Polonium vapor pressure

The vapor pressures of lead and polonium iodides have been investigated. The metals were heated in an atmosphere of iodine in a closed system. The pressure of the products was determined by a statistical method. At less than 80 atomic percent iodine, P0I4 forms in the condensed phase. At 473°K P0I4 dissociates into P0I2. Above 80 atomic percent iodine, the condensed phase exhibits the presence of Pole. The enthalpy of evaporation of Pole is 116kj mole. These experiments suggest that the separation of polonium from lead can be accomplished by their volatization in iodine vapors at elevated temperatures. 

The vapor pressures of iodides of polonium were measured in a closed system. Metalhc polonium was heated in iodine vapor and the pressures were measured. At iodine concentrations below 80 atomic percent and with increasing temperatures, polonium tetraiodide is formed in the condensed phase. The tetraiodide dissociates into P0I2 beginning at a temperature of 473 °K. The evaporation enthalpy of P0I2 is 94.4kj mole. At 80 atomic percent the condensed phase exhibits the presence of Pole. 

The separation of polonium from lead is an important procedure in radiochemistry. It was proposed,based upon studies of the vapor pressure of the iodides of lead and polonium, that polonium diiodide should serve for the pyrochemical separation of Po from Pb. 

Polonium tetrabromide is a bright red solid which melts, in bromine vapor, at about 330°C (7, 75), and boils at 360°C/200 mm 75). It is prepared by heating polonium metal in bromine vapor at 200 mm pressure for 1 hour at 250°C (7, 75) or, more rapidly, in a stream of nitrogen saturated with bromine vapor at 200°-250°C, and by heating polonium dioxide in hydrogen bromide or by evaporating a solution of polonium(IV) in hydro-... 

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