metalresearcher
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Getting Calcium metal by thermite reaction with Al ?
I heard in a periodic video on the Youtube channel of Martyn Poliakoff (most of you will probably know him) how the Ca 48 isotope is made.
https://www.youtube.com/watch?v=CodBk7xewRk
He tells that the metal is finally reduced by aluminothermic reduction of CaO.
Is this aluminothermic reduction (of 'ordinary' calcium, not Ca-48) really possible for the amateur chemist, or only in the very specialstic Dubna lab
with high-tech equipment ?
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Σldritch
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Think i remember seeing something on that here...
Quick search: http://www.sciencemadness.org/talk/viewthread.php?tid=15069 Remember to search!
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Godrick VanHess
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Yes, Al can and will reduce CaSO4. I have had some success doing this reaction in a paper tube buried in sand which keeps the product in a solid lump.
The Ca tends to be small beads distributed through the solid mass. Not exactly practical for my applications but it is "doable" .
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aga
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Mmmm. Maybe calcium hydroxide will go all thermite-y with Mg.
Not tried that one yet.
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Deluxbert
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Dont think so
Looking at the enthalpy of formation says:
For Ca(OH)2 −987 kJ·mol-1
For MgO −601.6 ± 0.3 kJ·mol-1
For NaOH −427 kJ·mol-1
For Na2O -416 kJ/mol-1
Mg works for NaOH to MgO and Na
Al2O3 −1675.7 kJ·mol-1
Thats the reason why you cant reduce Al or Mg or Na with C
CO2 −393.5 kJ·mol-1
That Al2O3 is just way to stable of a compound so its usually the thing ending up with the oxygen after a reaction.
Ofc its more complicated but looking at it like this says it shouldnt work with Mg.
Like this you can roughly tell which thermites will work and estimate the energy released.
For example
CuO −156 kJ·mol−1
Fe2O3 −824.2 kJ/mol
See that the energy released can be bigger because the difference between the entropy of CuO and Fe2O3.
In this case CuO is the bigger bang as one can tell in trying.
[Edited on 23-3-2018 by Deluxbert]
[Edited on 23-3-2018 by Deluxbert]
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Metacelsus
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Quote: Originally posted by Godrick VanHess  | | Yes, Al can and will reduce CaSO4. I have had some success doing this reaction in a paper tube buried in sand which keeps the product in a solid lump.
The Ca tends to be small beads distributed through the solid mass. Not exactly practical for my applications but it is "doable" .
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Really? I have ignited Al and CaSO4, but I didn't observe any Ca metal. To be fair, I wasn't using excess Al and maybe you were. I was just trying to
see if the mixture would burn. The end product contained lots of sulfides, judging by smell.
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MrHomeScientist
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I also find it unlikely that calcium can be produced from aluminum. Ca is more reactive than Al!
Following the link posted in the second post in this thread, blogfast also says no:
| Quote: Originally posted by blogfast25 | Sigh… another wild goose chase by those unwilling to consider condition 1: Is It Possible, Thermodynamically?
CaO HoF = - 635 kJ/mol
Al2O3 = - 1676 kJ/mol
CaO + 2/3 Al --- > Ca + 1/3 Al2O3, Heat of Reaction = + 635 – 1/3 1676 = + 76 kJ/mol, reaction is (strongly) endothermic and
unless you have a trick up your sleeve to force the equilibrium from left to right nothing will happen.
Calcium is in fact occasionally used where aluminium fails as an oxide reducing agent, the technique is then called calciothermy. V2O5 has been
reduced with Ca for instance and early production of metallic U (from UO2) also used Ca (now Mg with UF4). Drawback of Ca is that CaO has an insanely
high MP, not desirable in most oxide reductions.
One potential trick is to heat a mitxure of CaO and Al to very high temperature under vacuum: Ca has a lower BP (1,484C) than Al (2,519C) and the Ca
could thus in (unsubstantiated) theory be selectively boiled off. Good luck with that!
Ca is produced electrochemically because it’s the only PRACTICAL way.
One could of course envisage various reducing agents in very extreme conditions and never be able to bench test it because the conditions required.
CaO + C --- > Ca + CO is a possibility because at very high temperature (x,000 C) the volatile Ca and CO drive the equilibrium to the right, IF
you can successfully remove them form the mix. That would involve probably high vacuum on top of the high temperatures. Again, bonne chance!
The communications published above are likely by bullshitting freewheelers…
[Edited on 16-12-2010 by blogfast25] |
He's the resident thermite expert so I tend to believe him!
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metalresearcher
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| Quote: Originally posted by Godrick VanHess | | Yes, Al can and will reduce CaSO4. I have had some success doing this reaction in a paper tube buried in sand which keeps the product
in a solid lump. The Ca tends to be small beads distributed through the solid mass. Not exactly practical for my applications but it is "doable" .
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Indeed, it will, but to CaS and Al2O3 and the first will react with moisture to stinky H2S. No Ca metal will be formed as it is more reactive than
Al.
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Deluxbert
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https://youtu.be/KGMKlsG9_1o?t=592
It does seem to work here. (Maybe Al blobs instead?)
But terrible as expected. Probably worse than NaOH+ Mg
Also i read Ca Al alloys will form.
I will try it simply. Gonna need to look if I have good quality CaSO4
[Edited on 23-3-2018 by Deluxbert]
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phlogiston
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Canadianchemist did not demonstrate that he obtained calcium metal.
In this particular video, what he did was test the pH after dumping the CaSO4+Al reaction products into water. It tested alkaline, which is not
surprising.
Among the expected reaction products are CaS and Al2S3.
Both will react with water. Wikipedia:
| Quote: | Calcium sulfide decomposes upon contact with water, including moist air, giving a mixture of Ca(SH)2, Ca(OH)2, and Ca(SH)(OH).
CaS + H2O → Ca(SH)(OH)
Ca(SH)(OH) + H2O → Ca(OH)2 + H2S |
[Edited on 24-3-2018 by phlogiston]
[Edited on 24-3-2018 by phlogiston]
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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symboom
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Off topic but i finally found a great process to make calcium metal
Henri Moissan first isolated pure calcium in 1898 by reducing calcium iodide with pure sodium metal:[3]
CaI2 + 2 Na → 2 NaI + Ca
1898
Sodium could be substituted with lithium which is even easier to come by the only problem is calcium iodide is hydroscopic
Calcium iodide can be formed by treating calcium carbonate, calcium oxide, or calcium hydroxide with hydroiodic acid:[4]
CaCO3 + 2 HI → CaI2 + H2O + CO2
Calcium iodide slowly reacts with oxygen and carbon dioxide in the air, liberating iodine, which is responsible for the faint yellow color of impure
samples.
2 CaI2 + 2 CO2 + O2 → 2 CaCO3 + 2 I2
Calcium forms interesting compoundsWhen strongly heated in air, calcium bromide will react with oxygen to produce calcium oxide and bromine:
2 CaBr2 + O2 → 2 CaO + 2 Br2
In this reaction the oxygen oxidizes the bromide to bromine.
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aga
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Pretty sure this would be an Entropy driven reaction, although i am too lazy/drunk to look it up/calculate before posting.
@symboom: expanding your sig does not add any weight to anything.
Perhaps (not sure if this will help) posting even one experiment you have done might.
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S.C. Wack
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Oh hi
and again
http://www.sciencemadness.org/talk/viewthread.php?tid=24889
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symboom
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I found the wikipedia page and thought that was a process
That could be done
Aga so you know
Many links on my singnature are to help others or to help me keep track of the most relavant experiments i have or will have done.
Shown
Copper peroxide
Zinc peroxide
Lithium peroxide
Experiments with oxone
Simple experiments
Some unfortunatly i cant need lab space
Maybe ill make a floating hot air ballon lab
to get the lab space i need jk
Need vacuum rated glassware
For H2O2
Ascodole waiting on tdeps result
not wanting a friendly visit again also the reason for no current experiments or experiments with complex salts.
I thought i would work on a project that was more meaningful after U2U with a few members and a bigger project that could help more members.
Currently projects
Just plant chemistry such as limonene extracting and stuff things every one has already done
And starting a lab or at least cost analysis of two different states
For now
Also i try to remove my signature after i post so it only shows up once on the page
Also this spammer os the one using our words against us
Quote:
Very recently started new project
claudiaem4
Just started fresh protrude:
http://sonja.web1.telrock[dot]net
We dont need no damn hyperlinks added [dot] to remove hyperlink spam
[Edited on 16-6-2018 by symboom]
Mods may want to watch for this
What was probally used
thought i would work on a project that was more meaningful after U2U with a few members and a bigger project that could help more members.
[Edited on 16-6-2018 by symboom]
[Edited on 16-6-2018 by symboom]
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Texium
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Thread Moved
27-11-2023 at 12:22 |
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