Precipitation of aluminum oxide having low sodium oxide content

Claim 1

The process of producing an aluminum oxide having a sodium oxide content after calcining of less than 0.1% by weight which comprises: a. continuously precipitating aluminum oxide in a first tank maintained at a temperature of 55°-80° C and an alumina-to-caustic ratio of 0.68 while 1. adding feed liquor at an alumina-to-caustic ratio of 1.04 into said tank at a flow rate in liters per minute equal to approximately 0.043% of the volume of said tank; and 2. simultaneously adding aluminum hydroxide seed slurry to said tank at a rate in meters 2 per hour to maintain a precipitation rate in said tank of less than 0.03 grams Al 2 O 3 per hour per meter 2 of said aluminum hydroxide seed added to the tank per hour; b. feeding the resultant precipitate slurry from said first tank to a second tank maintained at a temperature of about 70° C at a flow rate in liters per minute equal to 0.115% of the volume of said second tank to maintain an alumina-to-caustic ratio of about 0.61 in said second tank; and c. recovering a low soda aluminum hydroxide precipitate from said second tank characterized by a sodium oxide content after calcining of less than 0.1% by weight.