ISO 11210 is the international standard, published by the International Organization for Standardization, that prescribes the method for the determination of platinum content in platinum jewellery alloys. The standard sets out the gravimetric procedure by which a sample of platinum alloy is dissolved, the platinum is precipitated and isolated, and its mass is determined to a level of precision sufficient to verify hallmarking compliance. ISO 11210 is the reference method for platinum assaying in laboratories accredited under hallmarking regimes worldwide and is the technical basis for compliance with the related fineness standards in ISO 9202 and the various national platinum hallmarking regulations.

Method

The standard prescribes that a known mass of platinum alloy sample be dissolved in aqua regia, a mixture of hydrochloric and nitric acids, with optional supplementary digestion to ensure complete dissolution of any insoluble residues. The platinum in solution is then selectively precipitated using a reducing agent that converts platinum salts to elemental metal while leaving other accompanying metals in solution. The precipitate is filtered, washed, ignited, and weighed; the platinum content is calculated from the recovered mass relative to the original sample mass.

The standard provides detailed protocols for sample preparation, reagent purity, the digestion sequence, the precipitation conditions, the ignition temperature and atmosphere, and the calculation of results, including correction factors for any retained accompanying metals. The reproducibility of the method, when performed under accredited laboratory conditions, is sufficient to verify platinum content to within parts per thousand of the declared fineness, which meets the requirements of all major hallmarking schemes.

Use in hallmarking

National hallmarking offices including the British Assay Offices, the Bureau de Garantie in France, the Italian and Spanish hallmarking authorities, and ISO 17025-accredited assay laboratories worldwide use ISO 11210 (or national methods harmonised with it) as the technical basis for platinum content verification. A piece of platinum jewellery presented for hallmarking is assayed against the declared fineness, typically 850, 900, 950, or 999 parts per thousand, and the hallmark is applied only if the assay confirms compliance. ISO 11210 ensures that this verification is reproducible across laboratories and consistent across markets.

Related standards

The ISO 11210 standard is part of the wider ISO standards suite on precious metal assaying, which includes ISO 11427 on silver assaying, ISO 11426 on gold assaying, and ISO 9202 on fineness designations for precious metal alloys. The full set of standards governs the determination and labelling of precious metal content for consumer protection in international trade. ISO/TC 174, the Technical Committee on jewellery, maintains the standards and updates them at intervals to reflect advances in analytical methodology.