Charcoal obtained from walnut shells were studied for determining the acidic surface complexes by selective neutralization technique using bases of different strengths. Effect of time, benzene extraction and demineralization on the uptakes of various bases by charcoal were investigat­ed and groups like carboxyl, lactone, phenolic, hydroxyl and keto-enol were thought to be present on the surface of charcoal. Uptakes of stronger bases sodium ethoxide and potassium isopropoxide were unexpectedly low, which were thought to be due to the bulky size of ethoxide and isopropoxide, which get access into the mi cropores with di ffi culty as compared to the smalls i zed hydroxide.