Heat of immersion of thermally treated silica gel

Abstract

The heat of immersion of thermally treated silica gel in water, aliphatic alcohols and other organic compounds was studied. Silica gel was heathyphen;treated in the range from ≈ 450 K to the temperature above which a vigorous change in properties occurred by sintering. Heat treatment was performed in gases such as helium, oxygen, air and water, and a vacuum of ≈ 0.1 N m^–2; a known amount of Na⁺ ion impurity was present in silica gel to be treated. The values of heat of immersion in water, aliphatic alcohols, aromatic compounds and compounds with dipole moments were proportional to the number of OH groups per unit surface area in the range 0 to ≈ 4 OH groups per nm². This relation is discussed with respect to the surface and pore structures of silica gel.