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Hydrogen ion mobility in normal and heavy water solutions of electrolytes

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Northey, Helen L 1975 , 'Hydrogen ion mobility in normal and heavy water solutions of electrolytes', PhD thesis, University of Tasmania.

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Abstract

Proton and deuteron mobility in normal and heavy water solutions
of some alkali halides and tetraalkylammonium bromides has been
measured polarographically, and the diffusion coefficients of the
proton and deuteron calculated using a corrected form of the Ilkovic
equation. The value of the constant in the correction factor of the
equation was found to be 17, in agreement with other experimental and
theoretical work.
In all cases, proton and deuteron diffusion was retarded as
concentration of supporting electrolyte increased. This was also
found to occur when cadmium ion diffusion was measured in some nitrate
solutions. The main difference was the rapid decrease for hydrogen
and deuterium ion diffusion in the 0 - 1 m concentration range. The
similarity of both diffusion current and half-wave potential vs.
concentration plots for hydrogen and cadmium ions at higher concentra
tions seemed. to point to a complete reduction of any abnormal diffusion
mechanism for the hydrogen ion, in agreement with the conclusions drawn
by some other workers.
When, however, results were analysed in terms of the effect of
electrolyte concentration on the excess or Grotthuss mobility of the
hydrogen and deuterium ions, it was found that some of the Grotthuss
component was present even up to concentrations of supporting electro
lyte'of about 4 m. These results also raise some questions about the
accepted mechanism for the transport of normal and heavy hydrogen ions
in electrolyte solutions. It appears that it is the field-induced
orientation of water molecules or hydrogen ions that is the rate
determining step in proton and deuteron transport. This exceeds the rate
of thermal orientation, is slower than proton or deuteron
tunnelling and has been justified theoretically. The thermal orien
tation of water molecules appears to be no guide to the field-induced
orientation in the presence of electrolytes.
The lower diffusion currents in heavy water solutions are attri
buted to the more extensive deuterium bonding as compared with the
hydrogen bonding in normal water. The greater reduction of proton
and deuteron diffusion in solutions of electrolytes considered to be
structure-makers is, therefore, in agreement with this.
Energy of activation measurements support generally the above
conclusions.
When hydrogen ion diffusion coefficients obtained in this study
were compared with literature values there appeared some discrepancies,
but some values agreed with present ones. It is thought that diffusion
through a glass diaphragm cell may not give reliable results for the
hydrogen ion because water structure becomes modified when water moves
through very fine glass capillaries or pores, and this would affect the
abnormal Grotthuss component of mobility.

Item Type: Thesis - PhD
Authors/Creators:Northey, Helen L
Keywords: Hydrogen-ion concentration, Electrolyte solutions
Copyright Holders: The Author
Copyright Information:

Copyright 1973 the author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania. 1975. Bibliography: l. 153-159

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