Talk:Fractional distillation

Flawed example

Before I go bold and remove the ethanol-water example, anyone interested in choosing something else and with a more accurate explanation? Here are two reasons:

• In fractional distillation, the vapors and liquid have varying equilibrium concentrations along the vertical fractionator, with the most volatile component being most abundant at the top. However, since the batch setup in the example will slowly deplete in the more volatile component during operation, its concentration at the top of the column will continuously decrease in time and there will be no sharp "switch" to the less volatile component. Only the first few drops condensed out from this batch fractional distillation setup will have a relatively high purity in the most volatile component. The explanation in the text is better fit for the simple batch distillation (on which there is no article yet).
• The particular ethanol-water mixture will form an azeotrope containing about 95% ethanol, which is actually more volatile than pure ethanol. See for example http://www.ces.purdue.edu/extmedia/AE/AE-117.html. So this will be the component that will separate first at the top of the column. --Unconcerned 23:52, 17 Aug 2004 (UTC)

I had the same thought while reading the example. It seems sufficient for its scope (lab benchtop distillation), however the explanation and results described seem to confuse the concept of batch distillation with continuous process distillation. Perhaps a separation of components with less affintity for one another such as a C3 splitter (propane-propylene splitter) would be more appropriate . . . C3 splitters are the biggest distillation towers I´ve ever seen (with respect to the number of trays 200+).;--StateOfTheUnion

trays vs. random packing

So can someone explain trays in the process (and how that would fit in with different faction outlets), and what they're good for, and why you might want raschig rings or ordered packing instead of them (in certain situations)? And link it up to reflux as well? I'd like to learn more about fusel alcohols and how they're taken out of ordinary distillation. I was pleased to learn about azeotropes, but there's more that I could learn...
~ender 2005-10-04 22:12:MST

Logical Inconsistency

The following sentence is illogical, and is factually flawed:

" In this example, a mixture of 95% ethanol and 5% water boils at 78.2°C, being more volatile than pure ethanol, so the ethanol cannot be completely purified by distillation."

The two concepts may be true from some point fo view (completely purified? Fine precious metals are never better than 99.98% pure, so how pure is "completely purified" ethanol? Can any method produce it? I think 99% or better is called "ethanol absolute", perhaps that's "complete purification".), but they do not follow from one another as written.

The reason that complete puriication by distillation is impossible has little to do with the boiling point, it's about both water and alcohol evaporationg into a less than saturated gaseous medium, and how it's impossible to saturate the gas with water and keep the alcohol at less than saturation. There is no temperature and pressure that will allow the distillation to perfectly separate the liquids. The purity of the distillate can be improved by distillation at a temperature significantly below the boiling point of either water or alcohol or of the mixture by taking advantage of evaporation and partial pressures in the surrounding gas.

Thinking about this, it would be interesting to see what happens in a mixture at around -20c, where the water has turned solid and the alcohol is still a liquid, to use vacuum distillation to take off the liquid alcohol, leaving the solid water ice behind. Clearly this would be expensive and impractical in a commercial operation, but it may be a method by which ethanol is completely purified (whatever the boundary of that could be) by distillation, in contrast with the statement in the article. Furthermore, absolute ethanol is obtained by distillation with benzine.

I have also identified that this is actually a misquoting/misunderstanding of the entry from the Columbia Encyclopedia - http://www.bartleby.com/65/et/ethanol.html - where they refer to simple distillation. Presumably the writer did not understand that the meaterial lost integrity when the word simple was omitted to avoid misappropriation of the material. Clearly this should be rewritten. Octothorn 02:51, 10 January 2006 (UTC)

See freeze distillation, where alcohol and water cannot be seperated by freezing. (Maybe vacuum freeze distillation might work?) :~ender 2006-01-31 19:29:PM MST

Yes, the freezing won't work so well either. but the not on the benzene is correct. that is how you make "absolute ethanol." which i assume is as pure ethanol as any normal person would care to get. those azeotropes aren't much fun to deal with most of the time. —Preceding unsigned comment added by 71.92.101.14 (talk) 04:40, 2 October 2009 (UTC)

This is just an example. No distillation can make something 100% pure. — Preceding unsigned comment added by SecretSpectre (talk • contribs) 23:49, 12 November 2022 (UTC)

Bunsen Burner

Who uses a bunsen burner as the heat source for a fractional distillation? Most of the time, you risk setting your lab bench on fire! —Preceding unsigned comment added by 64.53.218.27 (talk • contribs) 7 February 2006 (UTC)

...I use one. Kilo-Lima|^(talk) 14:32, 23 April 2006 (UTC)

Depends what you're fractionating really. Then again, strictly speaking it's probably safer to move away from the open flames, but if you need fast powerful heat...GreatMizuti 13:47, 29 July 2006 (UTC)

I have never, ever seen a bunsen burner used for destillation. That was an ancient practice. 70ies? 50ies? WWII? --Maxus96 (talk) 21:21, 28 August 2016 (UTC)

I routinely did it in the 90s, and still do occasionally for special purposes...hard to beat a micro-burner for quick high heat at a small spot on weirdly shaped vessels. DMacks (talk) 21:27, 28 August 2016 (UTC)

only one ok it's good secure more safely 117.230.22.255 (talk) 06:41, 14 October 2024 (UTC)

Deleted expansion stub

I deleted the expansion stub because:

• I expanded the article by adding a schematic diagram and a discussion of reflux used in large-scale industrial towers.

• I expanded the "See also" section considerably by adding links to the articles that deal with the various other types of distillation such as azeotropic distillation, freeze distillation, extractive distillation, etc.

In my personal opinion, what this article needs is to downplay its focus on laboratory-scale glassware distillation and upgrade its focus on the use of large-scale fractionators in industry. Perhaps that could be done by simply reversing the location of the glassware section and the industrial section?? What do others think? - mbeychok 00:08, 5 June 2006 (UTC)

Categories

Fractional distillation is indeed a vital part of the oil industry, if you don't think it fits under Industrial processes, then, quite frankly, you are quite mistaken. GreatMizuti 00:47, 18 September 2006 (UTC)

GreatMizuti, good for you! I agree thoroughly. Here is what I posted on Wsloand's Talk page:

I am curious as to why you are removing the "parent categories" from a number of articles. Regardless of the Wikipedia Manual of Style, I thought one of the prime purposes of Wikipedia was to help unkowledgeable readers and/or newcomers to Wikipedia find what they are looking for as easily as possible. I would point out that the Wikipedia Manual of Style is not written in stone and is not meant to be completely inflexible. It is meant to be guidance. Please explain your thinking on this subject. Thanks, - mbeychok 00:30, 18 September 2006 (UTC)

As an addendum to my above posting here is a quote from the Manual of style:

"This Manual of Style has the simple purpose of making the encyclopedia easy to read by following a consistent format — it is a style guide. The following rules do not claim to be the last word on Wikipedia style. One way is often as good as any other, but if everyone does it the same way, Wikipedia will be easier to read and use, not to mention easier to write and edit. In this regard, the following quotation from The Chicago Manual of Style deserves notice:

Rules and regulations such as these, in the nature of the case, cannot be endowed with the fixity of rock-ribbed law. They are meant for the average case, and must be applied with a certain degree of elasticity." - mbeychok 00:30, 18 September 2006 (UTC)

Trays

Is it possible to use a spiral for the column?Arnero 19:01, 22 October 2006 (UTC)

Arnero, If you are asking about industrial fractionators, I don't understand what you mean by a spiral. Industrial fractionators (or distillation columns) usually use vapor-liquid contacting devices known as trays (or plates) or some type of packing. There are various types of trays ... the most prevalent are those using either bubble caps or valve caps. As for packing (as noted in this article), it may be random dumped packing or structured sheet metal. - mbeychok 19:25, 22 October 2006 (UTC)

I suspect he's thinking of a graham condenser (for example, this Ace Glass item [1]). That's very good for condensing a vapor, due to lots of thermal contact with the cooling jacket, but I don't know why it would be a good for the fractionating column. Alternatively, there are spiral packing techniques for straight Liebig condensers. DMacks 08:00, 23 October 2006 (UTC)

On the farm

While reading this article i came across the following section:

"Alternate set-ups may utilize a "cow" or "pig" which is connected to three or four receiving flasks. By turning the "cow" or "pig", the distillates can be channelled into the appropriate receiver. A Perkin triangle is versatile piece of apparatus that can be also be used to collect distillation fractions which does not require a cow" or "pig" adaptor. A Perkin triangle is most often used where the distillates are air-sensitive or where the fractions distil and are collected under reduced pressure, but can be used for a simple and fractional distillation."

Now, i assume that cows and pigs refer to some kind of chemistry equipment, mabey glassware or whatever. However, without previous knowledge of the subject and no links, it makes this segment confusing at best. perhaps someone who actually knows what this means can throw a link or two in there? 204.82.251.197 (talk) 14:30, 9 February 2009 (UTC)

See [2]. Shame we don't have a picture... but that can't be helped. --Rifleman 82 (talk) 14:42, 9 February 2009 (UTC)

25º?

in the intro, it says that if the boiling point difference is greater than 25ºC, simple distillation is used. simple distillation cannot produce a reasonably pure (<5% impurities) sample unless the boiling point difference is greater than 100ºC. According to Introduction to Organic Laboratory Techniques: A Small-Scale Approach (ISBN:978-0534408336), 108ºC is required to achieve separation by simple distillation. There is a table in the book (page ~751) that has a list of how many boil/condense cycles are required for various boiling point differences. It also calls the boil/condense cycles that occur in the column "theoretical plates." the table ranges from bp difference of 108º with 1 theoretical plate to a bp difference of 2º which requires 100 theoretical plates. —Preceding unsigned comment added by 71.92.101.14 (talk) 04:59, 2 October 2009 (UTC)

First line correct

The first line as written isn't strictly correct. There are at least a couple things wrong with it, and I believe the most important is the omission of the use of the term fractionating column, since fractional distillation is distinguished from other types of distillation based on the use of a fractionating column such as a Vigreux column, not the fact that it's a method of separating mixtures into fractions. All types of distillation separate the pot into fractions, so this is not characteristic of fractional distillation. Also not entirely correct is the description of the mixture. This technique will give fractions of a pot but not if one of the components of a mixture is, say, a gas. A gas will leave open apparatus and escape and not be captured as a fraction. Very often, fractionation of liquids is wanted. "A mixture" without further characterization is very general. I am willing to rework the first three sentences if no one else would like to take the opportunity to do so. I will come back in a few days to see if an edit has been made, and if not I'll give it a shot. 2603:900A:1C0B:7700:9D9F:26BA:28CF:552B (talk) 09:08, 14 April 2019 (UTC)

Fractional condensation

   I think nonplussed is the adjective that describes my mental state, upon noticing our lack of not (only an article, but in fact) even of a redirect, for this perfectly predictable consequence of the topic-worthiness of the accompanying article. I hasten to add that even tho I may in fact be nuckin' futz, there is at least an insane logic to my assertion, and I may even explicate that before shuffling off this [[wikt:mortal coil]|].
--JerzyA (talk) 23:42, 30 June 2019 (UTC)

It's silly to think that a mere edit in WP could constitute a monument to oneself, but here I am: suggesting (as at least some, of at least we males, of my pretentious species are wont to do, especially in anticipation of [[shuffle off|shuffling off Wikt:this mortal coil), that this one might just be my own. Still, "Vanity, thy name is" ... something or other ... oh, I fergit what .... JerzyA (talk) 00:07, 1 July 2019 (UTC)

 &nbsp Oh, yeah:[[wp:Steve_Martin#Nuckin'_futz|]] (It's tuff, when can't edit away yr talk typos, which, if I groused abt editing facilities on talk page's being inadequate, is the other side of the coin abt editing talk being sadly identical wit editing an article. (1)I predict that no one will give a damn abt my long thot analysis of the design issues, as editor/software-engineer (2) I can't guess whether (2a) That's fine, bcz there are still pros at WMF with adequate free attention to work it out, or (2b) that's tragic bcz fanboys seem adequate to maintain process and initiative, despite Hari Selden's lamented retirement and decline, or (2b) tragic, bcz real imaginative and professional programming and data-management capabilities have still not been pushed to a point where the pro bono publica structures in place can continue to exploit the continuing refinement and elaboration of the underlying concept toward its full realization.IMO, history favors stagnation, but we can only, predict, and kick in our own. two-bits, whether of hope and perhaps new heights, and/or of despair.and perhaps stagnation ending in collapse.
--JerzyA (talk) 04:06, 1 July 2019 (UTC)

 &nbsp:&nbsp:For example (Re le esprit d'escalier:) I wrote, probably Hari Selden and the best I can do about it is to append comments like this. If I were as clever as I like to imagine, I'd have written some WP:essays since the early days, and exploited the wiki capabilities more in the WP:wikipedia nanespace, instead of composing essays on talk pages. Too late?.
----JerzyA (talk) 04:41, 1 July 2019 (UTC)