1. THE PROCESS OF TREATING CEMENT KILN FLUE DUST WHICH HAS THEREIN THEORETICAL ALKALIES WHICH ARE NOT READILY SOLUBLE IN AN AQUEOUS MEDIUM, WHICH COMPRISES HEATING THE DUST TO A TEMPERATURE OF AT LEAST 1000* F. IN AN OVEN FOR A TIME SUFFICIENT TO INCREASE THE SOLUBILITY OF THE ALKALIES IN AN AQUEOUS MEDIUM, TREATING THE RESULTANT HEATTREATED DUST WITH AN AQUEOUS MEDIUM TO DISSOLVE A SUBSTANTIAL AMOUNT OF THE WATER-SOLUBLE MATERIALS, AND SEPARATING SAID AQUEOUS MEDIUM FROM THE SOLID PARTICLES OF THE TREATED DUST.