Precipitation of fine yellowbright gold powder from acquareg

[antonio]

Good afternoon to everybody,
My name is Antonio and I'm a new member of this forum.
I have a question regarding the precipitation of gold from acqua regia solution.
I know there are several reducing agents that you can add to acqua regia solution for the precipitation of gold powder:
- hydrogen peroxyde
- SMB
- Formaldheide
- ossalic acid
- etc.
However, all of these agents don't allow a formation of a fine yellow gold powder. For my application, I need to have a fine yellow bright gold powder with dimension from 1 to 200 micrometers.
I have read a recent work in the journal "Science" where a group of scientist obtained a precipitation of nanometric yellow gold powder (200-500 nm) from acqua regia by adding to the solution polyvinilpirrolidone (like capping agent) and poliethilene glicol like nucleation agent. I have tried to repeat these experiment and I obtained a gold powder of 0,7 micrometers.
Are there any chemical method for obtain from a solution of acqua regia a micrometric yellow bright gold particles?
Thanks for your time.
regards

 

[Palladium]

Wow! That is so much above my pay grade. Lou would probably be the best man to answer a question like that. Him or that other real smart chemist fellow, i can't think of his name right off hand. I will send Lou a PM with a link to this thread.

 

[Lou]

My experience was with gold clusters that were 50-150 nm in size and were made via citrate and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) to control nucleation.

Given your application, you might want to consider argon atomization. 1-200 um is coarse stuff insofar as powders go. I wouldn't call it "nano". We supply a company locally that makes atomizates from precious metals. The powder is indeed bright yellow.

Use of peroxide, sulfite, hydroquinone or other stronger reducing agents (can't believe I'm saying that in the same sentence as peroxide) will not work because they are too fast and will often give spongy precipitates. You can try diluting the solution down to say, 10 g Au(III) / L and use a dilute solution of hydrazine sulfate and do it in the cold.

 

[kane333]

Wow! That is so much above my pay grade. Lou would probably be the best man to answer a question like that. Him or that other real smart chemist fellow, i can't think of his name right off hand. I will send Lou a PM with a link to this thread.

4metals?

 

[Westerngs]

I would try oxalic acid, both solutions cold, and let them sit a few days.

Beautiful gold precipitates, very finely divided, but I have never actually determined the particle size.

 

[Palladium]

Wow! That is so much above my pay grade. Lou would probably be the best man to answer a question like that. Him or that other real smart chemist fellow, i can't think of his name right off hand. I will send Lou a PM with a link to this thread.

4metals?

I believe 4metals specialty, if I'm not mistaken, is analytical chemistry. Not sure about Lou's but i'm pretty sure it covers a different field of chemistry that better suits the question at hand. The other fellow i was talking about is like Lou with chemistry, but don't post much anymore and I've heard them talk that secret Latin chemist talk or what ever language it is they speak. All i know is you don't have them type of intellectual conservations with Lou without knowing what your talking about. I just wish Lou would do that thread on nucleation's?

 

[steyr223]

Maybe lino

 

[Lou]

Freechemist.