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Author: Subject: Electrolysis of Nitrates
chemoleo
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[*] posted on 20-3-2004 at 10:14
Electrolysis of Nitrates


Had this conversation with someone recently, on the electrolysis of salts in general.
Well, for instance, the electrolyis of chlorates gives perchlorates, sulphates give peroxo sulphate, but how about nitrate?

Obviously there is no higher oxidation state than 5, so what could happen? I am tempted to think nothing, but the electrolysis of water itself, to H2 and O2.

I.e. I take a saturated solution of NaNO3, and electrolyse this.




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[*] posted on 20-3-2004 at 10:36


Well, there are pernitrates but they are somewhat unstable.

O
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N-O-O-
|
O




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[*] posted on 20-3-2004 at 10:54


Why do text books and teachers all say that nitrates, sulphates and chlorates cant be oxidized by electrolysis when things actually happen to them when you do so? :mad: Im all confused now :(
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[*] posted on 20-3-2004 at 14:46
Electrolysis of KNO3


I once electrolysed a solution of KNO3 in a cell with two carbon rods separated by a membrane. After a while (once the solution had a pH > about 13.5), I got a distinct smell of NH3 at the cathode.

I've also heard that it is possible to get nitrates (with small yield) by electrolysing ammonium salts. If anyone wants to try this, I would NOT recommend using the chloride:o.
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[*] posted on 21-3-2004 at 11:55


Quote:
Originally posted by Saerynide
Why do text books and teachers all say that nitrates, sulphates and chlorates cant be oxidized by electrolysis when things actually happen to them when you do so? :mad: Im all confused now :(


Teachers lie.
Every year of chem I have taken I always find out that of what I took last year about 10% of it was a lie :mad:
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[*] posted on 29-3-2004 at 02:32


Won't the electrolysis of nitrate salts gives nitric acid at the anode???:o



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[*] posted on 29-3-2004 at 16:00


Quote:
Originally posted by darkflame89
Won't the electrolysis of nitrate salts gives nitric acid at the anode???:o


Yes, but its hard to get much concentration (pH less than 0.5 say, which would only be 0.3M). Apparently some mixing goes on through the membrane. Possibly would work with a special membrane. You might be able to distill the HNO3, but presumably if someone has a distilling apparatus they can probably already make HNO3 using the nitrate and sulfuric acid.
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[*] posted on 29-3-2004 at 17:11
Membrane.


Has anyone got any idea how such a membrane could be constructed or bought?

I've got 50kg of ammonium nitrate and about 60 kg of potassium nitrate, and an unlimited supply of electricity. It's nice to live only 50 kilometers from a nuclear plant.


[Edited on 2004-3-30 by axehandle]




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darkflame89
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[*] posted on 30-3-2004 at 02:11


Got this recent idea, dunno if it works.

React MgO with NH4NO3 to get the ammonia and the Mg(NO3)2

Then, take the Mg(NO3)2 and heat it to get the NO2 gas. You then dissolve it in water to get nitric acid.

Then you could probably concentrate it by electrolysis.




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[*] posted on 30-3-2004 at 02:56


If NO2 is dissolved in water it gives a mixture of nitrous and nitric acids, not only nitric acid.

darkflame89, what do you mean by concentrating by electrolysis?!
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rikkitikkitavi
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[*] posted on 30-3-2004 at 06:01


MgO doesnt hydrolyse easily to Mg(OH)2

Neither is it easy to react
Mg(OH)2 + 2 NH4NO3 => Mg(NO3)2 + 2 NH3 (g) due to the low solubility of Mg(OH)2.

Try with CaO instead.

Nitric acid can not be concentrated by electrolysis since it decomposes into water, NH3, NH4+ , NOx, e t c,
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darkflame89
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[*] posted on 31-3-2004 at 01:43


But i can hardly find CaO in Singapore, unless i can convert CaCO3 to CaO



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[*] posted on 31-3-2004 at 04:44
NO3 radical


from <a href="http://bcis.pacificu.edu/~polverone/copae.html">The Chemistry of Powder and Explosives</a>:
<blockquote>quote:<hr>Ohman (532. Elektrochem., 42, 862 (1936); Svensk Kemisk Tid., SO, 84 (1938)) in Sweden has developed an ingenious electrolytic
process for the production of nitric esters direct from ethylene.
The discharge of the nitrate ion (NO<sub>3</sub><sup>-</sup>;) at the anode liberates the
free nitrate radical (NO<sub>3</sub>;) which in part combines directly with
ethylene to form nitroglycol.
H<sub>2</sub>C=CH<sub>2</sub> + 2NO<sub>3</sub> <s>&nbsp;&nbsp;&nbsp;></s> O<sub>2</sub>NO-CH<sub>2</sub>-CH<sub>2</sub>-ONO<sub>2</sub>
Another portion of the free nitrate radical apparently reacts with
itself and with water as indicated below, and the oxygen which
becomes available enters into the reaction with the consequent
formation of dinitrodiglycol.
2NO<sub>3</sub> <s>&nbsp;&nbsp;&nbsp;></s> N<sub>2</sub>O<sub>5</sub> + [O]
N<sub>2</sub>O<sub>5</sub> + H<sub>2</sub>O <s>&nbsp;&nbsp;&nbsp;></s> 2HNO<sub>3</sub>

H<sub>2</sub>C=CH<sub>2</sub> + [O] + 2NO<sub>3</sub> <s>&nbsp;&nbsp;&nbsp;></s> O<sub>2</sub>NO-CH<sub>2</sub>-CH<sub>2</sub>-O-CH<sub>2</sub>-CH<sub>2</sub>-ONO<sub&g t;2</sub>
A platinum gauze anode is used. It is immersed in an acetone
solution of calcium nitrate which is kept continuously saturated
with ethylene which is bubbled through in such manner that it
sweeps over the surface of the platinum gauze. An aluminum
cathode is used, in a catholyte consisting of a nitric acid solution
of calcium nitrate, and the cathode compartment is filled to a
higher level since the liquid moves into the anode compartment
as the electrolysis progresses. After the electrolysis, the cathode
liquid is fortified with nitric acid for use again. The anode liquid
is neutralized with slaked lime, and distilled in vacuum for the
recovery of the acetone, and the residue, after the removal of
calcium nitrate, washing, and drying, consists of a mixture of
nitroglycol and dinitrodiglycol and is known as Oxinite. Dynamites
made from Oxinite differ but little from those made from
nitroglycerin.<hr></blockquote>

now instead of using ethylene why not combine it with a kolbe reaction?!!
eg electrolysis of NaNO3 and sodium acetate to get methyl nitrate at anode and hydrogen at cathode major byproduct of anode would be ethane but also traces of methanol and oxygen




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[*] posted on 16-10-2004 at 17:11
CaO


CaO has a higher solubility than MgO. Even given that, it takes quite some time for it to
react with NH4NO3. Reacting MgO would probably push the limits of your patience.




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[*] posted on 17-10-2004 at 13:35


Actually, CaO reacts immediately with water to
Ca(OH)2 . The reaction can be slow or fast, depending on particle size (surface).

MgO , if not heated up to 1500 C or so, reacts much more slowly, taking up to days to hydrolyze. If heated to about 1500 C (dead burned) crystal structure changes and it is almost inert (magnesia)

however, I will take back that Mg(OH)2 doesnet react with NH4NO3(not that it matters much six months later).

Mg(OH)2 does react with ammoniumsalts.

/rickard
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[*] posted on 24-3-2005 at 13:04
Electrolysis of nitric acid


For some reason, I discovered this document on the electrolysis of nitric acid, which I never noticed before. I hope noone else posted it somewhere, I don't even know how I obtained it.

Anyway - it's actually quite interesting, and confirms hodges observation - the electrolysis of HNO3 causes reduction of the nitrogen, not oxidation. That is, it depends on the cathodes being used, Pt electrodes and a diaphragm produce nitric oxide, copper cathodes ammonia, and polished zinc 46 % hydroxylamine (next to ammonia!!)
So essentially, without electrode separation, the electrolysis of HNO3 with Zn cathode should produce ammonium nitrate and hydroxylamine nitrate!

I thought this is too interesting to leave this unmentioned.

Attachment is as .doc, & large, might change this later. But have a look for now :)

[Edited on 25-3-2005 by chemoleo]

[Edited on 16-12-2007 by chemoleo]

electrolysishno3gr2.gif - 105kB




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[*] posted on 5-4-2008 at 09:50
Ntric acid by electrolysis


Just read somewhere else about a proposal to synthesise nitric acid from nitrates in solution. Also I found a book in the site library that suggests it is both possible and practical.

Has anyone done it?

Could I electrolyse KNO3 and get HNO3 + K...
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[*] posted on 5-4-2008 at 10:13


It's a form of electrodialysis, using cation and anion selective membranes.

http://www.agc.co.jp/english/chemicals/ion-maku/selemion/sel...
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[*] posted on 6-4-2008 at 04:08


Quote:
Originally posted by Contrabasso
Has anyone done it?
Could I electrolyse KNO3 and get HNO3 + K...


Look in Hale's "Manufacture of Chemicals by Electrolysis" for the old "Nodon Process"!
It claimed to produce HN03 from alkali-nitrates in peat, but the mechanism is a bit unclear.

P
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[*] posted on 6-4-2008 at 05:54


Merged your new thread, contrabasso, with this one. It should answer some questions.

As indicated, your nitrate salt will get reduced unless you employ selective anion membranes.




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[*] posted on 6-4-2008 at 08:49


Contrabasso, all things considered, IMO, producing HN03 from KN03 electrolytically looks so fraught with difficulties it makes distillation from H2S04 look like child's play.

P
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[*] posted on 6-4-2008 at 15:42


Elerctrolysuis o nitrates, at a suffuiciently high voltage, would produce either pernitrates, NO4-, or else nitrogen peroxide, NO3 or N2O6.
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