pillyg Posted February 12, 2011 Posted February 12, 2011 As many of you know i am trying and failing to make MgAl. I have Mg shavings for firestarting. I was trying to melt them in to an ingot but failed. I took it out of the crucible and poured it into a can to let it cool. It put some charcoal on it and left it. I came back a week later to see how it was. It had all oxidized which I knew would happen. It has been cold here (pretty much 18F) the whole time. I ripped the can and found a dark green powder. It was like AF charcoal it was so fine. It was also warm. I out some snow on it to cool it down, and it started smoking. The snow melted and ammonia gas was produced. There was a lot. My questions are1. Why was it still hot even though it had been freezing for a week.2. Why did it heat up when snow was added3. Why did it produce ammonia?
Mumbles Posted February 12, 2011 Posted February 12, 2011 That sounds like magnesium nitride to me. It probably wasn't still warm, just when you opened it, the chemical started reacting with the atmosphere, which is exothermic. It heated up further when you exposed it to pure water, which subsequently gave off ammonia from the magnesium nitride. I still don't know why you don't just wrap the Mg turnings up in aluminum foil, and add them to the Al melt.
pillyg Posted February 12, 2011 Author Posted February 12, 2011 That sounds right I am wrapping the Mg in foil. This was b4 I did that. I was trying to melt the Mg into an ingot. Then you told me to wrap them.
ausgoty Posted February 12, 2011 Posted February 12, 2011 But if you try to melt magnesium on its own you will probaly still run into trouble. When I melt it I already have a pool of molten aluminium in the bottom of the crucible. Even so just before it melts it seems to start burning and as it melts little fires spring up all over the place. I believe it is only the melt pool and the relative lack of oxygen that stops it from burning completely. If you really must create magnesium ingots, perhaps inject and inert gas such as argon into the crucible as you melt? Oh, and don't leave it outside in the wet for 2 weeks. Magnesium corodes very quickly in the presence of water/water vapour as you have found out
Arthur Posted February 12, 2011 Posted February 12, 2011 Working with Magnesium really needs a vacuum induction furnace (expensive) or noble gas purging til the Mg cools to hand hot
Algenco Posted February 13, 2011 Posted February 13, 2011 But if you try to melt magnesium on its own you will probaly still run into trouble. When I melt it I already have a pool of molten aluminium in the bottom of the crucible. Even so just before it melts it seems to start burning and as it melts little fires spring up all over the place. I believe it is only the melt pool and the relative lack of oxygen that stops it from burning completely. If you really must create magnesium ingots, perhaps inject and inert gas such as argon into the crucible as you melt? Oh, and don't leave it outside in the wet for 2 weeks. Magnesium corodes very quickly in the presence of water/water vapour as you have found out that's when you give it a quick stir and cover
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