Polonium II

Polonium is known to form a number of oxidation states including Po . Brown (2001) showed that the stability region ( j,-pH) of polonium(II) was quite narrow, occurring in a region that does not exceed a pH of 6 and is bounded by polonium metal at lower and polonium(IV) at higher E. The hydrolytic properties of polonium(II) are expected to be similar to those of lead(II). As a consequence, polonium(II) is not expected to hydrolyse until a pH higher than 6, in a region where it is not expected to be stable. It is not expected, therefore, that polonium(II) hydrolysis species would exist and none have been reported. 

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Bipositive polonium in hydrochloric acid solution (pink) is oxidized to polonium(lV) by hydrogen peroxide, by hypochlorous acid or by the radiolysis products of the alpha bombardment of the solvent. Solutions of polonium(II) in acid are obtained by the reduction of polonium(lV) with sulfur dioxide or hydrazine in the cold, or with arsenious oxide on warming. Polonium (IV) is not reduced in hydrochloric acid by either hydroxylamine or oxalic acid, even on boiling 6). 

Suspensions of the disulfate in N-2 N sulfuric acid dissolve on boiling with hydroxylamine to give a pink solution, characteristic of polonium(II), but the disulfate hydrate is reprecipitated on cooling, even in the presence of an excess of hydroxylamine (10), in accord with earlier trace level... 

Polonium (ii) The radioisotopes of polonium (usually Po) have been difficult to analyze with accuracy using the conventional methods. The procedure outlined here is, however, simple, rapid, and accurate. With the sample in solution, add 3 to 5 mL of concentrated phosphoric acid and evaporate to remove other acids. Transfer this phosphoric acid solution to a small equilibration vessel using 3 to 5 mL of water. Add 1 mL of 0.1 M HCl. Add a measured volume, 1.2 to 1.5 mL, of a solution of TOPO, 0.1 to 0.2 M, in toluene and equilibrate. This is a highly selective separation of polonium from other radionuclides with the possible exception of the beta/gamma emitting bismuths. Quantitative stripping and transfer of the polonium to a plate is difficult but the use of an extractive scintillator and counting on a PERALS spectrometer is rapid and simple and the results are quite accurate. Because of the minimal chemical manipulations required, the accuracy of this determination can easily be better than 1%. 

No hydrolysis species have been observed for polonium(II). In aqueous solution, polonium(IV) forms the oxoanion PoO ". This latter cation has been observed to hydrolyse to form the four monomeric species, PoOOH" to PoO(OH)4 . Potentially, polonium(IV) could form polymeric species, but due to its relatively high radioactivity, conducting experiments at a concentration that... 

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. 

Under normal conditions an atom in elemental tellurium has coordination number 2 + 4. It has been known for a long time that pressure causes the interatomic distances to approximate each other until finally every tellurium atom has six equidistant neighboring atoms at 297 pm the structure (now called Te-IV) corresponds to /3-polonium. However, before this is attained, two other modifications (Te-II and Te-III) that are out of the ordinary appear at 4 GPa and 7 GPa. Te-II contains parallel, linear chains that are mutually shifted in such a way that each Te atom has, in addition to its two neighboring atoms within the chain... 

When the flow through the CNC was exhausted outside of the laboratory, we observed particle formation at higher SOp concentrations as expected (Table II). To prove that the radical scavenger effect is reproducible, another radical scavenger (92 ppb nitric oxide) was used in the presence of 110 ppb SOp concentration and 2% humidity, and the supression in particle formation was observed. Another possible mechanism that supressed the particle formation is that more neutralization of polonium ions occurred at the higher humidities and thus ion-induced nucleation would be suppressed. 

The physical properties of the metal (Table II) resemble those of thallium, lead and bismuth, its neighbors in the Periodic Table, rather than those of tellurium, its lower homologue. The low melting and boiling points are particularly noteworthy an attempted study of the Hall effect in polonium metal has also been reported (90). In chemical properties the metal is very similar to tellurium, the most striking resemblance being in its reactions with concentrated sulfuric acid (or sulfur trioxide) and with concentrated selenic acid. The products are the bright red solids, PoSOs and... 

The binuclear terbium centers and type I rotaxanes form a two-dimensional layer. Stacked layers are further interconnected via type II rotaxanes to form a three-dimensional polyrotaxane network, which has an inclined a-polonium topology with the binuclear terbium centers behaving as six-connected nodes (Fig. 20.4.10). The void space in the crystal packing is filled by a free rotaxane unit, NOJ and OH- counter ions, and water molecules. 

Another method for measuring Volta potentials is to ionize the air between the plates, and adjust the potential applied to them until no current passes across the air gap. This method appears to have been used first by Righi2 (with ultra-violet rays as a source of ionization), later by Perrin and many later workers, using radium salts 8 Greinachcr,4 and Anderson and Morrison,6 pointed out that errors frequently arose if sources capable of ionizing the air in other parts of the apparatus than directly between the plates and it is well to use either a carefully shielded source of j3 or y rays or a radioactive source such as polonium, which gives off only a rays which have a range of a few centimetres only. This method is that used for the determination of the surface potentials of insoluble films as described in Chapter II. 

The main characteristics of the elements of the chromium subdivision are dealt with in Chapter I. of Vol. VII., Part III. Those of sulphur, selenium, and tellurium are dis-cussed in Volume Vll, Part II, Polonium (Radium F) is dealt with in Vol. Ill,... 

The chemistry of polonium was recently reviewed by Bagnall (23). Regarding free radicals this review cites a calculation of the bond length of PoH (245) and some electrochemical evidence of Po(III) as an intermediate in the oxidation of Po(II) to Po(IV) in aqueous hydrochloric acid (24). 

Solutions containing the metal, most commonly in nitric acid, will deposit the metal on a platinnm electrode by electrodeposition. Polonium metal is deposited spontaneously from such solutions on to metals such as silver or nickel. The metal can be sublimed off such support metals at low pressures. Thermal decomposition of polonium sulfide also yields the metal. In much the same way as tellurium, the metal can be obtained from its solutions by the action of reducing agents such as hydrazine, tin(II) ion, titanium(III) ion, and dithionite. Such metal precipitates appear as gray-black powders. Thin foils, silvery in color, have been prepared by vacuum sublimation of the metal. 

Indications have been reported for metallic conduction in sulfur at high temperature at ultra high pressures ranging from 87 to 230 kb (9,10,11), The metallic conduction is believed to arise from a transition to a metallic structure, perhaps similar to that of polonium. However, there is some question as to whether this transition took place experimentally in the solid state (9, 12) as a result of the uncertainty in the location of the liquidus at ultra high pressures. The metallic sulfur state is characterized by a conductivity which decreases with increasing pressure and has electrical properties different from typical metals (II). 

Ions IruNltrate Media. II. Separation of Selenium-Tellurium-Polonium and Radium D- Radium E- Polonium", Notas de Plalca (Brazil) Vol. Vi No. I5 (1959) NP-8653. 

Certain predicted volatility characteristics of elements 116,117, and 118 (eka-polonium, eka-astatine, and eka-radon) or their compounds may offer advantages for chemical identification this, of course, is especially true for element 118. The chemical properties of element 116 should be determined by extrapolation from polonium, and thus it should be stable in the ii state with a less stable IV state. 

Polonium (Po) is a radioactive element that was discovered in 1898 by Marie Sklodowska-Curie and Pierre Curie. Po is used in brushes to remove dust from photographic films and to avoid charge static accumulation produced by several processes, such as the rolling of paper, wire, and sheet metal. In addition, Po has been alloyed with beryllium to be used as a neutron source. All these and other applications depend on Po s structural properties. Po is the only element of the periodic table that adopts the simple cubic (sc) structure at ambient pressure (a few other elements such as Ca-III and As-II present the sc, but only at high pressure [1]), and this structure has a low atomic packing factor and is rare in nature. The first experimental studies of Po s crystal structure, by using electron diffraction, were reported in 1936 by Rollier et al. [2]. Several years later, Beamer and Maxwell [3,4] and Sando and Lange [5] reported on their X-ray diffraction experiments on metallic Po. From these reports, we know that Po exhibits two structural phases the a phase (a-Po), which has the sc structure p Pmim)], a = 3.345(2) A [4], and the /3 phase (/3-Po), stable above 77(9)°C, which has the rhombohedral (r) structure [Df (/ 3m)], a = 3.359(1) A, and a = 98.22(5)°. 

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