Atmosphere (unit)
582780
224550330
2008-07-09T10:50:15Z
Zorrobot
7218328
robot Modifying: [[uk:Атмосфера (одиниця)]]
'''Standard atmosphere''' is a pressure defined as 101,325 [[Pascal (unit)|Pa]] and used as unit of [[pressure]] (symbol: atm). Standard atmosphere is a non-[[SI]] unit that is internationally recognized. The [http://www.bipm.org/jsp/en/ViewCGPMResolution.jsp?CGPM=10&RES=4 10th Conférence Générale des Poids et Mesures] (10th CGPM) adopted ''standard atmosphere'' for general use and affirmed its definition of being precisely equal to 1,013,250 [[dyne]]s per [[square centimeter]] (101,325 [[Pascal (unit)|Pa]]). This value is intended to represent the mean atmospheric pressure at mean sea level at the latitude of [[Paris|Paris, France]], and as a practical matter, truly reflects the mean sea level pressure for many of the industrialized nations (those with latitudes similar to Paris).
In [[chemistry]], the original definition of “Standard Temperature and Pressure” ([[standard conditions for temperature and pressure|STP]]) was a reference temperature of 0 [[°C]] (273.15 [[kelvin|K]]) and pressure of 101.325 [[kilopascal|kPa]] (1 atm). However, in 1982, the [[International Union of Pure and Applied Chemistry]] (IUPAC) recommended that for the purposes of specifying the physical properties of substances, “''the standard pressure''” should be defined as precisely 100 kPa (≈750.062 Torr).<ref>IUPAC.org, Gold Book, ''[http://goldbook.iupac.org/S05921.html Standard Pressure]''</ref>
==Pressure units and equivalencies ==
{{Pressure Units}}
A pressure of 1 atm can also be stated as:
:≡1.013 25 [[bar (unit)|bar]]
:≡101.325 [[kilopascal|kPa]]
:≡1013.25 [[millibar]]s (mbar, also mb) or [[hectopascal]]s (hPa)
:≡760 [[torr]]<sup> [B]</sup>
:≈760.001 mm-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available<sup> [B, C]</sup>
:≈29.9213 in-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available<sup> [C]</sup>
:≈1.033 227 452 799 886 [[kgf]]/cm²
:≈1.033 227 452 799 886 [[technical atmosphere]]
:≈1033.227 452 799 886 cm–H<sub>2</sub>O, 4 °C<sup> [A]</sup>
:≈406.782 461 732 2385 in–H<sub>2</sub>O, 4 °C<sup> [A]</sup>
:≈14.695 948 775 5134 [[pound-force per square inch|pounds-force per square inch]] (psi)
:≈2116.216 623 673 94 pounds-force per square foot psf)
:Notes:
:<sup>A</sup> This is the customarily-accepted value for cm–H<sub>2</sub>O, 4 °C. It is precisely the product of 1 kg-force per square centimeter (one technical atmosphere) times 1.013 25 (bar/atmosphere) divided by 0.980 665 (one gram-force). It is not accepted practice to define the value for water column based on a true physical realization of water (which would be 99.997 495% of this value because the true maximum density of [[Vienna Standard Mean Ocean Water]] is 0.999 974 95 kg/l at 3.984 °C). Also, this “physical realization” would ''still'' ignore the 8.285 cm–H<sub>2</sub>O reduction that would actually occur in a true physical realization due to the vapor pressure over water at 3.984 °C.
:<sup>B</sup> Torr and mm-Hg, 0°C are often taken to be identical. For most practical purposes (to 5 significant digits), they are interchangeable.
:<sup>C</sup> [[NIST]] value of 13.595 078(5) g/ml assumed for the density of Hg at 0 °C
==Other applications==
In the [[United Kingdom]], [[scuba diver]]s and others often use the word ''atmosphere'' loosely (the correct term is "ambient pressure") to mean 1 [[bar (unit)|bar]] (1000 millibars, or 100<font size="-1"> </font>000 [[pascal (unit)|Pa]]).
The unit [[technical atmosphere]] (at) is roughly equal to the gauge pressure under 10 [[metre|m]] of water; 1 at = 98066.5 Pa.
==See also==
*[[Standard conditions for temperature and pressure]]
== References ==
{{reflist}}
[[Category:Units of pressure]]
[[Category:Atmosphere]]
[[Category:Chemical engineering]]
[[Category:Environmental engineering]]
[[Category:Mechanical engineering]]
[[Category:Physical chemistry]]
[[Category:Standards]]
[[Category:Thermodynamics]]
[[be-x-old:Атмасфэра (адзінка вымярэньня)]]
[[bs:Standardna atmosfera]]
[[bg:Атмосфера (единица)]]
[[ca:Atmosfera (unitat)]]
[[cs:Atmosféra (jednotka)]]
[[da:Atmosfære (enhed)]]
[[de:Physikalische Atmosphäre]]
[[et:Atmosfäär (ühik)]]
[[el:Ατμόσφαιρα (μονάδα)]]
[[es:Atmósfera (unidad)]]
[[eu:Atmosfera (unitatea)]]
[[fa:اتمسفر (واحد)]]
[[fr:Atmosphère (unité)]]
[[ko:기압]]
[[hr:Standardna atmosfera]]
[[it:Atmosfera (unità di misura)]]
[[he:אטמוספירה (מידה)]]
[[lv:Atmosfēra (mērvienība)]]
[[lt:Atmosfera (matavimo vienetas)]]
[[hu:Atmoszféra (mértékegység)]]
[[nl:Atmosfeer (eenheid)]]
[[no:Standardatmosfære]]
[[nn:Standardatmosfære]]
[[pl:Atmosfera fizyczna]]
[[pt:Atmosfera padrão]]
[[ru:Атмосфера (единица измерения)]]
[[sk:Atmosféra (jednotka)]]
[[sl:Atmosfera (enota)]]
[[sv:Atmosfär (tryckenhet)]]
[[uk:Атмосфера (одиниця)]]
[[zh:标准大气压]]