Process for producing alumina of low soda content

Claim 1

PROCEDURE FOR PURIFICATION OF ALUMINA TO REMOVE SODA, COMPRISING SUPPLYING A QUANTITY OF ALUMINA IN DIVIDED FORM TO A CALCINING REGION WHICH HAS A DISCHARGE LOCALITY FOR REMOVAL OF CALCINED PRODUCT, CALCINING SAID QUANTITY OF ALUMINA IN SAID REGION WITH A FLUORIDE MINFRALIZER WHICH IS A SUBSTANCE THAT HAS THE CHARACTERISTIC OF PRODUCING SUBSTANTIALLY RECRYSTALLIXED ALUMINA DURING SAID CALCINATION, SAID SUBSTANCE ALSO HAVING THE CHEMICAL CHARACTERISTIC OF REACTING WITH THE SODA CONTENT OF SAID ALUMINA TO FORM A WATER SOLUBLE SODIUM SALT DURING SAID CALCINATION, SAID CALCINING STEP COMPRISING HEATING SAID QUANTITY OF ALUMINA IN THE PRESENCE OF SAID MINERALIZER TO A TEMPERATURE OF AT LEAST ABOUT 1000*C., TO PRODUCE SAID ALUMINA IN SAID SUBSTANTIALLY RECRYSTALLIZED FORM AS ALPHA ALUMINA CONTAINING AN UNVOLATILIZED RESIDUE OF A WATER-SOLUBLE FLUORIDE SALT OF SODIUM, DISCHARGING AT THE AFORESAID LOCALITY SUBSTANTIALLY THE ENTIRETY OF SAID QUANTITY OF ALUMINA IN ITS SAID CALCINED RECRYSTALLIZED FORM, SAID MINERALIZER REACTING WITH SAID SODA OF THE ALUMINA DURING CALCINATION TO PRODUCE A QUANTITY OF SAID LASTMENTIONED SALT WHICH REMAINS UNVOLATILIZED IN SAID DISCHARGED ALUMINA, AND REMOVING SUCH SALT BY SUBJECTING SAID RECRYSTALLIZED ALUMINA, WHICH WAS DISCHARGED AS AFORESAID IN CALCINED FORM, TO LEACHING WITH AQUEOUS LIQUID SELECTED FROM THE CLASS CONSISTING OF DILUET WATER SOLUTIONS OF MINERAL ACIDS, DILUTE WATER SOLUTIONS OF INORGANIC ALKALIS, AND PLAIN WATER, SAID SOLUTIONS OF ACIDS AND SAID SOLUTIONS OF ALKALIS EACH HAVING A CONCENTRATION OF LESS THAN 5%.