ISO 5068-2:2007

Brown coals and lignites - Determination of moisture content - Part 2: Indirect gravimetric method for moisture in the analysis sample

ISO 5068-2:2007 specifies a method for the determination of the moisture content in the analysis sample of brown coals and lignites using an indirect gravimetric method.

Charbons bruns et lignites — Détermination de l'humidité — Partie 2: Méthode gravimétrique indirecte pour l'humidité de l'échantillon d'analyse

General Information

• Status: Published
• Publication Date: 09-Jan-2007
• ICS: 73.040 - Coals
• Technical Committee: ISO/TC 27/SC 5 - Methods of analysis
• Drafting Committee: ISO/TC 27/SC 5/WG 7 - Brown coals and lignites
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 05-May-2025
• Completion Date: 13-Dec-2025

Relations

• Revised: ISO 5068-2:2025 - Brown coals and lignites - Determination of moisture - Part 2: Indirect gravimetric method for moisture in the analysis sample
• Effective Date: 27-May-2023
• Revises: ISO 5068:1983 - Brown coals and lignites - Determination of moisture content - Indirect gravimetric method
• Effective Date: 15-Apr-2008

Overview

ISO 5068-2:2007 specifies an indirect gravimetric method for determining the moisture content of the analysis sample of brown coals and lignites. The method measures mass loss of a weighed test portion dried under controlled conditions (105 °C to 110 °C) in a nitrogen atmosphere and is intended for routine laboratory moisture analysis of hygroscopic brown coal and lignite samples.

Key topics and technical requirements

• Principle: Moisture is calculated from the loss in mass of an analysis sample dried to constant mass in a nitrogen‑purged oven.
• Temperature and atmosphere: Oven control between 105 °C and 110 °C with a dry, high‑purity nitrogen atmosphere (oxygen ≤ 30 µl/l).
• Nitrogen flow: Recommended flow to provide approximately 15 oven‑volume changes per hour; Annex A describes a nitrogen purification train (reduced copper at ≈ 500 °C) or the use of commercial nitrogen meeting the oxygen limit.
• Sample and sample prep: Analysis sample prepared per ISO 5069-2; typically ground to pass a 0.212 mm sieve. Test portion: 1–2 g spread so layer mass does not exceed specified limits.
• Apparatus: Sensitive balance (0.001 g resolution), shallow silica/glass weighing dish with well‑fitting lid, flow meter, drying tower with desiccant and a cooling vessel/desiccator.
• Reagents and safety: Desiccants such as magnesium perchlorate or silica gel are recommended; note hazard warning for magnesium perchlorate (strong oxidizer).
• Procedure and timing: Weigh before and after drying; dry for 3 h or until constant mass. Cool covered dish on a metal plate (≤ 5 min), then to room temperature (≈ 20 min) before final weighing.
• Expression and precision: Moisture (%) calculated from mass differences; report mean of duplicate determinations to 0.1%. Repeatability: duplicate results in same lab/operator should not differ by more than 0.3%.
• Reporting: Include sample identification, standard reference, result and expression method, and test date.

Applications and users

ISO 5068-2 is used where accurate moisture determination of brown coal and lignite analysis samples is required:

• Analytical laboratories performing proximate and ultimate coal analyses (moisture, volatile matter, calorific value, C/H).
• Power generation and coal handling facilities for quality control and fuel accounting.
• Coal producers and trading operations needing standardized moisture reporting.
• Research laboratories and regulatory bodies assessing fuel properties.

Keywords: brown coal moisture determination, lignite moisture analysis, ISO 5068-2, indirect gravimetric method, nitrogen oven, coal testing laboratories.

Related standards

• ISO 5068-1 - Indirect gravimetric method for total moisture (companion part).
• ISO 5069-2 - Sample preparation for moisture determination and general analysis.
• ISO 1213-2 - Vocabulary for sampling, testing and analysis (definitions).

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 5068-2
First edition
2007-02-01
Brown coals and lignites —
Determination of moisture content —
Part 2:
Indirect gravimetric method for moisture
in the analysis sample
Charbons bruns et lignites — Détermination de l'humidité —
Partie 2: Méthode gravimétrique indirecte pour l'humidité de l'échantillon
d'analyse
Reference number
©
ISO 2007
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ii © ISO 2007 – All rights reserved

Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Definitions . 1
4 Principle. 1
5 Reagent. 1
6 Apparatus . 2
7 Sample . 4
8 Procedure . 4
9 Expression of results . 4
10 Precision of method . 5
11 Test report . 5
Annex A (informative) Nitrogen-purification train. 6

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.
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 5068-2 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee SC 5,
Methods of analysis.
This first edition of ISO 5068-2, together with ISO 5068-1, cancels and replaces ISO 5068:1983, which has
been technically revised.
ISO 5068 consists of the following parts, under the general title Brown coals and lignites — Determination of
moisture content:
⎯ Part 1: Indirect gravimetric method for total moisture
⎯ Part 2: Indirect gravimetric method for moisture in the analysis sample

iv © ISO 2007 – All rights reserved

INTERNATIONAL STANDARD ISO 5068-2:2007(E)

Brown coals and lignites — Determination of moisture
content —
Part 2:
Indirect gravimetric method for moisture in the analysis sample
1 Scope
This International Standard specifies a method for the determination of the moisture content in the analysis
sample of brown coals and lignites using an indirect gravimetric method.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 1213-2, Solid mineral fuels — Vocabulary — Part 2: Terms relating to sampling, testing and analysis
ISO 5069-2, Brown coals and lignites — Principles of sampling — Part 2: Sample preparation for
determination of moisture content and for general analysis
3 Definitions
For the purpose of this document, the definitions given in ISO 1213-2 apply.
4 Principle
A test portion of the general analysis test sample is dried to constant mass at a temperature of 105 °C to
110 °C in an atmosphere of nitrogen. The moisture content of the analysis sample is calculated from the loss
...