The thermal behaviour of Ba[Cu(C2O4)2(H2O)]·5H2O in N2 and in O2 has been examined using thermogravimetry (TG) and differential scanning calorimetry (DSC). The dehydration starts at relatively
low temperatures (about 80°C), but continues until the onset of the decomposition (about 280°C). The decomposition takes place
in two major stages (onsets 280 and 390°C). The mass of the intermediate after the first stage corresponded to the formation
of barium oxalate and copper metal and, after the second stage, to the formation of barium carbonate and copper metal. The
enthalpy for the dehydration was found to be 311±30 kJ mol−1 (or 52±5 kJ (mol of H2O)−1). The overall enthalpy change for the decomposition of Ba[Cu(C2O4)2] in N2 was estimated from the combined area of the peaks of the DSC curve as −347 kJ mol−1. The kinetics of the thermal dehydration and decomposition were studied using isothermal TG. The dehydration was strongly
deceleratory and the α-time curves could be described by the three dimensional diffusion (D3) model. The values of the activation
energy and the pre-exponential factor for the dehydration were 125±4 kJ mol−1 and (1.38±0.08)×1015 min−1, respectively. The decomposition was complex, consisting of at least two concurrent processes. The decomposition was analysed
in terms of two overlapping deceleratory processes. One process was fast and could be described by the contracting-geometry
model withn=5. The other process was slow and could also be described by the contracting-geometry model, but withn=2.
The values ofEa andA were 206±23 kJ mol−1 and (2.2±0.5)×1019 min−1, respectively, for the fast process, and 259±37 kJ mol−1 and (6.3±1.8)×1023 min−1, respectively, for the slow process.