Overview
ISO 791:1973 establishes a gravimetric method using 8-hydroxyquinoline for the determination of aluminium content in magnesium alloys. This international standard applies specifically to magnesium alloys with aluminium content ranging from 1.5% to 12.0% by mass, excluding alloys that contain zirconium, thorium, or rare earth elements. The procedure outlined ensures precise and reliable quantification of aluminium, critical for quality control and verification in metallurgical and materials engineering contexts.
This standardized analytical technique was developed by the International Organization for Standardization (ISO) to promote consistency in chemical analysis of magnesium alloys across laboratories and industries worldwide.
Key Topics
- Scope: Applicable to magnesium alloys without zirconium, thorium, or rare earths, measuring aluminium within 1.5% to 12.0%.
- Analytical Principle:
- The sample is digested with hydrochloric acid to release aluminium ions.
- Aluminium is precipitated using ammonium benzoate in a reducing acetic medium.
- The aluminium precipitate is dissolved and re-precipitated as aluminium ortho-oxyquinolate by reaction with 8-hydroxyquinoline.
- The precipitated complex is filtered, washed, dried, and weighed to calculate aluminium content gravimetrically.
- Reagents: Includes sodium sulfite, hydrochloric acid, nitic acid, ammonium salts, cyanide potassium (for alternate precipitation), and 8-hydroxyquinoline, among others.
- Sample Preparation: Utilizes chip samples ≤1 mm thick, suitable for laboratory analysis.
- Calculation: Based on the mass of ortho-oxyquinolate precipitate and a conversion factor to derive aluminium percentage.
- Precision and Reporting: Detailed instructions on sample mass, precipitation conditions, filtration, washing, drying, and weighing ensure reproducible results. Test reports must include method reference, results, test conditions, and any deviations.
Applications
- Quality Control in Magnesium Alloy Production: Enables manufacturers and suppliers to verify aluminium concentrations, ensuring compliance with alloy specifications.
- Metallurgical Research: Supports research activities where precise aluminium quantification in magnesium-based materials is essential.
- Material Certification: Facilitates certification testing by providing a standardized method recognized globally.
- Failure Analysis and Regulatory Compliance: Used for investigating material performance issues related to aluminium content and meeting regulatory standards.
- Educational and Laboratory Training: Serves as a reference protocol in analytical chemistry and materials science education for gravimetric analysis techniques.
Related Standards
- ISO/R 791-1968: The predecessor recommendation replaced by ISO 791:1973, offering refined methodology for aluminium determination.
- Standards on Magnesium Alloy Sampling: Future ISO standards may provide complementary guidance on sample preparation and handling for magnesium alloys.
- ISO Standards on Chemical Analysis of Metals: Other ISO standards in the series cover analytical methods for different alloy systems, elements, and trace impurities.
- ASTM and JIS Methods: Alternative industry standards exist for aluminium analysis but may differ in technique or scope; ISO 791 is particularly noted for its gravimetric accuracy using 8-hydroxyquinoline.
Keywords: ISO 791, magnesium alloys, aluminium determination, gravimetric method, 8-hydroxyquinoline, aluminium analysis, metallurgical standards, magnesium alloy testing, chemical analysis, international standard, material quality control.