Portland State University. Department of Chemistry.
Dennis W. Barnum
Date of Publication
Master of Science (M.S.) in Chemistry
Iron -- Solubility, Hydrolysis
1 online resource (2, viii, 58 p.)
The hydrolysis of iron(III) ions in aqueous solution forms a series of soluble hydroxide complexes with associated equilibrium constants. The solubility of iron(III) is controlled by the various soluble hydroxide complexes, and can, in theory, be calculated from the pH and equilibrium constants. Experimental verification of the calculated solubility has proven difficult due to the lack of sensitive analytical techniques and the presence of colloidal ferric hydroxide interferences. Recently, electrochemical methods for the determination of low levels of iron(III) have been developed using adsorptive cathodic stripping voltammetry which relies on the interfacial accumulation of the chelate of iron with Solochrome Violet RS on a hanging mercury drop electrode. The purpose of this investigation was to experimentally verify the calculated solubility of iron(III) in the pH 4-12 region using adsorptive cathodic stripping voltammetry. The ubiquitous nature of iron requires background levels of iron be reduced below the experimental concentrations to be determined. Attempts to lower the background levels of iron were ineffective as concentrations below about 10-8M iron could not be attained. Verification of the calculated solubility of iron(III) was unsuccessful as background concentrations of iron(III) and tr.e presence of colloidal ferric hydroxide hindered the experimental results. The dissolution of the ferric hydroxide colloids coupled with the background levels of iron resulted in the determination of experimental concentrations which exceeded theoretical values by two to four orders of magnitude.
Menting, Victor L., "Solubility Studies of Iron(III) Oxides and Hydroxides" (1994). Dissertations and Theses. Paper 4853.