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Author: Subject: Concentrating Nitric acid
Pulverulescent
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[*] posted on 18-9-2013 at 01:19


Concentration of HNO3 by electrolysis!



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PHILOU Zrealone
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[*] posted on 18-9-2013 at 03:02


Quote: Originally posted by Antiswat  
anhydrous CuSO4 as in for removing water from low concentration HNO3, right?
that should work, but gypsum should work aswell..

CuSO4 anh. can take per mole, up to 5 moles of water (5 x 16 mL / g H2O) thats 80 mL
but you need to keep in mind that you might need to squeeze the now wet CuSO4 to get more HNO3 out of it..
but however man...

Actually, it would be slightly better 5x18g of water = 92g or ml water ;)

The process with MgO (or CaO) or Mg(NO3)2 (or Ca(NO3)2) and filtration and/or distillation is interesting because:
1°) dehydratant is recyclable by heating and too much a heating causes not too much arm because MeO (Me = Mg or Ca) is also compatible with the process except it uses some of the HNO3.
2°) dehydratant at a certain nitrate content will cristallize and allow easier filtration due to precipitation by common anionic effect.
3°) no interferences of external anions...like sulfate, chloride




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[*] posted on 19-9-2013 at 11:21


Would not distilling again and using a high number of theoretical plates in the distilling column be the most efficient and possibly effective method of reaching very high concentration?
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[*] posted on 20-9-2013 at 05:04


In distilling from H2SO4/NaNO3 mixtures water finds its way into the distillate from decomp. of HNO3!
Distillation under good vacuum sidesteps this . . .




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[*] posted on 20-9-2013 at 08:50


I would be distilling from nitric acid and sulfuric acid under a vacuum of 18 inches of mercury while being stirred to prevent uneven heating.

Further, with a sufficient distilling column, one theoretically would not even need to distill again. I'm going to try a hemple column that is 25mm x 300mm filled with roughly 500 0.25-inch glass balls. By carefully controlling the temperature in the column using insulation, it seems possible that the product making its way over to the condenser could be nearly pure.
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[*] posted on 21-9-2013 at 03:29


Fractionation isn't necessary or desirable . . .
The ordinary water-cooled condenser will work fine for non-vacuum distillation, while for vacuum work extra cooling is advisable!
And, anyway, there are very few cases where anhydrous acid is essential!




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[*] posted on 21-9-2013 at 05:31


I don't see how fractionation is undesirable. Would not each evaporation and condensation cycle leave behind more of the less volatile compounds?

Anhydrous acid is, in fact, my goal.
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[*] posted on 21-9-2013 at 07:29


Quote:
I don't see how fractionation is undesirable.

Nitric acid behaves as a constant-boiling fraction in such distillations, regardless of its water-content.




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[*] posted on 21-9-2013 at 18:59


If the proper amount of sulfuric acid is introduced to the nitric acid, it seems to me that there theoretically would be no water left to form the azeotrope.

What would be left, it appears to me, would be:

H3O+
HSO4-
SO42-

[Edited on 22-9-2013 by malford]
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[*] posted on 21-9-2013 at 20:47


The amounts may have less to do with the affinity sulfuric acid has for water, than the thermodynamic favoribility of a small fraction of water to form an azeotrope with HNO<sub>3</sub>. I am sure much more complicated explinations of vapor phase interactions are required, but im at a loss...

I do know that if you apply a halfway decent vacuum to a
standard distillation apparatus (no fractionating column needed) you will get nitic acid likely beyond suitable for your needs. Even without a vacuum, very strong RFNA is easily obtained with even just 1 to 2 distillations starting from an anhydrous nitrate salt and some ~98% sulfur acid. Bubble dry air through to remove dissolved NO<sub>x</sub> and what more could you need?

[Edited on 22-9-2013 by Bot0nist]




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[*] posted on 23-9-2013 at 08:35


I agree that extremely pure nitric I will probably not need. But, I'm pursuing the science of it.

As such, I'm curious about using a distilling column. There is a large difference between a distilling column not being needed, as in more than required for typical applications, and the same being counterproductive. Is it in fact counterproductive?
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[*] posted on 24-9-2013 at 01:45


Well, the greatly extended vapour-path requires strong heating to drive the distillation ─ so yes . . .



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[*] posted on 24-9-2013 at 04:47


Ah, so you're saying it is counterproductive because of the potential for decomposition of the nitric acid?

Well, if a vacuum is used and the column is insulated, I suppose we could circumnavigate those worries. In such a case, would not the column become an asset and improve the purity of the product?

My main concern is, what exactly are the products of a nitric acid, sulfuric acid mixture, what are their boiling points, are any of them azeotropic with nitric acid? Suppose I start with 70% HNO3 and 98% H2SO4.
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[*] posted on 24-9-2013 at 04:54


Quote:
Suppose I start with 70% HNO3 and 98% H2SO4.

Yes do, the vapour will be of constant comp. with or without a column . . .




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[*] posted on 24-9-2013 at 12:38


When you say vapor, what compounds are you referring to? It seems there are lots of products of a nitric acid (70%)/sulfuric acid (98%) reaction. I am unable to find the properties of all of the products and thus cannot determine whether a column would provide a benefit. I am hoping to determine this scientifically rather than anecdotally.
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[*] posted on 24-9-2013 at 12:45


The do some experiments, with and without a column, and analyze the obtained fractions...

The condensate is what your after, after all. It will be nitric acid, and a very small amount of water, either carried over from the reactants, or from the decomposition of the acid.




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[*] posted on 24-9-2013 at 12:51


If you would like to visit me and help determine the existence and precise amount of every product compound, I would be very grateful. Otherwise, I do not have the knowledge or equipment to do so.

Edit:

http://www.jacobs.com/uploadedfiles/Products/Chemetics/Nitri...

In this document, it is said in the third paragraph that adding sulfuric acid (50% weight) "completely" eliminates the azeotrope. It is said in the fifth paragraph that a distilling column is then used to produce up to 99% pure nitric acid.

They may be using the column to separate leftover acids from the pure nitric acid rather than to gradually purify the nitric acid. However, their language "further concentrated" referring to the increase from 80% to 99% nitric acid in the upper portion of the column seems to imply that the column employs fractionation.

[Edited on 24-9-2013 by malford]
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[*] posted on 19-10-2013 at 11:50


I found the following data (similar to malford post):

- Nitric acid of 68% azeotrope can be eliminated with min. 50% H2SO4 at 1:1 volume (1L az. HNO3 + 1L min. 50% H2SO4) by fractional distilling the nitric acid at 83C to obtain concentrations up to and over 99%, and then recycling the H2SO4 by boiling off the water to get high conc. again

- Magnesium nitrate anhydrate (dec. 330C) can be used in similar manner mixed by equivalent weight (1kg&1L) to eliminate the azeotrope. Because of the low decomp point, vacuum fractionation and water bath heating is preferred method

Questions:

- Could HNO3 be dehydrated with CaSO4?
- Could H2SO4 be dehydrated with CaSO4?

Off-topic for nitric acid:

-HNO3 can be manufactured by calcium or magnesium nitrate, at 650C or 330C, and an oxide is leftover and NO2 gas is released, which forms HNO3 upon water.
-CaO can be reacted to form CaOH with water
-MgO can be reacted with NaOH, in where Mg(OH)2 is formed and precipitated as solid(practically insoluble), and Na will instantly scavenge new OH group from water, and no NaOH is consumed in the transfer process
-Mg(OH)2 can be reacted with ammonium nitrate, in which metathesis will form Mg(NO3)2 and ammonia, released as gas upon heating - CaOH applies exactly the same manner in this phase
-The purpose of this transfer process is to eliminate completely the consumption of sulfuric acid to obtain HNO3

-NO2 forms nitric acid in water, and one NO group is released in air. Therefore, one should use long plastic or steel cylinder, for ex. 200mm diameter and 1500mm high to scrub the NO2, because NO is slightly heavier than air, and it stays in the cylinder and re-oxidizes to NO2, which condenses back to the water, and by this method, the recovery rate of NO2 gas can be increased over 95%. This produces max. 68% HNO3 without pressurizing the scrubber, which can be concentrated as mentioned before.
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[*] posted on 14-11-2013 at 15:23


Here is an alternate perspective which may be justified on safety concerns alone (very concentrated acids are dangerous and, at times, their behavior is unexpected).

The idea is not so much focusing on concentrating HNO3, but on raising the 'activity level' of the acid in the particular application. Adding Ca(NO3)2 or Mg(NO3)2 may accomplish this.

A cited example occurs in hydrometallury, where one can significantly raise the 'activity level' of dilute HCl by adding MgCl2 (alternatively, to a lesser extent using NaCl). This is an important tool in this field where one is trying to leach out minerals from ores efficiently and cheaply.

Source: See Hydrometallurgy in Extraction Processes, Vol I, by C. K. Gupta and T. K. Mukherjee, page 15 at <del>http://books.google.com/books?id=F7p7W1rykpwC&pg=PA203&lpg=PA203&dq=FeCl2+%2B+O2+%3D+FeO(OH)+%2B+FeCl3&source=bl&ots=fi WLs05y8f&sig=mi-pV94woVj7JABKBB zLZcqbEwM&hl=en&sa=X&ei=ZQgfUeq7BIi50AGynoDoBQ&sqi=2&ved=0CFAQ6AEwBA#v=snippet&q=Magnesium%20chloride%20MgCl2&f=false</ del> http://books.google.com/books?id=F7p7W1rykpwC&pg=PA15 .

where the author cites data confirming that a 2M HCl in 3M CaCl2 or MgCl2 (or FeCl3) behaves like 7M HCl.


[Edited on 14-11-2013 by AJKOER]

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: del; fixed link?]

[Edited on 20.11.13 by bfesser]
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[*] posted on 15-11-2013 at 05:43


Quote: Originally posted by AJKOER  

where the author cites data confirming that a 2M HCl in 3M CaCl2 or MgCl2 (or FeCl3) behaves like 7M HCl.


[Edited on 14-11-2013 by AJKOER]


That link get truncated when someone else uses it.

Can you cite these data?




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[*] posted on 19-11-2013 at 07:08


OK, I actually check this messy link and it does work. The 'trick' is to copy and paste it. However, one must copy the entire link text including the last space and period.

To be honest, there is precious little more data then I presented. However, there is more research (some advanced) on the topic of activity level. I would also not consider myself an exceptional source on this topic, but I have taken a course in Numerical Analysis and have source books. This latter discipline being applicable as the actual calculations of activity levels in practice could involve the solution of a system of non-linear equations. Apparently, there are companies that consult for industrial chemical producers by solving these numerical problems.
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[*] posted on 20-11-2013 at 08:42


It works for you (but not me), probably because it's cookie based.

Personally I'm sceptical about acid activity increasing by adding a salt of the conjugated base to it. Even HCl + H2O < === > H3O+ + Cl- is an equilibrium (albeit with a very high Ka), so stuffing the solution with extra Cl- should push the equilibrium a bit to the left.

Subjectively I've also experienced that acids are less reactive to metals in solutions of high ionic strength (all other things being equal). I have no clear empirical evidence for it though.

[Edited on 20-11-2013 by blogfast25]




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[*] posted on 20-11-2013 at 09:12


AJKOER, spaces cannot be used in a URL. Your browser is likely auto-correcting your copy-pasted link from history. I replaced the link in your post; please let me know if it's not in alignment with your intent.



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[*] posted on 20-11-2013 at 15:35


Quote: Originally posted by blogfast25  
It works for you (but not me), probably because it's cookie based.
It's Google Books, which is known to have issues crossing jurisdiction.
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[*] posted on 18-4-2014 at 04:18


I have lots of 40% nitric acid can I simply mix it with 98%H2SO4 to distill more than 90% concentration HNO3
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