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This article says R = 8.314 but in all the osmotic pressure calculations I have done at uni we have used 0.08206 L atm mol K. Does anyone object to changing this? -- Mdhowe 04:34, 18 October 2006 (UTC)
I have no objection, that is the most commonly used value of R for osmotic pressure and it also uses the simplest dimensions. —Preceding unsigned comment added by 69.105.29.230 ( talk) 06:50, 14 April 2010 (UTC)
I know this phenomenon as Osmotic pressure. I thought everybody did?
Turgid and flacid plant parts
I am going to add a short description of turgid and flacid plant parts with a link to the article stoma. It seems like a good idea to me. Thoughts? 160.94.120.197 17:11, 19 October 2005 (UTC)lotusduck
What about turgour and erectile body parts. Does this not deseve a mention?-- Light current 00:44, 11 January 2006 (UTC)
I understand osmotic pressure as follows:
Solution in semipermeable membrane (permeable only to solvent) exposed to pure solvent. The osmotic pressure is the physical pressure applied to the solution required to prevent movement of pure solvent into the solution.
Another, less accurate, way to define it is the pressure a solution exerts through a semipermeable membrane to draw more solvent into itself.
I have never heard of "turgor pressure" and many erectile tissues in animals rely on blood flow rather than osmosis.
The definition of osmotic pressure given above ("...the physical pressure applied to the solution required to prevent movement of pure solvent into the solution") is a much better definition that the one actually given in the article ("...the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute"). In fact, the hydrostatic pressure is not "produced" by a solution, but rather must be applied by some outside entity, such as the rigid walls of a container resisting volume changes, or the force of gravity acting on a column of solution. I'll make the change unless anyone has any objections. Thewookie55 19:14, 24 September 2007 (UTC)
Tugor and osmotic pressure are different things. Osmotic pressure is the pressure applied from the outside of the cell that pushes the water in. We could say it is the tendancy to take water. ( http://edtech.clas.pdx.edu/osmosis_tutorial/osmotic_pressure3.html) and ( http://www.wisc-online.com/objects/index_tj.asp?objid=NUR4004) Turgor pressure is from inside of the cell done by the water inside. ( http://www.cartage.org.lb/en/themes/Reference/dictionary/Botanical/T/Turgor.html) Klesk
tur·gor (tûr'gər, -gôr')
n.
- The state of being turgid.
- Biology. The normal fullness or tension produced by the fluid content of blood vessels, capillaries, and plant or animal cells.
I have separated out the osmosis and turgor pressure information as osmotic pressure is the cause of turgor pressure, but they are not the same thing. Please feel free to add to either article. pschemp | talk 03:22, 9 July 2006 (UTC)
I think the symbol's wrong here: π = iMRT.
(I don't know how to change it, so I thought I'd just comment —The preceding unsigned comment was added by 90.240.242.118 ( talk) 14:18, 3 March 2007 (UTC).
The correct symbol is π according to Physiology (Berne and Levy, 5th Ed) and Physiology (Costanzo, 3rd Ed). You might be thinking of Φ (Phi) which is the Osmotic co-efficient, and can be added to the equation in the form π = iMRTΦ. However, Osmotic pressure and Osmotic coefficient are not the same thing. Tim Set Match ( talk) 15:25, 5 January 2008 (UTC)
I agree with the first post, it should be Psi, due to the fact Psi is a symbol, in this example symbolising the Osmotic potential. Pi is a constant which I believe isn't correct. e.g. ψ =iMRT. 12:47, 19 September 2008 —Preceding unsigned comment added by 81.110.103.44 ( talk)
Osmotic pressure seems to be important in medicine, there's a lot of talk about it in topics like traumatic brain injury.I'm not knowledgeable enough to write about it yet,but if I do the research would osmotic pressure as a medical topic be better as a separate article? Thanks 216.40.21.8 13:05, 29 July 2007 (UTC)
A solute doesn't 'want' to do anything. —Preceding unsigned comment added by 124.188.96.108 ( talk) 14:34, 15 September 2008 (UTC)
How does one calculate the amount of energy needed to remove a given volume of solvent from a solution? Notice that the concentration of the solution changes as the volume does, and that pressure*volume[=]energy. Thoughts? RSido ( talk) 01:49, 13 May 2009 (UTC)
Does somebody have a derivation of the Morse equation from first principles? 124.168.200.74 ( talk) 14:10, 14 May 2009 (UTC)
Blood, vinegar, Alkaline detergent or lemon juice.Bold text —Preceding unsigned comment added by 24.4.135.218 ( talk) 20:13, 22 March 2010 (UTC)
I came to this article to confirm that the units of osmotic pressure is Osm or mOsm. This was not included on this page, but Googling, I found many instances where it is used. Perhaps this would be of use to other readers. Wakablogger2 ( talk) 21:22, 12 August 2010 (UTC)
On 04:10, 10 January 2013 user:174.57.197.136 changed the value of R from (8.3145 J K-1 mol-1) to (08205746 L atm K-1 mol-1). These are different forms of the same unit, and are both correct. However, in this context, I believe (it's been too long since second semester physics, sorry), that a pressure-based form (as opposed to the Joules form previously in the article) is appropriate, as the usual unit for osmotic pressure is, in fact pressure, and usually Pascals. But as the usual unit is Pascals, I'd think the kPa form (8.3145 L kPa K−1 mol−1) form of R would be preferred, not the atm form as it reads now. Note that the numerical value of the kPa form is the same as the Joules form.
I see this has been slightly discussed here before (not to mention the multiple decades since I've had to work one of these) so before changing it to (8.3145 L kPa K−1 mol−1), I thought I'd ask. Rwessel ( talk) 07:30, 10 January 2013 (UTC)
Dear Osmosis Experts: A friend who knows more physics than I do, but who is not a Wiki editor, pointed out what is to him a mis-wording in "This process will stop once the pressures of the water and sugar water on both sides of the membrane become equal." His suggested replacement: "The process stops when the partial pressure of water on the sugar-water side equals the pressure of the pure water on the other side." His point, I think, is that it is not equality of total pressure between the two liquids, but rather equality of water to water, disregarding the additional pressure due to the sugar. I am reluctant to edit the change myself, because I am not an osmoticist. Would one of you experts please make this change if you see it as valid? Two additional notes: (1) In the sentence before that one, how about replacing "the two solutions" with "the two liquids," (including the comma), as pure water is technically not a "solution", right? (2) My friend introduces the phrase "partial pressure"; Wikipedia has an article on it, but it seems to deal only with gases. Would a link to partial pressure be appropriate? Kotabatubara ( talk) 19:01, 10 November 2015 (UTC)
The final Van't Hoff Equation in this article is incorrect. Currently it reads:
however if this were the case, an infinitely dilute solution would have an infinite osmotic pressure which is nonsense. The correct form of the Van't Hoff Equation is:
I don't have the time right now to check the derivation and determine what part is wrong (I expect that it is just between the integral and the first simplified equation with the activity coefficient) so I will just put this here until I have time to come back and check. If someone can either verify that this is wrong, or else tell me why I am wrong about this that would be great. Otherwise I'll change it when I get a chance.
The symbol for molar volume is Vm, rather than V. I replaced the symbol the V, used for volume earlier in the article, with Vm in the section about "Deriving the van't Hoff Equation". Christopher King ( talk) 16:59, 13 November 2019 (UTC)
Also, both "C" and "c" were used for molar concentration in the "Theory and measurement" section. The capital C should be used for number concentration, not molar concentration, so I changed to lower-case c. Christopher King ( talk) 17:17, 13 November 2019 (UTC)
I added the last steps to the van't Hoff equation derivation, which resolves the issue raised above, I think. Christopher King ( talk) 17:54, 13 November 2019 (UTC)
if R = 0.08206 L atm / mol K as it says, it could not possibly be molality, as that would not agree with the dimensions used here. also, according to Chemistry, The Central Science by Brown LeMay and Bursten, osmotic pressure = (n/V)RT= MRT I took the liberty of fixing it. please do not revert it without bringing evidence as to why you would do so. —Preceding unsigned comment added by 69.105.29.230 ( talk) 05:44, 14 April 2010 (UTC)
The equation
and following contain the activity coefficient γ. It would be preferable to state explicitly that the Van t'Hoff equation applies to any solution which is sufficiently dilute that it behaves as an ideal solution in the thermodynamic sense. Then, all reference to activity coefficients in the derivation the Van t'Hoff equation should be removed.
The discussion further down gives an equation for non-ideal solutions as
This does not involve activity coefficients, so, if the above suggestion is adopted, all mention of activity coefficients will be removed, making the presentation much clearer.
A further complication, which has been ignored, is that with ionic solutes, single-ion activity coefficients cannot be obtained by experiment. That issue is also resolved by the suggested change. Petergans ( talk) 12:24, 14 November 2019 (UTC)
Description 37.111.130.148 ( talk) 19:41, 9 September 2022 (UTC)
This is the
talk page for discussing improvements to the
Osmotic pressure article. This is not a forum for general discussion of the article's subject. |
Article policies
|
Find sources: Google ( books · news · scholar · free images · WP refs) · FENS · JSTOR · TWL |
This
level-5 vital article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||||||||||||
|
This article says R = 8.314 but in all the osmotic pressure calculations I have done at uni we have used 0.08206 L atm mol K. Does anyone object to changing this? -- Mdhowe 04:34, 18 October 2006 (UTC)
I have no objection, that is the most commonly used value of R for osmotic pressure and it also uses the simplest dimensions. —Preceding unsigned comment added by 69.105.29.230 ( talk) 06:50, 14 April 2010 (UTC)
I know this phenomenon as Osmotic pressure. I thought everybody did?
Turgid and flacid plant parts
I am going to add a short description of turgid and flacid plant parts with a link to the article stoma. It seems like a good idea to me. Thoughts? 160.94.120.197 17:11, 19 October 2005 (UTC)lotusduck
What about turgour and erectile body parts. Does this not deseve a mention?-- Light current 00:44, 11 January 2006 (UTC)
I understand osmotic pressure as follows:
Solution in semipermeable membrane (permeable only to solvent) exposed to pure solvent. The osmotic pressure is the physical pressure applied to the solution required to prevent movement of pure solvent into the solution.
Another, less accurate, way to define it is the pressure a solution exerts through a semipermeable membrane to draw more solvent into itself.
I have never heard of "turgor pressure" and many erectile tissues in animals rely on blood flow rather than osmosis.
The definition of osmotic pressure given above ("...the physical pressure applied to the solution required to prevent movement of pure solvent into the solution") is a much better definition that the one actually given in the article ("...the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute"). In fact, the hydrostatic pressure is not "produced" by a solution, but rather must be applied by some outside entity, such as the rigid walls of a container resisting volume changes, or the force of gravity acting on a column of solution. I'll make the change unless anyone has any objections. Thewookie55 19:14, 24 September 2007 (UTC)
Tugor and osmotic pressure are different things. Osmotic pressure is the pressure applied from the outside of the cell that pushes the water in. We could say it is the tendancy to take water. ( http://edtech.clas.pdx.edu/osmosis_tutorial/osmotic_pressure3.html) and ( http://www.wisc-online.com/objects/index_tj.asp?objid=NUR4004) Turgor pressure is from inside of the cell done by the water inside. ( http://www.cartage.org.lb/en/themes/Reference/dictionary/Botanical/T/Turgor.html) Klesk
tur·gor (tûr'gər, -gôr')
n.
- The state of being turgid.
- Biology. The normal fullness or tension produced by the fluid content of blood vessels, capillaries, and plant or animal cells.
I have separated out the osmosis and turgor pressure information as osmotic pressure is the cause of turgor pressure, but they are not the same thing. Please feel free to add to either article. pschemp | talk 03:22, 9 July 2006 (UTC)
I think the symbol's wrong here: π = iMRT.
(I don't know how to change it, so I thought I'd just comment —The preceding unsigned comment was added by 90.240.242.118 ( talk) 14:18, 3 March 2007 (UTC).
The correct symbol is π according to Physiology (Berne and Levy, 5th Ed) and Physiology (Costanzo, 3rd Ed). You might be thinking of Φ (Phi) which is the Osmotic co-efficient, and can be added to the equation in the form π = iMRTΦ. However, Osmotic pressure and Osmotic coefficient are not the same thing. Tim Set Match ( talk) 15:25, 5 January 2008 (UTC)
I agree with the first post, it should be Psi, due to the fact Psi is a symbol, in this example symbolising the Osmotic potential. Pi is a constant which I believe isn't correct. e.g. ψ =iMRT. 12:47, 19 September 2008 —Preceding unsigned comment added by 81.110.103.44 ( talk)
Osmotic pressure seems to be important in medicine, there's a lot of talk about it in topics like traumatic brain injury.I'm not knowledgeable enough to write about it yet,but if I do the research would osmotic pressure as a medical topic be better as a separate article? Thanks 216.40.21.8 13:05, 29 July 2007 (UTC)
A solute doesn't 'want' to do anything. —Preceding unsigned comment added by 124.188.96.108 ( talk) 14:34, 15 September 2008 (UTC)
How does one calculate the amount of energy needed to remove a given volume of solvent from a solution? Notice that the concentration of the solution changes as the volume does, and that pressure*volume[=]energy. Thoughts? RSido ( talk) 01:49, 13 May 2009 (UTC)
Does somebody have a derivation of the Morse equation from first principles? 124.168.200.74 ( talk) 14:10, 14 May 2009 (UTC)
Blood, vinegar, Alkaline detergent or lemon juice.Bold text —Preceding unsigned comment added by 24.4.135.218 ( talk) 20:13, 22 March 2010 (UTC)
I came to this article to confirm that the units of osmotic pressure is Osm or mOsm. This was not included on this page, but Googling, I found many instances where it is used. Perhaps this would be of use to other readers. Wakablogger2 ( talk) 21:22, 12 August 2010 (UTC)
On 04:10, 10 January 2013 user:174.57.197.136 changed the value of R from (8.3145 J K-1 mol-1) to (08205746 L atm K-1 mol-1). These are different forms of the same unit, and are both correct. However, in this context, I believe (it's been too long since second semester physics, sorry), that a pressure-based form (as opposed to the Joules form previously in the article) is appropriate, as the usual unit for osmotic pressure is, in fact pressure, and usually Pascals. But as the usual unit is Pascals, I'd think the kPa form (8.3145 L kPa K−1 mol−1) form of R would be preferred, not the atm form as it reads now. Note that the numerical value of the kPa form is the same as the Joules form.
I see this has been slightly discussed here before (not to mention the multiple decades since I've had to work one of these) so before changing it to (8.3145 L kPa K−1 mol−1), I thought I'd ask. Rwessel ( talk) 07:30, 10 January 2013 (UTC)
Dear Osmosis Experts: A friend who knows more physics than I do, but who is not a Wiki editor, pointed out what is to him a mis-wording in "This process will stop once the pressures of the water and sugar water on both sides of the membrane become equal." His suggested replacement: "The process stops when the partial pressure of water on the sugar-water side equals the pressure of the pure water on the other side." His point, I think, is that it is not equality of total pressure between the two liquids, but rather equality of water to water, disregarding the additional pressure due to the sugar. I am reluctant to edit the change myself, because I am not an osmoticist. Would one of you experts please make this change if you see it as valid? Two additional notes: (1) In the sentence before that one, how about replacing "the two solutions" with "the two liquids," (including the comma), as pure water is technically not a "solution", right? (2) My friend introduces the phrase "partial pressure"; Wikipedia has an article on it, but it seems to deal only with gases. Would a link to partial pressure be appropriate? Kotabatubara ( talk) 19:01, 10 November 2015 (UTC)
The final Van't Hoff Equation in this article is incorrect. Currently it reads:
however if this were the case, an infinitely dilute solution would have an infinite osmotic pressure which is nonsense. The correct form of the Van't Hoff Equation is:
I don't have the time right now to check the derivation and determine what part is wrong (I expect that it is just between the integral and the first simplified equation with the activity coefficient) so I will just put this here until I have time to come back and check. If someone can either verify that this is wrong, or else tell me why I am wrong about this that would be great. Otherwise I'll change it when I get a chance.
The symbol for molar volume is Vm, rather than V. I replaced the symbol the V, used for volume earlier in the article, with Vm in the section about "Deriving the van't Hoff Equation". Christopher King ( talk) 16:59, 13 November 2019 (UTC)
Also, both "C" and "c" were used for molar concentration in the "Theory and measurement" section. The capital C should be used for number concentration, not molar concentration, so I changed to lower-case c. Christopher King ( talk) 17:17, 13 November 2019 (UTC)
I added the last steps to the van't Hoff equation derivation, which resolves the issue raised above, I think. Christopher King ( talk) 17:54, 13 November 2019 (UTC)
if R = 0.08206 L atm / mol K as it says, it could not possibly be molality, as that would not agree with the dimensions used here. also, according to Chemistry, The Central Science by Brown LeMay and Bursten, osmotic pressure = (n/V)RT= MRT I took the liberty of fixing it. please do not revert it without bringing evidence as to why you would do so. —Preceding unsigned comment added by 69.105.29.230 ( talk) 05:44, 14 April 2010 (UTC)
The equation
and following contain the activity coefficient γ. It would be preferable to state explicitly that the Van t'Hoff equation applies to any solution which is sufficiently dilute that it behaves as an ideal solution in the thermodynamic sense. Then, all reference to activity coefficients in the derivation the Van t'Hoff equation should be removed.
The discussion further down gives an equation for non-ideal solutions as
This does not involve activity coefficients, so, if the above suggestion is adopted, all mention of activity coefficients will be removed, making the presentation much clearer.
A further complication, which has been ignored, is that with ionic solutes, single-ion activity coefficients cannot be obtained by experiment. That issue is also resolved by the suggested change. Petergans ( talk) 12:24, 14 November 2019 (UTC)
Description 37.111.130.148 ( talk) 19:41, 9 September 2022 (UTC)