ISO 11426-2021 PDF

Full title and description

St ISO 11426-2021 — Jewellery and precious metals — Determination of gold — Cupellation method (fire assay). This international standard specifies the classical cupellation (fire assay) procedure for accurately determining the gold content (fineness) of homogeneous materials used in jewellery and related precious‑metal products.

Abstract

The standard defines a stepwise cupellation (fire assay) method for the quantitative determination of gold in homogeneous samples, preferably for fineness in the range 100–999.5 parts per thousand (‰). It covers sample preparation (inquartation when required), addition of lead, cupellation to obtain a precious‑metal button, parting of silver, and final weighing of gold. It includes provisions for samples with high base‑metal content, platinum/palladium presence or high silver ratios, and gives limits for elements (not compatible with significant iridium, rhodium or ruthenium: sum > 0.25 ‰). The method is recommended for use with jewellery alloy fineness determination referenced in ISO 9202.

General information

• Status: Published (active)
• Publication date: 11 March 2021
• Publisher: International Organization for Standardization (ISO)
• ICS / categories: 39.060 — Jewellery
• Edition / version: Edition 4 (2021)
• Number of pages: 8 (ISO published text)

Scope

ISO 11426:2021 applies to the determination of the gold content of materials considered homogeneous by the cupellation (fire assay) technique. It is intended primarily for samples with gold fineness from approximately 100 ‰ up to 999.5 ‰; for gold fineness above 999.5 ‰, spectroscopy‑by‑difference methods (for example ISO 15093) are recommended. The standard provides adaptations for samples containing substantial base metals, platinum/palladium or high silver content, and states incompatibilities with significant amounts of iridium, rhodium or ruthenium.

Key topics and requirements

• Principle and stepwise procedure: inquartation (if required), addition of assay lead, cupellation in an oxidizing furnace, recovery of a precious‑metal button, parting of silver with nitric acid and weighing of gold.
• Preferred measurement range: nominal fineness 100–999.5 ‰; notes on handling extremely high‑fineness samples.
• Elemental interferences and limits: not compatible with combined Ir/Rh/Ru above ~0.25 ‰; special precautions for Pt and Pd.
• Reagents and materials: assay‑grade lead, high‑purity silver for inquartation and proof samples, analytical‑grade acids and reagents.
• Apparatus and conditions: cupellation furnace (high‑temperature, oxidizing), magnesia cupels, balances with appropriate resolution for required accuracy.
• Quality control: use of proof samples, correction for systematic errors, repeatability criteria and required items for test reports.

Typical use and users

Laboratories performing fire‑assay analyses, assayers in refineries and jewellery manufacturing quality‑control teams, hallmarking and regulatory bodies checking alloy fineness, and forensic or trade laboratories requiring a reference wet‑chemistry method for gold determination. Users rely on this standard where high accuracy and traceable assay results are required.

Related standards

Standards commonly referenced alongside ISO 11426 include ISO 9202 (fineness ranges and designation for precious metal alloys), ISO 15093 (spectroscopic methods for very high‑fineness gold by difference), and other ISO methods for precious metals such as ISO 11210 (platinum determination), ISO 11427 (silver determination) and various ISO/TC 174 publications on sampling and testing of precious‑metal alloys. National adoptions (EN ISO / BS EN / DIN EN ISO) are often published with additional national forewords.

Keywords

cupellation, fire assay, gold determination, fineness, jewellery, precious metals, inquartation, assay, proof sample, parting, cupellation furnace

FAQ

Q: What is this standard?

A: ISO 11426:2021 is an international standard that specifies the cupellation (fire assay) method for determining gold content in homogeneous precious‑metal samples used in jewellery and related products.

Q: What does it cover?

A: It covers the complete fire‑assay procedure (sample preparation, inquartation if needed, addition of lead, cupellation, parting and weighing), applicable measurement ranges, adjustments for special sample types, and quality‑control and reporting requirements.

Q: Who typically uses it?

A: Assay laboratories, jewellers and manufacturers, precious‑metal refineries, hallmarking and regulatory authorities, and trade/forensic laboratories that require a reference wet‑chemistry method for gold analysis.

Q: Is it current or superseded?

A: This document is the current edition published in 2021 (Edition 4). It supersedes earlier editions (for example the 2014 edition) and is subject to ISO's periodic systematic review process.

Q: Is it part of a series?

A: Yes. ISO 11426 belongs to a set of ISO/TC 174 standards for jewellery and precious metals; related methods for silver, platinum and palladium determination and standards addressing sampling and fineness (e.g., ISO 9202, ISO 11427, ISO 11210) form a complementary series.

Q: What are the key keywords?

A: Cupellation, fire assay, gold, fineness, jewellery, precious metals, assay, inquartation, parting.