GB/T 7739.1-2019 in English
VALIDMethods for chemical analysis of gold concerntrates—Part 1：Determination of gold and silver contents
- Issued on:2019-12-31
- Implemented on:2020-11-01
- File Format:PDF
- Delivery:Within 1 day
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《GB/T 7739.1-2019金精矿化学分析方法 第1部分：金量和银量的测定》由TC379（全国黄金标准化技术委员会）归口，主管部门为国家标准化管理委员会。
Introduction
Analysis of the core content of the standard
| Method | Principle | Determination range (g/t) | Main improvements |
|---|---|---|---|
| Method 1 | Fire assay gravimetric method | Gold 10.0-550.0 Silver 200.0-12000.0 | New silver content correction method Extended lower limit of determination |
| Method 2 | Activated carbon enrichment-atomic absorption | Gold 10.0-150.0 | New detection method |
| Method 3 | Activated carbon enrichment-iodine titration | Gold 10.0-150.0 | New detection method |
Key technical innovations
Main improvements compared with the 2007 version:
- The lower limit of gold determination is reduced from 20.0g/t to 10.0g/t
- Two methods of activated carbon enrichment system are added
- Silver content correction calculation formula is introduced (ash blowing loss coefficient method)
- The original tolerance requirement is replaced by precision clause
Key points of fire assay
Magnesia ash dish requires attention: cement: magnesia: water = 15:85:10 ratio, dry in the shade for 3 months before use. The following should be controlled during the melting stage:
- Initial heating at 800℃, and heat preservation at 930℃ for 15min
- Finally, maintain at 1100-1200℃ for 10min
- The mass of the lead button should be controlled within the range of 25-50g
Precision control requirements
Take the gold content of 44.7g/t as an example:
- Repeatability limit (r): ≤1.8g/t
- Reproducibility limit (R): ≤2.5g/t
When the silver content is 1036.6g/t:
- Repeatability limit (r): ≤30.1g/t
- Reproducibility limit (R): ≤50.3g/t
Implementation suggestions
1. For high copper samples, 30-50 times the amount of copper should be added with lead oxide
2. Activated carbon pretreatment needs to be soaked in ammonium bifluoride for 3 days
3. Ash blowing temperature should be strictly controlled at 880℃±20℃
4. It is recommended to verify the silver ash blowing loss coefficient regularly
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