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Author Topic: Purifying Gallium  (Read 5241 times)

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Purifying Gallium
« on: June 25, 2011, 01:49:14 AM »

Hello guys.
So today I added another element to my collection. 45g of gallium arrived at my door this morning. This is my experience with the metal. The purity was advertised at 99.99%. In all respects I've no doubt it is indeed pure. However, there was a nasty sheen of grey "slag like" gallium oxide, or at least thats what I think it is, present on its surface. It seems the oxide forms rapidly on molten gallium when exposed to the air. The seller surly poured it molten into a mold and allowed it to cool.

I went about trying to find a way to get rid of the oxide and I found that it dissolves rapidly in warm water. Based on what I've read, the gallium oxide and water combine to produce gallium hydroxide. The reaction produces bubble of hydrogen and or oxygen, I assume. In any case, after the reaction stopped and the remaining cloudy grey water was poured away and replaced with clean water the molten gallium that remained at the bottom seemed to be very clean and pure. It appears that pure gallium is stable underwater and is obviously not allowed to oxidize with the open air.

I added ice to the water and the gallium quickly solidified and I could take it out of the water. After a few minutes, now solid and exposed to the air, the metal attained a slight bluish tint. It seems that, like aluminum, it still oxidizes even as a solid. It's actually really pretty, much better than that matte grey appearance.

I'm not much of a chemist so I have a few questions about this. Firstly, do you think this is a good means of ridding the gallium of the oxides? Melting the metal in your hands and and playing around with it yields alot of this ugly slag. If this process is repeated am I sacrificing much of the element to create gallium hydroxide or gallium oxide. Will there be a noticeable loss in the mass of the sample? What exactly is happening when gallium oxide and water react? What gasses are produced? Is gallium hydroxide or gallium oxide harmful (I know it seem stupid to ask this after the fact)? Is gallium stable in water for long periods of time? I read an article the said that a slightly saline solution (.01-1% NaCl) minimized the amounts of gallium ions absorbed by the water after long periods of time. It was a bit over my head but does that imply that salt water may be best for storing gallium? Any of your thoughts are appreciated. Thanks!



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Re: Purifying Gallium
« Reply #1 on: July 01, 2011, 01:59:21 PM »

I'm not a chem expert but it is obvious that gallium forms an oxide in air. There are very few metals that don't react with oxygen (gold, platinum, etc). I also have a sample of gallium and noticed that molten gallium forms and oxide.

I also doubt that gallium would not react with water. I'm sure it forms a coating of hydroxide.

If you are a pro, melt it in a glove box full of dry nitrogen. Use a syringe. Put the needle deep in it and suck it. Put the gallium into a pyrex or quartz tube and melt the tube and close. Now you have a tube with a inert atmosphere of nitrogen with your gallium sample.

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