Alkali antimony silicates as precursors to new inorganic acids

Two alkali antimony silicates, K 4 Sb 4 O 8 (Si 4 O 12 ) and Cs 3 Sb 3 O 6 (Si 2 O 7 ) with strongly covalent and rather open octa hedraltetrahedral frameworks have been ion exchanged in acidic medium. Their proton exchanged derivatives are hydrated and their water content has been studied at 20°C as a function of relative humidity. Both compounds are true lattice hydrates and their thermal behavior, studied with use of TGA and X-ray diffraction, indicates that their dehydration process is reversible up to about 400°C. Titrations with different alkali hydroxide solutions show that they behave as solid acids with ion exchange properties.