Concentrating silica sols without particle growth

Claim 1

IN A PROCESS FOR PRODUCING A CONCENTRATED, AQUEOUS SILICA SOL IN WHICH THE SILICA IS PRESENT AS UNIFORMLY SIZED PARTICLES IN THE SIZE RANGE OF 4 TO 10 MILLIMICRONS, THE STEPS COMPRISING PREPARING SEPARATE BODIES OF AN AQUEOUS SILICA SOL CONTAINING LESS THAN 10 PERCENT BY WEIGHT OF SILICA, THE SILICA BEING IN THE FORM OF PARTICLES NO LARGER THAN THE SIZE DESIRED IN THE FINAL PRODUCT AND EACH BODY OF SOL HAVING A PH IN THE RANGE OF 7.0 TO 10.5, SIMULTANEOUSLY HEATING THE SOL BODIES TO A TEMPERATURE IN THE RANGE OF 50 TO 150*C. AND, WHILE MAINTAINING THE SEPARATE BODIES AT SUBSTANTIALLY THE SAME TEMPERATURE. EVAPORATING WATER FROM ONE BODY OF SOL, ADDING SOL FROM THE SECOND BODY TO REPLACE THE EVAPORATED WATER AND KEEP THE VOLUME OF THE FIRST BODY SUBSTANTIALLY CONSTANT, AND CONTINUING THE EVAPORATION AND REPLACEMENT AT CONSTANT VOLUME UNTIL THE SILICA CONTENT OF THE FIRST BODY OF SOL IS FROM 10 TO 50 PERCENT SIO2.