Write the principle behind the froth floatation process. What is the role of collectors in this process?

Froth floatation process is based on the principle that the metallic sulphide particles of ore are preferentially wetted by oil and the gangue particles by water.
Collectors attach themselves by polar groups to grains of minerals which then become water repellent and thus, pass on into the froth. Examples are ethyl xanthate and potassium ethyl xanthate.