Title: Activity effects in seawater and other saline mixtures
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00098280/00001
 Material Information
Title: Activity effects in seawater and other saline mixtures
Physical Description: xii, 123 leaves : ill. ; 28 cm.
Language: English
Creator: White, Donald Richard, 1953- ( Dissertant )
Bates, Roger G. ( Thesis advisor )
Winefordner, James D. ( Reviewer )
Dolbier, William R. ( Reviewer )
Brezonik, Patrick L. ( Degree grantor )
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1979
Copyright Date: 1979
Subjects / Keywords: Chemistry thesis Ph. D
Saline waters -- Thermodynamics   ( lcsh )
Dissertations, Academic -- Chemistry -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
Abstract: Measurements of electromotive force (EMF) and the isopiestic technique were utilized in the determination of factors which influence the thermodynamic activity and related properties of individual species in complex saline mixtures. EMF measurements in cells without liquid junction were carried out to determine the mean activity coefficient of HC1, y+> in electrolyte mixtures resembling seawater. In mixtures of HCl-MgCl 2 , it was found that y + decreases in a linear fashion as HC1 is replaced by MgCl„ while maintaining constant total ionic strength and, in this respect, obeys Harned's Rule. These measurements were carried out at four ionic strengths, namely I = 0.1000, 0.3809, 0.6729, and 0.8720 mol kg -1 at nine temperatures from 5 to 45°C. The three higher ionic strengths correspond to seawater of salinities 20, 35, and 45°/00. In addition, studies were made on the system HCl-NaCl-MgCl 2 at I •= 0.6729, the molal ratio of NaCl to MgCl 2 being maintained at 7.202 as in natural seawater. The Harned coefficients obtained from all measurements were found to decrease slowly with temperatr ture. The trace activity coefficients of HC1, y ± , were calculated from the Harned equation in two ways. First, by combining Harned coefficients from the HCl-MgCl 2 study with those from an earlier HCl-NaCl study, weighting the two with respect to their relative ionic strength contributions to seawater. Secondly, they were calculated using Harned coefficients from the HCl-NaCl-MgCl 2 study. All values were found to be identical with those measured earlier in total artificial seawater (excluding sulfate) at all ionic strengths and temperatures included in the experiments. The concept of single-ion activity and the problem of liquid-junction potentials in pH measurement were addressed in a study of pH in synthetic seawater and saline media simulating serum. Measurements of EMF in a cell with liquid junction at 25°C were carried out in buffered artificial seawater at salinities of 30, 35, and 40°/00, each containing a Tris buffer at molalities of 0.02, 0.04, and 0.06. Comparison of the pnu values calculated by the operational definition with those determined from measurements in cells without liquid junction demonstrates that a residual liquidjunction potential exists which varies with salinity. Within a given salinity, however, pm„ values calculated by the operational definition are identical regardless of Tris buffer concentration. Evidence is presented that pH measurement of blood plasma and other clinical media at ionic strengths of 0.16m vs. the NBS standards may involve residual liquid-junction errors amounting to 0.03 to 0.05 pH unit. EMF measurements of cells both with and without liquid junction indicated that residual liquid-junction effects may be nearly eliminated by matching the ionic strength of the standard to that of the sample. A phosphate buffer composed of 0.005217m KH 2 P0 4 , 0.018258m Na„HP0 and 0.1m NaCl (buffer ratio 1:3.5 and I = 0.16m) is to be preferred to the NBS phosphate buffer (I = 0.1m) for measurements of this sort. Isopiestic measurements were carried out at 25°C on mixtures of electrolytes having to do with seawater, NaCl-SrCl 2 and NaCl-Na 2 C0 3 , and the resulting osmotic coefficients were determined in the ionic strength range 0.3 to 6.0m. The data were fitted to the current treatments of Pitzer and Scatchard for solutions of mixed electrolytes. Activity coefficients were calculated for the individual solutes in each mixture using the best-fit ion interaction parameters from the Pitzer treatment. These are discussed in light of the excess free energies of mixing calculated from the corresponding Scatchard parameters. Xll
Statement of Responsibility: by Donald Richard White, Jr.
Thesis: Thesis (Ph. D.)--University of Florida, 1979.
Bibliography: Bibliography: leaves 117-121.
General Note: Typescript.
General Note: Vita.
 Record Information
Bibliographic ID: UF00098280
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000099742
oclc - 07119964
notis - AAL5200


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