The thermal degradation of calcium oxalate monohydrate is studied by using diffuse reflectance Fourier transform infrared spectroscopy combined with quadrupole mass spectrometry (DRIFTS/MS). DRIFTS/MS results are correlated with thermogravimetric analyses to verify the thermal properties of samples studied. Infrared spectral evidence for CaC<sub>2</sub>O<sub>4</sub>·H<sub>2</sub>O dehydration and infrared spectra for three different CaC<sub>2</sub>O<sub>4</sub> phases are given. In addition, the significance of a band at 1085 cm<sup>−1</sup> assigned to CO<sub>2</sub><sup>2-</sup> which appears during the decomposition of CaC<sub>2</sub>O<sub>4</sub> to CaCO<sub>3</sub> is discussed.
Robert L. White and Jiu Ai, "Variable-Temperature Diffuse Reflectance Infrared Studies of Calcium Oxalate Monohydrate," Appl. Spectrosc. 46, 93-99 (1992)