2
$\begingroup$

I melted about 2 kg of gallium and put it in a plastic container, in order to make crystals. After letting them grow and extracting them, I let the gallium freeze at the room temperature, which is below the melting point.

However, for some reason there is a small quantity of gallium (10-20 g) that is not freezing after days. I extracted the liquid then froze it in a refrigerator. But if I put it outside again, it melts, so this is not supercooled gallium, a well documented phenomenon.

It behaves like normal gallium with slightly lower melting point, something like a Galinstan eutectic. However this is 99.99% pure gallium (that was fully solid) and I am pretty sure that I never contaminated it...

Any idea what is happening?

Improve this question
$\endgroup$
3
  • 3
    $\begingroup$ One wonders how reliable that 99.99% purity claim is... Without specialised equipment, it's generally difficult to distinguish purities of any substance above ~95-98%. If the average consumer can't tell, the supplier has the perverse incentive to cut the cost. $\endgroup$
    – Nicolau Saker Neto
    Jul 20 '19 at 0:28
  • $\begingroup$ A pdf at this link would seem to indicate that typical impurities are a mishmash of elements. documents.indium.com/qdynamo/download.php?docid=1107 $\endgroup$
    – MaxW
    Jul 20 '19 at 2:39
  • $\begingroup$ It would really be neat to throw this inn an XRF and look for the differences. $\endgroup$
    – MaxW
    Jul 20 '19 at 4:10
3
$\begingroup$

It's possible that the gallium is not as pure as advertised. If it has (say) some indium as an impurity, the indium-gallium alloy would have a lower melting point, potentially below room temperature.

I thought that partial freezing might have crystallized out more pure gallium, and left less pure gallium as the melt, but I'm not sure that's how indium-gallium alloys work. I made a few grams of the alloy, and I never saw any such behavior in it -- then again, I never experimented much along those lines.

Improve this answer
$\endgroup$
1
  • $\begingroup$ Every reason to believe that liquid gallium has more impurities than the average over the bulk 2 kg mass. Even if the bulk is 99.99% pure, 20 g would only be 1% of the 2 kg mass. Assuming the 20 g mass has 50% of the total impurities would mean that the 20g has 1% impurities. $\endgroup$
    – MaxW
    Jul 20 '19 at 2:29

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.