Today I am finally going to be distilling my mercury and I know a lot of you guys have been waiting for this for a while. In general, to get super clean mercury there are two major steps. The first step is a mechanical and chemical cleaning and the second is a distillation. The first step is very important to do before the distillation, because it removes the bulk of the contaminants. I won't be showing that part here today and I'll be focusing just on the distillation, but for those who are interested in seeing those cleaning steps, I cover them in a video that I did several months ago. The link to this video can be found in the description. Anyway, as I said, after the initial cleaning steps the mercury is actually pretty clean. I went ahead and used it in several reactions with absolutely no problem, but I decided that in the end I did want to distill it. Distilling the mercury will definitely increase its purity but I did it mostly because I thought that it would be cool to see. In general, cleaning mercury is dangerous, but this distillation step is much more scary than the cleaning step. In the previous video, probably the worst thing that could happen was a mercury spill, and even that isn't too horrible. Mercury does fume a lot at room temperature and it's bad to breath this in, so probably the other major danger is being exposed to a small amount of mercury. To mitigate these risks, I worked over containers to catch any possible spills and I worked in a very well-ventilated area to avoid breathing in any of the vapour. In this video though, we'll be heating up mercury to its boiling point and generating a lot of mercury vapour. Mercury boils at a relatively high temperature, so there is a risk of cracking or breaking the glassware under the heat. If the glass were to break, it would realise a crazy amount of mercury gas into the air, and on top of that, I'd probably have some hot mercury spilling and splashing around. Anyway, with that implicit warning in place, we can get things started. The mercury that I'll be distilling today is actually from two separate sources. The stuff on the right is what I cleaned in my previous video, and since then, it somehow got oxidised and dirty. The mercury on the left was received and cleaned much more recently and so it still looks pretty good. The liquid that you see floating above the mercury is just water, and it's used to keep down the mercury vapours. If the mercury were stored without water above it, mercury vapour would fill the entire container and when I open it, it would be released into the air. Without the water it's also much more possible for mercury vapour to passively leak out of the container. Before we start, I am going weigh out the mercury and this is just to show you guys the mass that we're working with. The mass will be a little bit inflated because it will include the water and the bottle, but you should still be able to see that it's quite heavy. The first bottle alone weighs something like 3.4 kg and the second one weight about 1.5 kg. From this mass we can approximate the volume of mercury that we have by dividing it by the density of mercury. This obviously won't be super accurate though, because I'm including the mass of the bottle and the water. What it tells me though is that I'm working with something around 350 ml of mercury, which helps me decide the size of the flask that I will distil it in. I'll talk about flask choice a little bit more when we get to the actual distillation. Right now, I have two sources of mercury, and I am going have to combine them. One important thing to point out is that it's very important to have the beaker filled with water because if we'd poured the mercury into a dry beaker, a lot of splashing would occur Anyway, the entire contents of both containers were emptied into the beaker. At the bottom, we clearly have our mercury, but above, we have a lot of the mercury contaminated water. What I need to do now is pour off as much of the water as possible. Any water that's included with the mercury we're gonna have to distil, and it's kinda just a waste of time. It's pretty easy to pour the majority of the water out, but soon we'll get close to pouring out the mercury as well, so I stop and I have to suck out the rest with a syringe. Using the syringe, I pull away most of the water that remains but I leave a very small layer to try to block some of the vapours that might be coming off. The mercury here is now ready to be distilled, so I let it chill out and I move on to setting up the apparatus. OK... so this is the set-up that I'm going to be using. On the left, we have the distillation flask and the heating mantle, and through a distillation adapter, it's connected to an air condenser. The boiling point of mercury is high enough that it's really not recommended to use a water condenser. If the water doesn't pass fast enough through the condenser, it could in theory cause some of the water to boil, but the bigger issue is that it will create a huge temperature differential, and it might crack the glass. The likelihood of this happening is honestly pretty low, but I don't really think it's worth risking it, considering a water condenser offers no benefit here. Anyway, moving on, the mercury will condense in the air condenser and be collected in a receiving flask on the right. I decided to do this distillation under vacuum, because it allows me to boil the mercury at a much lower temperature. The normal boiling point of mercury is around 360ºC and under my vacuum I can probably get it to boil at around 260ºC. So if we look even further to the right, we can see that I have another piece of glassware with a bunch of tubing set up. This piece of glassware in the beaker is known as a trap and it's connected to both my distillation apparatus and to my vacuum pump, which you can't see in this shot The trap serves as an intermediate between the pump and the apparatus, and it prevents any mercury from making it over and potentially destroying my pump. Initially, when it's just water being distilled, I'll keep the trap at room temperature, but once mercury starts coming over, I'll have to cool it. And finally, I have a container under the entire apparatus, just in case any mercury spills. Anyway, I think that's enough talking about the apparatus and now we can get started on the actual distillation. The mercury in the beaker from before is then carefully poured into the distillation flask. I mentioned earlier that the volume of the mercury is important and this is so I can decide whether to use a 500 ml flask here, or the 1 l. A good general rule for distillation is to not fill the flask above the halfway mark. 300-ish ml is a little bit too much for a 500 ml flask but it's perfectly fine for a 1 l flask. To try to keep things boiling nicely, I added in some broken glass. The density of mercury is really high so the glass just sits on top, but I figured that maybe it could still help some way. I turned on the vacuum pump and the heating mantle and it doesn't take long to water to start distilling over. The water that was included with the mercury will be distilled off first and then I'll swap out the receiving flask for when the mercury starts to come over. Some of you might be wondering why I didn't just remove the water with a separatory funnel and there's actually a reason for this. Some of the mercury was stored under mineral oil before I cleaned it, and I just want to be sure that all of the oil is gone. If there's any minute quantities of oil left, it should in theory co-distil with the water, and it will show up in the receiving flask After distilling off the water, there wasn't any oil in the receiving flask, so my washing steps must have been pretty effective. Anyway, boiling off water isn't too interesting, so I'm going to jump ahead a little. I kept heating things until water stopped coming over and it looked like there was no water vapour in the distillation flask. The vacuum pump was turned off and the apparatus was cleaned, dried and reassembled. In the beaker on the right, I also set up an isopropanol dry ice bath. This cold bath is really easy to set up and all I need to do is pour in some isopropanol and then drop in some dry ice. It's more common to make a dry ice bath using acetone, but I unfortunately only had 99% isopropanol on hand. When the dry ice is added, there will initially be a lot of bubbling as the isopropanol cools. After just a few minutes it should settle down and become much more tame. Not long after I started heating things, mercury started to collect on the sides of the flask. This made for a very nice and reflective surface, so you can actually see my house and maybe even the camera. This doesn't last for too long though, and once the mercury starts to boil, the flask should clear up a lot. And now to show you guys something that's kind of dangerous. With the vacuum distillation, it's pretty typical to seal the joints using grease. In my case though, I couldn't seal all of the joints because my grease can only withstand up to 200ºC and the mercury boils at a much higher temperature than this. So basically I couldn't use grease and I expected some of the joints to leak and that I wouldn't have the best vacuum going. This was the case in the initial stages of the distillation but apparently as the mercury started to boil, it started to self seal the joints. This is something that I should have taken into account for, but it was an error in judgement on my part. It eventually achieves a decent seal, so the vacuum pump is able to drop the pressure and then the boiling just takes off. I don't think that I have to tell you guys that this is really dangerous and it should be stopped immediately. I honestly let it go on a little bit longer than I should have though, because I wanted to show you guys the violence of it. To stop things it's pretty simple and we just have to take it off heat, so using the lab jack, I lowered the heating mantle away from the flask. I turn on the heat again, and this time, I'm very careful to make sure that I don't get any violent boiling. What I'm going to do here is bring it to a boil, distil over a little bit of mercury, and then change the receiving flask. The violent boiling shot impure mercury, as well as broken glass, into the receiving flask. There's also a bunch of mercury in the air condenser and the adapter, so I'm just distilling a little bit to clean those things up. I collected several drops of mercury, stopped the distillation, let things cool, and then transferred the contents of the receiving flask back to the distilling flask. With everything set up again, we can actually start the real distillation, and this time, guys, I promise things work out. As the mercury vapour travels up the adapter, you can see it condensing of the walls a bit. What's interesting here is that the mercury vapour is completely invisible, and we don't have something like a grey or silver cloud that you might expect with metal vapour. Also, the surface tension of mercury is really high, so it beads up immediately after condensing on the glass. Anyway, it doesn't take long for us to get a steady distillation of mercury going. A lot of the mercury vapour was condensing on the sides of the 1 l flask, so I covered it with aluminum foil, to try to insulate it and help the vapour come over. Now, when we take a look at the receiving flask, we see that we're collecting some nice and clean mercury. From this point on, things are pretty much on autopilot, and we just have to wait for everything to distil over. To increase the rate of distillation, and to help the mercury make it over, I decided to insulate the adapter as well. I move the tin foil back, and we can see that this time, the mercury is boiling much more nicely, and not violently like before. I found that it was really mesmerising to watch the mercury condense. There was just something oddly satisfying about watching the mercury beads form, and then slide down the condenser. When the mercury passed through the vacuum adapter and into the receiving flask, it also looked a little bit weird to me. It's pretty typical for a liquid to streak when it moves across a surface, but because of the super high surface tension of mercury, it instead travels as completely separate drops. To me at least, I feel like this kind of gives the illusion that it's a solid, and not liquid. In this shot near the end, you can see just how shiny and mirror-like the surface of the mercury is. Anyway, after several hours, we finally get to the end of the distillation. The end is not defined by having nothing left in the distillation flask, because it's really important to not distil to dryness. It's kind of a judgement call on how much you should have in the flask when you stop it, and I honestly think I stopped it a little bit prematurely. I turn off the heating mantle and I remove the aluminum foil, and I just wait for things to cool down now. Once everything had cooled, I took a shot of what remained in the distillation flask, and it looks a little bit weird here. The colour is yellowish, because it's a reflection of the heating mantle that's below off-screen, and the top is all bumpy and rough because of all the broken glass. All these factors combined with my weird lighting angle makes it not really look like mercury. Anyway, now it's time to clean up, so I start to dismantle the apparatus. I start by cleaning the vent adapter first, and then I move onto the air condenser and the vacuum adapter. The cleaning process here is pretty simple, and I'm just using a squirt bottle with water, to try to wash out the mercury. The mercury tends to be really stubborn, so it takes at least several washings to get it out. Even after many, many washings though, it's still very possible to have some stubborn mercury still stuck there. When I take off the air condenser, you can see some mercury spill into the container. When this happened, I was happy that I used a second smaller container to do the washings over, because cleaning the larger one would have just been a much bigger pain. Now I get to the vacuum adapter, which is the last major piece to wash. When the vacuum adapter is removed, it's really important to cap the receiving flask, just to prevent any dust or dirt from falling into our fresh mercury. We can't forget to look at the trap, but first, we have to let things thaw out. After helping things melt with a little bit of cold water, I see that the trap didn't actually catch any mercury, and it only has water. This either means that not much mercury vapour came over, or it means that whatever came over passed directly to my pump. I used a water recirculator pump, so everything's pumped into a reservoir, and there was no mercury there, so I'm actually leaning on the first option. Anyway, what I need to do now is transfer the nice clean mercury into a storage container. During the distillation, I thoroughly cleaned out the bottle, so everything's just going to be transferred back into it. It's important to be careful here, and make sure that the mercury doesn't splash out of the funnel. The transfer of the mercury was surprisingly complete, and I couldn't see any mercury left over in the flask. After everything was added, I poured in about 100 ml of distilled water. Just to be thorough, I then use a wash bottle to clean the funnel. I then go ahead and cap the bottle, but I put some saran wrap on first, because the inside of the lid was flaking a little bit. Now I come back to the distillation flask, with the mercury and the broken glass, but with proper lighting here, it actually looks like mercury. Anyway, what we wanna do is transfer it to the other bottle and reserve it for a future distillation. I was honestly a little bit surprised how shiny the stuff left in the distillation flask was. Normally, if the mercury was super dirty, it would be full of contamination here, but it still looks pretty clean. This tells me that the cleaning steps I did prior to the distillation actually cleaned the mercury up pretty well. There still might be some metallic impurities or other things dissolved in the mercury that we can't see, but I think it was still pretty good. Anyway, with several water washings, I try to get out any mercury that was left behind. I didn't film it, but after the distillation, I weighed both the receiving flask and the distilling flask, and from this, I was able to calculate how much mercury I had. Based on the calculations, I found that I had 292.5 ml of clean mercury, and about 46 ml of dirty mercury with some glass in it. The presence of the broken glass throws off the calculations a little bit, so the volume here is probably a little bit elevated. When both of the volumes are combined, we get a total of about 338 ml, which is pretty close to my estimate at the beginning of the video. Keep in mind that the technique I used in the beginning of the video, to determine the volume, is only really viable for mercury because it's so heavy. The discrepancy in mass between my estimate and the actual amount of mercury is about 350 g. This is only something like 30 ml of mercury, but if we worked with something that had a lower density, it could represent a few hundred millilitres. Based on the straw poll results from my Patreon and Youtube, I've decided that the next video will be on dibenzylacetone. Also, I'm working on part four of my paracetamol synthesis and once I get that filmed, I'll upload it as soon as possible. As usual, I'd like to thank everyone who's supporting me on Patreon. Anyone who supports me with $5 or more will get their name at the end of the video, like you see here. Eventually, I hope to get some higher tiers going, and also add some more rewards to the $1 and $5 tier. If I made a mistake with your name, or I forgot to include you here, please let me know by messaging me on Patreon. Anyway, these are the videos that I've already filmed, and the ones that I plan to film. If you have any suggestions, please let me know in the comments. Also, if you haven't already, you can subscribe to keep up-to-date with every video that I post. I'm trying to post at least one video a week, and this month, there will probably be some doubling up some weeks.
I spent every day of my graduate school career using a vacuum line with a large mercury diffusion pump refluxing 24/7. It easily contained 500 mL of mercury - right on the bench, and was one of four or five in the lab.
BALLSY. GET THIS MAN A COAT
Wouldn't the differing amount of water affect his calculations in the end? Or has he taken it into account in the 30 mL range he estimated.