Sciencemadness Discussion Board - Magnesium Nitrate for WFNA (not practical)

Magnesium Nitrate for WFNA (not practical)

Sulaiman - 26-2-2017 at 06:43

In preparation for making a little more anhydrous HNO₃ I was searching eBay.uk for a suitable nitrate to use with H₂SO₄ drain unblocker,
the best deal seems to be Mg(NO₃)₂ at £6.09 for 1kg inc. p&p.

Previously I have used Na, K, and Ca nitrates, Ca being the best value in terms of moles of nitrate per £,
Mg is even better, and MgSO₄ is a lot more coluble than CaSO₄ so should be better ?

I expect the Mg(NO₃)₂ to arrive in a few days so I will update this when I've actually made the HNO₃

just thought I'd mention this in case anyone else is about to make some HNO₃

and
using calcium nitrate, heat in the bottom of the distillation pot was much greater than at the top, visibly causing lots of NO₂
this time I'd like to try a partial vacuum distillation,
can anyone recommemd an optimal vacuum pressure range to do this, using water near 0^oC for the condenser ?
(e.g. @17mm Hg b.p. = 0^oC = too low)

P.S. this page on nitric acid properties is informative http://nitrogen.atomistry.com/physical_properties_nitric_aci...

[Edited on 26-2-2017 by Sulaiman]

Magpie - 26-2-2017 at 07:58

Quote: Originally posted by Sulaiman

using calcium nitrate, heat in the bottom of the distillation pot was much greater than at the top, visibly causing lots of NO₂
this time I'd like to try a partial vacuum distillation,

Is that high temperature caused by solids laying in the bottom of the flask? If so, strong mechanical stirring should stop this.

Sucking off NO into your aspirator is a loss of yield.

wg48 - 26-2-2017 at 08:15

Quote: Originally posted by Sulaiman

In preparation for making a little more anhydrous HNO₃ I was searching eBay.uk for a suitable nitrate to use with H₂SO₄ drain unblocker,
the best deal seems to be Mg(NO₃)₂ at £6.09 for 1kg inc. p&p.

Previously I have used Na, K, and Ca nitrates, Ca being the best value in terms of moles of nitrate per £,
Mg is even better, and MgSO₄ is a lot more coluble than CaSO₄ so should be better ?

I expect the Mg(NO₃)₂ to arrive in a few days so I will update this when I've actually made the HNO₃

just thought I'd mention this in case anyone else is about to make some HNO₃

and
using calcium nitrate, heat in the bottom of the distillation pot was much greater than at the top, visibly causing lots of NO₂
this time I'd like to try a partial vacuum distillation,
can anyone recommemd an optimal vacuum pressure range to do this, using water near 0^oC for the condenser ?
(e.g. @17mm Hg b.p. = 0^oC = too low)

P.S. this page on nitric acid properties is informative http://nitrogen.atomistry.com/physical_properties_nitric_aci...

The price of Mg nitrate does look attractive but the only one I could find at that price looks like the dihydrate. That has a little less nitrogen (6% with my quick calculation) but than its's almost half the price so still more economical.

But what about the two molecules water per nitrate, does it form an acid sulphate/hydrate. It would be nice if its prefers the hydrated sulphate in the reaction conditions.

Sulaiman - 26-2-2017 at 08:29

Magpie,
yes, I expect that stirring would help, but my diy mantle/stirrer is not yet ready.

wg48
I am hoping that there will be much less NOx generated at the lower temperatures using partial vacuum.

side note: 10 minutes ago I started vacuuming my previous batch of RFNA at c -75 kpag to get WFNA .... results in an hour or so ....
....................................................................................

Oh crap ... I missed the fact that magnesium nitrate is hygroscopic and forms a hexahydrate ... my 1 kg of MgSO₄ may be only 4 moles of nitrate,
I'll cook it down to c600g of anhydrous magnesium nitrate before using it.

I dehydrated my calcium nitrate tetrahydrate, so no excuse for forgetting

________________________________________________
result: ... rubber bungs don't like NO_x / HNO₃

... D'oh ... not my day ... still learning ...

I've gone from nitric acid with a clear yellow colour to a cloudy orange

___________________________________________________
To complete todays cock-ups ... magnesium nitrate hexahydrate cannot be dehydrated to even the dihydrate by heating...
it decomposes
2 Mg(NO₃)₂ → 2 MgO + 4 NO₂ + O₂

One batch of azeotropic nitric acid comming soon ..........

(or maybe I'll keep the magnesium nitrate HEXAHYDRATE for something else and use my stock of Na, K or Ca nitrate)

[Edited on 26-2-2017 by Sulaiman]

macckone - 26-2-2017 at 09:26

Depending on rubber type,
You can actually get nitrated rubber.
Unlikely to be explosive but not good
for the rubber or the yield.

Get glass jointed equipment and
teflon sleeves instead of vacuum grease
for best results.

Sulaiman - 26-2-2017 at 09:32

I was lazy and just stuck a rubber bung in the bottle that I used to store the RFNA.

what pissed me off is that I KNOW that nitric acid attacks rubber :mad:

I've always used glass only setups ... my pathetic excuse for forgetting

[Edited on 26-2-2017 by Sulaiman]

zts16

Sulaiman - 26-2-2017 at 10:03

thanks for moving this ... maybe to detritus is more suitable ! ... please ... I can't bear the embarassment

There is nothing new or useful in this thread ... it deserves 'detritusing'.

[Edited on 26-2-2017 by Sulaiman]

wg48 - 26-2-2017 at 11:18

Oh crap ... I missed the fact that magnesium nitrate is hygroscopic and forms a hexahydrate ... my 1 kg of MgSO₄ may be only 4 moles of nitrate,
I'll cook it down to c600g of anhydrous magnesium nitrate before using it.

[Edited on 26-2-2017 by Sulaiman][/rquote]

I screwed up my calculation your right its probably the hexahydrate. Still a bit cheaper than sodium version per nitrate but a little bit too much water for 68% nitric.

Fulmen - 26-2-2017 at 11:26

Quote: Originally posted by Sulaiman

I'll cook it down to c600g of anhydrous magnesium nitrate before using it.

AFAIK it is virtually impossible to get anhydrous magnesium nitrate. It can in fact be used instead of sulfuric acid for nitration, dehydrated to perhaps mono- or dihydrate.

chloric1 - 23-7-2024 at 10:12

Quote: Originally posted by Sulaiman

Magpie,
yes, I expect that stirring would help, but my diy mantle/stirrer is not yet ready.

wg48
I am hoping that there will be much less NOx generated at the lower temperatures using partial vacuum.

side note: 10 minutes ago I started vacuuming my previous batch of RFNA at c -75 kpag to get WFNA .... results in an hour or so ....
....................................................................................

Oh crap ... I missed the fact that magnesium nitrate is hygroscopic and forms a hexahydrate ... my 1 kg of MgSO₄ may be only 4 moles of nitrate,
I'll cook it down to c600g of anhydrous magnesium nitrate before using it.

I dehydrated my calcium nitrate tetrahydrate, so no excuse for forgetting

________________________________________________
result: ... rubber bungs don't like NO_x / HNO₃

... D'oh ... not my day ... still learning ...

I've gone from nitric acid with a clear yellow colour to a cloudy orange

(or maybe I'll keep the magnesium nitrate HEXAHYDRATE for something else and use my stock of Na, K or Ca nitrate)

[Edited on 26-2-2017 by Sulaiman]

What temperature does magnesium nitrate completely become magnesium oxide? Since now have 40 lbs of calcium nitrate tetrahydrate, I should be able to make MgO from Epsom salts. I want to play with magnesium cements. I already have a blast with white Portland cement, so easy to color!

Precipitates - 23-7-2024 at 17:49

From our wiki:

Magnesium nitrate decomposes at around 330°C+.

For specific details, this magnesium nitrate decomposition paper is quite extensive.

Given the findings of the paper, I'd whack the temperature up to 450°C, or higher, to speed up decomposition (you can't really go too high).

To avoid breathing in any of the nitrogen dioxide fumes produced perform the experiments outside - and in small increments (perhaps not pounds and pounds of it at a time).

Keep heating until there is no further change in mass.

Quote: Originally posted by chloric1

What temperature does magnesium nitrate completely become magnesium oxide?

In the above study, the authors found this to be at around 500°C (773 K).

[Edited on 24-7-2024 by Precipitates]

chloric1 - 31-10-2024 at 08:35

Hopefully magnesium oxide does not attack porcelain crucibles at 500 C because it’s like a matter of using a turrel or even a Meker burner. I hook my burners to BBQ 20 lb propane so fuel last

. I could opt for a using my nickel crucible or hammer a dish from hot rolled steel. I might just try iron just to see if it gets passivated by the magnesium nitrate