ISO 4323:2025
(Main)Surface active agents — Soaps — Determination of chloride content by potentiometric method
Surface active agents — Soaps — Determination of chloride content by potentiometric method
This document specifies a potentiometric method for the determination of the chloride content in soaps, with or without other surface-active agents, and also in compounded products. The method is applicable for chloride mass fractions between 0,01 % to 1,0 %.
Titre manque
General Information
Standards Content (Sample)
International
Standard
ISO 4323
Third edition
Surface active agents — Soaps —
2025-10
Determination of chloride content
by potentiometric method
Reference number
© ISO 2025
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Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 1
6 Apparatus . 2
7 Sampling . 3
8 Procedure . 3
8.1 Measurement temperature .3
8.2 Standardization of the silver nitrate solution.3
8.2.1 Titration .3
8.2.2 Calculation of solution .4
8.3 Determination .4
8.3.1 Test portion .4
8.3.2 Titration .5
8.3.3 Blank test .5
9 Expression of results . 5
10 Precision . 5
10.1 General .5
10.2 Repeatability .5
10.3 Reproducibility . .5
11 Test report . 5
Annex A (informative) Example V calculation . 7
EQ
Bibliography . 8
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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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
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This document was prepared by Technical Committee ISO/TC 91, Surface active agents.
This third edition cancels and replaces the second edition (ISO 4323:2018), which has been technically
revised.
The main changes are as follows:
— Normative references have been revised;
— text revised;
— precision clause added.
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
International Standard ISO 4323:2025(en)
Surface active agents — Soaps — Determination of chloride
content by potentiometric method
1 Scope
This document specifies a potentiometric method for the determination of the chloride content in soaps,
with or without other surface-active agents, and also in compounded products.
The method is applicable for chloride mass fractions between 0,01 % to 1,0 %.
2 Normative references
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 385, Laboratory glassware — Burettes
ISO 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 8212, Soaps and detergents — Techniques of sampling during manufacture
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1
chloride content
mass fraction of chloride, expressed as sodium chloride and in percent, determined in accordance with the
procedure described in this document
4 Principle
A test portion is dissolved in water and isopropanol. The suspension is acidified with nitric acid then the
chloride ions are titrated potentiometrically with a silver nitrate standard solution by using either a silver
ion selective electrode plus a reference electrode or a combined electrode.
5 Reagents
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only
distilled water or water of equivalent purity in accordance with ISO 3696.
5.1 Nitric acid, approximately 6 mol/l solution.
5.2 Silver nitrate, approximately 0,1 mol/l solution.
Dissolve 8,5 g of silver nitrate in water in a 500 ml one-mark volumetric flask, dilute to the mark and mix.
Store this solution capped in a dark amber-coloured flask. Standardize the solution according to (8.2) before
use against sodium chloride standard solution (5.4 or 5.5).
Store the solution away from direct light.
5.3 Silver nitrate, approximately 0,01 mol/l solution.
Transfer 10,0 ml of the solution (5.2) into a 100 ml one-mark volumetric flask. Dilute to the mark with water
and mix.
Prepare this standard solution immediately prior to use.
5.4 Sodium chloride, standard solution, 0,1 mol/l.
Weigh, to the nearest 0,001 g, 2,922 g of primary standard sodium chloride, previously dried for 2 h at 105 °C
and cooled in a desiccator. Dissolve in a small quantity of water and transfer quantitatively to a 500 ml one-
mark volumetric flask. Dilute to the mark and mix.
Potassium chloride can be used instead of sodium chloride but the weight of the chemical is to be adjusted
accordingly.
5.5 Sodium chloride, standard solution, 0,01 mol/l.
Transfer 10,0 ml of the standard solution (5.4) into a 100 ml one-mark volumetric flask. Dilute to the mark
with water and mix.
Prepare this standard solution immediately prior to use.
5.6 Isopropanol.
6 Apparatus
All laboratory glassware shall be class A, in accordance with ISO 385, ISO 648 or ISO 1042 as appropriate.
During the analysis, unless otherwise stated, ordinary laboratory apparatus and the following shall be used.
6.1 Potentiometer, provided with a measuring electrode suitable for the determination of chloride and
sensitivity 2 mV, covering the range −500 mV to +500 mV, or an auto-titrator
6.2 Electrode, silver ion selective electrode (ISE) with double junction reference electrode (10 % KNO in
outer junction and saturated AgCl in inner junction) or a combined electrode.
6.3 Electromagnetic stirrer
6.4 Burette, graduated in divisions of 0,1 ml, of capacity 50 ml, or an automatic plunger burette, readable
to the nearest 0,01 ml. The burette, or automatic plunger burette, should preferably be made of brown glass.
6.5 Device for grinding or grating cheese, capable of being cleaned easily.
6.6 Analytical balance, capable of weighing to the nearest 1 mg.
6.7 Vessel, suitable for blending and titrating.
7 Sampling
The sampling shall be done in accordance with ISO 8212. The soap bar should be grated with a cheese grater
(6.5). At least half of the bar should be grated to ensure a complete representation of the bar. The grated
soap sample should be kept in an air-tight container to avoid moisture loss. Soap bar/sample should not have
been damaged or changed during transport or storage.
8 Procedure
8.1 Measurement temperature
In order to reduce the effects of thermal and electric hysteresis, take care that the temperatures of
electrodes, the water used for washings, the standard solutions and the test solution are as close to each
other as possible. The temperatures of the standard solutions and the test solution should not differ by more
than 1 °C. The measurement temperature should be 25 °C ± 5 °C.
8.2 Standardization of the silver nitrate solution
8.2.1 Titr
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