1, chlorination purification is more suitable for gold powder purification, and larger gold nuggets need to be splashed into small particles or pressed into thin sheets with beads to speed up chlorination. Hydrochloric acid+salt+hydrogen peroxide, hydrochloric acid+salt+chlorine, hydrochloric acid+salt+perchloric acid.

2. Heat to remove oxidizing gases: hydrogen peroxide and chlorine. Filtering to remove nonmetallic substances, and washing the filter residue with water for many times. The reducing gold-bearing liquid is acidic, and crystalline sodium sulfite or sulfur dioxide gas is used. Boil with nitric acid or concentrated sulfuric acid-remove impurities 6. The melting purity can reach 99.9%.

3. Electrolytic purification of gold Electrolytic purification is a common method. Using alloy gold as anode, pure gold or stainless steel as cathode and concentrated hydrochloric acid as electrolyte, the purity can reach 99.95%. Change the electroplating solution in time. Slow speed, long working hours and high power consumption.

4. Chloramine method and ammonium chloride method are more suitable for purifying gold powder. Larger gold nuggets need to be splashed into small particles with beads or pressed into thin sheets to accelerate chlorination.

5. Filtering to remove nonmetallic substances, washing filter residue with water for many times, and adding ammonia water to adjust pH = 135. Gold-loaded solution is alkaline, and formaldehyde can be used as reducing agent. Boil with nitric acid or concentrated sulfuric acid-remove impurities.