Radioactive barium

This is a radioactive element. It occurs in minute traces in barium and thorium minerals, but it can be produced by irradiation of bismuth in a nuclear reactor. (The study of its chemistry presents great difficulty because of its intense a radiation). 

The radioactive isotopes available for use as precursors for radioactive tracer manufacturing include barium [ C]-carbonate [1882-53-7], tritium gas, p2p] phosphoric acid or pP]-phosphoric acid [15364-02-0], p S]-sulfuric acid [13770-01 -9], and sodium [ I]-iodide [24359-64-6]. It is from these chemical forms that the corresponding radioactive tracer chemicals are synthesized. [ C]-Carbon dioxide, [ C]-benzene, and [ C]-methyl iodide require vacuum-line handling in weU-ventilated fume hoods. Tritium gas, pH]-methyl iodide, sodium borotritide, and [ I]-iodine, which are the most difficult forms of these isotopes to contain, must be handled in specialized closed systems. Sodium p S]-sulfate and sodium [ I]-iodide must be handled similarly in closed systems to avoid the Uberation of volatile p S]-sulfur oxides and [ I]-iodine. Adequate shielding must be provided when handling P P]-phosphoric acid to minimize exposure to external radiation. 

Synthetic chemical approaches to the preparation of carbon-14 labeled materials iavolve a number of basic building blocks prepared from barium [ CJ-carbonate (2). These are carbon [ C]-dioxide [ CJ-acetjlene [U— C]-ben2ene, where U = uniformly labeled [1- and 2- C]-sodium acetate, [ C]-methyl iodide, [ C]-methanol, sodium [ C]-cyanide, and [ CJ-urea. Many compHcated radiotracers are synthesized from these materials. Some examples are [l- C]-8,ll,14-eicosatrienoic acid [3435-80-1] inoxn. [ CJ-carbon dioxide, [ting-U— C]-phenyhsothiocyanate [77590-93-3] ftom [ " CJ-acetjlene, [7- " C]-norepinephrine [18155-53-8] from [l- " C]-acetic acid, [4- " C]-cholesterol [1976-77-8] from [ " CJ-methyl iodide, [l- " C]-glucose [4005-41-8] from sodium [ " C]-cyanide, and [2- " C]-uracil [626-07-3] [27017-27-2] from [ " C]-urea. All syntheses of the basic radioactive building blocks have been described (4). 

The properties of hydrated titanium dioxide as an ion-exchange (qv) medium have been widely studied (51—55). Separations include those of alkaH and alkaline-earth metals, zinc, copper, cobalt, cesium, strontium, and barium. The use of hydrated titanium dioxide to separate uranium from seawater and also for the treatment of radioactive wastes from nuclear-reactor installations has been proposed (56). 

Barium titanate thin films can be deposited on various substances by treating with an aqueous solution containing barium salts and an alkanolamine-modifted titanate such as TYZOR TE (151). In a similar fashion, reaction of a tetraalkyl titanate with an alkah metal hydroxide, such as potassium hydroxide, gives oxyalkoxide derivatives (KTi O(OR) ), which can be further processed to give alkali metal titanate powders, films, and fibers (152—155). The fibers can be used as adsorbents for radioactive metals such as cesium, strontium, and uranium (156). 

In 1938 Niels Bohr had brought the astounding news from Europe that the radiochemists Otto Hahn and Fritz Strassmann in Berlin had conclusively demonstrated that one of the products of the bom-bardmeiit of uranium by neutrons was barium, with atomic number 56, in the middle of the periodic table of elements. He also announced that in Stockholm Lise Meitner and her nephew Otto Frisch had proposed a theory to explain what they called nuclear fission, the splitting of a uranium nucleus under neutron bombardment into two pieces, each with a mass roughly equal to half the mass of the uranium nucleus. The products of Fermi s neutron bombardment of uranium back in Rome had therefore not been transuranic elements, but radioactive isotopes of known elements from the middle of the periodic table. 

The half-life of a radioactive species is defined as the time it takes for the activity of the sample to drop by 50%. In this activity, you will investigate the decay of 137Bam, a metastable isotope of barium that undergoes gamma decay with a half-life of several minutes. 

The radioactive element is a silvery, shiny, soft metal that is chemically similar to calcium and barium. It is found in tiny amounts in uranium ores. Its radioactivity is a million times stronger that that of uranium. Famous history of discovery (in a shed). Initially used in cancer therapy. Fatal side effects. Small amounts are used in luminous dyes. Radium was of utmost importance for research into the atom. Today its reputation is rather shaky as its decay gives rise to the unpleasant radon (see earlier). In nuclear reactors, tiny amounts of actinium are formed from radium. 

After treatment of XXXVI with aqueous barium hydroxide, the liquor contained formic, methoxyacetic, and ethoxyacetic acids, methoxyacetone, and ethoxyacetone, produced by the two modes of cleavage XXXVIa and XXXVIb. Formic acid was converted with red mercuric oxide to carbon dioxide this was recovered as barium carbonate, the radioactivity of which was a measure of the C14 incorporated into Cl of kojic acid in the biosynthetic process. The alkoxyacetones were removed from the liquor by steam distillation, and converted to iodoform and a mixture of methoxy- and ethoxy-acetic acids. The iodoform was recovered by filtration its radioactivity indicated the proportion of C14 incorporated into C4. The alkoxy-... 

Elution volume calibrations were performed using radioactive tracers of the rare earth elements and 133Ba, with atomic-absorption or flame-emission analysis of iron, sodium, potassium, calcium, and magnesium. As shown in Fig. 5.14, any barium added to the second columns is eluted at the start of the light rare earth element fraction . To ensure barium removal the sample can be put through the first column again. 

The high radioactivity of radium requires special handling techniques and precautions. Its high radioactivity is far more important than any chemical toxicity but from a chemical point of view its hazards are similar to those of barium. 

Crystallisation was one of the earliest methods used for separation of radioactive microcomponents from a mass of inert material. Uranium X, a thorium isotope, is readily concentrated in good yield in the mother liquors of crystallisation of uranyl nitrate (11), (33), (108). A similar method has been used to separate sulphur-35 [produced by the (n, p) reaction on chlorine-35] from pile irradiated sodium ot potassium chloride (54), (133). Advantage is taken of the low solubility of the target materials in concentrated ice-cold hydrochloric acid, when the sulphur-35 as sulphate remains in the mother-liquors. Subsequent purification of the sulphur-35 from small amounts of phosphorus-32 produced by the (n, a) reaction on the chlorine is, of course, required. Other examples are the precipitation of barium chloride containing barium-1 from concentrated hydrochloric acid solution, leaving the daughter product, carrier-free caesium-131, in solution (21) and a similar separation of calcium-45 from added barium carrier has been used (60). 

A radioactive form of barium, in the compound BaS04, is used to diagnose intestinal ailments. Why is a more soluble compound, such as BaCl2, not used in this procedure ... 

Radium is the last element in group 2 and is very similar to the other alkali earth metals, which makes it the largest and heaviest element in the group. It particularly resembles barium, which is just above it in group 2 of the periodic table. Radium is a bright white radioactive luminescent alkali earth metal that turns black when exposed to air. Its melting point is 700°C, its boiling point is 1,140°C, and its density is approximately 5.0 g/cm. ... 

As a nuclear reaction, the s process is relatively well understood, but the problem lies in identifying an astrophysical site for it and determining the relevant physical parameters, such as neutron flux, mean time separating two neutron captures, and temperature. It has been shown that the most propitious temperatures are those of helium fusion. Added to the fact that the surfaces of certain red giants are rich in s isotopes, such as radioactive technetium and barium, this observation confirms the idea that the s process may be related to helium fusion regions in stars. 

The most important use of barium is as a scavenger in electronic tubes. The metal, often in powder form or as an alloy with aluminum, is employed to remove the last traces of gases from vacuum and television picture tubes. Alloys of barium have numerous applications. It is incorporated to lead alloy grids of acid batteries for better performance and added to molten steel and metals in deoxidizing alloys to lower the oxygen content. Thin films of barium are used as lubricant suitable at high temperatures on the rotors of anodes in vacuum X-ray tubes and on alloys used for spark plugs. A few radioactive isotopes of this element find applications in nuclear reactions and spectrometry. 

Gross alpha and gross beta activity can be determined by various radioactive counters, such as internal proportional, alpha scintillation, and Geiger counters. Radium in water can be measured by co-precipitating with barium sulfate followed by counting alpha particles. Radium-226 can be measured from alpha counting of radon-222. Various methods are well documented (APHA, AWWA, and WEF 1998. Standard Methods for the Examination of Water and Wastewater, 20 ed. Washington DC American Public Health Association). 

After the Curies, with the assistance of M. G. Bemont, had carried out many laborious fractionations of barium chloride, they found that the most insoluble fractions were the most radioactive. In the course of her experiments Mme. Curie had learned that radioactivity is an atomic property depending solely on the quantity of active element present." For this reason the presence of another active element was suspected, and the radioactive barium chloride was therefore submitted to M. Demarcay for spectroscopic examination. He detected a new line in the ultraviolet region of the spectrum, and certain other lines, all of which were most distinct in the most radioactive preparations, and, as fractionation proceeded, the barium lines became fainter and fainter (23, 28, 52). 

The inverse technique, which makes use of complexation of compounds to the product such that it becomes insoluble (e.g. fatty acids with barium cations), is also applied. These methods are also applicable for strains that do not grow on the screening compound due to lack of a complete metabolic pathway for the starting material. A variation on this theme is the trapping of radioactive tracers, such as... 

Radioactive metal wastes from the nuclear industry are of increasing concern as the amount of waste to be disposed of increases. Current treatment of nuclear wastewater involves the addition of lime, which is effective in precipitating most metals out of solution with the exception of radium (Tsezos Keller, 1983). Barium chloride (BaCl2) is used to precipitate radium from sulfur-rich effluents as barium-radium sulfate. Other treatment methods include incineration for some solid wastes, and filtration, adsorption and crystallization for liquid wastes (Godbee Kibbey, 1981). 

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. 

Radium is chemically similar to barium it displays a characteristic optical spectrum its salts exhibit phosphorescence in the dark, a continual evolution of heat taking place sufficient in amount to raise the temperature of 100 times its own weight of water 1°C every hour and many remarkable physical and physiological changes have been produced. Radium shows radioactivity a million times greater than an equal weight of uranium and. unlike polonium, suffers no measurable loss of radioactivity over a short period of time (its half life is 1620 years). From solutions of radium salts, there is separable a radioactive gas radium emanation, radon, which is a chemically ineit gas similai to xenon and disintegrates with a half life of 3.82 days, with the simultaneous formation of another radioactive element, Radium A (polonium-218). 

Type I zirconium-nickel alloy delay compn having a formulation 60/14/26 BaCr04/KClC>4/ 70-30 Zr-Ni was used for these expts. Two different radioactive tracers, 27-day chromium-51 and 2.1-year cesium-134, were employed. The first was added to the compn in the form of BaslCr04 as a fractional percentage of total barium chromate, and the second tracer was included as 134CsQ in ppm concn of the total mixt... 

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