β Scribed by D. Rolle; J.W. Schultze
No coin nor oath required. For personal study only.
Thermodynamic data for the electrosorption of aromatic molecules at metal electrodes (the electrosorption valency y, surface concentration r, the double layer capacity C,, and the free adsorption enthalpy AC,) are analysed for phenol at mercury as an example. At small r the phenol molecule is adsorbed in a Aat position, but at T > Y& this changes to perpendicular. y is negative and 1 FLI 0.2 for flat orientation, but negligible for the perpendicular one. C, decreases with increasing coverage for both orientations, indicating a dominating thickening of the double layer. From AC, values a small s-bond contribution AC, % 50 kJ mol-' is estimated. The energetic analysis shows that an anodic charge transfer takes place if the electrode potential approaches the oxidation potential e,,and a cathodic charge transfer in the vicinity of s_,,. Charge transfer data for other aromatic and heterocyclic compounds were obtained using the same thermodynamic analysis. In general, the charge transfer is positive, 0 -Z 1 < 0.3. These data can be successfully correlated with the oxidation potential, the ionization potential and the electron density in the ring respectively.
π SIMILAR VOLUMES
The effect of coumarin on the "deposition potential" of a number of metals at solid metal surfaces has been compared with that at a dropping mercury electrode. These results have been used to interpret the adsorption of coumarin on different metal surfaces and to suggest that Tl+ and Pb\*+ ions are
## Abet -The absorption of H&, Tl+, B13+ and Cuz+ at polycrystalbne gold electrodes from aqueous solutions IS mvestigated by potentrostatic step expenme-nts at rotatmg rmgdBk electrodes The macroscoptc partml charge transfer coefiiuent 1 u determmed from the uutud part of the current transients at