ISO 7404-5:2025

International
Standard
ISO 7404-5
Fourth edition
Coal — Methods for petrographic
2025-10
analysis —
Part 5:
Method of determining
microscopically the reflectance of
vitrinite
Charbon — Méthodes d'analyse pétrographique —
Partie 5: Méthode de détermination au microscope du pouvoir
réflecteur de la vitrinite
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms & Definitions . 1
4 Principle . 1
5 Reagents and materials . 2
6 Apparatus . 3
7 Preparation of sample . 8
8 Procedure . 8
8.1 Setting up the apparatus .8
8.1.1 Starting procedure .8
8.1.2 Adjusting the microscope for random or maximum measurements .8
8.1.3 Illumination .8
8.1.4 Alignment .9
8.2 Checking the reliability and calibration of the apparatus .9
8.2.1 Stability of the apparatus .9
8.2.2 Variation in reading on rotating a reflectance standard on the stage .9
8.2.3 Correction for parasitic reflections and photomultiplier dark current .9
8.2.4 Linearity of the signal from the photomultiplier .9
8.2.5 Calibration of the apparatus .10
8.3 Measurement of the reflectance of vitrinite .10
8.3.1 General .10
8.3.2 Measurement of the maximum reflectance of vitrinite in oil .10
8.3.3 Measurement of the random reflectance of vitrinite in oil .11
9 Reporting of results .11
10 Precision .13
10.1 Repeatability . 13
10.2 Reproducibility .14
11 Test report . 14
Bibliography .15

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 27, Coal and coke, Subcommittee SC 5, Methods
of analysis.
This fourth edition cancels and replaces the third edition (ISO 7404-5:2009), which has been technically
revised.
The main changes are as follows:
— input from the International Committee for Coal and Organic Petrology (ICCP) has been added.
A list of all parts in the ISO 7404 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Petrographic analyses have been recognized internationally as important in the context of the genesis,
vertical and lateral variation, continuity, metamorphism and usage of coal. The International Committee
for Coal and Organic Petrology (ICCP) has made recommendations concerning nomenclature and analytical
[1][2][3][4][5][6]
methods and has described in detail the characteristics of a wide range of coals . This document
incorporates many useful comments made by members of the ICCP and by member bodies of ISO/TC 27.
Petrographic analyses of a single coal provide information about the rank, the maceral and microlithotype
compositions and the distribution of minerals in the coal. The reflectance of vitrinite is a useful measure
of coal rank and the distribution of the reflectance of vitrinite in a coal blend, together with a maceral
group analysis, can provide information about the rank and type of the coal and important chemical and
technological properties of the blend.
The ISO 7404 series is concerned with the methods of petrographic analysis currently employed in
characterizing coal in the context of its technological or geological use, or both. It establishes a system for
petrographic analysis.
[7]
The method of determining the reflectance of vitrinite is applicable for low-, medium- and high-rank coals .
The properties of a given coal are determined by the proportions and associations of the macerals and
minerals present and by the rank of the coal. The reflectance of the vitrinite in the coal can be used as an
indicator of rank, independent of the petrographic composition. Vitrinite reflectance increases progressively
with rank. The reflectance of vitrinite has various other applications, such as the characterization of bulk
samples and cargoes. For coal blends, the measurement of the vitrinite reflectance profile can permit the
identification of the component coals and permit the estimation of the relative abundance of the component
coals within the blend.
The reflectance of the macerals of the vitrinite group can vary significantly in a single coal seam and therefore
the value of the reflectance obtained depends also on the choice of the macerals used for measurement.
Reflectance measurements are made on one or more of the macerals of vitrinite. Consequently, a vital step in
the measurement of vitrinite reflectance is the identification of vitrinite and its various macerals or maceral
[1]
varieties. For this purpose, reference can be made to ISO 7404-1, the ICCP handbook and subsequent ICCP
[2][5]
authored journal articles .
[2]
For rank determination of single-seam coals, normally the reflectance of collotelinite (ulminite B in
[5]
lignites, the equivalent of low-rank B and C ) is determined. In cases where collotelinite (or in low-rank
coals, ulminite B) is not present in sufficient amounts, reflectance analysis on other vitrinite macerals
is performed. Reflectance analysis on various vitrinite macerals can also be applied for technological
purposes and to coal blends; see 8.3.1. The reflectance value obtained also depends on whether maximum
or random reflectance measurements are made, so it is necessary to specify the type of measurement.
All of these analysis procedures are applicable to single-coal seams or to blends providing that adequate
(see 8.3.1) reflectance measurements are made in compliance with an unbiased sampling procedure on a
representative sample.
For vitrinite reflectance analysis, the ICCP regularly run the Single Coal Accreditation Program (SCAP) for
accrediting petrologists in the analysis of single seam coals.
NOTE As the ISO 7404 series covers coals of all rank, the term “vitrinite” as used in this document includes
vitrinite as well as huminite. Reference can be made to ISO 7404-1 for details. The equivalent to collotelinite in lignites
is ulminite B. Reflectance measurement on lignites is performed on huminite.

v
International Standard ISO 7404-5:2025(en)
Coal — Methods for petrographic analysis —
Part 5:
Method of determining microscopically the reflectance of
vitrinite
1 Scope
This document specifies the methods for determining the reflectance of vitrinite of coals microscopically
on polished surfaces, immersed in oil. The methods are applicable to coals from single seams or coal blends
covering the whole range of low-, medium- and high-rank coal.
Vitrinite reflectance measurements can be used to characterize the components wi
...