# HNO3-HF



## Fijcho (May 14, 2016)

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 (May 14, 2016)

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

Dave


----------



## Topher_osAUrus (May 14, 2016)

FrugalRefiner said:


> 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 (May 14, 2016)

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 (May 14, 2016)

mls26cwru said:


> 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 (May 14, 2016)

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 (May 14, 2016)

FrugalRefiner said:


> 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 (May 14, 2016)

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 (May 14, 2016)

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 (May 15, 2016)

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 (May 15, 2016)

Thanks you all!


----------



## Lou (May 15, 2016)

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


----------

