ISO 4323:2025

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.