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I was trying to make Calcium metal by electrolyzing molten $\ce{CaCl_2}$. I used a stainless steel spoon and a thick steel wire as electrodes. Then I attached them to a power supply. I placed some $\ce{CaCl_2}$ in the spoon and melted with a gas torch. I then placed the steel electrode in the molten pool and gradually pulled it out. A black glassy substance formed on the rod. I ran water over it and it fizzed as I would expect from Calcium metal, however, when it was exposed to air for a period of time it start to "melt" as it absorbed moisture from the air. As I was breaking it off of the electrode, it shattered and I could see that it was the glassy substance all the way through.

I am trying to figure out what I have made. Could it possibly be a mixture of unreacted $\ce{CaCl_2}$ and a small amount of Calcium?

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  • $\begingroup$ Could you clarify, if you used freshly calcined CaCl2 or a wet one? $\endgroup$
    – permeakra
    Commented Mar 2, 2015 at 18:24

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I would hypothesize that the "black glassy stuff" is nothing more than glassified $\ce{CaCl_2}$. Metal is an excellent heat conductor and the liquid $\ce{CaCl_2}$ likely cooled rapidly to form glass when the cold wire was inserted.

Two things could be done to avoid this:

1.) heat the wire before inserting it into the mixture of molten $\ce{CaCl_2}$.

2.) heat the $\ce{CaCl_2}$ well above its melting point.

If you are determined to make Calcium metal it might be worth electrolysing an aqueous solution of $\ce{CaCl_2}$ to evolve the $\ce{Cl2(g)}$ (do this responsibly outside/in fume hood of course as $\ce{Cl2(g)}$ is poisonous.) Calcium Hydroxide should be the result. Evaporating the water will yield solid $\ce{CaOH}$, which should be much easier to electrolize using your method since it has a melting point of 580°C vs. 772°C for $\ce{CaCl_2}$.

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    $\begingroup$ Better yet, just buy"slaked lime", which is $\ce{Ca(OH)2}$. You should be able to find it at home improvement stores. $\endgroup$
    – Ben Norris
    Commented Aug 12, 2013 at 10:54
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Does this sound like what you made: Iron (III) Chloride. Depending on the polarity of the electrode, one constituent of the melt will combine with the material of the electrode, so it sounds like the chlorine combined with the iron in the steel wire.

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    $\begingroup$ It's probably not $\ce{FeCl3}$, which is yellow to green in color $\endgroup$
    – Ben Norris
    Commented Aug 12, 2013 at 10:50
  • $\begingroup$ > Iron (III) Chloride || would brake in gas torch $\endgroup$
    – permeakra
    Commented Mar 2, 2015 at 18:23

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