!

So I added more zinc powder. Again, nice recoverable amount to add to my collection.

I raced to draw off the liquid before the black powder dissolved again.

It was me against the beaker. The solution in the beaker was reclaiming the black powder faster than I could get the liquid out.

There was only about half left when I reached the bottom.

I could see bubbles, so I added some water to dilute and hopefully stop the dissolution.

Finally, I added a pinch of sodium carbonate to get the acid to stop eating the black powder. Big mistake.

I got this curd like precipitate now mixed in with the black powder I was trying to get.

This stuff is very slippery - seems like it will dissapear on you in a heart beat.

I can see why folks could get frustrated and give up!

Tomorrow is another day - I am more determined to get some platinum.

kadriver


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## kadriver (Jan 30, 2012)

By the way, I tested the solution before retrieveing the gold precipitate.

I placed two drops in two cavities on the spot plate.

To one I added stannouos chloride - nice dark instant reaction.

To the other, a crystal of ferrous sulfate - absolutely no reaction after 5 minutes.

This test allowed me to conclude that all the gold had been removed by the gram of ferrous sulfate added earlier.

kadriver


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## Geo (Jan 31, 2012)

no problem, glad i could help. actually that came from Hokes book but i cant remember exactly where in there i read it. funny how things pop out at you sometimes when your not thinking about it.


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## philddreamer (Jan 31, 2012)

Oxilic in wood bleach...
I've been having trouble keeping Pd from been dragged down with the gold when using SMB to precipitate from the ram chips AR solution.
I'll look for some @ Ace.

Thanks!

Phil


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## kadriver (Jan 31, 2012)

I got some wood bleach at Ace Hardware. It says oxalic acid right on the container. I also ordered some lab grade off ebay. I think it was $12 for 500 grams.

I was reading in Hoke and she says both solutions must be hot, or else it could take days for the gold to drop.

kadriver


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## kadriver (Feb 1, 2012)

This is a shot of the mixed PGMs recoverd from my silver cell slimes.

I now have all the PGMs (for now) cemented out and I am ready to start seperating the mixed metals from the black powder.

I am not familiar with any process as this will be my first attemp to seperate the black powder.

It has been suggested that I start by giving the black powder a bath in 20% (20 grams NaOH in 100ml water) sodium hydroxide solution to dissolve any zinc that made it into my collection jar of black powder.

How long should I allow the black powder to react with the NaOH? 

It was also suggested that the NaOH bath be at room temp. Is this right or should I add some heat?

Any guidance would be greatly appreciated.

kadriver


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## Geo (Feb 1, 2012)

if im not mistaken, hcl will digest zinc. nitric should dissolve the palladium at room temps leaving PT which if i understand right needs to be boiled in AR.
.


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## kadriver (Feb 2, 2012)

Geo:

Won't the HCl digest the palladium also?

If yes, then I would have to cement it out once again - a task I would not be looking forward to doing.

The only acid I had in the beaker when I was cementing the black powder was dilute HCl.

After cementing it with zinc powder, the dilute HCl would re-digest the palladium faster than I could get the precipitated black powder out of the beaker.

Maybe the black powder was not palladium? This is all new to me.

kadriver


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## Geo (Feb 2, 2012)

then one of the more experienced guys should advise you on this one because as far as i knew, palladium doesn't dissolve in straight hcl. nitric on the other hand dissolves it at room temperature. a quick web search and the only GOOD references i can find come from lazersteve here on GRF, he says hcl can dissolve PD but it needs a strong oxidizer like hcl/cl and at that its very slow to dissolve. the most other common consensus on wiki-answers and such is hcl will not dissolve palladium.


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## lazersteve (Feb 2, 2012)

Finely divided Pd will go into HCl to some degree. Hoke mentions this if I'm not mistaken and I have seen it with zinc cemented Pd black experimentally.

Metallic fused Pd will not dissolve in HCl normally.

Steve


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## core (Aug 16, 2013)

HEY GUYS,

The Oxyllic acid at the grocery store is called "BarKeeper's Friend". 

CLR contains:Water, Lactic Acid, Gluconic Acid, Lauramide Oxide, 1-butoxy-2-propanol.

Looks like danger to me! Wiley Coyote


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## Harold_V (Aug 17, 2013)

lazersteve said:


> Finely divided Pd will go into HCl to some degree. Hoke mentions this if I'm not mistaken and I have seen it with zinc cemented Pd black experimentally.
> 
> Metallic fused Pd will not dissolve in HCl normally.
> 
> Steve


If memory serves, HCl will dissolve palladium oxide.

Harold


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## Lou (Aug 18, 2013)

Not so much... HBr is a far better solvent.


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