AndersHoveland - 3-8-2011 at 13:27
When a mixture of concentrated hydrochloric acid (32%) is mixed with some sodium nitrate and heated, brown fumes begin to be given off. Someone in
another forum claimed that this mixture was capable of slowly dissolving gold.
It is known that there exists the following equilibrium in aqua regia:
HNO3 + (3)HCl <==> NOCl + (2)H2O + Cl2
In a mixture of muriatic acid and sodium nitrate, perhaps there is also an equilibrium, although only very small?
(2)NaNO3 + (4)HCl <==> (2)NaCl + (2)H2O + Cl2 + NO2 + NO
Theoretically, if the reaction could be made much more acidic, the equilibrium would probably shift more to the right. The reaction would not really
be driven much towards the right until acid concentrations of around 70%, which is not possible for muriatic acid, since only so much HCl (which is a
gas in the pure form) can dissolve in water.
One would wonder whether the sodium nitrate in the concentrated muriatic acid solution could act as a catalyst, allowing some of the hydrochloric acid
to be oxidized by the air:
(4)HCl + O2 <==> + H2O + Cl2 ?
(since the oxides of nitrogen would react with oxygen to form nitric acid)
One would think that this reaction would have already been described in this forum, but a search did not reveal anything. Does anyone know what is
happening in this reaction?
It is known that mixtures of nitric oxide and nitrogen dioxide together can attack ammonium salts. Perhaps letting a little ammonium nitrate dissolved
in hydrochloric acid (32%conc) sit around for 24 hours will answer the question. If there is indeed any equilibrium, a portion of the ammonium nitrate
should react, with the net equation:
(3)NH4NO3 + (6)HCl --> (9)H2O + (3)N2 + (3)Cl2
will do experiment and let everyone know how it went. If there is no reaction, than it would strongly suggest that there is no chlorine or nitrogen
oxides in equilibrium.
(typically NCl3 will not form under strongly acidic conditions, but one should still be careful)
[Edited on 3-8-2011 by AndersHoveland]
Fleaker - 3-8-2011 at 19:38
This mixture does indeed dissolve gold, and does it effectively.
It will form nitroysl chloride which will give you chlorine and a slew of nitrogen oxides.
Arthur Dent - 4-8-2011 at 03:34
Gold salvagers/refiners affectionately call this mix "poor man's Aqua Regia" because nitric acid is usually more expensive and harder to get than
Sodium Nitrate (for many of us). It is most effective if heated, but you don't need to heat it throughout the reaction with the metal itself, just
pouring the really hot mixture over the gold parts is enough. It evolves quite a bit of the NO gases (angry orange cloud) 
The only advantage real Aqua Regia has is that you don't need to heat it to react with gold, which is probably a good thing because the thought of a
boiling mixture of HNO<sub>3</sub> and HCl is enough to inspire much respect... 
I have a small batch of gold-plated components that's ready to be processed, and I am still in the process of determining whether i'll use poor man's
or the real thing. Of course, it's small scale batches because I am very limited in what I can do outdoors (busy urban area) so I'll do this inside
with a series of scrubbers/bubblers. Yeah I know, I'd rather do this outside but I really can't and I don't have a vent hood. 
Robert
Chemistry Alchemist - 25-8-2011 at 22:19
Wouldnt that reaction produce Nitric Acid and Sodium Chloride? Heating the mixture to produce Nitrogen Dioxide gas (copper or silver used as a
catylist) bubble of the nitrogen dioxide into 30% Hydrogen Peroxide to produce Nitric acid?
woelen - 25-8-2011 at 22:56
This reaction gives some NaCl and some HNO3, but the reaction is far from clean. If you heat the mixture, then you'll get ONCl (nitrolsyl chloride, an
orange gas) and also some NOx and Cl2. if you add copper (an no it is NOT a catalyst, it is quickly used up), then that dissolves, but hardly any gas
is produced. Most of the copper will react with Cl2 and this does not give any gas. Of course, some gas is produced, but don't expect that to be pure
NO2. It will be a mix of NO2, ONCl, Cl2 and NO. If you lead that through 30% H2O2 you'll obtain very impure HNO3. This HNO3 will contain HCl and Cl2
and on storage it will turn yellow/orange due to formation of ONCl.
Chemistry Alchemist - 25-8-2011 at 23:00
oh ok... well thats how i tried to make Nitric acid and no chlorine was produced from it
Gui316 - 25-8-2011 at 23:43
But you did not make nitric acid either, did you?
Chemistry Alchemist - 25-8-2011 at 23:54
yeah i made dilute nitric acid, i used water instead if hydrogen peroxide because i didnt have any one me
Chemistry Alchemist - 25-8-2011 at 23:55
http://www.youtube.com/watch?v=2yE7v4wkuZU
NurdRages video on making nitric acid, he done what i just said
woelen - 26-8-2011 at 02:24
I certainly believe this makes HNO3, but it will be impure. I'm quite sure that a lot of chloride will be present in this acid. Test some of the acid
by adding a few drops to distilled water and add a few drops of solution of AgNO3 to this. Most likely you will have a nice white cloud of AgCl.
rstar - 29-9-2011 at 05:31
This mixture can dissolve Gold so it may also dissolve Platinum
AndersHoveland - 29-9-2011 at 11:56
Still have not got around yet to doing the experiment.
Going to add some solid NH4NO3 into 30 percent concentrated hydrochloric acid in a plastic bottle, then screw the cap tightly on. The bottle will be
left to sit (in a remote location) for several days. If the concentrated acid catalyses any decomposition of the NH4NO3, the bottle will have burst
after that time, or at least will bulge outward.
Theoretically it might work, but I have an instinctual feeling that nothing will happen.