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Some fun with Gallium.


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Either today or later this week I will be receiving 60 grams of Gallium to add to my collection. Right now, I have my meager amount of gallium in a 20 mL vial as a solidified blob. My 60 grams of Ga will be arriving as two 30 gram buttons. So my task will be to melt the Ga and pour it into the glass vial where I will need to resolidify it. The problem is, Ga expands as it freezes so if I freeze it too quickly it may crack the glass vial. I'm pretty sure that it won't crack, however, since there will be plenty of room for it to expand upward if it needs to. (It's like a bottle of soda. A full bottle of soda will explode if it freezes because the liquid inside will expand to more than the volume of the bottle. If the bottle is half full, however, it won't break the container since it will just expand upwards as it freezes). So for my Ga I have the following planned.

 

1) Take some water in a big pyrex container and heat it up until it's just below boiling.

 

2) Take a separate container and put some ice water in there.

 

3) Take my current amount of Ga and place the vial in the hot water to melt the Ga that's in there.

 

4) With a plastic container with a spout, melt the 60 grams of Ga into a liquid using the hot water container.

 

5) Pour the ~10 mL of liquid Ga into my vial with the pre-existing Ga in a liquid form.

 

6) Place the cap back on the vial to keep O2 out.

 

7) Take the vial and place it on a surface sitting in the ice cold water.

 

The cold from the bottom should cause the metal to solidify from the bottom upwards, so that any expansion will force the Ga further towards the top and not out towards the side. I figure this will allow it all to solidify and will prevent any cracking of the glass vial. The small amounts of impurities inside the Ga already should also give it the 'seed' it needs to solidify and not supercool. What do you think?

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How hot will the molten Ga be? Putting molten metal into a glass container then submerging it in ice water, will almost certainly crack it! (hot inside cold outside). It doesnt take much of a temp difference.

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Molten Gallium is about 86 degrees Fahrenheit. :) I already went through with the plan and it worked out great! I'll take a picture as soon as it finishes solidifying and I've cleaned off the 'gunk'.

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LOL. Yeah, I set it aside under my photography lamp and it all melted away, so I put it in with my other Gallium but then it solidified. Sorry about that. ;)

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Ga.png

 

As you can see in the image above, everything went great! I lost a few milligrams of the stuff as it got 'stuck' to the plastic container I was melting it in, and some of it was lost as I tried to scrape off as much 'gunk' as possible as it solidified. What really puzzles me is the presence of a blue haze on portions of the metal. Under bright lights, you can see a sky blue tint to the metal at certain angles, but under other lighting you really can't see it at all. I wonder if there was some copper metal that got amalgamated into the gallium and is now emitting its light, or if it's a gallium oxide that is a slight contamination. Either way, it's kind of neat looking. What's cool is that the mercury I have in the same sized vial is at exactly the same level as the Ga is. When you pick each of them up, you can really feel the density difference. (Hg is about twice as dense as Ga). So all in all, it was a fun little time! :D

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lol. Yeah, you should see the container I used to melt the big buttons in. There's this thin blue-black-metal haze to it from where the gallium 'stuck'. :D

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Okay, the blue color is due to a small bit of gallium oxide contamination. Upon exposure to moist air, which there was plenty of since I melted the metal in a hot water bath, a thin layer of oxide will form on the gallium giving it a sky blue tint. That is EXACTLY what I see so that mystery is now solved. Thank you internet. :D

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Yeah, silicon is really cool looking. It certainly does look like a metal, but it is so brittle and completely 'non-metal' like. That and tellurium are perfect examples of 'metalloids'.

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My own experience.

 

One of the very few elements I have bought in large quantity is gallium.

About 1300 grams of Ga 99,99% from 2 different suppliers (no, NOT Alfa Aesar).

Price per kg (1992) ~4000 swedish crowns, which is approximately 600 USD.

The purity 99,99% (=4N) has 100 times too high content of impurities for semiconductor purposes.

 

When melting Ga you soon find that the molten metal it is extremely sticky. This is due to at thin coating of gallium(I)oxide, Ga2O. Melting the metal in air, or even under pure water, is a huge dissapointment!!!

It looks awful, with a dirty crusted soggy skin on the surface. But I soon discovered a treatment.

 

Like Al, Ga is passivated by oxidizing acids. But melting Ga under a ~5% water solution of a nonoxdizing acid (I used H2SO4, quality "pro analysi" = analytical grade) dissolves the thin oxide coating immediately.

In this state, the metal forms a very beatiful silvery white metal sphere (if you stay with a few grams). Under such a diluted acid, the hydrogen formation on the metal surface is very slow, hardly disturbing, but the oxide is quickly dissolved.

And, in this oxide free form, the metal does not stick to any surface at all!

I used a ~5% water solution of H2SO4, maybe it will work with even more diluted acid.

 

I melted Ga (about 50g) i a polycarbonate E-flask, first under air. The molten metal really did adhere to the surface, was impossible to remove mechanically. Extremely sticky. Then I added the acid, swirled the flask, and the result was impressive. The adhering metal just fell of the plastic surface, and formed one beatiful silvery molten sea of metal! Even when the metal had formed crusts of white oxide (Ga(OH)3 and Ga2O3 formed when exposed to air and moisture for about a year), these crusts where dissolved by the acid within a few minutes.

 

Of course this acid treatment slowly dissolves the metal. So, when the metals solidifies, remove the solid and rinse under pure cold water.

 

I also tried supercooling. When completely pure and dust free, the molten metal (under diluted acid) can be kept in liquid state for months at room temperature.

But when I accidentally dropped a tiny speck of dust (some paper fiber) the molten metal began to solidify within a couple of minutes!

One hour later, the whole mass of metal was solid.

 

I also discovered a surprising thing about the colour of Ga.

At one time the melt was solidifying (polycarbonate flask), and soon some strange darker blue spots with sharp angles appeared on the plastic surface. When tilting the flask I discovered that these blue spots where crystals forming.

These blue spots formed on the plastic surface inside the melt, on places WITHOUT any contact with air, so it could not be due to oxidation of the metal!

My conclusion from this experiment is that the solid metal is darker than the liquid, with a bluish tint!

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Not so pleasant. Don´t do this!!!

 

One of the other metals I got in large quantity is - sodium!

Many years ago, I once got an offer I couldn´t resist. Once in a lifetime-offer.

A huge bottle of pure sodium, in large sticks, analytical grade.

The only problem was that I had to buy the hole lot, which was one kilogram...!

 

I quickly (under some anguish...) repacked the metal sticks under pure paraffinum oil. Original protecting fluid was ligroin. Then I put the huge bottle in a fireproof safe, well locked away. And it will certainly stay there. Forever.

 

Yikes...!

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Well, I would like to, but unfortunately it is almost impossible.

It is practically impossible to ship this stuff to almost anywhere.

In the US it has to be shipped according to USPS Publication 52, and so on.

And international shipping is even worse.

 

I don´t even like to take a look at the bottle, because I am getting a bit ... anxious!

So, I keep it inside the safe, and tries not to disturb it.

Probably, one day I am going to donate it to some institution.

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Fair enough...You should at least react some of it, Throw one of the rods into a lake id like to see that :D Actualy i think it would be even better with pottasium big purple flame and all...

 

~Scott

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Potassium...

 

Once (more than 25 years ago) I got a 10g ingot of potassium, unfortunately under kerosene.

That liquid is impure, and the metal coprroded heavily within days!

The oxide quickly forming was a massive grayish crust, which is not the oxide K2O (white), but the dangerous and oxidizing oxides K2O2 (peroxide) and KO2 (hyperoxide).

These are dangerous in contact with oil; cutting in such a piece of metal can initiate a dangerous reaction between the oxide and the oil (litterature says probably not reaction with the metal).

 

So I decided to destroy it. I put the ingot in a metal can, and a couple of friends and I went to the beach a dark and rainy(!) night. Removed the lid and threw the potassium ingot out in the sea. It started at once with a vigorous evolution of hydrogen, got really hot, and ignited spntaneously within 10 seconds.

 

The molten potassium got hotter, burning more and more violently. After about 30 seconds it exploded violently with a very loud bang, sputtering burning metal around (still on the water).

 

My friends were impressed. I was just very pale...

 

I will NEVER repeat that experiment!

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Back to gallium.

 

A friend and I once decided to synthezie anhydrous gallium(III)bromide, from direct reaction of the elements.

A sea of molten Ga (~10g) i an glass flask, dripping liquid bromine onto it.

 

When dripping Br onto the metal, it just inflamed and burned with a red flame (!), the bromine drop fizzing around on the metal surface.

 

Reminded of a small piece of sodium reacting on a water surface!

 

And, to much bromine was added at once. A reddish steam was violently thrown out of the flask, togehter with some GaBr3.

 

Once more, I will never repeat this experiment.

 

I will stay with collecting elements, not disturbing them!

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