AuSn 80/20 alloy

[Joe cocker]

Hi everybody,

I got AuSn (80% gold) preforms debris (small foils 100 micrometers thick (a few millimeters length and width) and I would like to know if it was possible to refine it by separating Tin from gold?
I have 100 g to refine.
If not refine it is less interesting when you sell it !
Thanks a lot for your help !!!

 

[Lino1406]

Just boil in HCl

 

[galenrog]

Lino is right. Personally, I would take it down a notch. Warm HCl will do, but will take a bit longer. With my physical limitations, boiling acids are always a concern.

Time for more coffee.

 

[Joe cocker]

Thanks for your reply but can you give some details? what HCl % and which quantity?
I put AuSn preforms in a ceramic up or in stainless cup ? And then in a oven or on fire ?
Then what happened ? Tin is vaporized with HCl and gold stay in the bottom of the cup !!
Thanks a lot !!!

 

[Yggdrasil]

First and foremost, according to your statements above, I'd say you are not we quite ready yet.
Read dealing with waste and search for dissolving tin.
Ideally we recommend reading C.M. Hoke's book, but at least download it from the forum and start reading it.

HCl and stainless, not good combination.
Ceramic is better but not good.

Get yourself some borosilicate beakers. Coffe machine mugs are acceptable, kind of.
When heating use a catchbasin of some kind. We recommend Corningware pyrocerams.
Glass forms for the oven can be used, but not ideal.

Use a sand bath or something to spread the heat so it is heated evenly.
All this has to be done outside or in a good fumehood.

Do it inside and you will damage all metals in the vicinity. Nails, bolts anything and everything.
A good way to "kill" your house.

When these things are in place add HCl (muriatic) is fine, heat it until it is warm 70-90 centigrade is plenty and the acid will do its thing dissolving the tin.
What is left is the gold, filter it, and if you think there are more tin do it again with fresh acid.
Dissolve the gold, precipitate, wash and melt.

 

[snoman701]

Melt with excess borax with an oxidizing flame.

 

[Joe cocker]

Thanks a lot
After a few reading and video, it is seem that 20% tin is to be considered as a base material rather than as impurities …
Then shall I use HCl or Aqua regia?
The process would be:
1- put solder residual AuSn 80/20 in a becher
2- put HCl (30%) [ + nitric acid ? Or aqua Regina only)
3- heat to accelerate ??
4- filter and rinse residuals with deionized water ? (Vacuum is necessary ?)
5- precipitate gold using Sodium metabisulfite (is that right ?)
6- how to be sure all gold is precipitated? (Stannous test?)
7- keep solids (mud) by removing the liquid
8- dry on a hot plate (by adding alcohol ?)
9- melt and borax for a shiny color

Thanks for you help !

 

[FrugalRefiner]

Thanks a lot
After a few reading and video, it is seem that 20% tin is to be considered as a base material rather than as impurities …
Then shall I use HCl or Aqua regia?

Do NOT use aqua regia. The nitric acid will turn the tin to metastannic acid which is a pain to filter. Use HCl for the first step to dissolve as much tin as possible. You may not get it all, but eliminate as much as possible.

The process would be:
1- put solder residual AuSn 80/20 in a becher
2- put HCl (30%) [ + nitric acid ? Or aqua Regina only)

Again, just HCl. And the combination of HCl and nitric is aqua regia, not aqua regina.

3- heat to accelerate ??
4- filter and rinse residuals with deionized water ? (Vacuum is necessary ?)

Tap water is fine.

5- precipitate gold using Sodium metabisulfite (is that right ?)
6- how to be sure all gold is precipitated? (Stannous test?)
7- keep solids (mud) by removing the liquid

Before drying it, it would be good to wash the powder/mud. No need to dry it first.

8- dry on a hot plate (by adding alcohol ?)

No alcohol. Just dry the washed powder.

9- melt and borax for a shiny color

You only need enough borax to glaze the dish before you put your gold in it to melt it.

Dave

 

[Joe cocker]

Thanks Dave !
How do you clean the mud before drying it ? And how do you know that all gold is dissolve into HCl ? (Is it linked to HCl quantity and time ?)
Thanks

 

[Joe cocker]

Hi
I don’t know if you can do that (because of properties) : do you know if there is a section dealing with AuSn refining in Hoke’s book ?
Or if I am following the process I describe above , I have great chance of success ?

 

[Yggdrasil]

Thanks Dave !
How do you clean the mud before drying it ? And how do you know that all gold is dissolve into HCl ? (Is it linked to HCl quantity and time ?)
Thanks

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.

 

[Joe cocker]

Thanks a lot !! I am quite ready to try something but what about the quantity ?
For example for 100 g of AuSn (80 / 20), how many HCl shall I add and then how many SMB to precipitate ?

Thanks a lot

 

[Yggdrasil]

Many is for things you can count and much is for things like flour, sugar and other.
Cover what you want to dissolve in HCl and heat a bit. When the reactions seem to stop add more heat or HCl.
If it then stops pour of the liquid and add more HCl.
And so on.

Edit to add.
There is no need to add SMB because what is left is the gold, it will not dissolve.

Do you actually read and understand the advice you are given?

Maybe you should study more?

 

[Joe cocker]

you are right ! I misunderstood something!!
I read and looked videos where it is said that gold was dissolve and then that you need SMB to precipitate !
Maybe it was with another alloy and/or acid ??
It is then easier !

 

[Joe cocker]

(And in that post, Dave told me that my described process was fine …)
I am lost .. need to study more !

 

[butcher]

Joe, if your lost, and do not understand the answers before you even begin on your journey, you will surely be lost after getting started and when things do not work the way you expect them to. then asking questions to get out of that problem, may not be as helpful as you expect if you do not understand the language or the instructions or what even to expect.

Your gold will still be there when you are ready and have spent some time to gain an understanding of the process you plan on exploring, you will still run into problems or things will happen with the chemistry that you will not understand, but with study, you will have enough understanding to work your way through the problems and find yourself out of the wilderness, and if you do need help you will understand the answers.

I have been studying and doing this for many years now, and yet I still need more study.
I learn something new or gain a better understanding almost every day.
Gaining a little understanding is like planting a seed, with that seed you planted, your skills grow tremendously, with fertilization of study, and little water of practice, you plant your skills in firm ground, and that seed flourishes and grows large.

Asking a question half understanding and you rush out and toss that seed out in poor soil without understanding what it needs to flourish or knowing how to care for it, you may not be very successful getting your seeds of gold to grow.

I can study this my whole life and only learn a very small portion of what all there is to learn.

 

[Joe cocker]

Hello butcher! I understand the wording but information I am receiving are not going in the same way …
I just need to know if HCl 33% will dissolve the gold in AuSn (80/20) or the Tin …
Thanks again for your help

 

[manorman]

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

 

[manorman]

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

 

[Joe cocker]

Thanks a lot !!