Polonium iodides

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. 

Polonium tetraiodide (8) is a black solid which sublimes in nitrogen at 200°C with partial decomposition to the metal. It is formed from the elements at 40°C/1 mm, by treating polonium dioxide or hydroxide with 0.1 N hydriodic acid, and is precipitated from solutions of polonium(lV) in dilute hydrochloric acid on the addition of 0.1 N hydriodic acid. It is also obtained as a black sublimate by heating polonium dioxide in hydrogen iodide at 200°C a black addition compound (PoCVxHI) is formed in the cold. Polonium metal does not react with iodine dissolved in carbon tetrachloride, but with iodine dissolved in benzene it does react to some extent. 

More than a decade later Muraour (Ref 11) reported that nitrogen iodide, picric acid, Pb picrate, TNT, NG, hexogen (RDX), Ag acetylide and Pb azide were subjected to the action of arrays from polonium with negative results. Details of the expts were not given... 

Ibid, Action of a-Rays of Polonium, X-rays onH Ultra-violet rays on Nitrogen Iodide and other Explosives , SocChimBullFr 53, 612—13 (1933) 12) W.E. Gamer C.H. Moon, The... 

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. 

Haissinsky and Walen [35] subjected nitrogen iodide to 5-MeV a-particles from a polonium source. The dryness of the sample and the intensity of the source decreased the time to explosion. The investigators stated that "the detonation of nitrogen iodide could be explained by a local heating of a grain of the powder." However, they thought this was an exceptional result because lead azide, silver azide, and diazo-zw-nitroaniline perchlorate did not detonate from 1 mCi of Po within 20 min. In lead azide a yellowing of the material occurred. 

Direct measurements of emerging gamma rays typically use the gamma rays from lead-210 and rely on decays occurring in lung or bone tissues. This method utilizes a system of either sodium iodide or germanium detectors placed over the body in a well-shielded room (Crawford-Brown and Michel 1987). For past exposures, the lead-210 and polonium-210 concentrations in the urine are determined by counting the number of decays on a sodium iodide system or by use of liquid scintillation. 

Table 12.5 shows evidence for the trends that we have come to expect. The highest oxidation number (+6) is stabilized by fluorine only in the cases of selenium and tellurium PoF is not known. There are no low oxidation number fluorides, apart from F—Se—Se—F and Se=SeF2, and these can only be trapped at low temperatures. Selenium forms no iodides, but the more electropositive tellurium and polonium do. 

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