Coulometric-Acidemetric Titrations and Related Studies in Acetic Acid-Acetic Anhydride Solutions

Citation

Mather, William Brewster (1961) Coulometric-Acidemetric Titrations and Related Studies in Acetic Acid-Acetic Anhydride Solutions. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/4X11-3S02. https://resolver.caltech.edu/CaltechETD:etd-05042006-104755

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Part I: A coulometric titration of bases is described in which the supporting electrolyte consists of a sodium perchlorate solution in acetic anhydride, containing a small amount of acetic acid. A number of inorganic bases (sodium acetate, potassium hydrogen phthalate, sodium fluoride, sodium chloride, sodium nitrate and sodium sulfate have been titrated in this solvent with accuracies of ±0.2%. Perchloric acid is generated with 100% efficiency with a mercury anode. The end point is determined potentiometrically. Application of this coulometric technique has been made to the determination of fluoride ion. Most anions other than perchlorrate display basic character in this solvent and were titrated with the fluoride. The titration has been applied to the determination of the total base in mixtures of fluoride with sulfate, chloride and nitrate. In some instances two end points can be observed with binary mixtures, so that analysis for each component is possible. An example is a mixture of fluoride and chloride. Part II: An investigation of reactions occurring at and around platinum electrodes, both anode and cathode, in the electrolysis of a solution of 0.1 VF sodium perchlorate in acetic anhydride, which contains a small amount of acetic acid (0.1 VF), is described. Chronopotentiometric techniques have been extensively employed in these studies. The cathode reaction is the reduction of the small amount of acetic acid present in the acetic anhydride solution. The reduction products are hydrogen and acetate ion: [...]. The anode reaction is probably the oxidation of acetic acid or acetic anhydride to form hydrogen ions or acetylium ions: [...]. The acetylium ions condense rapidly with the solvent to form slightly dissociated products: [...]. Further condensations to higher, very slightly dissociated products occur. These higher condensation products, in the protonated form, are such weak acids that they do not react with sodium acetate in the acetic anhydride solution. Thus, hydrogen ions are effectively lost from the solution. Coulometric-acidimetric titrations of bases, performed with hydrogen ions generated at a platinum anode in acetic anhydride, were unsuccessful because of this loss of hydrogen ions. An appendix is included in which attention is drawn to the very reducing potentials attainable in acetic anhydride. From preliminary experiments it appears that sodium ion is more easily reduced than the acetic anhydride solvent.

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