Dental Scrap in AR

[rainmaker]

I recently sent some silver colored dental scrap to a refiner I use (no names) He returned it to me stating there were no PMG's in it. Well believing "it's OK to be paranoid when the whole worlds after you", I droped it into some fresh "poor mans" AR. What I got is 2 batches of brown AR and my dental scrap appears to be basicly unscaved. The scrap was/is casting splatter,and sprues with some retainer/bridge type material.

Any comments and/or wisdom as to what I have and /or need to do next would be appreciated.

Thanks everyone

 

[butcher]

stainless steel? try boiling 150 degrees, also test your solutions,
Harold can give a good report on this.

 

[Harold_V]

There's a fairly simple test to determine what you have when dealing with "white" dental scrap. The material that is valueless is very rigid and will not bend. It snaps, although with considerable resistance. By contrast, if you encounter white materials that are malleable, they generally contain platinum and palladium. The color of the AR you described sounds like that's exactly what you had, although most likely mixed with the high temperature alloy material that is commonly used.

You can take advantage of the valueless material to cement the values down, assuming you leave the material in contact. Your objective will be to eliminate the junk, not to cement the values, but that's how it's done. I used that method a couple times when I received a large lot of material that would have been difficult to sort. By starting with AR and allowing it to work until it is exhausted, you'll notice that the initial color is as you describe it, a dark brown. Continued heating will begin the cementing process, whereby the valueless material goes into solution in the process of cementing down the values.

By carefully monitoring your solution, you can discard the worthless stuff easily, then start again, recycling the same cemented metal a few times. Each time you follow the procedure you'll eliminate more of the junk, and have more of the values extracted, and cemented.

The barren solution should be a dark green color after you've extracted the values. If it tests barren with stannous chloride, it should be separated from the solids and discarded. If it has any color beyond a dark green, it likely has values contained within. Sneak up on the last little bit so you have taken advantage of the cementing process to eliminate all but a trace of the valueless stuff. Make sense?

If I left out something obvious, ask again.

Harold

 

[61 silverman]

Harold , I also have some dental material , that some seemed very TOUGH and some of it flattened on a small anvil, with some convincing!! My Biggest concern on how too deal with this material as the concern that I have read there could be ( Mercury ) in some dental scrap..Would that only be in Tooth Fillings,,?? or in the bridge work if ..?? How could I test for presence of any,,?
Thanks MARK

 

[Harold_V]

There will be no mercury in bridge work, but if the bridge was attached to teeth that had been crowned (I don't know if that's a possibility), there's no telling what may be under the crown. It's not uncommon to crown filled teeth---four of my (gold) crowns have silver amalgam inside them.

To my knowledge, there is no ready test, but if you have dental work that is to be refined, using an anvil, smack the piece with a hammer. That should release the tooth that accompanies the values, and if the item has mercury, it will be apparent by the inside color. If memory serves, it is somewhat brittle, not ductile, so it doesn't flatten, it crumbles instead.

Great care must be exercised when melting such items. If you melt them without fume control, you'll be exposed to mercury vapors. Not a good thing to experience. If you discover silver amalgam, it's a good idea to remove it as much as is possible---the tin contained within can complicate filtration of solutions.

The material I described (white, with no value to the home refiner) isn't likely to deform much. It will break instead, so if you have some white material that has flattened, I'd be inclined to think it may have values within. When in doubt, dissolve a small piece in AR----it the solution comes out dark green, pretty good chance it's valueless. Look for a brown tint, but never assume anything. Test with stannous chloride.

Harold

 

[61 silverman]

Thank's Harold, I have smashed most all of the pieces that had any tooth on them a bit more to do.. I'll try to put up a couple of pics. of the material if you think it'll tell you something..
MARK

 

[61 silverman]

hope this pic will load,

 

[Harold_V]

Needless to say, the blurry picture doesn't tell me much, but one thing is discouraging. The objects appear to have a blue cast. That is not a good sign. I highly recommend you dissolve one of the snippets in AR to see what it yields. I expect the solution will be dark green. Be certain to test, regardless of what it looks like, however. Also, boil the piece long enough to consume the AR, so it doesn't interfere with a reaction. When AR is tested at strength, it's not uncommon to not get a reaction, even when you have values in solution.

If the pieces broke up when being hammered, that's also a good sign that they are not of value. The high temperature alloy used for bridges and other appliances tends to be very brittle and not malleable at all. If you attempt to bend it, it breaks instead of bending.

If you find white appliances (such as a crown, or a metal cap with porcelain on top) that has a more white/yellow appearance, and is more malleable, good chance it's platinum group metal.

If you find you have values mixed with non-values, and you can't, or don't want to sort them manually, lets talk some more. I used a process to eliminate the base metals that made it much easier. It revolves around using AR, so that may give you a clue how it is accomplished.

Harold

 

[Oz]

When AR is tested at strength, it's not uncommon to not get a reaction, even when you have values in solution.

Have you had your stannous not indicate accurately after you had eliminated your nitric?

Yes, I’m being a knowledge thief again.

I love hearing you talk Harold.

 

[Harold_V]

Have you had your stannous not indicate accurately after you had eliminated your nitric?

To the best of my recollection, yes, but only when my stannous chloride had degenerated. It is for that reason that one should always have on hand a standard solution. Gold is the easiest one to make and use, so that was my choice. When I failed to get a reaction from a solution that I suspected as having value, the first thing I did was to test my stannous chloride.

Regards testing a strongly acidic solution, even with viable stannous chloride, my observations were that you'd get a reaction, but it might be very short lived. It wasn't uncommon to see a purple ring develop and instantly disappear. Not being a chemist, I can only assume that the reaction was dissolved by the free acid. Chris or Lou may have a better explanation.

Harold

 

[Oz]

Before I do anything else in the “shop” I check my stannous against a control gold solution. I have heard of many interferences with a stannic test that have not yet played out empirically with what I have done so far. It makes sense that with a strongly acidic solution that the tin could be incorporated rapidly. I too look forward to the chemists on the forum giving their input.

 

[61 silverman]

Harold Thank you again for yoour expertise,, I think you may suggest that I follow HOKE's method possibly,, like rolled or filled gold HCL--wash clean -- Nitric - wash re- wash Clean -- Both steps boiled too remove any base metalls reachable,, After those two sepperate steps AR might Be the next step,, Please tell Me if I am on the wrong thought path.. Thank's again MARK

 

[61 silverman]

I hope this pic will be a little more help.. some of the bridge work has areas of it that are solid and then there are hollow spaces like crowns.. also there are some discs that came in the same buy,, all from an Italian Dentist..

 

[Harold_V]

Harold Thank you again for yoour expertise,, I think you may suggest that I follow HOKE's method possibly,, like rolled or filled gold HCL--wash clean -- Nitric - wash re- wash Clean -- Both steps boiled too remove any base metalls reachable,, After those two sepperate steps AR might Be the next step,, Please tell Me if I am on the wrong thought path.. Thank's again MARK

Right now, what you need to conclude is if you have values, or not. It is apparent that you have more than one thing to consider, so without having some experience, you're going to have to go through the same testing procedure with a sample of each thing you have.

As you alluded, Hoke can guide you through the proper procedures, but you have to understand what to do, and when to do it. Right now the only thing you should concern yourself with is testing---do not get overly concerned about refining procedures, for you may have nothing to refine, and what you have, assuming you do have value, may require more than one procedure, although you could process everything by inquartation.

Begin by doing as I suggested. Place a tiny snippet of each type of material in a test tube or a small beaker (do not combine them---run each sample separately), and dissolve it as best you can, using a drop or two of nitric, and four times as much HCl. A few drops of water should be included. You must get some of the material in solution so it can be tested. Watch for the colors to develop as the material dissolves. If you see yellow or brown at first, and it slowly changes to green, you have values mixed with base metals, which are cementing the values. You can then add a few more drops of AR to continue dissolving the material.

If you find that the color that develops is nothing but a dark green, pretty good chance you have nothing of value. Color change is important, so watch closely. If you dissolve everything that is included, test the solution with stannous chloride that is known to be good (test against a standard solution). If you get any kind of reaction that displays a dark color, you have values, gold, palladium or platinum, or combinations of all of them. Set all of that kind of material aside, and continue testing until you have tested a sample of each type you have.

I talked about sorting chemically. You can take advantage of the fact that base metals will cement values by dissolving everything in AR, starting out with a small amount, not enough to dissolve all of the metal. It should be allowed to dissolve (heated) until it no longer is performing any work, then allowed to cement the values that have gone into solution. When it is barren of value, it will be a dark green color, but it should always be tested with stannous chloride.

When the solution tests barren, it should be diluted with tap water and allowed to settle well, so you don't lose any of the fine particles of values. Once settle, the solution is siphoned off carefully, then the process is repeated. By carefully dissolving the material and allowing the base metals to precipitate the values, you can eliminate almost all of the base metals, then process the last solution for values. You will have eliminated most, but not all of the base metals, so the solution will be lightly contaminated with garbage. Does this make sense to you?

The newest picture doesn't help, it's too small to discern what you are trying to show.

You mentioned an Italian dentist. Is his work from Italy? Could be their practices are different from those here in the US, so there could be some things that I wouldn't understand.

A parting thought. Dental wastes will likely be the most complex scrap you encounter, due to the mixes of metals. You can expect silver, gold, platinum and palladium from such materials, so you will have to have a broad understanding of how they interact with one another. For example, if you have silver in the presence of platinum, some platinum will be dissolved in nitric acid----so silver will become the carrier of a portion of your values. It is for that reason a refiner should get involved in parting silver, where such values are recovered.

Harold

 

[61 silverman]

THANK YOU very much, I will follow that advice and hope for some good results,
I have a total of 215 gram of material casting sprues mis-run (not filled)flashing,, gold crowns , and dentures w/porcelin.. and the discs in previous pic, Yes the material is from ITALY i'll show a picture of the bag the discs came in =NOBILDENT'e metalli odontoiatrici
I don't speak Italian but i think it means "dental metal basically"

 

[butcher]

this is good information from these disscusions, I have been getting into dental metals together and this information will be very hepful, keep it up I am taking note's.
thanks
Harold I remember you said you might think of writing a book, if you thought you could find three people interested in reading it.
to me you have been writing a book on this forum and people all over this world are benifitting from it, Thanks to a young man with an interest, who started this forum, and all the wonderful people who contribute to it, full of very useful clean information.

 

[Harold_V]

Funny, without having an education, the idea of writing a book seems out of reach for me.

It's easy to address questions that are asked, assuming I have had parallel experiences, but there is so much I do not know and understand that I feel a book at my hand might just become a book of humor!

Besides, it would be hard to improve on the great work of Hoke!

You may have noticed, she is my hero.

Harold