[Hunter2]

I  think for this purpose you don't need so pure compound. The removal of excess KCl is in my opinion not necessary.

[kailee33]

There is two routes I can take

The classic route in making a gold sulpho-resinate (Gold Salt + Sulphured resin)

Or the more modern route gold aryl mercaptide (Gold Salt + ethyl acetate + dimethylbenzenethiols + Polymer)

But I would prefer to work with more natural products

[kailee33]

I  think for this purpose you don't need so pure compound. The removal of excess KCl is in my opinion not necessary.

Agreed, I would just like to minimise, hence why I was initially looking for approximate weights to use in the reaction, to keep excess potassium quite low

[kailee33]

So Stoichiometry calculation for 10g of KAuCl4 would require 8.99g of HAuCl4 + 1.97g of KCL so a ratio of 21.9% KCL.

To give minimal excess this could be 30%??

[kailee33]

Might as well tie the thread up with the complete formula, hopefully I've got it right

Au + 3HNO3 + 3HCl + KCl = KAuCl4 + 3NO2 + 3H2O

[Borek]

Au + 3HNO3 + 3HCl + KCl = KAuCl4 + 3NO2 + 3H2O

Yes, this is correctly balanced, but slightly unrealistic. Reactions of the oxidation by concentrated nitric acid (which is not exactly a case here, but close) typically go through more than one pathway and produce more than one gaseous product. Details can depend on several others factor (like temperature, purity and concentration of the reagents used) - but the stoichiometry observed never exactly follows single reaction equation.

So yes, this is a good starting point, but what it really it tells is "if you use less reagents than this equation suggests you will fail". Finding correct excess is more or less guesswork and requires some trial and error experiments. I would start with something like 50%-100% excess of both acids. Plenty of chlorides in the solution (from HCl), so excess of KCl can be smaller - say 10% (doesn't mean it will be OK, that's just where I would start experimenting).

[Hunter2]

I learned 40 years ago that Aqua Regia react in this way

3 HCl + HNO3 => NOCl + 2 H2O + 2 Cl* ( nasc)

Nitrosyl chloride NOCl and nascent Chlorine is developed.

There active chlorine radicals have the capability to dissolve the gold.

Au + 3 Cl* => AuCl3 => and this with more HCl gives H[AuCl4]

Also found on the german Wikipedia side

https://de.wikipedia.org/wiki/K%C3%B6nigswasser

The english one don't mentioned it???

https://en.wikipedia.org/wiki/Aqua_regia



Is there some new knowledge or the side is outdated?

[Borek]

I learned 40 years ago that Aqua Regia react in this way

3 HCl + HNO3 => NOCl + 2 H2O + 2 Cl* ( nasc)

Nitrosyl chloride NOCl and nascent Chlorine is developed.

Definitely mechanism of Au dissolution by aqua regia, is not just a simple HNO₃ oxidation. Feel free to develop an overall reaction from that. It won't change the situation - overall reaction only partially reflects the reality, nitrosyl chloride will most likely react further and decompose.

I didn't wrote

Reactions of the oxidation by concentrated nitric acid (which is not exactly a case here, but close)

without a reason.

[kailee33]

Au + 3HNO3 + 3HCl + KCl = KAuCl4 + 3NO2 + 3H2O

Yes, this is correctly balanced, but slightly unrealistic. Reactions of the oxidation by concentrated nitric acid (which is not exactly a case here, but close) typically go through more than one pathway and produce more than one gaseous product. Details can depend on several others factor (like temperature, purity and concentration of the reagents used) - but the stoichiometry observed never exactly follows single reaction equation.

So yes, this is a good starting point, but what it really it tells is "if you use less reagents than this equation suggests you will fail". Finding correct excess is more or less guesswork and requires some trial and error experiments. I would start with something like 50%-100% excess of both acids. Plenty of chlorides in the solution (from HCl), so excess of KCl can be smaller - say 10% (doesn't mean it will be OK, that's just where I would start experimenting).

Thank you Borek, the excess acid I'm used to, I have dissolved gold in aqua regia many times. Normally I start with excess HCL & calculated Nitric, when reaction slows/stops, add a little more nitric. Repeat until all gold has dissolved. Excess acid can easily be boiled off, then a few evaporation of water, leaving fairly pure HAuCl4

I just got a little worried about the quantity of KCl as I knew it wouldn't be as easy removing excess and wanted to keep the KAuCl4 of a fairly high purity. But I can do more practical experiments, keep notes on exact weights to find a good balance

[kailee33]

I learned 40 years ago that Aqua Regia react in this way

3 HCl + HNO3 => NOCl + 2 H2O + 2 Cl* ( nasc)

Nitrosyl chloride NOCl and nascent Chlorine is developed.

There active chlorine radicals have the capability to dissolve the gold.

Au + 3 Cl* => AuCl3 => and this with more HCl gives H[AuCl4]

Also found on the german Wikipedia side

https://de.wikipedia.org/wiki/K%C3%B6nigswasser

The english one don't mentioned it???

https://en.wikipedia.org/wiki/Aqua_regia



Is there some new knowledge or the side is outdated?

Thank you hunter, I will use this instead..

[kailee33]

I learned 40 years ago that Aqua Regia react in this way

3 HCl + HNO3 => NOCl + 2 H2O + 2 Cl* ( nasc)

Nitrosyl chloride NOCl and nascent Chlorine is developed.

Definitely mechanism of Au dissolution by aqua regia, is not just a simple HNO₃ oxidation. Feel free to develop an overall reaction from that. It won't change the situation - overall reaction only partially reflects the reality, nitrosyl chloride will most likely react further and decompose.

I didn't wrote

Reactions of the oxidation by concentrated nitric acid (which is not exactly a case here, but close)

without a reason.

Agreed, for my purposes I am only really interested in one product since this is for more practical than theoretical purposes. But you have both been very kind in helping me understand the process in a deeper level, so thank you both. I have many more experiments ahead