Overview
ISO 11210:2023 - "Jewellery and precious metals - Determination of platinum - Gravimetry using ammonium chloride" specifies a gravimetric laboratory method for determining platinum content in homogeneous precious-metal materials. The procedure is optimized for platinum fineness between 50 ‰ and 999 ‰ by mass. For fineness above 999 ‰, a spectroscopy-by-difference approach (e.g., ISO 15093) is recommended. ISO 11210:2023 is also listed as a recommended method for fineness determination in jewellery alloys covered by ISO 9202.
Key topics and technical requirements
- Principle: Dissolve the sample in aqua regia, precipitate platinum as diammonium hexachloroplatinate using ammonium chloride, convert the precipitate to platinum sponge by ignition, and weigh the metallic platinum.
- Sample size & accuracy: Typical tests use samples containing ~250 mg to 1 g of platinum. Analytical balance reading accuracy specified at 0.01 mg.
- Reagents & conditions: Uses aqua regia, hydrochloric and nitric acids, saturated ammonium chloride solution, and, if needed, reducing/inert gases for ignition control.
- Apparatus: Standard lab glassware, porcelain crucibles (20–45 ml), muffle furnace (≥900 °C), ashless filter paper (retains >3 µm), and ICP‑OES for co‑precipitate analysis.
- Silver handling: Includes a dedicated preparation route to remove silver as AgCl before platinum precipitation.
- Co‑precipitation correction: Co‑precipitated alloying elements are quantified (e.g., by ICP‑OES) from the dissolved platinum sponge and used to correct the platinum mass.
- Quality limits: Residual platinum in filtrate must not exceed 0.5 % of the initial sample’s platinum; duplicate determinations must agree to better than 3 ‰.
- Reporting: Test reports must identify the sample, sampling procedure, reference to ISO 11210:2023, and platinum content in ‰ (single and mean values).
Applications and users
- Laboratories performing platinum determination, gravimetric assays, and fineness certification for jewellery and precious-metal products.
- Quality control in jewellery manufacturing, bullion assay, precious-metal recycling and refining where gravimetric accuracy and traceable methods are required.
- Regulatory bodies and conformity assessment organizations verifying declared fineness in precious-metal articles.
- Useful when spectroscopy is unsuitable or as a reference/confirmatory method for platinum content.
Related standards
- ISO 15093 - spectroscopy method by difference for very high fineness
- ISO 9202 - jewellery alloy fineness determination guidance
- ISO 11490 - harmonization referenced in the standard
- ISO 11596 - sampling procedures for precious metals
Keywords: ISO 11210, platinum determination, gravimetry, ammonium chloride, jewellery, precious metals, fineness, assay method, ICP‑OES.
