I have been purifying precious metals from jewelry for a few years and have gleaned many good tips and ideas from this forum ... Thank you all ... I was at the dentist recently and he asked if I could refine gold teeth which will be a first for me... Any suggestions ?? ... can I go directly to "aqua regia," nitric acid (HNO3) and hydrochloric acid (HCl) , or are there other steps to consider??
gold filled teeth
- Thread starter RevMatt
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Dental alloys contain gold and palladium, often as much as equal portions of both.
To start heat the teeth to a red glow, it will smell from the bone you burn off but since teeth can carry the AID's virus you cannot be too careful.
Next crush off whatever non precious material you can in a mortar and pestle the rest you will separate and process for precious metals.
2 options next depending on what equipment you have in your refinery. If you have a silver cell, inquart the metal and part it to get relatively clean gold for aqua regia follow up. Then cement the Silver and Palladium to make an anode for your cell. The Palladium will show up in your electrolyte or as slimes in the anode bag.
If you don't have a Silver cell the Palladium can be recovered from the parting liquid using Dimethylglyoxime and reduced to a metal from the Dimethylglyoxime salt.
Another option is straight aqua regia, without inquartation, to drop the gold with ferrous sulfate followed by the Palladium with Ammonium chloride and sodium chlorate.
If you want to avoid the PGM salts entirely (they require careful handling due to their toxicity,). you can cement the Palladium on copper after dropping the gold. Then re-dissolving the Palladium metal in nitric acid you can cement it a second time using fine copper powder carefully and slowly added until all of the Palladium drops. That can get you pretty pure Palladium if you don't add the Copper too quickly or in excess.
@kurtak has mastered the art of cementation of PGM's on fine copper powder. If you choose that route surely he will give you some handy tips.
To start heat the teeth to a red glow, it will smell from the bone you burn off but since teeth can carry the AID's virus you cannot be too careful.
Next crush off whatever non precious material you can in a mortar and pestle the rest you will separate and process for precious metals.
2 options next depending on what equipment you have in your refinery. If you have a silver cell, inquart the metal and part it to get relatively clean gold for aqua regia follow up. Then cement the Silver and Palladium to make an anode for your cell. The Palladium will show up in your electrolyte or as slimes in the anode bag.
If you don't have a Silver cell the Palladium can be recovered from the parting liquid using Dimethylglyoxime and reduced to a metal from the Dimethylglyoxime salt.
Another option is straight aqua regia, without inquartation, to drop the gold with ferrous sulfate followed by the Palladium with Ammonium chloride and sodium chlorate.
If you want to avoid the PGM salts entirely (they require careful handling due to their toxicity,). you can cement the Palladium on copper after dropping the gold. Then re-dissolving the Palladium metal in nitric acid you can cement it a second time using fine copper powder carefully and slowly added until all of the Palladium drops. That can get you pretty pure Palladium if you don't add the Copper too quickly or in excess.
@kurtak has mastered the art of cementation of PGM's on fine copper powder. If you choose that route surely he will give you some handy tips.
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A silver cell for just this recovery may be overkill unless you can keep up with the Silver to feed it. It is only an option if you are already running a cell.
kurtak
Well-known member
Any dental gold alloys with 25% (or higher) Pd will be silvery white (white gold) rather then yellow gold color as the Pd literally "bleaches" the yellow color out of the gold
Other metals that will bleach the yellow out of gold (at 25%) are Pt Ni Mn so white gold alloys can have 25% of anyone of those metals or a combination of those metals that equals (at least 25%) of those metals
Ni will not be used in dental gold because some people are allergic to Ni (not sure about the Mn)
If there is less then 25% of those metals in the alloy the yellow color will "start" to show with the yellow getting deeper in color the less of those metal in the alloy
White gold can be made with less then 25% of those metal by using other white metals in the alloy like Zi or Ag but the "white metal" in the alloy needs to then be "somewhat" greater then 25% as Zi & Ag do not actually "bleach" the gold but rater dilute the gold
My point being that with dental gold is if it is silvery/white it is likely alloyed with 25% or more Pd &/or Pt
If it is silvery/grey it likely has some but much less Pd/Pt but also some Zi/Ag in it (as well as "maybe" Cu)
If the dental gold is actually yellow/gold in color it will likely run (plus/minus) 75% gold with the remaining 25% made up of Cu Ag Pd - maybe "some" Zi &/or Pt in place of the Pd
With yellow/gold dental the Pd will generally only run 3 -5% (or Pt if used in place of the Pd - which is more rare)
I just had 4 yellow/gold crowns XRFed & they ran 75% gold 3% Pd & the remainder Cu/Ag with a trace of Zi
They make many different dental alloys
https://www.drericmorrison.com/post/understanding-the-difference-between-dental-gold-regular-gold
https://pocketdentistry.com/7-gold-and-alloys-of-noble-metals/
And one more side note; - they also make caps/crowns out of SS (stainless steel) which of course will be silvery/white - so can be mistaken for white gold dental
Kurt
Don't neglect white metals just because they are white. I just bought a bucket of "stainless" sprues from a dental lab. About 10% are a 20% Pd Alloy. Still don't know how I'm going to sort it all, since I don't have XRF. Thus far it's been by filing off some material and testing the filings in AR with stannous. It's a pain in the butt.
Since stainless passivates in nitric and Palladium dissolves in nitric you could try a small sample in a nitric bath.
