[kailee33]

Hi all, been searching the Internet for a while in creating K(AuCl4). The only real reference I could find was quite vague, 'Dissolve elemental gold in aqua regis in the presence of KCL. Looking for some input if possible?

[kailee33]

Okay so I found this which looks fairly straight forward, I guess my next question is to work out the percentage weight of each chemical required to produce the product without excess of either. (In reality I don't mind a small excess of potassium chloride, as long as its minimal).

As shown in Figures 8 and 6 and 7, the prior art provides a method of preparing potassium chloroaurate which is similar to the above-described prior art method for preparing sodium chloroaurate. The prior art method for preparing potassium chloroaurate is to treat the aqueous chloroauric acid solution with potassium chloride (KCl) or potassium carbonate (K 2 CO 3 ) at 100 ° C, and then evaporate, cool, crystallize and dry. The orange potassium chloroaurate crystal was obtained by treatment.

HAuCl 4 + KCl → KAuCl 4 + HCl (Formula 6)

2 HAuCl 4 +K 2 CO 3 →2 KAuCl 4 +H 2 O+CO 2 (Formula 7)

[Hunter2]

I would choose KCl. If you use K2CO3 the solution could be at drag in to alcaline and gold oxide would precipitate. pH control is not easy and if you consumed all H+ then it's get dangerous to get to alcaline.
With KCl you can boil the solution and HCl evaporates.

[Borek]

my next question is to work out the percentage weight of each chemical required to produce the product without excess of either

Not a good idea actually. Assuming just stoichiometric synthesis almost never works. In this case at best using stoichiometric amounts will make the dissolution slow at the end, but more likely there will be gaseous byproducts that will consume acids involved not letting them react with the gold itself.

You want excess of other reagents, to make sure you used and precipitated all gold, which is most expensive.

[kailee33]

I would choose KCl. If you use K2CO3 the solution could be at drag in to alcaline and gold oxide would precipitate. pH control is not easy and if you consumed all H+ then it's get dangerous to get to alcaline.
With KCl you can boil the solution and HCl evaporates.

Thanks Hunter, yeah, I had went ahead and ordered some HCL, really because I saw it used in the first aqua regia method. I believe this was an older method as you can produce the required HCL from the KCL to form Aqua Regia

[kailee33]

my next question is to work out the percentage weight of each chemical required to produce the product without excess of either

Not a good idea actually. Assuming just stoichiometric synthesis almost never works. In this case at best using stoichiometric amounts will make the dissolution slow at the end, but more likely there will be gaseous byproducts that will consume acids involved not letting them react with the gold itself.

You want excess of other reagents, to make sure you used and precipitated all gold, which is most expensive.

Any suggestions on a good starting point for weights? Also, would there be any way to precipitate out the KCL if I just go with a large excess?

[Borek]

I believe this was an older method as you can produce the required HCL from the KCL to form Aqua Regia

I am starting to wonder if you should try this reaction, as it requires dealing with seriously dangerous reagents and apparently is way above your level of expertise.

[kailee33]

The dangerous part has already been done, the gold chloride has been made, I'm really just on the last step. I may not have the chemistry background but I do have a very technical background and research lots before anything practical. This particular step isn't very well documented hence the reason I have came here for some expert advice?

[kailee33]

So im now looking at solubility in diethyl ether, if im reading this correctly I can react the gold chloride with an excess of KCL. Then ether can be used to dissolve the KAuCl4 leaving the excess KCL as a solid which can be filtered off. Does this sound plausible?

[Hunter2]

What is the solubility of KAuCl4 in Diethylether. Do you have a number.
But I don't think  it's soluble. And if yes in water it would be more higher.
. .

[kailee33]

What is the solubility of KAuCl4 in Diethylether. Do you have a number.
But I don't think  it's soluble. And if yes in water it would be more higher.
. .

I couldn't find specifics on how soluble but did find the following

Potassium gold chloride

Description
Yellow crystalline powder. Potassium gold cyanide is used in photography and paints for Porcelain and Glass.

Synonyms and Related Terms
potassium aurichloride; potassium chloroaurate; gold potassium chloride

Physical and Chemical Properties
Soluble in water, ethanol, ether.

Composition   KAuCl4 - 2H2O


and KCL is described s practically insoluble in Diyethlether

[Hunter2]

The same I also can find, but without ether.
And again it's high soluble in water. You never will get it transferred into ether.

[kailee33]

Even if I dry it? I have successfully dried AuCl4 to powder it using a vacuum chamber and low heat?

[Hunter2]

There is no AuCl4. You have AuCl3 or better Au2Cl6. The other one is HAuCl4.This is existing as Trihydrate. HAuCl4 * 3 H2O. If you dry it decompose.
Drying and separation of two chemical is a different thing.
Check the solubilities of KCl and KAuCl4 and do fractional crystallisation in water.
PS For what you need the KAuCl4 by the way.

[kailee33]

Thank you very much for the help Hunter, I will read up on fractional crystallisation.

I use gold chloride on pottery. This is mixed with an organic binder & flux. But I find the shelf life is short, the gold seems to revert back to metallic Au after a couple of weeks. So I am looking at a more stable salt of gold for longer storage.