Gas analysis — Vocabulary

ISO 7504:2015 defines terms related to gas analysis, with the main focus on terms related to calibration gas mixtures for use in gas analysis and gas measurements. It does not cover terms which relate only to specific applications.

Analyse des gaz — Vocabulaire

L'ISO 7504:2015 définit les termes relatifs à l'analyse des gaz, en insistant plus particulièrement sur les termes relatifs aux mélanges de gaz pour étalonnage utilisés dans l'analyse des gaz et les mesurages de gaz. Les termes qui recouvrent des applications spécifiques n'y figurent pas.

Analiza plinov - Slovar

Ta mednarodni standard opredeljuje izraze, povezane z analizo plinov, pri čemer se osredotoča predvsem na izraze, povezane s kalibracijskimi plinskimi mešanicami za uporabo pri analizi plinov in meritvah plinov. Ne zajema izrazov, ki se nanašajo samo na določene aplikacije.

General Information

Status
Published
Publication Date
10-May-2015
Current Stage
9093 - International Standard confirmed
Start Date
11-May-2021
Completion Date
11-May-2021

RELATIONS

Effective Date
28-Feb-2009

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INTERNATIONAL ISO
STANDARD 7504
Third edition
2015-05-15
Gas analysis — Vocabulary
Analyse des gaz — Vocabulaire
Reference number
ISO 7504:2015(E)
ISO 2015
---------------------- Page: 1 ----------------------
ISO 7504:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 7504:2015(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms relating to general concepts ................................................................................................................................................... 1

4 Terms relating to physical properties ............................................................................................................................................ 3

5 Terms relating to calibration gases ................................................................................................................................................... 5

6 Terms relating to methods for the preparation of gas mixtures ........................................................................ 6

7 Terms relating to storage in gas cylinders ................................................................................................................................. 7

8 Terms relating to gas analysis................................................................................................................................................................. 7

9 Terms from metrology .................................................................................................................................................................................... 9

Annex A (normative) List of terms defined in ISO/IEC Guide 98-3 and ISO/IEC Guide 99 ........................11

Annex B (normative) Sampling definitions ................................................................................................................................................12

Annex C (informative) Index ......................................................................................................................................................................................13

Bibliography .............................................................................................................................................................................................................................15

© ISO 2015 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 7504:2015(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any

patent rights identified during the development of the document will be in the Introduction and/or on

the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers

to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 158, Analysis of gases.

This third edition cancels and replaces the second edition (ISO 7504:2001), which has been technically

revised for alignment with the terminology used in other International Standards, including

ISO/IEC Guide 98-3 and ISO/IEC Guide 99:2007.
iv © ISO 2015 – All rights reserved
---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO 7504:2015(E)
Gas analysis — Vocabulary
1 Scope

This International Standard defines terms related to gas analysis, with the main focus on terms related

to calibration gas mixtures for use in gas analysis and gas measurements. It does not cover terms which

relate only to specific applications.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

measurement (GUM:1995)

ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and

associated terms (VIM)
ISO 10715:1997, Natural gas — Sampling guidelines
3 Terms relating to general concepts

Terms used in the field of gas analysis that are well defined by either ISO/IEC Guide 98-3 or

ISO/IEC Guide 99 are included in Annex A.
3.1
homogeneity

state of a gas mixture wherein all of its components (3.3) are distributed uniformly throughout the

volume occupied by the gas mixture
3.2
stability

attribute of a gas mixture, under specified conditions, to maintain its composition (3.5) within specified

uncertainty (Annex A) limits for a specified period of time (maximum storage life (7.5))

3.3
component

chemical entity at a defined physical state present in a material or in a mixture

3.4
content

amount-of-substance fraction (3.5.1.1), mass fraction (3.5.1.2), volume fraction (3.5.1.3), amount-of-

substance concentration (3.5.2.1), mass concentration (3.5.2.2), volume concentration (3.5.2.3) of a

component (3.3) in a gas or gas mixture
[7]
Note 1 to entry: See ISO 14912 for further information about this concept.

EXAMPLE 1 The hydrogen content in a mixture of hydrogen and nitrogen, expressed as an amount-of-substance

fraction (3.5.1.1), is x(H ) = 0,1.

EXAMPLE 2 The content of sulfur dioxide in air at p = 101,325 kPa and T = 288,15 K, expressed as a mass

concentration (3.5.2.2), is γ(SO ) = 1 mg/m .
© ISO 2015 – All rights reserved 1
---------------------- Page: 5 ----------------------
ISO 7504:2015(E)
3.5
composition

identity and content (3.4) of each component (3.3) that constitute a particular gas mixture

3.5.1 Fractions
3.5.1.1
amount-of-substance fraction
mole fraction
x , y
B B

quotient of the amount of substance of a component B and the sum of the amounts of substance of all

components (3.3) of the gas mixture
[SOURCE: ISO 80000-9:2009, 9-14]
3.5.1.2
mass fraction

quotient of the mass of a component B and the sum of the masses of all components (3.3) of the gas mixture

[SOURCE: ISO 80000-9:2009, 9-12]
3.5.1.3
volume fraction

quotient of the volume of a component B and the sum of the volumes of all components (3.3) of the gas

mixture before mixing, all volumes referring to the pressure and the temperature of the gas mixture

[SOURCE: ISO 80000-9:2009, 9-15]
3.5.2 Concentrations
3.5.2.1
amount-of-substance concentration
mole concentration

quotient of the amount of substance of a component B and the volume of the gas mixture

[SOURCE: ISO 80000-9:2009, 9-13]
3.5.2.2
mass concentration
quotient of the mass of a component B and the volume of the gas mixture
[SOURCE: ISO 80000-9:2009, 9-11.2]
3.5.2.3
volume concentration

quotient of the volume of a component B before mixing and the volume of the gas mixture, both volumes

referring to the same pressure and the same temperature

Note 1 to entry: The volume concentration and the volume fraction (3.5.1.3), both referring to the same pressure

and the same temperature, have identical values if, and only if, the sum of the component volumes and the volume

of the whole gas mixture are identical.
2 © ISO 2015 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 7504:2015(E)
4 Terms relating to physical properties
4.1
equation of state

mathematical relationship between the state variables (pressure and temperature) of a gas or gas

mixture and the volume occupied by a given amount of substance, written as pV = ZnRT

Note 1 to entry: In this relationship
p is the pressure;
V is the volume;
Z is the compressibility factor (4.2);
n is the amount of substance;
R is the molar gas constant;
T is the absolute temperature.
4.2
compressibility factor
compression factor
Z-factor
real-gas factor

quotient of the volume of an arbitrary amount of gas at specified pressure and temperature and the

volume of the same amount of gas, at the same state conditions, as calculated from the ideal gas law

4.3
reference conditions

definite values of pressure and temperature (state conditions) of gases and gas mixtures to which the

results of measurements and/or calculations should refer

EXAMPLE In the field of gas analysis and gas measurement, the following conditions are commonly preferred:

— normal conditions: p = 101,325 kPa, T = 273,15 K;
[5]
— metric standard conditions: p = 101,325 kPa, T = 288,15 K (see ISO 13443 ).
4.4
density

quotient of the mass and the volume occupied by that mass at specified state conditions

[SOURCE: ISO 80000-9:2009, 9-11.1]
4.4.1
relative density

quotient of the gas density and the density of dry air of standard composition, specified at the same

state conditions
[SOURCE: ISO 6976:1995, 2.4, modified — Language aligned with other definitions]
4.5
saturation vapour pressure

pressure exerted by the vapour of a chemical substance in equilibrium with a condensed phase (liquid

or solid or both) in a closed system

Note 1 to entry: For each pure substance, saturation vapour pressure is a function of temperature only.

© ISO 2015 – All rights reserved 3
---------------------- Page: 7 ----------------------
ISO 7504:2015(E)
4.6
dew point

temperature at or below which, at a specified pressure, condensation from the gas phase will occur

Note 1 to entry: For pure substances, dew point and bubble point (4.7) coincide. At that temperature, the pressure

equals the saturation vapour pressure (4.5).
4.7
bubble point

pressure and temperature condition at which the liquid phase is in equilibrium with the first appearing

bubbles of gas

Note 1 to entry: For pure substances, dew point (4.6) and bubble point coincide. At that temperature, the pressure

equals the saturation vapour pressure (4.5).
4.8
critical point

single point in pressure-temperature space at which the composition (3.5) and properties of the gas and

liquid phases in equilibrium are identical

Note 1 to entry: The pressure at this point is known as the “critical pressure p ” and the temperature as the

“critical temperature T ”, respectively.

Note 2 to entry: For a pure substance, the critical temperature is that temperature above which only the gas phase

can exist irrespective of the applied pressure.
4.9
cricondenbar
maximum pressure at which two-phase separation (condensation) can occur

Note 1 to entry: The phase coordinates cricondenbar and cricondentherm (4.10) apply to gas mixtures (with the

binary system as the simplest case). For a gas mixture, the critical point (4.8) is no longer the maximum pressure,

as well as the maximum temperature for vapour-liquid coexistence (see Figure 1).

Note 2 to entry: It is the highest pressure in the two-phase envelope and generally higher than the critical pressure.

Note 3 to entry: For a pure substance, cricondentherm (4.10), cricondenbar, and critical point (4.8) are represented

by a single point, i.e. the critical point.
4.10
cricondentherm
maximum temperature at which two-phase separation (condensation) can occur

Note 1 to entry: The phase coordinates cricondenbar (4.9) and cricondentherm apply to gas mixtures (with the

binary system as the simplest case). For a gas mixture, the critical point (4.8) is no longer the maximum pressure,

as well as the maximum temperature for vapour-liquid coexistence (see Figure 1).

Note 2 to entry: It is the highest temperature in the two-phase envelope and generally higher than the critical

temperature.

Note 3 to entry: For a pure substance, cricondentherm, cricondenbar (4.9), and critical point (4.8) are represented

by a single point, i.e. the critical point.
4 © ISO 2015 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 7504:2015(E)
Key
1 critical point B dew point curve
2 cricondenbar (l) liquid phase
3 cricondentherm (g) gaseous phase
A bubble point curve (lg) two-phase (liquid-vapour) region
Figure 1 — The p,T phase envelope of a binary system
5 Terms relating to calibration gases
5.1
calibration gas mixture

gas mixture of known stability (3.2) and homogeneity (3.1) whose composition (3.5) is well established

for use in the calibration (Annex A) or verification (9.2) of a measuring instrument or for the validation

(9.3) of a measurement

Note 1 to entry: Calibration gas mixtures are measurement standards (Annex A) as defined in ISO/IEC Guide 99.

5.2
reference gas mixture

calibration gas mixture (5.1) whose composition (3.5) is well established and stable to be used as a

reference standard of composition from which other composition data measurements are derived

Note 1 to entry: Reference gas mixtures are reference measurement standards (Annex A) as defined in

ISO/IEC Guide 99.
5.3
parent gas
gas, vapour, or gas mixture used for preparation of other gas mixtures
© ISO 2015 – All rights reserved 5
---------------------- Page: 9 ----------------------
ISO 7504:2015(E)
5.4
complementary gas
balance gas
diluent gas
major gas
matrix gas
component (3.3) of a gas mixture which is usually added at the
...

SLOVENSKI STANDARD
SIST ISO 7504:2016
01-junij-2016
1DGRPHãþD
SIST ISO 7504:2002
Analiza plinov - Slovar
Gas analysis - Vocabulary
Analyse des gaz - Vocabulaire
Ta slovenski standard je istoveten z: ISO 7504:2015
ICS:
01.040.71 Kemijska tehnologija Chemical technology
(Slovarji) (Vocabularies)
71.040.40 Kemijska analiza Chemical analysis
SIST ISO 7504:2016 en,fr

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST ISO 7504:2016
---------------------- Page: 2 ----------------------
SIST ISO 7504:2016
INTERNATIONAL ISO
STANDARD 7504
Third edition
2015-05-15
Gas analysis — Vocabulary
Analyse des gaz — Vocabulaire
Reference number
ISO 7504:2015(E)
ISO 2015
---------------------- Page: 3 ----------------------
SIST ISO 7504:2016
ISO 7504:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 7504:2016
ISO 7504:2015(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms relating to general concepts ................................................................................................................................................... 1

4 Terms relating to physical properties ............................................................................................................................................ 3

5 Terms relating to calibration gases ................................................................................................................................................... 5

6 Terms relating to methods for the preparation of gas mixtures ........................................................................ 6

7 Terms relating to storage in gas cylinders ................................................................................................................................. 7

8 Terms relating to gas analysis................................................................................................................................................................. 7

9 Terms from metrology .................................................................................................................................................................................... 9

Annex A (normative) List of terms defined in ISO/IEC Guide 98-3 and ISO/IEC Guide 99 ........................11

Annex B (normative) Sampling definitions ................................................................................................................................................12

Annex C (informative) Index ......................................................................................................................................................................................13

Bibliography .............................................................................................................................................................................................................................15

© ISO 2015 – All rights reserved iii
---------------------- Page: 5 ----------------------
SIST ISO 7504:2016
ISO 7504:2015(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any

patent rights identified during the development of the document will be in the Introduction and/or on

the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers

to Trade (TBT), see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 158, Analysis of gases.

This third edition cancels and replaces the second edition (ISO 7504:2001), which has been technically

revised for alignment with the terminology used in other International Standards, including

ISO/IEC Guide 98-3 and ISO/IEC Guide 99:2007.
iv © ISO 2015 – All rights reserved
---------------------- Page: 6 ----------------------
SIST ISO 7504:2016
INTERNATIONAL STANDARD ISO 7504:2015(E)
Gas analysis — Vocabulary
1 Scope

This International Standard defines terms related to gas analysis, with the main focus on terms related

to calibration gas mixtures for use in gas analysis and gas measurements. It does not cover terms which

relate only to specific applications.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in

measurement (GUM:1995)

ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and

associated terms (VIM)
ISO 10715:1997, Natural gas — Sampling guidelines
3 Terms relating to general concepts

Terms used in the field of gas analysis that are well defined by either ISO/IEC Guide 98-3 or

ISO/IEC Guide 99 are included in Annex A.
3.1
homogeneity

state of a gas mixture wherein all of its components (3.3) are distributed uniformly throughout the

volume occupied by the gas mixture
3.2
stability

attribute of a gas mixture, under specified conditions, to maintain its composition (3.5) within specified

uncertainty (Annex A) limits for a specified period of time (maximum storage life (7.5))

3.3
component

chemical entity at a defined physical state present in a material or in a mixture

3.4
content

amount-of-substance fraction (3.5.1.1), mass fraction (3.5.1.2), volume fraction (3.5.1.3), amount-of-

substance concentration (3.5.2.1), mass concentration (3.5.2.2), volume concentration (3.5.2.3) of a

component (3.3) in a gas or gas mixture
[7]
Note 1 to entry: See ISO 14912 for further information about this concept.

EXAMPLE 1 The hydrogen content in a mixture of hydrogen and nitrogen, expressed as an amount-of-substance

fraction (3.5.1.1), is x(H ) = 0,1.

EXAMPLE 2 The content of sulfur dioxide in air at p = 101,325 kPa and T = 288,15 K, expressed as a mass

concentration (3.5.2.2), is γ(SO ) = 1 mg/m .
© ISO 2015 – All rights reserved 1
---------------------- Page: 7 ----------------------
SIST ISO 7504:2016
ISO 7504:2015(E)
3.5
composition

identity and content (3.4) of each component (3.3) that constitute a particular gas mixture

3.5.1 Fractions
3.5.1.1
amount-of-substance fraction
mole fraction
x , y
B B

quotient of the amount of substance of a component B and the sum of the amounts of substance of all

components (3.3) of the gas mixture
[SOURCE: ISO 80000-9:2009, 9-14]
3.5.1.2
mass fraction

quotient of the mass of a component B and the sum of the masses of all components (3.3) of the gas mixture

[SOURCE: ISO 80000-9:2009, 9-12]
3.5.1.3
volume fraction

quotient of the volume of a component B and the sum of the volumes of all components (3.3) of the gas

mixture before mixing, all volumes referring to the pressure and the temperature of the gas mixture

[SOURCE: ISO 80000-9:2009, 9-15]
3.5.2 Concentrations
3.5.2.1
amount-of-substance concentration
mole concentration

quotient of the amount of substance of a component B and the volume of the gas mixture

[SOURCE: ISO 80000-9:2009, 9-13]
3.5.2.2
mass concentration
quotient of the mass of a component B and the volume of the gas mixture
[SOURCE: ISO 80000-9:2009, 9-11.2]
3.5.2.3
volume concentration

quotient of the volume of a component B before mixing and the volume of the gas mixture, both volumes

referring to the same pressure and the same temperature

Note 1 to entry: The volume concentration and the volume fraction (3.5.1.3), both referring to the same pressure

and the same temperature, have identical values if, and only if, the sum of the component volumes and the volume

of the whole gas mixture are identical.
2 © ISO 2015 – All rights reserved
---------------------- Page: 8 ----------------------
SIST ISO 7504:2016
ISO 7504:2015(E)
4 Terms relating to physical properties
4.1
equation of state

mathematical relationship between the state variables (pressure and temperature) of a gas or gas

mixture and the volume occupied by a given amount of substance, written as pV = ZnRT

Note 1 to entry: In this relationship
p is the pressure;
V is the volume;
Z is the compressibility factor (4.2);
n is the amount of substance;
R is the molar gas constant;
T is the absolute temperature.
4.2
compressibility factor
compression factor
Z-factor
real-gas factor

quotient of the volume of an arbitrary amount of gas at specified pressure and temperature and the

volume of the same amount of gas, at the same state conditions, as calculated from the ideal gas law

4.3
reference conditions

definite values of pressure and temperature (state conditions) of gases and gas mixtures to which the

results of measurements and/or calculations should refer

EXAMPLE In the field of gas analysis and gas measurement, the following conditions are commonly preferred:

— normal conditions: p = 101,325 kPa, T = 273,15 K;
[5]
— metric standard conditions: p = 101,325 kPa, T = 288,15 K (see ISO 13443 ).
4.4
density

quotient of the mass and the volume occupied by that mass at specified state conditions

[SOURCE: ISO 80000-9:2009, 9-11.1]
4.4.1
relative density

quotient of the gas density and the density of dry air of standard composition, specified at the same

state conditions
[SOURCE: ISO 6976:1995, 2.4, modified — Language aligned with other definitions]
4.5
saturation vapour pressure

pressure exerted by the vapour of a chemical substance in equilibrium with a condensed phase (liquid

or solid or both) in a closed system

Note 1 to entry: For each pure substance, saturation vapour pressure is a function of temperature only.

© ISO 2015 – All rights reserved 3
---------------------- Page: 9 ----------------------
SIST ISO 7504:2016
ISO 7504:2015(E)
4.6
dew point

temperature at or below which, at a specified pressure, condensation from the gas phase will occur

Note 1 to entry: For pure substances, dew point and bubble point (4.7) coincide. At that temperature, the pressure

equals the saturation vapour pressure (4.5).
4.7
bubble point

pressure and temperature condition at which the liquid phase is in equilibrium with the first appearing

bubbles of gas

Note 1 to entry: For pure substances, dew point (4.6) and bubble point coincide. At that temperature, the pressure

equals the saturation vapour pressure (4.5).
4.8
critical point

single point in pressure-temperature space at which the composition (3.5) and properties of the gas and

liquid phases in equilibrium are identical

Note 1 to entry: The pressure at this point is known as the “critical pressure p ” and the temperature as the

“critical temperature T ”, respectively.

Note 2 to entry: For a pure substance, the critical temperature is that temperature above which only the gas phase

can exist irrespective of the applied pressure.
4.9
cricondenbar
maximum pressure at which two-phase separation (condensation) can occur

Note 1 to entry: The phase coordinates cricondenbar and cricondentherm (4.10) apply to gas mixtures (with the

binary system as the simplest case). For a gas mixture, the critical point (4.8) is no longer the maximum pressure,

as well as the maximum temperature for vapour-liquid coexistence (see Figure 1).

Note 2 to entry: It is the highest pressure in the two-phase envelope and generally higher than the critical pressure.

Note 3 to entry: For a pure substance, cricondentherm (4.10), cricondenbar, and critical point (4.8) are represented

by a single point, i.e. the critical point.
4.10
cricondentherm
maximum temperature at which two-phase separation (condensation) can occur

Note 1 to entry: The phase coordinates cricondenbar (4.9) and cricondentherm apply to gas mixtures (with the

binary system as the simplest case). For a gas mixture, the critical point (4.8) is no longer the maximum pressure,

as well as the maximum temperature for vapour-liquid coexistence (see Figure 1).

Note 2 to entry: It is the highest temperature in the two-phase envelope and generally higher than the critical

temperature.

Note 3 to entry: For a pure substance, cricondentherm, cricondenbar (4.9), and critical point (4.8) are represented

by a single point, i.e. the critical point.
4 © ISO 2015 – All rights reserved
---------------------- Page: 10 ----------------------
SIST ISO 7504:2016
ISO 7504:2015(E)
Key
1 critical point B dew point curve
2 cricondenbar (l) liquid phase
3 cricondentherm (g) gaseous phase
A bubble point curve (lg) two-phase (liquid-vapour) region
Figure 1 — The p,T phase envelope of a binary system
5 Terms relating to calibration gases
5.1
calibration gas mixture

gas mixture of known stability (3.2) and homogeneity (3.1) whose composition (3.5) is well established

for use in the calibration (Annex A) or verification (9.2) of a measuring instrument or for the validation

(9.3) of a measurement

Note 1 to entry: Calibration gas mixtures are measurement standards (Annex A) as defined in ISO/IEC Guide 99.

5.2
reference gas mixture

calibration gas mixture (5.1) whose composition (3.5) is well established and stable to be used as a

reference standard of composition from which other composition data measurements are derived

Note 1 to entry: Reference gas mixtures are reference measurement standard
...

NORME ISO
INTERNATIONALE 7504
Troisième édition
2015-05-15
Analyse des gaz — Vocabulaire
Gas analysis — Vocabulary
Numéro de référence
ISO 7504:2015(F)
ISO 2015
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ISO 7504:2015(F)
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ii © ISO 2015 – Tous droits réservés
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ISO 7504:2015(F)
Sommaire Page

Avant-propos ..............................................................................................................................................................................................................................iv

1 Domaine d’application ................................................................................................................................................................................... 1

2 Références normatives ................................................................................................................................................................................... 1

3 Termes relatifs aux concepts généraux ........................................................................................................................................ 1

4 Termes relatifs aux propriétés physiques ................................................................................................................................. 3

5 Termes relatifs aux gaz d’étalonnage.............................................................................................................................................. 5

6 Termes relatifs aux méthodes de préparation des mélanges de gaz .............................................................6

7 Termes relatifs au stockage dans des bouteilles de gaz .............................................................................................. 7

8 Termes relatifs à l’analyse des gaz ..................................................................................................................................................... 7

9 Termes de métrologie ..................................................................................................................................................................................... 9

Annexe A (normative) Liste des termes définis dans le Guide ISO/IEC 98-3 et dans le

Guide ISO/IEC 99 ...............................................................................................................................................................................................11

Annexe B (normative) Définitions relatives à l’échantillonnage .........................................................................................12

Bibliographie ...........................................................................................................................................................................................................................13

© ISO 2015 – Tous droits réservés iii
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ISO 7504:2015(F)
Avant-propos

L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes

nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est

en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude

a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,

gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.

L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui concerne

la normalisation électrotechnique.

Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont

décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier de prendre note des différents

critères d’approbation requis pour les différents types de documents ISO. Le présent document a été

rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www.

iso.org/directives).

L’attention est appelée sur le fait que certains des éléments du présent document peuvent faire l’objet de

droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable

de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant les

références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de l’élaboration

du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de brevets reçues par

l’ISO (voir www.iso.org/brevets).

Les appellations commerciales éventuellement mentionnées dans le présent document sont données pour

information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un engagement.

Pour une explication de la signification des termes et expressions spécifiques de l’ISO liés à l’évaluation de

la conformité, ou pour toute information au sujet de l’adhésion de l’ISO aux principes de l’OMC concernant

les obstacles techniques au commerce (OTC), voir le lien suivant: Avant-propos — Informations

supplémentaires.

Le comité chargé de l’élaboration du présent document est l’ISO/TC 158, Analyse des gaz.

Cette troisième édition annule et remplace la deuxième édition (ISO 7504:2001), qui a fait l’objet d’une

révision technique.
iv © ISO 2015 – Tous droits réservés
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NORME INTERNATIONALE ISO 7504:2015(F)
Analyse des gaz — Vocabulaire
1 Domaine d’application

La présente Norme internationale définit les termes relatifs à l’analyse des gaz, en insistant plus

particulièrement sur les termes relatifs aux mélanges de gaz pour étalonnage utilisés dans l’analyse des

gaz et les mesurages de gaz. Les termes qui recouvrent des applications spécifiques n’y figurent pas.

2 Références normatives

Les documents ci-après, dans leur intégralité ou non, sont des références normatives indispensables à

l’application du présent document. Pour les références datées, seule l’édition citée s’applique. Pour les

références non datées, la dernière édition du document de référence s’applique (y compris les éventuels

amendements).

Guide ISO/IEC 98-3:2008, Incertitude de mesure — Partie 3: Guide pour l’expression de l’incertitude de

mesure (GUM:1995)

Guide ISO/IEC 99:2007, Vocabulaire international de métrologie — Concepts fondamentaux et généraux et

termes associés (VIM)
ISO 10715:1997, Gaz naturel — Lignes directrices pour l’échantillonnage.
3 Termes relatifs aux concepts généraux

Les termes utilisés dans le domaine de l’analyse des gaz et dont on trouve une définition satisfaisante

dans le Guide ISO/IEC 98-3 ou dans le Guide ISO/IEC 99 figurent à l’Annexe A.
3.1
homogénéité

état d’un mélange de gaz dont tous les constituants (3.3) sont uniformément répartis sur l’ensemble du

volume occupé par le mélange de gaz
3.2
stabilité

attribut d’un mélange gazeux, dans des conditions données, lié à la conservation de sa composition (3.5)

dans des limites d’incertitude (Annexe A) spécifiées pour une période donnée
[SOURCE: durée maximale de conservation (7.5)]
3.3
constituant

entité chimique, dans un état physique défini, présente dans un matériau ou un mélange

3.4
teneur

fraction de quantité de matières (3.5.1.1), fraction massique (3.5.1.2), fraction volumique (3.5.1.3),

concentration en quantité de matière (3.5.2.1), concentration massique (3.5.2.2), concentration

volumique (3.5.2.3) d’un constituant (3.3) dans un gaz ou un mélange de gaz
[7]

Note 1 à l’article: Voir l’ISO 14912 pour davantage d’informations sur ce concept.

EXEMPLE 1 La teneur en hydrogène dans un mélange d’hydrogène et d’azote, exprimée en fraction de quantité

de matières (3.5.1.1), est x(H ) = 0,1.
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ISO 7504:2015(F)

EXEMPLE 2 La teneur en dioxyde de soufre de l’air à p = 101,325 kPa et T = 288,15 K, exprimée en concentration

massique (3.5.2.2), est γ(SO ) = 1 mg/m .
3.5
composition

identification et teneur (3.4) de chaque constituant (3.3) formant un mélange de gaz particulier

3.5.1 Fractions
3.5.1.1
fraction de quantité de matières
fraction molaire
x , y
B B

quotient obtenu en divisant la quantité de matières d’un constituant B par la somme des quantités de

matières de tous les constituants (3.3) du mélange gazeux
[SOURCE: ISO 80000-9:2009, 9-14]
3.5.1.2
fraction massique

quotient obtenu en divisant la masse d’un constituant B par la somme des masses de tous les

constituants (3.3) du mélange gazeux
[SOURCE: ISO 80000-9:2009, 9-12]
3.5.1.3
fraction volumique

quotient obtenu en divisant le volume d’un constituant B par la somme des volumes de tous les

constituants (3.3) du mélange gazeux avant mélange, tous les volumes se référant à la pression et à la

température du mélange gazeux
[SOURCE: ISO 80000-9:2009, 9-15]
3.5.2 Concentrations
3.5.2.1
concentration en quantité de matière
concentration molaire

quotient obtenu en divisant la quantité de matières d’un constituant B par le volume du mélange gazeux

[SOURCE: ISO 80000-9:2009, 9-13]
3.5.2.2
concentration massique

quotient obtenu en divisant la masse d’un constituant B par le volume du mélange gazeux

[SOURCE: ISO 80000-9:2009, 9-11.2]
3.5.2.3
concentration volumique

quotient obtenu en divisant le volume d’un constituant B avant mélange par le volume du mélange de

gaz, les deux volumes se référant à la même pression et à la même température

Note 1 à l’article: La concentration volumique et la fraction volumique (3.5.1.3), les deux se référant à la même

pression et à la même température, ont des valeurs identiques si et seulement si la somme des volumes des

constituants et le volume de l’ensemble du mélange gazeux sont identiques.
2 © ISO 2015 – Tous droits réservés
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ISO 7504:2015(F)
4 Termes relatifs aux propriétés physiques
4.1
équation d’état

équation mathématique établissant la relation entre les variables d’état (pression et température) d’un

gaz ou d’un mélange gazeux, et le volume occupé par une quantité de matières donnée, s’écrivant pV = ZnRT

Note 1 à l’article: Dans cette équation
p est la pression
V est le volume;
Z est le facteur de compressibilité (4.2);
n est la quantité de matière;
R est la constante molaire des gaz;
T est la température absolue.
4.2
facteur de compressibilité
facteur de compression
facteur Z
facteur des gaz réels

quotient obtenu en divisant le volume d’une quantité arbitraire de gaz, à une pression et température

spécifiées, par le volume de la même quantité de gaz, aux mêmes conditions d’état, d’après la loi des gaz

parfaits
4.3
conditions de référence

valeurs données de pression et de température (conditions d’état) des gaz et mélanges gazeux, qu’il

convient d’utiliser comme valeurs de référence pour les mesures et/ou les calculs

EXEMPLE Dans le domaine de l’analyse des gaz et du mesurage des gaz, les conditions suivantes sont

généralement préconisées:
— conditions normales: p = 101,325 kPa, T = 273,15 K;
[5]

— conditions normales de référence métriques: p = 101,325 kPa, T = 288,15 K (voir l’ISO 13443 ).

4.4
masse volumique

quotient de la masse par le volume occupé par cette masse dans les conditions d’état spécifiées

[SOURCE: ISO 80000-9:2009, 9-11.1]
4.4.1
densité

quotient de la masse volumique du gaz à la masse volumique de l’air sec ayant une composition normale

de référence, dans les mêmes conditions d’état

[SOURCE: ISO 6976:1995, 2.4, modifié — Terminologie harmonisée compte tenu des autres définitions]

4.5
pression de vapeur saturante

pression exercée par la vapeur d’une substance chimique à l’équilibre avec une phase condensée (liquide,

solide ou les deux) dans un système fermé

Note 1 à l’article: Pour chaque substance pure, la pression de vapeur saturante dépend uniquement de la température.

© ISO 2015 – Tous droits réservés 3
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ISO 7504:2015(F)
4.6
point de rosée

température à laquelle ou au-dessous de laquelle se produit, à une pression donnée, la condensation à

partir de la phase gazeuse

Note 1 à l’article: Pour les substances pures, le point de rosée et le point de bulle (4.7) coïncident. À cette température,

la pression correspond à la pression de vapeur saturante (4.5).
4.7
point de bulle

conditions de pression et de température dans lesquelles la phase liquide est à l’équilibre et où les

premières bulles de gaz apparaissent

Note 1 à l’article: Pour les substances pures, le point de rosée (4.6) et le point de bulle coïncident. À cette température,

la pression correspond à la pression de vapeur saturante (4.5).
4.8
point critique

point unique du domaine pressions-températures où la composition (3.5) et les propriétés des phases

gazeuses et liquides à l’équilibre sont identiques

Note 1 à l’article: En ce point, la pression et la température sont appelées respectivement «pression critique p »

et «température critique T ».

Note 2 à l’article: Pour une substance pure, la température critique est la température au-dessus de laquelle ne

peut exister que la phase gazeuse, quelle que soit la pression appliquée.
4.9
cricondenbar

pression maximale à laquelle une séparation en deux phases (condensation) peut se produire

Note 1 à l’article: Les coordonnées de phase cricondenbar et cricondentherme (4.10) s’appliquent aux mélanges de gaz

(selon le système binaire dans le plus simple des cas). Pour un mélange de gaz, le point critique (4.8) ne correspond

plus à la pression maximale ni à la température maximale pour la coexistence liquide-vapeur (voir Figure 1).

Note 2 à l’article: Il s’agit de la pression la plus élevée de l’enveloppe diphasique, généralement plus élevée que la

pression critique.

Note 3 à l’article: Pour une substance pure, le cricondentherme (4.10), le cricondenbar et le point critique (4.8) sont

représentés par un unique point, à savoir le point critique.
4.10
cricondentherme

température maximale à laquelle une séparation en deux phases (condensation) peut se produire

Note 1 à l’article: Les coordonnées de phase cricondenbar (4.9) et cricondentherme s’appliquent aux mélanges de gaz

(selon le système binaire dans le plus simple des cas). Pour un mélange de gaz, le point critique (4.8) ne correspond

plus à la pression maximale ni à la température maximale pour la coexistence liquide-vapeur (voir Figure 1).

Note 2 à l’article: Il s’agit de la température la plus élevée de l’enveloppe diphasique, généralement plus élevée que

la température critique.

Note 3 à l’article: Pour une substance pure, le cricondentherme, le cricondenbar (4.9) et le point critique (4.8) sont

représentés par un unique point, à savoir le point critique.
4 © ISO 2015 – Tous droits réservés
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ISO 7504:2015(F)
Légende
1 point critique B courbe de rosée
2 cricondenbar (l) phase liquide
3 cricondentherme (g) phase gazeuse
A courbe de bulle (lg) région diphasique (liquide-vap
...

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