Gold nitrate

[goldsilverpro]

Lou,
This is mainly for you.

If you Google - gold nitrate - you will find it for sale (actually HAu(NO3)4). One of the applications is plating. I recently found this method on the internet for making it:

HAu(Cl)4 + 4AgNO3 = 4AgCl + HAu(NO3)4

I once toyed with the idea of using AgNO3 to drop the gold (along with the AgCl) from a very difficult hi-HNO3, lo-HCl AR solution. I just assumed the gold would drop because I knew of no gold nitrate compound. Evidently I was wrong.

Do you have any experience with this? Can you think of other ways to produce it?

 

[Lou]

Actually gold nitrate does exist. This is one I've never made, and this is a hip shot, I'd have to consult Cotton or the other Cotton.

This normally does not happen--gold (III) nitrate is transient in any sort of aqueous medium. I'd really have to think on how to prepare it dry; usual method is reaction with N2O5.

You recall that auric chloride is a Lewis Acid. So too is auric nitrate--they immediately complex an extra ion (in this case nitrate) and a proton. That's why it's acid gold chloride, because it's AuCl3 with an HCl, which serves to stabilize it. This is analogous to HAu(NO3)4 with HNO3 being the acid.


If you don't want to mess about with the silver nitrate method for forming acid gold nitrate, you will have to exploit another thermodynamic process.

Don't like silver? Then try it with lead (II) nitrate, or Hg2+2 (calomel precipitates). Lead chloride is pretty soluble at higher temps, so you'll have significant contamination unless it is done cold. If you don't like that, make an aqua regia using HBr or HI so that the resultant lead salt will be more insoluble; bear in mind that using HBr or HI brings its own problems, namely the tendency of nitric acid to oxidize the halide to its elemental state. Also recall that excess halide in solution will complex the lead.