Reorientation processes and surface phase transitions—III. An investigation of the capacitance characteristics of the Hg/aqueous solution interface in the presence of methylpyridines
✍ Scribed by A. Pappa-Louisi; P. Nikitas; Ph. Andonoglou
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 567 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0013-4686
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✦ Synopsis
Abetrsct-The differential capacity characteristics of an electrified Hg/O.l N Na,SO, aqueous solution interface is studied in the presence of methylpyridines. It is shown that the adsorbed films of 2-and 3-methylpyridines undergo a phase transformation at potentials around -l.OV (see) and at concentrations higher than 0.015 M. The transition region is bounded by needle-like capacitance peaks at negative potentials to -1.1 V (see) and capacitance shoulders in the region between -0.3 and -0.7V (see). An explanation of the shape of the capacitance curves in the coexistence region is attempted in terms of slow irreversible transition processes. At potentials beyond the needle-like peaks, 2-and 3-methylpyridines are desorbed, whereas at potentials less negative than -0.3 V an increase in their adsorption is observed leading to a capacitance adsorption/desorption maximum at positive changes. Under the same conditions the adsorption layer of 4-methylpyrldine doe8 not show any symptoms of a phase transition. The capacitance curves exhibit two adsorption/desorption maximums at extreme polarizations, which bound the adsorption region of this substance.