Other Polonium Compounds

This salt is a white crystalline solid made by treating polonium (IV) hydroxide or chloride with dilute acetic acid. Its solubility in the latter increased from 0.2 mg (of Po210)/liter in 0.1 N acid to 82.5 mg/liter in 2 N acid, indicating complex ion formation. The acetato complex is colorless in solution and appears to be more stable than the hexachloro complex (11). 

Alcoholic camphoric acid reacts with alkaline suspensions of trace polonium giving a product soluble in benzene or chloroform (122). 

The solubility of polonium dioxide in 1 M citric acid is about 10.2 mg (of Po2IU)/liter (101, p. 53). 

Some trace level studies (50, 51, 81) of the extraetion of this compound from weakly alkaline solution have been reported. It appears to be soluble in chloroform (50, 51), amyl alcohol and carbon tetrachloride (81). 

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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. 

An interesting method (88) for the separation of trace amounts of polonium makes use of the volatility of some, as yet unidentified, organic compounds. Polonium complexes with diphenylearbazonc, diphenylear-bazide and diphenylthiocarbazone sublime below 100°C under atmospheric pressure and those with thiourea, 8-hydroxyquinoline, s-diphenylthiourea, thioseinicarbazide and other related compounds sublime below 160°C under the same conditions. Thus trace polonium has been separated from dilute nitric acid in the presence of diphenyl carbazide by steam distillation. 

One curious observation, however, was that pure U actually had a lower radioactivity than natural U compounds. To investigate this. Curie synthesized one of these compounds from pure reagents and found that the synthetic compound had a lower radioactivity than the identical natural example. This led her to believe that there was an impurity in the natural compound which was more radioactive than U (Curie 1898). Since she had already tested all the other elements, this impurity seemed to be a new element. In fact, it turned out to be two new elements—polonium and radium— which the Curies were successfully able to isolate from pitchblende (Curie and Curie 1898 Curie et al. 1898). For radium, the presence of a new element was confirmed by the observation of new spectral lines not attributable to any other element. This caused a considerable stir and the curious new elements, together with their discoverers, achieved rapid public fame. The Curies were duly awarded the 1903 Nobel prize in Physics for studies into radiation phenomena, along with Becquerel for his discovery of spontaneous radioactivity. Marie Curie would, in 1911, also be awarded the Nobel prize in chemistry for her part in the discovery of Ra and Po. 

Cigarette smoke contains a minute amount of polonium, along with many other carcinogenic chemicals, many of which can cause lung cancer. Over one hundred trace elements and compounds have been identified in cigarette smoke besides polonium. Some examples are nicotine, cresol, carbon monoxide, pyridine, and the carcinogenic compound benzopyrene. 

The product in this case is sodium aluminate, a compound that contains the aluminate ion, [Al(OH)4]. Because aluminum oxide reacts with both acids and bases, it is classified as amphoteric. Other main-group elements that form amphoteric oxides are shown in Fig. J.3. As you can see, these elements lie in a diagonal band across the table from beryllium to polonium. The acidic, amphoteric, or basic character of the oxides of the d-block metals depends on their oxidation state (see Chapter 16). 

Elements at the right of the p block have characteristically high electron affinities they tend to gain electrons to complete closed shells. Except for the metalloids tellurium and polonium, the members of Groups 16 and 17 are nonmetals (Fig. 1.50). They typically form molecular compounds with each other. They react with metals to form the anions in ionic compounds, and hence many of the minerals that surround us, such as limestone and granite, contain the nonmetals in their... 

The compounds of the particle phase are collectively called tar, or total particulate matter (TPM). Tar is the oily residue left behind when moisture evaporates from burned tobacco. It contains thousands of compounds, including cancer-causing aromatic amines, nitro-samines, and polycyclic aromatic hydrocarbons that are present in both smoking and smokeless tobacco. Other harmful constituents include radioactive lead and polonium as well as arsenic, among others. 

The group shows the normal property of a trend towards metallic character as it is descended. Selenium, tellurium and polonium have metallic allotropes and polonium has generally metalloid-type properties where they have been studied (Po is very rare). All the elements combine with a large number of other elements, both metallic and non-metallic, but in contrast to compounds of the halogens they are more generally insoluble in water, and even where soluble they do not ionize readily. 

After they had identified the positrons they had missed before, the Joliot-Curies had started up their cloud chamber again and looked for the new particle in other experimental arrangements. They found that if they bombarded medium-weight elements with alpha particles from polonium, the targets ejected protons. Then they noticed that lighter elements, including in particular aluminum and boron, sometimes ejected a neutron and then a positron instead of a proton. That seemed evidence for a compound proton. They presented their evidence with enthusiasm as a report to the Solvay Conference. 

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