Vacuum distillation | Purpose & how it works - H2O GmbH
Jun. 16, 2025
Vacuum distillation | Purpose & how it works - H2O GmbH
Water is present in virtually every industrial process; it is not only used for manufacturing products, but also for diverse purposes accompanying the production process. These can be cleaning, processing, diluting, cooling, or transporting.
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Water is essential in the production of almost any product, whether it is a car or a toothpick. A vast amount of water is spent in the production of paper, food, and chemicals. This so-called industrial water generated in production processes is usually contaminated after the production process and polluted with heavy metals, oils or salts among other substances of concern.
The contaminated water can cause severe environmental damage if it is returned to the public supply without being purified beforehand. Therefore, an efficient long-term strategy is to purify the contaminated water directly in the facility where it was produced, since the contamination usually makes up only a small fraction of about 2-3% of the wastewater and the purified water can be reused directly in the facility as well.
A vacuum distillation plant is perfectly suited for this purpose as it is highly energy-saving in comparison to atmospheric evaporation.
1. What is vacuum distillation?
Vacuum distillation explained simply: The wastewater is evaporated, the dirt remains behind, the rising steam is free of impurities. The condensate, also called distillate, can be reused in production. In this way, 100 % waste water produces around 98 % cleag an water and only 2 % residue, which can be disposed of at minimal cost. The underlying physical principle is termed separation of substances according to boiling point differences.
This vacuum distillation method also saves energy, because water evaporates under vacuum at 80 degrees Celsius instead of 100 degrees Celsius. This has a major impact on the amount of energy consumed. Due to the use of heat exchangers and the reuse of the evaporation heat in the system, the set-up of a vacuum distillation consumes comparably little electricity. You can find another article about cost efficiency here.
2. Evaporation vs. vacuum distillation
Evaporation is a very obvious phenomenon, as it can be observed very easily in nature and also in the household, e.g.,salt is left behind when salty water like seawater evaporates. The evaporated water falls back to earth as clean, salt-free rain. Another example from the household would be the water vapor that collects as condensate on the lid of the pot. The condensate is pure water and does not contain any salt present in the pasta water.
Part of the vacuum distillation process is called vacuum evaporation. Vacuum evaporation is a process in which a liquid is made to evaporate at a lower temperature than normal. The vacuum distillation principle is to lower the atmospheric pressure in a vessel containing the liquid below the vapor pressure of the liquid. This process can be applied to any liquid. However, the process of vacuum evaporation is usually associated with the effect where water can be brought to a boil at normal room temperature. An advantage of the method is that also energy of compression can be used for the evaporation (mechanical vapor recompression) and that no external energy is required for the condensation.
But probably the most important advantage of vacuum evaporation is the unspecific separation based exclusively on boiling points, which means that extremely diverse chemicals can be separated very effectively; the range covers for example heavy metals, salts, but also organic compounds like oils and fat. Vacuum evaporation can also be used to prevent the breakdown of liquids that should not be exposed to high temperatures.
3. What is the purpose of vacuum distillation?
Short path vacuum distillation is a very energy-saving technique for removing impurities from industrial wastewater. Since dirty water usually consists of only 2-3% or less of contaminants, vacuum distillation produces 98% pure water that can be returned to the production cycle.
This not only saves costs in the supply of new water for production, but also mitigates the costs incurred for external disposal services to an extreme degree.
Find out more about the applications and benefits of industrial vacuum distillation.
4. How does vacuum distillation work?
In the vacuum distillation process, the industrial wastewater is fed into a heat exchanger and evaporated under vacuum. The heat exchanger consists of a bundle of tubes in which the wastewater is divided into smaller volumes to make it easier to evaporate. The applied vacuum lead then to a modification of the boiling point. This allows water to evaporate at around 185 degrees Fahrenheit (85 °C) instead of 212 degrees Fahrenheit (100 °C) under atmospheric pressure.
All substances with a higher boiling point than water remain in the evaporation residue. The resulting vapor is then fed into the vapor compressor. It creates compression heat, which heats up the steam to 248 degrees Fahrenheit (120 °C). From the vapor compressor, the compressed steam hits the tube bundle again where the cooler wastewater is fed, condensing on the outer wall of the tubes. As a result, the steam reverts to liquid clean water and can be discharged from the system or returned to the production process. The contaminated evaporation residue is then drained off.
5. Pre- and aftertreatment in the process of vacuum distillation
The heart of the wastewater treatment system is the vacuum distillation unit. Depending on the nature of the wastewater contamination, pre-treatment and post-treatment may be necessary.
The pretreatment
Pretreatment can include a belt filter (or inclined belt filter), which is used to remove floatable and filterable solids from the water by means of a filter fleece selected to match the solids concentration and viscosity of the wastewater to be treated.
Pretreatment by a neutralization plant protects the microorganisms that break down organic substances in the wastewater, e.g., in the biological stage of a wastewater treatment plant. Microorganisms react very strongly to fluctuations in the pH value.
In a neutralization plant, substances such as hydrochloric acid or caustic soda are often used to produce a neutral liquid with a pH of 7 corresponding to that of water.
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The aftertreatment
In the aftertreatment, ultrafiltration can be used. In this process, the pores of the semipermeable membrane (which can only be penetrated on one side) are smaller than in microfiltration, but larger than in nanofiltration.
In ultrafiltration, the treated dirty water is forced through plastic tubes at up to 10 bar resulting in particles, bacteria and viruses being collected in the pores of the filter tubes. The result is an absolutely germ-free water. The membranes are mainly made of very low-cost materials such as cellulose acetates or polyamides.
6. Other vacuum distillation techniques and products
The H2O VACUDEST vacuum distillation system is very efficient and space-saving since technologies adapted to meet individual needs for improving water quality are already built into the machine ex works.
These are for example:
Destcontrol
The H2O DESTCONTROL measures the pH value of the water not like conventional units in the feed, but instead in the purified distillate. The pH-value of industrial wastewater often differs drastically before and after evaporation as after-reactions can be triggered during the evaporation process.
The DESTCONTROL doses a neutralizing agent directly into the VACUDEST evaporator and thus compensates for any after-reactions that may occur. This not only ensures a constant distillate quality, but also makes an upstream continuous neutralization obsolete.
Clearcat & Purecat
This additional option offers the possibility of treating industrial wastewater containing oil and grease in a single process step without additional manpower. The modules normally save an extra upstream oil separator.
In addition, this technology does not require any energy or auxiliary materials, as it is based on catalytic and physical effects. Clearcat and Purecat technology is seamlessly integrated into your vacuum distillation system and requires no additional space.
Clearcat technology lowers COD (Chemical Oxygen Demand) levels in wastewater to the point where they are 60% better than with other conventional vacuum distillation systems.
If you are aiming for recirculation in almost all industrial sectors, use the Purecat module in addition to the Clearcat. This can reduce the COD value by a further 50%.
VACUDEST ZLD 300
Our VACUDEST vacuum distillation system already reduces the amount of wastewater by up to 95%. However, the remaining residual water content in the residues can sometimes make complete disposal difficult. This problem is eliminated by the VACUDEST ZLD post-concentrator.
Vacuum distillation pumps
In order to achieve a consistently high level of separation of the various substances during vacuum distillation and to ensure that the process is carried out reliably, it is important that the vacuum in the evaporator is sustained very precisely. Therefore, a high-quility pump is needed. In connection with vacuum distillation there are very many different pumping technologies in use. If you want to know more about them, please read the article Vacuum distillation pumps.
7. Why should a company use short path vacuum distillation for water treatment?
Vacuum distillation is not only a very environmentally friendly process due to the comparatively low energy consumption of evaporation, but also very economical, as one can see in this comparison to disposal of industrial wastewater.
Due to the recurring use of the water in the company's own production, very little water has to be sourced from new. However, the savings in disposal costs are the decisive factor, which means that a vacuum distillation plant usually amortizes after about two years.
Due to the low energy consumption, a vacuum distillation plant is also economically ahead of other water treatment technologies. In terms of fresh water costs, operating costs, and costs for the removal of evaporation residues and filter cakes, the vacuum distillation plant is ahead of other types of treatment such as chemical-physical treatment. Here you can find a comparison to alternative treatment methods.
6. Vacuum distillation problems
International companies such as MAN and Audi rely on the H2O VACUDEST system on a daily basis, as it scores in areas such as surface technology, the metalworking and metal processing industries, as well as in waste disposal and aviation companies. The Clearcat and Purecat technologies also show their unique strengths when it comes to oily industrial wastewater.
To learn about the limitations of vacuum distillation, as well as our advice for the optimal wastewater solution, please read our article Application limits of vacuum distillation.
Vacuum Distillation Confusion - Powered by XMB 1.9.11
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posted on 10-1- at 23:50 Vacuum Distillation Confusion
I would have to say that I'm still very much a beginner. I would like to think I'm getting better, but scenarios such as what happened tonight prove otherwise.
Recently I've notice that during vacuum distillation, I don't get that much lower of a boiling point separation, as would normally be expected. I've attributed this to not putting sufficient grease at the joints.
Tonight I decided to vacuum distill water and see if I could get better results by greasing the joints more. So I added a nice even layer of grease at every joint.
The water was able to boil at under 50C at 23in Hg. The boiling point seems lower, but now I get an inconsistent drip rate. I will get like 5 quick drips, then nothing for 30secs, then a few more quick drips.
This went on and on, no matter what I did. I would increase temperature, but nothing better would happen. I increased temps drastically, but still no steady drip rate.
A few drips would come over together, then nothing. I can see, what looks to be air entering into the top joint of the condenser.
The only thing I can figure is this could be causing a negative vacuum, preventing a steady drip rate.
Has anyone encountered similar? I mean, I've vacuum distilled before and I don't recall all the hassle. I spent like over two hours trying to vacuum distill like 100ml of water. TheChemiKid
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posted on 11-1- at 05:13
First off: This should have been posted in Beginnings.
Here is a probable answer to your question: If your vacuum pump is a rather cheap pump, the vacuum will almost definitely fluctuate a lot during the distillation. Even very expensive diaphragm pumps can still fluctuate slightly.
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posted on 11-1- at 06:57
The pump is fairly expensive. It is a rocker 500 and it seems consistent with the vacuum, at least from the gauge at the vacuum.
Should I be striving for absolutely no leaks in a vacuum distill?
At such high vacuum, should I be using something besides Vaseline to grease?
I've seen things like "Dow High Vacuum Grease", I just didn't think it was a must. BromicAcid
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posted on 11-1- at 07:04
First set of questions. What kind of trap are you using? Are you cooling your receiver? What kind of condenser do you have in line? If you are not condensing the vapors and keeping them condensed, put another way, if the vapors are making their way to the vacuum pump, then you will see these surges. In these cases the system is being pulled under vacuum by removing the gases in the system. The material begins to distill, vaporizing and turning into a gas, this new gas fills the system. When this gas does not condense then the pressure in your system goes up, the distillation stops, and the pump has to work again to remove this gas to get the pressure back down and the cycle repeats.
Edit: If you are able to measure the vacuum (since you mention you had a reading of 23 inches of mercury) simply measure the vacuum on the pump itself with the pump not connected to anything. Now assemble the glassware without anything in it but properly greased. Connect the pump to the setup and allow it to pull down for 10-30 minutes, now measure the vacuum on the setup, A properly greased and sealed setup should give an identical reading to the pump on itself.
Edit 2: You said you were boiling water at 50C and 23 in Hg, when I used the nomograph on that value I see you were still supposed to be boiling in the 90's. To boil even in the 50C range you're going to need pressures of ca. 4-5 inHg. Something would have to be notably wrong to get these sorts of values with a decent vacuum pump, I don't think you would be losing this much due to leaking joints, and you should hear any sort of leak. Then again maybe your vacuum gauge is wrong.
[Edited on 1/11/ by BromicAcid]
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posted on 11-1- at 07:34
You should definitely invest in some Dow High Vacuum Grease. It will last you a long time, and is very chemically resistant. For almost any distillation, this is a must. Even though it is expensive, a little bit goes a long way.
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gravityzero
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posted on 11-1- at 08:34
Thanks for the comments.
Bromic, I'm doing this as a test with water and I'm using a very simplistic vacuum distillation setup.
I'm using a 250ml boiling flask, connected to a 3-way adapter, connected to a 200mm liebig condenser, connected to a vacuum adapter, connected to a collection flask.
I'm trying this again as I type. I have the vacuum wide open and the vacuum is causing the water to boil at around 43C. For this to happen, it is a certain that the vacuum is working.
The vacuum gauge measures a kPa value of 90, which converts to roughly 26inHg.
The distillate condenses, and at this stage there is no trap being used. The vacuum itself has a built in moisture trap that does not appear to be collecting any vapor.
After resealing the joints this morning, I no longer see bubbles at any of them. I allowed the vacuum to set for a few minutes before I proceeded to distill and I think that helped.
I am still getting a very inconsistent drip rate. I will get maybe 5 drips to come over at once, then nothing for better part of a minute, then 5 more drops, then nothing.
When distilling at normal pressure, I can always obtain a steady and consistent drip rate.
I feel like the condenser is working correctly. I don't think any vapor is escaping, but I have had that occur in the past.
I also think the product being distilled is just as clean, it is just unpredictable and takes forever.
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posted on 11-1- at 09:54
Again, something is wrong with the data you are giving. By the pressure provided your water should be boiling in the 90s, at the temperatures you provided your vacuum should be in the ballpark of 13 kPa (since your vacuum is reading in kPa). Actually... atmospheric pressure is about 101 kPa, you're reading 90 kPa... does the scale read zero at atmospheric pressure? Is it showing the pressure drop as say -90 kPa in which case the actual pressure would be around 10 kPa which would at least make sense with the rest of it.
My suggestion still holds, empty out the water, dry your glassware, and vacuum check the setup. If your setup holds vacuum without the water then your issue is that you are not condensing the vapors and it is killing your vacuum. Just because there is a water trap doesn't mean it will remove gross water contamination.
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posted on 11-1- at 10:25
You are correct to say -90kPa. Sorry for not posting the negative, but a vacuum distillation will always be done at reduced pressure.
I will try this later with a 400mm liebig and see if it gets any better.
I know what you are getting at and I've had vacuum distillations in the past where vapor was noticeably escaping the setup.
If it ain't one thing it's another. I appreciate all comments and I will press on.
Hopefully I haven't caused permanent damage to the vacuum.
Thank you BromicAcid for all your assistance. BromicAcid
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posted on 11-1- at 10:33
Quote: Originally posted by gravityzero You are correct to say -90kPa. Sorry for not posting the negative, but a vacuum distillation will always be done at reduced pressure.
Yes, it is valid to say that a vacuum distillation will always be done under reduced pressure however in literature you will not see negative values for pressure in literature or even on this site. Atmospheric pressure is 101 kPa, not zero. Your reading of -90 kPa should be subtracted from this value to give your actual pressure of 11 kPa. -90 is just confusing, the only time I see negative numbers with pressure involve PSI, there is a PSIA where the value starts at 0 (absolute vacuum) and a PSIG where 0 is actually atmospheric pressure. But even they are differentiated by a difference in units to avoid ambiguity.
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posted on 12-1- at 17:41
Quote: Originally posted by gravityzero I will get like 5 quick drips, then nothing for 30secs, then a few more quick drips.
That's about how it is, though I'd say you need to either turn up the heat or the vacuum a little if you want things to go faster; it's a solid rule IMHO. A lot of this has to do with condensate buildup in the apparatus more than anything with my apparatus, but in general weird little pressure swings should occur in the condenser especially; raw imperfect equilibrium between liquid and gas and heat and suddenly things condense if your condenser can handle it. Given how violent things are in the pot, it shouldn't be too surprising.
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posted on 15-1- at 15:33
My first thought was that you're simply at the mercy of superheating/bumping, something exacerbated under reduced pressure. A push pull circumstance can ensue.
A really good exercise that helps one understand how dynamic and oscillating the pressure gradients within a distillation setup are is to setup for a vacuum distillation, using water, without connecting the vacuum hose. Then begin the distillation and get it running at a even constant rate. Then place a small balloon over the vacuum outlet on the setup.
You will notice an oscillation within the balloon.
Back to point, stir your boiling water or put some pumice, boiling stones or best yet a capillarily to the bottom of the flask that allows slight air ingress.
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posted on 15-1- at 16:13
I have a different idea as to what might be the problem with regards to inconsistent dripping. Perhaps a little of the grease you applied to the joints found its way inside the glassware, leading to a band of grease around the inside of the joint. Because grease is hydrophobic, perhaps the water slid down the condensor and was stopped by the band of grease until sufficient water had built up to overcome the repellent force the grease provided.
Once that force had been overcome, all the water that had built up behind the grease (several drips worth at least) would flow over the grease and into the condensor, and the cycle would start again
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posted on 15-1- at 16:25
I've run several vacuum distillations during various syntheses. I remember some pressure fluctuations but not to where it was overly objectionable. If your vacuum source is an aspirator variation in water pressure would result in vacuum fluctuation.
If your surging is caused by fluctuations in the vacuum source you could try adding a "vacuum reservoir" to your system. This could be any relatively large vessel, such as a 1-liter Buchner filter flask, that is capable of full vacuum. This could be teed into your system with a piece of vacuum hose.
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posted on 17-1- at 09:01
The water did appear to be bumping somewhat. It was being stirred and even had a boiling stone, but it still appeared to be having trouble boiling properly. I've also read that insulating the boiling flask might help.
I'm trying to understand the core concepts and avoid just getting it to work. I'm using the same methodology for determining condenser length.
My understanding is the higher the boiling point, the shorter the condenser.
I've seen materials with atmospheric boiling points above 200C being distilled without a condenser and assumed this was the reasoning. S.C. Wack
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posted on 17-1- at 15:37
Quote: Originally posted by gravityzero The water did appear to be bumping somewhat. It was being stirred and even had a boiling stone, but it still appeared to be having trouble boiling properly.
Another guess the unprovided detail thread then. In that case, you're not getting condensate because you're not getting evaporation except on superheating. Plus: is that stirring...magnetic? Magnetic stirring and a boiling stone for this? BTW...no one can see air enter clean undamaged very lightly greased tapered joints, unless whoever finished the glass was Chinese or tripping balls...water really is suckier than other solvents to distill...use the same grease everyone else does, to fit in if nothing else.
It should not be "bumping somewhat", it should be bumping constantly and unambiguously, unless the flask is rotating or stirred hard overhead.
There may be some practical reason why 95% of organic chemistry books have capillary tubes coming in from the top or through an extra neck as the #1 option. IMHO ghetto means borosilicate tubing that barely fits though a thermometer joint, a blowtorch, scissors, and electrical and/under teflon tape, and humbly suggest giving something along those lines a go.
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posted on 3-2- at 09:23
I have a question regarding the boiling points and pressure. I have vacuum pump that generates quite hard vacuums, as low as sub-millibar scale, according to the factory. I haven't tested it though, but I though that if I have high boiling liquids, like 150-300C, is the boiling point of the liquids linear? A calculator dictates that a liquid boiling 200C will boil at whopping -70C when using sub-millibar vacuum. This causes problems with condensation, of course.
So, do I need to get vacuum regulator, or are there some physical laws regarding the boiling points at very low pressures that interfere with this calculation? I've heard that water doesn't actually boil at very low pressures at less than -50C or something. Is this true? BromicAcid
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posted on 3-2- at 14:46
Look up a nomograph and you will be able to correlate reduced pressure to boiling point. You do not need a vacuum regulator so much as just a way to bleed air or better yet nitrogen into the system to help keep the vacuum consistent. Never heard of water not boiling well at low pressures though.
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posted on 4-2- at 03:46
What I was trying to say is this:
https://upload.wikimedia.org/wikipedia/commons/thumb/0/08/Ph...
That water exists only in solid and will not evaporate at certain temps and pressures? Does this kind of action apply to other stuff too? BromicAcid
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posted on 4-2- at 04:17
As a distillation progresses it requires a constant input of heat to replace the energy lost of components distill out of the system. If you had water under full vacuum and were really ripping it out of the system, faster than you were even putting energy in, and the pot kept getting cooler your distillation will slow because your system does not have much energy, but you will still be pulling off water. Your other issue will be your heat transfer will not be as good as the water solidifies. The only difference through is that you will not have a liquid phase, you will be subliming your water instead of distilling your water, but that does not magically mean that water will stop being removed from the system.
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posted on 4-2- at 17:30
Well, then I've gotta get the manual valve to adjust the pump capacity directly. organicchemist25
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posted on 16-2- at 17:03
I see this thread is current, so I am hoping someone would help clarify something. I have done searching on here and the web and various organic literature, including Vogel and Zubrick.
Here is my question. And basically a yes or no answer will give me the answer I need to move forward.
When I hook up and prepare for vacuum distillation, do I seal the system completely up(which seems so wrong). or do I have a slight bit of air (or gas if needed) controlled by something like the hoffman clamp on a hose or valve shut off on one of the glass joints of the flask ? I feel it needs to let a tiny bit of either air or gas in, as vacuum is being applied to it.
Here is some pics of the lab, since I think this is my first post. I have used this site for a lot of answers I was looking for. I hope to be able to repay by providing relative info to help others out.
I have a corning hot plate and stirrer, I have a single stage pump, as well as an aspirator, high vacuum joint grease and a Meriam Instrument digital manometer. I also have a Hoffman style hose clamp if I need it to regulate the input of outside air or a gas. I have had first semester Organic, but know quite a bit more than that from my own reading and experimenting.
Vacuum distillation is about the only practice I am not knowledgeable in at my current level of experience. I really want to to get comfortable and experienced with it.
We NEVER did a vacuum distillation in my lab. I even asked my prof about vacuum distillation and they really couldnt answer my question.
And any additional info or tips would be greatly appreciated.
And if someone could identify the glass apparatus I am holding? I have no idea what it is and what it might be used for. I was told it was a custom piece when I bought it.
Thanks.
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posted on 16-2- at 18:23
There are vacuum controllers my favorite being the faucet. Next favorite: not tightening the connection of the pump that tight. Not sure what's wrong with full vacuum. If you're going to run air or whatever in the system might as well run it through a not so fine capillary to the bottom of the liquid. Maybe this is faster than standard vacuum distillation if the vacuum, heating, and cooling are up to it?
But one may often regulate heat instead of vacuum.
[Edited on 17-2- by S.C. Wack]
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Quote: Originally posted by organicchemist25 I see this thread is current, so I am hoping someone would help clarify something. I have done searching on here and the web and various organic literature, including Vogel and Zubrick.
Here is my question. And basically a yes or no answer will give me the answer I need to move forward.
When I hook up and prepare for vacuum distillation, do I seal the system completely up(which seems so wrong). or do I have a slight bit of air (or gas if needed) controlled by something like the hoffman clamp on a hose or valve shut off on one of the glass joints of the flask ? I feel it needs to let a tiny bit of either air or gas in, as vacuum is being applied to it.
Here is some pics of the lab, since I think this is my first post. I have used this site for a lot of answers I was looking for. I hope to be able to repay by providing relative info to help others out.
I have a corning hot plate and stirrer, I have a single stage pump, as well as an aspirator, high vacuum joint grease and a Meriam Instrument digital manometer. I also have a Hoffman style hose clamp if I need it to regulate the input of outside air or a gas. I have had first semester Organic, but know quite a bit more than that from my own reading and experimenting.
Vacuum distillation is about the only practice I am not knowledgeable in at my current level of experience. I really want to to get comfortable and experienced with it.
We NEVER did a vacuum distillation in my lab. I even asked my prof about vacuum distillation and they really couldnt answer my question.
And any additional info or tips would be greatly appreciated.
And if someone could identify the glass apparatus I am holding? I have no idea what it is and what it might be used for. I was told it was a custom piece when I bought it.
Thanks.
Wow, what a beautiful home lab! Is that a fume hood? Is this structure built inside a garage? Is that a dehumidifier I see there in the corner?
As for vacuum distillation I *believe* that there is not necessarily a need to allow air into the setup, unless you want a slightly higher pressure in the setup than the minimum your vacuum pump will produce. Beware, too, that you need some kind of trap between your distillation apparatus and your vacuum pump - especially if the pump is not a specialized chemical-resistant one. It's typical to have a desiccant tube in line with the pump along with something to catch particulates or large drops of liquid which can be accidentally ingested (this will often be simply a container which draws gas from the setup through a tube which opens at the bottom of a receiving vessel and then connects the vacuum pump near the top so that a few droplets are not likely to get sucked all the way through). For organic vapors, this same kind of setup is often cooled down by an alcohol/dry-ice mixture or even LN2 to form a cold trap to condense the vapor very quickly before it can make it through into the pump. Beware that using LN2 absolutely requires that the entire apparatus be free of air or other oxygen sources as LOX will condense at LN2 temperature and react explosively with anything flammable.
Finally, beware of implosion hazard with vacuum. Vacuum-rated glassware is typically quite a bit thicker-walled. Even with special glassware (and especially if you are doing this with normal glassware - but never with the really thin-walled cheap stuff!), you should have an additional layer of implosion protection such as a polycarbonate shield or mesh around each piece of glassware. Panache
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posted on 17-2- at 03:23
Why is it you feel you require an air bleed, this seems contrary to the entire concept of vacuum distillation. To control the vacuum having a needle valve t-pieced into the line as close to the pump as possible is the simplest solution, variously sophisticated manostats being the least simple.
Only pull a decent vacuum on spheres, tubes, pears and their interconnecting paraphernalia unless the item is specially strengthened for vacuum (such as vacuum flasks for Büchner funnels). Schott laboratory reagent bottles can also take a full vacuum.
My one implosion on a two litre erlenynmer, where I mistakenly became distracted and the slight vacuum I was using to draw away some evolved gases went deeper than expected as the gases stopped evolving has scarred me forever. The sound/boom was odd and the ml or so of solvent and slight lacryomater went over everything within three metres.
Luckily my back was turned!
organicchemist25
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posted on 17-2- at 10:10
Thank you everyone for replying.
I do have a solvent trap and a inline vacuum trap for when I hook up the vacuum.
That is a A/C and dehumidifier combo.
I guess the reason why I was think about letting just a tiny bit of air or gas in is so that is was never a closed system. I have seen pics that had a needle tip submerged with tiny bubbles in the solution. I just figured, obviously the vacuum would be a lot higher than the tiny amount being input onto the system. I will attach a pic or two that I have seen that gave me the assumption at one time about letting air/gas into the system.
I have never been able to find a solid reference as to what I was looking for. Maybe I have been over thinking it. I just definitely what to have a good understanding and what exactly I have to do to do it as safe as possible. I do know not to use thin walled and I definitely know the risk of implosion. That is definitely why I wanted to ask the experienced.
Oh, and can anyone ID that vigreux column and graham condenser combo piece in the last picture I attached? and what it is used for?
Thanks
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