all right so what we're going to do now is the crystallization of this particular substance it doesn't you don't really need to know what it is because we're only talking about the procedure and the method or the techniques uh for crystallizing but it is caffeine and we have just for the sake of calculations at the end i want you to determine the percent recovery so we have 508 milligrams right now so 0.508 grams and then what we wanted to do what we want to do in the end is determine how much we have after recrystallization has occurred to see if there's any loss of product uh which oftentimes there is and so we want to see how much right so we're going to calculate the percent recovery now for crystallization basically there's a couple different there's actually a lot of different ways to do this uh one of the more common ways that we do it in our lab is by just dissolving it and the minimal amount of hot solvent okay so what is this thing soluble in that's going to allow for crystallization to occur oftentimes since these are known procedures there's a lot of there's there's already a lot of methodologies out there or procedures outlining it for us and so for uh for caffeine in particular i'm going to use ethanol so uh here's ethanol right here 200 proof means that it's a 100 100 ethanol um so basically before and the key here was remember we want to dissolve it in the minimal amount of hot salt okay so remember solid materials tend to be more soluble in hot solvents right and so if we dissolve it in hot solvent as it cools down it's the solubility of that substance will decrease in that cooler solvent right and so let's say we macmi dissolved a gram of caffeine inside x amount of solvent as a hot solvent as it cools down it's not going to have that same ratio of solubility and so it's going to either precipitate out and meaning form a solid or it's going to uh form some nice crystals if we let that cooling process occur as slow as possible then we're going to get crystals okay so i want to point out again since we are doing uh this crisp recrystallization process in hot solvent um we have to put it on a hot plate and since we're working with ethanol this is fine to be working with on the benchtop and but we don't want to place this lovely 508 milligrams of caffeine on the hot plate right away what we want to do is add i see i've actually i did the process already and so i determined personally that i like about 15 milliliters to start with this amount of caffeine so i measured out 15 milliliters and this would be something that might be in the procedure already if it's an unknown compound and you're trying to recrystallize it uh what you want to do is just add a little bit of solvent so where it's all trial and error right so we're scientists it's all trial and error you want to add solvent to the solid material before you put it on the hot plate the reason why you do this is because you don't want to basically burn your substance you don't want to melt your substance because once you melt your substance it's called something called oiling out will occur and it's just going to ruin the recrystallization process and you're going to get like a poopy brown oil on the bottom for example and it's never going to form nice crystals you're not you're not going to purify your substance and you're going to be really upset right because you're trying to get lovely uh crystals of caffeine and so that's why you want to make sure you add solvents to your solar material before you start heating it now what i've done here is i have it in a flask so that way if it gets hot i can use some like a nice test tube clamp to go ahead and lift that off but this isn't going to get so hot that i won't actually be able to grab it with my hand but that's something you need to be aware of know what you're working with how hot this is going to get and then make sure you have this proper safety precautions uh to make sure that you have can take care of it safely right and so um this is just gonna i'm gonna constantly stir this again if you let it sit there it can heat the solid material on the bottom and then cause that oil that we don't want to have and oil out okay so we have to be constantly stirring this you can also throw a stir bar in here that's gonna and then turn on the the magnet here to have it stirring and that stir bar is gonna create a nucleation site for crystals to form on but then you gotta scrape it off of the stir plate or the stir bar and it's just the whole thing right so i find it very easy to just kind of stir it like this now i didn't add that full 15 milliliters because i wanted to make sure that i didn't add too much okay all right this was just an approximation that i uh i made for myself you want to add again the minimal amount of hot solvents to this once it starts boiling then we're it's not going to get any hotter than that right this is ethanol so it's like 85 or something like that and that's going to uh be as hot as it can get so once it starts boiling if you find that not all the material is [Music] dissolved what you can do is actually have one of these guys on here as well and then i'll be stirring both of these at the same time and then i also have my medicine dropper okay and this medicine dropper is going to allow me to take a little bit of this hot solvent that's just ethanol and place it inside of the um the recrystallization flask okay so uh you can see that a lot of this material is dissolved however there let me see if i can get you a nice contrast there's a little glare but there is still a little bit of material in there so i'm gonna go ahead keep stirring this keep stirring this and this is definitely something you just have to be patient with and once it's all dissolved then what we're going to do is take that off the hot plate place it on our workbench and then let it sit there for just a few minutes depending on the substance it could take 10 to 15 minutes to crystallize completely or i do personally know that caffeine will crystallize very quickly in ethanol and so it won't take much time at all but the key here is once it's all dissolved set it aside and leave it alone the slower and like the undisturbed crystallization processes are always going to be the best and they're going to allow for the best perfect purification uh of your substance through this method okay and so [Music] let's see we're almost there so close it's so close you can see just a little bit there and so we're just again we're going to be patient and we are constantly stirring okay so when you're letting it sit there obviously to the good lab uh techniques or like kind of skills are going to be cleaned up while it's waiting it's sitting there don't just sit there on your like and then like stare at it it's like watching water boil you don't want to do that a watch pot never boils right and so what you want to do is while it's while that's cooling off to room temperature you want to go do other things and what we're going to do is actually set up a filtration apparatus so that way we can do a vacuum filtration to isolate the the lovely caffeine crystals that we've obtained so then that will allow it to dry as well because it's a vacuum filtration it will remove all of the ethanol after five to ten minutes and then we can weigh it and see how much we've got i didn't uh show you the weighing out of this material because that's kind of lame but i will give you that final number in the end okay and again we started with 508 milligrams i see some chunks in here and those guys are giving me some problems so what i'm going to do is go ahead and try and smash them up a little bit with my with something you can have a glass stirring rod or you can use right now i'm just using the pipette for the medicine dropper um because i can okay so you really can't see that but uh just imagine some solid in there like little chunks little pebbles almost and all i'm trying to do is make sure they go away [Music] because they are everything else is pretty much dissolved with the exception of just a few crystals and in a not to bombard you with a ton of information but in a laboratory if i had some um stubborn material that really just didn't want to um recrystallize i'm sorry i didn't want to dissolve what i could do is filter that off because maybe that's not actually caffeine maybe that's some other impurity that's in here um and i don't want it in there and so i could also always filter that off really quick and then continue with the recrystallization process afterwards just to ensure that i get the uh purest possible sample [Music] so this is why i want you to get um these medicine droppers if if i had to i could if i i kind of observed and realized there's a lot of caffeine sample in here and i don't think any of that's going to dissolve i would add a little bit i would pipet carefully a little bit of ethanol into here and then i would um [Music] using a pipette allows me to be more careful and add just the minimal amount because again we want only the minimal amount of [Music] ethanol to dissolve this caffeine because that's going to almost ensure that we have a saturated solution of caffeine in high ethanol and if it's saturated and hot ethanol as it cools a lot of that caffeine is going to precipitate out or form crystals and so now that we've got it all dissolved i'm going to go ahead and place it on the bench okay i'm going to go ahead and turn the heat off so actually you know what i'm looking more closely at this there is actually a little bit left in here so this is perfect because now i get to use my pipette and i will transfer i'm actually just gonna do like a couple drops so like one two three four five six seven eight why not i like me it's a good number right let's do eight drops why not so i really feel like that's all we really need um sometimes you can even add less than that just really depends on how much sample you're working with we're working with 500 milligrams which is quite a bit uh and so eight drops is totally fine and we are looking pretty good let me get this boiling again [Music] there we go i think all of it's gone so now i can place it on the bench top and let that cool to room temperature and i'll give you a look at it right now all right so here it is looking good so um again basically you can you can cover this if you want or you i would just put it somewhere safe depending on what it is you don't want your lab mate to knock it over you don't want to knock it over you don't want to hate yourself or you're not meat because that's not cool nothing but love right um but if you let it sit here cool down to room temperature nothing happens uh what you can also do is add it to an ice bath just set it on ice carefully so it doesn't fall as the ice melts and then after that if it doesn't form crystals then what you can do is grab a glass stirring rod and so this guy right here and then you scratch at the bottom like that it's pretty much like this so once you scratch at the bottom like that you're scratching the glass and this is actually just kind of creating a like an imperfection in the glass that allows for something it's basically creating something called a nucleation site and a nucleation site is just a it's like a imperfection of the glass or like a porous portion in the glass that allows the solid caffeine material to start crystallizing on so like it adheres to it uh probably intermolecular forces and then once it sticks to it another caffeine molecule will stick to its uh itself and then we get stacks on stacks on stacks of caffeine molecules to make these beautiful needles right before our eyes oh my goodness have you ever seen such a glorious thing such cool needles not everything crystallizes in needle form obviously like if you've seen salt it forms a certain shape and sugar will probably form a certain shape water forms a certain shape and so it just depends on the type of material but needles are definitely a common thing for organic materials look at that that's so cool i love crystallization i love just watching it sometimes you can see them just grow right before your eyes if you're looking more closely but that nucleation site once it's formed and that you start you form a tiny crystal that's all you need to make and make it pop off basically to form something that we're looking at like right here uh once and you can also add like a tiny crystal to to a solution that you're trying to crystallize if scratching it didn't work a tiny crystal can act as a nucleation site as well okay so like if i had one of these needles and one of my lab mates was struggling to get this to crystallize i can add a tiny needle to their sample and it might help serve as that nucleation site for more christine more caffeine to crystallize okay okay so now i've let this sit for quite some time now and as you can tell there's a lot of solid in there um actually mostly solid not very much liquid is obvious so that's cool um now what we want to do is go ahead and filter off that solid material and then isolate the nice pure crystalline caffeine and so the setup that we want to use for that is a vacuum filtration so what i have here is a lab stand and then we have this basically let me take it off for you it's a clamp so this is one of the types of clamps that we have in the lab and it's got this we basically screw it onto this pole and it basically holds everything securely so that it doesn't fall now what we've also got is a vacuum flask it looks like an erlenmeyer flask except it's got this little arm and this little like bumps right here are usually going to be where you want to put a vacuum hose okay what does the vacuum hose looks like to look like looks like this it's different than a water hose in that it doesn't it's really rigid rubber and so it won't collapse on itself when you pull it back okay imagine like sometimes even when you're sucking through a straw and you have this delicious milkshake shake and it's plugging the bottom and sometimes when you stuck on the straw the strawberries like that that wouldn't be a very good vacuum tube right so what we're going to do is put this on here we're going to clamp it so that way it's secure and will not fall over because and we want to do this before we connect the vacuum okay hopefully oh no this doesn't work i don't know pause okay so that's a common thing there's a couple vacuums in this organic chemistry lab that don't work and so hey i just showed you a realistic uh scenario right so move on to the next spot now either in a hood or an adjacent spot we've got this vacuum too and you don't want to connect it until after you've clamped this uh vacuum clasp because these vacuum tubes since they're so rigid they have a mind of their own then just go like this and then they take your flask and they go and they smash it onto the bench and then you broke your glassware and you're super bummed because i gotta pay for that and everybody's sad because there's glass everywhere too so we don't want to hurt ourselves anyway and now we've got this neoprene adapter this is the smaller one of the two the way to know which one you use is basically if it falls inside that's too small it's gonna be really hard to get out so be careful when you do that but this one sits right on top you can barely see the lip um kind of chilling right there yeah oh and this right here is called a buckner funnel remember that was like it's the one that kind of i think i said it looks like a box it's got the square top and then it's got these the holes right there you put a little a nice little circular filter paper in there and it sits amazingly on top and then you go ahead and put that on there and voila we've set up our vacuum apparatus our filtration device and then if we pull our vacuum you can hear it sucking okay first thing you want to do before you add your material to it is wet the filter paper with a little bit of the solvent that you use so that way it sucks it down because right now the filter paper is kind of ripply and it's possible that when you pour it over some of the solution that you pour in can sneak underneath and then solid can fall down into the vacuum flask and then we'll lose material that'll decrease our yield and we'll be super bummed because we didn't get 100 which we're probably not going to get anyway but uh either way we want to maximize our yield right so that's one of the ways that we can do that another thing i want to mention is if we're doing something like crystallizing sugar at home or salt you'll you're not going to really have the same setup right and so what you can do is i'm just going to do this very carefully you can use you can see you can see the lit clear liquid right here right and so what we're going to do is i'm just going to pour that off and this is called decanting so when i say decant a solution i mean pour off the liquid but leave the solid behind okay and so this is something that you can easily do at home to kind of separate your solid material from your liquid material you're going to have to be careful because it's not always going to be stuck at the bottom like it was for caffeine that just made for an easy example of decanting for me perfect i totally planned that by the way um but now i'm going to take my glass stirring rod whatever i have and i'm going to break up that solid material and i'm going to pour the rest of it okay so i'm going to turn this vacuum on i basically wet it already and so now all of the um all of the the filter paper is kind of suctioned to the buchner funnel b c h and e r and now i can go ahead and pour it off very quickly you can see stuff going down and then i still have more in here if you want to go ahead i'm not going to but if you wanted to rinse your caffeine to maybe get the rest of it out of this particular flask right here you don't want to rinse with just regular old ethanol because it does it is soluble in ethanol right to some degree and so what we want to do is actually rinse it with cold ethanol because as we know caffeine is less soluble in cooler ethanol and so this will prevent any significant loss by dissolving it but we can still get more of the material out and check it out there's a good amount of caffeine stuck in here and so it might be a good idea to rinse that in another scenario but really all i want you to kind of gather from this is the process of recrystallization and then i mean you saw me pour it off now i'm going to let this hang out here for about five to ten minutes and what we're going to do is take a look at the final mass to determine how much we obtained from that 508 milligrams that we started with okay and so this will give us an explanation as to uh why certain procedures or chemical reactions aren't going to yield 100 so one of the things obviously would be that we maybe the reaction didn't go to completion or in the case of caffeine we might extract it from tea or coffee but maybe our extraction procedure wasn't very good and then also when we finally purified it we we obviously have some white material down here we left some here and so we lost product like that but i'm gonna show you this it looks really cool in there um so let's take a look at that look at that i love the way it looks it kind of reminds me of a truffula tree i don't know my kids are really into the lorax and they smell like uh butterfly milk or something and they feel like silk the truffula tree so it looks so soft and like fluffy you can make a need out of it i think it would be amazing and but also when you're looking at your material anyway right it's always best to kind of spread the material out so that way we can make sure that we can get the ethanol kind of sucked out of the material as best and efficiently as possible and so that's going to be done by kind of spreading it out so that way it comes in contact with the um with the filtration or like the filter paper that way it's the vacuum's actually having an effect on it and that's pretty much it for the filter or the recrystallization process so what i really want i'll give you that number for the final mass in just a second but what i really want you guys to do is do this at home with either sugar or salt or if you're feeling ambitious i would really love to see you guys do both now obviously you're not going to be able to do um do this like kind of like the way i did but so instead of ethanol and caffeine you're going to be using water and sugar or water and salt and you're going to have to do it on the stove and so i guess technically you could probably do it with a microwave if you didn't have a stove um although that procedure would probably be uh pretty tedious but i think it's it's really important to learn how to do this stuff like if you did have that stove to add the minimal amount of water to your sugar or salsa salt material to dissolve it but in hot water okay and so when we do this we need to be really careful because hot water is um what is it hot so it can burn you and i want you guys to be really careful with this but i mean it's just water right so hopefully you guys know how to like cook pasta because that's all we're really we would be the equipment right we're boiling water but add the minimal amount of hot water to the sugar or salt to dissolve it sugar and salt are really soluble in water so for example sugar is i think you can do a one to three ratio and that is one cup of water for three cups of sugar that's a lot i'm not expecting you to use all of that but what we want to do is make some rock candy and so i'm gonna create my own video but i'm not gonna really put too much uh dialogue to it i'm just gonna show you the process and then we will see the outcome right i'm gonna make rock candy it's gonna be super awesome and i want you guys to do sugar and salt to see how the crystals look different okay i think this would be really cool to observe and because the crystal lattice that's formed is obviously going to be very different because sugar is this cyclic um basically carbon oxygen hydrogen containing compound well salt is just sodium and chloride and it's just the two things kind of just chilling next to each other and then they form this uh really awesome structure in the solid form and so i think it would be really cool for us to kind of observe that okay so let's take a look at the mass of this final product of caffeine hello there so basically i poured i scraped off this material the caffeine from the buchner funnel onto this white paper and what we've got is .377 grams of caffeine on them so you can may or may not be able to see let's see oh oh i don't know how to affect the light here let's see tap the screen there you go so maybe you can see it or not um but there's a little bit of caffeine on that beaker phone and so there's some lost there right so this is another thing that we have to deal with when we are kind of transferring materials from one vessel to the next now one thing i want to mention is if we wanted to maximize our yield i can just take some ethanol dissolve it in here go back to that vacuum flask dissolve whatever's in there or whatever was left in the recrystallization flask i can go and recapture all of that material dissolve it in ethanol and then recrystallize again to maximize my yield so keep in mind the stuff that went through the buchner funnel that was in solution right and so the recrystallization process is a purification process and so the stuff that went through the flask or the the buccaneer funnel filter that stuff is going to be less pure than this stuff right here so i don't want to combine it even if it's just solid material uh recrystallizing it again is totally okay but keep in mind that this is probably going to be the purest and largest batch of material that i can get out of it any subsequent recrystallization is going to obviously yield less material because we have 373 milligrams of it right here and uh so there's only about uh like 130 milligrams and kind of scattered throughout the different vessels that we've transferred it to and so crystallizing 100 milligrams is a lot harder or requires less material uh less ethanol to do to recrystallize that and so it's just gonna yield maybe we'll get like 50 milligrams out of it and so sometimes it's worth it sometimes it's not just depends on the material that you're working with and your goal if it was something that you spent like six months making and now you it's like gonna cure cancer or something you might want to go back and recrystallize that again to get the most out of this whole process right so it's just gonna it's just gonna depend right or what you can do if is this something that is this something that you do all the time well let's say you did this reaction uh let's say like five times a month well if i combine all of this stuff with the other stuff after the five reactions that's another 500 milligrams right so i can combine all those into one batch and then do a recrystallization at the end of the month and then boom i got another milligrams right 373 whatever it is okay and so this is just me telling you how to be super awesome in a lab and be very efficient uh atom economy is really important uh as well as yields and so we've got to figure out how to maximize our yields in any way right and sometimes recrystallization process for example is going to give you less than you started with because that's the nature of it and that's just something you gotta deal with so uh sometimes it's okay sometimes you can figure out ways to improve that yield so again uh i would show you but the scale is actually as i've messed with it i'm touching the table it's going back down so again let's just call it 373 milligrams so 0.373 okay and then so what you want to do is that number divided by 508 times 100 and that's going to give you your percent recovery okay okay bye [Music] is [Music] hey guys come on where's my backup all right i hope you enjoyed that let me know if you have any questions bye