PHYSICO-CHEMICAL STUDIES OF CuNa₃P₃O₁₀ 12H₂O, CRYSTALLOGRAPHIC CHARACTERIZATION OF CuNa₃P₃O₁₀ AND QUANTUM CHEMICAL CALCULATIONS OF THE P₃O₁₀5- ION

摘要

A copper sodium triphosphate CuNa_(3)P_(3)O_(10) 12H_(2)O already known has been prepared by the method of ion exchange resin of aqueous chemistry and studied by X-Ray diffraction, thermal analyses (TGA-DTA), differential scanning calorimetry (DSC) and infrared spectrometry which show the characteristic bands of a triphosphate P_(3)O_(10)~(5-). The results of differential thermal analysis, X-Ray powder diffraction and IR spectra of the compound heated at different temperatures showed that, after dehydration, CuNa_(3)P_(3)O_(10) 12H_(2)O decomposes into an amorphous compound, then it crystallizes at 500 °C in order to give the new triphosphate CuNa_(3)P_(3)O_(10). CuNa_(3)P_(3)O_(10) crystallizes in the rhomboedric system, space group P-3_(1c), Z = 2 with the following unit-cell dimensions: a = b = 7.022(1)?, c = 9.217(1)?, M(20) = 81, F(20) = 117 (0.003419; 50) and V = 393,59(2)?~(3). CuNa_(3)P_(3)O_(10) is stable until its melting point at 560 °C. Two different methods Ozawa and KAS have been selected in studying the kinetics of thermal behavior of the triphosphate P_(3)O_(10) for the first time. The kinetic and thermodynamic characteristics of the dehydration of CuNa_(3)P_(3)O_(10) 12H_(2)O and the thermal phenomena accompanying this dehydration were determinated and discussed on the basis of the proposed crystalline structure. Quantum chemical calculations have been made for the first time for the P_(3)O_(10)~(5-) ion.