Overview
ISO 11441:1995 specifies a titrimetric analytical procedure for the determination of lead content in lead sulfide concentrates. The method is based on precipitation of lead as lead sulfate, dissolution of that precipitate in a known volume of EDTA (disodium ethylenediaminetetraacetic acid) and back‑titration of the excess EDTA with a standardized zinc solution. It applies to concentrates with lead contents from 10 % (m/m) to 80 % (m/m) and includes sample preparation, reagents, apparatus and calculation rules.
Key topics and requirements
- Analytical principle: Dissolution by fusion with sodium peroxide → double precipitation of lead as sulfate (with bismuth removal if needed) → dissolve lead sulfate in alkaline EDTA → back titration of excess EDTA with zinc.
- Applicable range: Lead content 10–80 % (m/m).
- Reagent and safety notes:
- Use analytical‑grade reagents and distilled water.
- Important reagents include sodium peroxide, sulfuric/perchloric/nitric/hydrofluoric acids, EDTA (0.1 mol·L‑1), and zinc standard solution.
- Safety warning for hydrofluoric acid handling (highly hazardous; use fume hood and PPE).
- Standardization and blanks:
- EDTA is standardized against zinc and lead metal; a blank titration is performed in parallel to check reagent quality.
- Calibration factors and repeatability checks are defined; standardization must be repeated if specified ranges are exceeded.
- Apparatus and sample handling:
- Class A volumetric glassware, nickel/zirconium crucibles for fusion, membrane filters and vacuum filtration apparatus.
- Procedure details:
- Tabled guidance on EDTA volume by lead content (e.g., ~50 mL EDTA for 10–60 % Pb, ~70 mL EDTA for 60–80 % Pb).
- Annexes A and B are integral (sample preparation and acceptance flow‑sheet); Annex C provides precision derivation (informative).
Applications and who uses it
- Quality control and assaying of lead sulfide concentrates at exploration, mining, concentrate preparation and smelting stages.
- Routine laboratory analysis for metallurgical laboratories, assay offices, smelter QC, and regulatory or certification bodies.
- Useful for analytical chemists, metallurgists, QA/QC managers, and providers of certified reference materials.
Related standards
- ISO 385‑1 (burettes), ISO 648 (pipettes), ISO 1042 (volumetric flasks), ISO 4787 (volumetric methods), ISO 9599 (hygroscopic moisture in concentrates), ISO Guide 35 (certification of reference materials).
Keywords: ISO 11441:1995, lead sulfide concentrates, lead determination, EDTA titration, back titration, lead sulfate precipitation, titrimetric method, assay, metallurgical laboratory.