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Author: Subject: Ampouling Gallium?
elementcollector1
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[*] posted on 28-9-2013 at 22:16
Ampouling Gallium?


Is it possible to contain molten gallium metal in an ampoule to create a specimen for an element collection? In other words, when gallium freezes, does it expand so much that it will crack the ampoule?

If this is the case, would slow cooling suffice to prevent this? I know that the reason hot glass shatters on contact with cold water is due to thermal shock, so preventing such a drastic change would serve to protect the ampoule, correct?




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Finnnicus
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[*] posted on 28-9-2013 at 22:27


"Gallium expands 3.1% on solidifying, so it should not be stored in a metal or glass container that can break upon its solidification."

From About.com

For a comparison, water expands 9% on freezing.

[Edited on 29-9-2013 by Finnnicus]




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[*] posted on 28-9-2013 at 23:19


so basically your container geometry needs to be right. could you not have some one blow a spherical ampoule and fill it max 45% or so? also small glass christmas ornaments could be a short term answer. they have soft thin glass like an ampoule and the dye/silver inside is easy to remove. shouldn't cost more than a few dollars for something better from a glass blower. no color, no super special shape, just a small sphere. that way you could have fun and melt it from time to time in your hand, and as long as none got stuck in the irregular shape left at the point of sealing, it should not break. just a thought.

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Pyro
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[*] posted on 29-9-2013 at 02:50


you could use a standard ampoule with only a few mm of gallium in the bottom, that way there would be no chance of breaking




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12AX7
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[*] posted on 29-9-2013 at 02:51


How pure is it, and how soft is pure gallium? If the glass is strong enough, it might contain it -- the metal extruding itself as it expands.

If you fill it on its side, so the liquid gallium occupies a shallow secant of the cylindrical cross-section, it should expand fairly freely. Just make sure not to refreeze it in any other position?

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bfesser
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[*] posted on 29-9-2013 at 06:48


I have a couple spherical ampoules if you need one.



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[*] posted on 29-9-2013 at 09:35


I've had some products that I have made at work that expand on freezing and that are packed in wide mouth jars. They are poured in as liquids and the jars are tilted to the side so when they freeze it can expand up the walls to some extent. Better than just having it sit flat in the bottom.



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elementcollector1
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[*] posted on 29-9-2013 at 10:47


Quote: Originally posted by Finnnicus  
"Gallium expands 3.1% on solidifying, so it should not be stored in a metal or glass container that can break upon its solidification."

From About.com

For a comparison, water expands 9% on freezing.

[Edited on 29-9-2013 by Finnnicus]


So, a good test would be to see if water freezes in an ampoule without breaking it.




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Pyro
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[*] posted on 29-9-2013 at 10:55


just do it with Ga, you can easily separate it if it does break.



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BobD1001
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[*] posted on 29-9-2013 at 12:46


It honestly never occoured to me that the expansion of gallium when solidifying might crack glass. I recently put some solid pieces of gallium in a vial to display on my periodic table, which is in my garage. This winter shouldn't be an issue as it will be too cold in there to liquify the sample, however next summer that might become a relevant issue!
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[*] posted on 29-9-2013 at 13:11


I once made the mistake of putting ca. 50 mL of gallium in a glass screw-cap tube.

You get some gorgeous geometric crystal patterns up against the glass, but it did break. The mess wasn't too bad. Basically just a rod of gallium with a bunch of broken glass around it.

A tube might survive if you continuously turned the container while the gallium crystallized. Of course if it remelts on a hot day, don't be surprised to find the tube cracked later on.

For this reason I keep my gallium in an HDPE bottle, which can flex a bit.
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MrHomeScientist
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[*] posted on 30-9-2013 at 07:22


Another thing to consider is that gallium wets glass. Once molten, if you swirl it around inside your ampoule it will quickly coat all the walls and you won't be able to see the liquid metal inside any more.

I actually used this property in my first sample of gallium for display in my collection - I melted it and coated the inside of a vial to give a (very poor) mirrored surface. My current sample is made up of small beads that I made by melting the Ga, drawing it into a pipette, and gently dropping blobs into cold water. Interestingly, it would pretty often supercool and stay as a liquid!
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[*] posted on 30-9-2013 at 16:30


this would be hard to accomplish but if there in no air in the ampoule the gallium cant freeze or stick to the glass.



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[*] posted on 30-9-2013 at 16:40


I've suddenly remembered that there's actually a video that shows gallium sealed in an evacuated ampoule. The gallium remains liquid and doesn't wet the glass, bouncing around like mercury. Supposedly the latter property is achieved by coating the inside of the glass with some gallium oxide.

Take a look:
http://www.youtube.com/watch?v=12SFKUd32Ng
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[*] posted on 1-10-2013 at 10:28


Gallium oxide works (use it to coat crucibles when making alloy).

If the gallium is very clean (given a quick bit of aqua regia, then DI water) it won't wet glass.




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elementcollector1
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[*] posted on 1-10-2013 at 10:32


Quote: Originally posted by Fleaker  
Gallium oxide works (use it to coat crucibles when making alloy).

If the gallium is very clean (given a quick bit of aqua regia, then DI water) it won't wet glass.


Would a nitrate salt and sulfuric acid substitute for the aqua regia?




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[*] posted on 1-10-2013 at 10:55


Can't comment--never tried that.



Neither flask nor beaker.


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bismuthate
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[*] posted on 1-10-2013 at 11:29


Yes it would work to clean the gallium because sulfuric acid will acid corrode gallium. ( I don't know about nitric but i would belive it does)



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[*] posted on 1-10-2013 at 11:40


My gallium looks very clean already, but I'll give it a clean with a dilute mixture of sulfuric acid and ammonium nitrate followed by a quick rinse in distilled water, and dried off with isopropanol (this should suck up the water, and leave the gallium dry when it evaporates). Then, I'll ampoule it. Sound good?



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[*] posted on 1-10-2013 at 11:54


sounds great! Would you mind posting a picture?



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[*] posted on 1-10-2013 at 21:37


Sure thing! Before I do, a disclaimer: This attempt at cleaning gallium metal was half-assed, to say the least. I could have done a lot more, and perhaps this is why the sample turned out the way it did in the end.


For starters, 1.2g of ammonium nitrate, followed by a lot of water and several drops of sulfuric acid. Shown here, next to the gallium's original container.


Quite a big container for just 1g, right? I don't have any pictures of the cleaning process, but rest assured that the lump of gallium didn't seem to get any shinier - it already looked like 'clean' metal to me...


Terrible pic of the finished ampoule. Sometimes, I wish I had kristofagyok's equipment...


Slightly better pic. You can see where the gallium made a mirror on the ampoule wall - it actually made the sample look a little better, and if you look closely you can see those odd hexagonal crystals on the mirror surface. Not in this picture, obviously.


The finished, labeled sample, ready to go in my element collection. I have about 50 ampoules labeled just like this, and 94 more that aren't labeled. Pretty neat!

The best conclusion I can draw from this is that these 1mL ampoules are resistant to gallium's freezing expansion, and are suitable for containing it. I can also draw the conclusion that I probably needed to have melted the gallium in the cleaning solution in order to make it completely oxide-free.




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