Overview
ISO 4323:2025 - Surface active agents - Soaps - Determination of chloride content by potentiometric method - specifies a potentiometric titration procedure to determine chloride content in soaps, compounded products and formulations containing surface‑active agents. The method is applicable to chloride mass fractions from 0.01 % to 1.0 % and uses silver nitrate titration monitored with a silver ion selective electrode (or combined electrode) connected to a potentiometer or autotitrator.
Keywords: ISO 4323:2025, chloride determination, potentiometric titration, soaps, silver nitrate, ion selective electrode, soap quality control.
Key topics and technical requirements
- Scope and applicability
- Intended for soaps with or without other surface‑active agents and for compounded products.
- Measurement range: 0.01 % to 1.0 % chloride (mass fraction).
- Principle
- Dissolve a test portion in water and isopropanol, acidify with nitric acid, then titrate chloride ions with standardized silver nitrate potentiometrically.
- Reagents and solutions
- Nitric acid ~6 mol/L; silver nitrate standard solutions (~0.1 mol/L and diluted 0.01 mol/L); sodium chloride primary standard solutions (0.1 and 0.01 mol/L); isopropanol; use water complying with ISO 3696.
- Store concentrated AgNO3 in amber flasks and prepare working dilutions immediately prior to use.
- Apparatus and glassware
- Potentiometer (sensitivity 2 mV, range −500 mV to +500 mV) or autotitrator.
- Silver ion selective electrode with double‑junction reference (or combined electrode).
- Class A glassware per ISO 385/648/1042; burettes or automatic plunger burettes; analytical balance (1 mg).
- Procedure and calculations
- Sampling per ISO 8212 (grating soap bars, avoid moisture loss).
- Maintain measurement temperature ~25 °C ± 5 °C and minimize temperature differences between solutions.
- Endpoint detection uses successive potential increments (ΔE); formulae provided to calculate exact titrant volume (V) and molarity (T).
- Blank test mandatory; precision and repeatability/reproducibility clauses included.
Applications and who uses this standard
- Quality control (QC) laboratories in soap and detergent manufacturing for routine chloride content testing.
- Product development and formulation teams validating raw material purity and finished product composition.
- Regulatory and compliance testing where chloride levels affect product specifications or stability.
- Independent testing laboratories performing standardized, traceable potentiometric chloride determinations.
Practical benefits include reliable, reproducible chloride quantification across a defined range and clear sampling/validation steps tailored to solid soap bars and compounded products.
Related standards
- ISO 8212 - Soaps and detergents - Techniques of sampling during manufacture
- ISO 3696 - Water for analytical laboratory use - Specification and test methods
- ISO 385, ISO 648, ISO 1042 - Laboratory glassware (burettes, pipettes, volumetric flasks)
- Prepared by ISO/TC 91 (Surface active agents)
Use ISO 4323:2025 to implement a validated potentiometric chloride test method for soap manufacturing, laboratory accreditation, and product specification control.
Open preview (PDF)Surface active agents — Soaps — Determination of chloride content by potentiometric method
