1. Introduction.- 2. Chemical Bonding and Structure of Solids.- 3. Aqueous Solutions, Slurries and Pulp.- 4. Physical Chemistry of Interfaces.- 5. Electrical Characteristics at Interfaces.- 6. Surface Forces in Flotation.- 7. Adsorption from Solutions.- 8. Hydrophobicity and Contact Angle.- 9. Flotation Surfactants.- 10. Collector Mechanism I. Thiol Collectors in Sulfide Minerals.- 11. Collector Mechanism II. Non-Thiol Collectors.- 12. Mechanism of the Action of Modifying Agents.- 13. Frothers and Frothing.- 14. Flotation Kinetics and Fine Particles Flotation.- References.- References.