Bismuth and Polonium

Bismuth and polonium are the only elements in their respective chemical series that form cations. The lighter elements in both groups only form anions. Bismuth has trivalent and pentavalent oxidation states, but the latter is relatively unstable with respect to formation of the oxide. Polonium exhibits a range of oxidation states (Brown, 2001), with the divalent and tetravalent states forming the cations Po and PoO in aqueous solution. Shannon (1976) reported that the ionic radius of BP is 1.03 A. 

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 

Hydrolysis of Metal Ions, First Edition. Paul L. Brown and Christian Ekberg. 

The solubility of bismuth oxide (bismite) is described by reaction (2.13) (M = BP , x= 1.5). Laptev and Kolonin (1982) studied the solubility of bismite and determined the solubility constant and third monomeric stability constant 0/ across the temperature range of 25-300°C. From these data, and the protolysis constants of water listed in Chapter 5, the solubility constant relevant to 

The relationship between the solubility constants and temperature is described by the equation 

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However, in regard to the reactions of tungsten with metallic elements, the situation is quite different. A large number of metals exist which fail to react with tungsten, like the alkali metals, the alkaline earth metals with the exception of beryllium, the rare earth metals with the exception of cerium, and especially the elements scandium, yttrium, lanfiianiun, copper, silver, gold, zinc, cadmium, mercury, indium, thallium, tin, lead, antimony, bismuth, and polonium. 

It should be noted that in groups IVA, VA, and VIA, the elements at the top are nonmetals (carbon, nitrogen, and oxygen) and those at the bottom are metals (lead, bismuth, and polonium). The stairstep cuts these groups in two, separating metals from nonmetals with metalloids in the middle. 

Thorium, bismuth and polonium can be quantitatively separated from lead.(and radium) by extraction from a saturated aluminum nitrate solution with-mesityl oxide (M3)i Thallium can be separated by extraction of thallium III into a solution of 5% n-octanol In hexone from 0.15 M hydrochloric acid (L2). 

It Is possible In some cases to change the order of elution as shown for lead and Iron-III in curves A and B of Figure 27- Lead, bismuth and polonium have been separated from radium solutions by Dowex-1 anion-exchange columns (h6)(HIO)(P3) by putting the mixture onto the resin In 1-2 M hydrochloric acid. The radium passed. 

Separation of bismuth and polonium from lead can also be achieved by Immersing a hydrogen soaked platinum electrode In a 0.1 M hydrochloric acid solution of the tracer lead, bismuth and polonium (E6). Nitric acid, bromine or other substances which might poison the platinum electrode for adsorption, of hydrogen must be absent. This has been used for separation of RaD from RaE and RaF (E6)(H5)- This method does not introduce nickel or silver contamination Into the RaD solution or In the RaE or RaP when these are dissolved from the electrode. 

Soils contain varying amounts of uranium-238, which decays in several steps to radium-226, then to radon-222, a gas (see Figure 21.4). Some homes situated in areas of high uranium content have been found to accumulate radon gas. Radon has a half-life of 3.8 days, decaying by alpha emission to radioactive lead, bismuth,and polonium.These decay products can remain in the lungs and may lead to lung cancer. 

Radon-222 [14859-67-7] Rn, is a naturally occuriing, iaert, radioactive gas formed from the decay of radium-226 [13982-63-3] Ra. Because Ra is a ubiquitous, water-soluble component of the earth s cmst, its daughter product, Rn, is found everywhere. A major health concern is radon s radioactive decay products. Radon has a half-life of 4 days, decayiag to polonium-218 [15422-74-9] Po, with the emission of an a particle. It is Po, an a-emitter having a half-life of 3 min, and polonium-214 [15735-67-8] Po, an a-emitter having a half-life of 1.6 x lO " s, that are of most concern. Polonium-218 decays to lead-214 [15067-28A] a p-emitter haviag = 27 min, which decays to bismuth-214 [14733-03-0], a p-emitter haviag... 

Poet, S. E., Moore, H. E., and Martell, E. A., Lead-210, Bismuth-210, and polonium-210 in the atmosphere accurate radio measurement and application to aerosol residence time determination, J. Geophys. Res., 77, 6515-6527 (1972). 

After neutron irradiation bismuth (canned in aluminum jackets) is dissolved in a mixture of hydrochloric and nitric acids and excess NO3 is removed by adding a reducing agent, such as, urea or formic acid. If bismuth is used as an anode, the reducing agent is dissolved in HCl. Various methods are applied for concentration of polonium in the acid mixture and its subsequent separation from bismuth. Such processes include spontaneous deposition of polonium over a less electropositive metal and coprecipitation with tellurium. In the latter method, a Te + or Te + salt is added to the extract, followed by addition of stannous chloride, which reduces both the tellurium and polonium to their metallic state, coprecipitating them from bismuth in the extract mixture. 

Sir Alexander Fleck, 1889—. Author of many research papers on the radioactive isotopes. He proved the inseparability of uranium Xi and radioaetinium from thorium, of thorium B and actinium B from lead, of mesothorium 2 from actinium, of radium E from bismuth, and of radium A from polonium, and confirmed the discovery of uranium X3 by Faj ans and O. H. Gohring. Chairman of Imperial Chemical Industries, Ltd. See also ref. (1S7). 

Much of the early literature of polonium describes methods for separating it from these mixtures many of these have subsequently been adapted to the separation of milligram amounts of polonium from irradiated bismuth and to its purification. The methods range from a simple chemical separation of the element with a tellurium carrier to its electrodeposition on to a more noble metal or its spontaneous electrochemical replacement on the surface of a less noble metal. 

The deposition of polonium on to copper does not give a good separation of the element from bismuth (83, 111), but bismuth powder itself provides a quite successful process (25). In practice, the irradiated bismuth is dissolved in a mixture of hydrochloric and nitric acids, and after elimination of the latter, the solution is stirred with a few grams of powdered bismuth the polonium is deposited completely on to the bismuth. The product is dissolved in acid and the whole process repeated with decreasing amounts of metallic bismuth, until the proportion of polonium to bismuth is high enough for the former to be precipitated as the metal with stannous chloride. 

The poor metals among the BCNOs usually include aluminum, gallium, indium, thallium, tin, lead, and bismuth. The metalloids are boron, silicon, germanium, arsenic, antimony, tellurium, and polonium. The nonmetals are carbon, nitrogen, oxygen, phosphorus, sulfur and selenium. These groups are not official, and chemists sometimes disagree on whether a particular element like boron should be called a metal or a metalloid. 

The gases radon (222Rn) and thoron (220Rn) are formed as progeny of uranium and thorium in rocks and soil. They are emitted from the ground into the atmosphere, where they decay and form daughter products, isotopes of polonium, bismuth and lead, which either remain airborne till they decay, or are deposited in rain and by diffusion to the ground. 

The two heaviest members of Group 6A can lose electrons to form cations. Although they do not lose all six valence electrons because of the high energies that would be required, tellurium and polonium appear to exhibit some chemistry involving their 4+ cations. However, the chemistry of these Group 6A cations is much more limited than that of the Group 5A elements bismuth and antimony. 

Moore, H.E., Poet, S.E. and Martell, E.A., Size distribution and origin of lead-210, bismuth-210 and polonium-210 on airborne particles in the troposphere. In T.F. Gesell and W.M. Lowder (Eds.), Natural Radiation Environment III. Technical Information Center, U.S. Dept, of Energy, Springfield, Virginia, pp. 415-429 (1980) Pierson, D.H., Cambray, R.S. and Spicer, G.S., Lead-210 and polonium-210 in the atmosphere, Tellus, 18 (1966) 427-433. 

Polonium, with chemical resemblance to bismuth and tellurium, is often considered as a metal. 

Bones are actually living protein networks to which minerals attach themselves. Not aU of the minerals deposited on bones are essential to bone building. There are at least two dozen elements in bones that have no known function in the human body, as well as a handful of nonessential elements, such as boron, strontium, silicon, barium, bismuth, and arsenic (yes, arsenic), that are believed to do some good. Five toxic elements—lead, cadmium, mercury, polonium, and radium—are often found in human bones. As long as they are stabilized in the bones, they do no apparent harm. 

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