The syntheses of high purity GeI2 and GeI4 from the elements are described. The vapour pressure over solid germanium (11) iodide has been measured by the static method with a membrane-gauge manometer from T = 550 K to T = 650 K and the molar enthalpy and entropy of sublimation calculated by second-law and third-law methods. Enthalpy differences for solid and liquid GeI2 were measured in the temperature interval (330 to 770) K by drop calorimetry. The temperature, enthalpy and entropy of melting of germanium (11) iodide were determined. The values of the standard molar thermodynamic properties for solid and liquid GeI2 are presented from T = 298.15 K to T = 781 K. We have used the maximum likelihood method in the treatment of the data obtained together with previous reported values. On the basis of this work we recommend a set of standard enthalpies of formation and absolute entropies for the Ge-I compounds. (C) 2003 Elsevier Ltd. All rights reserved.