Radium chloride

L. radius, ray) Radium was discovered in 1898 by Mme. Curie in the pitchblende or uraninite of North Bohemia, where it occurs. There is about 1 g of radium in 7 tons of pitchblende. The element was isolated in 1911 by Mme. Curie and Debierne by the electrolysis of a solution of pure radium chloride, employing a mercury cathode on distillation in an atmosphere of hydrogen this amalgam yielded the pure metal. 

Marie Curie (1867-1934) and Pierre Curie (1859-1906) Nobel Prize for physics 1903. Only 0.1 g of radium chloride was isolated from about 500 kg or uranium pitchblende (1 5 million). 

Radium chloride (RaCy has the same use as radium bromide. 

Uranium mineral first is digested with hot nitric acid. AH uranium and radium compounds dissolve in the acid. The solution is filtered to separate insoluble residues. The acid extract is then treated with sulfate ions to separate radium sulfate, which is co-precipitated with the sulfates of barium, strontium, calcium, and lead. The precipitate is boiled in an aqueous solution of sodium chloride or sodium hydroxide to form water-soluble salts. The solution is filtered and the residue containing radium is washed with boiling water. This residue also contains sulfates of other alkahne earth metals. The sohd sulfate mixture of radium and other alkahne earth metals is fused with sodium carbonate to convert these metals into carbonates. Treatment with hydrochloric acid converts radium and other carbonates into chlorides, all of which are water-soluble. Radium is separated from this solution as its chloride salt by fractional crystallization. Much of the barium, chemically similar to radium, is removed at this stage. Final separation is carried out by treating radium chloride with hydrobromic acid and isolating the bromide by fractional crystallization. 

At the time of the discovery of radio-activity, about seventy-five substances were called elements in other words, about seventy-five different substances were known to chemists, none of which had been separated into unlike parts, none of which had been made by the coalescence of unlike substances. Compounds of only two of these substances, uranium and thorium, are radio-active. Radio-activity is a very remarkable phenomenon. So far as we know at present, radio-activity is not a property of the substances which form almost the whole of the rocks, the waters, and the atmosphere of the earth it is not a property of the materials which constitute living organisms. It is a property of some thirty substances—of course, the number may be increased—a few of which are found widely distributed in rocks and waters, but none of which is found anywhere except in extraordinarily minute quantity. Radium is the most abundant of these substances but only a very few grains of radium chloride can be obtained from a couple of tons of pitchblende. 

While tracing down the new element, the Curies often wondered how its salts would look, and hoped that perhaps they might display beautiful colors. The radium chloride which they finally obtained proved to be a white salt, however, but it was even more beautiful than their... 

As part of her Ph.D. research (Radioactive Substances, 1903), Marie Curie measured the atomic mass of radium, a new, radioactive element that she discovered. She knew that radium is in the same family as barium, so the formula of radium chloride is RaCl2- In one experiment, 0.091 92 g of pure RaCl2 was dissolved and treated with excess AgN03 to precipitate 0.088 90 g of AgCl. How many moles of Cl were in the RaCl2 From this measurement, find the atomic mass of Ra. 

In the same year, 1896, the Curies isolated an active barium chloride fraction, containing another new element, which they named radium. They found that radium chloride could be separated from barium chloride by fractional precipitation of the aqueous solution by addition of alcohol. By 1%2 Madame Curie had prepared 0.1 g of nearly puie radium chloride, with radioactivity about three million times that of uranium. 

A radioactive method has also been developed for determination of catalyst levels in reactors, hoppers, and catalyst-feed lines of moving-bed units (331). The equipment consists of one or more radiation sources (radium chloride), a Geiger tube, and associated electronic instruments. The radium sources are mounted within the vessel at intervals over the range of levels to be measured, with the Geiger tube at the top. The exact amounts and locations of the radium sources are so proportioned that radiation from each source is no longer detected when covered by a 2-ft. layer of catalyst. Thus the counter receives maximum radiation when the vessel is empty and decreasing intensities as catalyst level rises. 

Representative Chemicaes Radium bromide and radium chloride, both soluble in water, are two of the common forms of radium with public health concerns... 

The method of treatment consisted in effecting a concentration of some of the constituents of the residues and observing the radioactivity of the various portions into which the material was divided. It was observed that if barium was concentrated the radioactivity of that portion increased rapidly. From a ton of residues there may be prepared 10-20 kilograms of crude sulfate whose activity is about 60 times that of uranium. The Curies then converted the sulfates to chlorides and subjected the material to the process of fractional crystallization. After a number of crystallizations there was obtained in the most insoluble portion a fraction, of a gram of radium chloride which was a million times as active as uranium, One ton of pitchblende is said to contain 0.37 gram of radium, 0.00004 gram of polonium,1 and a small amount of aetinium. 

Radium chloride, RaCl2 or RaCb - 2H20, forms colorless crystals when pure but when barium is present the color is yellow or pink. It is somewhat less soluble in water and hydrochloric acid than is BaCl2, with which it is isomorphous. 

Since monazite contains an appreciable amount of uranium, radium is always present and the methods of extracting mesothorium concentrate the radium also. Consequently, commercial mesothorium contains considerable radium, which is responsible for 20-25 per cent of the radioactivity produced. Since, however, the mesothorium is much more active than radium, it is estimated that commercial mesothorium is composed, weight for weight, of 99 per cent radium chloride and 1 per cent mesothorium chloride. 

Because radium was present in such a tiny amount, the Curies were at first unable to isolate pure samples, but had to settle for the chloride salt, RaCl2. Much to the Curies delight, they found that radium chloride glowed in the dark, just like phosphorus. The Curies took such joy in their discovery that they would entertain their scientific friends— among them Paul Langevin (1872-1946) and Jean-Baptiste Perrin (1870-1942)—by inviting them to the Curies apartment just to sit in the dark and watch their sample of radium chloride glow. 

Radium. The radium source used in brachytherapy uses mostly radium sulfate or radium chloride mixed with an inert filler and loaded into cells about 1 cm long and 1 mm in diameter. These cells are made of 0.1- to 0.2- mm-thick gold foil. Radium sources are manufactured as needles or tubes in a variety of lengths and activities. Leakage of radon gas from a radium source represents a significant hazard if the source is broken. The sources are, however, doubly encapsulated to prevent such an occurrence. Cesium-137 has replaced radium, at least in the US. 

In 1902 Marie Curie succeeded in isolating one-tenth of a gram (0.0035 ounces) of pure radium chloride from eight tons of pitchblende residue, a task that required an enormous amoxmt of physical labor. The atomic weight of radium she determined to be 225. These results aroused immediate interest. She received her doctoral degree in 1903, her radioactivity investigations forming the major part of her thesis. It was undoubtedly one of the most remarkable doctoral theses ever written. Her Nobel Prize in... 

Radium. Ra at. wt 226 (mass number of most stable isotope) at. no. 88 valence 2. A radioactive alkaline earth meta], Occurrence in earth s crust approx ]0-d% by wt. Natural isotopes 223, actinium X 224, thorium X 226 228, mesothorium 1. 22 Ra is a product of disintegration of uranium and is present in al] ores contg uranium. Separated in the form of a salt by P. and M. S. Curie from the pitchblende nf Joachimsthal, Bohemia Curie et at.. Compt. Rend. 127, 12]5 (1898). [soln of the element by electrolysis of an aq soln of radium chloride Curie, Debierne. ibid. 151, 523 (1910). 12 Ra iT, 6.7 years) produced by disintegration of thorium (I12Th) discovered in 1907 by O. Hahn in monazite residues from isolating thorium. Zaire (Congo) is the main producer of radium, Canada next. Clinical evaluation in... 

The noble gases occur as minor constituents of the atmosphere (Table 17-1). Helium is also found as a component (up to 7%) in certain natural hydrocarbon gases in the United States. This helium undoubtedly originated from decay of radioactive elements in rocks, and certain radioactive minerals contain occluded helium which can be released on heating. All isotopes of radon are radioactive and are occasionally given specific names (e.g., actinon, thoron) derived from their source in the radioactive decay series 222Rn is normally obtained by pumping off the gas from radium chloride solutions. Ne, Ar, Kr and Xe are obtainable as products of fractionation of liquid air. 

In the same year the Curies, together with G. Bemont, isolated another radioactive substance for which they suggested the name radium. In order to prove that polonium and radium were in fact two new elements, large amounts of pitchblende were processed, and in 1902 M. Curie announced that she had been able to isolate about 0.1 g of pure radium chloride from more than one ton of pitchblende waste. The determination of the atomic weight of radium and the measurement of its emission spectrum provided the final proof that a new element had been isolated. 

Radium chloride, with the molecular formula of RaClj, is a yellowish-white crystal that becomes yellow or pink upon standing. It is radioactive and soluble in water. It is used in cancer treatment and physical research. 

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