Mobility of isotopes

The progress achieved in the field of isotope electromigration in metals, salts, and aqueous solutions since the meeting on isotope separation in Paris in 1963 is reported. It is shown that the temperature dependence of the isotope effect in liquid metals leads to the conclusion that it is a result of classical atom—atom interactions. Isotope effects in molten salts are smaller than in classical ionic gases. A three stage model is proposed for an explanation of the temperature dependences of the isotope effects in molten salts. The available data of the relative difference in mobilities of isotopes in aqueous solutions are summarized. 

It is interesting to compare these results with the mobilities of isotopes in classical ionic gases. These can be calculated as follows. 

If we put the masses of LiCl (m+ = 6.5, m. = 35.5) into the formula for the pure ion gas, we get /x li = —0.42, a value that is only by 20% larger than the experimental value for molten LiCl, /x Li = —0.34. Also the temperature independence of /x + in the gas corresponds to the low temperature dependence found in the condensates. Thus, many of the big differences between gases and condensates in structure and transport mechanisms seem to cancel out when relative differences of the eigen mobilities of isotopes are considered. 

In Figures 2, 3, and 4, the results of the various measurements of the relative difference in mobilities of isotopes in aqueous solutions have been summarized. Mi/u always means the effective relative difference in mobilities with respect to water. It includes possible contributions of isotope effects in dissociation equilibria. In judging the results it has to be kept in mind that the errors in Aw/iz are at least of the order of 0.001. 

D2O and the tritium analogue T2O (p. 41). The high bp is notable (cf. H2S, etc.) as is the temperature of maximum density and its marked dependence on the isotopic composition of water. The high dielectric constant and measurable ionic dissociation equilibrium are also unusual and important properties. The ionic mobilities of [H30] and [OH] in water are abnormally high (350 X 10 " and 192 x 10 cms per V cm... 

Fjeld RA, DeVol TA, Goff RW, Blevins MD, Brown DD, luce SM, Elzerman AW (2001) Characterization of the mobilities of selected actinides and fission/activation products in laboratory columns containing subsurface material from the Snake River Plain. Nucl Tech 135 92-108 Fleischer RL (1980) Isotopic disequilibrium of uranium alpha-recoil damage and preferential solution effects. Science 207 979-981... 

Grape, G., Price, T.D., Schroter, P., Sollner, F., Johnson, C.M. and Beard, B.L. (1997). Mobility of Bell Beaker people revealed by strontium isotope ratios of tooth and bone a study of southern Bavarian skeletal remains. Applied Geochemistry 12 517-525. 

Oxygen isotopes, sometimes combined with carbon, nitrogen, strontium, and lead isotopic measurements, have been used to study the mobility of diverse human groups such as in Teotihuacan and Oaxaca, Mexico, dating from about 300 bc to ad 750 (Stuart-Williams et al. 1996), the Kellis 2 cemetery (c. ad 250) in the Dakhleh Oasis, Egypt (Dupras and Schwarcz 2001), and in Britain (Budd et al. 2003). 

FIolk, G.J., Kyser, T.K. Don Chipley, FIiatt, E.E., Marlatt, J. 2003. Mobile Pb-isotopes in Proterozoic sedimentary basins as guides for exploration of uranium deposits. Journal of Geochemical Exploration, 80, 297-320. 

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