Sciencemadness Discussion Board

Preparation of Anhydrous Magnesium Nitrate

APO - 9-3-2013 at 15:00

Could Liquid Nitrogen Dioxide dissolve Magnesium and form Anhydrous Magnesium Nitrate? I saw on another forum that that's how Anhydrous Copper Nitrate is made industrially.

Fantasma4500 - 9-3-2013 at 16:52

i dont think it would be a really comfortable reaction to perform in a testtube tbh, or well without great protection.. im quite sure N2O4 would react violently with Mg metal..
i see the reason for using liquid NO2, but why not just use NO2 on some magnesium chippings, and also what would the reason be for the magnesium nitrate anyways? if it would be to drag water out of nitric acid then i think it might be better to use something alike silica gel, which is insoluble, dont know if it would react with HNO3 tho.. doubt it..

AndersHoveland - 9-3-2013 at 19:29

It would depend whether Mg(NO3)2 has any solubility in N2O4. I am not sure that it does. If there is no solubility, it cannot dissolve, and then a protective layer would just form on the surface of the metal preventing further reaction. If there is a reaction, it is likely to be very energetic. Magnesium is a much more electropositive metal than copper.

AJKOER - 10-3-2013 at 06:20

Perhaps a better approach, to quote from Wikipedia (http://en.wikipedia.org/wiki/Nitrogen_dioxide ):

"Conversion to nitrates
NO2 is used to generate anhydrous metal nitrates from the oxides:[6]

MO + 3 NO2 → 2 M(NO3)2 + NO "

So try warming MgO in dry NO2 (note, Mg(NO3)2 decomposes at 330 C).

Here is an alternate embodiment of this path that may yield some anhydrous nitrate. First note on heating at 256 C:

2 Cu(NO3)2 → 2 CuO + 4 NO2 + O2

so if a tube was first packed with Cu(NO3)2, which was directly heated, and then a layer of MgO, which is not directly subject to heat, perhaps some anhydrous nitrate is produced.

Note the oxygen from the Cu(NO3)2 decomposition can also be consumed via:

2 NO + O2 --> 2 NO2

so the best net reaction could be:

2 MgO + 4 NO2 + O2 → 2 Mg(NO3)2

Note, this procedure does not require anhydrous copper nitrate as the hydrate can be carefully heated until red NO2 fumes are apparent and then the layer of MgO added.

Bottom line, the suggested procedure may be able to convert a hydrated nitrate (in the form of Copper nitrate) into an anhydrous nitrate via an established process for the creation of anhydrous nitrates.

[Edited on 10-3-2013 by AJKOER]

blogfast25 - 10-3-2013 at 09:10

This patent should give some clues:

http://www.google.com/patents/US20090189117

One thing's for sure: you can't obtain anhydrous magnesium nitrate as you would anhydrous magnesium sulphate; by simple heating. On heating Mg(NO3)2 hydrate decomposes, like Be(NO3)2 hydrate.

[Edited on 10-3-2013 by blogfast25]

AJKOER - 14-3-2013 at 08:18

Quote: Originally posted by AJKOER  
Perhaps a better approach, to quote from Wikipedia (http://en.wikipedia.org/wiki/Nitrogen_dioxide ):

"Conversion to nitrates
NO2 is used to generate anhydrous metal nitrates from the oxides:[6]

MO + 3 NO2 → 2 M(NO3)2 + NO "

So try warming MgO in dry NO2 (note, Mg(NO3)2 decomposes at 330 C).

Here is an alternate embodiment of this path that may yield some anhydrous nitrate. First note on heating at 256 C:

2 Cu(NO3)2 → 2 CuO + 4 NO2 + O2

so if a tube was first packed with Cu(NO3)2, which was directly heated, and then a layer of MgO, which is not directly subject to heat, perhaps some anhydrous nitrate is produced.

Note the oxygen from the Cu(NO3)2 decomposition can also be consumed via:

2 NO + O2 --> 2 NO2

so the best net reaction could be:

2 MgO + 4 NO2 + O2 → 2 Mg(NO3)2


I believe this procedure will be successful as elsewhere on this forum, I recall reading a report of the accidental formation of anhydrous Aluminum nitrate when NO2 escaped and attacked an Al foil covering.

I would further increase the reactivity of the Magnesium oxide with the creation of MgO nanocrystals prepared from a thermal decomposition of magnesium oxalate powder (see http://www.sciencedirect.com/science/article/pii/S0022369710... ). Magnesium oxalate dihydrate can be prepared as follows:

MgSO4 + H2C2O4 + 2 H2O --> MgC2O4.2H2O (s) + H2SO4

Be careful, the created Sulfuric acid could be very strong depending on the level of hydration. Then, on heating Magnesium oxalate dihydrate (see http://books.google.com/books?id=i9nyvTYBQtAC&pg=PA459&a... ):

MgC2O4.2H2O (s) --Heat 623 to 723 K--> MgO (s) + CO (g) + CO2 (g) + 2 H2O (g)

If so desired, one could have a layer of Magnesium oxalate on top of (or adjacent to) the Copper nitrate, and subject the MgC2O4.2H2O to thermal decomposition first. To implement this, perhaps using a long horizontally placed test tube and selectively heating sections would work.


[Edited on 15-3-2013 by AJKOER]

Motherload - 27-7-2013 at 18:38

I am going to try this unless someone already has and it doesn't work.

To dry methanol ... Anhydrous Ca(NO3)2 and anhydrous MgSO4 is added in molar quantities and agitated.
Mg(NO3)2 is alcohol soluble and CaSO4 isn't.
This is then filtered and alcohol distilled off or just evaporated.