throughout the suspension and are recovered in the froth The sign of the surface charge for alkali halides in their satuphase during flotation. Other particles which do not adsorb rated brines has been established from nonequilibrium electrophothe collector are maintained in a hydrophilic state and remain resis measurements, and on this basis the flotation response of in suspension, and separation is thus achieved. alkali halides was explained based on the adsorption of oppositely charged collector colloids by heterocoagulation. These surface Lattice Ion Hydration Theory and Flotation Chemistry charge results for alkali halides are generally as expected from The difference in the floatability of KCl and NaCl is amazsimplified lattice ion hydration theory with some exceptions, speing in view of the fact that these two alkali halides are so cifically LiF, KCl, NaCl, KBr, RbBr, KI, and RbI. The presence of natural oxygen defect states in the crystal lattice and the inaccu-similar chemically and crystallographically. Several hypothracies involved in the gaseous ion hydration free energy values eses have been advanced in the past to explain collector used appear, in the past, to be responsible for these deviations. adsorption phenomena observed in soluble salt flotation sys-The presence of natural oxygen defect states in KCl, KBr, RbBr, tems, with little agreement (4-11). However, results from and RbI, as characterized by UV/Vis absorption, was found to recent research at the University of Utah indicate that collecaccount for their anomalous surface charge. Further, other positor adsorption in soluble salt flotation with alkyl amines and tively charged alkali halides, LiF, NaCl, and KI, were found to carboxylates can best be explained by the heterocoagulation be free of oxygen defect states. Nevertheless, oxygen defects can of the oppositely charged collector colloids and soluble salt be created in these alkali halides to make them negatively charged, mineral particles (12-17). Based on nonequilibrium elecand this has been demonstrated for NaCl. Such negatively charged trokinetic measurements for alkali halides by laser-Doppler NaCl can be readily floated with positively charged amine collector electrophoresis reported by Miller et al. (13), the sign of colloids, thus confirming the surface charge/collector colloid adsorption theory.