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THE NATIONAL STANDARD OF AMOUNT OF SUBSTANCE

Field consumer protection, type sample precious metal alloys

 

Holder of the national standard in the scope of the SI unit mol

The activities of the Department for precious metals, as the holder of the national standard in the scope of the SI unit mol, are focused mainly:

- in the assurance of the traceability of the measurements of the mass fraction of precious metals to the international level.

- to the establishment of reference values for selected measurements and their dissemination to lover levels of measurements of mass fraction of precious metals in field laboratories.

International recognition of Department for precious metals is obtained via the collaboration of MIRS chemical laboratory in international interlaboratory comparisons organized by AEAO (Association of European Assay Offices) as well as via the collaboration with other national institutions responsible for testing and conformity assessment of precious metal articles. Via a continuous research and development work preformed in the field of chemical measurements an appropriate expertise is obtained and the fulfillment of national needs is reached. 

Department for precious metals is responsible also for the most the most  difficult tasks in the filed of legal metrology connected to the testing and conformity assessment of precious metal articles as well as for the inspection of the quality of work of the suppliers, which independently assure the conformity of the articles by their own quality system.

 

Traceability of the measurements of the mass fraction of precious metals to international level

The traceability of the measurements of the mass fraction of precious metals to international level is obtained via the application of pure precious metals, with a proven traceability to primary standards, as reference materials in the measurement process.

Dissemination of the value of the national standard to field laboratories in Slovenia

Dissemination of the value of the national standard is obtained via the interlaboratory comparisons which are organized by MIRS for the field laboratories, which are performing the analysis of precious metal articles. The reference value for the mass fraction of particular precious metal in the alloy is determined prior to the comparison by MIRS chemical laboratory with accredited measurement methods with proven traceability and evaluated measurement uncertainty.

 

Research and development work

Research and development work of the Department for precious metals is mainly focused in a dissemination of measurement value for the measurements of the mass fraction of precious metals in different alloys. For these purposes the optimization and development of different chemical methods are investigated in order to minimize the measurement uncertainty of the chemical analysis of precious metal alloys. The studies of the traceability of chemical measurements as well as the study of different approaches to the evaluation of measurement uncertainty are also executed. Additionally the research work is focused in the improvement of the quality of measurements, homogeneity studies of the precious metal alloys used as samples in the proficiency testing schemes for Slovenian laboratories as well as to the automation of the measurement processes. The quality of measurements, performed at the Department for precious metals, and their metrological characteristics are examined and proven via the collaboration of MIRS chemical laboratory in different international interlaboratory comparisons. Novel measurement approaches as well as modified standardized procedures of chemical analysis of precious metal alloys are also examined and developed via such activities.

 

Best measurement capabilities

Department for precious metals performs the measurement of the mass fraction of precious metals in alloys by different methods, with the characteristics as listed below:

 

Method Standard Material Measurement intervalExpanded measurement uncertainty
Determination of gold in gold jewellery alloys – Cupellation method (fire assay)ISO 11426:1999 (except 7.3 and 7.5)Gold alloysMass fraction of Au from 333 ‰ to 990 ‰  ± 0,5 ‰
Determination of silver in silver jewellery alloys – Volumetric (potentiometric) method using sodium chloride or potassium chlorideISO 13756:1997Silver alloysMass fraction of Ag from 800 ‰ to 999 ‰ ± 3,2 ‰

 

Departmant for precious metals