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The chemistry of making nitric acid


#1

According to the help page from on ebay, you can make nitric
acid by mixing 1/2 cup of sodium nitrate with one quart of sulfuric
acid. My question is, will this mixture indeed produce nitric acid?
If yes, will it be of a quality you could use, to make aqua regia for
refining? Thank you to our chemist friends who probably know the
answer to this.


#2
will [the proposed process] be of a quality you could use, to make
aqua regia for refining? 

Since aqua regia consists of 3 parts concentrated nitric acide and 1
part hydrochloric acid, the short answer is no.

David


#3

I will just go ahead and say that you are nuts. Except that back in
my amateur chemist days, I was nuts, too. Mixing sodium nitrate
(saltpeter) and sulfuric acid is the old fashioned way of making
nitric acid. The modern way is to make nitrogen dioxide from ammonia
and dissolve it in water. NO2 is the red gas that HNO3 puts off, and
is the redness in fuming nitric. The problem with doing it the old
way is that it’s “dirty” - it requires fractional distillation to
make relatively pure HNO3. In short: Yes, you will get something
resembling HNO3, but unless you do careful Molar calculations you
won’t know really what it is, or what concentration. It will be some
mix of the two acids, with salts dissolved in it. Maybe you want to
distill HNO3 in your kitchen, but I won’t be there. Obviously, the
costs of setting up that apparatus and a hood and all is way more
than just going out and buying a pint of acid…

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#4

Whilst this is definitely a John Burgess kind of question…

Sulphuric acid is H2SO4…and while you might get some nitric
acid by dumping sodium nitrate into it…The Dance of the Atoms
(OK, Ok, Molecules, too), you see…

Nitric acid is HNO3 (I think)…

I don’t know what’s going to happen with all of the “S” floating
around in there…or the S04’s running looser…or derivatives
thereof… It ain’t gonna be a straight nitric acid as a result,
though…even if a bunch of sulfur and it’s derivatives bubble off
and stink the place up… And some of those can be nasty critters…

If there’s precipitates, I don’t think it would be fun separating
them, either…

If you’ve got the sulphuric acid, then to find some nitric acid and
mix it in according to the proportions/strengths to give you your
aqua regia…would seem to be a safer and maybe saner approach…

Gary W. Bourbonais
A.J.P. (GIA)

P.S. My chemistry is High School and First Year college stuff,
qualitative was as far as I got, with a touch of organic… And
it’s been a long time since I’ve dusted off a book…


#5

The answer really is ‘it depends’… Reacting Sodium Nitrate with
Sulphuric acid will give some Nitric acid but it will also produce
Sodium Sulphate in the solution which will be a contaminant. As
Sodium Sulphate is pretty unreactive stuff, this may not matter (one
of its uses is as a filler in washing detergents) but it may make a
difference, who knows? If you are intending to use Sodium Nitrate
fertiliser as a starting point, this is probably already contaminated
by other chemicals put there to make it rain resistant or improve its
action as a fertiliser. The other factor will be the strength of the
acid and it will be a pretty fine balancing act to make sure that
there is no unused Sodium Nitrate or Sulphuric acid in the solution
which will also contaminate it. I’m wondering why it is that, if you
can get Sulphuric acid and Sodium Nitrate, you can’t just buy Nitric
acid?

Ian
Ian W. Wright
Sheffield UK


#6
If you've got the sulphuric acid, then to find some nitric acid and
mix it in according to the proportions/strengths to give you your
aqua regia...would seem to be a safer and maybe saner approach... 

Aqua regia is nitric and hydrochloric acids no sulfuric in the mix.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#7

Thanks Ian and Gary,

I can (and do) just buy the concentrated nitric acid. I was
inquiring because of a posting about the person who sells the sodium
nitrate on ebay. I was curious what the reaction would be, of mixing
these two chemicals. I don’t intend to experiment with this. I felt
sure,as you pointed out, there would be contaminants or
precipitates.

I have been getting fine results, with the aqua regia I make using
nitric and hydrochloric acid. For sure, I don’t do this in my
kitchen. In case this posting encourages any one unfamiliar with
these acids to use them, I want to point out the fumes are deadly,
and both acids are really nasty chemicals to work with. Don’t fool
with them unless you have the proper safety equipment and knowledge.


#8

Phew! That’s good news, that you’re not going into the chemical
business… Here’s a pretty good and easy rundown on the processes
involved:

Under Synthesis…

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