In chemistry, the original definition of “Standard Temperature and Pressure” (STP) was a reference temperature of 0 °C (273.15 K) and pressure of 101.325 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 (exactly 1 bar).
A pressure of 1 atm can also be stated as:
:≡1.013 25 bar :≡ 1013.25 hectopascal (hPa) :≡ 1013.25 millibars (mbar, also mb) :≡ 760 torr [B] :≈ 760.001 mm-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available [B, C] :≈ 29.9213 in-Hg, 0 °C, subject to revision as more precise measurements of mercury’s density become available [C] :≈ 1.033 227 452 799 886 kgf/cm² :≈ 1.033 227 452 799 886 technical atmosphere :≈ 1033.227 452 799 886 cm–H2O, 4 °C [A] :≈ 406.782 461 732 2385 in–H2O, 4 °C [A] :≈ 14.695 948 775 5134 pounds-force per square inch (psi) :≈ 2116.216 623 673 94 pounds-force per square foot (psf)
:Notes: :A This is the customarily-accepted value for cm–H2O, 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–H2O reduction that would actually occur in a true physical realization due to the vapor pressure over water at 3.984 °C. :B Torr and mm-Hg, 0°C are often taken to be identical. For most practical purposes (to 5 significant digits), they are interchangeable. :C NIST value of 13.595 078(5) g/ml assumed for the density of Hg at 0 °C
The old European unit technical atmosphere (at) is roughly equal to the gauge pressure under 10 m of water; 1 at = 98066.5 Pa.
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 (یکا) fr:Atmosphère (unité) gl:Atmosfera (unidade) ko:기압 hr:Standardna atmosfera is:Loftþyngd it:Atmosfera (unità di misura) he:אטמוספירה (מידה) kk:Атмосфералық қысым lv:Atmosfēra (mērvienība) lt:Atmosfera (matavimo vienetas) hu:Atmoszféra (mértékegység) nl:Atmosfeer (eenheid) ja:標準気圧 no:Standardatmosfære nn:Standardatmosfære pl:Atmosfera fizyczna pt:Atmosfera padrão ru:Атмосфера (единица измерения) sk:Atmosféra (jednotka) sl:Atmosfera (enota) sv:Atmosfär (tryckenhet) tr:Atmosfer (birim) uk:Атмосфера (одиниця) vls:Atmosfeer (êenheid) zh:标准大气压This text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
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