Solution 2:
The role of depressant is to prevent one type of sulphide ore particles from forming the froth with air bubbles. is used as a depressant to separate lead sulphide
(PbS) ore from zinc sulphide ( ) ore. forms a zinc complex, on the surface of thereby preventing it from the formation of the froth.
Sodium tetracyno-
Zincate
In this condition, only lead sulphide forms froth and thus can be separated from zinc sulphide ore.