Editing Atmospheric pressure (section)

== Boiling point of liquids ==
[[File:Kochendes wasser02.jpg|thumb|[[Boiling water]]]]
Pure water [[boiling|boils]] at {{convert|100|C}} at earth's standard atmospheric pressure. The boiling point is the temperature at which the [[vapour pressure]] is equal to the atmospheric pressure around the liquid.<ref>{{citation |url=http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/vappre.html |title=Vapour Pressure |publisher=Hyperphysics.phy-astr.gsu.edu |access-date=2012-10-17 |archive-date=2017-09-14 |archive-url=https://web.archive.org/web/20170914100414/http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/vappre.html |url-status=live }}</ref> Because of this, the boiling point of liquids is lower at lower pressure and higher at higher pressure. Cooking at high elevations, therefore, requires adjustments to recipes<ref>{{citation |url=http://www.crisco.com/Cooking_Central/Cooking_Tips/Prep_High_Alt.aspx |title=High Altitude Cooking |publisher=Crisco.com |date=2010-09-30 |access-date=2012-10-17 |url-status=dead |archive-url=https://web.archive.org/web/20120907232429/http://www.crisco.com/Cooking_Central/Cooking_Tips/Prep_High_Alt.aspx |archive-date=2012-09-07 }}</ref> or [[pressure cooking]]. A rough approximation of elevation can be obtained by measuring the temperature at which water boils; in the mid-19th century, this method was used by explorers.<ref>{{cite journal |first1=M. N. |last1=Berberan-Santos |first2=E. N. |last2=Bodunov |first3=L. |last3=Pogliani |title=On the barometric formula |journal=American Journal of Physics |volume=65 |issue=5 |pages=404–412 |year=1997 |doi=10.1119/1.18555 |bibcode = 1997AmJPh..65..404B  }}</ref> Conversely, if one wishes to evaporate a liquid at a lower temperature, for example in [[distillation]], the atmospheric pressure may be lowered by using a [[vacuum pump]], as in a [[rotary evaporator]].