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Author: Subject: Metallic Strontium
clearly_not_atara
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[*] posted on 27-6-2015 at 10:41


Why not just reduce it with potassium? Assuming you're familiar with producing K, SrCl2 + K >> Sr + KCl should be very favorable.
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[*] posted on 27-6-2015 at 12:37


Quote: Originally posted by clearly_not_atara  
Why not just reduce it with potassium? Assuming you're familiar with producing K, SrCl2 + K >> Sr + KCl should be very favorable.

Good idea but at which conditions? It's not possible with aqueus SrCl2 solution.


[Edited on 27-6-2015 by uzaymaymunu]




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[*] posted on 27-6-2015 at 12:48


I doubt that would work, potassium's greater volatility will negate the advantage of the small 'free energy', making separation nearly immposible.



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[*] posted on 27-6-2015 at 13:19


ΔH<sub>f</sub><sup>0</sup> for KCl and SrCl<sub>2</sub> resp. – 437 kJ/mol and – 829 kJ/mol (both NIST Webbook values).

SrCl2 + 2 K === > Sr + 2 KCl, ΔH<sub>reaction</sub><sup>0</sup> = - 45 kJ/mol. Entropic effects notwithstanding, that’s not promising ('not favourable'). And with K more volatile than Sr, heating isn't a solution here, as MM points out.

[Edited on 27-6-2015 by blogfast25]




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uzaymaymunu
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[*] posted on 27-6-2015 at 16:49


" The metal can be prepared by electrolysis of the fused chloride mixed with potassium chloride, or is made by
reducing strontium oxide with aluminum in a vacuum at a temperature at which strontium distills off. "
Sauce: CRC Handbook of Chemistry and Physics

Why chlorides, why not hydroxides?
And which ratio SrCl2/KCl should we prepare?


[Edited on 28-6-2015 by uzaymaymunu]




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blogfast25
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[*] posted on 27-6-2015 at 17:07


Quote: Originally posted by uzaymaymunu  

And which ratio SrCl2/KCl should we prepare?




A eutectic mixture: lowest possible melting point (assuming there is an SrCl2/KCl eutectic).

[Edited on 28-6-2015 by blogfast25]




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[*] posted on 27-6-2015 at 17:57


Referring to a previous page, here's the phase diagram:
https://www.sciencemadness.org/whisper/viewthread.php?tid=62...

Here's some more detail on strontium electrolysis:

Science Abstracts.png - 31kB electrolytic strontium.jpg - 116kB (pg. 62)

For whatever reason, it looks like temperatures given are wrong/sloppy in this reference.
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[*] posted on 3-7-2015 at 17:32


The electrochemists may well agree with you Blogfast, Hg has a large overpotential for H production. But I'd stay far away from any aqueous solutions

I have a deep-seated distrust of any but a well equipped lab being able to quantitatively remove Hg from a metal lattice. Boiling and condensing Hg in standard Pyrex is old hat, that's what all of our Hg diffusion pumps did back when those were routinely used on vacuum lines. For me, it's a more about how would you know when you had succeeded? Just achieving constant weight, wouldn't mean all of the Hg was out, maybe it was just not accessible. Elaborate, really extreme attempts to remove Hg from black P (catalyzed to form by it and copper-coated steel rods) fails, always.

The industrial method is, as noted, SrO and Al done at high vacuum in long heavy-walled steel retorts. Reactants and heat at one end. At a particular temp. zone, the Sr vapor will condense. It's very difficult for most to engineer at home.

The Downs cell with a molten Sr salt eutectic is the route I'd try at home. It is what Westinghouse called a "Type 2" fused bath electrolysis. In Type II the molten metal is deposited on a cathode that is sufficiently chilled to collect the metal as a solid from the molten bath. Atmosphere control will be paramount in any method.

This is a far more difficult task than making sodium or potassium. That is generally true for group II elements. At one point I was convinced that I'd find a way to make shiny barium metal. I no longer believe that I will succeed.

Does your country allow importation from China? They'll sell you nearly anything. Of course e-Bay, GalliumSource, Metallium , etc. will sell you Sr if your import people aren't ball-breakers (and some countries really are!). But if you are intent on the manufacture, prepare yourself for a work and time-intensive project.





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[*] posted on 3-7-2015 at 19:27


Quote: Originally posted by Dan Vizine  
.
At one point I was convinced that I'd find a way to make shiny barium metal. I no longer believe that I will succeed..


Sorry to hear that DV. Your glovebox was looking great and you were showing every indication of solving problems as they arose.
The question then is, has anyone ever produced shiny barium samples? Yours were the brightest that I have seen.
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blogfast25
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[*] posted on 4-7-2015 at 07:05


Quote: Originally posted by Dan Vizine  
Just achieving constant weight, wouldn't mean all of the Hg was out, maybe it was just not accessible.


Hmmm... the method is still used, albeit rarely now, for gold extraction for example.

There's an old sample of Ca metal in the British Museum, prepared all these decades ago with the aqueous amalgam cathode method. I'd have a go at that, if I had enough mercury.




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