British Standards Institution

Source:: ISO
Committee:: STI/53 - Specifications and test methods for jewellery and horology
Categories:: Information management | Standardization. General rules
Comment period start date:: 06/12/2024
Comment period end date:: 28/01/2025

Comment by:

28th Jan

Scope

This document specifies a cupellation method (fire assay) for the determination of silver on a material considered homogeneous. The silver content of the sample lies preferably between 400 parts per thousand (‰) to 999 parts per thousand (‰) by mass.

Fineness above 999 ‰ can be determined using a spectroscopy method by difference (e.g. ISO 15096 or ISO 18214).

The procedure is applicable to most types of silver samples. Some modifications are indicated for specific cases (presence of a large amount of base metals, see Annex A). It is compatible with the presence above trace levels of Platinum Group Metals, see Annex B.

This method is also intended to be used as the recommended method for the determination of fineness in jewellery alloys covered by ISO 9202.

Purpose

The determination of Ag content via fire assay is a technique widely used in laboratories in the precious metals industries and mines around the world. Although, there is no reference standard for this method.

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Please email further comments to: debbie.stead@bsigroup.com

Standard timeline

1. Proposal

Proposal start date:

06/12/2024

Proposal end date:

28/01/2025

2. Draft

3. Public Comments

4. Comment Resolution

5. Approval

6. Publication

Learn more about the standards development process

Standards Development

ISO/NP 25643 Jewellery and precious metals — Determination of silver — Cupellation method (fire assay)

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