I'm studying chemistry for my first year on high school. You really helped me out with my project about destillations because of this video! People like you who let students get interested in their skill earn alot of respect! Thanks!
Thank you very much! I was searching an explanation of the difference between miscible mixture's behavior and the immiscible one. Watching this video I understood the reason why Raoult's lawyer doesn't works with immiscible mixture. This video travelled to Italy! So many congratulations and good job for the future!
Thanks for the compliment, Von. You are right that there is unlikely to be a universally good extraction solvent unless you are only after one natural product. The classic example is eugenol from cloves, which can be nearly quantitatively extracted directly in methylene chloride or steam distilled. If you opt for direct extraction, there is likely to be additional non-voltile material in the extract. To clean that up, LC is definitely the answer (RP or NP).
+Robert Baindourov Humble thanks for the praise, Robert. There will be many, many more videos coming to the channel in summer 2016 as I finish another project with The Great Courses. Stay tuned!
As a second comment. RP and NP usually both stand a pretty good chance of working if you use the right mobile phase. There are choices you can make to hedge your bets, but at the end of the day chromatography is a fickle lady, and sometimes you just have to try everything at your disposal until you find what works empirically. This has been a fun discussion, VonMilash. Comments like this really spice up the channel. Thanks for your input!
You could probably do normal phase, too. I like RP because I used to be an HPLC jockey for a pharma company in my younger days. The best choice will really depend on the exact identity of the extract compound. One should also note that when working with raw material like plant matter, a direct extraction would have to be done before any LC technique could be applied. Steam distillation allows us to sidestep this requirement, extracting and distilling in one process.
In the example shown here (which is one that you are likely to use in a teaching lab), we are using water boiling at STP, so 100 C would be the temperature of the vapor. However, since steam (vapor) is the key in this technique, you are not restricted to the boiling point of water. A carefully controlled steam distillation (using a somewhat more complicated apparatus) can be carried out at any temperature from 100 degrees C on up!
This was a very interesting and informative video... It helped alot. N thanks for uploading it. I also want to make a request that ... could you make a video on azeotropic distillation and extractive distillation... And their difference! That would really help me out! :)
I have an inquiry that what is the boiling temp of the of the system its nearly water boiling temp. ? and when the steam is sent to the boiling flask , it can be condensed ...??
Is this very interesting! I wish you could do a follow-up version using the vernacular, rather then chem-speak, and instead of phrases like "involital is brown", you would say, "this is water, this is Rosemary, or what have you.) Thanks for taking my brain for a walk around the block!
ok so what is the difference between steam distillation and "distillation" (deflagmation?) where you keep your to be distilled solution in 100 degC? Other than poor mixing in the later example and difficulty with keeping the temperature constant i would say there are non right?
Steam distillation is used for oils with a low vapor pressure. (high boiling temperature at one atmosphere pressure) At 100c the oil vapor pressure is well below one atmosphere so the vapor will only travel to the condenser with gas diffusion which is extremely slow, especially in the narrow tubing. This would be like attempting to distill water at 50c under one atmosphere. Higher temperatures may not be practical either due to equipment limits or because of unwanted reactions, likewise extended distillation times may result in unwanted degradation of the oil. Vacuum distillation can replace most uses for steam distillation as both methods are used to work around vapor partial pressures, but you need both a vacuum pump and vacuum tight apparatus for vacuum distilling. There may also be issue on the condensing side of a vacuum setup if the vapor pressure curve of the oil is very flat, in which case you would need extra cold condensers, and then maybe you are below the melting point of the oil and you have issue freezing.(Compounds know for sublimation are likely better for steam than vacuum.) I suppose it may be possible to use a flow of inert gas in place of the steam, (and this may actually be more energy efficient than a simple steam setup) but this, like the vacuum method, adds extra complication to the apparatus. And if the mass of oil is tiny, you could use vacuum without a condenser and simply chill the receiving flask to circumvent the melting point issue.(Or use a mid temperature condenser for removing the bulk heat with a super chilled receiving flask to capture the remaining stray vapors.)
Good Job but you did not relate your theoretical explanation to steam distillation in any way something is missing no mention of lowering of separation temperature
Do not expect to get an explanation for every single thing, people should be able to use their intellects and logic to figure some things on their own, otherwise, they are not really worth studying these stuff, are they?
Hey Chem Survival.. I love the videos.. if you could PLEASE be so kind as to tell me which video production software you are using... particularly for the movement of the molecules.. i found especially intriguing. Thanks
Hi Daniel. I use a combination of several software suites including ChemDraw, Adobe Creative Suite, Sony Movie Studio and others to produce these videos. The moving objects that you are referring to in this video (the blue and red spheres) were actually created and animated using Microsoft PowerPoint. It is a much more powerful application than many give it credit for!
i didnt understand why the oil is carried with water. Does the oil evaporate in the flask and is carried by water vapor or is it carried in the liquid phase?
+Chris This is a great question. As far as I can see, conceptually it shouldn't matter. Either way 100 degree steam permeates the insoluble plant material and helps the oils to vaporize. In my teaching labs, we boil the water to generate 100 degree steam in-situ because it simple, safe and works well with the oils that we want to extract. Keep this in, mind, though. Liquid water will not boil above 100 C no matter what you do (unless it is pressurized), but vapor water (steam) can be super-heated. So imagine a really stubborn oil that will not vaporize well at 100C, but will vaporize better at a higher temperature (let's say 200 C as an example). Sometimes, we use steam at a controlled, higher temperature to improve the process. In this case, the steam can't be generated in-situ. It has to be generated, further heated, then pumped through the sample as a gas at that higher temperature in much the way that you described. This is one thing that makes steam distillation so versatile, if you design your steam generator well, you can set the temperature to just about any temperature you need to optimize the process.
Direct extraction is a nother viable technique many times. It will remove non volatile substances as well, sometimes requiring some extra steps to complete the purification.
The distillation flask contain non aqueous material and littile amount of water. By applying steam from the mixture the steam carries volatile material in to the condenser. Distillate is collected from the condenser. Suppose the distillation flask contain only non aqueous material. Its boiling point is much higher. We canont separate the volatile oil as simple as the previous case.
Hi Professor Davis! I've been a fan since seeing you on Great Courses videos. You're a great teacher...but your audio needs some work!!! Have you tried using a compressor or any other audio processing? My hearing, admittedly, sucks; but I have a hunch that I'm not the only one having trouble hearing you on your vids from time to time. Just wanted to give you a heads-up because you are definitely someone worth listening to!
Thanks for the feedback Daniel. Some of my videos from my early days are a bit rough, but my production values have gotten better over the years. I will probably have to reproduce some of my early work when I find the time in order to make it consistent with what I'm making now. Thanks again for the feedback and for enjoying my great course projects. They are one of my proudest achievements
The steam (water) serves several purposes in this process. The first is to provide temperature control, keeping the system's temperature below that at which the oil decomposes. The second is to provide some thermal mass, acting as a sort of carrier gas sweeping the small amount of oil vapor along through the system.
Does steam distillation work for oils work better worse for oils denser than water? The fact the vapor pressure from the steam pushes the oil vapor over makes me think that if the oil vapor is heavier than the water vapor, it wouldn't work as well. Is that not the case?
In the case of steam distillation it's more about volatility. Oils with higher vapor pressure will perform better under this set of conditions. Having said that, dense oils tend to be larger molecules with greater dispersion forces which means they often have lower vapor pressures and can be tricky to obtain through steam distillation.
Very good question! Essential oils can have boiling points in the 250C range. Often, oils thermally degrade before vaporizing completely. The steam helps to moderate the temperature, keeping it close to 100C so that this does not happen.
sure, that's true, but if you're doing natural products isolation, then you'd probably have at least two extractions to begin with.. a nonpolar and a polar. because there's no way everything in the bark or bulb or leaf or whatever is going to be extracted in dichoro or ethyl acetate or whatever by itself. as a synthetic organic chemist, i don't think i used reverse phase a single time to purify a compound. good vid either way. ;)
If the sidearm condenser heats up, the vapor can travel all the way to the end of the retort and escape to the atmosphere. Cool, running water is essential to distillation (this is why moonshiners always set up near a creek ;-) )
Perhaps it would be of benefit to view previous videos as well as read up on Raoult's law of thermodynamics and Dalton's law of particle pressure. This does require a very basic foundation in chemistry, but doesn't have to exceed the layman's abilities to comprehend. First, however, some very basic science must be understood. My intention is to distill essential oils and this is achieved through steam distillation. Upon completion of the process, there will be a stand of water and oil, which can then be separated. The products - essential oil and hydrosol (the scented distilled water can be used in various applications. It can be fun and very useful for household and personal body products. Best wishes!