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Thermal dehydration of the double salts K 2 Be(XO 4 ) 2 ·2H 2 O (X = S, Se)
Author(s) -
Georgiev M. P.,
Stoilova D. G.,
Marinova D. M.,
Karadjova V. A.
Publication year - 2007
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200610770
Subject(s) - chemistry , selenate , anhydrous , monoclinic crystal system , double salt , tetragonal crystal system , lattice energy , sulfate , dehydration , differential thermal analysis , raman spectroscopy , hydrogen bond , inorganic chemistry , thermal analysis , halide , infrared spectroscopy , crystallography , crystal structure , molecule , selenium , thermal , organic chemistry , diffraction , biochemistry , physics , optics , meteorology
The thermal dehydration of the title compounds was studied by TG, DTA and DSC methods and the enthalpies of dehydration were calculated (87.6 kJ mol –1 and 167.5 kJ mol –1 for the sulfate and selenate compound, respectively). The larger value of ΔH deh of K 2 Be(SeO 4 ) 2 ·2H 2 O is due to the stronger hydrogen bonds formed in the selenate as compared to those formed in the respective sulfate owing to the stronger proton acceptor capabilities of the SeO 4 2– ions. The enthalpies of formation (ΔH f 0 ) of the dihydrates are also calculated from the DSC measurements (– 4467.4 kJ mol –1 and – 3447.1 kJ mol –1 for the sulfate and selenate compound, respectively). The anhydrous double salt, K 2 Be(SO 4 ) 2 , forms tetragonal crystals with lattice parameters: a = 7.232(2) Å; c = 14.168(2) Å; V = 741.0 Å 3 , while the anhydrous salt, K 2 Be(SeO 4 ) 2 , forms monoclinic crystals with lattice parameters: a = 9.217(3) Å; b = 10.645(3) Å; c = 8.989(2) Å; β = 108.52(4)°; V = 836.2 Å 3 . Vibrational spectra (infrared and Raman) of both the dihydrates and the anhydrous compounds are also presented and discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)