This study was undertaken to establish an industrial process for the preparation of low-soda alumina useful in the manufacture of electronic ceramics. First, starting material, Al(OH)₃, was admixed with the chlorine-containing compounds. NH₄Cl or HCl, employed as the treating agent for reducing the soda in starting material, and then admixture was calcined at a temperature sufficient to eliminate the soda as a volatilizable compound which was produced by reaction of the soda and the above mentioned treating agents. This treatment is so-called the volatilization method. The results obtained in the study show that addition amount of treating agents has an enormous effect on the elimination of soda, and that optimum addition amount of NH₄Cl and HCl is 2.43 and 8.38(mole of treating agent/mole of Na₂O),respectively.