Overview
ISO 5196-1:1980 - "Magnesium alloys - Determination of thorium - Part 1: Gravimetric method" specifies a gravimetric chemical-analysis procedure to quantify thorium in magnesium alloys. Published in 1980, the standard covers principle, reagents, apparatus, sampling guidance, the stepwise analytical procedure, expression of results and test-report requirements. The method is applicable to products with thorium contents between 0.2% and 5.0% (m/m).
Key topics and technical requirements
- Scope and applicability: Designed for magnesium alloys containing 0.2–5.0% thorium by mass.
- Principle: Dissolve the alloy in hydrochloric acid, separate thorium as a benzoate, convert to thorium oxalate and then to thorium oxide by calcination; weigh the oxide gravimetrically.
- Reagents (analytical grade): hydrochloric acid (concentrated and diluted strengths described), benzoic acid (20 g/L and 2.5 g/L solutions), oxalic acid (saturated solution and wash solution), ammonium chloride, hydroxylamine hydrochloride, ammonium hydroxide, bromophenol blue indicator, distilled water.
- Sampling: Laboratory test-piece preparation guidance given (chip thickness ≤ 1 mm). Specific sample masses: typically 5 g for 0.2–1.5% Th, 3 g for 1.5–3.0% Th, and 2 g for 3.0–5.0% Th.
- Procedure highlights:
- Dissolution in HCl, boiling and filtration if needed.
- Precipitation of thorium as benzoate, then conversion to oxalate.
- Filtration, washing with oxalic-acid wash solution, transfer to pre-calcined porcelain crucible.
- Incinerate the filter (~500 °C) and calcine at 950 °C to constant mass to obtain thorium oxide for weighing.
- Expression of results: Thorium content is calculated from the mass of thorium oxide using a conversion factor (0.8788) to report percentage by mass. Full test-report content required (method reference, results and format, details of deviations, etc.).
Applications and who uses it
- Metallurgical and quality-control laboratories performing chemical analysis of magnesium alloys.
- Alloy producers and suppliers requiring certification of alloy composition for product specification and traceability.
- Materials testing and inspection bodies that verify compliance with contract or regulatory requirements.
- Research and development teams characterizing alloy formulations where thorium is an additive.
Related standards
- Developed by ISO/TC 79 (Light metals and their alloys). The standard notes that specific international guidance on sampling of magnesium and its alloys will be provided in a subsequent ISO publication.
Keywords: ISO 5196-1:1980, magnesium alloys, thorium determination, gravimetric method, thorium analysis, chemical analysis, thorium oxide, calcination, laboratory procedure.