#### Date of Award

1988

#### Degree Type

Dissertation

#### Degree Name

Doctor of Philosophy

#### Abstract

Binary diffusion coefficients of dilute aqueous lithium, sodium and potassium hydroxides have been determined at 25{dollar}\sp\circ{dollar}C by a simplified verison of Harned's conductimetric technique. The large difference in mobility between OH{dollar}\sp-{dollar} and the cations leads to an electrophoretic effect which reduces the rate of diffusion. Measured and predicted diffusion coefficients are in excellent agreement. Diffusion-derived activity coefficients are compared with activity data obtained from emf methods.;A matrix diagonalization procedure has been developed to determine multicomponent diffusion coefficients. If linear combinations of data from multicomponent diffusion experiments with different initial concentration gradients are analyzed as simple binary data, certain combinations can be found that transform the multicomponent diffusion coefficient matrix D to diagonal form and thus yield time-invariant pseudo-binary diffusion coefficients: the eigenvalues of D. Because the matrix that diagonalizes D is given by the coefficients used to form the linear combinations, D can be obtained by the inverse transformation. As a test, ternay diffusion coefficients for aqueous NaOH + NaCl mixtures were determined. The multicomponent diffusivity of the NaOH component is much larger than its binary diffusivity, and flow of the base produces large coupled flows of NaCl.;Diffusion coefficients of copper sulfate + sulfuric acid + water mixtures have been determined at 25{dollar}\sp\circ{dollar}C using conductimetric and diaphragm cell techniques. Diffusion of sulfuric acid produces large counterflows of copper sulfate and vice versa. If diffusion of copper sulfate in sulfuric acid solutions is treated as a binary process, the measured apparent diffusivities of copper sulfate are 1 to 8% lower than the salt's true diffusivity. Expressions are developed to predict ternary transport coefficients for the mixtures.;The diaphragm cell technique has been used to measure the nine quaternary diffusion coefficients for three compositions of the system KCl + KH{dollar}\sb2{dollar}PO{dollar}\sb4{dollar} + H{dollar}\sb3{dollar}PO{dollar}\sb4{dollar} + H{dollar}\sb2{dollar}O at 25{dollar}\sp\circ{dollar}C. It is shown that pH gradients in KH{dollar}\sb2{dollar}PO{dollar}\sb4{dollar} + H{dollar}\sb3{dollar}PO{dollar}\sb4{dollar} buffers can drive large coupled flows of KCl which concentrate KCl within diffusion boundaries. Onsager's reciprocal relations for isothermal quaternary diffusion are tested and verified. By transformation of the transport coefficients for the system KCl + KH{dollar}\sb2{dollar}PO{dollar}\sb4{dollar} + H{dollar}\sb3{dollar}PO{dollar}\sb4{dollar} + H{dollar}\sb2{dollar}O, coefficients for the system KCl + KH{dollar}\sb2{dollar}PO{dollar}\sb4{dollar} + HCl + H{dollar}\sb2{dollar}O are obtained.

#### Recommended Citation

Noulty, Robert Alexander, "Diffusion In Strong And Weak Mixed Electrolyte Solutions" (1988). *Digitized Theses*. 1707.

https://ir.lib.uwo.ca/digitizedtheses/1707