Mixed foils from plating wire

Dear All,

Just to share something what i have done recently , After dissolving scrap jewelry plating wire in diluted nitric acid washed and was left with some mixed gold and white foils.

1)I heated those foils in a steel frying pan until hot red.
2)wash the foils in HCl
3)put those foils in AR and heated to about 120C for about 5 hour with a watch glass covered.(After 5 Hr, Only the gold dissolved but not the white foils)
4)filter out the let over foils and precipitate the gold as usual.

On the second day i decided to melt the new batch of mixed gold and white foils into a button, Those foils are very difficult to melt and only melt at very high temperature. After melting for a long time i got a shiny silver grey button weight 1.2g.

1)I try to dissolve the button in hot AR again but there is no reaction at all even with hot AR the button react only a few tiny bubble at a time.

2)I dissolved the button with 10grams of silver metal to make it an alloys.(Even with the 10g of the silver melted together i still can't get the melting point that i am able to pour shot.)

3)I dissolved the alloy button in 50/50 nitric with no excess just enough, After everything dissolved it left with some gold powder, tiny bits of fine black powder and full of grey powder.(Picture attached)

4) I let it some time to cool down intend to siphon off the silver nitrate but when the solution cool down, The silver has comes down as nice crystal, I added in some water and all the crystal dissolved.

5)I siphon the silver nitrate solution to another beaker and give the residue a nice wash with lot of hot water and combine the wash water to the silver nitrate solution.

6)I added in HCl to remove the silver and filter off the silver chloride and was left with a yellow solution.

7)Tested the solution with stannous Cl and it shows a yellow stain.

8)I slowly add zinc dust to the solution until the solution turns white clear in color, I was left with some finely black powder. I then let the powder settle well(about 10min) then siphon off the solution and washed then dry it in the same beaker with a hot plate. Then finally a nitric acid wash to the powder and again wash and dry.

9)I combine the finely black powder with the previous left over mix powder from the alloy button from nitric wash together in the same beaker.

10)Add in 4HCl to 1 Nitric and heated to 120C with watch glass covered for 2hours with slow increase of Nitric. After the Ar bath all color of the powder dissolved except the grey powder(Suspect Rhodium).

11) Evaporate it, then add some water, precipitate the gold out and test it with stannous Cl and it shows a result that i never seen before. I suspect the solution now contain platinum but i did not precipitated it as i think there should be very little so i save the solution in a bottle.(Stannous Test picture attached).

12)No water to do any refining :lol: :lol: :lol: Tap water here can't be use, Got to wait for rain.

So far i am happy of the result that i have done and Special thanks to Mr Butcher and Mr Harold the man that i respect :lol: :lol: :lol: They has nothing to earn and they has no secret and help me throughout the process. In this forums there are more of this kind of person i did not mention here and i believe this is the type of members that keep the forum going :lol: Of course i did not take advantage by only asking how to do it, I have read and done some research and when really i had bump into a wall then i asked in a polite manner.


I have re-read Hoke's and realise that on
Pg. 119 second Paragraph, It says a maximum temp of 140C-150C to evaporate is adviced?
Pg. 141 If i don't understand wrongly we can do quartation for platinum by using sulfuric?

Also if anyone here care to share how to put rhodium into solution and re-precipitate it?


Regs.......
Franciz

Francis,

Rhodium can be made soluble by several techniques including:

1. Bisulphate fusion.

2. Concentrated sulfuric acid at elevated temperature.

3. Chlorination of Rh at 700C in a tube furnace with dry chlorine gas.

If you click on the above links, you can see the posts that have been made on the forum on the subject.

There are other methods for dissolving Rh, but most are not covered here on the forum.

You can find the stannous chloride test procedure for Rhodium in the Guided Tour --> General Reactions list in order to confirm you have Rh, which I strongly suspect you do.

Steve

lazersteve said:

Francis,

Rhodium can be made soluble by several techniques including:

1. Bisulphate fusion.

2. Concentrated sulfuric acid at elevated temperature.

3. Chlorination of Rh at 700C in a tube furnace with dry chlorine gas.

If you click on the above links, you can see the posts that have been made on the forum on the subject.

There are other methods for dissolving Rh, but most are not covered here on the forum.

You can find the stannous chloride test procedure for Rhodium in the Guided Tour --> General Reactions list in order to confirm you have Rh, which I strongly suspect you do.

Steve

Click to expand...

Hello Steve, How are you? Thank you for your reply.

Butcher has told me to did a search on your Stannous chloride test too :lol:
I am going to try it today if it rain...Lol...
I will update the result i got...

Best Regs...
Franciz

Franciz if you have more of these foils to refine I'd be tempted to use a weak cold AR solution on them as Hoke suggests to remove gold from platinum and not melt them, hopefully you will remove all the gold and only a little of the rhodium, the other thought would be to use sulphuric to dissolve the rhodium leaving the gold behind, whichever method you use test the solutions for values after precipitation. I certainly wouldn't melt the foils together again, incineration is always a good process but then I'd try either of the methods outlined above if do have more to refine, rhodium isn't keen to dissolve as you have found but it will if it's very thin or in powder form so it's difficult to get complete results which is why I only recover PGMs and don't try to refine them, I leave that to the experts such as Lou and Steve.

nickvc said:

Franciz if you have more of these foils to refine I'd be tempted to use a weak cold AR solution on them as Hoke suggests to remove gold from platinum and not melt them, hopefully you will remove all the gold and only a little of the rhodium, the other thought would be to use sulphuric to dissolve the rhodium leaving the gold behind, whichever method you use test the solutions for values after precipitation. I certainly wouldn't melt the foils together again, incineration is always a good process but then I'd try either of the methods outlined above if do have more to refine, rhodium isn't keen to dissolve as you have found but it will if it's very thin or in powder form so it's difficult to get complete results which is why I only recover PGMs and don't try to refine them, I leave that to the experts such as Lou and Steve.

Click to expand...

Thanks for your reply Nickvc :lol:

Yes, I have more of this plating wire not the foils(Before nitric wash) in fact i got this wire by been forced to buy it as if i don't buy this wire lots the seller will not sell me their gold wire but i got it at very low price( A little bit extra from scrap copper value)

I agree with your thinking using hoke method for not melting them together and use weak AR to remove the gold first but in my personal experience it would be very difficult to wash the leftover undissolve foils and even if i can give it a nice wash there would be lot of water to deal with.( I found out that gold precipitate more smoothly, Easy and complete in more concentrate solution rather than very dilute solution)

I may be totally wrong in my thinking but i make sure i don't lose any value in every step i have done, After washing i check my solution for PMs if Stannous show any i will precipitate it with zinc immediately if the solution is too dilute, Wash then save any powder thats fall out and keep it for next batch.

To be honest, I don't have much experience on PGMs especially rhodium and this is not the type of material that i will buy :lol:
I am not really into this refining business for PGMs nor i must master on how to refine it but since there are so many experience refiner here who is willing to share their experience i would like to gain knowledge, Learn and experience how to do it and i am just trying :lol: :lol: :lol: So if one day i came across this type of material i will dare to buy it...Hehe...

PS: I may be wrong in my way of refining this type of material but i found out that this is the most easiest and simple to understand method after trying few other method.

Franciz

Finally i got some rain today and able to save some enough water for my refining,

1) I have combine the precipitated gold powder from last time to the left over powder( weight 2.8g)

2) Boil in hot Ar and precipitate the gold as usual

3) Melt the gold into a small tiny button weight 0.7g( when i took off the flame the button form a hole in the center of the button but it has a very nice shiny yellow, Issit normal for pure gold)

3)Stannous Cl test show positive for Pt in the solution.

4)filter the left over grey powder, Dried and weight 1.8g

5)Set the Pt solution aside as i think it has too little to precipitate

6) Tommorrow i will try to dissolve the grey powder by using Steves method ''sulfuric Acid'' and will post the result i get...

Franciz

Franciz,
nice work, the button of gold looks pure,
I am not suggesting a process but was thought I would just post some thoughts for discussion.

This post is for discussion only, and should not be performed without proper knowledge and an understanding of all of the safety precautions, and safe lab practices.

Concentrated sulfuric acid (hot acid is stronger), concentrated sulfuric needs special precautions, this solution can cripple a man for life, if handled improperly, special attention to proper personal protective gear (full face shield, full arm and hand gloves, aprons rubber boots with tops sealed so acid would not fill the boot, and so on, precautions to prevent breaking vessels spills, dropping of containers and so on, fume control, (any accident with these processes can be crippling).

Special procedures with the use of these acids must be followed, with the concentrated sulfuric acid (such as never pour water into a concentrated acid where it explosively forms acid steam splashing concentrated acid all over you), concentrated acid is always diluted by pouring it slowly into water.


Concentrated sulfuric acid with a small amount of HNO3 5% of solution heated till SO2 fumes leave solution will dissolve gold silver and rhodium, this solution if carefully diluted by cooling and slowly pouring into water would precipitate gold silver and any rhodium powders that may not have dissolved,

2 Au + 15 H2SO4 + 3 HNO3 --> 2Au(HSO4)3 + 3NOSO4H + 6H2SO4:H2O
(Not sure this formula is balanced), the Idea here is the gold is a persulfate in solution.

This would also be the case in a similar reaction like a sodium bisulfate (NaHSO4) fusion with the powdered materials of gold, silver, rhodium, where the metal powders would form dissolved salts of metals in the fusion at around 500 degrees, as the bisulfate forms a molten salt with the gold silver and rhodium, the bisulfate acts just like the concentrated hot sulfuric acid in this reaction, when this salt fusion is diluted the dissolved gold and silver would precipitate, and the rhodium would stay soluble as a rhodium sulfate solution.


The reason gold dissolves into this hot concentrated sulfuric acid is similar to how gold will dissolve in a concentrated sulfuric cell at the anode where persulfate is generated, but gold will not stay in the solution very well after the gold ions leave the close proximity of the anode where persulfate is generated and moves towards the cathode the gold falls to bottom of the cell or is precipitated as sulfuric solution is diluted when cleaning the cell (silver sulfate is not very soluble), (rhodium sulfate would be soluble).


So here we see three methods doing very similar things, the method used by most the forum members and considered safest (but not safe) is the concentrated sulfuric cell, but also what form or alloy the materials are in would also dictate how well they would work with any of these processes, (powders or large pieces of alloy may need pretreatment or change the form of the metals.

With the silver cell would need an electrical contact with the positive lead of the power supply, if the material was plated copper wired the coating (valuable metal) could be stripped, but if the material was a solid bar it would take a long time or possibly passivate depending on metals involved conditions of the alloy anode.

butcher said:

Franciz,
nice work, the button of gold looks pure,
I am not suggesting a process but was thought I would just post some thoughts for discussion.

This post is for discussion only, and should not be performed without proper knowledge and an understanding of all of the safety precautions, and safe lab practices.

Concentrated sulfuric acid (hot acid is stronger), concentrated sulfuric needs special precautions, this solution can cripple a man for life, if handled improperly, special attention to proper personal protective gear (full face shield, full arm and hand gloves, aprons rubber boots with tops sealed so acid would not fill the boot, and so on, precautions to prevent breaking vessels spills, dropping of containers and so on, fume control, (any accident with these processes can be crippling).

Special procedures with the use of these acids must be followed, with the concentrated sulfuric acid (such as never pour water into a concentrated acid where it explosively forms acid steam splashing concentrated acid all over you), concentrated acid is always diluted by pouring it slowly into water.


Concentrated sulfuric acid with a small amount of HNO3 5% of solution heated till SO2 fumes leave solution will dissolve gold silver and rhodium, this solution if carefully diluted by cooling and slowly pouring into water would precipitate gold silver and any rhodium powders that may not have dissolved,

2 Au + 15 H2SO4 + 3 HNO3 --> 2Au(HSO4)3 + 3NOSO4H + 6H2SO4:H2O
(Not sure this formula is balanced), the Idea here is the gold is a persulfate in solution.

This would also be the case in a similar reaction like a sodium bisulfate (NaHSO4) fusion with the powdered materials of gold, silver, rhodium, where the metal powders would form dissolved salts of metals in the fusion at around 500 degrees, as the bisulfate forms a molten salt with the gold silver and rhodium, the bisulfate acts just like the concentrated hot sulfuric acid in this reaction, when this salt fusion is diluted the dissolved gold and silver would precipitate, and the rhodium would stay soluble as a rhodium sulfate solution.


The reason gold dissolves into this hot concentrated sulfuric acid is similar to how gold will dissolve in a concentrated sulfuric cell at the anode where persulfate is generated, but gold will not stay in the solution very well after the gold ions leave the close proximity of the anode where persulfate is generated and moves towards the cathode the gold falls to bottom of the cell or is precipitated as sulfuric solution is diluted when cleaning the cell (silver sulfate is not very soluble), (rhodium sulfate would be soluble).


So here we see three methods doing very similar things, the method used by most the forum members and considered safest (but not safe) is the concentrated sulfuric cell, but also what form or alloy the materials are in would also dictate how well they would work with any of these processes, (powders or large pieces of alloy may need pretreatment or change the form of the metals.

With the silver cell would need an electrical contact with the positive lead of the power supply, if the material was plated copper wired the coating (valuable metal) could be stripped, but if the material was a solid bar it would take a long time or possibly passivate depending on metals involved conditions of the alloy anode.

Click to expand...

Butcher,

Is there a way to melt the gold into a button without a hole?

I will not comment on the Rh works i have done today as i am get an unexpected result, I am sending a PM to you and Steves to seek help........

I will update any result i got after i have work out....

Franciz

That hole in your gold is saying it is very pure, you want to have that hole in your gold when you melt it.
It shows you are doing the right things :lol:

Dear All,

After trying everything and try to look through the forum i found that i have about the same problem as this------>http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=15326

Franciz,
some quick search on the oxide:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=15326



Rhodium(III) Oxide
http://www.google.com/#sclient=psy-ab&hl=en&rlz=1R2RNQN_enUS457&q=Rh2O3&oq=Rh2O3&gs_l=serp.12..0j0i30l6.5485.18703.1.27813.2.2.0.0.0.0.2157.2329.0j1j9-1.2.0.les%3B..0.0...1c.1.x5RgxUsJ8f0&psj=1&bav=on.2,or.r_gc.r_pw.&fp=9f906da1c2ca652a&biw=1024&bih=539


http://www.americanelements.com/rhoxp.html

Hi butcher,

What you say about concentrated sulfuric acid and it's dangers, is right. However, your statements about dissolution of precious metals in concentrated sulfuric acid or in molten sodium hydrogensulfate, in my opinion deserve some comments.

"Concentrated sulfuric acid with a small amount of HNO3 5% of solution heated till SO2 fumes leave solution will dissolve gold silver and rhodium, this solution if carefully diluted by cooling and slowly pouring into water would precipitate gold silver and any rhodium powders that may not have dissolved.."

I doubt, that such a mixture dissolves any gold. At least, in my hands it never did, leaving gold behind, after strong heating, until evolution of heavy fumes of SO₃, sulfur trioxide, (not SO₂, sulfur dioxide, which is a reducing agent), undissolved, as a nicely golden-brown coloured, spongy material. However, it may well be, that silver and rhodium, at least partly, are dissolved, forming a more or less coloured (depending on it's rhodium-content) solution, deposing some solid, only slightly water-soluble silver sulfate on dilution.

"This would also be the case in a similar reaction like a sodium bisulfate (NaHSO₄) fusion with the powdered materials of gold, silver, rhodium, where the metal powders would form dissolved salts of metals in the fusion at around 500 degrees, as the bisulfate forms a molten salt with the gold silver and rhodium, the bisulfate acts just like the concentrated hot sulfuric acid in this reaction, when this salt fusion is diluted the dissolved gold and silver would precipitate, and the rhodium would stay soluble as a rhodium sulfate solution."

Again, neither molten potassium hydrogensulfate, KHSO₄, nor molten potassium disulfate (potassium pyrosulfate), K₂S₂O₇ dissolved any gold in my hands. Potassium disulfate can be regarded as dehydrated potassium hydrogensulfate: 2 KHSO₄ <=> K₂S₂O₇ + H₂O.

However, very finely ground mixtures of K₂S₂O₇ and NaCl, intimately mixed together with very fine metal-powder, were able to dissolve significant amounts (several grams) of platinum-group metals on melting, as soluble chloro-complexes. Gold was attacked, too, but never found in significant quantities (only milligrams) in solution, after working up the cool, now solid melt with diluted HCl.