Sciencemadness Discussion Board

I'm pretty sure I made nitric acid...

Upsilon - 24-3-2014 at 12:04

I began with a saturated solution of calcium nitrate (can be bought very cheaply as fertilizer) and added a stoichiometric amount of 98% sulfuric acid according to this equation :
Ca(NO3)2 (aq) + H2SO4 (l) -> CaSO4 (s) + 2HNO3 (aq)

I filtered out the insoluble calcium sulfate, and threw a modern penny (copper plating) into the resulting solution. It took a long time for the copper plating to start dissolving (I did this on a very small scale without appropriately-sized glassware, so I had to use more water than necessary). Eventually the plating on the penny began developing holes and bubbles emerged. The solution began turning a pale blue, due to the formation of copper nitrate.

I don't have an appropriate container to store nitric acid in currently, so I can't do this on a large enough scale to get a higher concentration. Has anyone else tried this before/is willing to try it, and wants to share their results? I'd like to know if it is feasible to expect high concentrations of nitric acid (50%+) this way.

Pyro - 24-3-2014 at 12:06

the produced CaSO4 is a bitch to work with, it takes forever to filter and fucks up your glassware if you happen to heat it. you should transform the Ca(NO3)2 to NaNO3 or KNO3 before starting

Upsilon - 24-3-2014 at 12:10

Quote: Originally posted by Pyro  
the produced CaSO4 is a bitch to work with, it takes forever to filter and fucks up your glassware if you happen to heat it. you should transform the Ca(NO3)2 to NaNO3 or KNO3 before starting


I only used calcium nitrate instead of sodium/potassium nitrate because calcium sulfate is basically insoluble in water, while sodium/potassium sulfate are soluble and will be much harder to separate from the HNO3 solution.

Zyklon-A - 24-3-2014 at 12:54

Yes, I have done it before, I actually use barium nitrate mostly, as it is somehow cheaper for me to get, and the corresponding sulfate salt is less soluble.
Getting near anhydrous nitric acid is possible on paper, but in reality, it's too hard to filter of so much solid (Ba/CaSO4) in proportion to the small amount of liquid (nitric acid.)
I add an equal amount of water (by weight) to the sulfuric acid, this yields 77.77% nitric acid by weight, which is quite good.


[Edited on 24-3-2014 by Zyklonb]

blogfast25 - 24-3-2014 at 12:54

Quote: Originally posted by Upsilon  
[...] calcium sulfate is basically insoluble in water, while sodium/potassium sulfate are soluble and will be much harder to separate from the HNO3 solution.


Calcium sulphate is better described as 'very poorly soluble'. Your nitric acid is slightly contaminated. Just evaporate a bit of it to dryness...

Zyklon-A - 24-3-2014 at 12:58

Yes, barium sulfate is less soluble: 0.0002448g/100 mL at 20 °C, Vs. calcium sulfate: 0.21g/100ml at 20 °C.
Quite a bit of difference.

Upsilon - 24-3-2014 at 13:01

But barium nitrate is also drastically less soluble than calcium nitrate...doesn't that mean you need more water to completely dissolve it, reducing the concentration of the final product?

blogfast25 - 24-3-2014 at 14:19

Quote: Originally posted by Upsilon  
But barium nitrate is also drastically less soluble than calcium nitrate...doesn't that mean you need more water to completely dissolve it, reducing the concentration of the final product?


Not necessarily, no. Precisely because BaSO4 is so insoluble you can treat even a slurry of Ba(NO3)2 with H2SO4 and still make nitric acid that way. A waste of a perfectly useful barium salt, if you ask me, but each to their own.

Töilet Plünger - 24-3-2014 at 14:33

This was used in a distillation, the video is here.

http://www.youtube.com/watch?v=7akk5ppJjEw

Zyklon-A - 24-3-2014 at 15:44

Quote: Originally posted by Upsilon  
But barium nitrate is also drastically less soluble than calcium nitrate...doesn't that mean you need more water to completely dissolve it, reducing the concentration of the final product?

Like blogfast25 said, the insolubility of barium nitrate drives the equilibrium nearly completely to the right: H2SO4 + Ba(NO3)2 → 2HNO3 + BaSO4↓.
The solubility data I mentioned above is of course for water, not dil. nitric acid, but I'm pretty sure it's nearly insoluble in both.

Upsilon - 25-3-2014 at 09:56

Another question: can I store nitric acid in an empty plastic hydrogen peroxide brown bottle without any issues?

DraconicAcid - 25-3-2014 at 09:58

Quote: Originally posted by Upsilon  
Another question: can I store nitric acid in an empty plastic hydrogen peroxide brown bottle without any issues?

You're better off storing it in glass.

HgDinis25 - 25-3-2014 at 10:02

It depends on the type of plastic. HDPE usually stands most acids (even 98% sulfuric acid). For Nitric acid with a concentration <70% HDPE and even PE will do the job.
It is advised against storing corrosive substances (unless those that corrode plastic) in glass because it can easilly break and release the contents (bull**** for me, but posting the recomendation anyway).

Upsilon - 25-3-2014 at 10:47

Quote: Originally posted by HgDinis25  
It depends on the type of plastic. HDPE usually stands most acids (even 98% sulfuric acid). For Nitric acid with a concentration <70% HDPE and even PE will do the job.
It is advised against storing corrosive substances (unless those that corrode plastic) in glass because it can easilly break and release the contents (bull**** for me, but posting the recomendation anyway).


I looked on the bottom and it is in fact HDPE. The brown bottle will also help combat light decomposition, so that's a bonus.

HgDinis25 - 25-3-2014 at 11:13

The UV decomposition of <70% Nitric Acid is negligible. Only above those concentrations the HNO3 will start decomposing (at a very very very slow rate) into nitrogen oxides:
4 HNO3 → 2 H2O + 4 NO2 + O2

blogfast25 - 25-3-2014 at 14:13

I get mine (5 L of 70 w%) delivered in HPDE jerrys. No problems whatsoever.

hyfalcon - 25-3-2014 at 15:34

The cap may be an issue though.

ElizabethGreene - 27-3-2014 at 18:11

Quote: Originally posted by Upsilon  

I looked on the bottom and it is in fact HDPE. The brown bottle will also help combat light decomposition, so that's a bonus.


Please label this bottle in the most terrifying manner possible. It would be horrific if someone attempted to use Nitric acid to clean an open wound. Ouch.