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nitrobenzene interface
J. Electroanal. Chem., 190 (1985) 257-260
257
Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands
Short communication ON THE SURFACE AND ZERO CHARGE POTENTIALS AT THE W A T E R / NITROBENZENE INTERFACE *
ZBIGNIEW KOCZOROWSKI
Department of Chemistry, University of Warsaw, ul. L Pasteura 1, 02-093 Warsaw (Poland) (Received 20th December 1984; in revised form 22nd February 1985)
Great progress has been achieved recently in the electrochemistry of immiscible electrolyte solutions. At the same time, some essential and very difficult questions have arisen. Among them a very important one concerns the double-layer structure at a liquid/liquid interface, especially at the water/nitrobenzene interface usually considered to be a model system. The model consisting of two Gouy-Chapman-type diffuse layers separated by an inner layer was developed by Samec et al. [1-3] on the basis of the pioneering works by Vervey and Niessen [4] and by Gross et al. [5]. That approach aroused a serious controversy. Girault and Shiffrin [6] questioned the applicability of the inner layer model by suggesting mixed solvation and interfacial mixing. The simple interpretation of the charge density as a "smeared-out plane" is obscured by those effects as well as by ion pairing [7]. Recently we have found that the capacity of the water/1,2-dichloroethane interface is higher than that calculated from the Gouy-Chapman theory [8]. This is due either to surface charge transfer reactions [9] or to restricted applicability of the Gouy-Chapman theory [6,7] or to both reasons. On the other hand, Silva and Moura [10] concluded from their and other authors' data that the surface charge transfer as suggested in the above papers was doubtful. According to Samec et al. [3] their ideas can be reconciled with those of Girault and Schiffrin [7] " b y considering the boundary between the space-charge region and the inner layer to be diffuse rather than sharp, by analogy with the treatment of the metal/electrolyte interface using the non-local electrostatic approach" [11]. The problems of the double-layer models, of the potential of zero charge and of the structuring of the interface of immiscible electrolyte solutions were discussed at the Heyrovsk~¢ Discussion at Liblice [12] and they may still be considered to be open. It seems that a deal of useful information can be obtained from the analysis and the correlation of the Volta and zero charge potentials. Such a popular treatment used in discussing properties of the metal/solution interfaces was initiated and developed by Frumkin and his school [13,14] and later by Parsons [15] and Trasatti [16,17]. * Presented in part during the Discussions at the XVIIIth Heyrovsk~¢ Discussion, May 1984, Liblice, Czechoslovakia. 0022-0728/85/$03.30
© 1985 Elsevier Sequoia S.A.
258
Our Volta potential measurements for the nitrobenzene/water system yielded the difference of surface potentials of the mutually saturated solvents: X~n - XnW= A'~%X which amounted to 0.10 + 0.01 V [18]. The potential drop AW~wX was found to be considerably lower than the analogous potential difference estimated for pure water and pure nitrobenzene, AWX = Xw - X n = 0.24 + 0.01 V [19]. This means that the presence of water in nitrobenzene and especially of nitrobenzene in water modifies the surface structure of these liquids strongly. The A~X and AW~wX potentials were corrected for the influence of ions [18,19]. One can also say that the Galvani potential at a liquid/liquid interface is composed of dipolar and ionic parts [20]: AW%q~= AW~"wg(dipole)+ AW~wg(ion)
(1)
as it is used with the metal/solution systems [14,15,16,21]. When the interface is in the zero charge state (A~%%~c) then the ionic potential A'~%g(ion) should be zero and, therefore, the Galvani potential should be equal to the dipolar term. The surface potentials defined above can be expected to fulfil the following inequality: A~X > A'~%x > A~%g(dipole)
(2)
and the AW,%g(dipole) term should be very small compared with the potential difference of free surfaces due to equalization of compositions and of orientations of the water and nitrobenzene molecules at the interface of the mutually saturated liquids. The inequality (2) is so far an experimental finding only; no theory has been elaborated hitherto to justify it. It has been confined by the results of the potential of zero charge measurements that the AW~wg(dipole) value is indeed very small. However, the ~w~,~%zc data published hitherto for the water/nitrobenzene interface are markedly different
TABLE 1 Galvani zero charge potentials, A"~n~pzc, at water/nitrobenzene interfaces
1 2 3 4 5 6 7 8 9
Salt composition of system (mol d m - 3)
Aw~rpp~c Method of measurement
in water
in nitrobenzene
/mV
NaBr 3 × 10- 2 + TAABr var. LiCI var. LiCI var. LiCI 10-1 MgC12 5 × 10- 3 LiCI 10-2 LiCI 10- 2 NaBr 3 x 10- 2 + TAABr var. NaBr 10- z
TAATPhB 10- 2 TBATPhB var. TBATPhB var. TBATPhB 10 1 TBATPhB 10- 2 TPhAsTPhB 10-2 TBATPhB 10- 2 TAATPhB 10- z TBATPhB 10- 2
1+ 5 42 (15) 20 ( - 7) 58 27 46 32 0+ 5 0
interfacial tension capacity interfacial tension capacity capacity capacity capacity interfacial tension capacity
Ref.
5 1 (3) 23 (3) 24 2 2 2 22 3
TAABr means tetraalkylammonium bromide; vat., variable concentrations; TAATPhB, tetraalkylammonium tetraphenylborate; TBATPhB, tetrabutylammonium tetraphenylborate; TPhAsTPhB, tetraphenylarsonium tetraphenylborate.
259
(Table 1). They have been obtained by different experimental methods and for different ionic compositions of the aqueous and nitrobenzene phases including both reversible [5,22] and polarizable systems [1-3,23,24]. Apart from possible experimental errors * it seems that many potentials of zero charge are to be expected at such interfaces. They are similar to some metal-solution systems where the free charge and a broad spectrum of total charges should be distinguished [14,25]. The interfaces of immiscible electrolyte solutions are not as intensely polarizable as has been observed for the mercury-aqueous potassium fluoride system. This makes it possible that different potentials of zero charge values be measured depending on compositions, experimental methods and even on the conditions of the experiment. Influences of certain reversible reactions and of specific adsorption seem to be inevitable. The formal information on the structure of a liquid-liquid interface is given by the difference of the A~g(dipole) and AW.~wXvalues which is equal to A'~g(dipole) - AW,"w X = 8Xw" - ~X nw
=
mwn8X
(3)
The terms 8X wn and 8X nw are the modifications forced upon Xwn and X nW, respectively, by bringing the two liquid phases into contact. The surface potential AW~g(dipole) is then created at the formed interface. Probably this term Aw~Bx cannot be separated into components belonging to the phases for interfaces separating two mutually saturated solvents in contrast to the metal/solution system [16,17,21]. The term AWnnAx may be named the mixed dipolar interfacial potential. Generally, it depends not only on the ratio of water and nitrobenzene molecule numbers at the interface and on their orientations; it may also be strongly influenced by large ions, e.g. by those forming tetrabutylammonium tetraphenylborate (BATPhB) usually used as supporting electrolyte in nitrobenzene. Gavach et al. [26] determined the specific adsorption at the water/nitrobenzene interface of tetraalkylammonium bromides partitioned between the two solvents but then Gross et al. [5] deduced that such an effect is absent for tetraalkylammonium tetraphenylborates used as supporting electrolytes in the nitrobenzene phases. The TBA ÷ [18] and TPhB- [19] ions were observed to influence the free surface very strongly, i.e. the Xwn values. It is possible that A~ng(dipole) may be weakly affected by those ions, especially at the commonly used concentrations below 0.05 mol dm-3. The change in solubility of water in nitrobenzene is also rather small at those concentrations [27]. This phenomenon is probably an additional factor influencing the structure of liquid/liquid interfaces. In this context it may be of interest to interpret the experimental fact that the Galvani potential of the water/nitrobenzene system in the presence of tetraethylammonium picrate (TEAPi) partitioned between the two phases is close to zero * E.g. according to Samec et al. [3] a proper correction of the potential of the reference interface reversible with respect to the tetrabutylammonium ion yields the potential of zero charge equal to zero (Table 1: the values in brackets).
260 [20,28,29] o n a c c o u n t of t h e a l m o s t e q u a l i o n i c p a r t i t i o n c o e f f i c i e n t s o f the T E A + a n d P i - i o n s [30]. It m e a n s f o r m a l l y t h a t the V o l t a , Aw~q~°(TEAPi) a n d AW~wX t e r m s s h o u l d c o m p e n s a t e o n e a n o t h e r , T h i s has b e e n c o n f i r m e d e x p e r i m e n t a l l y [19]. Similarly, it results f r o m eqn. (1) t h a t t h e A'~w g ( d i p o l e ) t e r m s h o u l d b e e q u a l to t h e - A ' ~ ] , g ( i o n ) term. H o w e v e r , this c o m p e n s a t i o n m a y result f r o m the s p e c i f i c a d s o r p t i o n effect as well. F u r t h e r i n v e s t i g a t i o n s of t h e i n t e r f a c e s of i m m i s c i b l e e l e c t r o l y t e s o l u t i o n s , b o t h t h e o r e t i c a l a n d e x p e r i m e n t a l , i n c l u d i n g the use o f t h e s t r e a m i n g m e t h o d [31] a n d p e r h a p s o f s p e c t r a l m e t h o d s s h o u l d c o n t r i b u t e to s o l v i n g t h e s e p r o b l e m s . ACKNOWLEDGEMENT T h e a u t h o r wishes to t h a n k P r o f e s s o r S e r g i o T r a s a t t i , U n i v e r s i t y o f M i l a n , for a f r i e n d l y d i s c u s s i o n w h i c h was h e l p f u l in p r e p a r i n g this p a p e r . REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Z. Samec, V. Marerek and D. Homolka, J. Electroanal. Chem., 126 (1981) 121. D. Homolka, P. Hhjkovh and Z. Samec, J. Electroanal. Chem., 159 (1983) 233. Z. Samec, V. Marerek and D. Homolka, Faraday Discuss. Chem. Soc., 77 (1984) Paper 10. E.J.W. Vervey and K.F. Niessen, Philos. Mag., 28 (1939) 435. M. Gros, S. Gromb and C. Gavach, J. Electroanal. Chem., 89 (1978) 29. H.H. Girault and D.J. Schiffrin, J. Electroanal. Chem., 150 (1983) 43. H.H.J. Girault and D.J. Schiffrin in M.J. Allen and P.N.R. Usherwood (Eds.), Charge and Field Effects in Biosystems, Abacus Press, Tunbridge Wells, 1984, p. 171. G. Geblewicz, Z. Figaszewski and Z. Koczorowski, J. Electroanal. Chem., 177 (1984) 1. P. H~jkovh, D. Homolka, V. Marerek and Z. Samec, J. Electroanal. Chem., 151 (1983) 277. F. Silva and C. Moura, J. Electroanal. Chem., 177 (1984) 317. A.A. Kornyshev, W. Schrnickler and M.A. Vorotynsev, Phys. Rev. B, 25 (1982) 5244. XVllIth HeyrovskS¢ Discussion, Liblice, 1984. A.N. Frumkin, Z.A. Jofa and M.A. Gerovich, Zh. Fiz. Khim., 30 (1956) 1455. A.N. Frumkin, O.A. Petrii and B.B. Damaskin in J.O'M. Bockris, B.E. Conway and E. Yeager (Eds.), Comprehensive Treatise of Electrochemistry, Vol. 1, Plenum Press, New York, 1980, p. 221. R. Parsons in J.O'M. Bockris and B.E. Conway (Eds,), Modern Aspects of Electrochemistry, Vol. 1, Butterworths, London, 1954, Ch. 3. S. Trasatti in H. Gerisher and C.W. Tobias, (Eds.), Advances in Electrochemistry and Electrochemical Engineering, Vol. 10, Wiley Interscience, New York, 1976, p. 213. S. Trasatti in J.O'M. Bockris, B.E. Conway and E. Yeager (Eds.), Comprehensive Treatise of Electrochemistry, Vol. 1, Plenum Press, New York, 1980, p. 45. Z. Koczorowski and I. Zagbrska, J. Electroanal. Chem., 159 (1983) 183. I. Zagbrska and Z. Koczorowski, to be published. Z. Koczorowski, J. Electroanal. Chem., 127 (1981) 11. S. Trasatti, J. Electroanal. Chem., 150 (1983) 1. J.D. Reid, O.R. Melroy and R.P. Buck, J. Electroanal. Chem., 147 (1983) 71. T. Kakiuchi and M. Senda, Bull. Chem. Soc. Jpn., 56 (1983) 1322. T. Kakiuchi and M. Senda, Bull. Chem. Soc. Jpn., 56 (1983) 1755. A.N. Frumkin and O.A. Petrii, Electrochim. Acta, 20 (1975) 347. C. Gavach, P. Seta and B. D'Epenoux, J. Electroanal. Chem., 83 (1977) 225. E. Iwamoto, Y. Hiyama and Y. Yamamoto, J. Solution Chem., 6 (1977) 371. Z. Koczorowski and G. Geblewicz, J. Electroanal. Chem., 152 (1983) 55. G. Geblewicz and Z. Koczorowski, J. Electroanal. Chem., 158 (1983) 37. J. Rais, Collect. Czech. Chem. Commun., 36 (1971) 3253. H.H.J. Girault and D.J. Schiffrin, J. Electroanal. Chem., 161 (1983) 415.
257
Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands
Short communication ON THE SURFACE AND ZERO CHARGE POTENTIALS AT THE W A T E R / NITROBENZENE INTERFACE *
ZBIGNIEW KOCZOROWSKI
Department of Chemistry, University of Warsaw, ul. L Pasteura 1, 02-093 Warsaw (Poland) (Received 20th December 1984; in revised form 22nd February 1985)
Great progress has been achieved recently in the electrochemistry of immiscible electrolyte solutions. At the same time, some essential and very difficult questions have arisen. Among them a very important one concerns the double-layer structure at a liquid/liquid interface, especially at the water/nitrobenzene interface usually considered to be a model system. The model consisting of two Gouy-Chapman-type diffuse layers separated by an inner layer was developed by Samec et al. [1-3] on the basis of the pioneering works by Vervey and Niessen [4] and by Gross et al. [5]. That approach aroused a serious controversy. Girault and Shiffrin [6] questioned the applicability of the inner layer model by suggesting mixed solvation and interfacial mixing. The simple interpretation of the charge density as a "smeared-out plane" is obscured by those effects as well as by ion pairing [7]. Recently we have found that the capacity of the water/1,2-dichloroethane interface is higher than that calculated from the Gouy-Chapman theory [8]. This is due either to surface charge transfer reactions [9] or to restricted applicability of the Gouy-Chapman theory [6,7] or to both reasons. On the other hand, Silva and Moura [10] concluded from their and other authors' data that the surface charge transfer as suggested in the above papers was doubtful. According to Samec et al. [3] their ideas can be reconciled with those of Girault and Schiffrin [7] " b y considering the boundary between the space-charge region and the inner layer to be diffuse rather than sharp, by analogy with the treatment of the metal/electrolyte interface using the non-local electrostatic approach" [11]. The problems of the double-layer models, of the potential of zero charge and of the structuring of the interface of immiscible electrolyte solutions were discussed at the Heyrovsk~¢ Discussion at Liblice [12] and they may still be considered to be open. It seems that a deal of useful information can be obtained from the analysis and the correlation of the Volta and zero charge potentials. Such a popular treatment used in discussing properties of the metal/solution interfaces was initiated and developed by Frumkin and his school [13,14] and later by Parsons [15] and Trasatti [16,17]. * Presented in part during the Discussions at the XVIIIth Heyrovsk~¢ Discussion, May 1984, Liblice, Czechoslovakia. 0022-0728/85/$03.30
© 1985 Elsevier Sequoia S.A.
258
Our Volta potential measurements for the nitrobenzene/water system yielded the difference of surface potentials of the mutually saturated solvents: X~n - XnW= A'~%X which amounted to 0.10 + 0.01 V [18]. The potential drop AW~wX was found to be considerably lower than the analogous potential difference estimated for pure water and pure nitrobenzene, AWX = Xw - X n = 0.24 + 0.01 V [19]. This means that the presence of water in nitrobenzene and especially of nitrobenzene in water modifies the surface structure of these liquids strongly. The A~X and AW~wX potentials were corrected for the influence of ions [18,19]. One can also say that the Galvani potential at a liquid/liquid interface is composed of dipolar and ionic parts [20]: AW%q~= AW~"wg(dipole)+ AW~wg(ion)
(1)
as it is used with the metal/solution systems [14,15,16,21]. When the interface is in the zero charge state (A~%%~c) then the ionic potential A'~%g(ion) should be zero and, therefore, the Galvani potential should be equal to the dipolar term. The surface potentials defined above can be expected to fulfil the following inequality: A~X > A'~%x > A~%g(dipole)
(2)
and the AW,%g(dipole) term should be very small compared with the potential difference of free surfaces due to equalization of compositions and of orientations of the water and nitrobenzene molecules at the interface of the mutually saturated liquids. The inequality (2) is so far an experimental finding only; no theory has been elaborated hitherto to justify it. It has been confined by the results of the potential of zero charge measurements that the AW~wg(dipole) value is indeed very small. However, the ~w~,~%zc data published hitherto for the water/nitrobenzene interface are markedly different
TABLE 1 Galvani zero charge potentials, A"~n~pzc, at water/nitrobenzene interfaces
1 2 3 4 5 6 7 8 9
Salt composition of system (mol d m - 3)
Aw~rpp~c Method of measurement
in water
in nitrobenzene
/mV
NaBr 3 × 10- 2 + TAABr var. LiCI var. LiCI var. LiCI 10-1 MgC12 5 × 10- 3 LiCI 10-2 LiCI 10- 2 NaBr 3 x 10- 2 + TAABr var. NaBr 10- z
TAATPhB 10- 2 TBATPhB var. TBATPhB var. TBATPhB 10 1 TBATPhB 10- 2 TPhAsTPhB 10-2 TBATPhB 10- 2 TAATPhB 10- z TBATPhB 10- 2
1+ 5 42 (15) 20 ( - 7) 58 27 46 32 0+ 5 0
interfacial tension capacity interfacial tension capacity capacity capacity capacity interfacial tension capacity
Ref.
5 1 (3) 23 (3) 24 2 2 2 22 3
TAABr means tetraalkylammonium bromide; vat., variable concentrations; TAATPhB, tetraalkylammonium tetraphenylborate; TBATPhB, tetrabutylammonium tetraphenylborate; TPhAsTPhB, tetraphenylarsonium tetraphenylborate.
259
(Table 1). They have been obtained by different experimental methods and for different ionic compositions of the aqueous and nitrobenzene phases including both reversible [5,22] and polarizable systems [1-3,23,24]. Apart from possible experimental errors * it seems that many potentials of zero charge are to be expected at such interfaces. They are similar to some metal-solution systems where the free charge and a broad spectrum of total charges should be distinguished [14,25]. The interfaces of immiscible electrolyte solutions are not as intensely polarizable as has been observed for the mercury-aqueous potassium fluoride system. This makes it possible that different potentials of zero charge values be measured depending on compositions, experimental methods and even on the conditions of the experiment. Influences of certain reversible reactions and of specific adsorption seem to be inevitable. The formal information on the structure of a liquid-liquid interface is given by the difference of the A~g(dipole) and AW.~wXvalues which is equal to A'~g(dipole) - AW,"w X = 8Xw" - ~X nw
=
mwn8X
(3)
The terms 8X wn and 8X nw are the modifications forced upon Xwn and X nW, respectively, by bringing the two liquid phases into contact. The surface potential AW~g(dipole) is then created at the formed interface. Probably this term Aw~Bx cannot be separated into components belonging to the phases for interfaces separating two mutually saturated solvents in contrast to the metal/solution system [16,17,21]. The term AWnnAx may be named the mixed dipolar interfacial potential. Generally, it depends not only on the ratio of water and nitrobenzene molecule numbers at the interface and on their orientations; it may also be strongly influenced by large ions, e.g. by those forming tetrabutylammonium tetraphenylborate (BATPhB) usually used as supporting electrolyte in nitrobenzene. Gavach et al. [26] determined the specific adsorption at the water/nitrobenzene interface of tetraalkylammonium bromides partitioned between the two solvents but then Gross et al. [5] deduced that such an effect is absent for tetraalkylammonium tetraphenylborates used as supporting electrolytes in the nitrobenzene phases. The TBA ÷ [18] and TPhB- [19] ions were observed to influence the free surface very strongly, i.e. the Xwn values. It is possible that A~ng(dipole) may be weakly affected by those ions, especially at the commonly used concentrations below 0.05 mol dm-3. The change in solubility of water in nitrobenzene is also rather small at those concentrations [27]. This phenomenon is probably an additional factor influencing the structure of liquid/liquid interfaces. In this context it may be of interest to interpret the experimental fact that the Galvani potential of the water/nitrobenzene system in the presence of tetraethylammonium picrate (TEAPi) partitioned between the two phases is close to zero * E.g. according to Samec et al. [3] a proper correction of the potential of the reference interface reversible with respect to the tetrabutylammonium ion yields the potential of zero charge equal to zero (Table 1: the values in brackets).
260 [20,28,29] o n a c c o u n t of t h e a l m o s t e q u a l i o n i c p a r t i t i o n c o e f f i c i e n t s o f the T E A + a n d P i - i o n s [30]. It m e a n s f o r m a l l y t h a t the V o l t a , Aw~q~°(TEAPi) a n d AW~wX t e r m s s h o u l d c o m p e n s a t e o n e a n o t h e r , T h i s has b e e n c o n f i r m e d e x p e r i m e n t a l l y [19]. Similarly, it results f r o m eqn. (1) t h a t t h e A'~w g ( d i p o l e ) t e r m s h o u l d b e e q u a l to t h e - A ' ~ ] , g ( i o n ) term. H o w e v e r , this c o m p e n s a t i o n m a y result f r o m the s p e c i f i c a d s o r p t i o n effect as well. F u r t h e r i n v e s t i g a t i o n s of t h e i n t e r f a c e s of i m m i s c i b l e e l e c t r o l y t e s o l u t i o n s , b o t h t h e o r e t i c a l a n d e x p e r i m e n t a l , i n c l u d i n g the use o f t h e s t r e a m i n g m e t h o d [31] a n d p e r h a p s o f s p e c t r a l m e t h o d s s h o u l d c o n t r i b u t e to s o l v i n g t h e s e p r o b l e m s . ACKNOWLEDGEMENT T h e a u t h o r wishes to t h a n k P r o f e s s o r S e r g i o T r a s a t t i , U n i v e r s i t y o f M i l a n , for a f r i e n d l y d i s c u s s i o n w h i c h was h e l p f u l in p r e p a r i n g this p a p e r . REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Z. Samec, V. Marerek and D. Homolka, J. Electroanal. Chem., 126 (1981) 121. D. Homolka, P. Hhjkovh and Z. Samec, J. Electroanal. Chem., 159 (1983) 233. Z. Samec, V. Marerek and D. Homolka, Faraday Discuss. Chem. Soc., 77 (1984) Paper 10. E.J.W. Vervey and K.F. Niessen, Philos. Mag., 28 (1939) 435. M. Gros, S. Gromb and C. Gavach, J. Electroanal. Chem., 89 (1978) 29. H.H. Girault and D.J. Schiffrin, J. Electroanal. Chem., 150 (1983) 43. H.H.J. Girault and D.J. Schiffrin in M.J. Allen and P.N.R. Usherwood (Eds.), Charge and Field Effects in Biosystems, Abacus Press, Tunbridge Wells, 1984, p. 171. G. Geblewicz, Z. Figaszewski and Z. Koczorowski, J. Electroanal. Chem., 177 (1984) 1. P. H~jkovh, D. Homolka, V. Marerek and Z. Samec, J. Electroanal. Chem., 151 (1983) 277. F. Silva and C. Moura, J. Electroanal. Chem., 177 (1984) 317. A.A. Kornyshev, W. Schrnickler and M.A. Vorotynsev, Phys. Rev. B, 25 (1982) 5244. XVllIth HeyrovskS¢ Discussion, Liblice, 1984. A.N. Frumkin, Z.A. Jofa and M.A. Gerovich, Zh. Fiz. Khim., 30 (1956) 1455. A.N. Frumkin, O.A. Petrii and B.B. Damaskin in J.O'M. Bockris, B.E. Conway and E. Yeager (Eds.), Comprehensive Treatise of Electrochemistry, Vol. 1, Plenum Press, New York, 1980, p. 221. R. Parsons in J.O'M. Bockris and B.E. Conway (Eds,), Modern Aspects of Electrochemistry, Vol. 1, Butterworths, London, 1954, Ch. 3. S. Trasatti in H. Gerisher and C.W. Tobias, (Eds.), Advances in Electrochemistry and Electrochemical Engineering, Vol. 10, Wiley Interscience, New York, 1976, p. 213. S. Trasatti in J.O'M. Bockris, B.E. Conway and E. Yeager (Eds.), Comprehensive Treatise of Electrochemistry, Vol. 1, Plenum Press, New York, 1980, p. 45. Z. Koczorowski and I. Zagbrska, J. Electroanal. Chem., 159 (1983) 183. I. Zagbrska and Z. Koczorowski, to be published. Z. Koczorowski, J. Electroanal. Chem., 127 (1981) 11. S. Trasatti, J. Electroanal. Chem., 150 (1983) 1. J.D. Reid, O.R. Melroy and R.P. Buck, J. Electroanal. Chem., 147 (1983) 71. T. Kakiuchi and M. Senda, Bull. Chem. Soc. Jpn., 56 (1983) 1322. T. Kakiuchi and M. Senda, Bull. Chem. Soc. Jpn., 56 (1983) 1755. A.N. Frumkin and O.A. Petrii, Electrochim. Acta, 20 (1975) 347. C. Gavach, P. Seta and B. D'Epenoux, J. Electroanal. Chem., 83 (1977) 225. E. Iwamoto, Y. Hiyama and Y. Yamamoto, J. Solution Chem., 6 (1977) 371. Z. Koczorowski and G. Geblewicz, J. Electroanal. Chem., 152 (1983) 55. G. Geblewicz and Z. Koczorowski, J. Electroanal. Chem., 158 (1983) 37. J. Rais, Collect. Czech. Chem. Commun., 36 (1971) 3253. H.H.J. Girault and D.J. Schiffrin, J. Electroanal. Chem., 161 (1983) 415.