For Na and K I know chemical methods (although tedious because of air exclusion from the retort), but these methods don't work at reasonable
temperatures with Ca. CaO or CaCO3 with charcoal requires temperatures over 2000C, but are there other methods ? Tdep - 7-9-2014 at 05:07
There's always other methods, this is chemistry.
Reduction with Al, Mg, Na, K and probably even lithium will work. Amos - 7-9-2014 at 15:44
Calcium oxide or even calcium sulfate can be reduced in a thermite with aluminum or magnesium. I believe that when using calcium sulfate it's a pretty
self-sustaining reaction, should work fine if mixed properly, not sure about the oxide.phlogiston - 8-9-2014 at 00:32
In the calcium sulphate 'thermite', the sulphate is the oxidiser, not the calcium.PHILOU Zrealone - 8-9-2014 at 07:38
CaSO4/Al thermite might be explosive if the mix is too homogeneous!Amos - 8-9-2014 at 07:44
My prediction was that a lot of the calcium sulfate would thermally decompose into sulfur trioxide and calcium oxide; meaning you'd still get at least
some calcium; But I haven't tested it, so maybe more knowledgeable people should step in. metalresearcher - 8-9-2014 at 10:05
I already tried these reactions but no Ca metal is formed. Only CaS as when keeping the residue outdoors it stinks to H2S.
3CaSO4 + 8Al => 3CaS + 4Al2O3
Reaction in moist air:
CaS + 2H2O => Ca(OH)2 + H2SZyklon-A - 8-9-2014 at 14:40
In the calcium sulphate 'thermite', the sulphate is the oxidiser, not the calcium.
Depends on the stoichiometry you use. Generally after (or during) the calcium is reduced, it get partially oxidized by the sulfur.
This works better with calcium nitrate, as the nitrogen oxidizes the calcium slower, and less thoroughly.
Ca(NO3)2 + 6 Mg --> Ca + N2 + 6 MgO.
Also, the nitrate ion is a better oxidizer than the sulfate ion, so use larger Mg mesh - This is flash powder.
I have tried this with potassium and sodium nitrate, both work, but give terrible yields, and very impure products. Metacelsus - 8-9-2014 at 17:44
I doubt the reaction above would be feasible, and, even if it is, it's a waste of Mg. The reaction is equivalent to two steps:
1: Ca(NO3)2 + 5 Mg -> CaO + N2 + 5 MgO
2: CaO + Mg -> Ca + MgO
The second one is the only one that matters. Even if you can get Mg to do the reduction, it's going to be very hard to get the Ca metal out of the
mixture of products.
[Edited on 9-9-2014 by Cheddite Cheese]metalresearcher - 8-9-2014 at 23:53
Does this work ??? I thought, Ca is less 'noble' than Mg so the reaction prefers to go the other way ?
I'll try it.Metacelsus - 9-9-2014 at 06:40
It probably won't work. At best you'll end up with a mixture of Ca, Mg, CaO, and MgO. Mg boils lower than Ca so you can't isolate Ca by reactive
distillation.
I just suggested it as better than the flash powder idea; I didn't say it would work at all.
[Edited on 9-9-2014 by Cheddite Cheese]drwahab - 9-9-2014 at 09:22
I'm not getting viable products either
[Edited on 9-9-2014 by drwahab]Amos - 9-9-2014 at 09:52
Would CaOH work as opposed to CaO? This works just fine with NaOH and Mg.phlogiston - 9-9-2014 at 12:01
Before you try any method, first ask yourself if and how you'd be able to conclusively determine the presence of calcium metal should you get a small
amount of terribly contaminated Ca.
Amos - 9-9-2014 at 14:17
Not sure if phlogiston's question was directed at the original poster or not, but if you got some nodules in the middle, if you cleaned them off and
they readily ignited under a blowtorch and reacted violently with water, those would be 2 pretty good indicators. Especially when you start getting
white calcium hydroxide forming in the water and a white coating on the burning Ca.phlogiston - 10-9-2014 at 00:34
If the yield is low it will be more difficult. He may not find macroscopic nodules of nearly pure calcium in the reaction residue.
Consider that alloys of calcium and magnesium may form, some of which are much more difficult to ignite than either metal alone (for instance the
'non-combustible' AMCa602 alloy, which contains about 2% Ca)
In order to resolve the problem of ignition, non-combustible
magnesium alloys were developed by adding calcium
(Ca).3–5) By adding Ca, which is more reactive than Mg, the
oxidation reaction of Ca occurs and a coating of calcium
oxide is formed on the surface before Mg ignites.
Also, the reaction between calcium and water is not all that violent, and magnesium also reacts with water. The difference in reaction rate is
significant with large nodules of pure metals, but will be difficult to assess with powders of different particle size and intermediate composition
(alloys).
I just meant to say it is worth putting some thought into, or the OP may falsely conclude his methods did not yield any calcium.
[Edited on 10-9-2014 by phlogiston]metalresearcher - 10-9-2014 at 03:02
I just meant to say it is worth putting some thought into, or the OP may falsely conclude his methods did not yield any calcium.
Well, after a CaSO4 + Al reaction I put the residue into dilute HCl sol'n and gas appears which stinks nasty. This is obviously H2S. And that will NOT
be formed when Ca metal or a Ca/Al alloy reacts with water or HCl.
CaSO4 with Mg I have to try yet. Amos - 10-9-2014 at 05:07
Well, after a CaSO4 + Al reaction I put the residue into dilute HCl sol'n and gas appears which stinks nasty. This is obviously H2S. And that will NOT
be formed when Ca metal or a Ca/Al alloy reacts with water or HCl.
CaSO4 with Mg I have to try yet.
The formation of calcium sulfide was more or less guaranteed with this reaction, I was curious to know if there might also be some calcium metal
produced. I would forgo the use of calcium sulfate any further; from the sound of the conversation so far you're most likely just going to end up with
more noxious gases and disappointment. I would myself the magnesium and try the oxide or hydroxide in a well-contained and thermally insolated
thermite reaction so that you might get some good little spheres of calcium should it work.metalresearcher - 10-9-2014 at 11:47
Well, I did a test (actually two tests) but as I expected, I could get no Ca metal. No H2 bubbling appeared when I threw the result into water, see
the clip below.
The reaction was quite relaxed but it did happen with a strong orangish flame due to the Ca ions.
[Edited on 2014-9-10 by metalresearcher]phlogiston - 10-9-2014 at 13:03
When you sprinkle the contents of the second test in water, I hear an occasional brief high pitched sound, especially in the beginning. Like what you
would get when you drop a hot metal particle in water. Perhaps something is reacting. There is one at 3:25, and another at 3:27. It last a fraction of
a second.halogen - 11-9-2014 at 11:33
Well, thermite shmermite.
I was wracking some of my brains, for an analogue of Christe's synthesis of fluorine
Namely, whereas he used a high oxidation state salt of Manganese, and a lewis acid
A low oxidation state salt and a lewis base might effect some transformation into calcium metal
What lewis bases exist, phosphines, trimethylamine is easy enough to produce
that Young oliver Sacks wreaked havoc with the foul substance
but what calcium salt? I do not know of any hypotitanates or
whatever...
But I do know that azides decompose to metals, or sometimes metal nitrIDES if the metal is particularly reactive.
Calcium nitride exists, and if the azide doesn't decompose directly to the metal (in a controlled way - many azides are explosive)?
Then perhaps there is a way to covert the nitride to the metal more easily than one would calcium chloride, for example.
One might compare the heats of formation of aluminum nitride and calcium nitride. Aluminum being available, though electrically generated.
Would that be cheating? Aluminum nitride, by the way, is a wide band gap semiconductor, useful for LED's and high power transistors.
Similarly, boron nitride is exceptionally stable and hard, perhaps the sintering of calcium nitride and calcium boride would produce calcium metal, to
be leached out with a liquid organic amine.
Dan Vizine - 5-10-2014 at 09:10
Calcium metal from thermite?! That is a freaking nightmare scenario. Don't waste your time.
Calcium metal is not even able to be cast like, say, aluminum. You can't melt it in air without losing it unless protective fluxes are used. So,
anything that just might survive the reaction will be very impure.
There is a good reason that calcium is made by electrolysis, that is the easiest industrial way by far. Plus, it's a continuous process, not one done
in batches. Electrolysis of molten CaCl2 is not even easy like sodium (relatively speaking), and separation of CaCl2 and Ca is difficult due to mutual
solubilities. Not an easily performed task at home at all.
The "best" (not good, but best of the rest) alternate preparation is reduction of CaO by Al. The fact is that this eases the temperature requirement a
lot. Instead of 2000 C with carbon, at 1200 C aluminium will do the job. But the rub is isolation. In the patented procedure, a vacuum of 10 microns
is used. It takes a very special reactor to allow these conditions to be met. The product is isolated by distillation in a zone maintained at 680 -
740 C. The reaction time is typically 12 hours. Brauer says aluminothermic reductions give low yields of Ca.
While I applaud the spirit that leads you consider the possibilities, this is not a goal you'll achieve without a lot of good (read: expensive)
equipment and a ton of work. I frequently look to take on challenging element isolations (Cs, Rb, and Th), but I've never felt that I had equipment up
to the task for Ca. Attached is the section from Brauer concerning group II metal preparations/purifications. Can you not simply buy Ca from eBay?
As halogen suggested, preparation via the azides is possible, subject to 1) explosion risks and 2) production of impure metal (and only modest
amounts, as a powder with high surface area.)
Attachment: Group 2 Brauer.pdf (370kB) This file has been downloaded 1345 times
