Going supercritical.

about a year and a half ago now I started getting really interested in aerogel and despite it being kind of expensive I went out and bought some so I got this little square of it which is pretty cool it has this weird haziness to it and it kind of looks blue and this thing is also super light where you can barely feel that it's in your hand I mean you definitely know it's there but it's also it's weird how light it is for something this big but in any case after getting this and playing around with it for a bit I decided that I really wanted to make it so I went online and in the past I'd read a bit about what went into making aerogel but this time I really do it more and I found that pretty much all of them use supercritical fluids most commonly supercritical co2 when I read about this I went oh supercritical fluids of course supercritical co2 I've heard about that before I've read about it I think it might have heard about it in school but when I really started thinking about it I'd never actually really seen it before and I didn't really know what it was I knew the basic idea of it where a liquid is heated in some sort of closed vessel and this causes the pressure to build up as it vaporizes eventually though when the pressure and temperature get high enough it reaches something called the critical point and when we get past that temperature it ends up going supercritical where there's no real difference between the liquid and the gas phase and it kind of acts as a hybrid between the two this to me I guess on paper made sense and when I would read about it online but I couldn't visualize at all how that made any sense I looked it up online and I did find some videos that showed co2 going super critical but even after watching them all I still didn't really feel like I knew what was going on one of these videos though was made by Ben over I'd applied science and he had built this pressure chamber specifically to see the whole phase change that was going on so I contacted him and I asked him if I could pay him to make one of these chambers for me so that I could mess around with it and actually see in person what was going on but instead he just offered to send me the one that he already made totally free of charge and he wouldn't even let me pay for the shipping at this point that was kind of over a year ago now and I've been a bit slacking on this whole project but nonetheless huge thanks who was out to bend for helping me do this so basically I'm just gonna be doing a bunch of random things with this nice pressure chamber that Ben sent me and see if I can find anything interesting when co2 goes supercritical Ben did warn me though that this is kind of dangerous which I knew by just looking at it he tested it many times and he trusted it in his video to hold it in his hand when the co2 was supercritical but still he warned me that in theory it was kind of like a bomb and it could explode at any time but it should be safe but he's not responsible okay so the first thing that I had to do was open up the chamber and then add some dry ice which is solid co2 I packed in as much as I could fit and then I put on the other half of the chamber added the washers and the bolts and cranked it all down this part was pretty much the most important step because if I didn't tighten it enough the co2 would end up just leaking out it was also important though to not tighten it down too much because this could add some extra stress to those large acrylic windows I eventually felt that I'd done a pretty decent job but by this point almost all the dry ice had disappeared there was really just a sad small amount left and I decided instead of trying anything with this I would restart everything and I would just tighten everything down as fast as I could this time it was definitely way better and to test it out I just closed the valve to let the pressure build up as the pressure increased the dry ice slowly melted into liquid co2 but I started noticing a problem the liquid co2 was boiling way too much and this meant that there was a leak then I started hearing a hissing noise and I saw some white gas shooting out the back of the chamber this happened because I was afraid of tightening it too much but clearly I was a bit too soft on it but despite it being a failure what it did show me was that if there was a leak it wasn't just gonna blow up or something even when it's supercritical and the pressures a lot higher it would probably just leak out slowly like this and not fail catastrophically still though just for safety reasons and in case I'm wrong about this I made sure to do everything behind some protective shielding now I had a much better idea on how much I had to tighten everything down so I did a third run and it all worked like before I closed the valve which caused the pressure to start increasing and for the dry ice to melt under the normal atmospheric pressure that we live in carbon dioxide can only be a solid or a gas but at higher pressures it can also be a liquid if we take a look at the phase diagram for co2 we can see that it's only at five times atmospheric pressure that the liquid phase starts to appear so immediately after I closed the valve it was all still jumping directly from being a solid to a gas eventually though when the pressure built up to be about 5 atmospheres it was all able to start melting up until this point there was no leak and it all seemed to be going pretty decently but one major problem that I noticed was that the gauge wasn't moving at all this was a pressure gauge and I just said before that the pressure was increasing but it was still around zero this wasn't anything dangerous but it clearly wasn't working properly and there was a chance that it was just broken to really test it I just let it sit here for a bit to make sure that there were no leaks I came back about five or ten minutes later and it seemed pretty good so I opened the valve to vent out all the co2 with the pressure now dropping below that five atmosphere threshold all that liquid co2 was jumping back into being a gas also I'm not really sure about this but I think that the cloudiness is just a mixture of liquid co2 vapor and co2 gas after this run I thought that maybe the gauge wasn't broken and wishes plugged with something so I took it off and tried cleaning it and I did another run to test it out but again he didn't work so it was probably just broken as I said before this wasn't really a safety issue or anything but when trying to make this go supercritical it is nice to see what pressure it's at as long as I'm really not careless I shouldn't really have to pay attention too much to the pressure but it is still something nice to have I wish I had another spare gauge like this just sitting around but I didn't so in this case I wasn't gonna have that luxury however this didn't mean that I would have to do things completely blind because besides looking at the pressure I could also pay attention to the temperature this chamber was already set up with a small hole drilled in the side that I could put a thermocouple in this would let me carefully monitor the temperature and now to make it go supercritical I just had to heat it up this was done using a hairdryer and the goal was to bring it up to about 30 C as it warmed up the liquid co2 started to boil and the amount of it decreased but unlike before there wasn't a leak here this meant that I was making more and more gas in the same confined space which caused the pressure to increase and it also caused the density of the gas to increase and at the same time the heat was causing the liquid co2 to expand and to slightly decrease its density so as I kept eating it the density of the two phases were getting closer and closer and I noticed that it was getting harder to see the difference then eventually it got to this point where there wasn't a clear separation between the two and it was just this weird haze this was what I assumed was the critical point and here the densities of the two phases were pretty much the same so they started mixing together at this point I was well into the supercritical fluid area and liquid co2 was no longer able to exist I then kept heating it and the liquid part suddenly looked like it just turned into smoke this is because above the critical temperature of co2 which is about 31 C there's just too much energy and it's molecules for it to stay together as a liquid so all the co2 molecules end up getting pulled apart and they turn into something that's kind of like a gas this means they're able to move around freely like a gas and they're able to diffuse and fill this entire chamber however at such a high pressure its density is abnormally high and more like that of a liquid this then lets it dissolve things like a liquid and because of that supercritical fluids are often described as a gas liquid hybrid so now in this chamber was just a bunch of supercritical co2 but what's kind of cool is that it can turn it back into liquid co2 by cooling it down I got this idea from Ben and by putting some ice on the side of it I can drop the temperature below the critical temperature of 31 C and liquid co2 can start forming again before when I made it go supercritical and it all just kind of disappeared in a puff of smoke I thought it was really cool but I think I like this part more this was because in general the idea of boiling something until it completely disappeared was something that I'd seen before and it made sense to me however here I was starting with what looked like a completely empty chamber and then making a bunch of liquid from nowhere when it was eventually done it was nearly half full and I decided to make it go supercritical again but this time I wanted to look at it at a different angle and to see what the surface of it looked like just like before as it got closer to the critical point it got harder and harder to see the surface of the liquid co2 then when it got close to what I assume is the critical point it started to get a bit hazy it also had a bit of a blue color to it and it reminded me of aerogel but I'm not exactly sure what was going on then just like the other run it all very quickly disappeared and looked like it turned into a cloud of smoke what I had now was this whole chamber completely filled with supercritical co2 but what was really weird was that I just couldn't see it at all if I were just randomly handed this I would assume that it was completely empty and the only thing that could maybe tell me otherwise was that the broken gauge was now reporting a little bit of pressure when I was done playing around with it I wanted to try emptying it while it was still all supercritical this caused the chamber to slowly become hazy and I think this was because the pressure was dropping below the critical pressure as this happened I think the liquid in the gas phase were no longer able to stay all mixed together and the liquid started separating out it would have done this as extremely fine droplets though and then very quickly jumped to being a gas so there wasn't any condensation of liquid also as the pressure dropped below that 5 atmosphere point it just wouldn't have been able to be a liquid in general so after trying all that and seeing that it didn't just explode I wanted to try some other things I just saw that when it was supercritical it looked like it was completely empty but it was still actually filled with a supercritical fluid so what I wanted to see was what would happen if I put something solid in the chamber and how it would interact with the fluid I happen to have some silica beads lying around those things that you get in those little drying bags and I thought that they would probably work pretty well so I loaded up the chamber with a bunch of them along with some dry ice and I closed the valve like before this caused it all to slowly melt and eventually I had a bunch of liquid co2 with the silica beads at the bottom I then took it around a bit and it pretty much looked exactly like what you would expect if you had a bunch of beads sitting at the bottom of a liquid the liquid was able to slosh around pretty easily but the beads mostly just like staying in the same place I think shot it with my hairdryer to make it go supercritical and it was pretty much exactly the same as last time except I now had some beads at the bottom the interesting part was when I went to move it and it still looked like it was under a fluid it was like we just saw with a liquid co2 and they were all bunching up and didn't really like to move as another test I just strongly shook the thing up and down to see how the beads would move in an empty chamber it would fly from the bottom and easily hit the top but here they were more or less staying in one place again it was like the whole thing had been completely filled with a fluid and it was preventing the beads for moving up the tests that I thought was the most interesting though was when I flung the chamber on the side and I was able to make some turbulence in it and I guess that there were some small bits of some other junk on the silica beads and this was able to move around in the fluid I think that other shaking test that I did might have been a little bit weak but this one really showed me that there was a fluid in there after this I decided to empty the chamber but unfortunately for some reason I didn't think of filming it it actually turned out to be really cool though so I ended up doing it again and this is a clip from a different run but anyway now that it was empty I shook it around like I did before just as a comparison this time the beads were easily able to pop up and hit the top of the chamber like you'd expect if it were totally empty I originally chose to use these beads just because they happen to be next to me but they actually turned out to be really interesting when I looked closer at them they were all full of cracks but they were also kind of sparkly and some even had some color the silica beads that I started with definitely weren't colored in any way and there was something weird going on here to get a better look I had to zoom in a lot and I could see that some of them would reflect different colors depending on the angle this reminded me a lot of opal but I doubt that it's a similar mechanism going on here and I don't really know what's happening the beads were really cracked because the supercritical co2 was able to get into them and then I vented the pressure out really quickly it could be that these cracks are so thin that it makes some weird thin film interference or something but I'm kind of just making that up and I'm not really basing it on much of anything if any of you guys have any idea of what's going on here I would really like to hear about it I also think that it would be really cool if I were able to recreate this on a much larger scale maybe using a silica bead that's closer to the size of a golf ball I have no idea when I'll try doing this or if it's even remotely possible but it is something that I do want to eventually try but anyway that was pretty much everything that I wanted to do but as just one last thing I decided to replace the gauge I bought a new one for mcmaster-carr and now I could actually see what pressure everything was at this time when all the dry ice was melting the pressure on the gauge actually went up and it got to around 500 psi then as I heated it and it made it go supercritical the pressure started increasing again and it got just above a thousand psi it was still increasing a bit though and after I let it sit for about 10 minutes they ended up peaking around 1200 after this I opened the valve and I saw that the cloudiness only started forming the moment the pressure got below around a thousand psi this obviously wasn't something that I could notice when the valve was broken but it's kind of interesting they meant that all this fogginess was probably just the two phases liquid and gas no longer being able to mix together a lot of this fogginess was then able to last until it looked like it was around 50 or 70 psi which was just around that 5 atmosphere mark below that liquid co2 isn't able to exist so all this fogginess which I think was liquid co2 ended up just disappearing anyway with all that being said that was pretty much everything I wanted to try out I think by playing around with it I got a much better idea of how supercritical co2 worked and what it was like and I felt a lot more comfortable using it to make aerogels the chamber also worked super well and it didn't blow up and kill me so again a huge thanks goes out to Ben for letting me use it when I first started this little project I wanted to try using the chamber to make aerogel and also to extract caffeine from coffee but I found that neither of those things would really work both of those things need much higher pressures and lot longer soak times and the o-ring that's in the chamber just wouldn't be able to handle it to do either of these I'd have to build a proper chamber using stainless steel and all high-pressure fittings this video here was filmed over six months ago and in the mean time I actually did put together the proper chamber I've also actually used it to make aerogel and I'll eventually post a full video about it on my main channel Niall rad I'm also thinking of maybe using that chamber to make decaf coffee or to make that large-scale coloured silica bead that I mentioned before either way though I don't have plans to do either of those right now at the moment but they will probably eventually get done also as one last point some of you might be wondering why this video was on Niall blue and not the main channel Niall red and it's because I just didn't really feel like it fit there I've recently decided that I wanted to just dedicate Niall red too large and weird projects like making toilet paper moonshine or diamond water and this was not something that really matched up with that I had already filmed it all though and it made no sense to just waste it because I had a lot of fun with this project and there's a lot of good info in it so I decided to throw it here on Niall blue it's a bit weird though because the amount of work that went into making it all happen was kind of the same as a Niall red video but that's just how it is as usual a big things goes out to all my supporters on patreon everyone who supports me can see my videos at least 24 hours before I post them to YouTube also everyone on patreon can directly message me and if you support me with five dollars or more you'll get your name at the end like you see here [Music]

Channel: NileBlue

Views: 2,031,344

Rating: 4.9391546 out of 5

Keywords: nile, red, science, chemistry, aerogel, supercritical, pressure chamber, carbon dioxide, critical point, silica, fluid, liquid, gas, dry ice, blue, nileblue, nilered

Id: JslxPjrMzqY

Length: 19min 53sec (1193 seconds)

Published: Fri Jan 24 2020

Reddit Comments

[u/Massive-Gas]

"y'know spoons?" gets me every time

[u/[deleted]]

I'm angry that he posted this on the Nile Blue channel, and not the main channel.

Seems like anything more complex than "burning up diamonds and dissolving the gas in water" is too much for the dumb lay people to understand, right?

[u/shadowPHANT0M]

Looks like an air wedge was created by the cracks giving a thin film interference similarity. Same basic idea only an air gap instead of a film.

[u/[deleted]]

I wonder what the colour in those beads is caused by. If the fractures are in the nanometre range he created an interference effect with light? Interference effect pigments: micron sized transparent platelets coated with thin nanometre thick Ti2 giving multiple refraction/reflection paths. The thickness of the Ti2 coating sets the color, from thin to thick in nanometres: white 40-60nm (pearl effect), 60-80nm yellow, 80-100nm red, 100-140nm blue, and 120-160nm green.

You can make this by filtering ground mica/borosilicate out of pearly white texture shampoo. Next you want to sublime Ti2 onto the platelets while being agitated. From memory I can't recall the method...

Or I am probably wrong, but isn't opal a silica based mineral created under high pressure? Is that why the beads had that look? Cool video. Just reminded me of this stuff.

[u/Legendary_Dotaer]

i wonder how it would look if he tossed something that dissolved in SFCO2 like caffeine into the chamber