Polonium plating

Dissolve the Fe(OH)3 precipitate in the minimum amount of 2mol/L HCl. It may be necessary to add a few (one or two) mL of 9mol/L HQ. Then transfer quantitatively into 100 mL Teflon beaker and dilute with distilled water to approximately 40 mL. The solution 

Heat in a sand bath on magnetic stirrer-heater at 85-95 °C (stirring balls are convenient). Add ascorbic acid powder until the yellow colour (Fe) disappears. 

Note The amount required depends on the amount of Fe used. It takes a considerable amount to bind 250 mg of Fe. In order to prevent adding too much, wait after each addition, since the dissolution and complexation is slow. 

Remove the protective cover from the hollow side of the silver disc, clean the disc with ethanol and put it on the bottom of the beaker. 

Note If a disc is punched out of a sheet of silver, the borders remain a little curved. When dropped into the sample, the disc will fall hollow side up on the bottom of the beaker. 

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This has been made in trace quantities by the action of dilute hydrochloric acid on magnesium plated with polonium. As expected, it is extremely unstable and decomposes even at 100 K,... 

In 1896, the French scientist Fienri Becquerel happened to store a sample of uranium oxide in a drawer that contained some photographic plates (Fig. 17.2). He was astonished to find that the uranium compound darkened the plates even though they were covered with an opaque material. Becquerel realized that the uranium compound must give off some kind of radiation. Marie Sklodowska Curie (Fig. 17.3), a young Polish doctoral student, showed that the radiation, which she called radioactivity, was emitted by uranium regardless of the compound in which it was found. She concluded that the source must be the uranium atoms themselves. Together with her husband, Pierre, she went on to show that thorium, radium, and polonium are also radioactive. 

Lind (1961) defines radiation chemistry as the science of the chemical effects brought about by the absorption of ionizing radiation in matter. It can be said that in 1895, along with X-rays, Roentgen also discovered the chemical action of ionizing radiation. He drew attention to the similarity of the chemical effects induced by visible light and X-rays on the silver salt of the photographic plate. This was quickly followed by the discovery of radioactivity of uranium by Becquerel in 1896. In 1898, the Curies discovered two more radioactive elements—polonium and radium. 

Tsunogai and Nozaki [6] analysed Pacific Oceans surface water by consecutive coprecipitations of polonium with calcium carbonate and bismuth oxychloride after addition of lead and bismuth carriers to acidified seawater samples. After concentration, polonium was spontaneously deposited onto silver planchets. Quantitative recoveries of polonium were assumed at the extraction steps and plating step. Shannon et al. [7], who analysed surface water from the Atlantic Ocean near the tip of South Africa, extracted polonium from acidified samples as the ammonium pyrrolidine dithiocarbamate complex into methyl isobutyl ketone. They also autoplated polonium onto silver counting disks. An average efficiency of 92% was assigned to their procedure after calibration with 210Po-210Pb tracer experiments. 

Cowen et al. [5] showed that polonium can be electrodeposited onto carbon rods directly from acidified seawater, stripped from the rods and auto-plated onto silver counting disks with an overall recovery of tracer of 85 4% for an electrodeposition time of 16 h [ 13]. 

Polonium can be recovered from natural pitchblende. The yield, however, is exceedingly small as 1 g of polonium is contained in about 25,000 tons of pitchblende. The element may be isolated from the pitchblende extract by deposition on a bismuth plate immersed in chloride solution. 

The most spectacular radiation effect is the glow emitted by polonium and its compounds arising from excitation of the surrounding gas (see ref. 3, plate 4 ref. 4, frontispiece) a marked fluorescence is also induced in the... 

There have been some unsuccessful attempts to prepare a volatile hexafluoride from fluorine and polonium-210 26, 104), but recently such a fluoride has been prepared in this way from polonium-208 plated on platinum 132). The product appears to be stable while in the vapor phase, but on cooling a nonvolatile compound is formed, probably polonium tetrafluoride resulting from radiation decomposition of the hexafluoride. Analytical data are not recorded for any polonium fluoride, largely owing to the difficulty of determining fluoride ion accurately at the microgram level. 

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. 

Radioactivity was discovered in 1896 in Paris by Henri Becquerel, who investigated the radiation emitted by uranium minerals. He found that photographic plates were blackened in the absence of light, if they were in contact with the minerals. Two years later (1898) similar properties were discovered for thorium by Marie Curie in France and by G. C. Schmidt in Germany. That radioactivity had not been discovered earher is due to fact that human beings, like animals, do not have sense organs for radioactive radiation. Marie Curie found differences in the radioactivity of uranium and uranium minerals and concluded that the minerals must contain still other radioactive elements. Together with her husband, Pierre Curie, she discovered polonium in 1898, and radium later in the same year. 

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%. 

Radioactivity is emitted from atomic nuclei that are unstable and spontaneously change their structure. In 1896, Henri Becquerel first discovered radioactivity when he placed a piece of zinc uranyl sulfate wrapped in paper on a photographic plate. Two years later, Marie and Pierre Curie discovered two highly radioactive elements, polonium and radium, in pitchblende. a particles, the nuclei of helium atoms, were among the radiations emitted by these substances which were spontaneously transmuting. Indeed, since the earth had billions of years ago lost its original complement of light, inert helium, all helium in our... 

X-rays fascinated the scientific community and the general public alike. Scientists investigated further and soon found related phenomena. Chief among these was a discovery made by Antoine-Henri Becquerel, a professor of physics in Paris. While studying the characteristics of fluorescent materials in March 1896, he discovered that uranium exposed a photographic plate when placed next to it. He had found another form of radiation, one that was emitted spontaneously from a natural substance. To investigate further, Becquerel collaborated with a husband-and-wife scientific team, Pierre Curie and Maria Sklodowska-Curie. Sklodowska-Curie devised an electrometer that could measure this radioactivity, as she called it, and studied a number of materials. In 1898 the trio managed to separate from uranium ore two radioactive elements polonium and radium. 

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