plante1999
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failed reduction of Na3PO4 with MgAl
Today I made MgAl aloy 10g cost my 10$! to try to reduce Na3PO4 to Na3P with stocheimetric ratio of MgAl / Na3PO4 ratio but the termite like reduction
does not worked , even with KClO3/Sucrose starter, In fact it cost my 10$ for nothing. I was attempting to make Na3P... Wath does I have done wrong?
I never asked for this.
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neptunium
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did you try under vacuum or argon ? and heat it up ...a lot
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blogfast25
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Quote: Originally posted by plante1999  | | Today I made MgAl aloy 10g cost my 10$! to try to reduce Na3PO4 to Na3P with stocheimetric ratio of MgAl / Na3PO4 ratio but the termite like reduction
does not worked , even with KClO3/Sucrose starter, In fact it cost my 10$ for nothing. I was attempting to make Na3P... Wath does I have done wrong?
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Why use an Al/Mg alloy?
I tried thermite style reduction of Ca3(PO4)2 with Al powder and it failed. I believe, for orthophosphates, the dissociation energy for:
Na3PO4 === > 3 NaO + ½ P2O5
… is far too high to get a self-sustaining reaction.
With sodium metaphosphate, (NaPO3)6 - see ‘Calgon’, reaction is possible but with sustained external heating and it produces phosphorus, not
sodium phosphide. See the phosphorus thread.
At $10 for 10 g you're shopping badly.
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plante1999
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MgAl is more reducing than bare Al.
Magnesium is a realy rare metal here it is realy pricely! I finnaly started the mixture with NaClO3/MgAl starter , it burned realy realy hot making a
yellow gas, it was looking more like a smoke device than a termite reaction... It maked a white solid residu with a smell of cheap zinc in HCl.
[Edited on 17-12-2011 by plante1999]
[Edited on 17-12-2011 by plante1999]
I never asked for this.
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blogfast25
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| Quote: Originally posted by plante1999 | MgAl is more reducing than bare Al.
Magnesium is a realy rare metal here it is realy pricely! I finnaly started the mixture with NaClO3/MgAl starter , it burned realy realy hot making a
yellow gas, it was looking more like a smoke device than a termite reaction... It maked a white solid residu with a smell of cheap zinc in HCl.
[Edited on 17-12-2011 by plante1999]
[Edited on 17-12-2011 by plante1999] |
Two myths for the price of one.
The difference in reducing power between Al and Mg isn’t all that great. Mg has also the disadvantage of having an oxide with an even higher MP than
alumina: in pyrometallurgy (which is where these reducing agents are used, among other things) that’s not good. But you can use as powerful a
reducing agent on the salt of an oxoacid as you want: if you can’t get the salt to appreciably dissociate into its base forming oxide and its acid
forming oxide, you’ll never be able to reduce the latter!
You can pick up large amounts of Mg powder (every grade under the sun) for next to nothing at pyrosites.
You've been making phosphorus by the sound of it. That burns with a bright yellow flame and the white smoke is P2O5...
[Edited on 17-12-2011 by blogfast25]
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plante1999
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I was thinking that Mg which is a alkaline earth metal would be more reducing than Al!!! But MgAl alloy is easy to make fine powder , this is not a
myth , it is realy long to make Al powder... I thing blogfast have found what appened. But I want to make Na3P to make phosphine for a demonstration
of pyrophoric compound!
[Edited on 17-12-2011 by plante1999]
I never asked for this.
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blogfast25
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What a given salt of an oxoacid will be reduced to (or not) depends on some factors.
Take a simple example:
CaSO4 + 8/3 Al === > CaS + 4/3 Al2O3 (R.1)
… proceeds. It does not proceed to:
CaSO4 + 8/3 Al === > Ca + S + 4/3 Al2O3 (R.2)
Because the ΔG of R.1 is more negative than the ΔG of R.2 and that is largely due to the high heat of formation of CaS. That’s is not the
case for Na3P.
DON'T try and make phosphine: it's a DARWIN AWARD situation unless you're highly equiped!!! NO KIDDING!
Want a pyrophoric compound? Try silane: reducing SiO2 with Mg:
SiO2 + 3 Mg === > Mg2Si + 2 MgO
Magnesium silicide reacts with dilute acids to form silane(s). These are pyrophoric but not toxic! Phosphine is a killer!
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plante1999
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I did not have more Mg.......
I never asked for this.
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blogfast25
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Nope. A classic mistake. The reducing power of a reducing agent depends on the context its being used in. In the case of the reduction of solid, ionic
compounds (usually metal oxides, chlorides or fluorides) that depends almost solely on the Heat of Formation of the resulting oxide, chloride or
fluoride. Take a generic reduction;
MX + M’ === > M + M’X
The ΔH = HoF(M’X) - HoF(MX), so the higher (more negative) the HoF of M’X the more negative the ΔG of the reaction will be.
In the case of Mg v. Al (for oxides) Mg has a slight edge.
But in the case of fluorides, Mg has a serious edge because AlF3 has a relatively low HoF (it’s not 100 % ionic).
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