Overview
ISO 11490:2023 - Jewellery and precious metals - Determination of palladium - Gravimetry using dimethylglyoxime specifies a gravimetric analytical method for measuring palladium content in homogeneous precious‑metal materials. The method is optimized for samples with palladium content preferably between 50 and 999 ‰ (parts per thousand) by mass. Palladium above 999 ‰ is determined by spectroscopy by difference (e.g. ISO 15093). ISO 11490:2023 is also recommended for fineness determination in jewellery alloys covered by ISO 9202.
Key topics and technical requirements
- Principle: dissolve the sample in aqua regia, precipitate palladium as a dimethylglyoxime complex, calcine to metallic palladium (“palladium foam”) and weigh gravimetrically.
- Sample scope: homogeneous alloys and precious‑metal materials; preliminary composition check (e.g., XRF) recommended when composition is unknown.
- Treatment for silver-bearing samples: separate Ag as silver chloride (AgCl) prior to palladium precipitation.
- Reagents and equipment (examples specified):
- Concentrated HCl (≈30–37 %) and HNO3 (≈65–70 %), diluted solutions, aqua regia
- Dimethylglyoxime (aqueous and ethanolic saturated solutions)
- Muffle furnace (≈800 °C ± 50 °C), reducing and inert gases for calcination, porcelain crucibles, ash‑free filter paper, analytical balance (0.01 mg)
- ICP‑OES for trace‑element analysis of coprecipitated alloying elements
- Calcination and reduction: control oxidation during calcination (use of reducing gas or post‑reduction may be required) and determine coprecipitated elements in the dissolved palladium residue to apply corrections.
- Performance: duplicate determinations should agree within ±3 ‰ (repeatability criterion).
Practical applications and users
- Primary users:
- Jewellery and precious‑metals testing laboratories
- Assayers and quality control teams in jewellery manufacturing
- Precious‑metal refiners and analytical services verifying fineness and alloy composition
- Typical applications:
- Determination of palladium content in white gold and palladium alloys
- Routine fineness certification and compliance testing for hallmarks
- Reference/verification method where gravimetric accuracy is required or to validate spectroscopic methods
Related standards
- ISO 9202 - jewellery alloy fineness (related application)
- ISO 15093 - spectroscopy by difference for high palladium fineness
- ISO 11210 - harmonization of related gravimetric methods
- ISO 11596 - sampling procedures for precious metals
Note: Follow laboratory safety procedures when handling aqua regia and strong acids. For full procedural detail, acceptance criteria and reporting requirements consult the full ISO 11490:2023 document.
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