GB/T 15072.2-2025 Method for chemical analysis of precious metal alloys—Part 2: Determination of silver content English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS 97.120.99
CCS H 57
National Standard of the People's Republic of China
GB/T 15072.2-2025
Replaces GB/T 15072.2-2008,GB/T 15072.5-2008
Method for chemical analysis of precious metal alloys - Part 2: Determination of silver content
Issue date: 2025-08-29 Implementation date: 2026-03-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
Introduction
1 Scope
2 Normative References
3 Terms and Definitions
4 Method 1: Potentiometric Titration with Sodium Chloride (NaCl)
5 Method 2: Potentiometric Titration with Potassium Iodide (KI)
6 Method 3: Fire Assay Gravimetry
Method for chemical analysis of precious metal alloys - Part 2: Determination of silver content
Warning—Personnel using this document should have practical laboratory experience. This document does not address all potential safety issues. Users are responsible for implementing appropriate safety and health measures and ensuring compliance with national regulatory requirements.
1 Scope
This document describes methods for determining silver content in precious metal alloys using: Potentiometric titration with sodium chloride (NaCl), Potentiometric titration with potassium iodide (KI), Fire assay gravimetry
The NaCl potentiometric titration method and fire assay gravimetry are applicable to precious metal alloys excluding gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os).
NaCl method range: 3.00%–99.50% (mass fraction), Fire assay range: 2.00%–99.50% (mass fraction), KI method range: 3.00%–99.50% (mass fraction) for all precious metal alloys.
2 Normative References
The following documents contain provisions essential to this document through normative citations. Dated references: Only the cited version applies. Undated references: The latest version (including amendments) applies.
GB/T 6682 Specifications and Test Methods for Water used in Analytical Laboratories
GB/T 8170 Rules for Rounding off Numerical Values and Representation of Limit Values
3 Terms and Definitions
No terms require definition in this document.
4 Method 1: Potentiometric Titration with Sodium Chloride (NaCl)
4.1 Principle
The sample is dissolved in nitric acid. In nitric acid medium, silver is titrated with a standard NaCl solution using potentiometric detection. The silver content is calculated based on the consumed volume of NaCl solution.
4.2 Reagents and Materials
Unless otherwise specified, only analytical-grade reagents and Grade 2 water (per GB/T 6682) shall be used.
4.2.1 Silver metal (wAg ≥ 99.99%).
4.2.2 Nitric acid (ρ = 1.42 g/mL), GR.
4.2.4 Standard NaCl titrant [c(NaCl) ≈ 0.0001 mol/L].
Preparation:
a) Dissolve 5.845 g NaCl (GR) in water, dilute to 1 L, and mix thoroughly.
4.2.4 Standardization of NaCl Standard titrant
(b) Standardization:
Procedure:
Place 3 portions of silver standard solution (4.2.5) on an automatic potentiometric titrator (equipment parameters in Appendix A).
Titrate with the NaCl standard titrant until endpoint is reached.
Determine the endpoint from the potentiometric titration curve or dE/dV curve.
The maximum difference between the consumed volumes of NaCl titrant for the 3 parallel titrations shall not exceed 0.050 mL.
Calculate the average volume.
Actual concentration (c₀) of NaCl titrant is calculated using Equation (1):
c₀ = actual concentration of NaCl titrant (mol/mL)
m₀ = mass of silver weighed (g)
107.87 = molar mass of silver (g/mol)
V₀ = volume of NaCl titrant consumed during standardization (mL)
4.2.5 Silver standard solution
Preparation:
Weigh 0.2000 g of silver metal (wAg ≥ 99.99%, ±0.00001 g) into a 100 mL beaker.
Add 1.5 mL nitric acid solution (4.2.3) and cover with a watch glass.
Heat until complete dissolution, then remove nitrogen oxides by evaporation.
Cool to room temperature.
Rinse the watch glass and beaker walls with water.
4.3 Apparatus
4.3.1 Balance with 0.01 mg sensitivity.
4.3.2 Titration system: Automatic potentiometric titrator (see Appendix A for parameters).
4.3.3 Silver-composite electrode.
4.4 Sample preparation
Processing:
Crush sample into shreds with:
Thickness ≤ 0.2 mm
Length & width ≤ 2.0 mm
Cleaning:
Soak in ** glacial acetic acid** for 10 min.
Rinse with anhydrous ethanol, dry, and mix thoroughly.
4.5 Procedure
4.5.1 Sample portioning
Weigh sample according to Table 1, ±0.00001 g.
Standard
GB/T 15072.2-2025 Method for chemical analysis of precious metal alloys—Part 2: Determination of silver content (English Version)
Standard No.
GB/T 15072.2-2025
Status
to be valid
Language
English
File Format
PDF
Word Count
10500 words
Price(USD)
315.0
Implemented on
2026-3-1
Delivery
via email in 1~5 business day
Detail of GB/T 15072.2-2025
Standard No.
GB/T 15072.2-2025
English Name
Method for chemical analysis of precious metal alloys—Part 2: Determination of silver content
GB/T 15072.2-2025 Method for chemical analysis of precious metal alloys—Part 2: Determination of silver content English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS 97.120.99
CCS H 57
National Standard of the People's Republic of China
GB/T 15072.2-2025
Replaces GB/T 15072.2-2008,GB/T 15072.5-2008
Method for chemical analysis of precious metal alloys - Part 2: Determination of silver content
Issue date: 2025-08-29 Implementation date: 2026-03-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
Introduction
1 Scope
2 Normative References
3 Terms and Definitions
4 Method 1: Potentiometric Titration with Sodium Chloride (NaCl)
5 Method 2: Potentiometric Titration with Potassium Iodide (KI)
6 Method 3: Fire Assay Gravimetry
Method for chemical analysis of precious metal alloys - Part 2: Determination of silver content
Warning—Personnel using this document should have practical laboratory experience. This document does not address all potential safety issues. Users are responsible for implementing appropriate safety and health measures and ensuring compliance with national regulatory requirements.
1 Scope
This document describes methods for determining silver content in precious metal alloys using: Potentiometric titration with sodium chloride (NaCl), Potentiometric titration with potassium iodide (KI), Fire assay gravimetry
The NaCl potentiometric titration method and fire assay gravimetry are applicable to precious metal alloys excluding gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os).
NaCl method range: 3.00%–99.50% (mass fraction), Fire assay range: 2.00%–99.50% (mass fraction), KI method range: 3.00%–99.50% (mass fraction) for all precious metal alloys.
2 Normative References
The following documents contain provisions essential to this document through normative citations. Dated references: Only the cited version applies. Undated references: The latest version (including amendments) applies.
GB/T 6682 Specifications and Test Methods for Water used in Analytical Laboratories
GB/T 8170 Rules for Rounding off Numerical Values and Representation of Limit Values
3 Terms and Definitions
No terms require definition in this document.
4 Method 1: Potentiometric Titration with Sodium Chloride (NaCl)
4.1 Principle
The sample is dissolved in nitric acid. In nitric acid medium, silver is titrated with a standard NaCl solution using potentiometric detection. The silver content is calculated based on the consumed volume of NaCl solution.
4.2 Reagents and Materials
Unless otherwise specified, only analytical-grade reagents and Grade 2 water (per GB/T 6682) shall be used.
4.2.1 Silver metal (wAg ≥ 99.99%).
4.2.2 Nitric acid (ρ = 1.42 g/mL), GR.
4.2.4 Standard NaCl titrant [c(NaCl) ≈ 0.0001 mol/L].
Preparation:
a) Dissolve 5.845 g NaCl (GR) in water, dilute to 1 L, and mix thoroughly.
4.2.4 Standardization of NaCl Standard titrant
(b) Standardization:
Procedure:
Place 3 portions of silver standard solution (4.2.5) on an automatic potentiometric titrator (equipment parameters in Appendix A).
Titrate with the NaCl standard titrant until endpoint is reached.
Determine the endpoint from the potentiometric titration curve or dE/dV curve.
The maximum difference between the consumed volumes of NaCl titrant for the 3 parallel titrations shall not exceed 0.050 mL.
Calculate the average volume.
Actual concentration (c₀) of NaCl titrant is calculated using Equation (1):
c₀ = actual concentration of NaCl titrant (mol/mL)
m₀ = mass of silver weighed (g)
107.87 = molar mass of silver (g/mol)
V₀ = volume of NaCl titrant consumed during standardization (mL)
4.2.5 Silver standard solution
Preparation:
Weigh 0.2000 g of silver metal (wAg ≥ 99.99%, ±0.00001 g) into a 100 mL beaker.
Add 1.5 mL nitric acid solution (4.2.3) and cover with a watch glass.
Heat until complete dissolution, then remove nitrogen oxides by evaporation.
Cool to room temperature.
Rinse the watch glass and beaker walls with water.
4.3 Apparatus
4.3.1 Balance with 0.01 mg sensitivity.
4.3.2 Titration system: Automatic potentiometric titrator (see Appendix A for parameters).
4.3.3 Silver-composite electrode.
4.4 Sample preparation
Processing:
Crush sample into shreds with:
Thickness ≤ 0.2 mm
Length & width ≤ 2.0 mm
Cleaning:
Soak in ** glacial acetic acid** for 10 min.
Rinse with anhydrous ethanol, dry, and mix thoroughly.
4.5 Procedure
4.5.1 Sample portioning
Weigh sample according to Table 1, ±0.00001 g.
