Polonium compounds

Metallic polonium has been prepared from polonium hydroxide and some other polonium compounds in the presence of concentrated aqueous or anhydrous liquid ammonia. Two allotropic modifications are known to exist. 

The maximum permissible body burden for ingested polonium is only 0.03 microcuries, which represents a particle weighing only 6.8 x IO-12 g. Weight for weight it is about 2.5 x lOii times as toxic as hydrocyanic acid. The maximum allowable concentration for soluble polonium compounds in air is about 2 x lO-ii microcuries/cnu. 

PoS forms as a black precipitate when H2S is added to acidic solutions of polonium compounds. Its solubility product is 5 X 10-2 The... 

Reactions used for the preparation of polonium compounds are straightforward, but the experimental techniques are strictly determined by the small amount of the commonly used polonium-210 which is available and by the exceptionally high specific activity of the isotope (4.5 curics/mg, i.e., 1013 disintegrations/min/mg). Apart from the major effects of the alpha bombardment to be described, the separation of polonium-210 from its lead daughter, which grows in at a rate of 0.5%/day, constitutes a major chemical problem. It calls for rapid and efficient methods of purifying the polonium stock before each experiment the best of these is the sulfide process described in Section III. 

The alpha radiation chemical effects at the curie level are severe, leading to the self-decomposition of most polonium compounds thus solid polonium salts of organic acids char rapidly and polonium iodate evolves free iodine. 

It has been shown 37) that the alpha radiation displaces every atom in the lattice of a simple crystalline compound, such as polonium tetrabromide, at least once a day. It is therefore not surprising that X-ray powder photographs of polonium compounds are generally poor. 

In the past 15 years a large number of polonium compounds have been prepared in visible quantities for the first time and as a result of these investigations it has been shown that polonium behaves chemically very much as would be expected from its position in the Periodic Table, with the inert-pair effect, likely to be more marked in polonium than in tellurium, still little in evidence. 

Finally, in the P-decay of solid pentaphenylbismuthorane tagged with 210Bi various phenyl polonium compounds have been detected 187). 

A considerable body of published information dealing with the formation of organometallic polonium compounds has evolved from studies of the /3-decay products of Bi organometallics. 

The volatilities of 13 polonium compounds that are soluble in organic solvents was investigated. All of the compounds were found to volatilize below 200 °C at atmospheric pressure. Polonium was found to form soluble organic compounds with the following chelating agents 2, 3-butanediol 4, 4, 4-trifluoro-l-(2-thiene) 8-quinoline diethyldithiocarbamate thiocarbanilide 1, 5-diphenylcarbohydrazide l-phenyl-3-thiosemicarbazide thiosemicarbazide and thiourea. 

The P-decay of p-phenethyl derivative of trivalent Bi, (p-EtOCgH4)3 Bi(RaE), yielded two new polonium compounds , (p-EtOCgHJj °PoX in 72% yield and (p-EtOCgH lj °Po (28% yield). The first is the stabilization form of the primary molecular... 

The displacement of atoms just discussed is due to causes outside the affected crystal. But in the early days of radioactivity the destruction of radium salts by self-irradiation was recognised. Indeed the process occurs more or less in all minerals and compounds containing radioactive atoms. Recently D Eye (1957) calculated that 2 x 10 atoms in 1 mg of a polonium compound are knocked off their sites, mainly by recoil nuclei, in a day. As there are only about 10 atoms in this weight of the compound, every atom suffered, on the average, one displacement a day. By X-ray powder photography, with the special precautions necessitated by the polonium activity... 

The crystal structures of several polonium compounds have been determined. Both forms of PoOg have ionic lattices ZnPo has a zinc blende, and PbPo a rock-salt structure. In PoBr4, the Po is octahedrally co-ordinated with Br. 

There are no compounds of polonium of practical interest. Some polonium compounds are prepared for the purpose of research. 

Chalcogens - The Group VIA elements (oxygen, sulfur, selenium, tellurium, and polonium). Compounds of these elements are called chalcogenides. [7]... 

For almost half a century scientists had to be satisfied to work only with polonium compounds (usually in rather small amounts). The pure metal was prepared only in 1946. High-density layers of metallic polonium prepared by vacuum sublimation have a silvery colour. Polonium is a pliable low-melting metal (melting point 254°C, boiling point 962°C), its density is about 9.3 g/cm . When polonium is heated in the air it readily forms a stable oxide its basic and acidic properties are weakly manifested. Polonium hydride is unstable. Polonium forms organometallic compounds and alloys with many metals (Pb, Hg, Ca, Zn, Na, Pt, Ag, Ni, Be). When we compare Mendeleev s predictions with these properties we see how close they are to the truth. 

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