# Black powder in AR



## Dlaw46112 (Nov 6, 2016)

Hello, first post for me. I have been reading a lot and have started refining some scrap gold alloy we use in our Mfg. The alloy is 71% Au, 4.5% Ag, 8.5% Pt and the balance is Copper. I have dissolved about 238 Gms of this alloy in AR and I have a very fine black powder in this solution. It does not filter out in a coffee filter. The silver chloride was retained however. The alloy specification has a trace amount of Iridium and Palladium ( each less than .005%). I do not want to proceed further without some advice?


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## 4metals (Nov 6, 2016)

I would bet the fine powder is iridium. Iridium does not dissolve into aqua regia so it likely remained mixed with your silver chlorides. Why it would be fine enough to pass through a filter that retained the silver chloride may have to do with it's low concentration in the alloy. 

Was the starting material a solid metal alloy or a sintered metal?


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## nickvc (Nov 6, 2016)

Welcome to the forum.
My guess is iridium as it is very difficult to dissolve unless prolonged heating is applied, please be aware PGM salts, ie dissolved platinum group metals, are highly toxic so take the necessary safety precautions when dissolving and handling. The palladium will be in solution as will the copper and gold, the silver you now have in chloride form, I'd suggest some strong heating to dissolve the iridium and then precipitate the gold followed by cementation with copper to remove the PGMs, these I would save and send to a specialised refiner such as Lou to refine the values.


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## Dlaw46112 (Nov 6, 2016)

Thanks much for the quick replies! I started with solid alloy ( sheets .017 in thick with holes cut out with wire EDM). I did not heat the AR while dissolving but did it under a hood and I have a hot plate that I can heat the solution. I was curious if it was the trace iridium but the initial alloy stated it was less than .001 percent!
I will try the heating technique and report back.


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## FrugalRefiner (Nov 6, 2016)

Since you didn't heat it, some of the black may be platinum. Some of it may have dissolved along with the silver, but some may still remain since there was more Pt than Ag.

Dave


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## anachronism (Nov 6, 2016)

There is another option.

Process all of it WITHOUT heating it. 

Then if the Pt is the powder as mentioned by Dave you have most of it in one place and it can be processed separately.


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## Dlaw46112 (Nov 6, 2016)

Thanks again. I think I will split the solution and heat a portion to see f the powder dissolves. If it does, it is probably Pt. If not, then possibly the Iridium. Hoke mentions the Iridium will remain as residue but I was surprised I was not able to filter it with the silver chloride. Let you know in a couple days.
Thanks for all the wealth of knowledge. I have been reading the forum for a year and appreciate all the expert advise, particularly on safety.
Dave


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## autumnwillow (Nov 9, 2016)

I do not think its iridium. I usually process lots with iridium. They only behave like silver chlorides and should filter well.

What you have is either silver chloride or Pt. If you are only doing gravity filter then it will take time to filter.

Just out of curiosity. May I ask what you manufacture? The alloy used seem strange.


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## Dlaw46112 (Nov 12, 2016)

I heated part of the solution to about 125F with no change to the solution. I added a little more Nitric as I was very stingy with it in the initial dissolve and the solution has been sitting for a couple weeks so I thought my acids were killed. I also added about 4x the nitric amount with HCL to have some fresh AR. Still no change. The powder goes right thru a coffee filter. The gravity filtration is very quick, a couple minutes. I will try to add a pic.

Do I need to heat much higher?

We manufacture high speed slip rings for aerospace/ jet engine development. The ring and brush alloy is the same gold alloy, made by Deringer NEY called NEY G alloy.

I appreciate your help!
Dave


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## autumnwillow (Nov 13, 2016)

For Pt to dissolve, yes much higher. For silver chlorides, it will not be attacked by AR.


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## Dlaw46112 (Dec 31, 2016)

Update: It appears I did not have black powder contamination. My solution was so dark green that it appeared to have powder in it. I broke it up into smaller containers and was able to see that the solution was clear. I then added the ammonium chloride and dropped out the Pt as a yellow precipitate. I then filtered, diluted with water and dropped the gold with SMB. I washed the gold per LaserSteves tutorial and melted the gold. It was very pretty after dipping in the 5% sulfuric wash. I sold it and the assay came back at 99.06% and 99.38% purity ( 2 separate batches).
I was a little disappointed at the yield though. I thought I had 228 grams of Au in the alloy and I yielded only 194 grams. I am sure some is in my filters, platinum sponge and stockpot. Is this a poor result?
Thanks again for all the help and the volume of info on this forum. It is invaluable to guys like me.

Happy New Year!
Dave


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## anachronism (Dec 31, 2016)

Dave I would struggle to see where you would lose a whole ounce of gold unless you really did mess something up badly and physically lose something. Have you retained all your solutions and papers etc? 

If you have and you can scavenge those to be sure you have everything then maybe the next step would be to xrf a sample of the alloy just to be sure that your original starting numbers were correct. 

If they are not, then you need to have words with your supplier although it's more likely to be a "not recovered" issue.

Jon


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## Dlaw46112 (Dec 31, 2016)

Thanks Jon, I appreciate the honest feedback. I was disappointed in the yield. I did save my filters and solutions. This weekend, I started salvaging my stockpot to see if that is where my missing gold ended up. I have been bubbling with copper in the pot all week. I am following the procedure I found from 4metals on the forum. My filters were yellow colored at first and I realized I was not rinsing them well enough at first. Some is probably in there. I also got cockty one time and added the SMB too quickly and had a boil over. It was contained in a pan I had under the beaker but I realize now that I made a mistake using a steel pan rather then ceramic for this purpose.
Thanks for the kind suggestion that my original alloy was not correct. I am quite certain the material was as it was stated so the loss is in my process.

Dave


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## anachronism (Jan 2, 2017)

We all make mistakes no matter how much product we have run Dave. It's being able to track those mistakes down and recover the gold that means the difference. I'm sure you'll find as much as possible especially since you've kept all your raw materials and process fluids/papers.

An ounce is one heck of a lot to find and whilst I wish you all the best, thanks for taking the advice on the chin in the spirit that it was meant. 

Jon


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## nickvc (Jan 3, 2017)

With the boil over the chances are you cemented a fair amount of gold onto your steel catch pan so use either HCl or weak nitric to dissolve the steel so you can recover your gold, as Jon said an ounce of gold is a major loss but if you still have everything you will find it.


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## Dlaw46112 (Jan 3, 2017)

Thanks guys! I will do the recovery from my steel pan as suggested. Great advice as I was wondering how to recover that.
I think I also made the mistake of not removing my excess nitric before dropping the gold. After much more reading on the site, I think that is where I lost most of the gold. I dissolved my alloy by putting all of it into a 4l beaker and then adding the AR in what I calculated to be about a fourth of what would be needed. I was very surprised at how much of the gold dissolved with my first 100 ml of nitric. Once the process stopped, I poured off the solution and began processing it. I added new AR to the beaker and kept dissolving the gold alloy. I think what I missed was not adding excess HCL to the AR. I may have run out of the hydrochloric before all the nitric was used up.
I am now processing the stock pot by cementing with copper fittings. I now see however why Harold goes straight to iron as the cementing is quite attached to the copper. Any suggestions on how to remove this would be appreciated!
I will add a gold bar to a liter of my stockpot with some fresh HCL to see if any excess nitric causes the bar to dissolve. It currently weighs 141 grams and it will be interesting to see if any mass is lost.
Thanks for the continued interest!


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## Topher_osAUrus (Jan 3, 2017)

I have read a couple ways to get the stuck cement off of copper.
One. Keep using it until its gone
Two. Let it dry and it will flake off
Three. A little HCl can sometimes help it lose its adhesion to the copper

There may be more, but those are all that come to mind


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## Dlaw46112 (Jan 4, 2017)

Thank you! I will try 2 and 3 on a couple fittings and let you know.


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