ISO 14912:2003
(Main)Gas analysis — Conversion of gas mixture composition data
Gas analysis — Conversion of gas mixture composition data
ISO 14912:2003 defines the following quantities commonly used to express the composition of gas mixtures: mole fraction, mass fraction and volume fraction, as well as mole concentration, mass concentration and volume concentration. Relating to these quantities of composition, ISO 14912:2003 provides methods for the conversion between different quantities and the conversion between different state conditions. Conversion between different quantities means calculating the numerical value of an analyte content in terms of one of the quantities listed above from the numerical value of the same analyte content, at the same pressure and temperature of the gas mixture, given in terms of another of these quantities. Conversion between different state conditions means calculating the numerical value of an analyte content, in terms of one of the quantities listed above, under one set of state conditions from the numerical value of the same quantity under another set of state conditions, i.e. pressure and temperature, of the gas mixture. Gas mixture composition can be converted simultaneously between different quantities of composition and different state conditions by combination of the two types of conversion. ISO 14912:2003 is only applicable to homogeneous and stable gas mixtures. Therefore any state conditions (pressure and temperature) considered need to be well outside from the condensation region of the gas mixture and that of each of the specified analytes.
Analyse des gaz — Conversion des données de composition de mélanges gazeux
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 14912
First edition
2003-03-15
Gas analysis — Conversion of gas
mixture composition data
Analyse des gaz — Conversion des données de composition de
mélanges gazeux
Reference number
©
ISO 2003
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ii © ISO 2003 — All rights reserved
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Terms and definitions .1
3 Symbols and units .4
4 Basic principles.6
4.1 Expression of gas mixture composition.6
4.2 Conversion between different quantities.8
4.3 Conversion between different state conditions.9
5 Main procedures.10
5.1 Conversion between different quantities of composition.10
5.2 Conversion to reference conditions.13
6 Practical implementation.13
6.1 Conversion between quantities of composition .13
6.2 Conversion of single analyte contents .14
6.3 Conversion of complete compositions.15
6.4 Conversion between state conditions .15
6.5 Simple approximations applicable to conversion .15
7 Input quantities and their uncertainties.16
7.1 Pure gas data.16
7.2 Gas mixture data .19
7.3 Rough uncertainty estimates.22
8 Conversion uncertainty .22
8.1 General considerations .22
8.2 Conversion of single analyte contents .23
8.3 Conversion of complete compositions.24
8.4 Uncertainty calculation using numerical differentiation.26
8.5 Variances and covariances of input composition data.27
9 Application recommendations.29
Annex A (normative) Assessment of state conditions .30
Annex B (normative) Summation relations for the expression of mixture properties .33
Annex C (informative) Mixture component data .34
Annex D (informative) Examples.40
Annex E (informative) Computer implementation of recommended methods.55
Bibliography.57
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
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International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 14912 was prepared by Technical Committee ISO/TC 158, Analysis of gases.
iv © ISO 2003 — All rights reserved
Introduction
The objective of gas analysis is to determine the composition of gas mixtures. Gas mixture composition is
expressed qualitatively in terms of specified mixture components of interest, called analytes, and the
complementary gas. Gas mixture composition is expressed quantitatively by specifying the amount of every
analyte in the mixture and the composition of the complementary gas.
For the purpose of specifying the amount of an analyte in a gas mixture, different quantities are in use. This
diversity is due to the fact that in different applications different quantities have decisive advantages.
Therefore procedures for conversion between different quantities are required.
In cases where these quantities involve the volumes of the analytes or the gas mixture or both, they depend
on the state conditions, i.e. pressure and temperature, of the gas mixture. For each of these quantities,
procedures for conversion between different state conditions are required.
As a crude approximation, all of the conversions referred to above can be performed on the basis of the Ideal
Gas Law. In most cases, however, an accurate conversion has to take into account the real gas volumetric
behaviour of the analyte and of the gas mixture. In particular, many conversions require values of the
compression factor (or of the density) of the gas mixture.
This International Standard provides formally exact conversion procedures, based on fundamental principles,
which fully account for real gas behaviour of pure gases and gas mixtures. In addition to these, approximate
procedures for practical applications are described, designed for different levels of accuracy and available
data. These approximations are necessary because measured gas mixture compression factors (or densities)
are rarely available and therefore have to be estimated from component data. Uncertainty estimates are given
which result from combining approximations in the conversion procedures with the uncertainties of the input
data. Where conversions require real-gas volumetric data of pure gases or gas mixtures, these are expressed
by compression factors. As equivalents, density data could be converted into compression factor data.
INTERNATIONAL STANDARD ISO 14912:2003(E)
Gas analysis — Conversion of gas mixture composition data
1 Scope
This International Standard defines the following quantities commonly used to express the composition of gas
mixtures:
mole fraction,
mass fraction,
volume fraction,
and
mole concentration,
mass concentration,
volume concentration.
For these quantities of composition, this International Standard provides methods for
conversion between different quantities, and
conversion between different state conditions.
Conversion between different quantities means calculating the numerical value of an analyte content in terms
of one of the quantities listed above from the numerical value of the same analyte content, at the same
pressure and temperature of the gas mixture, given in terms of another of these quantities. Conversion
between different state conditions means calculating the numerical value of an analyte content, in terms of
one of the quantities listed above, under one set of state conditions from the numerical value of the same
quantity under another set of state conditions, i.e. pressure and temperature, of the gas mixture. Gas mixture
composition can be converted simultaneously between different quantities of composition and different state
conditions by combination of the two types of conversion.
This International Standard is applicable only to homogeneous and stable gas mixtures. Therefore any state
conditions (pressure and temperature) considered need to be well outside the condensation region of the gas
mixture and that of each of the specified analytes (see Annex A).
2 Terms and definitions
For the purpose of this document, the following terms and definitions apply.
NOTE See also References [1] and [2] in the Bibliography.
2.1 Quantities for the expression of gas mixture composition
NOTE Further information concerning the terms defined in this subclause is given in 4.1.
2.1.1
mole fraction
amount-of-substance fraction
x
quotient of the amount of substance of a specified component and the sum of the amounts of substance of all
components of a gas mixture
NOTE The mole fraction is independent of the pressure and the temperature of the gas mixture.
2.1.2
mass fraction
w
quotient of the mass of a specified component and the sum of the masses of all components of a gas mixture
NOTE The mass fraction is independent of the pressure and the temperature of the gas mixture.
2.1.3
volume fraction
φ
quotient of the volume of a specified component and the sum of the volumes of all components of a gas
mixture before mixing, all volumes referring to the pressure and the temperature of the gas mixture
NOTE The volume fraction is not independent of the pressure and the temperature of the gas mixture. Therefore the
pressure and the temperature have to be specified.
2.1.4
mole concentration
amount-of-substance concentration
c
quotient of the amount of substance of a specified component and the volume of a gas mixture
NOTE The mole concentration is not independent of the pressure and the temperature of the gas mixture. Therefore
the pressure and the temperature have to be specified.
2.1.5
mass concentration
β
quotient of the mass of a specified component and the volume of a gas mixture
NOTE The mass concentration is not independent of the pressure and the temperature of the gas mixture. Therefore
the pressure and the temperature have to be specified.
2.1.6
volume concentration
σ
quotient of the volume of a specified component before mixing and the volume of a gas mixture, both volumes
referring to the same pressure and the same temperature
NOTE 1 The volume concentration is not independent of the pressure and the temperature of the gas mixture.
Therefore the pressure and the temperature have to be specified.
NOTE 2 The volume fraction (2.1.3) and volume concentration (2.1.6) take the same value if, at the same state
conditions, the sum of the component volumes before mixing and the volume of the mixture are equal. However, because
the mixing of two or mo
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