h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

In order to describe this phenomenon, the concepts of free energy and entropy, and distance from equilibrium would be useful. This is a can of worms.

I have not figured out what the following sentence means:

The osmotic flow stops when the concentrations are balanced or when the hydrostatic pressure acting against this flow becomes as high.

What is osmotic flow and what is hydrostatic pressure?

What is a dynamic equilibrium?

Maybe we should define semi permeable membrane without throwing in a cation, since anions, too, which are excluded by the membrane contribute to the osmotic potential.

Note 6 is not relevant.

Solvent tends to flow from higher potential to low potential. Pure water is assigned zero potential. Any solute, by crackey, results in a negative potential. This is not weird.

Describing the osmotic potential as sucking is unorthodox. We have all been taught high to low by convention, without higher "potential" there is no reason to move.

There, I have come up with all sorts of impediments, without really suggesting ways to "fix" the article . I'm not trying to hurt your feelings.

Your willingness to tackle chemical physics, or is it physical chemistry, is admirable. Maybe try to avoid the DNA tounge in cheek parts. This is serious.

Have you ever noticed that you don't prune up when you swim in the ocean? That might be a good bit.

Again, take my suggestions and comments with a grain of salt. Thank you. MD

Okay, sorry for the delay. Lots of RL stuff to do.

First: Why didn't you put your comments into the PR discussion? Would have been of more help there. As far as THIS entry is concerned I can't do changes. (I'll comment on them, though, below).

Before I start: What do you mean by: 'Maybe try to avoid the DNA tounge in cheek parts. This is serious.'

I am not familiar with too many english idioms. Cheeks in DNA? Well. Now to the comments:

1. I am not going to open the can of worms. This entry is aimed at laypeople, so for that reason a more descriptive description of Osmosis as attempted here is probably better.

2. Osmotic flow is the flow of solvent through the membrane before equilibrium is reached. Hydrostatic pressure is the common pressure a volume of liquid exerts at a certain area.

3. Dynamic equilibrium is the following: If you look at every atom of the soup, they are moving around, that is: they are not static. Solvent molecules from both sides of the membrane flow in and out of the recipients. Even though they are moving around there is equilibrium (with a negligible fluctuation): That is dynamic equilibrium.

4. The mention of the cation was just meant as an example for a general ion. Of course anions do it too. Anything dissolved will do. Like sugar for instance which is not a ion in astrict sense.

5. Note 6 is irrelevant. So what? I thought it's the interesting kind of triffle knowledge worth putting in. Apart from that I included the note because from the text one might feel that the rigidity of a plant is only due to osmosis, and forget that there are other things making a tree stable.

6. For you it might not seem weird. But common people tend to look at a high number in modulo (eg. -174) and say the number is higher than a low number in modulo (eg. -81). Of course, that's wrong (-174 is lower than -81). The weird thing about that and the osmotic potential is that it is based on definition, and it could have been made easier (i.e. without the sign) for common people to grasp just by assuming a different model.

7. Describing Osmosis as sucking IS indeed unorthodox. But, pardon me, so what? H2G2 is unorthodox.

8. Pruning up in the ocean IS a good bit. Maybe you would want to write an entry about the effects of osmosis on our everyday lives? I am afraid that it's too late for an inclusion of that into the entry.

Thanks for the comments anyways Mediocredane. I do not agree that the entry needs to be 'fixed'. If someone wants to have a ultimate all correct explanation of osmosis, I think it's not h2g2 where he/she's going to look for it. I think you must be quite new here. One of the first things one learns in h2g2 is to take things less serious. This entry is OK just the way it is IMHO. Your comments would have been much more helpful in the PR process. Maybe I could have formulated things in a better way.

Anyways,

HELL

PS: Don't excpect any further replies until tuesday next week.

You wrote: "If someone wants to have a ultimate all correct explanation of osmosis, I think it's not h2g2 where he/she's going to look for it. I think you must be quite new here. One of the first things one learns in h2g2 is to take things less serious."

Excuse me! This and some of the earlier comments in your rebuttal (eg "Describing Osmosis as sucking IS indeed unorthodox. But, pardon me, so what? H2G2 is unorthodox") look like you are trying to "talk down" to readers and researchers of h2g2. I am one of the laypeople you say the entry is aimed at. I am also quite new here. I don't know anything about osmosis, so what I read here I expect to be correct. I'm not saying that what you wrote is or isn't correct, I am not qualified to judge that, but I would definitely like to think that if I am looking for good information on a subject, particularly a scientific term which should be capable of definition and explanation, then h2g2 is a resource worth consulting. Otherwise what's the point?

You begin the entry by stating "Most of us bump into this weird term when reading biology textbooks". Well, people who read biology textbooks are not laypeople (you say you aim this entry at laypeople), but biology students. I have to tell you that I have never studied biology or read a biology textbook in my life but I have certainly come across osmosis. It does have a figurative signification as well, you know. I would suggest that biology students are a minority.

You give a perfectly straightforward, if inaccurate, account of the origin of 'osmosis'. I say 'inaccurate', because it does not mean 'to collide' or 'to hit' - it comes from the Greek word 'osmos', which means 'push' or 'thrust'. Well never mind that, I don't suppose it matters too much now - but why do you say it is a weird term? What's weird about it?

For an entry that's aimed at laypeople, I confess you lost me in your first paragraph, where I ran up against 'solute' and 'hydrostatic pressure' and 'cations'. But I wouldn't mind betting you lost laypeople more intelligent than I when you started getting into Nobel Prize-winning equations. As a layperson I thought 'molar concentration' might have something to do with dentistry.

For all I know this might be a brilliant article but - IMO - it's not for laypeople!

Hmm, maybe you are right in some parts.

First of all... To my knowledge the entry IS accurate, what I wrote in reply to the first post of this thread was meant in a different way:

I don't want to start explaining chemical potentials, enthalpy and entropy and get to osmosis from there. That would be too complicated although ultimately all-correct. If you were looking for THAT h2g2 is probably not the place to go. Apart from that, the description for osmosis found in this entry IS correct.

About taking h2g2 less serous... There's a wealth of entries on scientific topics that I would - from a scientific point of view - (I am a scientist) dispute. But, looking at it from a h2g2 perspective the entries are meant to be accurate, but not to the last pedantic bit. Maybe I formulated that wrong in the reply above.

"I am one of the laypeople you say the entry is aimed at. I am also quite new here. I don't know anything about osmosis, so what I read here I expect to be correct."

Relax. The entry IS correct, but not as ultimately correct as the first post in this thread requires.

"I would definitely like to think that if I am looking for good information on a subject, particularly a scientific term which should be capable of definition and explanation, then h2g2 is a resource worth consulting. Otherwise what's the point?"

You're right. But h2g2 is not all-accurate ultimate truth - bear that in mind. The scientific stuff I write is to the best of my knowledge correct, you can use it without fear in your homework, essays, presentations, etc. But it's not going into the last detail of the topic.

OK... Summing up: Maybe I should have formulated my reply in a different way. Stuff in h2g2 is correct but sometimes a little incomplete. I think that's better.

"People who read biology textbooks are not laypeople (you say you aim this entry at laypeople), but biology students. I have to tell you that I have never studied biology or read a biology textbook in my life but I have certainly come across osmosis."

I meant SCHOOL-biology-textbooks. I thought that that's where most of us bump into osmosis. At least for me it was in school.

"It does have a figurative signification as well, you know."

What? Osmosis has a figurative meaning? Really? Please, tell me more... I am not a native English speaker, so, specially when it comes down to figurative meanings and idioms I don't know anything.

"...it comes from the Greek word 'osmos', which means 'push' or 'thrust'. ... why do you say it is a weird term? What's weird about it?"

1 - In my physics textbook (in german) 'osmos' is translated as 'colliding, pushing' - that's where I got it from.
2 - Weird: Why isn't it called 'pushing pressure' but 'osmosis'. To me, the word 'osmosis SOUNDS weird, and could be perfectly replaced by a term that anyone understands.
PS: It always dumbstrikes me when I notice somewhere that the terms I bump into actually have a very real everyday-life MEANING. Before I cared to look for the translation of 'osmos' I thought osmosis is a long forgotten word meaning 'that weird thing that happens when you strap a pig's skin to a flask containing putrid fruit' - which was probably the first time someone SAW osmosis happening. But no. At that time the person would have called it 'piggy blop' ore something, and only centuries afterwards, when scientists started to mess around with membranes and solutions they came up with that greek word. I think this is WEIRD.

"For an entry that's aimed at laypeople, I confess you lost me in your first paragraph where I ran up against 'solute' and 'hydrostatic pressure' and 'cations'. But I wouldn't mind betting you lost laypeople more intelligent than I when you started getting into Nobel Prize-winning equations. As a layperson I thought 'molar concentration' might have something to do with dentistry."

I am terribly sorry. That's the kind of information that I would have needed in the Peer Review process. You see, I am a scientist, and for me it is difficult to get back to the level of a layperson to explain stuff. So, if you have trouble with equations and words I couldn't know that. I thought it was somehow clear for anyone what 'hydrostatic pressure' or 'solute' is. Had I known that these terms are not widely used, maybe I would have written it differently. That's why this kind of comment is so useful in the peer review.

As far as 'molar' concentration is concerned: That's a perfect example for how things can get messed up. If I write the entry just saying 'concentration' then some pedantic wise-guy pops up and says 'Wo, but you have to use the MOLAR concentration'... For the pedantic's sake I end up including the word 'molar' in the hope that the layperson skpis over it and thinks 'OK, so it's a special form of measuring a concentration, but I don't have to bother about that' You see, here you end up trying to please greeks and trojans.

Thanks for your comment anyways - I will think of that for my next entries.

HELL

Dear Hell

Thanks very much for that explanation. I think the problem you describe is common to many Researchers here - how to explain a topic accurately without going into all the fine detail that an expert in the topic would expect. That was certainly one of the major problems I faced in writing the couple of entries which I have done so far. I think you need to use phrases like :
'It is generally agreed that...'
'A simple explanation would be...'
'Without going too deeply into it, you could say that...'
I notice that you actually tried to do this. But perhaps the topic of osmosis is so complicated that it would be better to write about something simpler, or take just one aspect of it (if that's possible - I wouldn't know) and confine yourself to that. But whatever you do, don't just include something in the hope that some readers will skip over it!

I also had the problem of how to get people to comment in Peer Review. What I did was to look around for other Researchers I thought might be interested in my topic, and sent them a note saying 'I've just put this entry into PR and would you like to take a look and comment please?' You could perhaps search for other scientific or biology-related entries, see who had written them, visit their Space, and take it from there. I know it's time-consuming. Maybe someone else can come up with a better idea?

The figurative meaning of osmosis, which non-scientific English-speaking people would understand, is the process of gradual, possibly unconscious, assimilation of ideas, knowledge, ambience or ethos. It's the process of getting to understand just by hanging around for a while and letting things sink in without necessarily making any conscious effort to learn. You can learn a lot about h2g2 by osmosis. It's to do with sniffing the air, feeling the vibes, that sort of thing.

English is my mother tongue, but I still need a good English-English Dictionary as a minimum, not to mention a thesaurus, and other books of reference on English usage. For h2g2 you should ideally use a British dictionary rather than one from any other anglophone country. A very useful single-volume dictionary which is not too massive on the bookshelf is The New Oxford Dictionary of English (Clarendon Press, Oxford). If you are serious about writing in English you ought to get one. Depending on where you are, it might be quite easy to pick up a good one second-hand.

If you are doing another scientific entry for lay people do let me know when it goes into PR and I'll be happy to give you a layman's opinion!

Yes, yes, There is one (cf. bottom of this reply).

I already have loads of dictionaries, and I don't think my English is that bad, thanks for the advice though. The problems are the idioms and the extended useage of words like 'osmosis'.

On thing I noted in that explanation is: That what is being described would be more correctly termed 'learning by diffusion' instead of 'osmosis' since you don't have a semi-permeable membrane there... Bah... Anyways. I got the picture. Thanks.

"But whatever you do, don't just include something in the hope that some readers will skip over it!"

Okay, in the future I pay more attention to that. Thanks.

"I also had the problem of how to get people to comment in Peer Review."

I recommend that everyone should hang out a while at the PR and comment on stuff, even if it's not their speciality. I regularly scan over the entries and comment where I think my comments will be of help. Sometimes - when I really like the entry - I just pop in and say the entry is great. Everyone should do this once in a while, then you wouldn't need to recruit people by yourself. I think that's how it SHOULD work.

As mentioned before: There is one entry I subbed for PR, recently. It's not really about science, but about the historical evolution of the science behind 'acids and bases'. Go there and tell me what you think.

HELL

Your English is very good. So is mine, but I still use a dictionary. The dictionary I mentioned will give you information on idioms, and extended usages of words like 'osmosis', also accurate information on etymology, guidance on usage, and so on.

Your English is very good. So is mine, but I still use a dictionary. The dictionary I mentioned will give you information on idioms, and extended usages of words like 'osmosis', also accurate information on etymology, guidance on usage, and so on.

Actually, as someone who runs a reverse osmosis plant, I found the article very accurate as far as one can go in this sort of forum. It works, who cares how? If it will turn sea water into drinking water then I'm happy.
Rod

Yo Rocket...

Maybe you know the answer to this:

If I have a tube with a semi permeable membrane attached to one end and I stick it into the sea then at a certain depth fresh water will get into my tube (reverse osmosis - that's I think how reverse osmosis gadgets work) the depth is so that the hydrostatic pressure is equal or bigger than the osmotic pressure. As I keep pressing the tube down the fresh water in the inner part of the tube will rise until it's hydrostatic pressure reaches the osmotic pressure - still following? - Now the problem: The density of fresh water is lower than the density of sea water. For that reason the water height inside my tube will rise more than I push it deeper to achieve higher pressures. I can calculate that at a depth of some kilometres the fresh water height will even exceed sea level. Now with that I could generate power and gain sea water. Of course that's not possible - because otherwise people would already have done it. But I don't know the reason. Do you happen to know it? Or are you rushing to the next tube and membrane store?

Thanks

HELL

I mean gain fresh water... was typing too fast.

See you,

HELL

As far as I can figure, the only problem is the input of work, ie: (in this case pressure).
The reverse osmosis plant that I work with relies on positive pressure on the raw water side of the semipermeable membrane, for every 10 litres of town water this plant will produce one litre of demineralised water. With seawater it is more like one hundred litres for one litre demineralised water. Oh it also works at a pressure of 210bar,in short you've got to pump(hard)

Rod

Hmm... Work, eh? I'll take a look at that. Thanks.

HELL.