Overview
ISO 13291:2006 - "Zinc sulfide concentrates - Determination of zinc - Solvent extraction and EDTA titrimetric method" specifies a laboratory analytical procedure for measuring the mass fraction of zinc in zinc sulfide (ZnS) concentrates. The method applies to concentrates with zinc content in the range 11% to 62% and combines acid dissolution, selective solvent extraction (MIBK), and EDTA titrimetry at pH 5.5.
Key topics and requirements
- Scope and applicability: Valid for zinc sulfide concentrates having 11–62 % zinc; intended for routine assay and quality control.
- Analytical principle: Dissolve the test portion (bromine + nitric acid; HF/sulfuric for residue), form a zinc–thiocyanate complex, extract selectively into methyl isobutyl ketone (MIBK), chemically mask interferents (thiourea, citrate, iodide), then titrate the organic phase with standardized EDTA using xylenol orange indicator.
- Sample handling: Air-equilibrated test sample per ISO 9599; typical test portion ~2.5 g with duplicate determinations and reagent blank runs.
- Reagents & standards: Uses analytical-grade reagents (bromine, nitric, hydrofluoric acids, MIBK, thiourea, di-ammonium citrate, ammonium thiocyanate, buffer, potassium iodide). EDTA 0.05 mol/L is standardized against high‑purity zinc metal under the same conditions as sample analyses.
- Apparatus & conditions: Class A volumetric glassware, platinum crucibles for insoluble residues, muffle furnace for ashing, controlled oven balance precision to 0.1 mg.
- Quality and precision: Requires at least duplicate determinations, blank corrections, and EDTA standardization; the standard includes precision, trueness checks and procedures for accepting analytical values.
- Safety note: Method uses hazardous chemicals (bromine, HF, strong acids) - follow appropriate health, safety and regulatory controls.
Practical applications
- Routine zinc assay and grade verification in mining and concentrator laboratories.
- Quality control of zinc sulfide concentrates prior to smelting or sale.
- Verification and certification of concentrate composition for metallurgical accounting, contract settlement and regulatory reporting.
- Use by analytical chemists, assay labs, metallurgists, mining quality assurance teams and standards/inspection bodies.
Related standards
- ISO 9599 - hygroscopic moisture in sulfide concentrates (sample prep)
- ISO 3696 - water for analytical laboratory use
- ISO 385, ISO 648, ISO 1042, ISO 4787 - volumetric glassware specifications and use
- ISO Guide 35 - reference material principles
Keywords: ISO 13291:2006, zinc sulfide concentrates, solvent extraction, EDTA titrimetric method, zinc determination, MIBK extraction, analytical method, concentrate assay.
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