ISO 6588-2:2020

INTERNATIONAL ISO
STANDARD 6588-2
Third edition
2020-03
Paper, board and pulps —
Determination of pH of aqueous
extracts —
Part 2:
Hot extraction
Papier, carton et pâtes — Détermination du pH des extraits aqueux —
Partie 2: Extraction à chaud
Reference number
ISO 6588-2:2020(E)
©
ISO 2020

---------------------- Page: 1 ----------------------
ISO 6588-2:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 6588-2:2020(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.
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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
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 6, Paper, board and pulps.
This third edition cancels and replaces the second edition (ISO 6588-2:2012), which has been technically
revised. The main changes compared to the previous edition are as follows:
— addition of the last four paragraphs in the introduction to clarify the differences, in the role and
[5]
mode of addition of a salt solution, between this document and ISO 29681 .
A list of all parts in the ISO 6588 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.
© ISO 2020 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO 6588-2:2020(E)

Introduction
Kraft fibre is well known to contain ionisable groups that are fixed to or in the fibre wall. In order to
fulfil the electro-neutrality, these groups are balanced by an equivalent number of positive charges,
which can be either protons or various metal ions. Especially in pulp suspensions at low ionic strengths,
this can give rise to a marked uneven distribution of mobile ions between the volume held by the fibre
wall and the bulk suspension liquor. This means that the fibre acts as an ion exchanger. These ion-
[2][3]
exchange phenomena can be modelled very well with the Donnan theory .
If a relatively clean pulp fibre sample, as for example bleached dried pulp, is diluted in deionised water,
the result will be a pulp suspension with a very low ionic strength. In such a system, most of the cations
present, including protons, will be concentrated in the water volume held by the fibre wall. If the pH
is measured, it will be measured in the bulk suspension liquor. By adding salt to this kind of system,
the ion exchange phenomena will be decreased and the concentration of different cations will be the
same in the water held by the fibre wall and in the bulk suspension liquor. Since the process waters
always contain a certain amount of ions, such a salt addition will give a more realistic environment
when measuring the pH of relatively clean pulp samples.
Based on the foregoing, two ISO Standards, this document and ISO 29681, are available for determination
of the pH of hot aqueous extracts of paper, board, or pulps. In ISO 29681, a salt solution is added prior
to extraction; however, in this document, the extraction is carried out with distilled or deionized water.
ISO 29681 is specifically applicable to bleached pulps from virgin fibres and to pulp samples having a
low ionic strength for which the pH-value will give more realistic results related to mill conditions than
those obtained with this document.
It is necessary to be aware that the results will not be the same when measuring pH according to this
document and to ISO 29681. The difference can be significant especially when measuring pulps having
a low ionic strength.
ISO 6588-1 differs from this document, in relation to the extraction conditions. No general guidance can
be given as to which of the two procedures (hot or cold) is best suited in a particular situation.
It should be noted that in this document, addition of a salt solution is performed after extraction and
filtration only for the purpose of obtaining a more stable and accurate pH measurement.
iv © ISO 2020 – All rights reserved

---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO 6588-2:2020(E)
Paper, board and pulps — Determination of pH of aqueous
extracts —
Part 2:
Hot extraction
1 Scope
This document specifies a method for the determination of the pH-value defined by the electrolytes
extractable by hot water from a sample of paper, board or pulp.
This document is applicable to all kinds of paper, board and pulp.
As the quantity of extractable ionic material approaches zero, as in the case of highly purified pulps,
the precision of the method becomes poor because of the difficulties encountered in making pH
measurements on water containing little electrolytic material.
Since the extraction in this document is performed with distilled or deionised water, the pH-value
measured will sometimes be different (e.g. fully bleached pulp) from the pH-value measured under
mill process conditions in which various types of process waters, e.g. chemically treated river water
containing electrolytes, are used. In such cases, ISO 29681 can be used instead, as it is specifically
applicable to bleached pulps from virgin fibres and to pulp samples having a low ionic strength for
which the pH value will give more realistic results related to mill conditions than those obtained with
this document. For cellulosic papers used for electrical purposes, the method used can be that given in
[4]
IEC 60554-2 .
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 186, Paper and board — Sampling to determine average quality
ISO 7213, Pulps — Sampling for testing
3 Terms and definitions
No terms and definitions are listed in this document.
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 http:// www .electropedia .org/
4 Principle
Extraction of a sample of 2 g for 1 h with 100 ml of boiling water of high purity. Filtration of the extract
and addition of a salt solution. Measurement of the pH-value of the extract at a temperature between
20 °C and 25 °C.
© ISO 2020 – All rights reserved 1

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ISO 6588-2:2020(E)

5 Reagents
5.1 Water, distilled or deionised water shall be used throughout the test. The conductivity of the water
shall not exceed 0,1 mS/m after boiling for 1 h and cooling in an acid-free atmosphere (e.g. free of CO ,
2
SO , H S) to a temperature between 20 °C and 25 °C. The pH of the water should be in the range of 6,8 to
2 2
7,3. Instructions for the determination of conductivity are specified in ISO 3696.
5.2 Standard buffer solutions, with known pH-values of about 4, 7 and 9. Such buffer solutions are
commercially available. Some examples of suitable buffer solutions are given, and their preparation is
described, in Annex A.
5.3 Potassium chloride solution, 1
...

NORME ISO
INTERNATIONALE 6588-2
Troisième édition
2020-03
Papier, carton et pâtes —
Détermination du pH des extraits
aqueux —
Partie 2:
Extraction à chaud
Paper, board and pulps — Determination of pH of aqueous extracts —
Part 2: Hot extraction
Numéro de référence
ISO 6588-2:2020(F)
©
ISO 2020

---------------------- Page: 1 ----------------------
ISO 6588-2:2020(F)

DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2020
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
Case postale 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Genève
Tél.: +41 22 749 01 11
Fax: +41 22 749 09 47
E-mail: copyright@iso.org
Web: www.iso.org
Publié en Suisse
ii © ISO 2020 – Tous droits réservés

---------------------- Page: 2 ----------------------
ISO 6588-2:2020(F)

Sommaire Page
Avant-propos .iv
Introduction .v
1 Domaine d'application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Principe . 2
5 Réactifs . 2
6 Appareillage et équipement . 2
7 Échantillonnage et préparation de l’échantillon . 2
7.1 Échantillonnage . 2
7.2 Préparation de l’échantillon . 2
8 Mode opératoire. 3
8.1 Pesée . 3
8.2 Extraction . 3
8.3 Détermination du pH . 3
9 Calcul . 3
10 Rapport d’essai . 4
Annexe A (informative) Préparation de solutions tampons étalons . 5
Annexe B (informative) Fidélité. 6
Bibliographie . 8
© ISO 2020 – Tous droits réservés iii

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ISO 6588-2:2020(F)

Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes
nationaux de normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est
en général confiée aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude
a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,
gouvernementales et non gouvernementales, en liaison avec l'ISO participent également aux travaux.
L'ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui
concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents
critères d'approbation requis pour les différents types de documents ISO. Le présent document a été
rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www
.iso .org/ directives).
L'attention est attirée sur le fait que certains des éléments du présent document peuvent faire l'objet de
droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable
de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant
les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de
l'élaboration du document sont indiqués dans l'Introduction et/ou dans la liste des déclarations de
brevets reçues par l'ISO (voir www .iso .org/ brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion
de l'ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles
techniques au commerce (OTC), voir www .iso .org/ avant -propos.
Le présent document a été élaboré par le comité technique ISO/TC 6, Papiers, cartons et pâtes.
Cette troisième édition annule et remplace la deuxième édition (ISO 6588-2:2012) qui a fait l’objet d’une
révision technique. Les principales modifications par rapport à l’édition précédente sont les suivantes:
— ajout des quatre derniers paragraphes dans l’introduction afin de clarifier les différences, en termes
[5]
de rôle et de mode d’ajout d’une solution saline, entre la présente norme et l’ISO 29681 .
Une liste de toutes les parties de la série ISO 6588 se trouve sur le site web de l’ISO.
Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent
document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes
se trouve à l’adresse www .iso .org/ fr/ members .html.
iv © ISO 2020 – Tous droits réservés

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ISO 6588-2:2020(F)

Introduction
Il est bien connu que la fibre kraft contient des groupes ionisables qui sont fixés sur ou dans la paroi
de la fibre. Afin de satisfaire l’électroneutralité, ces groupes sont équilibrés par un nombre égal de
charges positives, qui peuvent être des protons ou des ions métalliques divers. En particulier dans les
suspensions de pâtes de faible concentration ionique, cela peut mener à une distribution inégale des
ions mobiles entre le volume emprisonné dans la paroi de la fibre et le reste de la suspension. Cela
signifie que les fibres agissent comme un échangeur d’ions. Ces phénomènes d’échange d’ions peuvent
[2][3]
être très bien modélisés à l’aide de la théorie de Donnan .
Si un échantillon de fibres d’une pâte relativement propre, par exemple une pâte blanchie et séchée,
est dilué dans de l’eau désionisée, le résultat sera une suspension de pâte de très faible concentration
ionique. Dans un tel système, la plupart des cations présents, y compris les protons, sont concentrés
dans un volume d’eau retenu par la paroi de la fibre. Si le pH est mesuré, il s’agit du pH de la pâte
environnante. En ajoutant un sel à ce type de système, le phénomène d’échange d’ions est diminué et
la concentration des différents cations sera identique dans l’eau emprisonnée par la paroi de la fibre
et le reste de la pâte en suspension. Puisque les eaux de procédés contiennent toujours une certaine
quantité d’ions, un tel ajout d’un sel résultera en un environnement plus réaliste lors de la mesure du pH
d’échantillons de pâtes relativement propres.
Sur la base de ce qui précède, deux normes ISO, le présent document et l’ISO 29681 sont disponibles pour
la détermination du pH des extraits aqueux à chaud de papier, de carton ou de pâtes. Dans l’ISO 29681,
une solution saline est ajoutée avant l’extraction; toutefois, dans le présent document, l’extraction est
réalisée avec de l’eau distillée ou désionisée. L’ISO 29681 s’applique spécifiquement aux pâtes blanchies
à partir de fibres vierges et aux échantillons de pâtes de faible concentration ionique dont les conditions
de pH lors du procédé industriel conduiront à des résultats plus réalistes que ceux obtenus avec le
présent document.
Il est nécessaire d’avoir conscience du fait que les résultats obtenus en mesurant le pH conformément
au présent document seront différents de ceux obtenus à l’aide de l’ISO 29681. Ces différences peuvent
être significatives, notamment lors d’un mesurage sur des pâtes de faible concentration ionique.
L’ISO 6588-1 diffère du présent document en matière de conditions d’extraction. Aucune ligne directrice
générale ne peut être donnée concernant le mode opératoire le plus adapté (extraction à chaud ou à
froid) en fonction d’une situation donnée.
Il convient de noter que dans le présent document, l’ajout d’une solution saline est effectué après
extraction et filtration uniquement dans le but d’obtenir une mesure plus stable et exacte du pH.
© ISO 2020 – Tous droits réservés v

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NORME INTERNATIONALE ISO 6588-2:2020(F)
Papier, carton et pâtes — Détermination du pH des extraits
aqueux —
Partie 2:
Extraction à chaud
1 Domaine d'application
Le présent document spécifie une méthode pour la détermination du pH défini par les électrolytes
extractibles d’un échantillon de papier, de carton ou de pâte, par de l’eau chaude.
Le présent document est applicable à tous les types de papiers, de cartons et de pâtes.
Comme la quantité de matériau ionique extractible approche zéro, comme dans le cas des pâtes
hautement purifiées, la précision de la méthode devient mauvaise à cause des difficultés à réaliser les
mesurages de pH dans de l’eau contenant une faible quantité de matériau électrolytique.
Puisque, dans le présent document, l’extraction est effectuée avec de l’eau distillée ou désionisée, le pH
mesuré est parfois différent (par exemple pour une pâte hautement blanchie) de celui mesuré dans les
conditions mises en œuvre pendant le procédé industriel lors duquel différents types d’eaux de procédé
sont utilisés, par exemple de l’eau de rivière traitée chimiquement contenant des électrolytes. Dans de
tels cas, l'ISO 29681 peut être préférée car, étant spécialement conçue pour les pâ
...

SLOVENSKI STANDARD
oSIST ISO 6588-2:2020
01-oktober-2020
Papir, karton, lepenka in vlaknine - Določanje vrednosti pH vodnih ekstraktov - 2.
del: Ekstrakcija v vročem
Paper, board and pulps -- Determination of pH of aqueous extracts -- Part 2: Hot
extraction
Papier, carton et pâtes -- Détermination du pH des extraits aqueux
Ta slovenski standard je istoveten z: ISO 6588-2:2020
ICS:
85.040 Vlaknine Pulps
85.060 Papir, karton in lepenka Paper and board
oSIST ISO 6588-2:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST ISO 6588-2:2020

---------------------- Page: 2 ----------------------
oSIST ISO 6588-2:2020
INTERNATIONAL ISO
STANDARD 6588-2
Third edition
2020-03
Paper, board and pulps —
Determination of pH of aqueous
extracts —
Part 2:
Hot extraction
Papier, carton et pâtes — Détermination du pH des extraits aqueux —
Partie 2: Extraction à chaud
Reference number
ISO 6588-2:2020(E)
©
ISO 2020

---------------------- Page: 3 ----------------------
oSIST ISO 6588-2:2020
ISO 6588-2:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

---------------------- Page: 4 ----------------------
oSIST ISO 6588-2:2020
ISO 6588-2:2020(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.
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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
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 6, Paper, board and pulps.
This third edition cancels and replaces the second edition (ISO 6588-2:2012), which has been technically
revised. The main changes compared to the previous edition are as follows:
— addition of the last four paragraphs in the introduction to clarify the differences, in the role and
[5]
mode of addition of a salt solution, between this document and ISO 29681 .
A list of all parts in the ISO 6588 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.
© ISO 2020 – All rights reserved iii

---------------------- Page: 5 ----------------------
oSIST ISO 6588-2:2020
ISO 6588-2:2020(E)

Introduction
Kraft fibre is well known to contain ionisable groups that are fixed to or in the fibre wall. In order to
fulfil the electro-neutrality, these groups are balanced by an equivalent number of positive charges,
which can be either protons or various metal ions. Especially in pulp suspensions at low ionic strengths,
this can give rise to a marked uneven distribution of mobile ions between the volume held by the fibre
wall and the bulk suspension liquor. This means that the fibre acts as an ion exchanger. These ion-
[2][3]
exchange phenomena can be modelled very well with the Donnan theory .
If a relatively clean pulp fibre sample, as for example bleached dried pulp, is diluted in deionised water,
the result will be a pulp suspension with a very low ionic strength. In such a system, most of the cations
present, including protons, will be concentrated in the water volume held by the fibre wall. If the pH
is measured, it will be measured in the bulk suspension liquor. By adding salt to this kind of system,
the ion exchange phenomena will be decreased and the concentration of different cations will be the
same in the water held by the fibre wall and in the bulk suspension liquor. Since the process waters
always contain a certain amount of ions, such a salt addition will give a more realistic environment
when measuring the pH of relatively clean pulp samples.
Based on the foregoing, two ISO Standards, this document and ISO 29681, are available for determination
of the pH of hot aqueous extracts of paper, board, or pulps. In ISO 29681, a salt solution is added prior
to extraction; however, in this document, the extraction is carried out with distilled or deionized water.
ISO 29681 is specifically applicable to bleached pulps from virgin fibres and to pulp samples having a
low ionic strength for which the pH-value will give more realistic results related to mill conditions than
those obtained with this document.
It is necessary to be aware that the results will not be the same when measuring pH according to this
document and to ISO 29681. The difference can be significant especially when measuring pulps having
a low ionic strength.
ISO 6588-1 differs from this document, in relation to the extraction conditions. No general guidance can
be given as to which of the two procedures (hot or cold) is best suited in a particular situation.
It should be noted that in this document, addition of a salt solution is performed after extraction and
filtration only for the purpose of obtaining a more stable and accurate pH measurement.
iv © ISO 2020 – All rights reserved

---------------------- Page: 6 ----------------------
oSIST ISO 6588-2:2020
INTERNATIONAL STANDARD ISO 6588-2:2020(E)
Paper, board and pulps — Determination of pH of aqueous
extracts —
Part 2:
Hot extraction
1 Scope
This document specifies a method for the determination of the pH-value defined by the electrolytes
extractable by hot water from a sample of paper, board or pulp.
This document is applicable to all kinds of paper, board and pulp.
As the quantity of extractable ionic material approaches zero, as in the case of highly purified pulps,
the precision of the method becomes poor because of the difficulties encountered in making pH
measurements on water containing little electrolytic material.
Since the extraction in this document is performed with distilled or deionised water, the pH-value
measured will sometimes be different (e.g. fully bleached pulp) from the pH-value measured under
mill process conditions in which various types of process waters, e.g. chemically treated river water
containing electrolytes, are used. In such cases, ISO 29681 can be used instead, as it is specifically
applicable to bleached pulps from virgin fibres and to pulp samples having a low ionic strength for
which the pH value will give more realistic results related to mill conditions than those obtained with
this document. For cellulosic papers used for electrical purposes, the method used can be that given in
[4]
IEC 60554-2 .
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 186, Paper and board — Sampling to determine average quality
ISO 7213, Pulps — Sampling for testing
3 Terms and definitions
No terms and definitions are listed in this document.
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 http:// www .electropedia .org/
4 Principle
Extraction of a sample of 2 g for 1 h with 100 ml of boiling water of high purity. Filtration of the extract
and addition of a salt solution. Measurement of the pH-value of the extract at a temperature between
20 °C and 25 °C.
© ISO 2020 – All rights reserved 1

---------------------- Page: 7 ----------------------
oSIST ISO 6588-2:2020
ISO 6588-2:2020(E)

5 Reagents
5.1 Water, distilled or deionised water shall be used throughout the test. The conductivity of the water
shall not exceed 0,1 mS/m after boiling for 1 h and cooling in an acid-free atmosphere (e.g. free of CO ,
2
...