HNO3-HF

[Fijcho]

Hi
I am new to this forum and have a chemical question.
Gold can be dissolved in a mixture of nitric and fluorhydric acids, kind of alternative aqua regia?
Thanks!

 

[FrugalRefiner]

Hydrofluoric acid (aka fluorhydric acid) is extraordinarily dangerous! I would far prefer nitric and hydrochloric acid.

Dave

 

[Topher_osAUrus]

Hydrofluoric acid (aka fluorhydric acid) is extraordinarily dangerous! I would far prefer nitric and hydrochloric acid.

Dave

Yeah, i don't think i would ever entertain the idea of using HF.

Something that a drop, can sneak up on you, unnoticed...then eat away the calcium in your bones so they just snap?

I would certainly pass on that, and stick to the other traditional (still dangerous but *nothing* on hydrofluoric) methods..

I like my bones though...they've never done me wrong yet in 30 years, so i don't want to push it 8)

 

[mls26cwru]

first, hydroflouric is much more dangerous than nitric, so it wouldn't be a 'better' alternative to begin with...

second, I don't think it will work, because in Aqua Regia, its a two part reaction where the nitric attacks the gold and forms an intermediate compound which the hydrochloric come next to react to form chloro-auric acid... the chlorine that hydrochloric provides is a key step in dissolving the gold.

third, if you don't know that HF is a more dangerous acid to use, then you really need to educate yourself on basic chemistry a whole lot more before even think about starting to refine.

 

[FrugalRefiner]

second, I don't think it will work, because in Aqua Regia, its a two part reaction where the nitric attacks the gold and forms an intermediate compound which the hydrochloric come next to react to form chloro-auric acid... the chlorine that hydrochloric provides is a key step in dissolving the gold.

I hate to pick nits, but as I understand it, the nitric acid in aqua regia oxidizes the gold (removes one or more electrons) which creates gold ions (Au³⁺). The nitric does not form any intermediate compound with the gold. The gold ions then combine with the chloride ions (Cl^-) from the hydrochloric acid to form chloroauric acid.

Dave

 

[Fijcho]

Hi fellows

I appreciate your concern about my health and the dangers of HF.
My interest is only academic, but not being trained in theoretical issues about chlorine versus fluorine, I ask your advice.
No plans to do any reaction with HF.
Does anyone have an idea about the possibility to dissolve gold in that mixture?
Thanks!

 

[mls26cwru]

I hate to pick nits, but as I understand it, the nitric acid in aqua regia oxidizes the gold (removes one or more electrons) which creates gold ions (Au³⁺). The nitric does not form any intermediate compound with the gold. The gold ions then combine with the chloride ions (Cl^-) from the hydrochloric acid to form chloroauric acid.

Dave

You are correct... I should have chosen my words a little more carefully... "nitric attacks the gold and forms an intermediate compound" should have said "nitric attacks the gold which puts it into an intermediate state". The nitric doesn't actually combine with the gold and I can see how that could have been misinterpreted with how I worded it. I am pretty sure compound is also the wrong term to use as well since it oxidizes the gold to Au3+ which would still be an element and not a compound.... i hope I have it right now

 

[jason_recliner]

Purely hypothetically then, my advice would be the same as to anyone contemplating the idea of:

- Owning a pet chimpanzee
- Modifying a Honda to look like a Corvette
- Slicing your birthday cake with a chainsaw
- Using an acid so nasty it makes nitric look like dishwashing detergent, when there are simple options.

Just because you can, doesn't mean you should.

 

[Topher_osAUrus]

If your goal is purely to gain knowledge or *academic* reasons. I think that most of the halogens on the periodic table can manhandle gold to some extent. I know ive read of iodine, bromine, chlorine... So fluorine may work too... But, i wouldn't even mess with the idea.

If its plausible, maybe one of our chemists here can hit us with some knowledge

 

[nickvc]

I believe you can use HF and hydrogen peroxide to dissolve gold but can't see many applications where that would be a process of choice, if it were me I'd avoid anything that needs HF and leave it to the professionals who have the right safety equipment to handle the dangers.

 

[Fijcho]

Thanks you all!

 

[Lou]

No, it doesn't work with peroxide or nitric.