Talk:Partial pressure

Technical accessibility

This article could use some work to make it more accessible to people who are not already familiar with the principles of thermodynamics and kinetic theory. I'm sure that schoolchildren and even adults who haven't had basic science education would find the explication of fundamental concepts here to be quite helpful. I've already drafted similar improvements for Phase (matter) (see my 10 July 2005 edits there), which are illustrative of what I have in mind. -- Beland 13:29, 10 July 2005 (UTC)

Think I made it about as simple/accessible as it's going to get; just wanted to mention here that I removed the technical template from here as well as the main article (there was one here, on the talk page, for some reason) - Straker 20:26, 18 October

I appreciate the effort of writing the article, however I agree it could be more approachable for a wider audience. That doesn't mean you have to remove any equations. Rather just add some clarifying examples.

For example, add to the first section something like this: "Earth's atmosphere is 14.7 psi at sea level, and is composed of 79% nitrogen and 20% oxygen. The partial pressure of oxygen is therefore 20% * 14.7, or 2.94 psi. The partial pressure of nitrogen is 79% * 14.7 or 11.61 psi."

Further you could illustrate this by saying: "Astronauts wearing space suits breath pure oxygen at 4.2 psi. Despite the low pressure, they have more breathable oxygen available than at sea level on earth. This is because the partial pressure of pure oxygen at 4.2 psi is just that -- 4.2 psi, whereas on earth at sea level the partial pressure of oxygen is 20% * 14.7 psi or 2.94 psi".

Suggest revising the last section about safe ppO2 ranges, since the actual safe range is a function of time AND ppO2. Humans can survive with less than 1 psi O2 for short periods without developing anoxia, and 90 psi pure O2 for short periods without developing oxygen toxicity. There's a nice graph you could probably get from this page to illustrate: [1] Joema 04:19, 25 December 2005 (UTC)

Biological Applications

Whilst this article is very well written and very fully instructed in the ideals of pressures and pressure gradients, it is missing something. I am thinking of the possibilty of a biological side to this topic. The ideas surrounding partial pressures of gases in the blood systems of animals allowing for transport and dissociation at tissues and the lungs. This is a relatively simple idea but one I think would greatly benefit this already good area of research. —Preceding unsigned comment added by 86.144.167.89 (talk • contribs) April 26, 2006 (UTC)

Needs quite a bit of editing

In my opinion, this article needs quite a bit of editing to make it scientifically and technically sound. It also needs to be consistent throughout the article (for example, it uses different notation in different sections, notably the section on diving breating gases). The categories to which it is assigned really need to be more appropriate. For example, the list of categories needs to include Category:Chemical properties. Also, there is very little thermodynamics involved in the article as it now stands.

Someone who is really experienced in physical chemistry needs to do some major revisions. I will make some of the more obviously needed changes today .. and I may return later to do some re-writing. - mbeychok 17:23, 24 May 2006 (UTC)

It took me a bit longer than I estimated a few days ago, but I have now completely re-arranged and hopefully improved this article. I believe it is now much more scientifically and technically correct. I not only re-arranged and re-titled some of the sections, I also eliminated some of the redundant material which is very adequately contained in other articles (see the links in the "See also" section). - mbeychok 22:44, 26 May 2006 (UTC)

How do you spell jargon?

J-A-R-G-O-N... make it easier to understand for the rest of us... --toaster 22:16, 27 September 2006 (UTC)

toaster, there are quite literally hundreds, if not thousands, of articles in Wikipedia that I find completely incomprehensible. For example: Quantum mechanics, atomic physics, Psycholinguistics, Generative linguistics, Algorithmic information theory, String theory, Cosmology, at least 75% or more of the Thermodynamics articles, and 90% or more of the advanced Mathematics articles, etc. etc. All of those subjects have arcane terminologies or jargons that are beyond my fields of knowledge.I just accept the fact that those subjects simply cannot be "dumbed down" enough for me to understand them unless I am willing to spend months or years of study to become familiar with them. None of us can know everything. - mbeychok 23:55, 27 September 2006 (UTC)

But all is not lost. With some short intro phrasing and use of metaphor, even highly technical articles can in theory be made somewhat accessable to intelligent layman, until you get to the math. See the Feynman physics lectures (and even more, his QED book) for a valiant attempt at this. Also books by Steven Weinberg and Leon Lederman. See technical writing for more on the problem. This is very difficult writing to do, since people who really know the subject often forget how much they know, and are used to years of shorthand use. Those who are in a better position to explain to laymen, often lack the actually rigorous tech understanding, particularly when the math gets upper-division. SBHarris 19:19, 8 December 2006 (UTC)

Henry's constant

why is henry's constant labeled as "k" instead of "H"? —Preceding unsigned comment added by 68.107.105.71 (talk • contribs) November 6, 2006 (UTC)

Just by convention ... although some books and other references do use H. However, as someone said, "a rose is a rose by any another name" if I got that quotation right??? mbeychok 19:02, 6 November 2006 (UTC)es

No. "Rose is a rose is a rose"-- Gertrude Stein. "What's in a name? That which we call a rose by any other name would smell as sweet." -- Romeo and Juliet/Shakespeare. H is not used for Henry's law because in chemistry it's already taken as the symbol for enthalpy, where the H no doubt is used because it signifies "Heat" (the same as enthalpy at constant pressure)-- a much more important concept. SBHarris 23:29, 18 June 2007 (UTC)

I just to know what is the relation between the henry's constant and temperature as well as the solubility of the given liquid?--59.95.203.103 17:28, 10 September 2007 (UTC)hetal shah

Hetal shah, to answer your comment, see the Henry's law article ... especially the section on Temperature dependence of the Henry constant. - mbeychok 18:34, 10 September 2007 (UTC)

Partial pressures in liquids are not the same as pressures that would obtain if the liquid vanished

The article text states:

In chemistry, the partial pressure of a gas in a mixture of gases or of a gas dissolved in a liquid is the pressure which that gas would have if all other components of the gas mixture or liquid suddenly vanished without its temperature changing.

This is true for ideal gases, but in general not true of liquids (nor does the ref given say it's true in liquids), and this fact is due to non-unity Henry's constants. Obviously, two different ideal gases at the same gas partial pressures have the same concentration, but they may well have (and generally will have) differing concentrations in a liquid in equilibrium with the gas. In such a case, if the liquid vanished, the relative gas concentrations would change. Liquids can pack more or less gas moles per volume than the gas above them. Cold water, for example, has about half as much oxygen per liter as the air above it. If the water vanished in an equilibrium mix of air and water, obviously the remaining air would have to accomodate a volume of gas with a lower oxygen volumetric content than air, and thus O2 partial pressure for the new mix would drop. I'll fix this in the text. SBHarris 22:45, 23 November 2006 (UTC)

Very good article. Helped me a lot.

In my opinion it is a very good article it helped me a ton with my science fair project and it is very useful in learning about lung capacity. —Preceding unsigned comment added by 66.119.143.249 (talk • contribs) December 7, 2006

Disagree with the proposed merger

I thoroughly disagree with the proposed merger. There may be some redundancy between the two articles, but that is true of a great many Wikipedia articles. I see no great benefit or reason for this specific proposed merger. - mbeychok 19:22, 12 March 2007 (UTC)

I also disagree. This law belongs here. It can be copied, but not moved elsewhere. Xyzt1234 14:37, 26 April 2007 (UTC)

It is not necessary .. the link to the partial pressure is working enough. —Preceding unsigned comment added by 58.181.106.119 (talk • contribs) 18 June 2007 (UTC)

Removing proposed merger tag

The proposed merger tag was placed on Feb.22, 2007. After 4 months, there have been 3 comments disagreeing with the proposed merger and none that agree with it. I am therefore removing the tag. - mbeychok 18:45, 18 June 2007 (UTC)

Remove the diving stuff

In my opinion the subsection dealing with the partial pressure in breathing gas should be removed from this article as it is much too specific and has no real physical relevance to the concept of partial pressures. Opinions? —Preceding unsigned comment added by 220.101.176.63 (talk) 10:53, 1 October 2008 (UTC)

I don't think it's too specific, this is something important to understanding biology and is an issue that can draw a lot of attention to the concept of partial pressure. DB (talk) 17:47, 11 June 2011 (UTC)

Agree. Diving is probably the most common application of oxygen partial pressure in biology. It's also used in aerospace, but (for obvious reasons) not nearly so many people are astronauts and jet pilots are are sport scuba divers. We can also add a bit on lower partial pressures of oxygen in spacesuits and at high altitude, for better balance. See the question at the end of this TALK page, which can be answered in these terms. There's a section on pressure in the wiki article on space suit, which is also illustrative. SBHarris 19:58, 11 June 2011 (UTC)

Broken Link

The link to the "Ohio State Uni notes" (http://undergrad-ed.chemistry.ohio-state.edu/chemapplets/GasLaws/DaltonsLaw.html) is no longer available. Maybe that someone could fix that (I don't know how to do it). User:87.65.146.187 10:41, 30 November 2008

Symbol for pressure

Pressure is a physical quantity. Commonly for pressures, p is used as a symbol in physics. The capitol P stands for power... --95.89.0.171 (talk) 21:13, 8 October 2009 (UTC)

What's a capitol P? In physical chemistry, capital P is used for pressure, as in PV = nRT.96.54.32.44 (talk) 07:01, 25 December 2010 (UTC)

Better late than never. Changed all the occurrences of upper case P to lower case p. mbeychok (talk) 21:44, 29 April 2012 (UTC)

Altitude training

I followed a link from there to this article and I'm having trouble understanding how the pressure change on oxygen causes the different training effect. Is this explained anywhere? DB (talk) 17:47, 11 June 2011 (UTC)

The chemical reactivity of oxygen is due to its partial pressure, which is lower at higher altitudes. It is partial pressure that your body responds to in all ways, and altitude changes that (even if the percent oxygen is not changed). I'll put in an extra bit in the article to make that clearer. SBHarris 19:55, 11 June 2011 (UTC)

Definition

The definition could be rephrased shorter by saying hypothetical pressure instead of the pressure the gas component would have if...--86.125.152.170 (talk) 10:35, 21 November 2012 (UTC)

Also the definition includes the additivity of the partial pressures of components.

The definition implies an isothermal process .--79.119.217.178 (talk) 10:48, 21 November 2012 (UTC)

The first sentence of the article seems to imply that the given definition of "partial pressure" applies only to ideal gases. I've removed the term "ideal" from the first sentence. — Preceding unsigned comment added by 142.157.149.8 (talk) 22:31, 24 June 2013 (UTC)

This article is keeps growing and growing to include unnecessary subjects

The subject of this article is "Partial pressure":

• Why does it need to include a section on "Henry's Law" when there is an existing article entitled "Henry's law" which is much more detailed?
• Also, why does this article need to include a section on "Vapor pressure" when there is also an existing article entitled "Vapor pressure" which is much more detailed?
• Why does the "Vapor pressure" section need to discuss normal boiling points when there is also an existing article entitled "Boiling point" which discusses normal boiling points in much more detail.
• Why does this article need that grossly extensive template (at the bottom) which is entitled "Diving medicine, physiology, physics and environment"? I repeat that this is an article about "Partial pressure".

Who decided that this article was to be an omnibus article covering so many diverse subjects which are covered by existing articles elsewhere in WP? mbeychok (talk) 19:40, 12 January 2013 (UTC)

Variations of English

At present, this article employs a mixture of British and American English but should use just one variety per WP:ARTCON. Our guidance is at WP:ENGVAR and since there are no strong national ties for the topic, the style of English should be set by that used by the first major contributor, per WP:RETAIN. I believe the first major contribution that differentiated between en-gb and en-us was this edit, which used the British spelling 'metres'. I will therefore change the spellings throughout to use British English. --RexxS (talk) 16:51, 19 September 2014 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Partial pressure/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.

I have rated this article as being in Class A because it has all of the elements required for that class as described in the Assessment article. It is well written and has all of sections required by standard Wiki practice. However, I do feel it could still benefit from more improvement. It is of High importance to chemists and to chemical engineers. I cannot speak for its importance to Physicists. - mbeychok 05:45, 4 December 2006 (UTC)

Last edited at 05:46, 4 December 2006 (UTC). Substituted at 02:19, 30 April 2016 (UTC)

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Partial pressure in the setting of ABG

The article mentions Partial Pressure of Arterial Blood gasses in the medical section, but doesn't explain why this is particularly significant in the medical context as a useful measurement. Therefore the why tag has been added. 71.91.178.54 (talk) 22:22, 20 October 2018 (UTC)

Minimum partial pressure of oxygen required for human life.

This articles reflects that the minimum partial pressure of oxygen ( O2 ) needed to sustain a human is 16KPa.

"The minimum safe lower limit for the partial pressures of oxygen in a gas mixture is 0.16 bars (16 kPa) absolute. Hypoxia and sudden unconsciousness becomes a problem with an oxygen partial pressure of less than 0.16 bar absolute."

This statement does not indicate a reference, but I feel it is patently false. At sea level on Earth the pressure is 14.7 lbs/in2 or 1 bar or 100 KPa. With the atmosphere made up of approximately 20% oxygen this yields a partial pressure of oxygen as 20 KPa or 200 mbars or .2 bar. Based on common atmospheric pressures for various altitudes I show the following:

alt in m alt in ft atmospheric pressure partial pressure of oxygen notes

 0             0                 100 KPa                     20.0 KPa                Sea level
 1524         5000                 84.3 KPa                   16.2 KPa      Denver, Colorado area (this is just above the lower limit sited in the page)
  2134        7000                 78.2 KPa                   15.6 KPa      This is where I have lived for 27 year (S of Elizabeth Colorado)
  2591        8500                 71.5 KPa                   14.3 KPa      This was my previous home I lived in for 6 years (On robinson hill road north west of Golden, Colorado)
  3094       10,151                69.6 KPa                   13.9 KPa      City of Leadville, CO - spent 4 days on vacation here
  3658       12,002                63.0 KPa                   12.6 KPa      City of Lhasa, Tibet
  5099       16,724                60.1 KPa                   12.0 KPa      City of La Rinconada, Peru
  6000       19,685                47.5 KPa                    9.5 KPa      Maximum human sustainability (Nat Geo, and several climber journals)
  6096       20,000                46.6 KPa                    9.32KPa      Top of Mt. McKinley in Alaska.
  8848       29,032                30.0 KPa                    6.0 KPa      Top of Mt. Everest. 

I would think that the minimum partial pressure of oxygen would be about 9.5 +/- 0.5 for long term habitation and much lower for short amounts of time. I have hiked up several of Colorado's "14ers", mountain peaks above 14,000 ft elevation (4267 meters). While I did notice the lower air pressure I was able to hike up without oxygen carrying a backpack at over 60 years of age.

Given the cities cited above in Tibet and Peru and Colorado, all of which have a lower partial pressure of oxygen than the 16 KPa sited on the page. This figure cannot be true.

I have been unable to locate any citation showing a minimum partial pressure of oxygen for human life. The Apollo missions used much lower pressures, between 23 KPa and 34 KPa, but these were 100% oxygen. These were in the command module, LEM and EVA suits on the moon.

One supporting citation I found was by Dr. Michael J. Mulick, DO, Children’s Hospital Los Angeles, Los Angeles, CA. The excerpt is from an article in "Society for Pediatric Anesthesia" Volume 27, Number 3. "Climbing Mt. McKinley, one of the world’s seven tallest summits was one of the hardest things I have ever done. Mt. McKinley, known better by its native name Denali, meaning “The High One”, is the highest peak in North America at 20,322 feet.

My oxygen saturation on the summit was probably in the low 80's. The air temperature was well below zero with wind speeds up to 50 miles per hour. The only things I could focus on were to eat, drink, and keep moving. Climbers at high altitudes experience hypobaric hypoxia. Low barometric pressure causes the partial pressure of alveolar oxygen to be reduced at altitude as demonstrated in the alveolar gas equation:

PA02 = Fi02 * (Pb - PH2O) - (PaCO2/RQ)

On the summit of Denali, the barometric pressure is around 360 mm Hg which translates into a more than 50% reduction in available oxygen. This has profound effects on cognition, cardiopulmonary function, appetite, and sleep."

In the table above I show partial pressure of oxygen at sea level at 20 KPa and at the summit of McKinley at 9.32 KPa. This squares with his statement of "more then a 50% reduction".

Mike-ASelene (talk) 19:27, 19 May 2022 (UTC)