Polonium tetrachloride

There have been many reports of the wandering of polonium from open sources, behavior at one time attributed to an aggregate recoil mechanism (84), but more recent observations with curie quantities indicate that contamination only spreads when volatile compounds, for instance polonium tetrachloride, are involved. 

Polonium tetrachloride is a bright yellow solid it melts in chlorine at about 300°C 6, 74) to a straw-colored liquid which becomes scarlet at 350°C, possibly through decomposition to the dichloride. It boils at 390°C to give a purple-brown vapor which becomes blue-green above 500°C 6). The reason for this reversible color change is unknown. 

Complexes with organic compounds have been reported. Solubility studies with tributyl phosphate (TBP) indicate the formation of a complex PoC14-2TBP (IS). Weighable amounts of polonium tetrachloride in dilute hydrochloric acid can be titrated to a colorless end point with ethylene-diamine tetra-acetic acid (EDTA) the results suggest a complex with two molecules of EDTA, but solubility studies favor a 1 1 complex. The EDTA complex is soluble in alkali and is more stable in alkaline than in acid media, but the ligand is rapidly destroyed by the radiation and solvent radiolysis products 12). However, EDTA can apparently be used to complex trace polonium in the separation of radium D-E-F mixtures (129). 

Metallic polonium is not affected by 15% bromic acid, even at 70°C, and polonium dioxide or polonium(IV) hydroxide are only slightly soluble (2.5 mg Po02/liter) in 10% bromic acid. Polonium tetrachloride is converted to a white solid of unknown composition by 15% bromic acid this could be a basic chloride (12). 

This is a white, gelatinous solid of composition close to 2Po02-H3P04, made by the action of 1 M diammouium phosphate on solid polonium tetrachloride or of 2 M phosphoric acid on polonium hydroxide. It appears... 

Polonium tetrachloride is very soluble in 2 N tartaric acid, giving a colorless solution which slowly darkens owing to radiation decomposition. Electrolysis leads to deposition of about 12% of the polonium on the cathode and 65% on the anode (11). 

Although tellurium tetrachloride has been reported to form a 1 2 complex with acetamide, there appears to be little other information available on the complex. Similarly, the reported tributyl phosphate complex of polonium tetrachloride has received little attention. The formation of a polonium(IV) perchlorate complex with tributyl phosphate has been suggested in the solvent extraction of polonium from perchloric acid. 

Platinum Dichloride Platinum Dioxide Platinum Hexafluoride Platinum Monoxide Platinum Tetrachloride Plutonium Polonium Potassium Potassium Acetate Potassium Bicarbonate Potassium Bisulfide Potassium Borohydride Potassium Bromate Potassium Bromide Potassium Carbonate... 

A white solid, possibly polonium tetrafluoride, is obtained by treating polonium hydroxide or tetrachloride with dilute aqueous hydrofluoric acid treatment of this solid, in suspension in dilute hydrofluoric acid, with sulfur dioxide yields a bluish grey product (possibly PoF2) which rapidly reverts to the original white solid on standing, presumably owing to radio-lytic oxidation 12). The solubility of polonium(IV) in aqueous hydrofluoric acid increases rapidly with acid concentration, indicating complex ion formation (/ft), p. 48). 

The compound is produced by evaporating hydrochloric acid solutions of polonium (IV) 6, 26, 74), by heating the dioxide in carbon tetrachloride vapor 74), in hydrogen chloride, thionyl chloride or with phosphorus pentachloride 6) and by heating the metal in dry chlorine at 200°C (6, 25, 74). It is hygroscopic and hydrolyzes in moist air to a white solid, possibly a basic chloride (7)). The tetrachloride is soluble in thionyl chloride and in water with hydrolysis, and is moderately soluble in ethanol, acetone, and... 

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. 

Polonium dichloride reacts with bromine vapor at, room temperature to give salmon pink PoCUBra. Neither polonium dichloride nor the dibromide reacts with iodine vapor on heating, but both may form unstable interhalogen compounds on treatment with iodine in carbon tetrachloride (7, 8). 

Aqueous 1 M chromium trioxide (12) does not react with metallic polonium, but with polonium(IV) hydroxide or tetrachloride yields an orange-yellow solid, thought to be Po(Cr04)2. This is insoluble in an excess of the reagent and is easily hydrolyzed by water or wet acetone to a dark brown basic chromate with a composition close to 2Po02 Cr()3 (cf., the basic sulfate and selenate). On long standing in an excess of aqueous chromium trioxide, oxidation to polonium(VI) may occur (Section VI,A). 

Polonium tetranitrate, with at least one molecule of dinitrogen tetroxide of crystallization, is formed as a white crystalline solid by the action of liquid dinitrogen tetroxide on polonium dioxide or tetrachloride polonium metal does not react with this reagent or with its solution in ethyl acetate. The dinitrogen tetroxide is rapidly lost on standing and the resulting tetranitrate decomposes to the basic salt (1) in l i 2 hr. under vacuum (16). 

The tetrachloride of polonium is prepared by dissolving the metal in hydrochloric acid and evaporating to dryness. P0CI4, is a hydroscopic yellow solid which melts at 300° and is soluble in ethanol and acetone. The tetrachloride can be converted to dichloride, P0CI2, by reduction with sulfur... 

The tetrabromide of polonium has been prepared in several ways, which parallel those described for the tetrachloride. These include the direct reaction between the elements at 200 °C, dissolution of the metal in aqueous hydrobromic acid solution followed by evaporation, and by the reaction between gaseous HBr and P0O2. Its existence has been coirfirmed by chemical analysis. 

The salts 2Po02-X03 (X=S, Se) have been reported to form when the tetrachloride or hydroxide of polonium is treated with more dilute acid (0.02-0.25 N). The basic sulfate is yellow in color, while the selenate is white. 

One method of preparation of Ar2PoCl2 is described in which At2Po is chlorinated by SO2CI2 in carbon tetrachloride. The diaryl dihalide is precipitated out of the chloroform solution by the addition of petroleum ether. In this manner, the preparation of Ar2PoCl2 has been reported in which Ar is jo-anisyl, mesityl, and a-naphthyl. The bis(o -naphthyl)polonium dichloride can be recrystallized from jo-xylene. 

The tetrachloride is the best known and best characterized of the binary polonium halides. It has been prepared in a... 

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