Warning: Sodium hydroxide is corrosive.
Wear gloves when handling it.
This reaction also produces large amounts of hydrogen gas.
Work outside or in a fume hood.
Greetings fellow nerds.
In previous videos, you've seen me destroy aluminum objects with gallium.
What's left over is weakened aluminum that has small amounts of gallium embedded in it.
By your request, in this video we're going to try and recover some of that gallium.
Now the most common suggestion was to react the alloy with water.
This is not a bad idea actually, as gallium aluminum alloy is well known for being reactive with water.
The problem with using the aluminum from our earlier experiments is that while they do have gallium in them, it's not enough.
The alloy allows some attack but the aluminum oxide layer just grows thicker.
Even with heating the reaction eventually stops.
We need to increase the gallium content of our gallium aluminum alloy to start the process going.
I'm not going to add extra gallium though because gallium is expensive and i don't want to risk wasting it.
So instead we're going to go in the opposite direction
and force the destruction of some of the aluminum by reacting it with sodium hydroxide.
First we get some gallium infused aluminum.
In this case we have about 27 grams.
And to this i'm adding about 300mL of water.
Now in small portions we add a stoichiometric equivalent of sodium hydroxide.
So i'm adding a total of 40g.
Sodium hydroxide is highly corrosive to aluminum and it dissolves the aluminum oxide layers to form sodium aluminate.
This allows the aluminum underneath to be attacked and also forms hydrogen gas.
Gallium metal also gets attacked by sodium hydroxide but that reaction is much slower.
So for now the destruction of aluminum is the dominant reaction.
As more and more of the aluminum is consumed, the alloy should liquify as gallium becomes the dominant component.
There is still a lot of aluminum in it but the alloy will then pool into the bottom of the container.
It's important not to let the reaction get too hot or the gallium will be consumed as well.
Slow down the addition of sodium hydroxide if the self-boiling becomes excessive.
In previous runs the reaction ran out of control and overflowed.
So do pay attention.
You can even drop in ice cubes if it gets too hot too quickly.
Eventually, as the sodium aluminate and undissolved aluminum oxide particles build up, the reaction will slow down to a crawl.
This takes about an hour.
If the metal still hasn't liquified by now then there is too much aluminum
and you should refresh the reaction by pouring off the excess solution
and adding more water and equivalent sodium hydroxide.
Maybe also add in more gallium infused aluminum if it's available.
Mine seems to have liquified just fine so i'm going to let it cool down until it solidifies.
Now pour off the solution and in the bottom we'll have gallium metal.
This is very impure as there is still a significant amount of aluminum alloyed with it.
But now that the gallium concentration is high enough, we can purify it with water.
Get about 300mL of water or so and add in the gallium metal.
Now heat it up until it's near boiling, about 80 celsius or so.
We want to melt the gallium and react away any aluminum.
This method is safer than using sodium hydroxide since gallium reacts incredibly slowly with water.
So this is a good way of separating it without losing the gallium.
We couldn't use this earlier since the aluminum content was too high and the alloy couldn't melt.
Now that the sodium hydroxide consumed most of the aluminum,
the alloy can melt and we can use water to destroy the last bit of aluminum.
Keep heating until the gallium stops bubbling.
Now turn off the heating and let it cool and solidify.
And here is the gallium piece.
For amateur uses this is sufficient and will behave like pure gallium for most purposes.
Although it is a bit dirty with embedded aluminum oxide bits.
If you want to clean it up a bit more, you can get a 20% solution of sulfuric acid.
Heating it up and adding the gallium so it liquifies.
The acid reacts with the oxides and helps clean up the gallium.
The drawback of this method is that it consumes a small amount of the gallium as well
so it shouldn't be used for primary purification, just as a means of cleaning up the gallium.
Anyway once the gallium is completely molten, shake it a few times to knock off the impurities.
Once that's cleaned, quickly dunk the container in ice water to cool it and resolidify the gallium.
Once its solid pull it out and give it a wash.
And there we have it.
A hunk of gallium metal recovered from gallium aluminum alloy.
Now granted this isn't perfect, a significant quantity of gallium is still in the solution from before
and requires advanced solvent extraction to recover.
In some cases, this crude method couldn't retrieve any gallium at all.
The droplets of gallium were too small.
But this method is simple to perform for the amateur and just requires some sodium hydroxide and water.
I'll try and test the advanced methods in a future video.
Thanks for watching.
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