Thesis (Ph. D.)--University of Washington. / Vita. Bibliography: L. 66-68.

Thesis (Ph. D.)--Louisiana State University, Baton Rouge, La. / Vita. Bibliography: 1. 117-120.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1940. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 39-40).

No description available.

The novel Vanadium Bromide (V/Br) redox flow cell employs a V (III)/V (II) couple in the negative half-cell and a Br/Br2 couple in the positive half-cell, with hydrobromic acid and hydrochloric acid as the supporting electrolyte. This study evaluated the chemical and electrochemical properties of the electrolytes and assessed experimental and commercial membranes for use in the V/Br flow cell. A number of techniques were employed to characterise the composition of the V/Br flow cell electrolytes. During charge, the conductivity of the positive half-cell electrolyte increased, whilst the density and viscosity increased. The reverse was observed for the negative half-cell. The UV-visible spectra of the electrolytes showed characteristic peak wavelengths of the vanadium oxidation states and provided and insight into the halogenated species forming during the operation of the V/Br flow cell. The electrochemical properties of the electrolytes were also examined using cyclic voltammetry. NMR studies examined the relationships between the 35CI and 79Br nuclei in the presence of halide and paramagnetic vanadium ions. It was established that the SOC and performance of the V/Br flow cell can be measured by changes in slllectral chemical shifts and line widths. Small-scale cycling experiments were conducted to evaluate the performance of ion exchange membranes in the V/Br redox flow cell. Of the membranes evaluated, a number were not suitable for use due to high membrane resistances or low chemical stability. The perfluorinated Nafion?? and Gore Select?? ion exchange membranes proved to be the most chemically inert and showed low resistances. The Gore Select?? membranes did however exhibit blistering during extended cycling. The chemical stability and cycling performance of the HiporeTM microporous separator showed promise for future studies to optimise the selectivity and ion exchange capacity of the membrane. Tests of membrane ion exchange capacity, diffusivity and conductivity mirrored the properties displayed in the cell cycling experiments. Results suggested that the structural characteristics of the membrane (including functionality and crosslinking) greatly influenced membrane properties and performance. Tests of long term stability showed a negative change in membrane properties. These changes did not however reflect measured changes during cell cycling experiments.

Thesis (Ph. D.)--Bryn Mawr College, 1922. / Vita.

Thesis.

Thesis (Ph. D.)--Columbia University, 1933. / Vita. "By J.W. Palmer and H.T. Clarke." "Reprinted from the Journal of biological chemistry, vol. XCIX, no. 2, January, 1933." Bibliography: p. 444.

The work described in subsequent pages arose from certain difficulties in the current knowledge of the bond dissociation energies (D) of compounds of the type C6H5CH2-X. For the reaction C6H5CH2-X → C6H5CH2 - + X – D k.cals. (1) we can write D(C6H5CH2-X) = ΔHf(C6H5CH2-) + ΔHf(X-) - ΔHf(C6H5CH2-X) (2) where ΔHf is the heat of formation of a chemical entity. It has been the task of many recent researches to evaluate (D) for different compounds. Since the last two terms in the thermochemical equation are often known, a determination of D(C6H5CH2-X) permits the heat of formation of the benzyl radical to be evaluated. It is obviously necessary that a consistent scheme should produce a single value for ΔHf(C6H5CH2-) and one which is independent of the nature of X. Early work in this field by Szwarc had produced such agreement, but recent more detailed work, threw doubt on his findings for D(C6H5CH2-H). Since his values were claimed to be cross-checked through (2), it was clear that his work on the determination of D(C6H5CH2-H). Since his values were claimed to be cross-checked through (2), it was clear that his work on the determination of D (C6H5CH2-Br)4 might also be in error, for it was claimed to agree with his toluene results. The pyrolysis of bromides in the presence of excess toluene has been the main kinetic practised by Szwarc, and benzyl bromide is one of many bromides which have been investigated by him. In theory the method requires that the primary dissociation R – Br → R- + Br- (3) shall be followed by the inhibition of secondary processes by reactions R- + C6H5CH3 → RH + C6H5CH2- (4) Br- + C6H5Ch3 → HBr + C6H5CH2- (5) 2C6H5CH2- → C6H5CH2CH2C6H5 (6) Swarc claimed that the method showed the decompositions to have a first order dependence on RBr concentration, and that the temperature dependence of the velocity constant followed an equation log10k = log10A – E/4.57T for the most extensively investigated cases. He laid stress on the fact that the values of A he obtained were close to 1013 sec−1, which is the expected value for a first order reaction, and hence that he was observing the dissociation process (3). As usual in this field the energy of activation E was taken as the bond dissociation energy. Justification for this assumption will be considered in the next section. Benzyl bromide was one of the compounds Szwarc investigated more extensively and the results conformed with the above generalisations. In case of several other bromides the published results do not justify his assumption that the temperature independent factor would be found to have the value 1013 sec−1 under a more exhaustive scrutiny. These items prompted a re-examination of the whole toluene carrier gas technique as applied to benzyl bromide. In one form of this technique, and probably the most widely used version, a stream of toluene vapour entrains the halide Rbr by passage over the surface of the latter. Although temperatures above the dew point of toluene were advocated by Szwarc, elementary considerations suggested that solution of toluene in the Rbr could not be prevented by this and uniformity of entrainment would suffer greatly. Varying concentrations of reactant would result and kinetic deductions would be invalidated. As described in later pages, some simple experiments showed this suspicion about the toluene carrier gas technique to be correct. In view of this end and the chemical uncertainties quoted earlier, there seemed a need to re-investigate the pyrolysis of benzyl bromide fairly extensively. In later pages the details of such work are given together with work on the chlorobenzyl bromides. Before dealing with the practical aspects of the work a short survey of the relevant previous investigations and kinetic techniques used is given.