# Dental scrap.



## Aristo (Aug 19, 2007)

Hello...

I am looking for some guidance with regards to recovery of gold , platinum , palladium and silver from dental scrap. I have done extensive work with electronic scrap ( gold only ) , however , this is new ground for me. I want to be as careful as possible.

I have digested 100 grams of dental scrap in AR and the solution is currently a deep dark red. There is a whitish powder that has settled at the bottom . Stannous chloride is showing a very dark red , then black.

I would appreciate any help so as to correctly move forward on this.

Thank you.


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## Noxx (Aug 19, 2007)

I suppose that the withe powder at the bottom is Silver Chloride.


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## lazersteve (Aug 19, 2007)

First neutralize any excess nitric acid. Then test the liquid with DMG for Palladium. You can also test a small sample for Platinum with a dash of ammonium chloride. If addition of ammonum chloride forms an orange powder you have Platinum.

Harold can give you specific instructions on this type of scrap.

Steve


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## Aristo (Aug 19, 2007)

Thanks for the info so far.

Steve , 
I am planning on using butyl diglyme....so i wouldnt be needing to neutralize the excess nitric. 
After I pull up the gold chloride , I plan to hunt for the platinum etc. I have SMB , Ammonium chloride and...well thats all.
I am used to seeing green solutions , this red thingie is scaring me.
Also...the teeth are kinda scary. :twisted: 




Also...I didnt heat the Ar , would this mean that the platinum is still undissolved or is it in solution?. I understand only boiling AR dissolves platinum.


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## lazersteve (Aug 19, 2007)

Be sure you dilute and filter your mother liquor before using the BDG. The red color sounds a lot like the Palladium solution in my latest video, it's a deep red color. Platinum can co-dissolve with silver in nitric only reactions.

Steve


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## Harold_V (Aug 20, 2007)

Aristo said:


> I am used to seeing green solutions , this red thingie is scaring me.



Don't be scared----by happy. The green solutions are an indicator of everything you don't want, and nothing you do, with rare exception. 

The red solution you speak of is red because of its contents. You'll come to understand that even gold chloride assumes a deep red color when it's heavily concentrated (evaporated well). 

In this case, it's likely you're seeing a combination of gold (predominant metal), platinum and palladium. As Steve alluded, palladium can yield a very red solution all by itself, although it is generally a darker color, leaning towards brown. I've seen it as bright as mercurochrome, however. 



> Also...the teeth are kinda scary. :twisted:



I never allowed such things to get anywhere near the process. They break out easily with a hammer on a hard surface, which should be a part of the starting process. The less you include in your solutions, the less you'll lose to dragout. 

While you haven't alluded to doing so, let me give you a bit of advice here. Do not run any dental amalgam with any of the other dental alloys. The tin in the amalgam will complicate all of your filtering from the moment you dissolve them. If you get involved with amalgam, keep it separate at all times. 

If you dissolved your dental gold directly in AR, you dodged a bullet. Depending on the percentage of silver contained, it can become impossible to dissolve, complicating the entire operation. Paige, one of our readers, recently experienced that very thing. I'm sure he could enlighten you as to the value of inquartation. I strongly recommend that you, in the future, inquart such materials. 

As Steve suggested, when you do, some of the platinum, and a good majority of the palladium, will follow the silver when it's dissolved, so you must be able to part silver in order to recover them. That is a minor issue if you intend to get serious about refining precious metals. It goes with the territory. 

I have no advice to offer if you're using anything but the system suggested in Hoke's book. That is where my experience lies------I'm an "old school" refiner. I evaporated solutions, and selectively precipitated my values from filtered solutions. I have no experience with butyl diglyme, and I have serious doubts that I'd be interested in trying it. I see no need to add steps to an already functioning system of extraction, especially when it involves more equipment and supplies. 



> Also...I didnt heat the Ar , would this mean that the platinum is still undissolved or is it in solution?. I understand only boiling AR dissolves platinum.



While it's true that platinum is difficult to dissolve, that changes when it's finely divided. It's unlikely the platinum did not dissolve----but if you see signs of black particles in with the white precipitate (likely silver chloride) you mentioned, that is probably undissolved platinum. I always dissolved metals with heat, so I'm not familiar with how they behave cold. 

If you'd like to test your solution for platinum, if you'll follow these steps, you'll be able to do so. 

Using a spot plate-----(not a piece of paper) place a drop of solution in a cavity. Add to this drop a crystal of green copperas (ferrous sulfate). You should see a very thin sheet of gold form, and the color of the drop change, lighter in color. Using a glass rod, stir the drop until the entire crystal has dissolved. If all the gold has not precipitated, add another crystal. Once the gold is down, split the drop in two, then test one with DMG, which will precipitate the palladium, leaving only platinum in solution. Allow the yellow precipitate to settle, then drag as much of the solution to another cavity as you can, leaving behind the yellow material. You can now test with stannous chloride-----and expect a coffee colored reaction if you have platinum present. If the concentration is quite low, the color may even lean orange. The darker the reaction, the deeper the concentration. You can use the second part of the sample to repeat the test if needed. If not, wash the entire thing into your stock pot, for eventual recovery. 

Harold


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## Aristo (Aug 20, 2007)

Much appreciated Harold.
Thank you.


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## Aristo (Aug 20, 2007)

I diluted the solution and pulled the gold with BDG...and it seemed ok.
However , I added ammonium chloride to the dilute , but no ppt.
I recehecked with stannous chloride...the reaction is black with dark red.
grrrrrrrrrrrrr.

I await ...


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## lazersteve (Aug 20, 2007)

Aristo said:


> I added ammonium chloride to the dilute , but no ppt.



The solution should be concentrated before attempting precipitation of Platinum or Palladium. Work with a small volume first to get the feel of the reaction before attempting precipitation of the whole batch. 

Steve


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## Aristo (Aug 20, 2007)

Steve...
Thats the problem I have. I am not sure what order of preference I should use . I am concerned that if I use the ammonium chloride in the concentrate , I may affect my gold recovery and vice versa.
I am not a big fan of using urea and SMB.
Again , thanks for all the input. Hopefully there may be some benefit here for me and all that is reading this. Gold recovery is such a hush hush affair , it is refreshing to see the knowledge being shared on this board.


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## lazersteve (Aug 20, 2007)

Aristo,

Since you already used the BDG this should have removed the gold if you performed the extractions to completion (last clean BDG wash is clear after scrubbing). If this is the case, you should concentrate the solution and then add ammonium chloride to the saturated solution. If nothing precipitates (orange powder = Platinum Ammonium Chloride) then heat the solution and begin adding single crystals of sodium chlorate to precipitate the Palladium Ammonium Chloride (red powder). Of course the procedure is different for UREA and SMB users.


Steve


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## Aristo (Aug 21, 2007)

I added aluminium foil to the diluted solution.
Will see what happens tomorrow.


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## Aristo (Sep 18, 2007)

I have dropped all the metals from a sample solution using aluminium.....got a black ppt ( not sure what it is ).
I took another sample and added bdg without diluting.....got gold and then I added ammonium chloride and I can see a wonderful red ppt. I presume this is Platinum or is it a platinum salt?.
I washed the BDG with dilute HCL and the wash is testing red on stannous chloride...I didnt throw it out.....not sure what it is...solution is yellow.

After the platinum and gold extraction , aqua regia solution still red.


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## Irons (Sep 18, 2007)

Be careful how you dispose of your spent solutions from processing Dental Amalgam. It contains a large amount of Mercury. If the EPA catches you pouring it down the drain, you will pay dearly. Waste treatment plants check for Mercury on a regular basis and they have the ability to track it right back to your drain pipe. If you have a septic system and well, you may kill your whole family and poison your neighbors' groundwater for a long distance.

Mercury is a deadly poison when in solution.

Be careful how you handle it.

Personally, I will not process Amalgam for that reason.

EPA certified facilities have the procedures to properly dispose of it. They don't pay as much for Amalgam for the extra cost involved.


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## Aristo (Sep 18, 2007)

Thanks for that insight.
Safety should always be top priority in any process.
I will be taking the spent solution to a certified company for proper disposal.


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## Irons (Sep 18, 2007)

Unfortunately, they will charge for the service minus any recoverable metals.

Like any other business, it's a good idea to do a cost analysis to see if it would be safer and cheaper to send material to a registered faciity.

30 years ago, when I was taking Chemistry, people used to routinely dump dangerous compounds down the drain. Not any more, unless they're unscrupulous.

It's not worth losing everything over a bunch of lawsuits when the neighbors find out what has been going on.

My place is in an industrial zone and all discharges are monitored by the city. Any spike in hazmat coming down the pipe will get a visit from the folks at city hall, so i'm very careful.


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## Aristo (Sep 20, 2007)

So...
could anyone tell me what my red ppt is??


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## lazersteve (Sep 20, 2007)

Aristo,

Is the red powder soluble in H2O? How about 50% ammonium chloride in water? When heated does it give off any vapors and change appearance?

Steve


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## Aristo (Sep 20, 2007)

I havent checked it with anything Steve. I am aware that I dissolved material containing gold , platinum and palladium. I removed the gold with BDG.
The red ppt came from the addition of ammonium chloride to the leach ( AR ).


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## lazersteve (Sep 20, 2007)

Sounds like Platinum except it's red instead of orange. Filter some out and test with water to see if it redissolves. 

Steve


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## Aristo (Sep 20, 2007)

I am including pictures .....not sure if it is red or orange ppt.
I do have a yellow liquid ( hcl / bdg wash ) which shows black on stannous chloride.


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## Harold_V (Sep 20, 2007)

lazersteve said:


> Sounds like Platinum except it's red instead of orange. Filter some out and test with water to see if it redissolves.
> 
> Steve



Even if it does, that won't tell you what it is. I'd suggest dissolving a trace in a drop of water, split the sample and then testing with both stannous chloride and DMG. If it's platinum, the DMG won't react. If you get a yellow precipitate, it's palladium. Platinum should respond with a brown (coffee) color (with stannous chloride).

I've seen platinum precipitate with a light orange color, but never red. 

Harold

Edit: comment added for clarity


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## Platdigger (Sep 20, 2007)

Could it be Rhodium? Well, of course not if you did not disolve any.


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