ISO 6588-2:2005

INTERNATIONAL ISO
STANDARD 6588-2
First edition
2005-05-15

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 6588-2:2005(E)
©
ISO 2005

---------------------- Page: 1 ----------------------
ISO 6588-2:2005(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
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Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.


©  ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland

ii © ISO 2005 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 6588-2:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references . 1
3 Principle . 1
4 Reagents . 2
5 Apparatus and equipment. 2
6 Sampling and preparation of sample. 2
7 Procedure. 2
8 Calculation. 3
9 Precision . 3
10 Test report. 4
Annex A (informative) Preparation of some standard buffer solutions. 5
Bibliography . 6

© ISO 2005 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO 6588-2:2005(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 6588-2 was prepared by Technical Committee ISO/TC 6, Paper, board and pulps.
This first edition of ISO 6588-2, together with ISO 6588-1, cancels and replaces ISO 6588:1981, which has
been technically revised. The work within ISO/TC 6 has shown that the results obtained with the two parts of
ISO 6588 are equivalent to those obtained in ISO 6588:1981. There are four major differences compared with
the previous edition of ISO 6588:1981:
a) ISO 6588 has been divided into two parts: one dealing with cold extraction and the other with hot
extraction;
b) the determination is now carried out on an air-dry sample without determination of dry matter content, as
the amount of sample is not critical;
c) the extract is filtered;
d) a salt solution is added to speed up the measurement.
ISO 6588 consists of the following parts, under the general title Paper, board and pulps — Determination of
pH of aqueous extracts:
 Part 1: Cold extraction
 Part 2: Hot extraction
iv © ISO 2005 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 6588-2:2005(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-exchange phenomena can
be modelled very well with the Donnan theory [2, 3].
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.
It is necessary to be aware of these effects when interpreting the measured pH-values of highly purified pulps.

© ISO 2005 – All rights reserved v

---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 6588-2:2005(E)

Paper, board and pulps — Determination of pH of aqueous
extracts —
Part 2:
Hot extraction
1 Scope
This part of ISO 6588 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 part of ISO 6588 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 part of ISO 6588 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.
ISO 6588-1 differs from this part of ISO 6588 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.
For cellulosic papers used for electrical purposes, the method used should be that given in IEC 60554-2
(see [4] in the Biblio
...

SLOVENSKI STANDARD
SIST ISO 6588-2:2011
01-maj-2011
3DSLUNDUWRQOHSHQNDLQYODNQLQH'RORþDQMHS+YUHGQRVWLYRGQLKHNVWUDNWRY
GHO(NVWUDNFLMDYYURþHP
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
Ta slovenski standard je istoveten z: ISO 6588-2:2005
ICS:
85.040 Vlaknine Pulps
85.060 Papir, karton in lepenka Paper and board
SIST ISO 6588-2:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST ISO 6588-2:2011

---------------------- Page: 2 ----------------------

SIST ISO 6588-2:2011


INTERNATIONAL ISO
STANDARD 6588-2
First edition
2005-05-15

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 6588-2:2005(E)
©
ISO 2005

---------------------- Page: 3 ----------------------

SIST ISO 6588-2:2011
ISO 6588-2:2005(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.


©  ISO 2005
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland

ii © ISO 2005 – All rights reserved

---------------------- Page: 4 ----------------------

SIST ISO 6588-2:2011
ISO 6588-2:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references . 1
3 Principle . 1
4 Reagents . 2
5 Apparatus and equipment. 2
6 Sampling and preparation of sample. 2
7 Procedure. 2
8 Calculation. 3
9 Precision . 3
10 Test report. 4
Annex A (informative) Preparation of some standard buffer solutions. 5
Bibliography . 6

© ISO 2005 – All rights reserved iii

---------------------- Page: 5 ----------------------

SIST ISO 6588-2:2011
ISO 6588-2:2005(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 6588-2 was prepared by Technical Committee ISO/TC 6, Paper, board and pulps.
This first edition of ISO 6588-2, together with ISO 6588-1, cancels and replaces ISO 6588:1981, which has
been technically revised. The work within ISO/TC 6 has shown that the results obtained with the two parts of
ISO 6588 are equivalent to those obtained in ISO 6588:1981. There are four major differences compared with
the previous edition of ISO 6588:1981:
a) ISO 6588 has been divided into two parts: one dealing with cold extraction and the other with hot
extraction;
b) the determination is now carried out on an air-dry sample without determination of dry matter content, as
the amount of sample is not critical;
c) the extract is filtered;
d) a salt solution is added to speed up the measurement.
ISO 6588 consists of the following parts, under the general title Paper, board and pulps — Determination of
pH of aqueous extracts:
 Part 1: Cold extraction
 Part 2: Hot extraction
iv © ISO 2005 – All rights reserved

---------------------- Page: 6 ----------------------

SIST ISO 6588-2:2011
ISO 6588-2:2005(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-exchange phenomena can
be modelled very well with the Donnan theory [2, 3].
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.
It is necessary to be aware of these effects when interpreting the measured pH-values of highly purified pulps.

© ISO 2005 – All rights reserved v

---------------------- Page: 7 ----------------------

SIST ISO 6588-2:2011

---------------------- Page: 8 ----------------------

SIST ISO 6588-2:2011
INTERNATIONAL STANDARD ISO 6588-2:2005(E)

Paper, board and pulps — Determination of pH of aqueous
extracts —
Part 2:
Hot extraction
1 Scope
This part of ISO 6588 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 part of ISO 6588 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 part of ISO 6588 is performed with distilled or deionised water, the pH-value
measured will sometimes be different (e.g. fully bleached pulp) from
...

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Papier, carton et pâtes -- Détermination du pH des extraits aqueux -- Partie 2: Extraction à chaudPaper, board and pulps -- Determination of pH of aqueous extracts -- Part 2: Hot extraction85.060Papir, karton in lepenkaPaper and board85.040VlakninePulpsICS:Ta slovenski standard je istoveten z:ISO 6588-2:2005oSIST ISO 6588-2:2011en01-marec-2011oSIST ISO 6588-2:2011SLOVENSKI
STANDARD



oSIST ISO 6588-2:2011



Reference numberISO 6588-2:2005(E)© ISO 2005
INTERNATIONAL STANDARD ISO6588-2First edition2005-05-15Paper, 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
oSIST ISO 6588-2:2011



ISO 6588-2:2005(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
©
ISO 2005 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel.
+ 41 22 749 01 11 Fax
+ 41 22 749 09 47 E-mail
copyright@iso.org Web
www.iso.org Published in Switzerland
ii © ISO 2005 – All rights reserved
oSIST ISO 6588-2:2011



ISO 6588-2:2005(E) © ISO 2005 – All rights reserved iii Contents Page Foreword.iv Introduction.v 1 Scope.1 2 Normative references.1 3 Principle.1 4 Reagents.2 5 Apparatus and equipment.2 6 Sampling and preparation of sample.2 7 Procedure.2 8 Calculation.3 9 Precision.3 10 Test report.4 Annex A (informative)
Preparation of some standard buffer solutions.5 Bibliography.6
oSIST ISO 6588-2:2011



ISO 6588-2:2005(E) iv © ISO 2005 – All rights reserved 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 6588-2 was prepared by Technical Committee ISO/TC 6, Paper, board and pulps. This first edition of ISO 6588-2, together with ISO 6588-1, cancels and replaces ISO 6588:1981, which has been technically revised. The work within ISO/TC 6 has shown that the results obtained with the two parts of ISO 6588 are equivalent to those obtained in ISO 6588:1981. There are four major differences compared with the previous edition of ISO 6588:1981: a) ISO 6588 has been divided into two parts: one dealing with cold extraction and the other with hot extraction; b) the determination is now carried out on an air-dry sample without determination of dry matter content, as the amount of sample is not critical; c)
the extract is filtered; d) a salt solution is added to speed up the measurement. ISO 6588 consists of the following parts, under the general title Paper, board and pulps — Determination of pH of aqueous extracts:  Part 1: Cold extraction  Part 2: Hot extraction oSIST ISO 6588-2:2011



ISO 6588-2:2005(E) © ISO 2005 – All rights reserved v 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-exchange phenomena can be modelled very well with the Donnan theory [2, 3].
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. It is necessary to be aware of these effects when interpreting the measured pH-values of highly purified pulps.
oSIST ISO 6588-2:2011



oSIST ISO 6588-2:2011



INTERNATIONAL STANDARD ISO 6588-2:2005(E) © ISO 2005 – All rights reserved 1 Paper, board and pulps — Determination of pH of aqueous extracts — Part 2: Hot extraction 1 Scope This part of ISO 6588 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 part of ISO 6588 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 part of ISO 6588 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 wat
...

NORME ISO
INTERNATIONALE 6588-2
Première édition
2005-05-15

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 6588-2:2005(F)
©
ISO 2005

---------------------- Page: 1 ----------------------
ISO 6588-2:2005(F)
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©  ISO 2005
Droits de reproduction réservés. Sauf prescription différente, 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 et les microfilms, sans l'accord écrit
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Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
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Web www.iso.org
Publié en Suisse

ii © ISO 2005 – Tous droits réservés

---------------------- Page: 2 ----------------------
ISO 6588-2:2005(F)
Sommaire Page
Avant-propos. iv
Introduction . v
1 Domaine d'application. 1
2 Références normatives. 1
3 Principe . 1
4 Réactifs . 2
5 Appareillage et équipement . 2
6 Échantillonnage et preparation de l'échantillon . 2
7 Mode opératoire . 2
8 Calculs. 3
9 Fidélité. 4
10 Rapport d'essai . 4
Annexe A (informative) Préparation des solutions tampons étalons . 5
Bibliographie . 6

© ISO 2005 – Tous droits réservés iii

---------------------- Page: 3 ----------------------
ISO 6588-2:2005(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 (CEI) en ce qui concerne la normalisation électrotechnique.
Les Normes internationales sont rédigées conformément aux règles données dans les Directives ISO/CEI,
Partie 2.
La tâche principale des comités techniques est d'élaborer les Normes internationales. Les projets de Normes
internationales adoptés par les comités techniques sont soumis aux comités membres pour vote. Leur
publication comme Normes internationales requiert l'approbation de 75 % au moins des comités membres
votants.
L'attention est appelée 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.
L'ISO 6588-2 a été élaborée par le comité technique ISO/TC 6, Papiers, cartons et pâtes.
Cette première édition de l'ISO 6588-2, ainsi que l’ISO 6588-1, annule et remplace l'ISO 6588:1981, qui a fait
l'objet d'une révision technique. Des travaux dans le cadre de l'ISO/TC 6 ont démontré que les résultats
obtenus avec les deux parties de l’ISO 6588 sont égaux à ceux obtenus avec l’ISO 6588:1981. Il y a quatre
différences majeures par rapport à l'édition précédente, l’ISO 6588:1981:
a) l’ISO 6588 a été séparée en deux parties, l’une pour l'extraction à froid et l'autre pour l'extraction à chaud;
b) la détermination est maintenant effectuée sur un échantillon séché à l'air, sans détermination de la teneur
en matière sèche, puisque la quantité de l'échantillon n'est pas critique;
c) l'extrait est filtré;
d) une solution saline est ajoutée pour rendre la détermination plus rapide.
L'ISO 6588 comprend les parties suivantes, présentées sous le titre général Papier, carton et pâtes —
Détermination du pH des extraits aqueux:
 Partie 1: Extraction à froid
 Partie 2: Extraction à chaud
iv © ISO 2005 – Tous droits réservés

---------------------- Page: 4 ----------------------
ISO 6588-2:2005(F)
Introduction
Il est bien connu que la fibre kraft contient des groupes ionisables qui sont fixés à ou se trouvent à l'intérieur
de 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 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 la fibre agit en tant
qu'échangeur d'ions. Ce phénomène d'échange d'ions peut être modélisé très bien en utilisant la théorie de
Donnan [2,3].
Si un échantillon de pâte de fibres relativement propre, par exemple une pâte blanchie et séchée, est dilué
dans de l'eau déionisée, le résultat sera une pâte en suspension de très faible concentration ionique. Dans un
tel système, la plupart des cations présents, incluant les protons, seront concentrés dans un volume d'eau
retenu par la paroi de la fibre. Si le pH est mesuré, il sera mesuré dans la pâte environnante. En ajoutant un
sel à ce type de système, le phénomène d'échange d'ions sera 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.
Il est nécessaire d'être conscient de ces effets lors de l'interprétation des valeurs de pH telles que mesurées
pour des pâtes hautement purifiées.
© ISO 2005 – Tous droits réservés v

---------------------- Page: 5 ----------------------
NORME INTERNATIONALE ISO 6588-2:2005(F)

Papier, carton et pâtes — Détermination du pH des extraits
aqueux —
Partie 2:
Extraction à chaud
1 Domaine d'application
La présente partie de l’ISO 6588 spécifie une méthode pour la détermination de la valeur de pH définie par les
électrolytes extractibles d'un échantillon de papier, de carton ou de pâte, par de l'eau chaude.
La présente partie de l’ISO 6588 est applicable à tous les types de papiers, de cartons ou de pâtes.
Lorsque la quantité de substance ionique extractible est presque nulle, comme dans le cas des pâtes
hautement purifiées, la précision de cette méthode devient mauvaise à cause des difficultés engendrées par
la mesure du pH d'une eau contenant peu de substances électrolytiques.
Puisque l'extraction dans la présente partie de l’ISO 6588 est effectuée avec de l'eau distillée ou de l'eau
déionisée, la valeur de pH mesurée sera parfois différente (par exemple pour une pâte hautement blanchie)
de la valeur de pH mesurée sous les conditions d'opération à l'usine, alors que différents types d'eaux de
procédé, par exemple de l'eau de rivière traitée chimiquement contenant des électrolytes, sont utilisées.
L’ISO 6588-1 diffère de la présente partie de l’ISO 6588 seulement en ce qui à trait aux conditions d'extraction.
Aucun conseil général ne peut être fourni quant à laquelle des deux méthodes (à froid ou à chaud) est
indiquée dans une situation particulière.
Pour les papiers cellulosiques à usages électriques, il est recommandé que la méthode utilisée soit celle de la
Norme Internationale CEI 60554-2 (voir [4] dans la Bibliog
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