Crystal structure and thermal properties of a new double salt: K2SiF6·KNO3

Abstract A new double salt K 2 SiF 6 ·KNO 3 was found during determination of the solubility of K 2 SiF 6 in aqueous potassium nitrate solutions. Unit cell parameters (P6 3 /mmc, a = 5.6268(1) Å, c = 14.5186(6) Å, V = 398.09(2) Å 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 °C K 2 SiF 6 ·KNO 3 decomposes into its components KNO 3 and K 2 SiF 6 with an enthalpy of decomposition of about + 42 J·g ‐1 . Further thermal effects could be assigned to phase transformations of KNO 3 whereby earlier literature data have been reconfirmed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)