Talk:Osmosis/Archive 1

Archive 1

Archive 2

The simple explanation here is misleading

Wow the explanation on this site is terrible! Can't anyone describe colligative properties propertly on wikipedia!! Solutes bumping into the membrane HAS NOTHING to do with osmosis. It is purely an entropic or dillution based effect. Stop teaching students the wrong thing teachers!! -signed —Preceding unsigned comment added by 146.79.245.70 (talk) 04:21, 19 July 2010 (UTC)

Many texts will agree with the explanation on this page because it is simple, but it is a result of what is going on, not the cause. This explanation is also often incorrectly used to describe freezing point depression and vapor pressure depression.

It is better described as an entropic effect, one that is not easily put into words. Essentially water will flow from regions of high concentration, to low concentration. The water is turning the heat of the environment into work (osmotic pressure), and it converts a more ordered environment into a less ordered one (when final equilibrium is achieved). Disorder increases.

Many published texts get colligative properties wrong. Don't assume that your text is accurate. This paper provides some help, albeit written with some jargon, its the best I could find without going to formal literature. http://arxiv.org/ftp/physics/papers/0305/0305011.pdf

sorry for writing here but i do not know where to post as i am new here.

any way,i want to say this:Osmosis is the diffusion of water through a semi-permeable membrane, from a solution of low solute concentration (high water potential) to a solution with high solute concentration (low water potential)

I, David Carrasco, agree with this with confidence! —Preceding unsigned comment added by 220.244.82.166 (talk) 08:10, 7 October 2009 (UTC)

This wiki entry has improved dramatically since I posted the original "complaint" above. I think it is now a very good description of what is going on - from two different angles. —Preceding unsigned comment added by 168.156.37.112 (talk) 23:55, 23 February 2010 (UTC)

Latest added picture is wrong

BTW Latest added picture is wrong, shows low concentration diffusing to higher concentration. This is wrong as solutes move down the gradient so the arrows are thus the wrong way round

i cant find the potato and salt solution information. —Preceding unsigned comment added by 58.109.18.115 (talk) 01:21, 16 November 2008 (UTC)

Solute does move to the higher concentration.Michael Fourman 19:21, 27 March 2007 (UTC) Correction solvent does move to the higher concentration; solutes do not move through the membrane! Michael Fourman (talk) 05:18, 14 December 2007 (UTC)

Erm

what are the differences between osmosis and diffusion?

Osmosis is a type of diffusion. It is the diffusion of water through the cell membrane.

Explanation

I quote:

Solutes, such as proteins or simple ions, dissolve in a solvent such as water. This raises the concentration of the solute in these areas. The solvent then diffuses to these areas of higher solute concentration to equalize the concentration of the solute throughout the solution.

To me, this does not seem like a satisfactory explanation. The solvent is not sentient and it doesn't diffuse to do anything. Why then does osmosis occur? Is this something to do with entropy in a closed system, which is meant to always decrease? (Um, I think. Can anybody answer that too?) r3m0t 16:47, Feb 20, 2005 (UTC)

A simpler explanation I found in a revision guide for my GCSE exams explained the process as such; the molecules of the solvent pass both ways through the semi-permeable membrane, however because of the higher concentration of the solvent on one side of the membrane more pressue is applied on that side and more of the solvent passes through until an equilibriam is aquired where both sides are of an equal pressure.

heyy wuts up

R3m0t: That's the same problem I've always had with the explanations I've seen of the phinominon. I just re-wrote the section to avoid the anthropomorphization. Have a look. —BenFrantzDale 07:48, Apr 23, 2005 (UTC)

Looking back at my explanation, there's one thing I don't think I can explain well. Can someone take a crack at explaining the following two misconceptions?:

Incorrect: Suppose you have your maembrane and salt water on the right and fresh on the left. The chance of a water molecule from the left side finding a hole in the membrane is clearly greater than the chance of one on the right finding a hole since the density of water molecules on the left is greater. But aren't those big salt molecules on the right going to prevent some of the fresh water from getting through? That is aren't the salt molecules going to prevent just as much flow from left to right as right to left?

Incorrect: What's the fundamental difference between having dissolved salt molecules on one side of a membrane and having neturally-buyant plastic beads? If you had plastic beads in suspension and made the beads smaller, when would you start getting osmotic pressure?

I think good answers to these would help clarify the explanation. —BenFrantzDale 00:43, 16 December 2005 (UTC)

The reason the water moves.

Firstly the water (or for that matter any solute to which the membrane is permeable) does not move by diffusion. It moves as a result of a pressure difference across the length of the pore through which it flows. This can be proven by measuring the correlation between the radius of the pore, and the rate of flow through the pore. As it happens the rate of flow is inversely proportonal to r⁴ (thats radius to the power 4) demonstrating that it is obeying Poiseuille's law of flow (as a result of pressure difference) rather than Einstien's 'drunkards walk' of diffusion.

To attempt to answer the questions posed above:

1. (do the salt ions interfere with the flow of water molecules through pores?) If you imagine the pores letting through a stream of water rather than it diffusing through passively, you can imagine how the sodium and chlorine ions would not collide with the pore exit. This effect causes a pore-exit microgradient of salt ion concentration, meaning that the concentration of salt ions at the pore exit is very low indeed.

2. (what is the difference between molecules in solution, and big beads in suspension?) Well, not much mechanically. The difference in your example is the concentration involved. The beads do not exert a significant osmotic pressure because they are at such a ow concentration. Imagine the number of salt molecules in the same volume of solution compared with the number of plastic beads that there could possibly be in the solution. Also the size of the beads is so large that they never actually get to the membrane surface which is where they would need to act because they keep getting in each others way.―87.74.29.44

If the membrane was not there at all, then simple diffusion would assure that the solute would spread from the high concentration side to the low concentration side and a complementary movement of water would occur in the opposite direction, until the concentration was uniform throughout. Entropy in the system would have increased (solute more widely dispersed = more disorder in the system overall). Entropy is where the energy for this work is being derived from. The significance of a selectively permeable membrane in the system is that (typically) the solute cannot pass through it but the water CAN. Therefore, the only way entropy can be increased in this system (and it will never match the degree of change in the no-membrane system) is for a NET movement of water into the more concentrated side. If that side is fully enclosed by the membrane, it will swell up. If the membrane is physically strong enough, internal pressure will eventually cause an equilibrium to be reached and the NET movement of water will reduce to zero. In the case of red blood cells, the membrane will break long before equilibrium is reached, so they would burst, if placed in pure water. EatYerGreens 22:48, 2 March 2007 (UTC)

I also have a problem with the explanation given in the article:

Now imagine the same membrane separates a volume of pure water from a volume of a solution. A water molecule hits the membrane, it has a certain chance of passing through, but because there are fewer water molecules per volume in the solution, the water molecules on that side will not collide with the surface as much. As a result, there will be a net flow of fresh water to the side with the solution. Assuming the membrane does not break, this net flow will slow and finally stop as the pressure on the solution side becomes such that the diffusion in each direction is equal.

This is the explanation I remember from high school, but it has come to my attention that there is a problem with it. It is not necessarily true that a solution with a higher concentration of solute has a lower concentration of solvent (in terms of molecules of solvent per unit volume), compared with the pure solvent. In some cases, adding a solute to a solvent can actually decrease the volume of the solvent [1]. In such a case, there is actually a greater concentration (molecules per unit volume) of solvent and a greater concentration of solute on the solution-side of the membrane. Using the article's explanation, one would expect a net flow of water from the solution side to the pure water side, since there are more water molecules per unit volume in the solution side of the membrane than in the pure water side. DRE 22:44, 14 February 2006 (UTC)

There is also activity (osmosis?) caused by adhesion and intermolecular force which make some materials (like cloth) attract water through membranes because of net attraction (and others), which is why water can climb up your pant leg against gravity when you step in a mud puddle. This is what many people think of when they think of osmosis. -Kristan Wifler

A problem with invoking the Second Law: The Second Law of Thermodynamics only demands that entropy never decreases in a closed system, not that it necessarily increases. Therefore, it is not a suitable explanation for why osmosis occurs.

the explanation via entropy is standard. Mct mht 05:44, 8 September 2006 (UTC)

Precision

This bursting of the cell - hemolysis in this example, since we're also talking about the lysis of blood cells? --Enigma 15:59, 24 January 2006 (UTC)

Hemolysis is only valid with anaemia, however the latter is acceptable with any bursting

All solvents or just water?

In a few books and by a few of my teachers osmosis has always been described as the movement of water and water alone, and when i've asked about this i've been told that it is only water. So is this article incorrect?

Contrary to the belief of many people, osmosis does only ever occur with water - not any other aqueous solution. Hope this helps for clarification.

I agree with you. Osmosis is ONLY water. The wiki-article needs to be changed because is says a solvent (often water). It should say "Water" and water only. When it is a solvent other than water the process is called DIFFUSION.

No wonder people cannot wrap their heads around these physical processes. —Preceding unsigned comment added by 142.177.188.142 (talk) 12:36, 16 January 2009 (UTC)

human skin/shower

Is it true that we take on water through our skin when we bathe, through osmosis? Chris 00:52, 24 May 2006 (UTC)

yes, that why your skin gets all wrinkled, because its waterlogged --voodoom 02:38, 12 July 2006 (UTC)

actually your skin gets wrinkled when you go into the ocean for too long because water diffuses from your skin... —Preceding unsigned comment added by 70.181.102.25 (talk) 02:17, 5 October 2008 (UTC)

learning via osmosis

there is the acting superstition that puting a script under your pillow at night will help you after practicing the script so you learn it, i know this is an incorrect term for use of the wordbut it is is a concept worth consideration, possibly in an alternate osmosis article --voodoom 02:40, 12 July 2006 (UTC)

Definition

Quote: Osmosis is the diffusion of a liquid (most often assumed to be water, but it can be any liquid solvent) through a partially-permeable membrane from a region of low solvent potential to a region of high solvent potential

I was always told that osmosis worked the other way round, from a high potential to a low potential (vice verca to what has been writtten in this article)

I agree with this statement, since in general you go from high to low potential. Especially for water potential there is a different definition (both at Wikipedia and "biology" by Campbell and Reece 6th edition) Actually in the book I am refering to it is clearly stated that water moves from the solution of high water potential to the one with low water potential.--84.254.17.3 16:24, 11 September 2006 (UTC)

I dislike expressions like "high potential" and "low potential" because they have little intrinsic meaning (to me: potential what, for instance?) and I go into that brain-mode which is along the lines of "I don't understand that expression, so just tell me what other people mean when they say XYZ, so I can just go along with that and get my exam marks". If someone could relate the pair of phrases to "low concentration" and "high concentration" (of solute) then I'd understand and be grateful. EatYerGreens 21:50, 2 March 2007 (UTC)

Again the misleading use of the term "solvent!" Osmosis only relates to water! I am not sure why the term solvent is being injected here repeatedly! —Preceding unsigned comment added by Hroychow (talk • contribs) 22:32, 1 March 2010 (UTC)

Aquaporens and Major Revisions

In 2003, a nobel prize was awarded to Peter Agre and Roderick MacKinnon for proving that water passes through integral channel proteins in the cell membrane called aquaporens. This article incorrectly implies that water passes through the phospholipid bilayer: being polar, this is impossible. Someone needs to revise this article to reflect modern science. The Nobel Prize Organization's PR page on their discovery: [2]

This article incorrectly implies that water passes through the phospholipid bilayer: being polar, this is impossible.

If I may paraphrase, "water being polar, this is impossible". Not quite. In studies on liposomes where the bilayer composition is carefully controlled (i.e. no protein components included) the permeability to water has been directly measured. In The Molecular Biology of Cell Membranes, by P. J. Quinn, (1982 reprint) Ch. 4.1.1 (pp 133-135), work by Bittman and Blau is described. The full article reference is :- Biochemistry, 11 (1972), 4831-9, if that helps. Granted, water transport through pores is undoubtedly 1000 times more efficient than directly through the bilayer. Apparently the sheer fluidity of the lipid molecules is what makes it less than impassable. EatYerGreens 21:38, 2 March 2007 (UTC)

I agree!

Aquaporin -- note the spelling. —Preceding unsigned comment added by Hroychow (talk • contribs) 22:29, 1 March 2010 (UTC)

HEHE! :) —Preceding unsigned comment added by 121.73.250.144 (talk) 08:00, 9 June 2010 (UTC)

Endosmosis

I have redirected Endosmosis here, as the term appeared to mean almost exactly the same thing as Osmosis. If the meaning is somewhat different, a sentence or two about it could be included in this article, if someone wants to write them. --Xyzzyplugh 12:35, 30 September 2006 (UTC)

Correction - Solvent vs. solute

Solvent = the greater solution of 2 Solute = the solution there is less of

For example, as in water and salt - WATER is the solvent, SALT is the solute.

So, Osmosis is NOT: "the movement of water through a selectively permeable membrane from a region of low solute potential to a region of high solute potential"

but is rather 1) "the movement of water through a selectively permeable membrane from a region of low SOLUTE potential to a region of high SOLUTE potential"

or 2) "the movement of water through a selectively permeable membrane from a region of high solvent potential to a region of low solvent potential" - since the solvent in the case of osmosis is water.

(Bad formulation to use "solvent" at all though).

Another suggestion would be to write: "the movement of water through a selectively permeable membrane from a region of high water potential to a region of low water potential"

- Teh_biologisterer

Errrm, you typed the "Osmosis is NOT..." sentence and the "but is rather..." sentence exactly the same (in meaning), apart from "SOLUTE", in capital letters, in the second one. Care to try that again? EatYerGreens 22:00, 2 March 2007 (UTC)

Yep that was a schoolboy error there!

Semi-protection

I have protected this article from editing from anonymous and newly-registered users temporarily, considering the flood of vandalism it has received just now. - Mark 14:53, 28 November 2006 (UTC)

Why were so many people vandalising it at once? They achieved nothing. Rintrah 01:52, 29 November 2006 (UTC)

No idea. Just random idiots. - Mark 10:16, 29 November 2006 (UTC)

Bunch of kids in my class were copying and pasting for science coursework, so others vandalised it to stop them and have fun simultaneously. Rintrah, I think you'll find that we did accomplish something, the page is semi protected now isn't it? OrangeCrusader2

Accomplish something. Nah. It took me all of 10 seconds to request a couple admins come and protect the page / block the vandals. You clearly have no idea of how well Wikipedia works in the background to prevent vandalism like this. If you would care to inform your classmates, a repeat will see someone from Abuse Report contact your school. Yeap, we can and do that too over at WP:AbRep. Kind Regards - Heligoland | Talk | Contribs 19:13, 29 November 2006 (UTC)

Well, if you look through the history file, there were a number of other editors who were reverting the article as fast as the vandalism occurred. I suppose that requiring the cleanup efforts of serious folks is the new definition of "fun" to today's young folks. "Just the fact that you CAN does not mean that you SHOULD!" Lmcelhiney 19:21, 29 November 2006 (UTC)

"You clearly have no idea of how well Wikipedia works in the background to prevent vandalism like this." Oh I do, it was funny to watch while it lasted though. "a repeat will see someone from Abuse Report contact your school" I don't think they really care remotely. "Just the fact that you CAN does not mean that you SHOULD!" But they WILL.OrangeCrusader2

pure fool through and through Chensiyuan 13:51, 30 November 2006 (UTC)

I quote:

'Osmosis is the net movement of water through a selective permeable membrane from a region of low solute potential to a region of high solute potential (or equivalently, from a region of high solvent potential to a region of low solvent potential).' Instead of it being "thorugh a slective permeable membrane", which doesn't make sense, it should be "through a selctively permeable membrane".

Also, it can't be potential if it already is. If osmosis is happening than the high concentration is the high concentration and the low concentration is the low one. It is not potential.Ce.moreon 23:51, 12 December 2006 (UTC)

Unprotection

I have removed the semi-protection from this article, after a couple of weeks. - Mark 14:09, 13 December 2006 (UTC)

O,O .

The page is protected, so I can't fix it, but if we want to be precise, osmosis is diffusion of water ONLY. Diffusion of any other solute is just diffusion. (This is in reference to the "usually water" bit in the definition.) Hwi- Sept 2008

That's why it is protected ;-) Honestly, diffusion of solutes occurs in dialysis (take a look at Atkins, Physical Chemistry), which is based on osmosis, diffusion of Ions leads to the Donnan effect which is an osmotic phenomenon, just take a look at Moore, PC - Physical Chemistry. If you are able to read German, you might want to take a look at the classic work about osmosis by Wilhelm Pfeffer Osmotische Untersuchen, who explicitly refers to the "Diosmose gelöster Körper" (osmosis of solved substances). BTW: Osmosis is in no way restrained to water as permeable solvent, osmosis can happen with other solvents and even gaseous substances.

This type of confusion happens because many textbooks, especially biology books, take a water based system to introduce the concept of osmosis but fail to supply a more general definition afterwards. Regards, --Drahkrub (talk) 18:06, 17 September 2008 (UTC)

agreed:) —Preceding unsigned comment added by 202.156.9.231 (talk) 17:32, 11 May 2009 (UTC)

But what is Osmosis?

There should be a simple explanation for people are not technical and don't wish to be, like "Osmosis turns water into oxygen" or whatever IceHunter (who will sign his posts when Wikipedia stops using an american jingoistic character (which is easily accessible on american keyboards but difficult to get for the rest of the world))

Ice Hunter, just click on the symbols after Sign your user name below the edit window - you don't need to find the tilde character on you keyboard. Michael Fourman 23:20, 25 March 2007 (UTC)

But Why?

When a solute is added to water, why is it that the water molecules are attracted to the solute molecules... is it because of the inter/intra(i forget which)molecular forces between the ions and the polar ends of water, or am i getting this totally wrong? Behind the veil 13:27, 25 March 2007 (UTC)

Osmosis is nothing to do with any attractions between molecules of solvent and solute. Simply the fact that the membrane is impermeable to solute molecules, but permeable to solvent, is enough. See basic explanation section. I've just tried to maske this clearer; I hope it makes sense. Michael Fourman 23:15, 25 March 2007 (UTC)

I would go so far as to say that there is no such thing as osmosis. All that happens is that water diffuses from a region of high concentration to a region of low concentration. There is no separate physical process called "osmosis" there is only diffusion. Suggesting that "Osmosis" exists just confuses things. Stuart Wilson, 27th November 2007.

Cleaning needed?

Stumbled on the article, and this is what I get :

"Osmosis is a retarted subject you study in biology, usually involving a lab with potato cells and some sort of piontless lab report where you constantly repeat yourself and don't learn anything more about osmosis than you did in fourth grade when you first studied it."

Perhaps it needs some cleaning. :P I'll leave that to you guys, I am really not qualified.

Cheers. —Preceding unsigned comment added by 86.206.49.175 (talk) 05:40, 16 October 2007 (UTC)

Merger proposal

Merge with Osmotic shock? This has been proposed, but I'm not 100% convinced this is a good idea. The area of how organisms respond to osmotic stress is quite a broad one, and this stub could be greatly expanded to cover vertebrates/microorganisms/plants etc, and the particular organs or molecules involved in each organism, as well as the sensors and the signaling pathways that trigger the responses. I'm not proposing to do this immediatley, but this stub could grow quite large if an expert in the field was interested. Anyway, what do other people think? Tim Vickers (talk) 17:11, 11 December 2007 (UTC)

Agree; don't merge. Osmosis is a general physical process. Osmotic shock needs to refer to osmosis but is a separate issue. Michael Fourman (talk) 05:26, 14 December 2007 (UTC) Full Ack - don't merge Osmotic shock and Osmotic stress as biological/medical issues do definitly not belong into a physical/chemical article like osmosis. --Drahkrub (talk) 08:13, 12 April 2008 (UTC)

Concern moved from main article

86.144.43.43 has the following concern: what it says at the top! it is actually the opposite! osmosis happenes to water molecules moving from a HIGH CONCENTRATION, to a LOW CONCENTRATION! what they are thinking of is ACTIVE TRANSPORT! which is like completely different! An easier way of explaining it... Osmosis is like diffusion! only with water particles and with semipermeable membrane allowing certain molecules to actually get to the lower concentration solution! -- Paleorthid (talk) 22:49, 13 January 2008 (UTC)

Response. The article is correct, the concern is misplaced. The high concentration referred to is that of the solute, not of the water, which is the solvent. When a membrane is permeable to the solvent but not the solute, osmosis occurs. When the membrane is permeable to both, diffusion across the membrane occurs. Active transport is active (requiring an input of energy). Osmosis, like diffusion, is passive transport. -- Paleorthid (talk) 22:49, 13 January 2008 (UTC)-- Paleorthid (talk) 22:49, 13 January 2008 (UTC)

What's in a name?

IMHO: my daughter is doing GCSE and she and her friends are getting confused about osmosis. I think this has something to do with the terminology. When I was a student I thought the same. Why not use words that are more distinct than 'solute' and 'solvent'? Us grizzled science types are OK with this but newcomers and those who do not have classical english as a first language may have problems.

Just my six pennyworth and I know no one is going to change the names but it is something we should be aware of. It is hard enough to get kids to do the work in today's emasculated GCSE science let alone hope they may become sufficiently intrigued to choose science as a career (like I did). Royzee (talk) 19:16, 20 January 2008 (UTC)

Essential Factual Errors

I hate having to say this - but this article errs in quite a number of essential factual statements:

• Osmosis is not confined to water as solvent, it may include other fluids and even gases, although some biology textbooks will define osmosis incorrectly like the article does.
• Osmosis may include the movement of solutes (as in Dialysis (biochemistry)).
• It is not concentration what counts but rather the number of particles.
• Explanation of Osmotic pressure explains colligative property in terms of concentration, not number of particels, see article Van 't Hoff factor.

-- 22:03, 16 February 2008 (UTC) Buk

"Osmotic pressure" section

I guess there are some mistake with numeration of equations (eq. 1 isn't written at all, and no references to eq. 2 and 3, so no need in numeration)--VGmonster (talk) 14:31, 17 April 2008 (UTC)

Osmosis and pH

id like to say its gay —Preceding unsigned comment added by 86.155.0.60 (talk) 20:25, 10 November 2008 (UTC)

I'd say this article needs more information about pH and how it affects Osmosis Gsp (talk) 11:35, 6 October 2008 (UTC)

Edit Request

{{editsemiprotected}} Please change the first line to read: Osmosis is the tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane. Thanks. —Preceding unsigned comment added by 18.238.6.10 (talk • contribs)

 Not done Please provide link(s) to reliable, verifiable source(s) and reinstate your request, thanks.  Chzz  ►  07:52, 9 October 2009 (UTC)

See http://www.merriam-webster.com/dictionary/osmosis. Essentially, the above suggestion (not mine), or something like it, is a good idea (though the wording seems a bit wonky; e.g. "solvent" should be "solute"?). The current lead paragraph has three bites at the cherry where only one is needed:

"Osmosis is the diffusion ... More specifically, it is ... It is a physical process in which ..."

81.129.128.164 (talk) 21:46, 1 January 2010 (UTC).

Nay, it's rather a bad idea. Osmosis does not tend to equalize concentrations but rather chemical potential. Just try to figure out how a system of pure liquid or gas and a solution could reach a state of equal concentration on both sides of the membrane if the movement can only be transfer of solvent into the solution compartment? The only way to reach such a state would require complete removal of all substance from the pure solvent compartment - which has never been observed. Forget the Merriam-Webster definition - it's just rubbish and we should better stick with scientific sources. That's a problem partucilar to definitions of osmosis found in the literature - many of them are incomplete, too restricted or some are even factual nonsense.

BTW: The movement of solvent through the membrane is by its nature not diffusion (quite a common misconception based on the suggestion from Adolf Fick, see Adolf Fick. On liquid diffusion Philos. Mag., 10:30, 1855) but rather convection, as shown by A. Mauro., See his paper Nature of solvent transfer in osmosis. Science, 126:252, 1957 and the discussion of his work in later reviews, e.g. Frank G. Borg. What is Osmosis arXiv.org, e-Print (2003), p 14. Regards, --Burkhard (talk) 23:14, 2 January 2010 (UTC)

I don't think they're suggesting that equalisation of concentrations is actually achieved: they use the word "tend". In any case, the existing wording -- "tends to reduce the difference in concentrations" -- can be substituted. My main point is that the lead currently seems to keep "restarting", as if it keeps thinking of new things, or as if several different people have had a go. I think that all the fundamental points can be got across in one sentence. For example:

Osmosis is the movement of a solvent (such as water) across a semi-permeable membrane from a less-concentrated (hypotonic) to more-concentrated (hypertonic) solution, tending to reduce the difference in concentrations.

Compare this to what we currently have. Even if my effort is not exactly technically correct, do you see what I'm getting at? 86.133.54.74 (talk) 03:10, 3 January 2010 (UTC).

I repeat: The driving force behind osmotic processes are differences in chemical potential, not concentration. What tends to get equalized is the free enthalpy but not concentration. Trying to define or explain osmosis by means of concentration differences is plain wrong, misleading and contraproductive - therefore it is completely irrelevant what the guys from MW might have meant, it will remain rubbish, no matter how you try to interpret their intentions.

I agree that what we have now is too restricted (water only) and that in the end it relates to concentration as well, but it does not make sense to replace one wrong definition with another from a general dictionary - we should get it really right. One problem with osmosis is that that there are literally hundreds if not thousands of definitions out in the wild, most of them put up with little thought or knowlegde and hundreds of textbooks simply repeating or rephrasing other definitions, as this article itself does. The next problem is that most PC textbooks introduce osmosis using an example where a pure solvent and a solution are seperated by a semipermable membrane and then stop there. Students tend to believe that osmosis is restricted to systems comprising of these three ingredients and take this introcuctory example as real and authorative definition. Ever read about thermoosmosis where the osmotic movement involves just one component, rendering terms like solution and solvent meaningless in such context?

A new introduction should get it right from the start. As there is not just one authorative definiton it needs to be generic enough to harbor different scientific opinions on what is included into osmosis. E.g. according to Atkins'/de Paula's Physical Chemistry dialysis is a phenomenon based on osmosis whereas authors like Sun-Tak Hwang, Karl Kammermeyer: Membranes in separation, p. 24, (Techniques of chemistry, v. VII). John Wiley & Sons, Rochester, NY. 1975. ISBN 0-471-93268-X insist on differentiating between dialysis and osmosis. I don't see how this multitude can be put into one introductory sentence. Regards, --Burkhard (talk) 18:24, 3 January 2010 (UTC)

In that case, I think the lead should give as brief a definition as possible that is absolutely technically correct in the greatest generality, and then straight away cut to explaining the commonest example, which is the water-passing-through-membrane-so-as-to-reduce-differences-in-concentration one. 81.157.197.199 (talk) 15:14, 4 January 2010 (UTC).

Apparent contradiction

The lead section says that osmosis in biological systems generally involves membranes that are "impermeable to ... large molecules ... while permeable to water and small, uncharged solutes", and yet "Basic explanation" says that "particle size has no bearing on osmotic pressure". Does this make sense? 81.129.128.164 (talk) 21:12, 1 January 2010 (UTC).

Explanation of graphic

The graphic Osmosis.JPG looks like it could be a useful aid to understanding, but I would like to see an explanation of what it depicts in the caption. The explanation at File:Osmosis.JPG is poor. It talks a lot of complicated science but does not make any actual connection to the observed effects of osmosis. 81.129.128.164 (talk) 21:37, 1 January 2010 (UTC).

This sentence...

This is the same explanation as to why the disordered air does not spontaneously separate and order into oxygen and nitrogen, it would take energy for this to happen.

I'm no expert, but this sounds like bollocks to me. The reason why oxygen and nitrogen mix freely in the air is simply because both are randomly distributed throughout space - it would indeed take energy to keep them separate, but this has no relation to osmosis. 86.177.236.90 (talk) 21:16, 9 January 2010 (UTC) Osmosis is the diffusion of water across partially permeable membrane. The terms "semipermeable" or "selectively permeable" are more in use when it comes to biology. —Preceding unsigned comment added by 82.45.119.207 (talk) 20:43, 13 January 2010 (UTC)

Error in ref. 3

Hello there - can anyone correct the link that is related to ref. 3. It doesn't work! I think it should link to http://www.statkraft.com/presscentre/news/the-worlds-first-osmotic-power-plant-opened.aspx instead. Thanks \MrDenberg —Preceding unsigned comment added by MrDenberg (talk • contribs) 14:15, 11 January 2010 (UTC)

 —Preceding unsigned comment added by 97.127.31.189 (talk) 23:28, 16 February 2010 (UTC) 

Hmm...wondering...

should there be a reference on here to human osmosis in fiction? I've heard people say stuff like "Do your homework; you can't just touch the book and absorb the knowledge by osmosis!"; is human osmosis present anywhere in fiction? RandyS0725 (talk) 20:47, 27 March 2010 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Osmosis/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

rated top as high school/SAT biology content - tameeria 14:58, 17 February 2007 (UTC) This article could use some cleanup/copyediting, references and a section on (or at least mention of) osmotic shock. The two example pictures don't work in my browser. - tameeria 19:25, 18 February 2007 (UTC)

Last edited at 13:30, 7 November 2008 (UTC). Substituted at 15:30, 1 May 2016 (UTC)