If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
aqua regia--extract gold from?
any ideas on how to extract gold from aqua regia?
i assume just diluting it would work as would neutralizing it also. iwould assume that the gold would just pdrecipitate out thanks peter -- Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/ |
Ads |
#2
|
|||
|
|||
On Tue, 04 Nov 2003 19:15:59 -0800, in rec.crafts.jewelry ilaboo
wrote: any ideas on how to extract gold from aqua regia? i assume just diluting it would work as would neutralizing it also. iwould assume that the gold would just pdrecipitate out thanks peter Simple dilution doesn't do it, as the gold is now in the form of gold chloride, which is water soluable. What you have to do is a process called cementation, which, as you suggests, precipitates it out. It does it by replacing the gold ion in the chloride, with a baser and therefor more reactive metal. Like Iron, for example. If you simply add steel wool to the acid, it will slowly react, at first just using up remaing acid. Then after free acid is gone, the iron replaces the gold in the chloride, and the gold then deposits back out. eventually, once the process stops, the solution is one of iron chloride, and the gold is now plated loosely all over whatever remains of the steel wool, or as a sludge on the bottom It can be filtered, and after being very careful to remove all remaining traces of acids or chloride compounds, you can then remove the remaing steel wool by dissolving it in a straight acid like straight HCL, or better, sulphuric. The results will be decent, but probably not highly pure, as it's difficult to remove absolutely all the iron. Also, if you originally dissolved gold alloy that contained any platinum group metals or copper, these will also have precipitated out. The copper can be redissolved at the same time as the iron, if you choose the acid appropriately, but the platinum group metals will be difficult to seperate. Normally, one precipitates them first, with oxalic acid, before throwing down the gold. A cleaner and more selective precipitating agent is to use a solution of ferric sulphate. Since that dissolves, it doesn't leave metallic iron sitting around to contaminate the works, and it's a more effective precipitant as well, since the sulphate ion also acts on this, though I don't recall exactly how. In large refineries, the gold is usually precipitated out of the solution by bubbling hydrogen sulphide gas through the solution. This is not for the small operation however, since though tanks of H2S are cheap enough, the gas not only smells of rotton eggs, but is also highly toxic. You need a fume hood and appropriate scrubbers to use that method. Like the cementation method, the ferric sulphate will also throw down any platinum group metals present, so if they are there, you'd want to precipitate them first with oxalic acid. But the ferric sulphate does not affect the copper remaining in the solution. That stays there. So you get only the gold and platinum group metals in the precipitate. Hope that helps. Peter Rowe .. |
#4
|
|||
|
|||
In article , Peter W. Rowe
pwrowe@ixDOTnetcomDOTcom wrote: A cleaner and more selective precipitating agent is to use a solution of ferric sulphate. Peter,I think you mean ferrous sulphate (green vitriol), a reducing agent, like sodium bisulphite/metabisulphite. Ferric salts are oxidising agents, which is why ferric chloride is used to etch copper. I am always interested in your posts and have learnt a great deal from then in the last couple of years Thank you - G.H.Ireland -- igor _____________________________________________ Acorn RISC OS4 _____________________________________________ |
#5
|
|||
|
|||
On Thu, 06 Nov 2003 02:04:01 -0800, in rec.crafts.jewelry Mr G H Ireland
wrote: Peter,I think you mean ferrous sulphate (green vitriol), a reducing agent, like sodium bisulphite/metabisulphite. You're quite right. Ferrous it is. I should know better than to try and remember chemical names late in the evening... (grin) Peter |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Gold and all its variations for findings | Su/Cutworks | Beads | 24 | September 20th 04 03:27 PM |
Fusing "gold" leaf | Gordon Williamson | Glass | 2 | January 25th 04 01:25 AM |
What would happend... | m4816k | Jewelry | 4 | November 4th 03 03:52 AM |
How much 14K gold will a 1/4 ounce of 24K gold yield? | Jeff S. | Jewelry | 10 | October 28th 03 04:43 AM |
What does "salty" diamond mean? And 11k white gold? | AuroraeB | Jewelry | 1 | September 13th 03 05:22 PM |