AuSn 80/20 alloy

[Joe cocker]

I will then try this first « beginner » process:
- 50 g AuSn in a beicher
- 100 mL HCl 33%
- heat 70 degrees
- filter
- dry the powder and weight to evaluate if quantity is closed to 40 g
a- if not: re process with HCl
b- If yes: melt by adding borax in the recipient before ( a few grams?)

What do you thing about that ?

Thanks a lot

 

[Joe cocker]

Gold do not dissolve into HCl, Tin(Sn) do.
The mud will be the gold.

If you suspect more Tin is left.
Dissolve the powder in HCl Peroxide or HCl Bleach.
Do NOT use AR, because Tin and Nitric makes metastannic acid.
After dissolving, precipitate with SMB, wash and melt.

Hi Yggdrasil,
When you said that mud is gold, I thought I can directly melt this mud! But you wrote « after dissolving, precipitate with SMB.. ». Does it mean that I need to dissolve the mud in a solvent ?
Thanks a lot

 

[goldshark]

At 20% tin, in a button, will the HCL adequately dissolve through it? Also, will Sn adsorb into a cupel? I don't mean to jack the thread.

 

[Joe cocker]

Hey! Happy new year ! Anyone could validate the process here above ? Can I try that or am I wrong ?
Thanks a lot !!!!

 

[kurtak]

1- put solder residual AuSn 80/20 in a becher

If I understand this right Joe cocker is dealing with an 80/20 alloy of Au/Sn - NOT - a mix of gold - and - tin

Like say gold powder that has tin powder mixed in with it

IF (the big if) it an alloy of Au/Sn he can not separate the tin from the gold with HCl

So - we need to clarify - is he dealing with an alloy - or a mix of two different/separate metals

Kurt

 

[kurtak]

HCI will not resolve gold, it will dissolve the tin and what you have left will be gold.

If it's an alloy HCl will not dissolve ether the gold or the tin - at least not when the gold is at 80% & tin at 20%

If it was the other way around - 80% tin & 20% gold then yes HCl would dissolve the tin leaving gold behind

Kurt

 

[Joe cocker]

Hi Kurtak,
Thanks for your reply!
It is well an alloy containing 80% of gold!
Then , there is no “home process” to refine gold ?

Thanks a lot

 

[kurtak]

Yes it can still be refined at home - because of the tin it is more difficult to refine then other gold alloys

Because causes problems that you don't normally have with other alloys it will depend on you set up, experience & understanding

Now that we know it is an alloy - we can better help you through it

Kurt

 

[Joe cocker]

Up up ! Hope someone will be able to separate this tin from the alloy !
Thanks

 

[Joe cocker]

Happy new year to all !!!

 

[snoman701]

I don't think you followed my comment about the borax. If you melt Au80/Sn20 with an excess of borax, with an oxidizing flame, you can nearly purify the Au by selectively oxidizing the SnO2. At high temperature, SnO2 is readily soluble in the flux, leaving you with nearly pure gold.

 

[goldshark]

Still wondering if Tin will cupel. Am almost done with my new furnace, so haven't been able to try yet. Just wondering if anybody else has tried it.

 

[goldshark]

Snowman, do you do your process in a roasting dish (ceramic, pretreated with borax), or what? Any tell tale signs the reaction is complete? Thank you.

 

[Joe cocker]

I don't think you followed my comment about the borax. If you melt Au80/Sn20 with an excess of borax, with an oxidizing flame, you can nearly purify the Au by selectively oxidizing the SnO2. At high temperature, SnO2 is readily soluble in the flux, leaving you with nearly pure gold.

Thanks a lot , I understand better , I can try that !!!!

 

[silver1]

Try a Fizzer cell. Hcl and electricity. Both will go into solution. Drop Au with choice of percipient.

 

[Joe cocker]

Hi all and happy new year again ,
Last question before I order the materials I need to start …
Is Sn oxidation (SnO2) with borax is the best option to separate AuSn alloy?
Thanks a lot

 

[kurtak]

I don't think you followed my comment about the borax. If you melt Au80/Sn20 with an excess of borax, with an oxidizing flame, you can nearly purify the Au by selectively oxidizing the SnO2. At high temperature, SnO2 is readily soluble in the flux, leaving you with nearly pure gold.

snoman

Have you actually done this ?

I ask because I don't believe it is that simple

at best - an oxidizing flame "on the surface" of the molten gold will yes oxidize the tin atoms to SnO2 - BUT - ONLY the tin at the surface (which will then carry of in the borax flux/slag)

I could be wrong - but I believe in order to oxidize the Sn "inside" the molten gold you need to get oxidation of the tin "inside" the molten gold --- that is normally done by purging oxygen/air "through" the molten gold in order to oxidize the tin IN the gold thereby bring the SnO2 to the surface to be slagged off

Without purging air through the molten gold the tin IN the gold is going remain molten tin along with the molten gold & the only tin that will oxidize - by the oxidizing flame - is the tin on the surface of the molten gold --- when you hit it with the borax the borax will slag off the "surface" oxidized tin - but then the borax is also going to shield the molten metal from the oxidizing flame preventing further oxidation of tin at the surface

Without oxidizing the tin inside the molten gold it's not going to come to the surface to be slagged off --- they normally do that by bubbling air through the molten gold --- otherwise only a trace of tin - at the surface will be oxidized & slagged off

At least that is my understanding - I could be wrong - but I believe if you don't purge air through the molten gold (or silver) it won't oxidize the base metals enough to bring them to the surface to slag off - other then the base metals at the "very" surface of the molten metal

Hi all and happy new year again ,
Last question before I order the materials I need to start …
Is Sn oxidation (SnO2) with borax is the best option to separate AuSn alloy?
Thanks a lot

I would wait to get a better explanation of the process

Kurt

 

[orvi]

Hi all and happy new year again ,
Last question before I order the materials I need to start …
Is Sn oxidation (SnO2) with borax is the best option to separate AuSn alloy?
Thanks a lot

I will recommend to chill down, read some literature about it, because it appears (from your questions and misunderstandings) that you do not have much experience in refining. Certainly try small batches (like 1-2 g). It is always easier to recover mess from 2 g than from whole batch. Never discard anything from the reactions and refining unless you are sure that it dont contain precious metals.
In general, there is no certain guideline, which assure you with best yields and straightforward procedures which work 100% times. Refining don´t work this way material vary from piece to piece, slightest changes make huge differences in behavior of chemical reactions.

From this point, it is all about what is easier for you to catch/what you are more familiar with. Hydrometallurgy (dissolving in acids) or pyrometallurgy (smelting/melting/oxidizing/reducing in furnance) are quite different in many things. But your output (if everything is performed well) should be the same.

If you opt for oxidizing tin from molten alloy, do NOT use graphite/clay-graphite/SiC-graphite crucible - graphite will reduce formed tin dioxide back to metallic tin (just eating up your crucible and not doing anything).

 

[orvi]

snoman

Have you actually done this ?

I ask because I don't believe it is that simple

at best - an oxidizing flame "on the surface" of the molten gold will yes oxidize the tin atoms to SnO2 - BUT - ONLY the tin at the surface (which will then carry of in the borax flux/slag)

I could be wrong - but I believe in order to oxidize the Sn "inside" the molten gold you need to get oxidation of the tin "inside" the molten gold --- that is normally done by purging oxygen/air "through" the molten gold in order to oxidize the tin IN the gold thereby bring the SnO2 to the surface to be slagged off

Without purging air through the molten gold the tin IN the gold is going remain molten tin along with the molten gold & the only tin that will oxidize - by the oxidizing flame - is the tin on the surface of the molten gold --- when you hit it with the borax the borax will slag off the "surface" oxidized tin - but then the borax is also going to shield the molten metal from the oxidizing flame preventing further oxidation of tin at the surface

Without oxidizing the tin inside the molten gold it's not going to come to the surface to be slagged off --- they normally do that by bubbling air through the molten gold --- otherwise only a trace of tin - at the surface will be oxidized & slagged off

At least that is my understanding - I could be wrong - but I believe if you don't purge air through the molten gold (or silver) it won't oxidize the base metals enough to bring them to the surface to slag off - other then the base metals at the "very" surface of the molten metal



I would wait to get a better explanation of the process

Kurt

I think about this as some kind of scorification - i don´t see any major issues with this attempted process.
Tin dioxide have very high melting point, so formed slag will be solid. Periodically crushing the formed slag on top of the molten puddle will slowly oxidize everything.
As with cupellation (which need not to be stirred), convection and diffusion will mix the molten metal anyway, and at these temperatures relatively quickly. Altough, the crust which form will need to be broken periodically, to expose fresh surface of molten metal. Not overshot the temperature (not to vaporize gold) and it should go.

 

[snoman701]

As was said, it's basically a scorification. It's the basis of a reverberatory furnace.

Mixing is crucial, but my molten metals don't exactly sit in one rigid spot, they are always moving all over the place from the turbulence of the torch.

So, have I done it with this particular alloy, no....plenty of others though. I do it most commonly with brass to get the zinc out. I doubt he'll get 999, but it'll get a majority of the tin out given enough time.

Tin oxide is particularly nasty as it's more of a refractory, so I'd expect that an addition of sodium carbonate will be necessary to thin it out. I want to say it goes to tin oxide then sodium stannate which is readily soluble, but I'm not that good with the chemistry.