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Some fun with Gallium.


jdurg
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Gallium VERY readily becomes supercooled. Apparently the thermodynamics involved with it solidifying does not create a 'greater sense of stability' when it becomes a solid. As a result, it is very happy to stick around as a liquid far below its melting point. This is especially true if your Ga is very pure and there are no contaminations in the container. However once you give it a 'seed' on which to solidify, the solidification happens pretty readily. I guess a good analogy would be a supersaturated solution of something. Until you give it the prodding that it needs to ppt out of solution, it will be quite happy sticking around the way it is.

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Semiconductor purposes.

It turns out that to get a useful semiconductor is much more than just a chemical synthesis of a semiconductor material like gallium phosphide or arsenide.

 

Synthesis of gallium phosphide from the elements is one thing.

The production of a working LED is a completely different story!

 

First, purity. The purity of material for semiconductor purposes need to be at least 99,9999% (=6N). This is because even minute amounts of impurities adversely affects the electrical properties of the material.

 

Second, crystal form. The material in semiconductors is not just a solid lump of material, it is a pure single crystal of the material. So you must pull a solid crystal of the material from a melt. And of course, the melt as well as the formed crystal has to be protected from even minute traces of contamination.

The vapour pressure of the molten material, as well as the elements, has to be taken into consideration, to prevent some of the materal to evaporise.

In this case the vapour pressure of P; Ga has very low vapour pressure even at elevated temp.

 

And then there is the problem of doping the stuff.

Then you need some special crystal orientation for the light emission.

Etcetera.

 

These are some few of the numerous difficult :eek: problems with production of semiconductors.

The subject is more that of solid state physics (semiconductor physics) than inorganic chemistry.

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My 50g Ga sample melted in summer (48C) and has stayed liquid since then - down to a chilly 5C on a winters night (how cold is that you northern hemispherians?).

I have sealed it up with parafilm in a HDPE container. Developed an oxide crust after 4 months but still liquid.

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I have the same experience with gallium. It will stay liquid until disturbed by some small grain of solid matter that induce crystallization. By some reason, the oxide crust does not induce the crystallization process. But a small speck of dust will.

 

 

Northern hemisphere: in worst case the temp has fallen down to about -25 degrees centigrade in a really cold winter (south tip of Sweden).

In northern region of Sweden (Lappland), I think the most extreme recorded is about -53 degrees centigrade.

Well below the freezing point of Hg! :eek:

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From experience, I have found that if you take a copper wire and bend it into a tiny little hook and skim the top of the Ga, not only will the oxide adhere to the Cu fairly strongly, but it will initiate crystallization of the liquid Ga. I used this method to clean off the top of my gallium while it was still liquid, and when it solidified shortly thereafter, the surface was bright and reflective while staying completely free of oxide.

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Very little, if any contamination. The only places where I saw some contamination was at the bottom of the vial where I was really scraping hard to get rid of some oxide that adhered to the glass. Where I was scraping, you can see a very faint blue tint from probably a small bit of copper that went into solution, so to speak.

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The little bits of oxide and the loose bits of copper can act as the seed as well. Basically, when gallium supercools it does that because it can't find anything to help it start solidifying. By adding something to the Ga to give it that kick start, the crystals can begin to grow and the solid will form. I used Cu wire because I had a bunch lying around, and I found that the Gallium oxide latched onto the wire and I was able to get a VERY reflective and clean surface on my Ga as opposed to the oxidized surface I had in the past.

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  • 4 weeks later...

Thanks for that link Erlen. The last time I needed a little bit of Ga in a hurry, I paid twice as much for the shipping as the price of the gallium itself ! I bought from one of either Alpha Aesar or ESPI.

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further experimental updates:

 

I made some gallium nitrate the other evening, rather boring, it does react slowly upon heating, and takes a good 12+ hours to complete.

 

addition to Sulphuric acid, creates a dark grey "skin" on the metal, and heating it will make the metal melt and shiney again, no evidence of a salt yet, OR reduction in the gallium sample size.

 

I`m letting you know this so no-one else decides to try and waste their sample, i`ve still got plenty left however, and Phosphoric and hydrochloric acid hasn`t been tried yet, I`ll let you know how it goes when I get some more free time :)

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The gray skin is probably a simple oxide coating, as I've seen that happen numerous times with samples of Ga. (Hence why I use the Cu wire to skim off the 'gunk' as it is solidifying).

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Gallium is completely non-toxic. There is no way you can get hurt by it unless you take a bath in it. Comparing it in ANY way to mercury is just flat out wrong. (Ga does not vaporize to ANY extent).

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Gallium is completely non-toxic. There is no way you can get hurt by it unless you take a bath in it. Comparing it in ANY way to mercury is just flat out wrong. (Ga does not vaporize to ANY extent).

Indeed, I agree with jdurg. Gallium has a very low melting point for a metal, but it remains liquid up to a very high temperature (as far as I remember to over 2200 degrees centigrade). So, no fear for vapor, unless you heat the stuff to 2000 degrees or something like that and you sniff above the hot liquid :D.

 

Gallium, however, does stain. I have some of it and everything, which is touched by it becomes wetted by it... horrible!

 

I also have mercury, and up to now I only used it once in a very controlled way in a small experiment. The toxicity of that indeed is of a TOTALLY different level.

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LOL at the Galium stains :)

 

it happened to me the other day, I broke a small peice off, as you know it shatters like glass, some went on one of my rings (silver) and just melted like solder, si I rubbed it off and made it worse, that tiny microgram couated the entire palm of both hands and one leg of my jeans by the time I gave up, the silver color made me look like some kinda mid 60`s alien from a B Movie :)

 

washing up liquid soon removed it off my hands, the jeans have yet to be washed!

 

anyway, back on topic FUN with Galium, you`ll need to snap a tea spoon in half for this, warm up the breaks and touch the gallium sliver just enough that it covers and sticks, bring the 2 ends together as if you`re tring to "Fix" it again and then run it under cold water, it will "freeze" and make your spoon look usable again, polish up the "weld" so it`s as good as you can get it and keep the spoon cool.

 

from there you can fake a Yuri Geller act, OR!.... put it in the canteen and wait for someone to stir their coffee :)

 

Enjoy!

 

 

edit: another thing not bother trying with galium is making this Eutectic mixture with ordinary 60/40 tin/lead solder.

it`s basicly everything you don`t want in a solder and more, perfectly useless as far as I can establish, I made a 50/30/20 Galium Tin and lead melt, then froze it.

at room temp it`s as brittle as can be, a metalic white in color with an unsmooth surface.

*sigh*

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any amount of pure completely pure metal in your body is not good for you and yes the liquid gallium doesnt vaporizae but can be pulled in very slowly by both cappliary action and osmosis. im not saying its not safe im just saying be careful its easy to over look a small drops on your hands and arms when you take a bite into your sandwich. by the way im not saying dont play with gallium i do all the time,

just be careful and wear gloves

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Just as a test, I purposely ingested a small piece of gallium that was remaining in the original container I had it in. Guess what, I'm still alive and not even close to being ill.

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Just as a test, I purposely ingested a small piece of gallium that was remaining in the original container I had it in. Guess what, I'm still alive and not even close to being ill.

 

You make me laugh. :P

 

A rather strange occurrence happened recently. A few days ago I listed a set of elements for sale on ebay. Two of the samples in the set were a small piece of gallium as well as indium. So a few days ago I line them all up on a piece of paper to photograph them and I put the gallium and indium next to each other. I then leave the elements and upload the picture and forget about the elements until they sell this morning. So I go to package the elements and where the two pieces of indium and gallium were a few days ago is now a single puddle of molten metal.

 

I was quite perplexed by this and concluded that the table must have been bumped making the solid gallium and indium touch which created an alloy that is liquid at room temperature. The molten alloy then speeded the mixture of the metals.

 

Yes I realize its a bit sketchy; any other ideas?

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