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[en] To investigate the movement of brine along grain boundaries in polycrystalline salt, measurements have been made of the radial flow of brine through the interface between cylindrical salt crystals under axial stresses to 140 bar and temperatures to 80⁰C. For constant conditions, the total flow of brine showed a linear dependence on the logarithm of time, and the reciprocal permeability increased linearly with time. Loss of salt from the interface by pressure solution effects was more than enough to account for the decrease in the apparent thickness of the interface (i.e., that which may be estimated for an interface of the same permeability formed by plane parallel surfaces). This apparent thickness, initially as large as 10 μm, decreased to as little as 0.2 μm with exposure to stress and flowing brine. It decreased quickly with sudden increases in axial stress and usually increased, though not reversibly, with decreases in stress. The rate of increase in the reciprocal permeability with time was roughly proportional to the stress and to the square of the hydraulic pressure drop. Assuming similar apparent thicknesses for the grain boundaries in polycrystalline salt, permeabilities are predicted that are quite consistent with the low values reported for stressed core specimens

[en] The H₂ reduction equilibrium of UF₄ according to the equation: UF₄ + 1/2H₂(g) = UF₃(d) + HF(g) has been measured in selected molten fluoride solutions from 500 to 800⁰C. Absorption spectrophotometry was used to determine UF₃ and UF₄ concentrations in equilibrium with a gas mixture containing HF in approximately 1 atm H₂. By measuring all components as a function of temperature and melt composition, equilibrium quotient expressions for the reduction, log₁₀ Qsup(R) = a - b/T have been obtained where a = 3.771, 3.587, 3.133 and b = 8900, 8225 and 7296 for the LiF-BeF₂ solutions of 66-34, 57-43 and 48-52 mole % compositions, respectively. For a LiF-BeF₂-ThF₄ (72-16-12 mole %) solution, log₁₀ Qsup(R) = 3.952-9183/T where Q is in atmsup(1/2). By defining the standard state for each solute so that its activity coefficient is unity when it is present in very low concentration in LiF-BeF₂ (66-34 mole %), activity coefficient ratios, γsub(UF₄)/γsub(UF₃), for the other solvents have been calculated from the above expressions. These data have extended previous activity coefficients over wider temperature and solvent ranges. (author)

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[en] Additional results confirm that during most of the consolidation of polycrystalline salt in brine, the previously proposed rate expression applies. The final consolidation, however, proceeds at a lower rate than predicted. The presence of clay hastens the consolidation process but does not greatly affect the previously observed relationship between permeability and void fraction. Studies of the migration of brine within polycrystalline salt specimens under stress indicate that the principal effect is the exclusion of brine as a result of consolidation, a process that evidently can proceed to completion. No clear effect of a temperature gradient could be identified. A previously reported linear increase with time of the reciprocal permeability of salt-crystal interfaces to brine was confirmed, though the rate of increase appears more nearly proportional to the product of sigma ΔP rather than sigma ΔP² (sigma is the uniaxial stress normal to the interface and ΔP is the hydraulic pressure drop). The new results suggest that a limiting permeability may be reached. A model for the permeability of salt-crystal interfaces to brine is developed that is reasonably consistent with the present results and may be used to predict the permeability of bedded salt. More measurements are needed, however, to choose between two limiting forms of the model

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[en] The reactions of polycyclic aromatic hydrocarbons in molten antimony trichloride at temperatures from 80 to 175⁰C have been studied by in situ ¹H NMR and quench and separation techniques. Decomposition takes place by a complex series of hydrogen redistribution reactions whose net effect is a disproportionation of a type not previously known to occur. The reaction of anthracene (I) was studied in detail. Some of the anthracene molecules lose aryl-bound hydrogen and are condensed into larger molecules with aryl-aryl bonds such as the asymmetric bianthracenes (IV, V, and VI) and anthraaceanthrylenes (VII and VIII). The hydrogen released by these reactions is quantitatively captured by other anthracene molecules to form hydroaromatic molecules such as the 9,10-dihydro- and 1,2,3,4-tetrahydroanthracenes (II and III). The catalytic role of the solvent's Lewis acidity was demonstrated by the fact that the addition of a few mol % of a strong chloride donor reduced the reaction rates by a large factor. The reaction behavior of a group of related arenes (naphthalene, phenanthrene, chrysene, pyrene, perylene, and naphthacene) of widely varying basicity and oxidizability was also surveyed. 2 figures