Dissociation of polonium iodides and vapour pressure in polonium-iodine system

A method of vapor pressure determination based on the remote control of the amount of a radioactive element in a known volume according to its natural radioactivity at the dynamic equilibrium inside the enclosed evacuated ampule has led to the conclusion that the system polonium-iodine at an iodine content of up to 23 at.% produces no effect of iodine on the polonium vapor pressure. In the interval 50 to 80 at.% iodine, on heating the system, polonium tetraiodine dissociates into polonium diiodine and iodine. The temperature dependence of the polonium diiodide vapor pressure is expressed by the equation Isub(g)Psub(torr) = (8.59+-0.71) -(4905+-362)/T at 200 to 315 deg C. Vaporization heat enthalpy is equal to 22.4 kcal/mole. In the interval 81 to 100 at% iodine the polonium-iodine system is of a heterogeneous nature and is composed of polonium tetraiodide and iodine. At an iodine pressure of 30 to 70 torr polonium hexaiodide makes its appearance in the condensed phase, which dissociates to yield polonium tetraiodide