SIST ISO 6588-1:2023

Paper, board and pulps — Determination of pH of aqueous extracts — Part 1: Cold extraction

This document specifies a method for the determination of the pH-value defined by the electrolytes extractable by cold water from a sample of paper, board or pulp.
This document is applicable to all types 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 can sometimes be different (e.g. for fully bleached pulp) from the pH-value measured under mill process conditions, in which various types of process waters, such as 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 gives 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 IEC 60554‑2[5].

Papier, carton et pâtes — Détermination du pH des extraits aqueux — Partie 1: Extraction à froid

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 froide.
Ce document est applicable à tous les types de papiers, de cartons et de pâtes.
Lorsque la quantité de substance ionique extractible est presque nulle, comme dans le cas des pâtes hautement purifiées, la fidélité de la méthode devient mauvaise en raison des difficultés rencontrées lors de la réalisation des mesurages de pH d’une eau contenant peu de substances électrolytiques.
Puisque, dans ce document, l’extraction est effectuée avec de l’eau distillée ou désionisée, le pH mesuré peut parfois être 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 process sont utilisés, comme 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 pâtes blanchies issues de fibres vierges et pour les échantillons de pâte à faible concentration ionique, elle produit des valeurs de pH plus réalistes que le présent document.
Pour les papiers cellulosiques à usages électriques, la méthode indiquée dans la norme IEC 60554-2[5] peut être utilisée.

Papir, karton, lepenka in vlaknine - Določanje vrednosti pH vodnih ekstraktov - 1. del: Ekstrakcija v hladnem

Ta dokument opisuje metodo za določanje vrednosti pH na podlagi elektrolitov, ki jih je mogoče v hladni vodi ekstrahirati iz vzorca papirja, kartona, lepenke ali vlaknin.
Ta dokument se uporablja za vse vrste papirja, kartona, lepenke in vlaknin.
Metoda je manj natančna, če je količina ionskih snovi, ki jih je mogoče ekstrahirati, zanemarljiva (npr. v primeru zelo prečiščenih vlaknin), ker se pri merjenju vrednosti pH vode, ki vsebuje majhne količine elektrolitov, pojavljajo težave.
Ker se ekstrakcija iz tega dokumenta izvaja z destilirano ali deionizirano vodo, se lahko izmerjena vrednost pH v nekaterih primerih (npr. pri popolnoma pobeljenih vlakninah) razlikuje od vrednosti pH, izmerjene pod pogoji postopkov v papirnici, pri katerih se uporabljajo različne tehnološke vode, npr. kemično obdelana rečna voda, ki vsebuje elektrolite. V teh primerih je mogoče uporabiti standard ISO 29681, saj se uporablja posebej za pobeljene vlaknine iz primarnih vlaken in za vzorce vlaknin z nizko ionsko močjo, za katere vrednost pH daje realnejše rezultate v zvezi s pogoji v papirnici od tistih, pridobljenih z uporabo tega dokumenta.
Za celulozni papir za elektrotehnične namene je mogoče uporabiti metodo iz standarda IEC 60554‑2[5].

General Information

• Status: Published
• Publication Date: 07-Jun-2023
• ICS: 85.040 - Pulps
• ICS: 85.060 - Paper and board
• Technical Committee: VPK - Pulp, paper, board and products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 11-May-2023
• Due Date: 16-Jul-2023
• Completion Date: 08-Jun-2023
• Ref Project: ISO 6588-1:2021 - Paper, board and pulps — Determination of pH of aqueous extracts — Part 1: Cold extraction

Relations

• Revises: SIST ISO 6588-1:2020 - Paper, board and pulps -- Determination of pH of aqueous extracts -- Part 1: Cold extraction
• Effective Date: 01-Jul-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST ISO 6588-1:2023
01-julij-2023
Papir, karton, lepenka in vlaknine - Določanje vrednosti pH vodnih ekstraktov - 1.
del: Ekstrakcija v hladnem
Paper, board and pulps — Determination of pH of aqueous extracts — Part 1: Cold
extraction
Papier, carton et pâtes — Détermination du pH des extraits aqueux — Partie 1:
Extraction à froid
Ta slovenski standard je istoveten z: ISO 6588-1:2021
ICS:
85.040 Vlaknine Pulps
85.060 Papir, karton in lepenka Paper and board
SIST ISO 6588-1:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 6588-1:2023

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SIST ISO 6588-1:2023
INTERNATIONAL ISO
STANDARD 6588-1
Fourth edition
2021-11
Paper, board and pulps —
Determination of pH of aqueous
extracts —
Part 1:
Cold extraction
Papier, carton et pâtes — Détermination du pH des extraits aqueux —
Partie 1: Extraction à froid
Reference number
ISO 6588-1:2021(E)
© ISO 2021

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SIST ISO 6588-1:2023
ISO 6588-1:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2021 – All rights reserved

---------------------- Page: 4 ----------------------
SIST ISO 6588-1:2023
ISO 6588-1:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus and equipment . 2
7 Sampling and preparation of sample .2
7.1 Sampling . 2
7.2 Preparation of sample . 2
8 Procedure .2
8.1 General . 2
8.2 Weighing . 3
8.3 Extraction . 3
8.4 Determination of pH . 3
9 Calculation . 3
10 Test report . 3
Annex A (informative) Preparation of some standard buffer solutions . 5
Annex B (informative) Precision . 6
Bibliography . 7
iii
© ISO 2021 – All rights reserved

---------------------- Page: 5 ----------------------
SIST ISO 6588-1:2023
ISO 6588-1:2021(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
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 fourth edition cancels and replaces the third edition (ISO 6588-1:2020), of which it constitutes a
minor revision. The changes compared to the previous edition are as follows:
— clause references in 7.1, 8.1 and Clause 10 d) have been corrected.
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.
iv
  © ISO 2021 – All rights reserved

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SIST ISO 6588-1:2023
ISO 6588-1:2021(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-
[6][7]
exchange phenomena can be modelled very well with the Donnan theory .
If a relatively clean pulp fibre sample, 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 is measured in the bulk suspension liquor. By adding salt to this kind of system, the ion
exchange phenomena is 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 gives a more realistic environment when measuring the
pH of relatively clean pulp samples.
Based on the foregoing, two ISO Standards (ISO 6588-1 and ISO 29681) are available for determination
of the pH of cold aqueous extracts of paper, board, or pulps. In ISO 29681, a salt solution is added prior
to extraction; however, in ISO 6588-1, 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 gives more realistic results related to mill conditions than
those obtained with ISO 6588-1.
It is necessary to be aware that the results will not be the same when measuring pH according to
ISO 6588-1 and to ISO 29681. The difference can be significant especially when measuring pulps having
a low ionic strength.
ISO 6588-2 differs from this document only as regards 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 ISO 6588-1, addition of a salt solution is performed after extraction and
filtration only for the purpose of obtaining a more stable and accurate pH measurement.
v
© ISO 2021 – All rights reserved

---------------------- Page: 7 ----------------------
SIST ISO 6588-1:2023

---------------------- Page: 8 ----------------------
SIST ISO 6588-1:2023
INTERNATIONAL STANDARD ISO 6588-1:2021(E)
Paper, board and pulps — Determination of pH of aqueous
extracts —
Part 1:
Cold extraction
1 Scope
This document specifies a method for the determination of the pH-value defined by the electrolytes
extractable by cold water from a sample of paper, board or pulp.
This document is applicable to all types of paper, board and pulp.
As the quantity of extractable ion
...

INTERNATIONAL ISO
STANDARD 6588-1
Fourth edition
2021-11
Paper, board and pulps —
Determination of pH of aqueous
extracts —
Part 1:
Cold extraction
Papier, carton et pâtes — Détermination du pH des extraits aqueux —
Partie 1: Extraction à froid
Reference number
ISO 6588-1:2021(E)
© ISO 2021

---------------------- Page: 1 ----------------------
ISO 6588-1:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 6588-1:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus and equipment . 2
7 Sampling and preparation of sample .2
7.1 Sampling . 2
7.2 Preparation of sample . 2
8 Procedure .2
8.1 General . 2
8.2 Weighing . 3
8.3 Extraction . 3
8.4 Determination of pH . 3
9 Calculation . 3
10 Test report . 3
Annex A (informative) Preparation of some standard buffer solutions . 5
Annex B (informative) Precision . 6
Bibliography . 7
iii
© ISO 2021 – All rights reserved

---------------------- Page: 3 ----------------------
ISO 6588-1:2021(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
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 fourth edition cancels and replaces the third edition (ISO 6588-1:2020), of which it constitutes a
minor revision. The changes compared to the previous edition are as follows:
— clause references in 7.1, 8.1 and Clause 10 d) have been corrected.
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.
iv
  © ISO 2021 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 6588-1:2021(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-
[6][7]
exchange phenomena can be modelled very well with the Donnan theory .
If a relatively clean pulp fibre sample, 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 is measured in the bulk suspension liquor. By adding salt to this kind of system, the ion
exchange phenomena is 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 gives a more realistic environment when measuring the
pH of relatively clean pulp samples.
Based on the foregoing, two ISO Standards (ISO 6588-1 and ISO 29681) are available for determination
of the pH of cold aqueous extracts of paper, board, or pulps. In ISO 29681, a salt solution is added prior
to extraction; however, in ISO 6588-1, 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 gives more realistic results related to mill conditions than
those obtained with ISO 6588-1.
It is necessary to be aware that the results will not be the same when measuring pH according to
ISO 6588-1 and to ISO 29681. The difference can be significant especially when measuring pulps having
a low ionic strength.
ISO 6588-2 differs from this document only as regards 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 ISO 6588-1, addition of a salt solution is performed after extraction and
filtration only for the purpose of obtaining a more stable and accurate pH measurement.
v
© ISO 2021 – All rights reserved

---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 6588-1:2021(E)
Paper, board and pulps — Determination of pH of aqueous
extracts —
Part 1:
Cold extraction
1 Scope
This document specifies a method for the determination of the pH-value defined by the electrolytes
extractable by cold water from a sample of paper, board or pulp.
This document is applicable to all types 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 can sometimes be different (e.g. for fully bleached pulp) from the pH-value measured under
mill process conditions, in which various types of process water
...

NORME ISO
INTERNATIONALE 6588-1
Quatrième édition
2021-11
Papier, carton et pâtes —
Détermination du pH des extraits
aqueux —
Partie 1:
Extraction à froid
Paper, board and pulps — Determination of pH of aqueous extracts —
Part 1: Cold extraction
Numéro de référence
ISO 6588-1:2021(F)
© ISO 2021

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ISO 6588-1:2021(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2021
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.: [phone]
E-mail: [e-mail]
Web: www.iso.org
Publié en Suisse
ii
  © ISO 2021 – Tous droits réservés

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ISO 6588-1:2021(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 Généralités . 3
8.2 Pesée . 3
8.3 Extraction . 3
8.4 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
iii
© ISO 2021 – Tous droits réservés

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ISO 6588-1:2021(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 quatrième édition annule et remplace la troisième édition (ISO 6588-1:2020), dont elle constitue
une révision mineure. Les modifications sont les suivantes:
— les références dans les paragraphes 7.1, 8.1 et dans l’alinéa d) de l’Article 10 ont été corrigées.
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 2021 – Tous droits réservés

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ISO 6588-1:2021(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
[6], [7]
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, ainsi que 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 résulte 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, l’ISO 6588-1 et l’ISO 29681, sont disponibles pour la
détermination du pH des extraits aqueux à froid de papier, de carton ou de pâtes. Dans l’ISO 29681, une
solution saline est ajoutée avant l’extraction; toutefois, dans l’ISO 6588-1, 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 conduisent à des résultats plus réalistes que ceux obtenus avec l’ISO 6588-1.
Il est nécessaire d’avoir conscience du fait que les résultats obtenus en mesurant le pH conformément
à l’ISO 6588-1 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 6588-2 ne diffère du présent document qu’au sujet des 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 l’ISO 6588-1, 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.
v
© ISO 2021 – Tous droits réservés

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NORME INTERNATIONALE ISO 6588-1:2021(F)
Papier, carton et pâtes — Détermination du pH des extraits
aqueux —
Partie 1:
Extraction à froid
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 froide.
Ce document est applicable à tous les types de papiers, de cartons et de pâtes.
Lorsque la quantité de substance ionique extractible est presque nulle, comme dans le cas des pâtes
hautement purifiées, la fidélité de la méthode devient mauvaise en raison des difficultés rencontrées
lors de la réalisation des mesurages de pH d’une eau contenant peu de substances électrolytiques.
Puisque, dans ce document, l’extraction est effectuée avec de l’eau distillée ou désionisée, le pH mesuré
peut parfois être 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 process
sont utilisés, comme 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 pâtes blanchies issues de
fibres vierg
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 6588-1
ISO/TC 6
Paper, board and pulps —
Secretariat: SCC
Determination of pH of aqueous
Voting begins on:
2021-08-13 extracts —
Voting terminates on:
Part 1:
2021-10-08
Cold extraction
Papier, carton et pâtes — Détermination du pH des extraits aqueux —
Partie 1: Extraction à froid
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 6588-1:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. ISO 2021

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ISO/FDIS 6588-1:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
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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Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

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ISO/FDIS 6588-1:2021(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus and equipment . 2
7 Sampling and preparation of sample . 2
7.1 Sampling . 2
7.2 Preparation of sample. 2
8 Procedure. 2
8.1 General . 2
8.2 Weighing . 3
8.3 Extraction . 3
8.4 Determination of pH . 3
9 Calculation . 3
10 Test report . 3
Annex A (informative) Preparation of some standard buffer solutions . 5
Annex B (informative) Precision . 6
Bibliography . 7
© ISO 2021 – All rights reserved iii

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ISO/FDIS 6588-1:2021(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
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 fourth edition cancels and replaces the third edition (ISO 6588-1:2020), of which it constitutes a
minor revision. The changes compared to the previous edition are as follows:
— clause references in 7.1, 8.1 and Clause 10 d) have been corrected.
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.
iv © ISO 2021 – All rights reserved

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ISO/FDIS 6588-1:2021(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-
[6][7]
exchange phenomena can be modelled very well with the Donnan theory .
If a relatively clean pulp fibre sample, 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 is measured in the bulk suspension liquor. By adding salt to this kind of system, the ion
exchange phenomena is 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 gives a more realistic environment when measuring the
pH of relatively clean pulp samples.
Based on the foregoing, two ISO Standards (ISO 6588-1 and ISO 29681) are available for determination
of the pH of cold aqueous extracts of paper, board, or pulps. In ISO 29681, a salt solution is added prior
to extraction; however, in ISO 6588-1, 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 gives more realistic results related to mill conditions than
those obtained with ISO 6588-1.
It is necessary to be aware that the results will not be the same when measuring pH according to
ISO 6588-1 and to ISO 29681. The difference can be significant especially when measuring pulps having
a low ionic strength.
ISO 6588-2 differs from this document only as regards 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 ISO 6588-1, addition of a salt solution is performed after extraction and
filtration only for the purpose of obtaining a more stable and accurate pH measurement.
© ISO 2021 – All rights reserved v

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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 6588-1:2021(E)
Paper, board and pulps — Determination of pH of aqueous
extracts —
Part 1:
Cold extraction
1 Scope
This document specifies a method for the determination of the pH-value defined by the electrolytes
extractable by cold water from a sample of paper, board or pulp.
This document is applicable to all types 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 lit
...