Describe the principal of forth flotation process, What is the role of a stabilizer and of a depressant?
Give one example each.

Forth floatation process is based on the fact that the sulphide ore particles are only moistened with oil, whereas oxide and gangue particles are moistened by water. For, the powdered ore is mixed with water and a little pine oil and whole mixture is then stirred vigorously through rotating paddle by blowing compressed air. The oil forms a foam or forth with air. The ore particles stick to the forth and rises to the surface, while gangue are left in water. The forth is skimmed off, collected and allowed to subside to get concentrated ore. 

This is especially suitable for sulphide ores.

Role of stabilizer - Stabilizers are used to stabilize the forth.

Example Cresols and aniline. 

Role of depressant - Depressants are used to prevent certain type of particles from forming the froth with bubbles. Example. NaCN can le used as a depressant in the separation of ZnS and PbS.