ISO/DIS 787-9:2026(en)

ISO/TC 256

Secretariat: DIN

Date: 2026-01-27

General methods of test for pigments and extenders — Part 9: Determination of pH value of an aqueous suspension

© ISO 2026

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Contents

Foreword iv

1 Scope 1

2 Normative references 1

3 Terms and definitions 1

4 Reagents 1

5 Apparatus 1

6 Sampling 2

7 Procedure 2

8 Expression of results 2

9 Test report 2

Foreword

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This document was prepared by Technical Committee ISO/TC 256, Pigments, dyestuffs and extenders, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 298, Pigments and extenders, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This third edition cancels and replaces the second edition (ISO 787-9:2019), which has been technically revised.

The main changes are as follows:

— the normative references have been updated;

— in 4.1 the specification of distilled or demineralized water has been changed;

— in 4.2 “buffer solution” has been changed to “ion intensity regulating solution”;

— in Clause 7, quantity of added wetting agent has been changed;

— in Clause 9, the information contained in the test report has been updated.

A list of all parts in the ISO 787 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.

General methods of test for pigments and extenders — Part 9: Determination of pH value of an aqueous suspension

This document specifies a general method of test for determining the pH value of an aqueous suspension of a sample of pigment or extender.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling

ISO 18451‑1, Pigments, dyestuffs and extenders — Terminology — Part 1: General terms

For the purposes of this document, the terms and definitions given in ISO 18451‑1 apply.

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

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at https://www.electropedia.org/

4.1 Distilled or demineralized water, of at least grade 3 as specified in ISO 3696, having a pH between 5,0 and 7,5.

Because water rapidly absorbs carbon dioxide, the water shall be protected from access to the atmosphere.

4.2 Ion intensity regulating solution, 0,1 % KCl (p.a.), CAS Registry Number^®[1] 7447-40-7, prepared using water specified in 4.1.

The preparation of an ion intensity regulating solution is optional but recommended.

5.1 Glass container, made of chemically resistant glass, fitted with a ground glass or rubber stopper.

Glass container shall be cleaned before each use and to be rinsed with the corresponding water, see above. The rubber stopper shall not have been used for any other purpose.

5.2 pH measuring device, capable of measurement to 0,1 unit, calibrated against buffer solutions of known pH value at the temperature of the test.

5.3 Balance, with an appropriate limit of error.

Take a representative sample of the product to be tested, in accordance with ISO 15528.

Carry out the determination at room temperature.

Weigh a certain amount of the sample with a balance (5.3) and place it in the glass container (5.1). Prepare a 5 % to 10 % (mass fraction) suspension, using water (4.1) or the ion intensity regulating solution (4.2). Stopper the container and shake, roll or stir it vigorously for sufficient time. Allow it to stand for 5 min, and determine, to the nearest 0,1 unit, the pH value of the suspension with the pH measuring device (5.2). Alternatively, the suspension may be filtered beforehand.

If the product does not disperse easily in water, a wetting agent should be used. In this case, pure ethanol or methanol, up to 10 % (volume fraction) of the suspension, may be used, but care should be taken to ensure that the minimum quantity is used. The neutrality of the wetting agent should be checked once by making a blank determination. If a wetting agent is used, the volume of water shall be reduced so that the original concentration of the suspension is maintained.

The type and quantity of wetting agent used shall be stated in the test report.

Record the pH value to the nearest 0,1 unit and record the temperature of the suspension to the nearest 1 °C.

Report the result to the nearest 0,1 unit.

The test report shall contain at least the following information:

a) the identification of the product tested;

b) a reference to this document, i.e. ISO 787‑9:—;

c) the concentration of the suspension and the liquid used (water or the ion intensity regulating solution);

d) filtering method if the suspension is filtered;

e) if used, the type and quantity of wetting agent;

f) the result of the test as indicated in Clause 8, and the test temperature;

g) any deviation, by agreement or otherwise, from the procedure specified;

h) any unusual features (anomalies) observed during the test;

i) the date of the test.

1. Chemical Abstracts Service (CAS) Registry Number® is a trademark of the American Chemical Society (ACS). This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of the product named. Equivalent products may be used if they can be shown to lead to the same results. ↑