Aluminum and Mercury


Mercury forms alloys with most metals in a process known as amalgamation. Last week, I messed around and tested it out with some gold leaf and it was pretty cool. This time though, I’m going to see what happens when I add it to aluminum. It’s supposed to be quite destructive, which is why you’re not allowed to bring mercury on a plane. So I went to Home Depot, and I bought a strip of aluminum. I cut out a small section and drilled a hole about halfway through. This little crater is important because Mercury is super annoying and without it, it would just slide off the plate. Under normal conditions, aluminum is surrounded by a protective oxide layer. Metallic Mercury isn’t able to penetrate through this barrier, so it kind of does nothing. Sometimes it’s possible to get things going by manually scratching away the oxide layer. I tried doing this about two or three times, but… it wasn’t working for me. I even tried to brute-force things using a drill, but that didn’t get things going either. I thought that maybe was just super slow to get started, so I went to lunch and I left it for about an hour. When I came back, nothing had changed so, clearly I have to use a different strategy. Instead of trying to remove the oxide layer mechanically, I’m going to try to do it chemically. So I took out all the mercury and I added some dilute hydrochloric acid. The hydrochloric acid quickly reacts with the oxide layer and dissolves it away. This exposes fresh aluminum metal; which also reacts with the acid. I let it go for about a minute, and then I get rid of the acid. With the acid gone we’ll start to reform the oxide layer, so it’s important to add the Mercury quickly. The amalgamation started almost right away, but it’s really hard to see. In the reflection you can see me leaned over to get a better look and I noticed some very small hairs forming between the aluminum and the mercury. In real-time this process is really slow, so I set things up for a time-lapse. So the major thing going on here is the combination of the mercury with the aluminum to form the amalgam. Some of the amalgam that forms gets dissolved in the mercury and makes its way to the top. When it gets there it comes in contact with oxygen in the air and it reacts to form white aluminum oxide. This part of the process is pretty short-lived though because it quickly gets covered and protected by the oxide. This prevents fibers from growing directly from the mercury, but obviously they continue going out from the sides. This happens because some of the mercury is dissolving into the aluminum. The amalgam here also reacts with air to form the oxide, but the difference is that it doesn’t shut itself down. The dissolved Mercury can continue to creep along the surface and amalgamate more aluminum. In theory, this process should keep going until the entire surface is covered with a thick layer of the oxide. The mercury could also penetrate deeper into the aluminum and compromise its strength, but I think that takes a really long time to do. About four hours later I decided to end the time lapse. I spun the thing around and when I noticed the other side looked a lot cooler, I was a little bit sad. Anyway, when I poked at it you can see that it’s not structurally very strong. I’m not sure what I was expecting, but I was surprised at how fragile it was. It looks like there’s quite a bit of aluminum oxide here, but surprisingly there’s only about 200 milligrams. I went to clean things up a little so I scraped away a lot of the oxide on the edges this reveals fresh aluminum amalgam which is the silver stuff that you see. As usual though it quickly reacts and turns grey again. As I said before, some of the mercury has dissolved into the aluminum. I was really curious to see how much more amalgamation would occur if I took away all the visible mercury. So I removed the large drop and I clean things up. I then left it out and did another time-lapse over the course of a couple hours. There was apparently enough left to get a decent amalgamation going, but it was actually less than I was expecting. I cleaned things up again, and this time when I scraped the edges, they’re not silver like before clearly the amalgamation process is done. I think the reason that it stops is because all the mercury that’s present is amalgamated with aluminum, but it’s hidden under the oxide layer. Without the main drop in the middle, we don’t have excess mercury to creep out and continue making more amalgam. It also might be possible that small amounts of mercury are taken away as the fibers grow, but I don’t know if that actually happens. Anyway, I’m going to go ahead and react things again because I want to highlight something. So, like before, to get things going I clean it up with some hydrochloric acid, then I add the mercury back. But this time, instead of doing things dry, I add some water. This prevents any cool oxide fibers from forming but I want you to notice is the bubbling that’s occurring. Instead of reacting with air, it’s reacting with the water here to form aluminum hydroxide and hydrogen gas. I was initially only expecting bubbles to come from below the mercury, but they’re actually coming from everywhere. What this tells me is that there was still some amalgam present and it was just trapped under the gray oxide. When I went to clean up the mercury this time it was actually more of a pain than usual. Some of it got stuck to the side, and I wasn’t able to get it out. Instead of letting it go to waste though, I just decided to do another time lapse. And I’m glad I did because although this one is shorter, I think it’s cooler than the first one. When it was done, I cleaned it up just like the last one, but there were still some little mercury bits left over. I think they were just covered with way too much oxide and weren’t really able to interact with the aluminum. I was curious to see how much damage was done. So I cut the plate in half. When I take a look on the side, it doesn’t look like it went deep at all, and it was really just surface level. I cleaned up one of the sides and we can see that again it really didn’t do that much damage. I Imagine to really destroy the aluminum, the mercury would have to sit there for quite a long time or we would have to continually remove the oxide that forms. In terms of its application, aluminum amalgams are commonly used in chemistry for reduction reactions. As we saw earlier, metallic mercury wasn’t amazing at attacking the aluminum, so for these reactions we usually use a soluble mercury salt. The general idea here is that mercury keeps exposing fresh aluminum, which really likes to donate electrons. A somewhat common, but highly illegal use of this reaction, is in the production of MDMA. Anyway, I think that’s about it for this video. Let me know if you’d like to see me try something else in terms of aluminum amalgams and tell me some other metals you’d like to see me try. Now just for a quick shoutout, you guys should check out the website that was made by one of my Patrons. It’s a pretty simple setup, and it’s used to generate molecule wallpapers. So you can just type in the chemical name, or its structure, and you can choose the color of the molecule as well as the background. If you have some time you should definitely check it out, and I’ve linked it in the description. A big thanks goes out to all of my supporters on Patreon! Everyone who supports me will see my videos 24 hours before I post it to youtube and they can also directly message me. Anyone who supports me with $5 or more will also get their name at the end like you see here.

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