Standard conditions

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

• in physics , chemistry , medicine , biology and process engineering for the definition of process conditions to be complied with (especially temperature and pressure ) in order to be able to compare the behavior or result of one process with another.
• in gas quantity and gas flow measurement for the definition of "standard volume" and "standard volume flow " (see also state number ).

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 .