Mixed calcium and copper oxalates, with different proportions of Ca2+ and Cu2+ ions, were precipitated by dimethyl oxalate hydrolysis in homogeneous solution. The compounds were evaluated by means of scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetry (TG), and differential thermal analysis (DTA). The results suggested quantitative precipitation without solid solution formation. From the TG and DTA curves, it was possible to evaluate the Ca2+ ion proportion in the solid phase and to confirm the precipitation of the individual species.UNESP Univ Estadual Paulista, Fac Engn Guaratingueta, Dept Engn Mecan, Sao Paulo, BrazilUNESP Univ Estadual Paulista, Fac Engn Guaratingueta, Dept Fis & Quim, Sao Paulo, BrazilUNESP Univ Estadual Paulista, Fac Engn Guaratingueta, Dept Engn Mecan, Sao Paulo, BrazilUNESP Univ Estadual Paulista, Fac Engn Guaratingueta, Dept Fis & Quim, Sao Paulo, Brazil