an equivalent weight to ti and al or less to form a precipitate the precipitate is washed to remove impurities and fired at about 200 u00b0 to 1 000 u00b0 c further the titanium oxide based solid solution and the aluminum oxide based solid solution may be produced as follows an organic compound of titanium and an organic compound of aluminum are dissolved in an organic solvent such that an intended ti al atomic ratio is obtained and then hydrolyzed by adding water the resultant precipitate is recovered and then fired at about 200 u00b0 to 1 000 u00b0 c examples of the above organic compound of titanium are ti o ch 2 3 ch 3 4 ti oc 4 h 9 n 4 ti och ch 3 2 4 c 2 h 5 2 ticl 2 ti och 2 ch c 2 h 5 c 4 h 9 4 ti o iso c 3 h 7 2 oc ch 3 chcoch 3 2 ti o normal c 4 h 9 2 oc 2 h 4 c 2 h 4 oh 2 2 and the like examples of the above organic compound of aluminum are al och ch 3 2 3 al ch 3 ch 2 10 coo 3 al o ch 2 3 ch 3 3 and the like examples of the above organic solvent are isopropanol n hexane benzene toluene methyl chloroform carbon tetrachloride and the like the purifier of this invention may have a powder form however it is preferably granulated into a spherical or cylindrical form having a diameter of 1 to 50 mm a granulated purifier has advantages that the resistance of the purifier to.