Sciencemadness Discussion Board

Is there a best nitrate salt for HNO3 production?

SHlTnipplesmadeofeggs - 26-9-2018 at 16:30


TL;DR Is sodium nitrate best for HNO3 production, or does it really matter if I use sodium or potassium?

Hello,

It seems I remember having read at some point that sodium nitrate was best for making HNO3. However I don't remember why and I can't find where I read that. I've read that ammonium nitrate can create dangerous byproducts (especially if you're heating with an open flame) like nitrous oxide.

I know you can make HNO3 from any nitrate salt (well I'm sure there are some that present difficulties even if technically possible). I was just wondering if certain salts lent themselves to this moreso than others. I currently have KNO3 and NH4NO3 and I'm currently making NaNO3 (because when I started I thought it was better), but I can probably procure and/or make most other common nitrates if one in particular is better.

I'm also thinking about distilling the HNO3 under vacuum, if that makes any difference as to what salt I use.

WGTR - 26-9-2018 at 17:06

I don’t like your username.

SHlTnipplesmadeofeggs - 26-9-2018 at 17:20

Well look at yours! At least mine makes sense!;)

TheMrbunGee - 26-9-2018 at 20:58

For what you have - Ammonium nitrate is better. because of how much acid you can get from gram of nitrate salt. Calcium nitrate is also good, because it is cheap, (but not that easy to find pure) but I am not sure how hard it is to clean out the calcium sulfate after you are done.

What you really mean by "better"? Lighter the nitrate cation, more acid you will get.. (and same goes for count of nitrate groups) but nothing really beats Lithium nitrate on this, not counting its costs.

Vosoryx - 26-9-2018 at 21:27

Quote: Originally posted by SHlTnipplesmadeofeggs  
Well look at yours! At least mine makes sense!;)


Are you sure about that bud?

chornedsnorkack - 26-9-2018 at 23:03

Are there any significant advantages to barium nitrate?
Low solubility of barium sulphate, namely. With stoichiometric amount of sulphuric acid, you might precipitate most of both barium and sulphate.
(Advantages shared to lesser extent with strontium, lead and silver nitrates).

TheMrbunGee - 27-9-2018 at 00:04

Quote: Originally posted by chornedsnorkack  
Are there any significant advantages to barium nitrate?
Low solubility of barium sulphate, namely. With stoichiometric amount of sulphuric acid, you might precipitate most of both barium and sulphate.
(Advantages shared to lesser extent with strontium, lead and silver nitrates).



Barium nitrate is toxic, not really common, quite expensive.
And you need 2g of nitrate for every gram of nitric acid.
As for ammonium nitrate you only need 1.3g of nitrate for 1g of nitric acid.
For okay quality you need to distill the acid anyway, and solubility of barium nitrate is not that great.

I made my nitric acid from calcium ammonium nitrate fertilizer, but I converted the salts to sodium nitrate, because I was not sure about cleaning calcium sulfate mess produced. (had bad experience with Ca salts and glassware) . And it was cheaper still (Calcium nitrate and NaOH used), than using KNO3, due to its price.

mayko - 27-9-2018 at 00:48

There are some disadvantages to ammonium nitrate; I'd go with Na/KNO3:

https://www.sciencemadness.org/whisper/viewthread.php?tid=5
Quote: Originally posted by TheMrbunGee  
Barium nitrate is toxic, not really common, quite expensive.
And you need 2g of nitrate for every gram of nitric acid.
As for ammonium nitrate you only need 1.3g of nitrate for 1g of nitric acid.
For okay quality you need to distill the acid anyway, and solubility of barium nitrate is not that great.




plus, your barium is now bound up as the sulfate, which makes it difficult to reclaim

Sulaiman - 27-9-2018 at 01:19

I have tried sodium, potassium and calcium nitrates to make RFNA,
for me, in UK, ammonium nitrate may set off anti-terror alarm bells :P

Calcium nitrate is cheap but caused the most NO2 to be generated as it was the most difficult to heat through.

Sodium nitrate gives more moles/kg and less cost/kg than potassium nitrate,
the only other difference between the two is the by-product,
do you want a sodium or potassium salt, or don't care as you will dispose of it ?

If you only want dilute nitric acid then
the insolubility of calcium sulphate allows a simple procedure,
(discussion here http://www.sciencemadness.org/talk/viewthread.php?tid=70712 )

I have not tried the procedure but it should be something like ;
Combine the ratios of calcium nitrate solution, sulphuric acid and water
that will produce the required concentration of nitric acid.
(calcium nitrate is commonly supplied as the tetrahydrate)
Higher target concentrations may lead to loss by adsorbtion to the calcium sulphate.
Lower target concentrations may give a relatively higher calcium sulphate impurity level due to its slight solubility.
I'd try around 20% then dilute as required, but I'm guessing.

Allow to settle then decant to get your acid of reasonable purity.
Filter the decanted acid if any cloudiness.
Distil for higher purity and/or concentration.

as it is unlikely that perfect stoichiometry will be achieved,
there will be some calcium nitrate or sulphuric acid excess in solution

if drain un-blocker grade sulphuric acid is used,
heating may cause the nitric acid to oxidise the dye/pigment
- not tried, but now I have to try it for myself ........

P.S. Azeotropic 98.3% w/w sulphuric acid has one water molecule per 10.6 acid molecules,
my 95% w/w has about one water molecule per 3.5 acid molecules.
If you want to calculate to excessive accuracy :D

P.S. I forgot to account for the calcium sulphate forming the di-hydrate in an aqueous environment,
so the nitric acid will be more concentrated than expected if not accounted for.

[Edited on 27-9-2018 by Sulaiman]

Herr Haber - 27-9-2018 at 03:10

I guess all has been said :)

If you have access to big quantities of NH4NO3 it's better than NaNO3
If you have to chose between Sodium, Calcium or Potassium nitrate stick with Sodium nitrate.
Getting rid of potassium sulfate stuck in your RBF can be quite a pain. Ca would be even worst.

So unless you need one of those sulfates, stick with sodium.
Unfortunately for me, Ammonium nitrate is quite hard to find around here. Otherwise I would keep the sulfate for ammonia generation.

Sulaiman - 27-9-2018 at 03:25

I've only made rfna from calcium nitrate once
and I had no problem washing out the calcium sulphate with tap water.
maybe I was just lucky,
OR
maybe in dilute/aqueous environments the di-hydrate forms ?

I stopped my rfna distlllation when excessive NO2 was generated
so I did not boil to dryness
..........................................................................................
I just checked my stock and I seem to have no calcium nitrate remaining
and there are other things that have more priority
so I shall not be doing this experiment any time soon.
I did the sums if anyone wants to try, at the one mole scale ;
54.25 ml (100 g) 98% sulphuric acid added drop wise to
236.15 g of dry calcium nitrate tetra-hydrate dissolved in
234.02 g water
should produce about 315 g of 20% w/w nitric acid,
maybe 250 ml recoverable with 0.25% calcium sulphate as dissolved impurity.

[Edited on 28-9-2018 by Sulaiman]

SHlTnipplesmadeofeggs - 1-10-2018 at 06:09

Quote: Originally posted by TheMrbunGee  
For what you have - Ammonium nitrate is better. because of how much acid you can get from gram of nitrate salt. Calcium nitrate is also good, because it is cheap, (but not that easy to find pure) but I am not sure how hard it is to clean out the calcium sulfate after you are done.

What you really mean by "better"? Lighter the nitrate cation, more acid you will get.. (and same goes for count of nitrate groups) but nothing really beats Lithium nitrate on this, not counting its costs.


I didn't really have any particular definition of better, I was waiting to see what was better to the people here and for what reasons? Ease of obtaining, useful byproducts, easier cleanup, etc. etc. It could be about anything I suppose, I guess I'm just asking what nitrates particular members like best for acid production and why they like them.
Quote: Originally posted by Vosoryx  
Quote: Originally posted by SHlTnipplesmadeofeggs  
Well look at yours! At least mine makes sense!;)


Are you sure about that bud?


As sure as I am about anything in life
Quote: Originally posted by Sulaiman  

Sodium nitrate gives more moles/kg and less cost/kg than potassium nitrate,
the only other difference between the two is the by-product,
do you want a sodium or potassium salt, or don't care as you will dispose of it ?

....

as it is unlikely that perfect stoichiometry will be achieved,
there will be some calcium nitrate or sulphuric acid excess in solution

if drain un-blocker grade sulphuric acid is used,
heating may cause the nitric acid to oxidise the dye/pigment
- not tried, but now I have to try it for myself ........

P.S. Azeotropic 98.3% w/w sulphuric acid has one water molecule per 10.6 acid molecules,
my 95% w/w has about one water molecule per 3.5 acid molecules.
If you want to calculate to excessive accuracy :D

...


[Edited on 27-9-2018 by Sulaiman]


I'm by no means an expert chemist so bear with me (the extent of my education was as a chem student until O-chem II, but I was a terrible student at the time and have forgotten most of the small amount I even learned) but from doing some reading/watching I believe I remember seeing that you could make sodium/potassium metabisulfite and that could then be turned into acetic (or maybe glacial acetic) acid. I might try to do that, but then again I may be lazy and decide not to do so. I don't have any particular need for it at the moment, but I like making things and having that on the shelf will definitely come in handy at some point.

[Edited on 1-10-2018 by SHlTnipplesmadeofeggs]

macckone - 1-10-2018 at 06:22

with calcium sulfate precipitate, it is better to dedicate a beaker to that use.
The calcium sulfate will settle out then decant. Filtering calcium sulfate is a pain.
But it settles really well.
Then get it out while it is wet and malleable.
It scrubs off easily unless you get a cake dried at the bottom or it fully sets.
Then it is soak scrub soak scrub.
Wet plaster is very soft but it is a pain to scrub out of a beaker.
I would not want to scrub it out of a RBF.

SHlTnipplesmadeofeggs - 1-10-2018 at 07:02

Quote: Originally posted by macckone  
with calcium sulfate precipitate, it is better to dedicate a beaker to that use.
The calcium sulfate will settle out then decant. Filtering calcium sulfate is a pain.
But it settles really well.
Then get it out while it is wet and malleable.
It scrubs off easily unless you get a cake dried at the bottom or it fully sets.
Then it is soak scrub soak scrub.
Wet plaster is very soft but it is a pain to scrub out of a beaker.
I would not want to scrub it out of a RBF.


Calcium nitrate probably won't be used (sounds like it's a PITA?) as ammonium and potassium nitrate is readily available and obviously other nitrates can be made from those salts.

Melgar - 1-10-2018 at 22:21

Calcium nitrate also doesn't react all the way, since the granules tend to form insoluble calcium sulfate coatings that shield much of the nitrate salt from reacting. Calcium, ammonium, and sodium nitrate are better, because in most cases you're actually forming the bisulfate salt, which has a low enough melting point to not be a problem.

weilawei - 2-10-2018 at 05:16

Quote:
I'm by no means an expert chemist so bear with me (the extent of my education was as a chem student until O-chem II, but I was a terrible student at the time and have forgotten most of the small amount I even learned) but from doing some reading/watching I believe I remember seeing that you could make sodium/potassium metabisulfite and that could then be turned into acetic (or maybe glacial acetic) acid. I might try to do that, but then again I may be lazy and decide not to do so. I don't have any particular need for it at the moment, but I like making things and having that on the shelf will definitely come in handy at some point.


I made some a few months back by neutralizing sodium hydroxide with concentrated vinegar (separated by freezing), recrystallizing the sodium acetate trihydrate, baking in an oven to drive off the water of crystallization, and distilling from sulfuric acid.

In short, it works, but yields are lousy and it takes a ton of work to prepare it this way.
It's also more expensive to do it this way. GAA is cheap.

Also, KNO3 is fine for making HNO3. I also just ran Magpie's prep of that. 10 second bursts in a microwave and hot water easily removed the potassium sulfate cake.

hissingnoise - 2-10-2018 at 06:40

The Na salt contains more nitrate than the K salt but to get strong nitric acid the hygroscopic salt must be well dried.

NH4NO3 is partially oxidised during distillation and the water produced will dilute the NA distillate.


fusso - 2-10-2018 at 11:13

I think it would be NaNO3 due to being the cheapest nitrate and no other nitrogenous byproducts.

[Edited on 02/10/18 by fusso]