ofsilica gels prepared in the presence of Na+(Method I) and in theabsence of Na+(Method II). In the presence of Na+, the surfacearea of silica gels tended to decrease with the increase in pH. Onthe other hand, in the absence of Na+, it tended to increase whenincreasing pH, peaking at approximately 5 and decreasing after-ward. The surface area of silica gels prepared in the presence of Na+was larger than that of prepared in the absence of Na+at pH ≤ 4 andwas lower at pH > 4. For the silica gels prepared in the presence ofNa+, the surface area ranged from approximately 204 to 525 m2g−1.It ranged from approximately 380 to 430 m2g−1when prepared inthe absence of N