Converting HCl to HNO3
Kevin Christiansen
A (rather weak) form of aqua regia can be made by simply adding
KNO3 to HCl, because of the following reaction:
HCl + KNO3 <-----> HNO3 + KCl
While this form of aqua regia *does* dissolve gold, the dissolution
requires considerably more time to dissolve gold than "standard"
aqua regia (HCl + HNO3) does.
I am guessing that this slower dissolution is caused by the low
concentration of HNO3 in the mixture, since there is nothing to
drive the above reaction to the right...
I am wondering, however, if the above reaction could be forced to
the right by adding enough KCl to result in a solution that was
saturated with KCl. A solution that is saturated with KCl could
not dissolve any more KCl, so it would be as if KCl was insoluble
in the solution, which would drive the above reaction to the right.
This reaction would probably be slower than a "standard" precipitation
reaction (such as precipitating chalk, which happens "instantly"), but
I can't see any reason why it would not happen, given enough time.
Perhaps this could be encouraged by using an excess of KNO3 and
heating the solution, taking advantage of the fact that KNO3 is
so much more soluble in hot water than KCl is...
Do you think this scheme (pre-saturating the solution with KCl to
drive the reaction to the right) would work, or is there something
I am missing?
Would sufficient KNO3 drive the reaction sufficiently to the right so
that the amount of HNO3 in solution actually exceeded the amount of
HCl in solution?
Assuming that this scheme did work, the KCl in solution (which would
not be much, due to the common ion effect with the HCl) would probably
not effect the solution's ability to dissolve (and then precipitate)
gold. But if it did, the KCl could be removed by filtration followed
by distillation.
What do you think? Would this work or am I barking up the wrong tree?
Thank you very much for any help you can give me!
- Kevin Christiansen
Ron Jones
news:6b1c57d3.03010...@posting.google.com...
Have you tried boiling the mix? As one who has dissolved lots of gold in
AQ, it's not that fast cold, and much better to heat it up. Also you could
distill out some water. I used to dissolve the gold and boil the mix to
expel all the acids - takes a toll on the fume cupboard fans though...
Ron Jones
Don't repeat history, see unreported near misses in chemical lab/plant at
http://www.crhf.org.uk
Oscar Lanzi III
water by adding H2SO4 work? Possibly, could the nitric acid be made
separately from KNO3 plus H2SO4?
--OL
Dale A Trynor
> Hello all!
>
> A (rather weak) form of aqua regia can be made by simply adding
> KNO3 to HCl, because of the following reaction:
>
> HCl + KNO3 <-----> HNO3 + KCl
Dale Trynor wrote:
Not sure why you cant just buy hydrochloric acid, as its commonly sold in
the hardware store as a rust remover.
Even our digestive system uses a 5% solution of HCl. If HCl is scarce you
can make it as an impure solution by precipitating calcium sulfate from a
calcium chloride solution. with sulfuric acid from old car batteries.
Burning and or "pyrolitizing ? on spelling" polyvinyl plastics is another
possibility but you need to mix or provide water somehow and if creative
it could be done in the same reaction. I have had to experiment on
occasion using beach balls as a way of temporarily containing such gases.
Sulfuric acid on chlorides and distilation is usualy the best but I am
very unsure on what it is that you are really interested in on all of
this. Maybe you want the challenging ?.
>
>
> While this form of aqua regia *does* dissolve gold, the dissolution
> requires considerably more time to dissolve gold than "standard"
> aqua regia (HCl + HNO3) does.
I have noticed that even a trace of HCL in concentrated nitric acid will
dissolve gold however it dose get a bit slow. I have also noticed that
even doubling the solution with water will vastly slow reaction even more
and when one gets to about 4 times the volume of water, then no dissolving
of gold appears to occur at all. Aqua regia is one thing but dilute is
another animal and in that way differs quite a bit from other acids in
what one gets with dilution.
> Assuming that this scheme did work, the KCl in solution (which would not
> be much, due to the common ion effect with the HCl) would probably
> not effect the solution's ability to dissolve (and then precipitate)
> gold. But if it did, the KCl could be removed by filtration followed
> by distillation.
>
> What do you think? Would this work or am I barking up the wrong tree?
>
> Thank you very much for any help you can give me!
>
> - Kevin Christiansen
I find it interesting that you are interested in finding alternatives for
HCl when its so much easier to get than is nitric acid. I have had
occasion to use ammonium nitrate solution with sulfuric acid added as a
way of dissolving the copper from gold plated objects. What is good about
ammonium nitrate is that it reacts with calcium hydroxide, that you can
easily buy in the hardware store to yield ammonia and calcium nitrate. One
can then use sulfuric acid to precipitate the calcium sulfate and leave a
nitric acid solution. You get a much better product and less mess by
making nitric acid by the usual distillation method using sulfuric acid,
but fortunately for some uses its not always necessary so one can take
advantage of cheap easily available fertilizer.
www.alternatescience.com
Dale A Trynor
Dale Trynor wrote:
You can easily distill the two apart as nitric acid is reasonably stable
for this. Sulfuric acid has a very high boiling point and is used in the
production of nitric acid from nitrates by just this process of
distilling of the resultant nitric acid.
I have always loved nitric acid and have on countless occasions amassed
my friends by dissolving a coin or key in about 1 minute or less. One
can come up with endless ideas to create works of art from metals. Do it
outdoors please and keep an emergency water bottle available along with
a buch of other safty advice etc. Its fantastic.
Steve Turner
>A (rather weak) form of aqua regia can be made by simply adding
>KNO3 to HCl, because of the following reaction:
>
>HCl + KNO3 <-----> HNO3 + KCl
>
>While this form of aqua regia *does* dissolve gold, the dissolution
>requires considerably more time to dissolve gold than "standard"
>aqua regia (HCl + HNO3) does.
>
>I am guessing that this slower dissolution is caused by the low
>concentration of HNO3 in the mixture, since there is nothing to
>drive the above reaction to the right...
>
>I am wondering, however, if the above reaction could be forced to
>the right by adding enough KCl to result in a solution that was
>saturated with KCl.
Kevin,
Adding KCl will shift the equlibrium to the left, in accordance with
Le Chatlier's principle.
Equilibria of this type (proton exchange in homogeneous solution) are
typically quite fast, i.e., diffusion controlled.
Perhaps the more relevant question is, why does a mixture of nitric
and hydrochloric acid dissolve gold, whereas either alone does not.
The answer lies in formation of atomic chlorine, which is an
extraordinary oxidizing agent. Perhaps this might suggest other
approaches to the problem at hand...
Steve Turner
Real address contains worldnet instead of spamnet
Kevin Christiansen
> Kevin Christiansen wrote:
>
> > Hello all!
> >
> > A (rather weak) form of aqua regia can be made by simply adding
> > KNO3 to HCl, because of the following reaction:
> >
> > HCl + KNO3 <-----> HNO3 + KCl
>
> Dale Trynor wrote:
> Not sure why you cant just buy hydrochloric acid, as its commonly sold in
> the hardware store as a rust remover.
> Even our digestive system uses a 5% solution of HCl. If HCl is scarce you
> can make it as an impure solution by precipitating calcium sulfate from a
> calcium chloride solution. with sulfuric acid from old car batteries.
You are right - HCl is *quite* readily available. I was hoping to find
a way to make the reaction proceed to the right - in order to obtain
the less-readily-available HNO3 from the easily-obtained HCl. I am
sorry if I did not make that clear.
I have made HNO3 in the past by distilling H2SO4 + a nitrate, but H2SO4 is
quite pricey around here. I was hoping to figure out a way to make HNO3
from the (much cheaper) HCl. HCl + AgNO3 ----> HNO3 + AgCl would work,
but it isn't exactly a cheap way of doing it. Pb and Hg nitrates aren't
exactly cheap and plentiful either...
Thanks!
- Kevin Christiansen
Kevin Christiansen
> kev...@crystalcanyon.com (Kevin Christiansen) wrote:
>
> >A (rather weak) form of aqua regia can be made by simply adding
> >KNO3 to HCl, because of the following reaction:
> >
> >HCl + KNO3 <-----> HNO3 + KCl
> >
> >While this form of aqua regia *does* dissolve gold, the dissolution
> >requires considerably more time to dissolve gold than "standard"
> >aqua regia (HCl + HNO3) does.
> >
> >I am guessing that this slower dissolution is caused by the low
> >concentration of HNO3 in the mixture, since there is nothing to
> >drive the above reaction to the right...
> >
> >I am wondering, however, if the above reaction could be forced to
> >the right by adding enough KCl to result in a solution that was
> >saturated with KCl.
>
> Kevin,
>
> Adding KCl will shift the equlibrium to the left, in accordance with
> Le Chatlier's principle.
Drat! :-) I will read up on Le Chatlier's principle tonight. I wonder
if things could be pushed to the right by adding a large excess of NO3 ions,
or by increasing the concentration of the HCl by bubbling in HCl gas...
> Equilibria of this type (proton exchange in homogeneous solution) are
> typically quite fast, i.e., diffusion controlled.
>
> Perhaps the more relevant question is, why does a mixture of nitric
> and hydrochloric acid dissolve gold, whereas either alone does not.
> The answer lies in formation of atomic chlorine, which is an
> extraordinary oxidizing agent. Perhaps this might suggest other
> approaches to the problem at hand...
Hmmmm.... Instead of adding KNO3 to the HCl, perhaps I should sprinkle
in just enough MnO2 to generate some nascent chlorine. Or, perhaps I
should bubble in some Cl made by acidifying bleach...
I actually have two reasons for wanting to produce HNO3 from HCl. One is
to make aqua regia for gold refining. The other is to make HNO3 (with a
minimum of residual chlorides) for silver refining. The only commercial
source of HNO3 I have found in this area that will sell to the public
wants $35 for a gallon of 52% HNO3. Ouch!
Thanks for your suggestions and help!
- Kevin Christiansen
Steve Turner
>> >HCl + KNO3 <-----> HNO3 + KCl
>Drat! :-) I will read up on Le Chatlier's principle tonight. I wonder
>if things could be pushed to the right by adding a large excess of NO3 ions,
>or by increasing the concentration of the HCl by bubbling in HCl gas...
This would be the classical way to push the equilibrium.
>Hmmmm.... Instead of adding KNO3 to the HCl, perhaps I should sprinkle
>in just enough MnO2 to generate some nascent chlorine. Or, perhaps I
>should bubble in some Cl made by acidifying bleach...
The former is the type of thing I was thinking of in my comments. It
might work. But it also adds more complexity to the gemisch.
>I actually have two reasons for wanting to produce HNO3 from HCl. One is
>to make aqua regia for gold refining.
I hate to bring it up, for reasons that will be obvious, but have you
considered the more traditional cyanide refining? This would offer
several benefits. One is greatly reduced reactivity, meaning that a
larger selection of suitable vessels will be available, and also
meaning greater selectivity; aqua regia will dissolve all kinds of
things besides gold... Another benefit would be lower fume burden.
Dissolution of gold in HNO3 gives off NO2, which is insidious. You
can breath a lethal dose with only mild discomfort, only to die of
pulmonary edema several hours later.
Of course, HCN is no picnic either, and there is always some evolved
when working with aqueous cyanide solutions...
> The other is to make HNO3 (with a
>minimum of residual chlorides) for silver refining. The only commercial
>source of HNO3 I have found in this area that will sell to the public
>wants $35 for a gallon of 52% HNO3. Ouch!
You can also buy it online (at least for the time being...) but
shipping is quite expensive.
Dale A Trynor
> Dale A Trynor <da...@nbnet.nb.ca> wrote in message news:<3E153DD9...@nbnet.nb.ca>...
> > Kevin Christiansen wrote:
> >
> > > Hello all!
> > >
> > > A (rather weak) form of aqua regia can be made by simply adding
> > > KNO3 to HCl, because of the following reaction:
> > >
> > > HCl + KNO3 <-----> HNO3 + KCl
[snip]
>
> > calcium chloride solution. with sulfuric acid from old car batteries.
> [snip]
>
> You are right - HCl is *quite* readily available. I was hoping to find
> a way to make the reaction proceed to the right - in order to obtain
> the less-readily-available HNO3 from the easily-obtained HCl. I am
> sorry if I did not make that clear.
Dale Trynor wrote:
Now that you mention it, I should have noticed that.
> I have made HNO3 in the past by distilling H2SO4 + a nitrate, but H2SO4 is
> quite pricey around here.
Could prove very cheap where they sell car batteries however its a ~30% solution.
> I was hoping to figure out a way to make HNO3
> from the (much cheaper) HCl. HCl + AgNO3 ----> HNO3 + AgCl would work,
> but it isn't exactly a cheap way of doing it. Pb and Hg nitrates aren't
> exactly cheap and plentiful either...
Must be many ways of doing this. Heating nitrates such as copper and maybe calcium can give
you NO2 that in tern will react with water to give nitric acid as well as NO which can in tern
be reacted with more oxygen to regenerate more of the NO2. I could imagine that this would all
be too difficult and far from practical for the do it yourselfer as one might need scrubbers
etc. Another approach that might be interesting to try and if I get the time to experiment
with is heating a mix that also produces water vapor at the same time, so that it might be at
least partially condensed directly into nitric acid ' maybe?. Adding some chlorates to provide
the extra oxygen might be more efficient and careful here with any organic's etc., that could
make the mix explosive. I have no idea if this would work but its the sort of experiments that
might be worth trying just for this type of challenge.
The problem for this approach is that if you only have potassium nitrate you would need to
convert it into another nitrate that decomposes to the NO2 and metal oxide. Silver nitrate is
likely to give NO2 plus oxygen as its reduced to the metal instead of just the oxide.
Don't forget nitrogen oxides producing bacteria, silo gas is where hay is stored and gets wet
is an example of NO2 produced this way and is so bad its considered a hazard. Also the first
sources of nitrates for gunpowder I believe are clamed to have came from chicken shit, no
kidding. So its not that far out to consider taking a bunch of old fish heads and using them
somehow to make nitrates on the cheap.
Electric arks can also be used to generate NO2 but would guess its a bit power inefficient.
Old oil furnace transformers could be used for this as what they are designed to do is
generate a nice large spark.
Similar experiments can be done with sulfates to produce S03 and that can be used to produce
sulfuric acid. I am trying to dream up some experiments to produce sulfuric acid directly from
sulfur. Don't forget that cheap impure sulfuric acid is sometimes used as a drain cleaner and
I have seen it sold as such.
www.alternatescience.com
Artem Evdokimov
combustion of NH3 - using copper oxide catalyst. It was once published as a
do-it-yourself experiment in one of the soviet chemical journals.
This method does indeed produce nitrogen oxides, and in the end a weak
solution of HNO3 which can be later concentrated.
A.G.E.