Radium fractions

Radioactivity The ability possessed by some natural and synthetic isotopes to undergo nuclear transformation to other isotopes, 513 applications, 516-518 biological effects, 528-529 bombardment reactions, 514-516 diagnostic uses, 516t discovery of, 517 modes of decay, 513-514 nuclear stability and, 29-30 rate of decay, 518-520,531q Radium, 521-522 Radon, 528 Ramsay, William, 190 Random polymer 613-614 Randomness factor, 452-453 Raoult s law A relation between the vapor pressure (P) of a component of a solution and that of the pure component (P°) at the same temperature P — XP°, where X is the mole fraction, 268... 

Figure 1. Schematic illustration of factors influencing the production and migration of radon in soils and into buildings. Geochemical processes affect the radium concentration in the soil. The emanating fraction is principally dependent upon soil moisture (1 0) and the size distribution of the soil grains (d). Diffusion of radon through the soil is affected primarily by soil porosity ( ) and moisture content, while convective flow of radon-bearing soil gas depends mainly upon the air permeability (k) of the soil and the pressure gradient (VP) established by the building.

Figure 7. Radon concentration growth in the outer volume during the first fifteen hours after closure. The exhalation can is radon-tight (y= 1). The exhalation material is dry sand mixed with 11 % ground uranium ore by weight. The diffusion length, L, is 1.4 m, the sample thickness, d, is 26 cm and the outer volume height, h, is 4.0 cm. Other parameters of the sample are as follows porosity 0.47, radium concentration 1180 Bq kg, emanation fraction 0.33, bulk density 1710 kg m 3 (experiment + theory).

Radon in indoor air arises primarily from radium in the soil. The radon in the soil gas flows under a pressure gradient from the soil into the building. In some cases building practices can lead to high radon levels in the living areas of the house. Radon is chemically quite inert and does not pose a significant radiation health hazard in itself because the retained fraction in the body is so low (Mays et al., 1958). It is, however, an excellent vehicle for the dispersion of its short-lived radioactive decay products. 

Solutes. Radium-Barium Fractionation. Ind, Engng. Chem. 40, 76 (1948). 

ISOTOPES There are no stable isotopes of radium. Radium has 25 known radioisotopes, ranging from Ra-206 to Ra-230. Their half-lives range from a fraction of a second to hundreds of years. Radium-226 was discovered by the Curies and has a half-life of about 1630 years. Ra-226 is the most abundant isotope, and thus, Ra-226 is used to determine radium s atomic mass. 

The element may be obtained from radioactive lead-210 (also, known as RaD, the lead fraction in the extraction of radium from uranium ore) by successive beta decay ... 

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. 

In 1901 Demarcay made an elaborate series of fractionations of samarium magnesium nitrate which resulted in the discovery of a new earth, europia (3, 31, 59). Since he could read a complex spectrum like an open book, he was frequently called upon to pass judgment on supposedly new elements, and was the first to observe the new lines of radium in some barium salts brought by Pierre Curie. 

I was certainly privileged, for I saw with my own eyes the birth of radium. Pierre Curie, who was my teacher, rendered me the incomparable honor of according me his confidence and friendship. I saw Mme. Curie work like a man at the difficult treatments of great quantities of pitchblende. I saw the first fractionations of the bromides of barium-radium. I saw the radium-bearing crystals shine in the dark before the radium spectrum could be observed in them. Every Sunday we used to go with Langevin, Perrin, Debierne,... 

Finally, the ionization current per gram, sy, has been calculated for 21 days after the event and compared with s95. Unlike the cloud sample, the KH sample was fractionated. The standardized (i.e., corrected to a reading of 560 X 10"9 ma. for a 100-/xgram radium standard) unfractionated value of this ratio at 21 days has been determined by Mackin to be 4.7 X 10"21 ma. per fission (10). The value determined here is only half of the theoretical value. Crockers calculations show that 140La contributes 60% of the ionization rate from an unfractionated sample at this time (2). Depletion in 140La therefore undoubtedly contributes to the... 

Chemically related to barium, radium is recovered from its ores by addition of barium salt, followed by treatment as fur recovery of barium, usually as the sulfate. The sulfates of barium and of radium are insoluble in most chemicals, so they arc transformed into carbonate or sulfide, both of which are readily soluble in HC1. Separation from barium is accomplished by fractional crystallization of the chlorides (or bromides, or hydroxides). Dry, concentrated radium salts are preserved in sealed glass tubes, which are periodically opened by experienced workers to relieve the pressure, The glass tubes are kept m lead shields,... 

The uranium series contains two radionuclides of special interest, 226Ra (ti/2 = 1600 y) and its daughter, 38 d 222Rn. 226Ra (and its daughters) are responsible for a major fraction of the radiation dose received from internal radioactivity. Radium is present in rocks and soils, and as a consequence in water, food, and human tissue. The high specific activity and gaseous decay products of radium also make it difficult to handle in the laboratory. 

The excretion of parenterally acquired radium from the human body occurs in two phases the first phase is very rapid, but the small fraction that remains in the body is ultimately released very slowly, presumably due to the turnover of bone matrix. An equation to describe the retention of radium in the human body, derived by Norris et al. (1955), predicts that the retention of radium 10 days after acquisition will be 16%, dropping to 2.5% at 1 year, 0.76% at 10 years, and 0.43% at 30 years. A similar equation has been developed for dogs. 

The decay constant of 220Rn is 6000 times greater than that of 222 Rn, so from (1.4) L is about 80 times less, that is only about 1 cm. The fraction of 220Rn atoms which escape from the rock crystals to the interstitial air is apparently about the same as for 222Rn, and since the specific activities of the thorium and radium chains are similar, equation (1.6) implies that the emanation of 222Rn should be 80 times greater... 

The radiochemical procedures required skill and delicacy but they were not conceptually new. To verify the presence of radium, Hahn and StraKmann tried to separate it from its barium carrier, using Marie Curie s method of fractional... 

---