Brightness of crystalline layered silicate minerals

Claim 1

A METHOD FOR BLEACHING KAOLIN CLAY CONTAINING AS AN IMPURITY A FERRIC COMPOUND WHICH IS NOT REMOVED THEREFROM BY A DITHIONITE BLEACHING REFENT WHICH COMPRISES FORMING A SUSPENSION OF SAID CLAY WTH A DILUTE SOLUTION IN DIMETHYLSULFOXIDE OF A COMPLEXING LIGAND SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL THIOYANATE, AMMONIUM THIOCYANATE, ACETYLACETONE, O-PHENANTHROLINE, BIPYRIDINE, ETHYLENEDIAMINE, MERCAPTOACETIC ACID, THIOMALIC ACID, MERCAPTOETHANOL AND MIXTURES THEREOF, SAID COMPLEXING AGENT BEING PRESENT IN AMOUNT TO REACT WITH SAID FERRIC COMPOUND IN SAID CLAY TO FORM A COLORED COORDINATION COMPLEX AND SAID DIMETHYLSULFOXIDE BEING PRESENT IN AMOUNT SUBSTANTIALLY IN AXCESS OF 1 MOLE PER EQUILAVENT OF SAID CLAY AND SUFFICIENT TO MAINTAIN A LIQUID PHASE OF DIMETHYLSULFOXIDE AFTER SAID REACTION IS COMPLETED, MAINTAININ SAID SUSPENSION UNDER CONDITIONS OF TIME AND TEMPERATURE WHICH FAVOR FORMATION OF A KAOLINITE-DIMETHYLSULFOXIDE INTERCLATION COMPOUND UNTIL A COLORED COORDINATION COMPLEX IS FORMED BY REACTION BETWEEN FERRIC IONS IN THE IMPURITY AND SAID COMPLEXING LIGEND, SEPARATING THE CLAY FROM A LIQUID PHASE, AND WASHING THE SEPARATED CLAY WITH WATER TO DECOMPOSE THE KALINITEDIMETHYLSULFOXIDE COMPLEX AND RESTORE THE CRYSTAL STRUCTURE TO THE CLAY.

Claim 2

A METHOD FOR BLEACHING KAOLIN CLAY CONTAINING AS AN IMPURITY A FERRIC COMPOUND WHICH IS NOT REMOVED THEREFROM BY A DITHIONITE BLEACHING REFENT WHICH COMPRISES FORMING A SUSPENSION OF SAID CLAY WTH A DILUTE SOLUTION IN DIMETHYLSULFOXIDE OF A COMPLEXING LIGAND SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL THIOYANATE, AMMONIUM THIOCYANATE, ACETYLACETONE, O-PHENANTHROLINE, BIPYRIDINE, ETHYLENEDIAMINE, MERCAPTOACETIC ACID, THIOMALIC ACID, MERCAPTOETHANOL AND MIXTURES THEREOF, SAID COMPLEXING AGENT BEING PRESENT IN AMOUNT TO REACT WITH SAID FERRIC COMPOUND IN SAID CLAY TO FORM A COLORED COORDINATION COMPLEX AND SAID DIMETHYLSULFOXIDE BEING PRESENT IN AMOUNT SUBSTANTIALLY IN AXCESS OF 1 MOLE PER EQUILAVENT OF SAID CLAY AND SUFFICIENT TO MAINTAIN A LIQUID PHASE OF DIMETHYLSULFOXIDE AFTER SAID REACTION IS COMPLETED, MAINTAININ SAID SUSPENSION UNDER CONDITIONS OF TIME AND TEMPERATURE WHICH FAVOR FORMATION OF A KAOLINITE-DIMETHYLSULFOXIDE INTERCLATION COMPOUND UNTIL A COLORED COORDINATION COMPLEX IS FORMED BY REACTION BETWEEN FERRIC IONS IN THE IMPURITY AND SAID COMPLEXING LIGEND, SEPARATING THE CLAY FROM A LIQUID PHASE, AND WASHING THE SEPARATED CLAY WITH WATER TO DECOMPOSE THE KALINITEDIMETHYLSULFOXIDE COMPLEX AND RESTORE THE CRYSTAL STRUCTURE TO THE CLAY.