ISO 5068-2:2025

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

This document specifies a method for the determination of the moisture 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: 04-May-2025
• ICS: 73.040 - Coals
• Technical Committee: ISO/TC 27/SC 5 - Methods of analysis
• Drafting Committee: ISO/TC 27/SC 5 - Methods of analysis
• Current Stage: 6060 - International Standard published
• Start Date: 05-May-2025
• Due Date: 20-May-2026
• Completion Date: 05-May-2025

Relations

• Revises: ISO 5068-2:2007 - Brown coals and lignites - Determination of moisture content - Part 2: Indirect gravimetric method for moisture in the analysis sample
• Effective Date: 27-May-2023

Overview

ISO 5068-2:2025 specifies an indirect gravimetric method for the determination of moisture in the analysis sample of brown coals and lignites. The method measures moisture by drying a representative test portion and calculating the moisture mass fraction from the mass loss. It is intended for laboratory analysis where precise moisture values are needed for subsequent testing (volatile matter, calorific value, C/H analysis, etc.).

Key topics and technical requirements

• Test principle: Loss in mass of a test portion dried to constant mass at 105 °C to 110 °C in a nitrogen atmosphere.
• Sample size and preparation: Typical test portion is 1 g to 2 g, ground to pass a 0.212 mm sieve and prepared according to ISO 18283 or ISO 13909-4.
• Atmosphere and gas purity: Dry high‑purity nitrogen with a maximum oxygen content of 30 µl/l; nitrogen flow providing about 15 oven-volume changes per hour. Annex A describes a nitrogen purification train option.
• Apparatus: Minimum free-volume nitrogen oven, shallow silica/glass dish with fitted lid, balance sensitive to 0.0001 g, flow meter, drying tower (magnesium perchlorate or silica gel) and a cooling vessel/desiccator.
• Drying end point: Constant mass defined as successive mass losses of less than 0.001 g; use the higher loss for calculations.
• Calculation and reporting: Moisture mass fraction calculated from initial and final masses; report the arithmetic mean of duplicate determinations to the nearest 0.1%.
• Repeatability: Duplicate determinations by the same operator/apparatus should not differ by more than 0.3% (absolute).
• Safety/chemicals: Desiccants such as magnesium perchlorate and silica gel recommended; note safety warning for magnesium perchlorate (strong oxidizer).

Applications and users

• Laboratories performing routine coal and lignite analysis (QA/QC, research, energy content determination).
• Coal testing facilities and utilities calculating calorific value and composition where accurate moisture correction is required.
• Producers and trading organizations requiring consistent moisture measurement for specification, billing, and compliance.
• Environmental and materials testing labs where hygroscopic behavior of brown coals and lignites affects downstream analyses.

Related standards

• ISO 18283 - Manual sampling of coal (sample preparation referenced).
• ISO 13909-4 - Mechanical sampling and preparation of test samples.
• ISO 1213-2 - Vocabulary for sampling, testing and analysis (terms and definitions used).

Keywords: ISO 5068-2:2025, brown coals, lignites, moisture determination, indirect gravimetric method, nitrogen oven, sample preparation, coal analysis, repeatability limit.

Standards Content (Sample)

International
Standard
ISO 5068-2
Second edition
Brown coals and lignites —
2025-05
Determination of moisture —
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 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagent . 1
6 Apparatus . 2
7 Sample . 4
8 Procedure . 4
9 Expression of results . 4
10 Repeatability limit . 5
11 Test report . 5
Annex A (informative) Nitrogen-purification train . 6

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 second edition cancels and replaces the first edition (ISO 5068-2:2007), which has been technically
revised.
The main changes are as follows:
— referenced documents have been updated;
— terms and definitions have been updated;
— the test report has been updated.
A list of all parts in the ISO 5068 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
International Standard ISO 5068-2:2025(en)
Brown coals and lignites — Determination of moisture —
Part 2:
Indirect gravimetric method for moisture in the analysis sample
1 Scope
This document specifies a method for the determination of the moisture in the analysis sample of brown
coals and lignites using an indirect gravimetric method.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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, Coal and coke — Vocabulary — Part 2: Terms relating to sampling, testing and analysis
ISO 13909-4, Coal and coke — Mechanical sampling — Part 4: Preparation of test samples of coal
ISO 18283, Coal and coke — Manual sampling
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 1213-2 apply.
ISO and IEC maintain
...