# What to do with dental amalgam



## hyderconsulting (Aug 11, 2007)

I have about 35 lbs. of dental amalgam which I would like to get refined. Anyone know of a refiner that doesn't charge an arm or a leg to do it? No, I do not want to invest in a mercury still and do it myself. Mention that word here in Tennessee and hazmat turns up immediately. Regards, Chris.


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## goldsilverpro (Aug 11, 2007)

The age old question, "What do you do with dental amalgam?" Not as bad as, "What do you do with silver plated copper wire?" Amalgam is composed of silver, tin, and mercury. The mercury is a little over half of the total weight. You first have to either retort off the mercury or, pay someone else to do it. Someone, somewhere. Maybe more local than you think. After the mercury is gone, the silver/tin alloy runs about 69/31, if I remember right. This alloy is not easy to refine. You can't use nitric acid because the nitric acid dissolves the tin and converts it to metastannic acid, a slimy mess that can nearly stop the action and shut you down. 

The only good way I've seen the silver/tin alloy separated is in a silver cell. And, that's tricky. 

--You could sell it as is. Dental refiners will buy it. The silver runs 33% - $62 per pound -as is. Shop around and find the best price.

--You could have it refined. The minimum lot charge may be around $250. Your 35 pounds of amalgam is worth, intrinsically, about $2170, in silver, less charges. Only God and the refiner knows how much money you'll end up with.

--You could find a buyer that would buy the Ag/Sn alloy, for probably more money, after the mercury is removed. You better make damned sure all the mercury is gone, however. You don't want the buyer to melt it and get mercury poisoning.

-- You could get a silver cell and separate the silver from the tin, after the mercury is gone. Then, sell the pure silver.


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## Harold_V (Aug 11, 2007)

goldsilverpro said:


> This alloy is not easy to refine. You can't use nitric acid because the nitric acid dissolves the tin and converts it to metastannic acid, a slimy mess that can nearly stop the action and shut you down.



Heh! 

That's true, but there is a simple way to circumvent the problem, one I used successfully for years. 

After a full retort of the amalgam, my next process was to heat the remains in an open pan, almost to redness. The remains would actually melt, and were stirred until they broke down by oxidization of the tin. I need not mention that this MUST be done in a fume hood, for there are traces of mercury that still remain. 

The oxidized tin didn't create the slime which is so troublesome---often coming from processing gold filled objects as well. This process made the extraction of silver dead easy. Silver was digested with nitric and tap water (I didn't care about the traces of silver chloride----which were recovered in a later operation). Once digested, the fluid was diluted by about three volumes, allowed to settle, then decanted for recovery of silver on scrap copper. I never had any problems with filtration by this method, but I can attest to the problems that are inherent if the roasting operation wasn't accomplished. 

Harold


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## goldsilverpro (Aug 11, 2007)

Good method, Harold. I hadn't heard of it. Makes sense.


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## Harold_V (Aug 12, 2007)

When I sold my refining business, I had in possession over 100 pounds of mercury, which went with the business. By then, the market was a tough one----buyers of mercury would pay for no less than 150 pounds, delivered. I was told they would accept the amount I had, gratis, assuming I was willing to ship it to them in approved vessels (iron flasks) at my expense. I was taken aback by their "generosity". Dentists were paying well over $15/lb for triple distilled mercury at that time, a process I had experienced myself. 

I really blew it on the mercury. Had I been together, I'd have retorted and washed it a second time, then sold it to prospectors. It was selling, easily, for around $12/lb at the time, but I had my hands full and couldn't do anything with it. Can't win 'em all!  

Anyway, the source of this mercury was all dental amalgam. I ran a large amount of dental amalgam as I described. It really made a difference. I was fortunate to hit on the process by accident---it wasn't because I was clever. Regardless, it sure made a huge difference in the process, which I had dreaded previously. 

By the way, for those that have never retorted dental amalgam, if it has come from a trap in the dental office, you can't begin to imagine the stink. I used to do all my retorting under a large hood that was powered by a 1 horse blower----the one I used to remove gasses when I'd operate my tilting furnace. Even with the hood, the smell was often disgusting. I'm not sure I'd process the stuff today if I was still refining. 

Harold


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## goldsilverpro (Aug 12, 2007)

I ran several jewelers traps. I still remember the stink. Fermentation. You get a similar, but not as bad, smell when using enzymes to strip silver from x-ray film. It's the safest film method but, the ever present stink is everywhere. I think that the enzymes ferment the gelatin.


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## Harold_V (Aug 12, 2007)

Amazing the differences in our experience. I've never even heard about that process. Combined, we'd be a powerful force!

Harold


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## goldsilverpro (Aug 12, 2007)

Thank you, Harold. Very nice compliment.


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## hyderconsulting (Sep 13, 2007)

I contacted five dental amalgam refiners/mercury processors that I could find on the internet to see what they could do or offer to do. I got a more accurate weight on the amalgam and it was 43 lbs., not 35 as previously listed. Also, this is dry dental amalgam that is leftover from dental preparations, not trap amalgam. It has been previously assayed at 55% Ag with traces of Au. 

1) Doral Refining Corp. in Freeport, NY offered $300 total for my 43 lbs. of amalgam as is. I'm not impressed.

2) Mercury Waste Solutions of Union Grove, WI doesn't pay anything for the amalgam or refine it. They also told me they didn't know of any company that did pay for it. I'm impressed even less.

3) D.F.G. Mercury Corp. of Evanston, IL told me that they hadn't refined amalgam in about ten years.

4) Bethlehem Apparatus Co. of Hellertown, PA doesn't buy amalgam but does refine it for you to remove the mercury and then return the residuals. They said for the amount I had they would charge $3.15 per pound.

5) Mercury Refining Company, Inc. of Albany, NY charges 5$ per lb. to refine the amalgam and the payable for Ag is 95% while for Au it is 90% I believe. They do not pay for the mercury now although they used to in the past. They said they would assay for Ag, Au and Pd also. The assay charges are around $200 total as an estimate.

I'm goin to check with Mid-States to see if they can handle refining the silver/tin residuals alright. This appears to be the way to go unless someone suggests otherwise. I have dealt with Mercury Refining before on another shipment of amalgam back in 2002 and they were very straight forward with their refining dealings. I don't have the ability at this moment to refine this material myself so one way or another I'll have someone else do the work for me if they are interested. Also, Mercury Refining said they expected to see some amount of Pd in the amalgam but my previous shipment to them they didn't find any.

Regards, Chris


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