Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

David W. Ebdon


An investigation was made into the possibility of determining thermodynamic ion association equilibrium constants for salts important in the study of seawater using spectrophotometry and ion selective electrodes. Calcium sulfate was used as the test salt. The success of the spectrophotometric method was found to depend upon the choice of a suitable indicator and refinement of the proper instrumental techniques. The indicators investigated were 1-(2'-hydroxy-1'-benzeneazo)-2-hydroxynaphthalene, 1-(2'-hydroxy-5'-chloro-1'-benzeneazo)-2-hydroxynaphthalene, and ammonium purpurate (murexide). Ammonium purpurate was found to be the most suitable indicator. Spectra of these three indicators and their calcium complexes at pH 10 are included in the paper. The ion selective electrode method was found to be unsuitable due to complications that arise in treating the data they provide.

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