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href="#Categorization"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Categorization</span> </div> </a> <span class="ext-discussiontools-init-sidebar-meta">4 comments</span> <ul id="toc-Categorization-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Accuracy?" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Accuracy?"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Accuracy?</span> </div> </a> <span class="ext-discussiontools-init-sidebar-meta">3 comments</span> <ul id="toc-Accuracy?-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Vapor_pressure_graph_appears_to_be_labeled_wrong" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Vapor_pressure_graph_appears_to_be_labeled_wrong"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Vapor pressure graph appears to 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//upload.wikimedia.org/wikipedia/commons/thumb/5/59/Nuvola_apps_edu_science.svg/50px-Nuvola_apps_edu_science.svg.png 2x" data-file-width="128" data-file-height="128"/></a></span></td><td class="wpb-header-combined"><a href="/wiki/Wikipedia:WikiProject_Chemistry" title="Wikipedia:WikiProject Chemistry">Chemistry</a> <span class="wpb-header-bubbles import-low">Low‑importance</span></td></tr><tr><td class="mbox-text wpb-main" colspan="2"><table><tbody><tr><td class="mbox-image wpb-image"><span typeof="mw:File"><a href="/wiki/File:Nuvola_apps_edu_science.svg" class="mw-file-description"><img alt="WikiProject icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/59/Nuvola_apps_edu_science.svg/50px-Nuvola_apps_edu_science.svg.png" decoding="async" width="50" height="50" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/59/Nuvola_apps_edu_science.svg/75px-Nuvola_apps_edu_science.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/59/Nuvola_apps_edu_science.svg/100px-Nuvola_apps_edu_science.svg.png 2x" data-file-width="128" data-file-height="128"/></a></span></td><td class="mbox-text">This article is within the scope of <b><a href="/wiki/Wikipedia:WikiProject_Chemistry" title="Wikipedia:WikiProject Chemistry">WikiProject Chemistry</a></b>, a collaborative effort to improve the coverage of <a href="/wiki/Chemistry" title="Chemistry">chemistry</a> on Wikipedia. If you would like to participate, please visit the project page, where you can join <a href="/wiki/Wikipedia_talk:WikiProject_Chemistry" title="Wikipedia talk:WikiProject Chemistry">the discussion</a> and see a list of open tasks.<span class="metadata wpb-metadata"><span class="wpb-project">Chemistry</span><span class="wpb-project_link">Wikipedia:WikiProject Chemistry</span><span class="wpb-banner_name">Template:WikiProject Chemistry</span><span class="wpb-assessment_cat">Chemistry articles</span></span></td><td class="mbox-empty-cell"></td></tr><tr><td class="assess import-low"><a href="/wiki/Category:Low-importance_Chemistry_articles" title="Category:Low-importance Chemistry articles">Low</a></td><td class="mbox-text" colspan="2">This article has been rated as <b>Low-importance</b> on the <a href="/wiki/Wikipedia:WikiProject_Chemistry/Assessment#Importance_scale" title="Wikipedia:WikiProject Chemistry/Assessment">project's importance scale</a>.</td></tr></tbody></table></td></tr></tbody></table></td></tr></tbody></table> <p>I think there is an error in the first equation. For example at a temperature of 25°C (298.15K) the calculated vapor pressure is 33.8mmHg. <small class="autosigned">— Preceding <a href="/wiki/Wikipedia:Signatures" title="Wikipedia:Signatures">unsigned</a> comment added by <a href="/wiki/Special:Contributions/143.93.17.22" title="Special:Contributions/143.93.17.22">143.93.17.22</a> (<a href="/w/index.php?title=User_talk:143.93.17.22&action=edit&redlink=1" class="new" title="User talk:143.93.17.22 (page does not exist)">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-143.93.17.22-2016-04-20T15:13:00.000Z" class="ext-discussiontools-init-timestamplink">15:13, 20 April 2016 (UTC)</a></small><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-143.93.17.22-2016-04-20T15:13:00.000Z"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-143.93.17.22-2016-04-20T15:13:00.000Z"></span> </p><p><span data-mw-comment-start="" id="c-212.159.122.240-2009-07-20T14:03:00.000Z"></span>The values of the Antoine equation do not match those given for water on the Antoine equation page. <span style="font-size: smaller;" class="autosigned">—Preceding <a href="/wiki/Wikipedia:Signatures" title="Wikipedia:Signatures">unsigned</a> comment added by <a href="/wiki/Special:Contributions/212.159.122.240" title="Special:Contributions/212.159.122.240">212.159.122.240</a> (<a href="/wiki/User_talk:212.159.122.240" title="User talk:212.159.122.240">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-212.159.122.240-2009-07-20T14:03:00.000Z" class="ext-discussiontools-init-timestamplink">14:03, 20 July 2009 (UTC)</a></span><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-212.159.122.240-2009-07-20T14:03:00.000Z"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-212.159.122.240-2009-07-20T14:03:00.000Z"></span> </p><p><span data-mw-comment-start="" id="c-SWAdair-2006-11-21T06:17:00.000Z"></span>Spelled vapour in the article title, can we fix this????? change it to the american spelling "vapor" </p> <dl><dd>Please see <a href="/wiki/Wikipedia:Manual_of_Style#National_varieties_of_English" title="Wikipedia:Manual of Style">Wikipedia:Manual_of_Style#National_varieties_of_English</a>. <a href="/wiki/User:SWAdair" title="User:SWAdair">SWAdair</a> <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-SWAdair-2006-11-21T06:17:00.000Z" class="ext-discussiontools-init-timestamplink">06:17, 21 November 2006 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-SWAdair-2006-11-21T06:17:00.000Z"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-SWAdair-2006-11-21T06:17:00.000Z"></span></dd></dl> <ul><li><span data-mw-comment-start="" id="c-Msaunier-2012-02-20T20:01:00.000Z-SWAdair-2006-11-21T06:17:00.000Z"></span>Wikipedia policy is to leave this as-is, although I admit that having the two articles with different spellings bugs me as well. C'est la vie! <a href="/wiki/User:Msaunier" title="User:Msaunier">Msaunier</a> (<a href="/wiki/User_talk:Msaunier" title="User talk:Msaunier">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Msaunier-2012-02-20T20:01:00.000Z-SWAdair-2006-11-21T06:17:00.000Z" class="ext-discussiontools-init-timestamplink">20:01, 20 February 2012 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Msaunier-2012-02-20T20:01:00.000Z-SWAdair-2006-11-21T06:17:00.000Z"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Msaunier-2012-02-20T20:01:00.000Z-SWAdair-2006-11-21T06:17:00.000Z"></span></li></ul> <p><span data-mw-comment-start="" id="c-76.77.246.138-2009-05-01T18:56:00.000Z"></span>OK...so what does "exp" stand for in the simplified formula? </p><p><a href="/wiki/Special:Contributions/76.77.246.138" title="Special:Contributions/76.77.246.138">76.77.246.138</a> (<a href="/w/index.php?title=User_talk:76.77.246.138&action=edit&redlink=1" class="new" title="User talk:76.77.246.138 (page does not exist)">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-76.77.246.138-2009-05-01T18:56:00.000Z" class="ext-discussiontools-init-timestamplink">18:56, 1 May 2009 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-76.77.246.138-2009-05-01T18:56:00.000Z"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-76.77.246.138-2009-05-01T18:56:00.000Z"></span> </p><p><span data-mw-comment-start="" id="c-99.233.145.177-2010-03-16T01:11:00.000Z"></span>{<br/> Based on calculations that I have made, it seems that the "exp" in the first formula stand for e^x (exponentiation over base e), and that the "log" in the log(P)-vs-1/T graph in the accompanying figure stands for log base 10. I calculated the vapour pressure of water at 20°C = 293K, and got:<br/> 1) 2.35 kPa from the first formula by assuming e^x<br/> 2) 2.33 kPa from the Antoine equation by using the parameter values for water between 0°C and 100°C on the Antoine equation page<br/> 3) 2.2--2.5 kPa from the graph by assuming log base 10.<br/> --Jason Pereira, <a href="/wiki/Special:Contributions/99.233.145.177" title="Special:Contributions/99.233.145.177">99.233.145.177</a> (<a href="/w/index.php?title=User_talk:99.233.145.177&action=edit&redlink=1" class="new" title="User talk:99.233.145.177 (page does not exist)">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-99.233.145.177-2010-03-16T01:11:00.000Z" class="ext-discussiontools-init-timestamplink">01:11, 16 March 2010 (UTC)</a>.<span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-99.233.145.177-2010-03-16T01:11:00.000Z"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-99.233.145.177-2010-03-16T01:11:00.000Z"></span><br/> } </p> <meta property="mw:PageProp/toc"/> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Quibble_about_the_definition" data-mw-thread-id="h-Quibble_about_the_definition-2016-11-26T21:05:00.000Z"><span data-mw-comment-start="" id="h-Quibble_about_the_definition-2016-11-26T21:05:00.000Z"></span>Quibble about the definition<span data-mw-comment-end="h-Quibble_about_the_definition-2016-11-26T21:05:00.000Z"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Talk:Vapour_pressure_of_water&action=edit&section=1" title="Edit section: Quibble about the definition"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span><div class="ext-discussiontools-init-section-bar"><div class="ext-discussiontools-init-section-metadata"></div><div class="ext-discussiontools-init-section-actions"></div></div></div> <p><a href="/w/index.php?title=User:Dtprice&action=edit&redlink=1" class="new" title="User:Dtprice (page does not exist)"><span data-mw-comment-start="" id="c-Dtprice-2016-11-26T21:05:00.000Z-Quibble_about_the_definition"></span>Dtprice</a> (<a href="/wiki/User_talk:Dtprice" title="User talk:Dtprice">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Dtprice-2016-11-26T21:05:00.000Z-Quibble_about_the_definition" class="ext-discussiontools-init-timestamplink">21:05, 26 November 2016 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Dtprice-2016-11-26T21:05:00.000Z-Quibble_about_the_definition"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Dtprice-2016-11-26T21:05:00.000Z-Quibble_about_the_definition"></span> </p><p><span data-mw-comment-start="" id="c-Dtprice-2016-11-26T21:17:00.000Z-Quibble_about_the_definition"></span>The opening statements are not really correct, as they confuse the vapo(u)r pressure with the vapour pressure at saturation. I would write the explanation/definition as something like: </p> <ul><li>The <b>vapor pressure of water</b> is the pressure exerted by molecules of <a href="/wiki/Water_vapor" title="Water vapor">water vapor</a> in gaseous form (whether pure or in a mixture of ideal gases such as air). With increasing pressure, or decreasing temperature, the water vapor content approaches saturation and at the saturation point it will be <a href="/wiki/Saturated_vapor" class="mw-redirect" title="Saturated vapor">in thermodynamic equilibrium with its condensed state</a>. At even higher pressures or lower temperatures some of the <a href="/wiki/Properties_of_water" title="Properties of water">water</a> <a href="/wiki/Condenses" class="mw-redirect" title="Condenses">condenses</a> into liquid form, leaving the gaseous water vapor at or close to saturation.</li></ul> <p>I would also want to add something about vapour pressure over ice. Something like: </p> <ul><li>At temperatures below the freezing point, condensation will generally result in ice formation. The form of the exponential relationship between temperature and water vapour over ice is similar to that for water vapour and liquid water at temperatures above freezing, but differs in the details, requiring different parameterisation. <small class="autosigned">— Preceding <a href="/wiki/Wikipedia:Signatures" title="Wikipedia:Signatures">unsigned</a> comment added by <a href="/w/index.php?title=User:Dtprice&action=edit&redlink=1" class="new" title="User:Dtprice (page does not exist)">Dtprice</a> (<a href="/wiki/User_talk:Dtprice#top" title="User talk:Dtprice">talk</a> • <a href="/wiki/Special:Contributions/Dtprice" title="Special:Contributions/Dtprice">contribs</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Dtprice-2016-11-26T21:17:00.000Z-Quibble_about_the_definition" class="ext-discussiontools-init-timestamplink">21:17, 26 November 2016 (UTC)</a><span data-mw-comment-end="c-Dtprice-2016-11-26T21:17:00.000Z-Quibble_about_the_definition"></span></small><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Dtprice-2016-11-26T21:17:00.000Z-Quibble_about_the_definition"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span></li></ul> <p><br/><span data-mw-comment-start="" id="c-Jhunt29-2021-10-09T01:32:00.000Z-Quibble_about_the_definition"></span> This problem remains uncorrected, and for some purposes, it is more than a quibble. This article discusses the saturated vapour pressure without explicitly defining that </p><p>Modifying the preceding comments, perhaps: The <b>vapor pressure of water</b> is the pressure exerted by molecules of <a href="/wiki/Water_vapor" title="Water vapor">water vapor</a> in gaseous form (whether pure or in a mixture with other gases such as air). This increases with increasing temperature of the liquid water. The maximum possible vapour pressure at steady state increases with the temperature of the gas phase. These are at equilibrium when the vapour pressure equals the saturated vapour pressure. The boiling point of water is the temperature at which the saturated vapour pressure equals the atmospheric pressure, and hence this decreases with decreasing atmospheric pressure.<a href="/w/index.php?title=User:Jhunt29&action=edit&redlink=1" class="new" title="User:Jhunt29 (page does not exist)">Jhunt29</a> (<a href="/wiki/User_talk:Jhunt29" title="User talk:Jhunt29">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Jhunt29-2021-10-09T01:32:00.000Z-Quibble_about_the_definition" class="ext-discussiontools-init-timestamplink">01:32, 9 October 2021 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Jhunt29-2021-10-09T01:32:00.000Z-Quibble_about_the_definition"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Jhunt29-2021-10-09T01:32:00.000Z-Quibble_about_the_definition"></span> </p><p><span data-mw-comment-start="" id="c-Jhunt29-2021-10-09T02:19:00.000Z-Quibble_about_the_definition"></span>On reflection, alternatively, this page should be re-titled "Saturated vapor pressure of water". It is helpful to those who wish to understand why you cannot breath at 9000m altitude, or why there is a maximum height for a siphon, but not useful for understanding why your pool looses more water and gets colder when the wind blows on a hot day <a href="/w/index.php?title=User:Jhunt29&action=edit&redlink=1" class="new" title="User:Jhunt29 (page does not exist)">Jhunt29</a> (<a href="/wiki/User_talk:Jhunt29" title="User talk:Jhunt29">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Jhunt29-2021-10-09T02:19:00.000Z-Quibble_about_the_definition" class="ext-discussiontools-init-timestamplink">02:19, 9 October 2021 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Jhunt29-2021-10-09T02:19:00.000Z-Quibble_about_the_definition"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Jhunt29-2021-10-09T02:19:00.000Z-Quibble_about_the_definition"></span> </p><p><span data-mw-comment-start="" id="c-Jhunt29-2021-10-10T07:22:00.000Z-Quibble_about_the_definition"></span>I changed the introduction, hopefully in a way that meets the various meanings of the phrase. If this is not just arbitrarily reversed, I will add some below freezing values to the vapour pressure table.<a href="/w/index.php?title=User:Jhunt29&action=edit&redlink=1" class="new" title="User:Jhunt29 (page does not exist)">Jhunt29</a> (<a href="/wiki/User_talk:Jhunt29" title="User talk:Jhunt29">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Jhunt29-2021-10-10T07:22:00.000Z-Quibble_about_the_definition" class="ext-discussiontools-init-timestamplink">07:22, 10 October 2021 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Jhunt29-2021-10-10T07:22:00.000Z-Quibble_about_the_definition"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Jhunt29-2021-10-10T07:22:00.000Z-Quibble_about_the_definition"></span> </p> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Boiling_point_arrow_on_log_graph_is_wrong" data-mw-thread-id="h-Boiling_point_arrow_on_log_graph_is_wrong-2011-09-12T07:34:00.000Z"><span data-mw-comment-start="" id="h-Boiling_point_arrow_on_log_graph_is_wrong-2011-09-12T07:34:00.000Z"></span>Boiling point arrow on log graph is wrong<span data-mw-comment-end="h-Boiling_point_arrow_on_log_graph_is_wrong-2011-09-12T07:34:00.000Z"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Talk:Vapour_pressure_of_water&action=edit&section=2" title="Edit section: Boiling point arrow on log graph is wrong"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span><div class="ext-discussiontools-init-section-bar"><div class="ext-discussiontools-init-section-metadata"></div><div class="ext-discussiontools-init-section-actions"></div></div></div> <p><span data-mw-comment-start="" id="c-64.118.100.243-2011-09-12T07:34:00.000Z-Boiling_point_arrow_on_log_graph_is_wrong"></span>The log graph shows the boiling point with with an arrow at log P = 2.4 when it should be at log P = 2.01 <span style="font-size: smaller;" class="autosigned">— Preceding <a href="/wiki/Wikipedia:Signatures" title="Wikipedia:Signatures">unsigned</a> comment added by <a href="/wiki/Special:Contributions/64.118.100.243" title="Special:Contributions/64.118.100.243">64.118.100.243</a> (<a href="/w/index.php?title=User_talk:64.118.100.243&action=edit&redlink=1" class="new" title="User talk:64.118.100.243 (page does not exist)">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-64.118.100.243-2011-09-12T07:34:00.000Z-Boiling_point_arrow_on_log_graph_is_wrong" class="ext-discussiontools-init-timestamplink">07:34, 12 September 2011 (UTC)</a></span><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-64.118.100.243-2011-09-12T07:34:00.000Z-Boiling_point_arrow_on_log_graph_is_wrong"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-64.118.100.243-2011-09-12T07:34:00.000Z-Boiling_point_arrow_on_log_graph_is_wrong"></span> </p> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Units_!!!!" data-mw-thread-id="h-Units_!!!!-2010-10-15T17:50:00.000Z"><span id="Units_.21.21.21.21"></span><span data-mw-comment-start="" id="h-Units_!!!!-2010-10-15T17:50:00.000Z"></span>Units !!!!<span data-mw-comment-end="h-Units_!!!!-2010-10-15T17:50:00.000Z"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Talk:Vapour_pressure_of_water&action=edit&section=3" title="Edit section: Units !!!!"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span><div class="ext-discussiontools-init-section-bar"><div class="ext-discussiontools-init-section-metadata"></div><div class="ext-discussiontools-init-section-actions"></div></div></div> <p><span data-mw-comment-start="" id="c-G4oep-2010-10-15T17:50:00.000Z-Units_!!!!"></span>OMG ! Who uses mmHg as units of pressure nowadays ! For goodness' sake get real and start using proper SI units that people will understand and can use. <small><span class="autosigned">—Preceding <a href="/wiki/Wikipedia:Signatures" title="Wikipedia:Signatures">unsigned</a> comment added by <a href="/w/index.php?title=User:G4oep&action=edit&redlink=1" class="new" title="User:G4oep (page does not exist)">G4oep</a> (<a href="/wiki/User_talk:G4oep" title="User talk:G4oep">talk</a> • <a href="/wiki/Special:Contributions/G4oep" title="Special:Contributions/G4oep">contribs</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-G4oep-2010-10-15T17:50:00.000Z-Units_!!!!" class="ext-discussiontools-init-timestamplink">17:50, 15 October 2010 (UTC)</a></span></small><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-G4oep-2010-10-15T17:50:00.000Z-Units_!!!!"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-G4oep-2010-10-15T17:50:00.000Z-Units_!!!!"></span> </p> <ul><li><span data-mw-comment-start="" id="c-Msaunier-2012-02-20T19:51:00.000Z-G4oep-2010-10-15T17:50:00.000Z"></span>Calm down, but I do agree; the metric world has more-or-less turned to SI units, but inHg is still used in the US, especially in aviation. Perhaps mmHg should be changed to inHg? <a href="/wiki/User:Msaunier" title="User:Msaunier">Msaunier</a> (<a href="/wiki/User_talk:Msaunier" title="User talk:Msaunier">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Msaunier-2012-02-20T19:51:00.000Z-G4oep-2010-10-15T17:50:00.000Z" class="ext-discussiontools-init-timestamplink">19:51, 20 February 2012 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Msaunier-2012-02-20T19:51:00.000Z-G4oep-2010-10-15T17:50:00.000Z"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Msaunier-2012-02-20T19:51:00.000Z-G4oep-2010-10-15T17:50:00.000Z"></span></li> <li>All that needs to happen is to add additional columns for SI units - and might as well include Imperial units and °F as well. Much of the work done in the U.S.A. is still in °F and psi. For instance public water utilities are interested in the vapor pressure of water for several types of engineering analyses.</li></ul> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Categorization" data-mw-thread-id="h-Categorization-2007-03-12T14:43:00.000Z"><span data-mw-comment-start="" id="h-Categorization-2007-03-12T14:43:00.000Z"></span>Categorization<span data-mw-comment-end="h-Categorization-2007-03-12T14:43:00.000Z"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Talk:Vapour_pressure_of_water&action=edit&section=4" title="Edit section: Categorization"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span><div class="ext-discussiontools-init-section-bar"><div class="ext-discussiontools-init-section-metadata"></div><div class="ext-discussiontools-init-section-actions"></div></div></div> <p><span data-mw-comment-start="" id="c-Philip_Trueman-2007-03-12T14:43:00.000Z-Categorization"></span>Why is this categorized under "Chemical properties". I don't see any chemistry here. Shouldn't this rather be in a subcategory of "Physics", say "Thermodynamics"? <a href="/wiki/User:Philip_Trueman" title="User:Philip Trueman">Philip Trueman</a> <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Philip_Trueman-2007-03-12T14:43:00.000Z-Categorization" class="ext-discussiontools-init-timestamplink">14:43, 12 March 2007 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Philip_Trueman-2007-03-12T14:43:00.000Z-Categorization"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Philip_Trueman-2007-03-12T14:43:00.000Z-Categorization"></span> </p> <dl><dd><span data-mw-comment-start="" id="c-Pbisson-2007-10-09T02:45:00.000Z-Philip_Trueman-2007-03-12T14:43:00.000Z"></span>Philip, you raise a good point. It would seem that such a thing might be better categorized under physics or thermodynamics. However, the vapor pressure of water, and partial pressures of gases in general, has long been a topic of physical chemistry. So, I'd say it's properly categorized. For example, the combined gas law (PV=nRT) comes from chemistry, not physics. The vapor pressure of water at various temperatures is frequently used in chemistry when performing gas-phase chemical reactions.</dd></dl> <dl><dd>But, what bothers me about this entry is that there is not a single reference to an acceptable scientific source for the numbers. Sure, there is a reference to a High School text book. Also, the table seems a bit incomplete. One would like the similar numbers in different units, say mmHg (ie: Torr), atm. Both these units are more common in the chemistry laboratory than are Pascal (which are more likely used in a physics lab).</dd></dl> <dl><dd>I'd like to see external references to other sources of physical chemistry, like a textbook (e.g.: any of Atkins' books on physical chemistry), a good reference manual (e.g.: CRC Handbook of Chemistry and Physics), and a scientific paper from a refereed journal (e.g.: something relevant from J. Phys. Chem.) Such referencing can buttruss the information in such a scientific entry and help to dispell the notion that Wikipedia is not a reference to be used for "scientific" information. <a href="/wiki/User:Pbisson" title="User:Pbisson">Patrick</a> <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Pbisson-2007-10-09T02:45:00.000Z-Philip_Trueman-2007-03-12T14:43:00.000Z" class="ext-discussiontools-init-timestamplink">02:45, 9 October 2007 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Pbisson-2007-10-09T02:45:00.000Z-Philip_Trueman-2007-03-12T14:43:00.000Z"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Pbisson-2007-10-09T02:45:00.000Z-Philip_Trueman-2007-03-12T14:43:00.000Z"></span></dd></dl> <dl><dd><dl><dd><span data-mw-comment-start="" id="c-83.92.159.225-2010-12-06T00:02:00.000Z-Pbisson-2007-10-09T02:45:00.000Z"></span>This is just wrong. Water has many chemical properties, but the vapour pressure is a thermodynamic property. Sure it is often used in chemistry - so is it's mass. Anyway, the category "Thermodynamic properties", is a subcategory of both "Thermodynamics" and "Chemical properties" (the current category), and must be correct for this article.</dd> <dd>Btw: Using mmHg instead of SI-units, in an article like this, seems contrary to Wiki-guidelines, unless the article was i.e. "vapour pressure of water in chemistry", and someone could document, that the usual unit of preference in that sector was mmHg. However I'm not a w-lawyer, and so I'll leave it to someone else to judge and correct that. <a href="/wiki/Special:Contributions/83.92.159.225" title="Special:Contributions/83.92.159.225">83.92.159.225</a> (<a href="/w/index.php?title=User_talk:83.92.159.225&action=edit&redlink=1" class="new" title="User talk:83.92.159.225 (page does not exist)">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-83.92.159.225-2010-12-06T00:02:00.000Z-Pbisson-2007-10-09T02:45:00.000Z" class="ext-discussiontools-init-timestamplink">00:02, 6 December 2010 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-83.92.159.225-2010-12-06T00:02:00.000Z-Pbisson-2007-10-09T02:45:00.000Z"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-83.92.159.225-2010-12-06T00:02:00.000Z-Pbisson-2007-10-09T02:45:00.000Z"></span></dd></dl></dd></dl> <p><br/><span data-mw-comment-start="" id="c-123.3.79.202-2010-05-04T15:06:00.000Z-Categorization"></span> I love the first sentence: 'The vapour pressure of water is the vapour pressure of water'. God job buddy. <span style="font-size: smaller;" class="autosigned">—Preceding <a href="/wiki/Wikipedia:Signatures" title="Wikipedia:Signatures">unsigned</a> comment added by <a href="/wiki/Special:Contributions/123.3.79.202" title="Special:Contributions/123.3.79.202">123.3.79.202</a> (<a href="/w/index.php?title=User_talk:123.3.79.202&action=edit&redlink=1" class="new" title="User talk:123.3.79.202 (page does not exist)">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-123.3.79.202-2010-05-04T15:06:00.000Z-Categorization" class="ext-discussiontools-init-timestamplink">15:06, 4 May 2010 (UTC)</a></span><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-123.3.79.202-2010-05-04T15:06:00.000Z-Categorization"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-123.3.79.202-2010-05-04T15:06:00.000Z-Categorization"></span> </p><p><br/> </p> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Accuracy?" data-mw-thread-id="h-Accuracy?-2016-11-26T16:51:00.000Z"><span id="Accuracy.3F"></span><span data-mw-comment-start="" id="h-Accuracy?-2016-11-26T16:51:00.000Z"></span>Accuracy?<span data-mw-comment-end="h-Accuracy?-2016-11-26T16:51:00.000Z"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Talk:Vapour_pressure_of_water&action=edit&section=5" title="Edit section: Accuracy?"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span><div class="ext-discussiontools-init-section-bar"><div class="ext-discussiontools-init-section-metadata"></div><div class="ext-discussiontools-init-section-actions"></div></div></div> <p><a href="/w/index.php?title=User:Dtprice&action=edit&redlink=1" class="new" title="User:Dtprice (page does not exist)"><span data-mw-comment-start="" id="c-Dtprice-2016-11-26T16:51:00.000Z-Accuracy?"></span>Dtprice</a> (<a href="/wiki/User_talk:Dtprice" title="User talk:Dtprice">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Dtprice-2016-11-26T16:51:00.000Z-Accuracy?" class="ext-discussiontools-init-timestamplink">16:51, 26 November 2016 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Dtprice-2016-11-26T16:51:00.000Z-Accuracy?"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Dtprice-2016-11-26T16:51:00.000Z-Accuracy?"></span> </p><p><span data-mw-comment-start="" id="c-TimeHorse-20221018184000-Accuracy?"></span>I came to this page to find a decent approximation formula, being too lazy to look it up in a book. But after I tried both formulae I was concerned (not to say surprised) that neither of them gives an accurate calculation of saturation vapo(u)r pressure (<span class="texhtml mvar" style="font-style:italic;">P</span>) at 0 °C!!! </p><p>The table shows a value of 0.6113 kPa at °C, which seems to be commonly agreed. The first formulation (least accurate and unattributed) gives me 0.6593 kPa! Antoine's formula gives me 0.6056 kPa. I then went to one of my reliable sources: Monteith and Unsworth (2008)<sup id="cite_ref-Monteith2008_1-0" class="reference"><a href="#cite_note-Monteith2008-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>. P. 13 provides Tetens' formula<sup id="cite_ref-Tetens1930_2-0" class="reference"><a href="#cite_note-Tetens1930-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> (published in 1930!) for temperatures above 0 °C, but cites Murray (1967)<sup id="cite_ref-Murray1967_3-0" class="reference"><a href="#cite_note-Murray1967-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>: </p> <dl><dd><dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P=0.61078\exp \left({\frac {17.27T}{T+237.3}}\right),}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>P</mi> <mo>=</mo> <mn>0.61078</mn> <mi>exp</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>17.27</mn> <mi>T</mi> </mrow> <mrow> <mi>T</mi> <mo>+</mo> <mn>237.3</mn> </mrow> </mfrac> </mrow> <mo>)</mo> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle P=0.61078\exp \left({\frac {17.27T}{T+237.3}}\right),}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/83bf9a3c78053dbd7eef7366e19decdcd0da5396" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:31.082ex; height:6.176ex;" alt="{\displaystyle P=0.61078\exp \left({\frac {17.27T}{T+237.3}}\right),}"/></span></dd></dl></dd></dl> <p>where temperature <span class="texhtml mvar" style="font-style:italic;">T</span> is in <a href="/wiki/Celsius" title="Celsius">degrees Celsius</a> (°C) and saturation vapor pressure <span class="texhtml mvar" style="font-style:italic;">P</span> is in <a href="/wiki/Kilopascal" class="mw-redirect" title="Kilopascal">kilopascals</a> (kPa) [NOTE: I have simplified the published equation slightly to make it easier to code.] According to Monteith and Unsworth, "<i>Values of saturation vapour pressure from Tetens' formula are within 1 Pa of exact values up to 35 °C.</i>" </p><p>Murray also provides Tetens' equation for temperatures below 0 °C [again I have simplified slightly]: </p> <dl><dd><dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P=0.61078\exp \left({\frac {21.875T}{T+265.5}}\right).}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>P</mi> <mo>=</mo> <mn>0.61078</mn> <mi>exp</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>21.875</mn> <mi>T</mi> </mrow> <mrow> <mi>T</mi> <mo>+</mo> <mn>265.5</mn> </mrow> </mfrac> </mrow> <mo>)</mo> </mrow> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle P=0.61078\exp \left({\frac {21.875T}{T+265.5}}\right).}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/15b9bb23e30f6a3571c728b934d11081152afd51" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:31.082ex; height:6.176ex;" alt="{\displaystyle P=0.61078\exp \left({\frac {21.875T}{T+265.5}}\right).}"/></span></dd></dl></dd></dl> <p>I also investigated the <a href="/wiki/Arden_Buck_equation" title="Arden Buck equation">Buck</a> formulation. This is rather more complicated than Tetens, but much more accurate, and reportedly superior to the <a href="/wiki/Goff%E2%80%93Gratch_equation" title="Goff–Gratch equation">Goff-Gratch equation</a>. Pursuing this further, I calculated values at six temperatures and their % error from the table values (which I am assuming are accurate, given the source is cited as <sup id="cite_ref-Lide2005_4-0" class="reference"><a href="#cite_note-Lide2005-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>). I get the following results: </p> <dl><dd><table class="wikitable"> <tbody><tr align="center"> <th><span class="texhtml mvar" style="font-style:italic;">T</span> (°C)</th> <th><span class="texhtml mvar" style="font-style:italic;">P</span> (Table)</th> <th><span class="texhtml mvar" style="font-style:italic;">P</span> (Eq 1)</th> <th><span class="texhtml mvar" style="font-style:italic;">P</span> (Antoine)</th> <th><span class="texhtml mvar" style="font-style:italic;">P</span> (Tetens)</th> <th><span class="texhtml mvar" style="font-style:italic;">P</span> (Buck) </th></tr> <tr align="center"> <td>0</td> <td>0.6113</td> <td>0.6593 (+7.85%)</td> <td>0.6056 (-0.93%)</td> <td>0.6108 (-0.09%)</td> <td>0.6112 (-0.01%) </td></tr> <tr align="center"> <td>20</td> <td>2.3388</td> <td>2.3755 (+1.57%)</td> <td>2.3296 (-0.39%)</td> <td>2.3399 (+0.05%)</td> <td>2.3383 (-0.02%) </td></tr> <tr align="center"> <td>35</td> <td>5.6267</td> <td>5.5696 (-1.01%)</td> <td>5.6090 (-0.31%)</td> <td>5.6289 (+0.04%)</td> <td>5.6268 (+0.00%) </td></tr> <tr align="center"> <td>50</td> <td>12.344</td> <td>12.065 (-2.26%)</td> <td>12.306 (-0.31%)</td> <td>12.354 (+0.08%)</td> <td>12.349 (+0.04%) </td></tr> <tr align="center"> <td>75</td> <td>38.563</td> <td>37.738 (-2.14%)</td> <td>38.463 (-0.26%)</td> <td>38.718 (+0.40%)</td> <td>38.595 (+0.08%) </td></tr> <tr align="center"> <td>100</td> <td>101.32</td> <td>101.31 (-0.01%)</td> <td>101.34 (+0.02%)</td> <td>102.43 (+1.10%)</td> <td>101.31 (-0.01%) </td></tr></tbody></table></dd></dl> <p>So the simple formulas presented in the wikipedia article are reasonably accurate at 100 °C, but quite poor for most of the temperature range below boiling point. Tetens<sup id="cite_ref-Tetens1930_2-1" class="reference"><a href="#cite_note-Tetens1930-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>, as reported by Murray<sup id="cite_ref-Murray1967_3-1" class="reference"><a href="#cite_note-Murray1967-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> and Monteith and Unsworth<sup id="cite_ref-Monteith2008_1-1" class="reference"><a href="#cite_note-Monteith2008-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>, beats both the empirical equations presented in the wikipedia article over the range from 0 to 50 °C (and I'd guess, probably for some way above 50 °C as well), but Antoine's is superior at 75 °C and above. The unattributed formula must have zero error at around 26 °C, but is of very poor accuracy outside a very narrow range. Tetens' equations are generally much more accurate and arguably simpler for use at everyday temperatures (e.g., in meteorology). However, I don't have reliable information on the performance of Tetens' equation for <span class="texhtml mvar" style="font-style:italic;">T</span> < 0 °C. As expected, Buck's equation for <span class="texhtml mvar" style="font-style:italic;">T</span> > 0 °C is significantly more accurate than Tetens, and its superiority increases markedly above 50 °C, though it is more complicated to use. For completeness, here are Buck's (1981)<sup id="cite_ref-Buck1981_5-0" class="reference"><a href="#cite_note-Buck1981-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> equations for <span class="texhtml mvar" style="font-style:italic;">P</span>(<span class="texhtml mvar" style="font-style:italic;">T</span>) for <span class="texhtml mvar" style="font-style:italic;">T</span> both above and below freezing: </p><p><br/> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P=0.61121\exp \left(\left(18.678-{\frac {T}{234.5}}\right)\left({\frac {T}{257.14+T}}\right)\right)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>P</mi> <mo>=</mo> <mn>0.61121</mn> <mi>exp</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mrow> <mo>(</mo> <mrow> <mn>18.678</mn> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>T</mi> <mn>234.5</mn> </mfrac> </mrow> </mrow> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>T</mi> <mrow> <mn>257.14</mn> <mo>+</mo> <mi>T</mi> </mrow> </mfrac> </mrow> <mo>)</mo> </mrow> </mrow> <mo>)</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle P=0.61121\exp \left(\left(18.678-{\frac {T}{234.5}}\right)\left({\frac {T}{257.14+T}}\right)\right)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/305bc1d601a4199e351394afd746d06ebc52ff52" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:54.26ex; height:6.176ex;" alt="{\displaystyle P=0.61121\exp \left(\left(18.678-{\frac {T}{234.5}}\right)\left({\frac {T}{257.14+T}}\right)\right)}"/></span>, over liquid water, <span class="texhtml mvar" style="font-style:italic;">T</span> > 0 °C</dd></dl> <p><br/> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P=0.61115\exp \left(\left(23.036-{\frac {T}{333.7}}\right)\left({\frac {T}{279.82+T}}\right)\right)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>P</mi> <mo>=</mo> <mn>0.61115</mn> <mi>exp</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mrow> <mo>(</mo> <mrow> <mn>23.036</mn> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>T</mi> <mn>333.7</mn> </mfrac> </mrow> </mrow> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>T</mi> <mrow> <mn>279.82</mn> <mo>+</mo> <mi>T</mi> </mrow> </mfrac> </mrow> <mo>)</mo> </mrow> </mrow> <mo>)</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle P=0.61115\exp \left(\left(23.036-{\frac {T}{333.7}}\right)\left({\frac {T}{279.82+T}}\right)\right)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/dd0f780edee2bffd6ba909abb5d7cfbf11d1d061" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:54.26ex; height:6.176ex;" alt="{\displaystyle P=0.61115\exp \left(\left(23.036-{\frac {T}{333.7}}\right)\left({\frac {T}{279.82+T}}\right)\right)}"/></span>, over ice, <span class="texhtml mvar" style="font-style:italic;">T</span> < 0 °C</dd></dl> <p><br/> For serious computation, my preferred formulation has been Lowe (1977)<sup id="cite_ref-Lowe1977_6-0" class="reference"><a href="#cite_note-Lowe1977-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>. Lowe developed two pairs of equations for temperatures above and below freezing, with different levels of accuracy. They are all very accurate (compared to <a href="/wiki/Clausius%E2%80%93Clapeyron_relation" title="Clausius–Clapeyron relation">Clausius-Clapeyron</a> and the <a href="/wiki/Goff%E2%80%93Gratch_equation" title="Goff–Gratch equation">Goff-Gratch</a>) but use nested polynomials for very efficient computation. However, there are more recent reviews of possibly superior formulations, notably Wexler (1976, 1977)<sup id="cite_ref-Wexler1976_7-0" class="reference"><a href="#cite_note-Wexler1976-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Wexler1977_8-0" class="reference"><a href="#cite_note-Wexler1977-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>, reported by Flatau et al. (1992)<sup id="cite_ref-Flatau1992_9-0" class="reference"><a href="#cite_note-Flatau1992-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup>. </p> <hr/> <p>You say Goff-Gratch is less accurate than Buck but you fail to present the corrected numbers for this equation. The numbers quoted in the article are incorrect according to my verified calculations using the Goff-Gratch. Specifically, I've calculated: </p> <table class="wikitable"> <caption>Table of Buck vs. Goff-Gratch values at 5 Centigrade-Degree intervals </caption> <tbody><tr> <th>Temperature (℃)</th> <th>Measured (kPa)</th> <th>Goff-Gratch (kPa)</th> <th>Buck (kPa)</th> <th>Goff-Gratch offset (kPa)</th> <th>Buck offset (kPa) </th></tr> <tr> <td>0</td> <td>0.6113</td> <td>0.6107</td> <td>0.6112</td> <td>-0.0008</td> <td>-0.0001 </td></tr> <tr> <td>5</td> <td>0.8726</td> <td>0.8718</td> <td>0.8724</td> <td>-0.0008</td> <td>-0.0002 </td></tr> <tr> <td>10</td> <td>1.2281</td> <td>1.2270</td> <td>1.2279</td> <td>-0.0011</td> <td>-0.0002 </td></tr> <tr> <td>15</td> <td>1.7056</td> <td>1.7041</td> <td>1.7052</td> <td>-0.0015</td> <td>-0.0004 </td></tr> <tr> <td>20</td> <td>2.3388</td> <td>2.3370</td> <td>2.3383</td> <td>-0.0018</td> <td>-0.0005 </td></tr> <tr> <td>25</td> <td>3.1690</td> <td>3.1667</td> <td>3.1685</td> <td>-0.0023</td> <td>-0.0005 </td></tr> <tr> <td>30</td> <td>4.2455</td> <td>4.2426</td> <td>4.2451</td> <td>-0.0029</td> <td>-0.0004 </td></tr> <tr> <td>35</td> <td>5.6267</td> <td>5.6231</td> <td>5.6268</td> <td>-0.0036</td> <td>+0.0001 </td></tr> <tr> <td>40</td> <td>7.3814</td> <td>7.3771</td> <td>7.3824</td> <td>-0.0043</td> <td>+0.0010 </td></tr> <tr> <td>45</td> <td>9.5898</td> <td>9.5848</td> <td>9.5923</td> <td>-0.0050</td> <td>+0.0025 </td></tr> <tr> <td>50</td> <td>12.3440</td> <td>12.3387</td> <td>12.3494</td> <td>-0.0053</td> <td>+0.0054 </td></tr> <tr> <td>55</td> <td>15.7520</td> <td>15.7452</td> <td>15.7600</td> <td>-0.0068</td> <td>+0.0080 </td></tr> <tr> <td>60</td> <td>19.9320</td> <td>19.9251</td> <td>19.9451</td> <td>-0.0069</td> <td>+0.0131 </td></tr> <tr> <td>65</td> <td>25.0220</td> <td>25.0149</td> <td>25.0412</td> <td>-0.0071</td> <td>+0.0192 </td></tr> <tr> <td>70</td> <td>31.1760</td> <td>31.1680</td> <td>31.2010</td> <td>-0.0080</td> <td>+0.0250 </td></tr> <tr> <td>75</td> <td>38.5630</td> <td>38.5551</td> <td>38.5947</td> <td>-0.0079</td> <td>+0.0317 </td></tr> <tr> <td>80</td> <td>47.3730</td> <td>47.3657</td> <td>47.4103</td> <td>-0.0073</td> <td>+0.0373 </td></tr> <tr> <td>85</td> <td>57.8150</td> <td>57.8086</td> <td>57.8543</td> <td>-0.0064</td> <td>+0.0393 </td></tr> <tr> <td>90</td> <td>70.1170</td> <td>70.1127</td> <td>70.1521</td> <td>-0.0043</td> <td>+0.0351 </td></tr> <tr> <td>95</td> <td>84.5290</td> <td>84.5278</td> <td>84.5486</td> <td>-0.0012</td> <td>+0.0196 </td></tr> <tr> <td>100</td> <td>101.3200</td> <td>101.3250</td> <td>101.3078</td> <td>+0.0050</td> <td>-0.0122 </td></tr></tbody></table> <p>Basically, yes, Buck is better lower than 50℃ but above that Goff-Gratch does much better. However, for most uses of the formula, such as humidity calculations, temperatures less than 50℃ are much more common than above so Buck probably is better for most applications. However, it would be useful to consider sub-0 vapour pressures to get the full picture. </p><p><a href="/wiki/User:TimeHorse" title="User:TimeHorse">TimeHorse</a> (<a href="/wiki/User_talk:TimeHorse" title="User talk:TimeHorse">talk</a>) <a href="/wiki/User:TimeHorse" title="User:TimeHorse">TimeHorse</a> (<a href="/wiki/User_talk:TimeHorse" title="User talk:TimeHorse">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-TimeHorse-20221018184000-Accuracy?" class="ext-discussiontools-init-timestamplink">18:40, 18 October 2022 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-TimeHorse-20221018184000-Accuracy?"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-TimeHorse-20221018184000-Accuracy?"></span> </p> <hr/> <p><span data-mw-comment-start="" id="c-TimeHorse-20221019192000-Accuracy?"></span>I looked up the Vapour Pressure of Ice<sup id="cite_ref-vpicebiopharma_10-0" class="reference"><a href="#cite_note-vpicebiopharma-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> I calculated the vapour pressure below 0℃ using both the above Buck algorithm for below freezing and the Goff-Gratch algorithm below freezing. Analyzing these results, I found Goff-Gratch to be the more accurate from 0℃ to -100℃, though they are close from -50℃ to 0℃ which again are common temperatures meteorologically. </p><p>Specifically: </p> <table class="wikitable"> <caption>Table of Buck vs. Goff-Gratch values for ice vapour pressure </caption> <tbody><tr> <th>Temperature (℃)</th> <th>Measured (Pa)</th> <th>Goff-Gratch (Pa)</th> <th>Buck (Pa)</th> <th>Goff-Gratch offset (Pa)</th> <th>Buck offset (Pa) </th></tr> <tr> <td>0</td> <td>610.8</td> <td>611.2</td> <td>611.1</td> <td>+0.4</td> <td>+0.4 </td></tr> <tr> <td>-1</td> <td>562.3</td> <td>562.7</td> <td>562.7</td> <td>+0.4</td> <td>+0.4 </td></tr> <tr> <td>-2</td> <td>517.3</td> <td>517.8</td> <td>517.7</td> <td>+0.5</td> <td>+0.4 </td></tr> <tr> <td>-3</td> <td>475.7</td> <td>476.1</td> <td>476.1</td> <td>+0.4</td> <td>+0.4 </td></tr> <tr> <td>-4</td> <td>437.2</td> <td>437.5</td> <td>437.5</td> <td>+0.3</td> <td>+0.3 </td></tr> <tr> <td>-5</td> <td>401.5</td> <td>401.8</td> <td>401.8</td> <td>+0.3</td> <td>+0.3 </td></tr> <tr> <td>-6</td> <td>368.5</td> <td>368.8</td> <td>368.8</td> <td>+0.3</td> <td>+0.3 </td></tr> <tr> <td>-7</td> <td>337.9</td> <td>338.2</td> <td>338.2</td> <td>+0.3</td> <td>+0.3 </td></tr> <tr> <td>-8</td> <td>309.7</td> <td>310.0</td> <td>310.0</td> <td>+0.3</td> <td>+0.3 </td></tr> <tr> <td>-9</td> <td>283.7</td> <td>283.9</td> <td>284.0</td> <td>+0.2</td> <td>+0.3 </td></tr> <tr> <td>-10</td> <td>259.7</td> <td>259.9</td> <td>259.9</td> <td>+0.2</td> <td>+0.2 </td></tr> <tr> <td>-15</td> <td>165.2</td> <td>165.3</td> <td>165.3</td> <td>+0.1</td> <td>+0.1 </td></tr> <tr> <td>-20</td> <td>103.2</td> <td>103.2</td> <td>103.3</td> <td>+0.0</td> <td>+0.1 </td></tr> <tr> <td>-25</td> <td>63.23</td> <td>63.28</td> <td>63.31</td> <td>+0.05</td> <td>+0.08 </td></tr> <tr> <td>-30</td> <td>37.98</td> <td>38.00</td> <td>38.02</td> <td>+0.02</td> <td>+0.04 </td></tr> <tr> <td>-35</td> <td>22.33</td> <td>22.34</td> <td>22.36</td> <td>+0.01</td> <td>+0.03 </td></tr> <tr> <td>-40</td> <td>12.83</td> <td>12.84</td> <td>12.85</td> <td>+0.01</td> <td>+0.02 </td></tr> <tr> <td>-45</td> <td>7.198</td> <td>7.202</td> <td>7.206</td> <td>+0.004</td> <td>+0.008 </td></tr> <tr> <td>-50</td> <td>3.935</td> <td>3.936</td> <td>3.939</td> <td>+0.001</td> <td>+0.004 </td></tr> <tr> <td>-55</td> <td>2.092</td> <td>2.093</td> <td>2.095</td> <td>+0.001</td> <td>+0.003 </td></tr> <tr> <td>-60</td> <td>1.080</td> <td>1.081</td> <td>1.082</td> <td>+0.001</td> <td>+0.002 </td></tr> <tr> <td>-65</td> <td>0.5406</td> <td>0.5407</td> <td>0.5413</td> <td>+0.0001</td> <td>+0.0007 </td></tr> <tr> <td>-70</td> <td>0.2615</td> <td>0.2615</td> <td>0.2619</td> <td>+0.0000</td> <td>+0.0004 </td></tr> <tr> <td>-80</td> <td>0.05470</td> <td>0.05472</td> <td>0.05484</td> <td>+0.00002</td> <td>+0.00014 </td></tr> <tr> <td>-90</td> <td>0.009670</td> <td>0.009670</td> <td>0.009709</td> <td>+0.000000</td> <td>+0.000039 </td></tr> <tr> <td>-100</td> <td>0.001400</td> <td>0.001403</td> <td>0.001413</td> <td>+0.000003</td> <td>+0.000013 </td></tr></tbody></table> <p>Also, I wanted to show the Python code I used to calculate these values; code uses the <a rel="nofollow" class="external text" href="https://pint.readthedocs.io/en/stable/">Pint</a> library to ensure dimensionality: </p> <div class="mw-highlight mw-highlight-lang-python mw-content-ltr" dir="ltr"><pre><span></span><span class="kn">from</span> <span class="nn">pint</span> <span class="kn">import</span> <span class="n">UnitRegistry</span> <span class="n">ureg</span> <span class="o">=</span> <span class="n">UnitRegistry</span><span class="p">()</span> <span class="n">_Q</span> <span class="o">=</span> <span class="n">ureg</span><span class="o">.</span><span class="n">Quantity</span> <span class="n">T100C</span> <span class="o">=</span> <span class="n">_Q</span><span class="p">(</span><span class="mi">100</span><span class="p">,</span> <span class="n">ureg</span><span class="o">.</span><span class="n">degC</span><span class="p">)</span> <span class="n">TTPC</span> <span class="o">=</span> <span class="mf">273.16</span> <span class="o">*</span> <span class="n">ureg</span><span class="o">.</span><span class="n">K</span> <span class="n">atm</span> <span class="o">=</span> <span class="n">_Q</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">ureg</span><span class="o">.</span><span class="n">atm</span><span class="p">)</span> <span class="k">def</span> <span class="nf">get_vapour_pressure_water_goff_gratch</span><span class="p">(</span><span class="n">T</span><span class="p">):</span> <span class="n">K</span> <span class="o">=</span> <span class="n">ureg</span><span class="o">.</span><span class="n">K</span> <span class="n">Tst</span> <span class="o">=</span> <span class="n">T100C</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">K</span><span class="p">)</span><span class="o">.</span><span class="n">magnitude</span> <span class="n">TK</span> <span class="o">=</span> <span class="n">T</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">K</span><span class="p">)</span><span class="o">.</span><span class="n">magnitude</span> <span class="n">esst</span> <span class="o">=</span> <span class="n">atm</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">ureg</span><span class="o">.</span><span class="n">hPa</span><span class="p">)</span> <span class="k">return</span> <span class="p">(</span><span class="mi">10</span><span class="o">**</span><span class="p">(</span><span class="o">-</span><span class="mf">7.90298</span><span class="o">*</span><span class="p">(</span><span class="n">Tst</span><span class="o">/</span><span class="n">TK</span><span class="o">-</span><span class="mi">1</span><span class="p">))</span> <span class="o">*</span> <span class="p">(</span><span class="n">Tst</span><span class="o">/</span><span class="n">TK</span><span class="p">)</span><span class="o">**</span><span class="mf">5.02808</span> <span class="o">/</span> \ <span class="mi">10</span><span class="o">**</span><span class="p">(</span><span class="mf">1.3816e-7</span><span class="o">*</span><span class="p">(</span><span class="mi">10</span><span class="o">**</span><span class="p">(</span><span class="mf">11.344</span><span class="o">*</span><span class="p">(</span><span class="mi">1</span><span class="o">-</span><span class="n">TK</span><span class="o">/</span><span class="n">Tst</span><span class="p">))</span> <span class="o">-</span> <span class="mi">1</span><span class="p">))</span> <span class="o">*</span> \ <span class="mi">10</span><span class="o">**</span><span class="p">(</span><span class="mf">8.1328e-3</span><span class="o">*</span><span class="p">(</span><span class="mi">10</span><span class="o">**</span><span class="p">(</span><span class="o">-</span><span class="mf">3.49149</span><span class="o">*</span><span class="p">(</span><span class="n">Tst</span><span class="o">/</span><span class="n">TK</span> <span class="o">-</span> <span class="mi">1</span><span class="p">))</span> <span class="o">-</span> <span class="mi">1</span><span class="p">))</span> <span class="o">*</span> \ <span class="n">esst</span><span class="p">)</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">ureg</span><span class="o">.</span><span class="n">kPa</span><span class="p">)</span> <span class="k">def</span> <span class="nf">get_vapour_pressure_water_buck</span><span class="p">(</span><span class="n">T</span><span class="p">):</span> <span class="n">TC</span> <span class="o">=</span> <span class="n">T</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">ureg</span><span class="o">.</span><span class="n">degC</span><span class="p">)</span><span class="o">.</span><span class="n">magnitude</span> <span class="k">return</span> <span class="mf">0.61121</span><span class="o">*</span><span class="n">np</span><span class="o">.</span><span class="n">exp</span><span class="p">((</span><span class="mf">18.678</span><span class="o">-</span><span class="n">TC</span><span class="o">/</span><span class="mf">234.5</span><span class="p">)</span> <span class="o">*</span> <span class="n">TC</span> <span class="o">/</span> <span class="p">(</span><span class="mf">257.14</span> <span class="o">+</span> <span class="n">TC</span><span class="p">))</span> <span class="o">*</span> \ <span class="n">ureg</span><span class="o">.</span><span class="n">kPa</span> <span class="k">def</span> <span class="nf">get_vapour_pressure_ice_goff_gratch</span><span class="p">(</span><span class="n">T</span><span class="p">):</span> <span class="n">K</span> <span class="o">=</span> <span class="n">ureg</span><span class="o">.</span><span class="n">K</span> <span class="n">T0</span> <span class="o">=</span> <span class="n">TTPC</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">K</span><span class="p">)</span><span class="o">.</span><span class="n">magnitude</span> <span class="n">TK</span> <span class="o">=</span> <span class="n">T</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">K</span><span class="p">)</span><span class="o">.</span><span class="n">magnitude</span> <span class="n">esi0</span> <span class="o">=</span> <span class="mf">6.1173</span> <span class="o">*</span> <span class="n">ureg</span><span class="o">.</span><span class="n">hPa</span> <span class="k">return</span> <span class="p">(</span><span class="mi">10</span><span class="o">**</span><span class="p">(</span><span class="o">-</span><span class="mf">9.09718</span><span class="o">*</span><span class="p">(</span><span class="n">T0</span><span class="o">/</span><span class="n">TK</span><span class="o">-</span><span class="mi">1</span><span class="p">))</span> <span class="o">/</span> <span class="p">(</span><span class="n">T0</span><span class="o">/</span><span class="n">TK</span><span class="p">)</span><span class="o">**</span><span class="mf">3.56654</span> <span class="o">*</span> \ <span class="mi">10</span><span class="o">**</span><span class="p">(</span><span class="mf">0.876793</span><span class="o">*</span><span class="p">(</span><span class="mi">1</span><span class="o">-</span><span class="n">TK</span><span class="o">/</span><span class="n">T0</span><span class="p">))</span> <span class="o">*</span> <span class="n">esi0</span><span class="p">)</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">ureg</span><span class="o">.</span><span class="n">Pa</span><span class="p">)</span> <span class="k">def</span> <span class="nf">get_vapour_pressure_ice_buck</span><span class="p">(</span><span class="n">T</span><span class="p">):</span> <span class="n">TC</span> <span class="o">=</span> <span class="n">T</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">ureg</span><span class="o">.</span><span class="n">degC</span><span class="p">)</span><span class="o">.</span><span class="n">magnitude</span> <span class="k">return</span> <span class="mf">0.61115</span><span class="o">*</span><span class="n">np</span><span class="o">.</span><span class="n">exp</span><span class="p">((</span><span class="mf">23.036</span><span class="o">-</span><span class="n">TC</span><span class="o">/</span><span class="mf">333.7</span><span class="p">)</span> <span class="o">*</span> <span class="n">TC</span> <span class="o">/</span> <span class="p">(</span><span class="mf">279.82</span> <span class="o">+</span> <span class="n">TC</span><span class="p">))</span> <span class="o">*</span> \ <span class="n">ureg</span><span class="o">.</span><span class="n">Pa</span> </pre></div> <p><a href="/wiki/User:TimeHorse" title="User:TimeHorse">TimeHorse</a> (<a href="/wiki/User_talk:TimeHorse" title="User talk:TimeHorse">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-TimeHorse-20221019192000-Accuracy?" class="ext-discussiontools-init-timestamplink">19:20, 19 October 2022 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-TimeHorse-20221019192000-Accuracy?"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-TimeHorse-20221019192000-Accuracy?"></span> </p> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="Vapor_pressure_graph_appears_to_be_labeled_wrong" data-mw-thread-id="h-Vapor_pressure_graph_appears_to_be_labeled_wrong-2022-02-11T05:08:00.000Z"><span data-mw-comment-start="" id="h-Vapor_pressure_graph_appears_to_be_labeled_wrong-2022-02-11T05:08:00.000Z"></span>Vapor pressure graph appears to be labeled wrong<span data-mw-comment-end="h-Vapor_pressure_graph_appears_to_be_labeled_wrong-2022-02-11T05:08:00.000Z"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Talk:Vapour_pressure_of_water&action=edit&section=6" title="Edit section: Vapor pressure graph appears to be labeled wrong"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span><div class="ext-discussiontools-init-section-bar"><div class="ext-discussiontools-init-section-metadata"></div><div class="ext-discussiontools-init-section-actions"></div></div></div> <p><span data-mw-comment-start="" id="c-71.45.76.116-2022-02-11T05:08:00.000Z-Vapor_pressure_graph_appears_to_be_labeled_wrong"></span>This logarithmic graph: <a class="external free" href="https://en.wikipedia.org/wiki/Vapour_pressure_of_water#/media/File:Vapor_Pressure_of_Water.png">https://en.wikipedia.org/wiki/Vapour_pressure_of_water#/media/File:Vapor_Pressure_of_Water.png</a> looks like the label for "Normal Boiling Point" is pointing to the incorrect log(pressure)/perk. Water normally boils at 373 K, so 1000/373 = 2.68, moreover, the vapor pressure would be 101 kPa, and the logarithm of that is ~2 (I can tell it's base ten because where the arrow's pointing bases 2 and e aren't anywhere close, being ~5.28 and ~11, respectively). The graph DOES intersect perk of 2.68 (mT)-1 and 2 log(kPa) exactly, which is where the "Normal Boiling Point" label should point. Someone should fix it but I won't do anything until I get consensus and I'm too busy to commit to fixing. <small class="autosigned">— Preceding <a href="/wiki/Wikipedia:Signatures" title="Wikipedia:Signatures">unsigned</a> comment added by <a href="/wiki/Special:Contributions/71.45.76.116" title="Special:Contributions/71.45.76.116">71.45.76.116</a> (<a href="/w/index.php?title=User_talk:71.45.76.116&action=edit&redlink=1" class="new" title="User talk:71.45.76.116 (page does not exist)">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-71.45.76.116-2022-02-11T05:08:00.000Z-Vapor_pressure_graph_appears_to_be_labeled_wrong" class="ext-discussiontools-init-timestamplink">05:08, 11 February 2022 (UTC)</a></small><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-71.45.76.116-2022-02-11T05:08:00.000Z-Vapor_pressure_graph_appears_to_be_labeled_wrong"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-71.45.76.116-2022-02-11T05:08:00.000Z-Vapor_pressure_graph_appears_to_be_labeled_wrong"></span> </p><p><span data-mw-comment-start="" id="c-71.45.76.116-2022-02-11T05:09:00.000Z-Vapor_pressure_graph_appears_to_be_labeled_wrong"></span>Actually I see that this issue has been raised farther up in the talk page over ten years ago lol. <small class="autosigned">— Preceding <a href="/wiki/Wikipedia:Signatures" title="Wikipedia:Signatures">unsigned</a> comment added by <a href="/wiki/Special:Contributions/71.45.76.116" title="Special:Contributions/71.45.76.116">71.45.76.116</a> (<a href="/w/index.php?title=User_talk:71.45.76.116&action=edit&redlink=1" class="new" title="User talk:71.45.76.116 (page does not exist)">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-71.45.76.116-2022-02-11T05:09:00.000Z-Vapor_pressure_graph_appears_to_be_labeled_wrong" class="ext-discussiontools-init-timestamplink">05:09, 11 February 2022 (UTC)</a></small><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-71.45.76.116-2022-02-11T05:09:00.000Z-Vapor_pressure_graph_appears_to_be_labeled_wrong"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-71.45.76.116-2022-02-11T05:09:00.000Z-Vapor_pressure_graph_appears_to_be_labeled_wrong"></span> </p> <div class="mw-heading mw-heading2 ext-discussiontools-init-section"><h2 id="References" data-mw-thread-id="h-References-2016-11-26T00:18:00.000Z"><span data-mw-comment-start="" id="h-References-2016-11-26T00:18:00.000Z"></span>References<span data-mw-comment-end="h-References-2016-11-26T00:18:00.000Z"></span></h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Talk:Vapour_pressure_of_water&action=edit&section=7" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span><div class="ext-discussiontools-init-section-bar"><div class="ext-discussiontools-init-section-metadata"></div><div class="ext-discussiontools-init-section-actions"></div></div></div> <span data-mw-comment-start="" id="c-Dtprice-2016-11-26T00:18:00.000Z-References"></span><style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-Monteith2008-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-Monteith2008_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Monteith2008_1-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Monteith, J.L., and Unsworth, M.H. 2008. <i>Principles of Environmental Physics</i>. Third Ed. AP, Amsterdam. <a rel="nofollow" class="external free" href="http://store.elsevier.com/Principles-of-Environmental-Physics/John-Monteith/isbn-9780080924793/">http://store.elsevier.com/Principles-of-Environmental-Physics/John-Monteith/isbn-9780080924793/</a></span> </li> <li id="cite_note-Tetens1930-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-Tetens1930_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Tetens1930_2-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Tetens, O. 1930. Über einige meteorologische Begriffe. Z. Geophys 6: 207-309.</span> </li> <li id="cite_note-Murray1967-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-Murray1967_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Murray1967_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Murray, F.W. 1967. On the computation of saturation vapour pressure. J. Applied Meteorology 6: 203-204. <a rel="nofollow" class="external free" href="https://dx.doi.org/10.1175/1520-0450(1967)006">http://dx.doi.org/10.1175/1520-0450(1967)006</a><0203:OTCOSV>2.0.CO;2</span> </li> <li id="cite_note-Lide2005-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-Lide2005_4-0">^</a></b></span> <span class="reference-text">Lide 2005</span> </li> <li id="cite_note-Buck1981-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-Buck1981_5-0">^</a></b></span> <span class="reference-text">Buck, A. L. 1981, New equations for computing vapor pressure and enhancement factor, J. Applied Meteorology, 20: 1527–1532. </span> </li> <li id="cite_note-Lowe1977-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-Lowe1977_6-0">^</a></b></span> <span class="reference-text">Lowe, P.R. 1977. An approximating polynomial for the computation of saturation vapor pressure. J. Applied Meteorology 16: 100-104. <a rel="nofollow" class="external free" href="https://dx.doi.org/10.1175/1520-0450(1977)016">http://dx.doi.org/10.1175/1520-0450(1977)016</a><0100:AAPFTC>2.0.CO;2</span> </li> <li id="cite_note-Wexler1976-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-Wexler1976_7-0">^</a></b></span> <span class="reference-text">Wexler, A. 1976. Vapor pressure formulation for water in range 0 to 100°C. A revision. J. Res. Natl. Bur. Stand. 80A: 775-285.</span> </li> <li id="cite_note-Wexler1977-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-Wexler1977_8-0">^</a></b></span> <span class="reference-text">Wexler, A. 1977. Vapor pressure formulation for ice. J. Res. Natl. Bur. Stand. 81A: 5-20.</span> </li> <li id="cite_note-Flatau1992-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-Flatau1992_9-0">^</a></b></span> <span class="reference-text">Flatau, P.J., Walko, R.L., and Cotton, W.R. 1992. Polynomial fits to saturation vapor pressure. J. Applied Meteorology 31: 1507-1513.</span> </li> <li id="cite_note-vpicebiopharma-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-vpicebiopharma_10-0">^</a></b></span> <span class="reference-text">Vapour Pressure of Ice, Biopharma Group, UK, 30 March 2015 Blog Post <a rel="nofollow" class="external free" href="https://biopharma.co.uk/blog/2015/03/30/vapour-pressure-of-ice/">https://biopharma.co.uk/blog/2015/03/30/vapour-pressure-of-ice/</a></span> </li> </ol></div></div> <p><small class="autosigned">— Preceding <a href="/wiki/Wikipedia:Signatures" title="Wikipedia:Signatures">unsigned</a> comment added by <a href="/wiki/User_talk:Dtprice" title="User talk:Dtprice">talk</a> 00:18, 26 November 2016 (UTC)</small> Comment was added and now updated by <a href="/w/index.php?title=User:Dtprice&action=edit&redlink=1" class="new" title="User:Dtprice (page does not exist)">Dtprice</a> (<a href="/wiki/User_talk:Dtprice" title="User talk:Dtprice">talk</a>) <a href="https://en.wikipedia.org/wiki/Talk:Vapour_pressure_of_water#c-Dtprice-2016-11-26T00:18:00.000Z-References" class="ext-discussiontools-init-timestamplink">16:51, 26 November 2016 (UTC)</a><span class="ext-discussiontools-init-replylink-buttons" data-mw-thread-id="c-Dtprice-2016-11-26T00:18:00.000Z-References"><span class="ext-discussiontools-init-replylink-bracket">[</span><a class="ext-discussiontools-init-replylink-reply" role="button" tabindex="0" href="">reply</a><span class="ext-discussiontools-init-replylink-bracket">]</span></span><span data-mw-comment-end="c-Dtprice-2016-11-26T00:18:00.000Z-References"></span> </p>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Talk:Vapour_pressure_of_water&oldid=1205899061">https://en.wikipedia.org/w/index.php?title=Talk:Vapour_pressure_of_water&oldid=1205899061</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Start-Class_Chemistry_articles" title="Category:Start-Class Chemistry articles">Start-Class Chemistry articles</a></li><li><a href="/wiki/Category:Low-importance_Chemistry_articles" title="Category:Low-importance Chemistry articles">Low-importance Chemistry articles</a></li><li><a href="/wiki/Category:WikiProject_Chemistry_articles" title="Category:WikiProject Chemistry articles">WikiProject Chemistry articles</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden category: <ul><li><a href="/wiki/Category:Talk_pages_with_comments_before_the_first_section" title="Category:Talk pages with comments before the first section">Talk pages with comments before the first section</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 10 February 2024, at 18:26<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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