When using sodium sulfide as a sulfiding agent, the dosage, pulp pH, pulp temperature, and stirring time must be strictly controlled.

(1) The dosage must be appropriate. Insufficient dosage will result in incomplete mineral sulfidation; excessive dosage will inhibit the sulfidation of the minerals due to excess sodium sulfide.

(2) The optimal pulp pH range for sulfidation varies for different minerals. Practice has shown that cerussite exhibits the fastest sulfidation rate at a pH of 9–10, while malachite shows the best sulfidation effect at a pH of 8.5–9.5.

(3) Pulp temperature has a significant impact on the sulfidation reaction; the sulfidation rate generally increases with increasing temperature.

(4) The stirring time must be appropriate. Longer stirring times result in a thicker sulfide film on the mineral surface, which is beneficial for flotation. However, excessive stirring time will oxidize the sodium sulfide and the sulfide film on the mineral surface, reducing the sulfidation effect. Vigorous stirring can cause the sulfide film to detach. To avoid excessively high local mass fractions and excessively long stirring times, sodium sulfide is often added in stages and batches.