This paper describes experiments to determine the crystal structure of a new oxide of calcium and palladium, CaPd3O4. This compound was obtained during the course of efforts to prepare alkaline earth palladates. In this process excess CaCO3 was heated with PdO in air to about 800° to 900°C. At intervals the reaction mixture was removed from the furnace, thoroughly remixed and then reheated. After several cycles, the reaction products were txamined by x-ray powder diffraction methods and were found to contain CaO, CaCO3, small amounts of Pd and PdO plus one or more unidentified phases. The CaO and CaCO3 were readily removed by washing with aqueous NH4CI solution. Small amounts of Pd and PdO remaining in the mixture were removed by boiling with aqua regia, which appeared to have no significant effect on the unknown phase or phases.
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