1. A PROCESS FOR CLASSIFYING A CALCINED PIGMENT CONTAINING TITANIUM DIOXIDE PARTICLES, WHICH COMPRISES, TREATING AN AQUEOUS SLURRY OF THE PIGMENT WITH A QUANTITY OF AN ALKALINE-REACTING DISPERSING AGENT SUFFICIENT TO RAISE THE PH OF THE SLURRY TO AT LEAST 8.0, AND DISPERSE THE PIGMENT IN THE SLURRY THEREAFTER ADDING TO THE SLURRY A SUFFICIENT QUANTITY OF AN ACID-REACTING REAGENT TO REDUCE THE PH OF THE SLURRY TO A VALUE WITHIN THE RANGE OF FROM 6.6 TO 7.6 AND PROVIDE A DISPERSED SLURRY WHICH DOES NOT BECOME THIXOTROPIC UNDER SUBSEQUENT CLASSIFICATION, AND SUBJECTING THE RESULTING DISPERSED SLURRY TO CENTRIFUGAL HYDROCLASSIFICATION TO SEPARATE FINE PARTICLES FROM COARSE PARTICLES.