Thermogravimetric analysis was applied to the characterisation of the porosity of silica gel. Thermal desorption of liquids from silicas for column chromatography was measured. Water and n-hexane were used as liquid adsorbates. Pore size distribution curves of silica gels were determined on the basis of thermogravimetric curves using Kelvin equation. The resulting distributions and total pore volumes were compared with those obtained from the nitrogen method. The influence of polarity of adsorptives on the porosity parameters of silica gels and on the shape of pore size distribution curves is discussed.