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Measurement and control of pH in hydrothermal solutions

Description: Hydrogen-electrode concentration cells with liquid junction are routinely used to measure the pH of aqueous solutions from 0 to 300 C. Results include the dissociation constants of common acids and bases and the hydrolysis and complexation of metal ions in aqueous electrolytes over a wide range of salinities. Recently, we have utilized these cells to examine the sorption of H{sup +} on mineral surfaces, the solubility of minerals with continuous in situ pH measurement, and the thermal decompositon rates of organic acids.
Date: December 31, 1995
Creator: Wesolowski, D.J.; Palmer, D.A. & Mesmer, R.E.
Partner: UNT Libraries Government Documents Department

Solvent extraction of cesium by substituted crown ethers

Description: The extraction of alkali metal nitrates by 18-crown-6, 21-crown-7, and 24-crown-8 ethers, bearing cyclohexano, benzo-, t-alkylbenzo, and furano- substituents, in 1,2-dichloroethane has been surveyed. Introduction of a furano substituent onto the macrocyclic ring of 18-crown-6 or 21 crown-7 ethers causes a significant reduction in both extraction efficiency and selectivity. Addition of an additional benzo group to dibenzo-21 -crown-7, to give tribenzo-21 -crown-7, decreases both extraction efficiency and selectivity, whereas addition of one or two additional benzo groups to dibenzo-24-crown-8 increases the extraction efficiency and selectivity for the larger ions Rb+ and Cs{sup +} Detailed equilibrium modeling of the extraction by lipophilic 21 -crown-7 ethers indicates that the addition of t-alkyl substituents onto the benzo groups has only a minor effect on the extraction of cesium nitrate by dibenzo-21 -crown-7 ethers.
Date: December 31, 1996
Creator: Sachleben, R.A.; Deng, Y.; Palmer, D.A. & Moyer, B.A.
Partner: UNT Libraries Government Documents Department

Measurements of the Distribution of Solutes between Liquid Water and Steam

Description: Direct measurements of the concentration of solutes in both liquid and steam phases in equilibrium with each other have been made in a static mode utilizing a platinum-lined autoclave to a maximum of 350 deg C. Partitioning constants were derived from these measurements based on existing experimental or estimated values of the stoichiometric mean activity coefficients for the solutes in the liquid phase. Independent measurements of the conductance of some of the solutes in dilute aqueous solutions to 600 deg C and 300MPa were also made. The combined results are discussed in terms of a speciated model and the implications of these results to industrial and natural hydrothermal processes are presented. PARTITIONING CONSTANT, ION-ASSOCIATION, CONDUCTIVITY, SPECIATION, CORROSION.
Date: December 31, 1997
Creator: Palmer, D.A.; Simonson, J.M. & Ho, P.C.
Partner: UNT Libraries Government Documents Department

Potentiometric studies at ORNL with hydrogen electrode concentration cells

Description: The absence of suitably stable reference electrodes for and to 300 C led ORNL to develop hydrogen electrode concentration cells for studies of equilibria of interest in reactor and steam generator systems to about 300 C during the late 1960`s and seventies. During the intervening two dozen years over twenty scientists have participated in potentiometric studies at Oak Ridge and much of that work will be summarized in this paper. A description of hydrogen electrode concentration cells developed in the late sixties and currently in use at Oak Ridge is given. The method of measurement, data interpretation, and published results are reviewed for studies of acid-base ionization, metal ion hydrolysis, and metal complexation reactions using principally such cells in titration or flow modes. 41 refs.
Date: December 31, 1994
Creator: Mesmer, R. E.; Palmer, D. A. & Wesolowski, D. J.
Partner: UNT Libraries Government Documents Department

Partitioning of solutes between liquid water and steam in the system {l_brace}Na-NH{sub 4}-NH{sub 3}-H-Cl{r_brace} to 350{degree}C

Description: Measurements have been made of the partitioning of solutes between liquid and vapor phases for hydrochloric acid and chloride salts found in both power plant steam cycles and in natural geothermal systems. Static sampling of equilibrium liquid and vapor phases extended from 350 C to the lowest temperatures for which reliable analytical determinations of vapor-phase solute concentrations could be made. Equilibrium constants for the partitioning of the various solutes were calculated from the measured equilibrium compositions, and represented as functions of temperature and solvent density over the full temperature range investigated. These equilibrium constants can be used to calculate equilibrium compositions of coexisting liquid and vapor phases under conditions ranging from steam production from saline geothermal brines to early-condensate formation in all-volatile treatment steam cycles.
Date: December 31, 1994
Creator: Simonson, J. M. & Palmer, D. A.
Partner: UNT Libraries Government Documents Department