Brown coals and lignites -- Determination of humic acids

This document specifies volumetric methods for the determination of total humic acids and free humic acid of brown coals and lignites.

Charbons bruns et lignites -- Dosage des acides humiques

General Information

Status
Published
Publication Date
08-Dec-2021
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
11-Nov-2021
Completion Date
10-Nov-2021
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INTERNATIONAL ISO
STANDARD 5073
Fourth edition
2021-12
Brown coals and lignites —
Determination of humic acids
Charbons bruns et lignites — Dosage des acides humiques
Reference number
ISO 5073:2021(E)
© ISO 2021
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ISO 5073:2021(E)
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© ISO 2021 – All rights reserved
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ISO 5073:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 2

4.1 Total humic acids .................................................................................................................................................................................. 2

4.2 Free humic acid ...................................................................................................................................................................................... 2

5 Reagents ........................................................................................................................................................................................................................ 2

6 Apparatus .................................................................................................................................................................................................................... 3

7 Sample ............................................................................................................................................................................................................................. 3

8 Procedure ....................................................................................................................................................................................................................3

8.1 Extraction of total humic acids ................................................................................................................................................ 3

8.2 Extraction of free humic acid .................................................................................................................................................... 3

8.3 Determination of humic acids in extracts ...................................................................................................................... 4

8.3.1 For total humic acids ...................................................................................................................................................... 4

8.3.2 For free humic acids ........................................................................................................................................................ 4

9 Calculation and expression of results ........................................................................................................................................... 4

10 Precision ....................................................................................................................................................................................................................... 5

10.1 Repeatability limit ............................................................................................................................................................................... 5

11 Test report .................................................................................................................................................................................................................. 5

Annex A (normative) Determination of the ratio of carbon mass fraction to humic acids

mass fraction of brown coals and lignites ................................................................................................................................ 6

iii
© ISO 2021 – All rights reserved
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ISO 5073:2021(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

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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.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

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expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.

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 5073:2013), of which it constitutes a

minor revision. The changes compared to the previous edition are as follows:
— referenced documents have been updated;
— terms and definitions have been added;
— sample has been added;
— determination of humic acids in extracts has been amended;
— calculation and expression of results have been amended;
— precision has been amended;
— test report has been amended;
— Annex A has been amended.

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
© ISO 2021 – All rights reserved
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ISO 5073:2021(E)
Introduction

In this document, humic acids are determined by the volumetric method with titration of extracts.

The test is empirical and, in order to ensure reproducible results, it is essential that the composition of

the extraction solution, the temperature and the time of extraction be carefully controlled. The value

0,59, which is the average ratio of carbon content of humic acids for many brown coals and lignites, has

been proved to be applicable. Another value may also be used, predetermined as described in Annex A,

and applicable to different countries or locations.
© ISO 2021 – All rights reserved
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INTERNATIONAL STANDARD ISO 5073:2021(E)
Brown coals and lignites — Determination of humic acids
1 Scope

This document specifies volumetric methods for the determination of total humic acids and free humic

acid of brown coals and lignites.
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 1171, Solid mineral fuels — Determination of ash

ISO 1213-2, Solid mineral fuels — Vocabulary — Part 2: Terms relating to sampling, testing and analysis

ISO 5068-2, Brown coals and lignites — Determination of moisture content — Part 2: Indirect gravimetric

method for moisture in the analysis sample

ISO 13909-4, Hard coal and coke — Mechanical sampling — Part 4: Coal — Preparation of test samples

ISO 18283, Coal and coke — Manual sampling
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 1213-2 and the following

apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
humic acids

group of complex organic, amorphous compounds of high relative molecular mass which occur as free

acid and as metal salts (humates)
3.2
total humic acids
humic acids (3.1) extracted by an alkaline sodium pyrophosphate solution
3.3
free humic acid
humic acid (3.1) extracted by a sodium hydroxide solution
© ISO 2021 – All rights reserved
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ISO 5073:2021(E)
4 Principle
4.1 Total humic acids

Extraction of an analysis sample of coal is carried out with an alkaline sodium pyrophosphate solution.

Carbon in the humic acid extracts is oxidized with potassium dichromate followed by titration of the

excess dichromate with ammonium ferrous sulfate standard solution.
4.2 Free humic acid

Extraction of an analysis sample of coal is carried out with a sodium hydroxide solution. Carbon in

the humic acid extracts is oxidized with potassium dichromate followed by titration of the excess

dichromate with ammonium ferrous sulfate standard solution.
5 Reagents
5.1 Sodium pyrophosphate, alkaline extraction solution.

Dissolve 15 g of crystalline sodium pyrophosphate (Na P O ·10H O) and 7 g of sodium hydroxide in 1 l

4 2 7 2
of water.
5.2 Sodium hydroxide solution.
Dissolve 10 g of sodium hydroxide in 1 l of water.
5.3 Potassium dichromate standard solution, c(1/6 K Cr O ) = 0,1 mol/l.
2 2 7

Dissolve 4,903 6 g of potassium dichromate, previously dried at 130 °C, in water. Transfer to a 1 l

volumetric flask and dilute to the mark with water.
5.4 Potassium dichromate oxidizing solution, c(1/6 K Cr O ) = 0,4 mol/l.
2 2 7
Dissolve 20 g of potassium dichromate in 1 l of water.
5.5 Ammo
...

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