ISO 4323:2018

Soaps - Determination of chloride content - Potentiometric method

This document specifies a potentiometric method for the determination of the chloride content of soaps, containing or not containing other surface active agents, and also of compounded products.

Savons — Dosage des chlorures — Méthode potentiométrique

General Information

• Status: Published
• Publication Date: 06-Dec-2018
• ICS: 71.100.40 - Surface active agents
• Technical Committee: ISO/TC 91 - Surface active agents
• Drafting Committee: ISO/TC 91/WG 1 - Analytical methods
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 01-Oct-2025
• Completion Date: 13-Dec-2025

Relations

• Revised: ISO 4323:2025 - Surface active agents - Soaps - Determination of chloride content by potentiometric method
• Effective Date: 25-May-2024
• Revises: ISO 4323:1977 - Soaps - Determination of chlorides content - Potentiometric method
• Effective Date: 04-Nov-2015

Overview

ISO 4323:2018 specifies a potentiometric titration method for determining the chloride content of soaps (including compounded products and soaps that contain other surface‑active agents). The standard describes sample preparation, reagents, apparatus, calibration and titration procedures using silver nitrate (AgNO3) and a silver ion selective electrode (or combined electrode), and how to report results as mass percentage expressed as sodium chloride (NaCl).

Key topics and requirements

• Scope: Applicable to soaps and compounded products; chloride reported as % NaCl.
• Principle: Potentiometric titration of chloride ions with standard AgNO3 in an acidic medium using a silver ion selective electrode plus a reference electrode (or combined electrode).
• Reagents: Analytical grade reagents; nitric acid (6 mol/L); AgNO3 solutions (0.1 mol/L and ~0.01 mol/L); standard NaCl reference solutions (0.1 and 0.01 mol/L); isopropanol. Potassium chloride may be used as an alternative primary standard (adjust weight accordingly).
• Apparatus: Potentiometer (or autotitrator), silver ISE with double junction reference (recommended), electromagnetic stirrer, Class A burette (ISO 385), and basic glassware.
• Sampling & sample prep: Follow ISO 8212 for sampling during manufacture; solid soap bars should be grated (cheese grater) and stored airtight to avoid moisture loss.
• Calibration: Standardize AgNO3 by titrating known volumes of NaCl standard solutions; determine end‑point potentiometrically by the maximum incremental change in potential; calculate AgNO3 normality.
• Determination: Dissolve test portion in a 1:1 mixture of water and isopropanol, acidify with nitric acid, titrate with the appropriate AgNO3 solution (choice based on expected chloride content), and run a blank. Control temperatures (ideally 25 °C) to ±1 °C between solutions and electrodes.
• Results & reporting: Clause 9 gives the calculation to convert titration volumes and AgNO3 normality into chloride content (expressed as % NaCl). Test report must include sample ID, method reference, conditions, results and any deviations.

Applications and users

• Quality control laboratories in soap and detergent manufacturing
• R&D teams developing soap formulations
• Incoming raw‑material inspection and supplier quality assurance
• Regulatory testing and conformity assessment for product specifications
• Contract testing laboratories offering analytical services for personal care products

Related standards

• ISO 385 - Laboratory glassware - Burettes (used for titration apparatus requirements)
• ISO 8212 - Soaps and detergents - Sampling techniques during manufacture (sampling procedure referenced)
• Prepared by ISO/TC 91 (Surface active agents)

Keywords: ISO 4323:2018, chloride content, soaps, potentiometric method, silver nitrate titration, silver ion selective electrode, soap testing, quality control.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 4323
Second edition
2018-12
Soaps — Determination of chloride
content — Potentiometric method
Savons — Dosage des chlorures — Méthode potentiométrique
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

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 . 2
8 Procedure. 2
8.1 Measurement temperature . 2
8.2 Calibration of the silver nitrate solution . 3
8.2.1 Titration. 3
8.2.2 Calculation of normality of solution . 4
8.3 Determination . 4
8.3.1 Test portion . 4
8.3.2 Titration. 4
8.3.3 Blank test . 4
9 Expression of results . 5
10 Test report . 5
Annex A (informative) Example of how to calculate V . 6
EQ
Foreword
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This document was prepared by Technical Committee ISO/TC 91, Surface active agents.
This second edition cancels and replaces the first edition (ISO 4323:1977), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Replaced water with water + isopropanol (1 + 1) as solvent in determination.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 4323:2018(E)
Soaps — Determination of chloride content —
Potentiometric method
1 Scope
This document specifies a potentiometric method for the determination of the chloride content of soaps,
containing or not containing other surface active agents, and also of compounded products.
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 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 terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
chloride content of soap products
mass fraction of chloride, expressed as sodium chloride and in percent, determined in accordance with
the procedure described in this document
4 Principle
−
Potentiometric titration of the chloride (Cl ) ions with standard silver nitrate solution in an acidic
medium, by using either a silver ion selective electrode plus a reference electrode or a combi
...