Prestart cleaning and preparation and refine method.

[adam mizer]

Hi, its been a while, many years like 10 years or so since I did some refining, had a different name on the board then lost password back then.
I have 200 grams of this material from Chinese Dental Lab, was purchased only from visual of XRF reading and weight.
With that said I'm preparing to refine. Just cleaning and preparation now.
Looking for opinions of others how you might proceed.
Was thinking maybe roast torching first then a wash in alkaline based cleaner and rinse off cleaner.
Then 50/50 HCL and water to get rid of minor base metals. (Wash, rinse).
A question would be go for the gold (AR) or get the silver (Nitric) out first?
Also thinking about the small amount of Rh, not to refine but just to get it.

 

[Martijn]

Try different approaches on tiny bits of the powder, and when you have found one that works, apply to the lot.
what was in the mix according to the XRF?

 

[nickvc]

Is the powder metallic or metals and ceramic and or other powder ?

 

[adam mizer]

Try different approaches on tiny bits of the powder, and when you have found one that works, apply to the lot.
what was in the mix according to the XRF?

Yes this makes more sense.
I will approach this with a sampling first.
XRF states 67.7% silver, 21.5% gold, 1.1% rhodium the rest base metal. Don't know how much powder percentage of weight does not show up on XRF readings.
@nickvc, its a guess at the powder at this point. However ceramics and metals is what it should be.
Maybe a 5-10gram sample is where I will start.

I'm waiting for propane supplies, I used all my acetylene getting 5lb's of contacts off and decided propane and oxygen is much cheaper.
Still have a couple pounds more of contacts to remove (the smaller stuff). Some pics of that.
Recently learned Acetylene hose is a TYPE R and Propane hose is a TYPE T.
TYPE R hose used with Acetylene will dry out and rot because of the oils in Propane.

 

[nickvc]

I asked because it only shows metals on the xrf which means a lot of the material will not be reported so the percentages may be well off.

 

[adam mizer]

I asked because it only shows metals on the xrf which means a lot of the material will not be reported so the percentages may be well off.

Yes I was wondering if XRF does not display powder how much percent mineral in the bottle.
Maybe I'll go to LINDE today and get some acetylene and small jeweler torch head and weigh out some grams and make that bead to find out.

 

[anachronism]

Personally I'd take 10g and use Nitric first to take out the silver.

 

[4metals]

I agree with Jon, In fact if you get a good digestion and follow it with an aqua regia dissolve of the gold you could be done. The insolubles should hold any Rhodium. I have never seen dental without Palladium before and i have never seen dental in that form. (powder).

One concern would be any coatings on the material which would prevent dissolution which need to be burned off by melting and shotting the material. But the powder, if it dissolves easily, will be an easier way forward. If your insoluble fraction exceeds what you should expect from nitric parting and aqua regia, the material may have been coated by milling with a malleable metal and require melting.

 

[adam mizer]

Wow.... what a loss.
The powder yield was absolutely miniscule unmeasurable.
Oh well had to give it a go. Wanted to try.
I have the rest sitting in nitric.
The 10gm roast and melt mixed with borax gave me a sticky mass of brown glass like.
Crushed the glass and found super tiny piece of metal unmeasurable.

 

[FrugalRefiner]

Well, it may well be a loss, but I wouldn't totally give up after one failed attempt. I know you've said you put the rest in nitric, but I might have tried a few more samples with a few more methods.

I noticed the tin content. That could give you problems with a nitric leach. We'll see. You can deal with it, but it's extra work.

I wouldn't have expected a good result trying to melt some with borax. If there's ceramic in there, you'll need something to help eliminate it. I believe cryolite is often mentioned.

Dave

 

[adam mizer]

I'll look into cryolite.
Torching in the stuff or?
Cryolite appears bad so care must be taken.
Uses are aluminum smelting, and glaze chemistry contributes to the homogeneity and fining of glass.
Letting it sit in nitric overnight.

 

[adam mizer]

Well apparently from the 10gm sample recrushed glass ceramic powder in nitric.
Silver chloride was found. Not much but enough to make me continue.
I'm under the impression there was no need for roasting.
The ceramics are heavy enough to drop and filtering easy after they settle.

 

[goldshark]

As with all dental powders, check for the presence of Mercury. Do a small batch in Nitric, then see if any is present on a Copper rod or sheet.

 

[kurtak]

Well apparently from the 10gm sample recrushed glass ceramic powder in nitric.
Silver chloride was found. Not much but enough to make me continue.
I'm under the impression there was no need for roasting.
The ceramics are heavy enough to drop and filtering easy after they settle.

Per the bold print - as long as you used distilled water with the nitric leach there should be NO silver chloride

According to the XRF read out the powder has 3.647 % Sn (tin) in it so the white cloud you are seeing is more then likely meta-stannic acid - the nasty tin paste refiners hate as a result of tin reacting with the nitric

Wow.... what a loss.
The powder yield was absolutely miniscule unmeasurable.

The 10gm roast and melt mixed with borax gave me a sticky mass of brown glass like.
Crushed the glass and found super tiny piece of metal unmeasurable.

Your test melt may not be a true representation of the actual metal in the powder - in other words there may (or not) be more metal in the powder then you are seeing in that test melt

As pointed out by 4metals - IF (the BIG IF) there is ceramic in the powder that can "prevent" some of the metal from properly melting - even to the point that it will not form into beads of metal that can be seen with the naked eye which means it "could" be tied up in the slag & you just don't see it even as tiny beads

This is because the ceramic particles could very well literally be "combined" with metal particles (from when they milled the powder originally) thereby preventing all the metal from actually melting & forming actual metal beads

To overcome that problem you MUST have a flux that will "dissolve" the ceramic in order to allow the metal to actually melt & then slag off just the ceramic - so you NEED cryolite &/or at least fluorspar to dissolve away the ceramic from the combined ceramic/metal so that only the ceramic goes off in the slag --- if there is a lot of ceramic you will also NEED a collector metal otherwise metal that is to small to see with the naked eye can very well end up in the slag

As well - if the ceramic & metal has been "combined" (from original milling of the powder) it is very likely that you will not get all the metal leached out of the powder with acid leaching as the ceramic - if combined with the metal will prevent the acid from fully dissolving the metals

I have the rest sitting in nitric.

I hope you don't mean that you put ALL of your powder in acid to leach it - but that you are doing a small test sample leach ???

So - IF (the BIG IF again) you still have most of this powder yet - you need to do another test melt (smelt actually) & you need to do that with some cryolite in your flux

I see you live in Boise Idaho - I live only 3 hours away from you & I have both cryolite & fluorspar so if you still have most of this powder yet we can make arrangements to get you some of that & you don't need much so I will just give you what you need

Do NOT provide you personal info (phone # etc.) here on the open forum - send me a PM so we can make arrangements to get you cryolite & fluorspar - IF you need it

Kurt

 

[kurtak]

As with all dental powders, check for the presence of Mercury. Do a small batch in Nitric, then see if any is present on a Copper rod or sheet.

Being as how it is still in powder form there should be no mercury in it

Dentist that still do amalgam fillings get what is needed to do the amalgam filling in a two part packet - in that packet they have a capsule of the metal powders (Ag etc.) along with a capsule of mercury & they do not mix the powder with the mercury until they are ready to fill the cavity with the amalgam --- if they per mixed the powder with the mercury (to make the actual amalgam) before needing it to actually fill the cavity the amalgam would harden up & they would be unable to squeeze the amalgam into the cavity

So if this powder had mercury in it - it would be a hard chunk of metal - just like a filling that falls out of your tooth - instead of being a powder

Besides that - if there was mercury in it - it likely would have shown up on the XRF read out

Kurt

 

[kurtak]

i have never seen dental in that form. (powder).

If it is for doing dental "amalgam" fillings then it will be in powder forum - they don't mix the powdered metals (which are actually "atomized" metal alloy powder) with the mercury to make the actual amalgam until just before filling the cavity - if they mixed the atomized metal powder & mercury to create the amalgam in advance of filling the cavity the amalgam would start to "set up" (harden) & they would not be able to squeeze the amalgam into the cavity

The amalgam "starts" to set up in "about" 15 - 20 minutes --- it then takes about 24 hour to fully set up (harden)

The reason the amalgam sets up & gets hard is because when the mercury is mixed with the metal powder the mercury actually starts dissolving the metal powder - that reaction of the mercury dissolving the metal (like any reaction) takes some time so at first the amalgam is more fluid - over time - as the mercury dissolves more of the metal powder it becomes an actual alloy/matrix of the mercury plus metal powder & that alloy/matrix hardens (due to the harder metals being dissolved in the mercury)

The foundation metals used in making the metal alloy - which is then atomized are primarily silver, tin, copper & zinc with other "traces" of metals sometimes added (such as PGMs &/or gold - in traces) --- the zinc is added in the "alloy melting" as an anti-oxidant to prevent oxidation of the copper & tin during the melt & zinc burns off during the melt

I have about 4 ozt. of powder similar to the OPs (no gold but "trace" of palladium) that I got from a couple of dentist that quit doing amalgam fillings & went entirely to doing composite fillings

I have 200 grams of this material from Chinese Dental Lab

I am guessing (but could be wrong) that this (OPs) powder is a metal powder for dental amalgams - it's just a "Chinese" recipe for the metals in the atomized powder

Kurt

 

[4metals]

If it is for doing dental "amalgam"

That makes sense, and yes I have retorted similar material, when I think of dental today it is either caps and crowns or crematory scrap.

 

[adam mizer]

@kurtak silver chloride after salt added. This also was able to filter rather quickly.
Yes I'm quite sure there was prevention in melt be it from the ceramic.
I'll have to get some cryolite to see how it works.
Thank you for the offer, I'm thinking getting a pound of the stuff as it may come in handy.
I still have my 10 gram sample dried in filters (putting in bottle) and another sample boiled in AR letting it cool right now.
Keeping all the solids for further tests.
I drove through your town a while back and sometimes pass the turn off as I take care of utility solar inverters on trips to Oregon.