Process for obtaining chromic oxide from a chromate ore

Claim 1

A PROCESS FOR PRODUCING CHROMIC OXIDE FROM A CHROME ORE COMPRISING ROASTING THE ORE WITH SODIUM CARBONATE, LEACHING THE ROASTED ORE TO PROVIDE A SODIUM CHROMATE SOLUTION CONTAINING SODIUM CARBONATE, CARBONATING THE SOLUTION TO CONVERT SOLUBLE SODIUM SILICATE AND ALUMINATE TO INSOLUBLE SILICA AND ALUMINUM HYDROXIDE AND SOLUBLE SODIUM CARBONATE, FILTERING OFF THE SILICA AND ALUMINUM HYDROXIDE, EVAPORATING THE FILTRATE IN AN EVAPORATOR AT A TEMPERATURE BELOW 116* C. WHILE REDUCING THE SODIUM CARBONATE CONTENT OF THE FINAL DRY SODIUM CARBONATE-SODIUM CHROMATE MIXTURE BY REMOVING FROM THE EVAPORATOR SODIUM CARBONATE MONOHYDRATE SALTING OUT IN THE EVAPORATOR UNTIL SUBSTANTIALLY ONLY A SODIUM CHROMATE SOLUTION REMAINS, CONTINUING THE EVAPORATION OF SAID SOLUTION AT A TEMPERATURE ABOVE 116* C. TO SALT OUT ANHYDROUS SODIUM CHROMATE, RECOVERING SUBSTANTIALLY DRY CRYSTALLIZED SODIUM CHROMATE WITH SUBSTANTIALLY REDUCED SODIUM CARBONATE CONTENT FROM THE EVAPORATOR, MIXING THE DRY SODIUM CHROMATE WITH ABOUT 9% TO 30% OF A DRY, FINELY