ISO/FDIS 6588-1

Paper, board and pulps -- Determination of pH of aqueous extracts

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 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 process sont utilisés, par exemple de l'eau de rivière traitée chimiquement contenant des électrolytes. Dans de tels cas, il convient d'appliquer l'ISO 29681 qui est spécifiquement élaborée pour les pâtes blanchies à partir de fibres vierges et aux échantillons de pâtes de faible concentration ionique pour lesquels les valeurs de pH seront plus réalistes du procédé industriel que celles obtenues avec le présent document. Pour les papiers cellulosiques à usages électriques, il est recommandé d'utiliser la méthode indiquée dans la norme IEC 60554-2[4].

Papier, carton et pâtes -- Détermination du pH des extraits aqueux

General Information

• Status: Published
• ICS: 85.040 - Pulps
• ICS: 85.060 - Paper and board
• Technical Committee: ISO/TC 6 - Paper, board and pulps
• Drafting Committee: ISO/TC 6/WG 4 - Chemical analysis
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 13-Aug-2021
• Completion Date: 13-Aug-2021

RELATIONS

• Revised: ISO 6588-1:2020 - Paper, board and pulps -- Determination of pH of aqueous extracts
• Effective Date: 07-Aug-2021

Standards Content (sample)

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)
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© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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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
...