ISO 5068-1:2007

INTERNATIONAL ISO
STANDARD 5068-1
First edition
2007-02-01

Brown coals and lignites —
Determination of moisture content —
Part 1:
Indirect gravimetric method for total
moisture
Charbons bruns et lignites — Détermination de l'humidité —
Partie 1: Méthode gravimétrique indirecte pour l'humidité totale




Reference number
ISO 5068-1:2007(E)
©
ISO 2007

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ISO 5068-1:2007(E)
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ISO 5068-1:2007(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Definitions . 1
4 Principle. 1
5 Reagent. 2
6 Apparatus . 2
7 Sample . 4
8 Procedure . 4
9 Expression of results . 5
10 Precision of method . 6
11 Test report . 7
Annex A (informative) Nitrogen-purification train. 8

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ISO 5068-1:2007(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.
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 5068-1 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee SC 5,
Methods of analysis.
This first edition of ISO 5068-1, together with ISO 5068-2, 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

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INTERNATIONAL STANDARD ISO 5068-1:2007(E)

Brown coals and lignites — Determination of moisture
content —
Part 1:
Indirect gravimetric method for total moisture
1 Scope
This International Standard specifies two methods for determination of the total moisture content of brown
coals and lignites using an indirect gravimetric single-stage method and a two-stage 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 purposes of this document, the definitions given in ISO 1213-2 apply.
4 Principle
4.1 Single-stage method
A sample, prepared using a closed mill, is dried to constant mass at a temperature of 105 °C to 110 °C in an
atmosphere of nitrogen, and the total moisture content is calculated from the loss in mass of the sample.
4.2 Two-stage method
A sample is coarsely ground and is then allowed to dry, either at ambient temperature or at a higher
temperature not exceeding 40 °C, to reach equilibrium with the atmosphere. The sample is further crushed
and then dried to a constant mass at a temperature of 105 °C to 110 °C in an atmosphere of nitrogen. The
total moisture content is calculated from the losses in mass during the two drying stages.
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ISO 5068-1:2007(E)
5 Reagent
5.1 Desiccant, fresh or freshly regenerated and preferably self-indicating.
Suitable desiccants are magnesium perchlorate and silica gel.
WARNING — Magnesium perchlorate is a strong oxidizing agent. Do no attempt to regenerate the
absorbent. Do not permit contact with organic materials or reducing agent.
5.2 Nitrogen, high-purity, dry with a maximum oxygen content of 30 µl/l.
NOTE Commercial nitrogen of this purity is available. See Annex A for details.
6 Apparatus
6.1 Oven, nitrogen-flushed, capable of being controlled by a temperature of 105 °C to 110 °C and with the
additional provision for passing a current of dry nitrogen through it at a flow rate about 15 times the oven
volume per hour.
Before using a new oven, carry out a temperature profile through the interior and take care to insert samples
only where the temperature is known to be 105 °C to 110 °C.
A suitable oven is illustrated in Figure 1.
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ISO 5068-1:2007(E)
Dimensions in millimetres

Key
1 nitrogen outlet 3 thermometer tube
2 space for heating element 4 copper gauze, having apertures of nominal size 0,25
Figure 1 — Typical nitrogen oven
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ISO 5068-1:2007(E)
6.2 Drying cabinet, capable of being controlled at a temperature of 30 °C to 40 °C and with provision for
venti
...