Measured distribution coefficients for

Hexavalent neptunium. Distribution coefficients of hexavalent neptunium at 25, 45, and 60 C measured by Srinivasan et al. [S18, S19] are simply related to measured distribution coefficients for hexavalent uranium by Eq. (10.26), with an average deviation of only 5 percent. 

Dm is the measured distribution coefficient for M = Th between the organic and aqueous phases, X4 the distribution coefficient of the uncharged complex TI1L4, A the dissociation constant of HL and Ki the distribution coefficient for HL between 1 M NaC104 and toluene. 

In QSAR studies the lipophilic character of a compound is usually expressed in terms of the logarithm of the octanol/water partition coefficient (i.e., log P). Experimentally, the octanol/water partition coefficient is determined by the shake-flask method. Unfortunately, it is often difficult to obtain precise values for the octanol/water partition coefficient because solute impurities will affect the measured distribution coefficient. For example, reported log P values for benzene (1-5) vary from 1.56 to as high as 2.34. 

Marcus measured distribution coefficients for macro amounts of U,... 

Mysen (1976) measured distribution coefficients for Sm in olivine and Ca-poor pyroxene by beta track mapping of synthetic silicates. That technique allows use of very low concentrations of a trace element. Mysen reported a strong concen-... 

D Reese, G Irwin, L Dittert, C Chong, J Swintosky. Nonemulsifying method for measuring distribution coefficients. J Pharm Sci 53 591, 1964. 

Campbell, J.R., Luthy, R.G., and Carrondo, M.J.T. Measurement and prediction of distribution coefficients for wastewater aromatic solutes, Environ. Sci. Technol., 17(10) 582-590, 1983. 

Measured mass related distribution coefficients for granite... 

Sr(II), and Ba(II), for the sodium form of montmorillonite. The Sr(II) results are from a different set of measurements than those in Figure 2, but are in good agreement with them. Effects of loading are small up to the several percent of ion-exchange capacity covered. Values of distribution coefficients for these three ions fall in a narrow range. 

Transition metal dopants and impurities are probably incorporated substitutionally for Ti in BaTi03. Emission spectrographic analyses indicate that the distribution coefficients for Mn and Fe dopants are on the order of 1 to 2, i.e., the crystals are slightly enriched relative to the melt. Cr and Ni may have distribution coefficients slightly less than 1. For Co, the measured concentrations in the crystals display considerable scatter we estimate that the distribution coefficient is on the order of 4. Fe is the most prevalent transition metal impurity and is typically present at a concentration of 10-15 ppm by weight. Si, Al, Mg, and Cu are also typically present at 5-50 ppmw. Fe and Cr impurities have also been observed by EPR spectroscopy, although Cr could not be detected by emission spectroscopy, with a detection limit of 10 ppmw. 

The different terms of Equation 1 were obtained as follows— /ce, formal potential of the Ce(IV)-Ce(III) couple in the medium, was taken from publications [Ce(IV)]a and [Ce(IV)]o have been measured by direct absorption spectrophotometry [Ce(III)] was calculated by difference between total cerium, titrated by potentiometry, and tetravalent cerium [Bk(IV)]a was calculated from the solvent beta counting, allowing for the measured distribution coefficient of Bk(IV) [Bk(III)] was determined by subtracting the [Bk(IV)]a value from the aqueous counting in all cases [Ce(III)]o and [Bk(III)]o were found to be negligible. 

The object of the present investigation was to test this relationship by measuring distribution coefficients and phase-boundary potentials for several different salts. The work fell into three parts ... 

It is always advisable to measure the distribution coefficient for the specific liquid/ liquid extraction before designing a full treatment system however, for a preliminary trade-off study between different treatment alternatives, this may not be practical. In addition, the selection of the extraction solvent would be facilitated if we could narrow the choices to a subset of organic solvents. There are a number of organic liquid/water distribution coefficients, available in the literature however, by far the system... 

Erionite and the related zeolite T exclude branched chain paraffins, so that n-paraffins are selectively cracked or hydrocracked over these catalysts. However, even n-paraffins have diffusities several orders of magnitude lower than in large pore zeolites. Earlier work on hydrocracking over erionite catalysts gave unexpected product distributions, with maxima at C4 and C12 and essentially no Cg product. Gorring measured diffusion coefficients for migration of n-paraffins in KT zeolite. An unexpected phenomenon, termed the window... 

Procedures. Procedures were developed for measuring plutonium distribution coefficients for batch equilibrium adsorption measurements and for measuring plutonium breakthrough concentrations for column flow-through adsorption experiments. 

Bone char appears to be the most effective adsorbent for removal of plutonium from the wastewaters because of high distribution coefficients for plutonium adsorption and rapid adsorption. The capacity of bone char for plutonium absorption can be calculated from a measured Kd value, assuming a reversible equilibrium adsorption reaction and a linear adsorption isotherm. If the capacity is defined as the point where the plutonium concentrations in the column feed and effluent are equal, the maximum volume of wastewater that can be treated (V ax) is (14)... 

Anion-exchange distribution coefficients for most metallic elements in sulfuric acid solution have been measured [28, 29], Uranium(Vl), thorium(IV), molybdenum(VI). and a few other elements are retained selectively from such solutions. Thorium(lV) is taken up selectively by anion-exchangers from approximately 6 M nitric acid [30]. 

The concept of bioconcentration is derived from that of distribution coefficients in physical chemistry in these, the equilibrium concentrations of a compound distributed between two phases are measured, for example, between water and a water-immiscible solvent such as hexane. If partitioning were a passive reaction, direct physicochemical measurements of the partition between an aquatic phase and a suitable model for the biological membrane would be possible. It would therefore be attractive to measure distribution coefficients in a chemically defined system and to seek a correlation between the values found and those obtained by direct measurements in biota. 

To insure that a statistical average behavior is observed in the chemical experiments with No and Lr, it has been necessary to make repeated measurements for each data point. Indeed, the determination of the distribution coefficients for Lr in a solvent extraction experiment required over 200 experiments to define the behavior of about 150 atoms of Lr (JL). Experiments of this kind are exceptionally difficult and computer-controlled equipment has been devised to perform either a portion or all of operations needed for the chemical tests and the analysis of samples. Computer automation, although requiring a larger effort to implement, permits an experiment to be repeated many times in rapid sequence with the added advantage of doing each quickly before the complete decay of the radioactive atoms of a shortlived isotope. 

Tetravalent neptunium. Srinivasan et al. [S18, S19] measured distribution coefficients of tetravalent and hexavalent neptunium and hexavalent uranium as functions of nitric acid and uranyl nitrate concentrations. At 45 and 60°C, the ratio of the observed [S19] separation factor for tetravalent neptunium to that of hexavalent uranium can be correlated within an average deviation of 6 percent by Eq. (10.25),... 

The multiple gas-phase aspect (repeating equilibration with a second volume of pure gas) provides for the separation of a given class of organic compounds (hydrocarbons) from others. The measured distribution coefficient also assists in the identification of compounds found by GC. These and other aspects of the gas equilibration method will be presented in greater detail later. 

We shall first examine the reaction chromatographic method in which the derivatives formed are not analysed and the reaction is assessed by the variation of the concentration of the sample compounds in one of two phases that are in equilibrium. This combined distribution-chromatographic method makes it possible to measure quantitatively the contents of components in a common unresolved peak. As an example we can cite the determination of isobutene and butene-1, which are not separated on most stationary phases, in a common peak. First the phase distribution of components in the sample was established in a liquid—vapour system at 20°C, with silver nitrate solution in ethylene glycol as the liquid phase. The distribution coefficients for isobutene and butene-1 in... 

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