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Author: Subject: Is it possible to produce calcium metal?
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[*] posted on 2-7-2013 at 14:21
Is it possible to produce calcium metal?


Hello to everyone,
I would like to know if it is possible to make calcium metalic at home through thermite method. I imagine to make a mixture of magnesium powder and calcium oxide.
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[*] posted on 2-7-2013 at 14:43


Probably possible since some guys made Na with NaOH and Mg via termite too. Caution should be taken.
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[*] posted on 2-7-2013 at 18:01


think electrolysis is the way to go on that one. look around for electrolysis of molten calcium chloride. Cl gass not too fun to be around though, so plan and play carefully.
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[*] posted on 2-7-2013 at 18:06


Quote: Originally posted by violet sin  
think electrolysis is the way to go on that one. look around for electrolysis of molten calcium chloride. Cl gass not too fun to be around though, so plan and play carefully.


at 772 degrees celsius he might as well use a KCl/NaCl mixture to get more interesting metals
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[*] posted on 2-7-2013 at 18:17


a propane torch will melt it... not that hard, and the Ca isn't a highly flammable liquid/gas at that temp either...

*at least my propane torch melted the CaCl2 I had.*

[Edited on 3-7-2013 by violet sin]
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[*] posted on 2-7-2013 at 18:24


calcium metal in water will not explode either like sodium or potassium i just saw a video on youtube.
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[*] posted on 2-7-2013 at 18:27


Aluminothermic reduction of calcium oxide is reported to give poor yields; it is supposed to work better for barium and strontium. If you were to try it you would need a furnace under high vacuum. Magnesium has a higher vapor pressure than the desired product and will not work here. Small quantities might be prepared by thermal decomposition of calcium azide.

See Brauer starting on page 922: http://library.sciencemadness.org/library/books/brauer_ocr.p...

The preparation given in Inorganic Syntheses Volume 6, "Calcium Metal Powder," indicates that sodium can reduce calcium chloride. Lithium may work as well.

I strongly suspect that under your current circumstances you do not have the equipment and technique to successfully, much less safely, isolate metallic calcium using one of these methods. Please read the suggested references.




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[*] posted on 2-7-2013 at 19:23


Quote: Originally posted by August  
thermite method. I imagine to make a mixture of magnesium


No.
Aluminum or aluminium, and 1200C at 20 microns. I don't think a few grams would be that difficult, just not free. Not worth it unless you're also making some UF4, UO2 etc.

[Edited on 3-7-2013 by S.C. Wack]




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[*] posted on 3-7-2013 at 02:07


Thank you guys
Well, unfortunately nowadays I do not intend to try the electrolysis of molten calcium chloride because I think it is a little bit dangerous (as Polverine already commented) but in the future I will try it.
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[*] posted on 3-7-2013 at 04:51


Quote: Originally posted by S.C. Wack  

Aluminum or aluminium, and 1200C at 20 microns. I don't think a few grams would be that difficult, just not free. Not worth it unless you're also making some UF4, UO2 etc.

[Edited on 3-7-2013 by S.C. Wack]


What do you mean? CaO cannot be reduced by Al (or Mg, or C), not at "1200 C" either.

See Ellingham Diagrams to determine which binary compounds can be reduced by which elements:

http://www.doitpoms.ac.uk/tlplib/ellingham_diagrams/interact...

The (ΔG, T) line of Al2O3 lies well above the CaO line over the entire range of temperatures. This is true also of Mg and C.

And the trick of pulling a vacuum isn't going to work here either because Ca has a high BP (1484 C, Wiki).

Reduction of CaCl2 with Li, Na or K maybe just about possible. Standard Enthalpies of Formation for CaCl2, -796 kJ/mole and LiCl, -408 kJ/mol suggest that.

Electrolytic methods are required. Probably electrolysis in watery solution of a calcium salt using mercury as cathode and subsequent distilling off the mercury from the formed amalgam in heat and vacuum is the easiest [cough!] at the home level.



[Edited on 3-7-2013 by blogfast25]




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[*] posted on 3-7-2013 at 13:02


Aluminothermic reduction of calcium oxide in vacuum furnaces to produce calcium is a major industrial method of production, operating on a scale of some thousands of tonnes per year. This is not some crazy hypothetical method. But neither is it well suited for small scale operations in a crudely equipped lab.

[Edited on 7-3-2013 by Polverone]




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[*] posted on 3-7-2013 at 16:06


Quote: Originally posted by blogfast25  
What do you mean? CaO cannot be reduced by Al (or Mg, or C), not at "1200 C" either.


Direct your calls of bullshit on the not-unknown author's writing to the editors of the Journal of the Electrochemical Society. They will probably point out that it was "presented at the Eighty-ninth General Meeting held at Birmingham, Ala., April 12, 1946, B. S. Hopkins presiding."

His company was deeply involved with the atomic program er Signal Corps for 20 years, from the very first bomb, so I guess the product was OK; it was also bought by chemical supply houses.




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[*] posted on 3-7-2013 at 16:33


<em>'I hate it when mommy and daddy fight!'</em>

<strong>blogfast25</strong>, <strong>S.C. Wack</strong>, who wants to be mommy?




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[*] posted on 4-7-2013 at 04:31


Well, I stand thoroughly corrected. An EPA paper describes the conditions at a Pfizer plant as 13 Pa, 1200 C and 24 h reaction time. 99 % purity of the metal after breaking vacuum with argon. Amazing that full separation between Al and Ca is achieved.


Here's an interesting real life cold war spook story, involving calcium (electrolytic, in this case), uranium and boron-10:

https://www.cia.gov/library/center-for-the-study-of-intellig...



[Edited on 4-7-2013 by blogfast25]




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[*] posted on 4-7-2013 at 05:58


It's the same plant, or at least at the same site.

BTW Loomis (yes, that one) got $13.8 mil worth of Pfizer stock, (1961 dollars) out of Pfizer for that, and the chairman got to keep his job.

[Edited on 4-7-2013 by S.C. Wack]




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[*] posted on 4-7-2013 at 06:11


See my post here:

http://www.sciencemadness.org/talk/viewthread.php?tid=935#pi...

For some more details on electrolysis method.




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[*] posted on 4-7-2013 at 06:36


S.C.: yes, the same site.

BA: I can't find an abstract to that German paper, it's not the amalgam method, by any chance?

Also CaCl2 + 2/3 Al === > Ca + 2/3 AlCl3

... could be considered (as you mentioned) because of AlCl3 volatility. Heating a very dry mixture in a stream of argon perhaps? CaCl2 has some volatility too of course.

Perhaps excess CaCl2, heated to just over MP (thus also over Al MP), with Argon removing AlCl3 vapour? Molten Al would probably sink in molten CaCl2, molten Ca would float.



[Edited on 4-7-2013 by blogfast25]




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[*] posted on 4-7-2013 at 10:16


aluminium and calcium oxide has been used for this, but i dont know at what temperatures
my source of this is a book on elements

small amounts of chlorine gas is no problem if you have ammonia




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[*] posted on 4-7-2013 at 13:02


I don't see ionic chlorides making AlCl3; it's too covalent to be favorable, and the reaction rate at lower temperatures (below the melting point of CaCl2) would be very slow. Even the vapor pressure of CaCl2 at the melting point is surprisingly high, and probably higher than the (reaction limited) AlCl3 vapor pressure.

It's noteworthy that chlorides flux molten aluminum, so you don't have to worry much about oxides interfering. That said, I've never noticed fumes from melting the two together which couldn't be attributed to fumes from the molten salt and fire combination alone.

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[*] posted on 5-7-2013 at 05:06


Quote: Originally posted by 12AX7  
I don't see ionic chlorides making AlCl3; it's too covalent to be favorable, and the reaction rate at lower temperatures (below the melting point of CaCl2) would be very slow.


Yes, that's what I think too. ΔG is likely to be too positive and the equilibrium constant thus far too small to be exploited, with too little elemental Ca in the melt. The resp. standard enthalpies of formation for CaCl2 and AlCl3 for instance are - 796 and - 706 kJ/mole (both NIST).

The only reference to the reaction I've found is a 'FORD chemical compatibility' page warning that molten CaCl2 is corrosive to aluminium.


[Edited on 5-7-2013 by blogfast25]




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[*] posted on 7-7-2013 at 07:28


Apparently MgCl2 is rather corrosive as well; I recall reading someone was designing an electrolysis apparatus and had to build the thing out of inconel or something like that! I do get the impression MgCl2 is.. less ionic, more of a Lewis acid, than its neighboring compounds.

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[*] posted on 24-9-2013 at 12:37


Quote: Originally posted by Polverone  
Aluminothermic reduction of calcium oxide in vacuum furnaces to produce calcium is a major industrial method of production, operating on a scale of some thousands of tonnes per year. This is not some crazy hypothetical method. But neither is it well suited for small scale operations in a crudely equipped lab.

[Edited on 7-3-2013 by Polverone]


Huh?? According to the Ellingham diagram reduction of CaO is less favorable at 1200°C than Al2O3, so this will never happen.
Electrolysis of CaCl2 at 800°C should work.
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[*] posted on 24-9-2013 at 18:25


If you intend to reduce a calcium salt, it may be much easier to use the chloride salt.
Calcium oxide has fairly high entropy of formation, due to higher lattice energy, and also not unlikely due to some mild covalent character between the calcium and oxide ions. What many may not realize here is that reduction potentials can greatly change depending on the anion.

Metallic sodium could easily reduce molten CaCl2. Aluminum certainly would not be able to reduce it. The reactivities of these 3 metallic elements would probably be the reverse if it was the oxide rather than the chloride.

To give you some idea of the general trends:

6 KOH + 2 Al --> Al2O3 + 6 K + 3 H2

K + NaCl --> KCl + Na

AlCl3 + 3 Na --> 3 NaCl + Al

CaCl2 + 2 Na --> 2 NaCl + Ca


Aluminum is not really as powerful of a reducing agent, it just has a strong affinity for oxygen.

While this may seem inexplicable, it can actually be understood in terms of Lewis "acidity" and "basicity" of various ions. Bare Al3+ ions are actually quite acidic, whereas O2- ions are basic. So the bonding has a very covalent character.



[Edited on 25-9-2013 by AndersHoveland]
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[*] posted on 24-9-2013 at 22:28


Quote: Originally posted by metalresearcher  
Huh?? According to the Ellingham diagram reduction of CaO is less favorable at 1200°C than Al2O3, so this will never happen.
Never? According to that logic, a vapor pressure of calcium as a result of a steady-state partition between two sides of a reaction can't happen either. But it does The reaction works because Ca vapor is continuously removed by vacuum. See the section in Kirk-Othmer titled "Calcium and Calcium Alloys".
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[*] posted on 25-9-2013 at 00:56


Barium is much easier to vaporize than calcium, just as potassium is much easier to distil than sodium.
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