Infrared spectroscopy of double-four-ring silicates

Attenuated—total—reflection infrared spectroscopy has been applied to characterize tetramethylammonium double-four-ring silicates in solution as well as in hydrate crystals. It is shown that tetramethylammonium silicate solutions at elevated temperatures (up to 85°C) still contain significant concentrations of double-four-ring silicate anions. Furthermore, the temperature-dependent shift in equilibrium between silicate anions appears to be fully reversible. A relation to the role of silicate anions in zeolite syntheses is suggested.