Sciencemadness Discussion Board

Making nitric acid from oxalic acid?

Upsilon - 15-9-2015 at 19:43

This seems too straightforward to be correct - can you really make cheap, easy nitric acid of high purity with oxalic acid and calcium nitrate? If I mix stoichiometric solutions of each together, a double replacement reaction should occur, and the resulting calcium oxalate should precipitate out (it has a solubility of about 7 mg/L), leaving a nitric acid solution. Would this not be possible though, since nitrate has a higher reduction potential than oxalate, causing the nitric acid to just eat up the calcium oxalate?

I'm asking because I'm going to be receiving some oxalic acid in a few days, and I'm trying to find an alternative to my current method of using sulfuric acid on calcium nitrate (calcium sulfate is very poorly soluble but still slightly so, and I'm trying to get the nitric acid as clean as possible without messing with distillation).

DraconicAcid - 15-9-2015 at 20:10

This would only work to give dilute nitric acid, as oxalates will dissolve in acidic solution.

Upsilon - 15-9-2015 at 20:48

Quote: Originally posted by DraconicAcid  
This would only work to give dilute nitric acid, as oxalates will dissolve in acidic solution.


So it's as I suspected then. Looks like I'm sticking with calcium nitrate + sulfuric acid for now.

hyfalcon - 16-9-2015 at 02:09

Have fun cleaning your reaction vessel. Stuff will set up like concrete in a RBF.

Bert - 16-9-2015 at 04:38
Quote:

I'm trying to get the nitric acid as clean as possible without messing with distillation.


Probably your simplest method for high purity is bubbling nitrogen dioxide into chilled water, or better yet, chilled Hydrogen peroxide.

http://m.instructables.com/id/Make-Nitric-acid-The-Complete-...

Of course, the next questions you will ask are going to be on how to get a high CONCENTRATION. Then you're going to be distilling nitric acid anyhow.

Mesa - 16-9-2015 at 09:24

Quote: Originally posted by Bert  

Quote:

I'm trying to get the nitric acid as clean as possible without messing with distillation.


Probably your simplest method for high purity is bubbling nitrogen dioxide into chilled water, or better yet, chilled Hydrogen peroxide.


I thought this gave significant amounts of lower oxides etc. in the final product(isn't that why conc. nitric acid is often coloured red?)

Detonationology - 16-9-2015 at 11:20

Quote: Originally posted by Upsilon  
Quote: Originally posted by DraconicAcid  
This would only work to give dilute nitric acid, as oxalates will dissolve in acidic solution.


So it's as I suspected then. Looks like I'm sticking with calcium nitrate + sulfuric acid for now.


Although CaSO4 is nearly insoluble, an even better option would be to precipitate BaSO4 or PbSO4, which have very minute Ksp values. Not only is Ba(NO3)2 the best candidate chemically IMO, it is quite cheap and accessible.

Detonationology - 16-9-2015 at 11:25

Quote: Originally posted by Upsilon  
Quote: Originally posted by DraconicAcid  
This would only work to give dilute nitric acid, as oxalates will dissolve in acidic solution.


So it's as I suspected then. Looks like I'm sticking with calcium nitrate + sulfuric acid for now.


Although CaSO4 is nearly insoluble, an even better option would be to precipitate BaSO4 or PbSO4, which have very minute Ksp values. Not only is Ba(NO3)2 the best candidate chemically IMO, it is quite cheap and accessible.

Upsilon - 16-9-2015 at 14:10

Quote: Originally posted by Detonationology  
Quote: Originally posted by Upsilon  
Quote: Originally posted by DraconicAcid  
This would only work to give dilute nitric acid, as oxalates will dissolve in acidic solution.


So it's as I suspected then. Looks like I'm sticking with calcium nitrate + sulfuric acid for now.


Although CaSO4 is nearly insoluble, an even better option would be to precipitate BaSO4 or PbSO4, which have very minute Ksp values. Not only is Ba(NO3)2 the best candidate chemically IMO, it is quite cheap and accessible.


I have considered this, but barium nitrate is still quite expensive when compared to calcium nitrate. The cheapest I see on eBay is almost $30 for 500g. I can get 5 pounds of calcium nitrate for half that cost.