Comparison of Methods for Determining Specific Surface Area of Soils

The present study was undertaken to compare the capabilities of four of the known methods; more specifically, N2 adsorption, methylene blue (MB)-titration, MB-spot test, and ethylene glycol monoethyl ether (EGME) methods were evaluated to determine the specific surface area (SSA) of 16 different clayey soils. The study showed that N2 adsorption method underpredicts the SSA of soils, especially for smectitic soils. No significant differences were observed between N2 SSA, MB SSA-titration, or MB-spot test for kaolinitic soils. The SSA estimates of MB-titration and MB-spot test methods were highly correlated for all soils. The EGME method has a very different procedure from the MB methods; however, it was highly correlated with MB methods (r^2=0.95). The N2 adsorption method had no correlation to other methods. The cation exchange capacity of tested soils was highly correlated to the SSA, as high as r^2=0.77. No unique relationship was determined between the clay fraction and SSA.