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j_sum1
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I dropped Na onto reasonably concentrated HCl just a couple of weeks ago.
Behaved remarkably like water.
To answer Pok. Look upthread a bit to see results of an afternoon playing with sodium and filter paper. I only observed the transparency when the
paper was present and acted as a barrier to too much water reaching the metal. But even with only a small puddle of water, I could not reproduce the
result without paper present.
I have seen video footage of potassium forming a clear pellet with water only. So, K seems different from Na.
[Edited on 12-3-2016 by j_sum1]
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Pok
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You are right. I just tried it several times with sodium and the ball looks metallic up to the end and just gets smaller and smaller but never
transparent. The explanation for the different behaviour of K and Na could be the amount of heat released and/or the solubility of NaOH/KOH or the
solubility of K in KOH / Na in NaOH. K is quite soluble in molten KOH whereas Na isn't very soluble in molten NaOH.
Maybe the NaOH separates from the Na in the molten ball thus allowing a better contact between water and NaOH (though I don't know how) so that the
NaOH dissolves more easily in the water. And in the case of potassium the K dissolves in the KOH and as soon as water has contact (through vapourized
water) with the ball, the whole K will be "eaten up" first and the KOH has no chance to dissolve in the water, thus remaining in the ball. I didn't
find anything in the literature (only the reaction with K is explained). What do you think?
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MrHomeScientist
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Seems to me that the reason the other salts he tested don't explode is simply temperature. All the other salts he tried melt at a lower temperature
than NaCl, so despite all being molten I bet they were all at different temperatures. He even noted that NaCl only causes the explosion at higher
temperature. I agree that KCl or NaOH would be interesting to try. Very cool slow motion video at least; I was shocked when the fish tank totally
shattered. Scary!
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j_sum1
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Good point. He's not comparing like quantities.
I like this kind of thing because it reveals that even for seemingly simple stuff (hot things in water) there is always a whole lot more going on than
first appears. We understand a lot less than we think we do.
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Sulaiman
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a related video
maybe the seed of more experiments;
sodium in oil over water https://www.youtube.com/watch?v=ZgAgO6bT49A
In addition to the technique offering a safer and air-free environment for transparent sodium experiments
It could even be a 'safe' classrom demo.
different molar ratios of sodium to water would give different indicator colours, for example.
I don't think I'll try for a while yet, but thought some may find it interesting.
P.S. I ordered a clay extruder as a sodium wire extruder that may kick-start me when it arrives, (from China of course)
I'm just not looking forward to cleaning it 
[Edited on 25-5-2016 by Sulaiman]
[Edited on 25-5-2016 by Sulaiman]
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j_sum1
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Reviving an older thread. If you have not read it then it is worth going from the beginning. Alas the original YT link is broken (edit or wasn't
working when I first posted) but you can still look up thunderf00t's experiments to get a sense of what the fuss is about. I will also link my
experimentation from upthread: link
Some related experiments have been done and reported on recently.
https://www.chemistryworld.com/news/tamed-sodium-in-water-co...
and the YT link, https://www.youtube.com/watch?v=o1nPgGyMo44&feature=yout...
The main modification to the experiment setup:
1. No paper used.
2. Hexanol added to the water instead of paper (reportedly to lower the availability of the water -- "to control the thermodynamics" (although I
think kinetics is probably the word needed here.))
3. Reaction performed in inert argon atmosphere.
4. Alloy or Na-K used. Composition unspecified.
They answer a couple of questions that we have rattled around here:
In no particular order
1. The transparent bead is molten NaOH.
2. The bead is held in place by the leidenfrost effect.
3. The bead crackles and explodes at the end due to thermal shock as it cools.
4. The blue/black of the metal is due to solvated electrons.
5. The reason that Na explodes under normal conditions is due to coulombic explosion caused by charge separation in the reaction.
6. The red-hot glow is from the evolution of heat (ok we knew that.) No mention is made of recalescence.
There were some additional observations made by thunderf00t in his experimentation with potassium -- I must look at these again. He noticed green
potassium gas under some circumstances and also got the reaction to occur fully submerged.
It is nice to have a few questions answered. I still think this is a field ripe for further experimentation. What exactly is the threshold of water
limitation to prevent the coulombic explosion? What happens to Na in a stream of low temperature steam? Why does the transparent bead appear when
paper is used but does not occur in a shallow puddle in a dish?
Oh to have a couple of kilos of Na and a few spare days to play.
[Edited on 22-8-2016 by j_sum1]
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