Radium preparation

The first product of disintegration is mesothorium I, discovered by Hahn in 1907. It is isotopic with radium and is used as a substitute for certain radium preparations. As large quantities of thorium minerals are now worked up in connection with the gas-mantle industry, and mesothorium is a by-product, it has assumed commercial importance. It is separated from thorium in monazite being precipitated along with barium as sulphate. Thorium Xy discovered by Rutherford and Soddy in 1902, is another isotope of radium. Radiothorium, RdTh, is an active isotope of thorium and cannot be separated from it directly it has to be obtained from mesothorium I by disintegration if required free from isotopes. 

At the same time, and using exactly the same method of working, distilled water is to be mixed with a radium preparation and all the above-mentioned... 

In June 1898 a radioactive element in the bismuth precipitate was characterised and named polonium from the native country of one of us (Poland). In December 1898 a new element, named radium in the barium precipitate was announced. The still impure radium preparation had an activity a million times that of uranium. E. Demar9ay showed that radium had a characteristic spark spectrum. ... 

Curies and who called it actinium, and by Giesel/ who called it emanium. Giesel obtained a radium preparation nearly free from barium by recrystallising the bromide only six or eight times. He found that it gave a carmine-red flame coloration. ... 

Gr. aktis, aktinos, beam or ray). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Actinium-227, a decay product of uranium-235, is a beta emitter with a 21.6-year half-life. Its principal decay products are thorium-227 (18.5-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300-degrees G. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.6-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons. 

Ra.don Sepa.ra.tion, Owing to its short half-life, radon is normally prepared close to the point of use in laboratory-scale apparatus. Radium salts are dissolved in water and the evolved gases periodically collected. The gas that contains radon, hydrogen, and oxygen is cooled to condense the radon, and the gaseous hydrogen and oxygen are pumped away. 

Barium [7440-39-3] Ba, is a member of Group 2 (IIA) of the periodic table where it Hes between strontium and radium. Along with calcium and strontium, barium is classed as an alkaline earth metal, and is the densest of the three. Barium metal does not occur free in nature however, its compounds occur in small but widely distributed amounts in the earth s cmst, especially in igneous rocks, sandstone, and shale. The principal barium minerals are barytes [13462-86-7] (barium sulfate) and witherite [14941-39-0] (barium carbonate) which is also known as heavy spar. The latter mineral can be readily decomposed via calcination to form barium oxide [1304-28-5] BaO, which is the ore used commercially for the preparation of barium metal. 

Figure 2. Alpha spectrum for a radium adsorbing manganese-oxide thin film exposed to a groundwater sample, after Surbeck (2000) and Eikenberg et al. (2001b). A 2x2 cm sheet is exposed to O.l-l.O L of sample for 2 days, capturing nearly all of the radium in the sample. These sample discs can be used directly for low-level alpha spectrometry without the need for further separation and preparation methods to produce planar sample sources. Energy resolution is nearly as good as for electroplated sources, and detection limits are typically 0.2 mBqA (6 fg Ra/L) for Ra and " Ra for a one-week counting period. These sensitivities are comparable to traditional methods of alpha spectrometry. [Used by permission of Elsevier Science, from Eikenberg et al. (2001), J Environ Radioact, Vol. 54, Fig. 4, p. 117]...

Preparation. The element was isolated in 1911 by Mme. Curie and A. Debieme by the electrolysis of a solution of pure radium chloride, employing a mercury cathode. By distillation in hydrogen atmosphere this amalgam yielded the pure metal. Radium is currently prepared by reduction of the oxide by Al at 1200°C in vacuum. 

Uses. The main use of radium is the preparation of 227Ac, via neutron capture in a nuclear reactor. 

Here, then, for the first time in the history of Chemistry, we have the undoubted formation of one chemical element from another, for, leaving out of the question the nature of the emanation, there can be no doubt that radium is a chemical element. This is a point which must be insisted upon, for it has been suggested that radium may be a compound of helium with some unknown element or, perhaps, a compound ofhdium with lead, since it has been shown that lead is probably one of the end products of the decomposition of radium. The following considerations, however, show this view to be altogether untenable (i.) All attempts to prepare compounds of helium with other... 

Actinium-227 occurs in uranium ore and is a decay product of uranium-235. It is found in equilibrium with its decay products. It is prepared hy homhard-ing radium atoms with neutrons. Chemically, the metal is produced hy reducing actinium fluoride with lithium vapor at 1,100°C to 1,300°C. 

The second member of the series is radium itself. The task of isolating it was most difficult, and involved risk of losing the precious product. In 1910, however, Mme. Curie and M. Andre Debieme finally succeeded in preparing the shining white metal but, since they needed the radium in their researches, they did not keep it in this form. 

To remove radium and other radioactive constituents from pitchblende, Hahn and Meitner treated pulverized pitchblende repeatedly and for long periods of time with hot concentrated nitric acid. From the insoluble siliceous residue they separated a new radioactive substance, which they called protoactinium. This name has subsequently been shortened to protactinium. When they added a little tantalum salt to a solution containing protactinium, the reactions of the new substance so closely resembled those of tantalum that Hahn and Meitner were unable to separate the two substances (118). Since tantalum is not radioactive, the protactinium could thus be obtained free from other radioelements. Since protactinium is not an isotope of tantalum, it should be possible to separate them from each other (119). By working up large quantities of rich pitchblende residues from the Quinine Works at Braunschweig, Hahn and Meitner were able to extract more active preparations of the new element (49). 

Mme. Curie and her daughter, Mme. Joliot-Curie. The latter published many papers on the radioactive elements. During World War I, while still very young, she assisted her mother in the radiological service to the wounded. With her husband, Dr. F. Joliot of the Institut de Radium in Paris, she prepared artificial radioactive elements. 

The actual discovery was made by Mile. Marguerite Perey at the Curie Institute in Paris. In 1939 she purified an actinium preparation by removing all the known decay products of this element. In her preparation she observed a rapid rise in beta activity which could not be due to any known substance. She was able to show that, while most of the actinium formed radioactinium, an isotope of thorium, by beta emission, 1.2 0.1 per cent of the disintegration of actinium occurred by alpha emission and gave rise to a new element, which she provisionally called actinium K, symbol AcK (35, 36). This decayed rapidly by beta emission to produce AcX, an isotope of radium, which was also formed by alpha emission from radioactinium. Thus AcK, with its short half-life, had been missed previously because its disintegration gave the same product as that from the more plentiful radioactinium. 

Feb. 2, 1907 Feb. 20,1907 1907 1907 1909 1910 1910 1911 May 28, 1912 1913 Death of Mendeleev. Death of Moissan. Urbain discovers lutetium. Von Bolton prepares a columbium (niobium) regulus. E. Weintraub prepares pure fused boron. Mme. Curie and M. Debierne isolate radium metal. M. A. Hunter prepares titanium 99.9 per cent pure. Antonoff discovers uranium Y. Death of Boisbaudran. Fajans and Gohring discover uranium X2 (element 91, eka-tantalum). 

---