"The magnetic properties of color centers were studied to obtain information regarding electron traps in insulators. Experiments designed to determine the equation governing the recovery of resonance after saturation were carried out. Relatively large samples were prepared by the method of additive coloration. KCl and RbCl crystals were used. Resonance saturation as a function of concentration was investigated and no significant dependence found. Measurements of the unsaturated susceptibility were made at liquid nitrogen and liquid helium temperatures. The bleaching of the F-center to form the B-band produced a different resonance. The equipment for observing the saturation and recovery of a portion of the resonance at 4 deg K is described. A theoretical examination was made of the interaction between the vibration of the ions around a negative-ion vacancy in an alkali halide and an electron trapped at that site. (M.C.G.)."