YS/T 521.2-2019 in English

This standard specifies two methods for determining the gold and silver content in crude copper: Method 1 dry and wet fire assay (arbitration method) and Method 2 direct fire assay. The technological evolution is mainly reflected in:

• Direct fire assay as an optional method
• Gold determination range expanded from 0.5g/t to 340.00g/t
• Silver determination method added titration method and weight reduction method

1. Sample preparation

The sample needs to be crushed to a particle size ≤0.074mm. Method 1 requires 20g to be weighed according to the screening ratio, and method 2 requires 10g.

2. Melting process control

• Dry and wet method: heat from 950℃ to 1100℃ and keep warm for 15min
• Direct method: heat from 900℃ to 1100℃ and keep warm for 20min

3. Gold separation technology

When the gold-silver ratio is >1:3, it is necessary to add metal silver (3-5 times the total particle weight) to ensure complete separation.

Take gold content of 16.93g/t as an example:

• Repeatability limit (r): 1.00g/t
• Reproducibility limit (R): 1.20g/t

When the silver content is 1181.3g/t:

• Repeatability limit (r): 23.5g/t
• Reproducibility limit (R): 56.9g/t

1. For high silver content (>2000g/t), the weight reduction method is preferred.
2. Regular verification>Potassium thiocyanate standard solution concentration (calibrated weekly)
3. The ash blowing temperature is strictly controlled at 840±5℃
4. Use ultra-micro balance (0.0001mg accuracy) to weigh the mixed particles