Crystal Structure And Thermal Properties Of A New Double Salt: K2sif6 Center Dot Kno3

A new double salt K2SiF6 center dot KNO3 was found during determination of the solubility of K2SiF6 in aqueous potassium nitrate solutions. Unit cell parameters (P6(3)/mmc, a = 5.6268(1) A, c = 14.5186(6) angstrom, V = 398.09(2) angstrom(3), Z = 2) and crystal structure have been determined. The compound is further characterized by RAMAN spectroscopy and X-ray powder diffraction. Thermal properties were studied using DTA, DSC and in situ high-temperature X-ray powder diffraction measurements. At 287 degrees C K2SiF6 center dot KNO3 decomposes into its components KNO3 and K2SiF6 with an enthalpy of decomposition of about + 42 J.g(-1). Further thermal effects could be assigned to phase transformations of KNO3 whereby earlier literature data have been reconfirmed. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.