Overview - ISO 15661:2020 (total chlorine determination)
ISO 15661:2020 specifies an analytical method for determination of total chlorine content in copper and nickel sulfide ores and concentrates using alkaline fusion and potentiometric titration. The standard covers two validated methods with applicable chlorine ranges:
- Method 1: 80 µg/g to 4 300 µg/g
- Method 2: 70 µg/g to 4 300 µg/g
The procedure decomposes test portions by alkaline fusion, oxidizes sulfides, and determines chloride at acid pH by potentiometric titration with silver nitrate (AgNO3). The document also defines required reagents, apparatus, sample preparation, quality controls (blanks and duplicates), precision/accuracy reporting and test reporting.
Key technical topics and requirements
- Principle: Fusion of sample with either a carbonate flux (Na2CO3 + K2CO3) or a potassium-based flux (KNO3 + KOH), dissolution, oxidation of sulfide with H2O2, and potentiometric titration of chloride after acidification.
- Reagents and purity: Use analytical-grade reagents and high-purity water (ISO 3696 Grade 2). Key reagents include AgNO3 (titrant), NaCl and NaBr (standardization), HNO3 and H2O2.
- Standardization: Potentiometric standardization of AgNO3 using known NaBr/NaCl additions to establish titration factor (target factor ~0.99–1.01).
- Apparatus: Zirconium or nickel crucibles, muffle furnace, potentiometric titrator with silver electrode, volumetric glassware complying with ISO specifications.
- Quality control: Perform two blanks alongside analyses, at least duplicate determinations under repeatability conditions, and follow precision/accuracy clauses for reporting.
- Safety note: The method involves hazardous materials and high temperatures - users must implement appropriate laboratory safety and health practices.
Practical applications and intended users
This standard is intended for:
- Mineral assay and analytical laboratories testing copper and nickel sulfide ores and concentrates
- Smelting and metallurgical process control teams monitoring halogen content
- Quality assurance/quality control (QA/QC) in mining and concentrate production
- Regulatory or contractual testing where total chlorine content affects product handling, corrosion risk, or metallurgical behavior
Practical benefits:
- Provides a reproducible, validated method for reliable chlorine quantification
- Supports process optimization, material compatibility assessments and compliance reporting
- Enables consistent inter-laboratory results through specified reagents, apparatus and standardization procedures
Related standards
Keywords: ISO 15661:2020, chlorine determination, alkaline fusion, potentiometric titration, copper sulfide ores, nickel sulfide concentrates, total chlorine content, silver nitrate titration, analytical method.