Abstract
Several previous studies of the hydration and dehydration process of laumontite have been performed, however, they have been carried out at room temperature without humidity-controlled conditions. The process is investigated by gravimetry and X-ray powder diffractometry under the conditions of controlled relative humidity (RH) at 25°C. The results show that laumontite has the following three phases in the atmosphere from 0 to 100%RH.(1) 12H2O phase (The phase contains ca. 12 water molecules per unit cell). The cell parameters are a=14.71 (1)Å, b=13.09 (1)Å, c=7.46 (1)Å and β=112.1 (1)°(0% RH).(2) 14H20 phase. The cell parameters are a=14.77 (1)Å, b=13.09 (1)Å, c=7.58 (1)Å and β=112.0 (2)°(50%RH).(3) 16-18H20 18H20 phase. The cell parameters are a=14.90 (2)Å, b=13.19 (1)Å, c=7.55 (1)Å and β=110.2 (1)°(100% RH).
