# Standard conditions

The term standard conditions is used in scientific and technical fields and basically has two meanings:

scope of application Name of the conditions temperature pressure definition annotation
physics Standard conditions ,
including normal conditions
273.15  K ≙ 0  ° C 101.325  kPa = 1.01325  bar = 1  atm DIN 1343 also apply in Germany to the specification of a gas quantity in stores, see standard cubic meters .
chemistry Standard conditions or STP conditions
273.15 K ≙ 0 ° C 100,000 kPa = 1,000 bar IUPAC ,
1982
While the standard conditions are used as reference values ​​from which one converts, standard conditions are often used to avoid conversions. In this sense, the IUPAC definition of exactly 1 bar is more modern and is particularly preferred for specifying thermodynamic material properties.
Electrochemistry When specifying the standard redox potential , one refers to the standard condition that all substances involved have an activity of 1. The reference temperature is 25 ° C. Redox potentials therefore correspond to the standard potentials at a = 1 at 25 ° C.
In this case the standard state of a substance in solution is activity a = 1. For the solutions that are not ideally diluted here, the concentration must be set so that the product of the activity coefficient (to be calculated or measured) and the concentration is one, since this is the activity.
In acidic solution, potentials are related to the potential of H 3 O + ions, in basic solution to that of OH - ions.
biochemistry Standard condition " pH  7" (neutral environment)
Medicine and Physiology ,
especially respiratory physiology
STPD conditions
( standard temperature, pressure, dry )
273.15 K ≙ 0 ° C 1013.25 hPa = 760 mmHg Water vapor partial pressure
p (H 2 O) = 0 kPa (dry)
BTPS conditions
( body temperature, pressure, saturated )
310.15 K ≙ 37 ° C
(normal human body temperature
)
actual air pressure p (H 2 O) = 6.25 kPa ( saturation vapor pressure at 37 ° C)
ATPS conditions
( ambient temperature, pressure, saturated :
actual measurement conditions outside the body)
Room temperature actual air pressure p (H 2 O) = saturation vapor pressure at the respective room temperature
Measurement of physical quantities,
e.g. B. of density , rotation value or
refractive index
Laboratory conditions ,
normal conditions
293,15 K ≙ 20 ° C
( Maßbezugstemperatur )
1013.25 mbar = 760  Torr
(reference atmospheric pressure at
the boiling point data )
Refractive indices are measured using the Na D line (589 nm) as the light source.
Gas chromatography SATP conditions
( Standard Ambient Temperature and Pressure )
298.15 K ≙ 25 ° C 101.300 kPa = 1.013 bar The standard volumes for gas chromatographic measurements are based on 25 ° C and 101,300 Pa
aviation ISA
( International Standard Atmosphere , international standard atmosphere )
288.15 K ≙ 15 ° C 1013.25 hPa (= 29.92 inHg)
at sea ​​level
ISO 2533 dry, further standard values ​​for temperature and pressure changes with increasing altitude
Compressed air industry Standard reference atmosphere 293.15 K ≙ 20 ° C 1 bar ISO 8778 (65% relative humidity )
293.15 K ≙ 20 ° C 1 bar DIN 1945-1 p (H 2 O) = 0 kPa (dry)

## Individual evidence

1. DIN 1343 “Reference condition, standard condition, standard volume; Concepts, Values ​​”, January 1990 edition.
2. U. Grigull: Standard volume and standard cubic meter . In: fuel, heat, power . tape 19 , no. 12 , 1967, p. 561-563 ( PDF [accessed August 18, 2016]).
3. JD Cox: Notation for states and processes, significance of the word standard in chemical thermodynamics, and remarks on commonly tabulated forms of thermodynamic functions . In: Pure and Applied Chemistry . tape 54 , no. 6 , 1982, pp. 1239–1250 , doi : 10.1351 / pac198254061239 ( PDF file; 226 kB [accessed February 8, 2014]).
4. Entry on standard conditions for gases . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.S05910 Version: 2.3.3.
5. Entry on standard pressure . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.S05921 Version: 2.3.3.
6. Schmidt, Lang: Physiologie des Menschen. 30th edition. Heidelberg 2007, ISBN 978-3-540-32908-4 .