How does gold react with chlorine?

[OMG]

In wiki under gold(III) chloride it says it can be made by direct chlorination at high temperatures, but on the same page it says that it begins to decompose above 160*C to form gold(I) chloride and chlorine. So does that mean that chlorine + gold at a temperature below 160*C will form gold(III) chloride?
That seems like a pretty low temperature.

 

[OMG]

Gold(III) bromide forms at 140"C, and chlorine is more reactive so does gold (III) chloride form at a lower temp that 140*C?

 

[Irons]

AC attacks at ambient and is a solution of Chlorine in acid. I think that refers to dry Chlorine.

 

[OMG]

I've read that iron and copper don't react with chlorine at that low of a temperature, so could you just use chlorine gas at say 140*C to convert only the gold to AuCl3. leaving the iron and copper behind as they are, then wash out the AuCl3 with water?
Seems like its too easy to do. There must be some complications.
I could see that the AuCl3 would build up on the surface of the gold, protecting it from further attack by Cl2, so I was thinking that you could put everything in a pressure cooker, raise the pressure to 5 atm so water won't boil until 150*C and then bubble chlorine though it (or generate the Cl2 in the water itself). That way when the AuCl3 is created, it will be carried away by the liquid exposing more Au to attack.
Then you won't be dealing with HCl at all, and the lower metals stay as metals. (the heat alone might not prevent Cl2 + H2O -> HCl + HOCl, but you could add some NaOCl to prevent that reaction.) In fact, you could bubble in some HCl gas into a NaOCl + water mixture to generate the chlorine right in the liquid.
Hmm. I think I'm going to buy a pressure cooker.

 

[Lou]

Ah, very convenient for you that I have actually done the chlorination of Au, Pt, Pd, and others quite a bit! FYI, wet chlorine will attack pretty much every metal, Cu and Fe do not react with dry chlorine. I can tell you how to most efficiently make chlorine and dry it.

Yes, it's a good way to purify gold and the PGMs, and good for separation. I'd like to say more but I broke my index finger earlier tonight and typing isn't a whole lot of fun with a splint! I'm correcting my peck typing every other word.



Lou

 

[Noxx]

Ouch... I hope it's not so bad.

 

[Lou]

Top knuckle is completely broke. I'd like to say I did it doing something manly like diving to the ground from a runaway aqua regia dissolution and being spattered with boiling acid but rather it was me getting a door slammed on it accidentally. Yet here I am still trying to contribute to the good of the forum Now that's manly! Heheheh, I love sarcasm!

 

[OMG]

Ouch! Well I hope for everyones sake you heal quickly.
But seriously, I'd definitely be interested in hearing the pros and cons and setup required and all that stuff.
I was just thinking of using NaOCl and HCl to generate chlorine, but if dry chlorine is a better option, I would think you could probably generate it inside of conc sulfuric somehow which would dry it out before it escapes. Am I on the right track?
So "wet" chlorine attacks iron and copper... I guess that means it attacks their oxides too?
Maybe if I ask Y/N questions it will be easier for you to answer if you feel up to it. This is a new avenue for me so I still have a lot to research.

1) Would this be a worthwhile method to look into for concentrating (powdered) black sand concentrates? ie a) are there a lot of obstacles to achieving reasonable results? (or is it generally straight forward once you get it down)
2) Does dry chlorine attack silver?
3) Does dry chlorine attack mercury?
4) Would "wet" chlorine attack the iron oxides as quickly as it would attack the gold at the appropriate temperature? (I'm thinking that if it attacks the iron oxides at a much slower rate that the gold and/or platinum, then it would still be very useful.)
5) If you bubbled "dry" chlorine through super saturated NaCl and water, would it get "wet"?
6) how about the same situation but through super saturated CaCl2 and water?

bah. I've got too many questions. I'll research more.

 

[OMG]

Some of the answers I've found:
Below 121*C: iron, copper, steel, lead, nickel, platinum, silver, and tantalum are resistant to dry chlorine.
At "ordinary" temperatures dry chlorine reacts with: aluminum, arsenic, gold, mercury, selenium, tellurium, and tin.
Titanium reacts violently with dry chlorine.
The metals are resistant, but only to certain temperatures, after which they will react.

"wet" chlorine is corrosive because of the HCl and HOCl formed with the reaction of the chlorine with water vapor/moisture.

 

[OMG]

If you are up to it Lou, I'd like to hear how to efficiently make dry chlorine.

Also, Are there solvents for gold chloride that aren't affected by chlorine and will keep the chlorine dry?

 

[Lou]

It is simple to make.

Forgive me if I do not myself answer your question, for it has been answered to my satisfaction by my friend Len, an Aussie physicist and amateur chemist. You will find all that you need to know, and perhaps more from reading his post here:

http://www.sciencemadness.org/talk/viewthread.php?tid=9713

If that is not sufficient from a hands on perspective, I will be glad to tell you how I do it, and how to implement chlorine safely in your processes.


Louis

 

[OMG]

That's great. Thanks. Sounds pretty easy. I'll look for trichlor next time I'm in town. I wonder why people aren't using just chlorine to dissolve there gold. It seems a lot easier and a more pure way to do it.