(289) Stanford, G. S., Nucl. Instr. and Methods 34, 1 (1965). (290) Starik, I. E., “Principles of Radiochemistry,” The Publishing House of the Academy of Sciences, MoscowLeningrad, 1959. (291) Stary, J., Ruaicka, J., Zeman, A., Anal. Chim. Acta 29. 103 (1963). (292) Stary, J., Ruzicka, J., Zeman, A., Talanta 11. 481 (1964). (293) Steele, E., L., in “Modern Trends in Activation Analysis,” proceedings of 1965 International Conference, College Station, Texas, 1966. (294) Steim, J. &Benson, I., A. A., Anal. Bzochem. 9, 21 (1964). (295) Strain, J. E., Ross, W. J., Rept. ORNL-3672 (1965). (296) Suzuki, N., Kudo, K., Anal. Chim. Acta 32,456 (1965). (297) Tadmor, J., ANAL.CHEM.36, 1565 (1964). (298) Tanielian, C., Coche, A., Deluzarche, A,, Laustriat, G,, Maillard, A., Intern. J . A p p l . Radiation Isotopes 15, 11 (1964). (299) Ibid., p. 17. (300) Tavendale, A. J., IEEE, Trans. Xucl. Sci. NS-12, 255 (1965). (301) Tavendale, A. J., Ewan, G. T., Nucl. Instr. Methods 25, 185 (1963). (302) Taylor, D., “Neutron Irradiation and Activation Analysls,” George Newnes Ltd., London, 1964.
(303) Tilbury, R. S., Wahl, W. H., Nucleonics 23, No. 9, 70 (1965). (304) Toelgyessy, J., Jesenak, V., Braun, T., Vienna, International Atomic Energy Agency, Preprint SM-55/107 (1964). (305) Tosch, W. C., AXAL.CHEW37, 958 (1965). (306) “Tracers in Analysis,” Isotopes Radiation Technol. 1, 293 (1964). (307) Vaninbroukx. R.. Soernol. A.. Intern. J . A p p l . ’RadiationAIsotopes 16; 289 (196.5). (3087 Verheijke, 11. L., Intern. J . A4ppl. Radiation Isotopes 15, 559 (1964). (309) Wahlgren, >I., Wing, J., Hines, J., in ‘‘Modern Trends in Activation Analysis,” Proceedings of 1965 International Conference, College Station, Texas, 1966. (310) Wainerdi, R. E., Fite, L. E., Gibbons, D., Sickins, W.W.,Jimenez, P., Drew, D., in “Radiochemical Methods of Analysis,” p. 149, Vol. 11, Proceedings of SvmDosium. Salzbure. October 1923, i96h, Intern. At. Energy Agency, Salzburg, 1965. (311) Wangermann, G., Atomkernenergie 9 , 187 (1964). (312) “The Warren Report,” p. 237, Associated Press, New York, 1964. (313) Watt, D. E., Ramsden, D., “High Sensitivity Counting Techniques,” The Machlillan Co., New York, 1964. (314) Way, K., Nuclear Data Sheets, N.A.S.-N.R.C., Washington, I).C. ~
(315) Weisz, H., Klockow, D., Mikrochim. Ichnoanal. Acta, No. 5-6, 1082 (1963). (316) Wester, P. O., Brune, D., Samsahl, K., Intern. J . A p p l . Radiation Isotopes 15, 59 (1964). (317) Wiesner, L., Atomwirtschaft 10, 131 (1965). (318) Wood, D. E., Pasztor, L. C., in “Modern Trends in Activation Analysis,” Proceedings of 1965 International Conference, College Station, Texas, 1966. (319) Wyttenbach, A., Seue Tech. 7, 85 (1965). (320) Yule, H. P., ANAL. CHEM.37, 129 (1965). (321) Yule, H. P., Guinn, V. P., in “Radiochemical Methods of Analysis,” p. ,111, 5‘01. 11, Proceedings of Symposium, Salzburg, October 19-23, 1964, Intern. At. Energy Agency, Salaburg, 1965. (322) Yule, H. P., Lukens, H. R., Guinn, V. P., AVucl. Instr. Methods 33, 277 (1965). (323) Zeman, A., Stary, J., Ruzicka, J., Talanta 10. 981 (1963). (324) Zhurav’lev, T’. F.,’M e d . Radiol. 9, No. 12, 63 (1964). (325) Zoller, L. K., National Aeronautics and Space Administration, Rept. N6316439 (1962). Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation.
Polarographic Theory, Instrumentation, and Methodology David N. Hurne, Massachusetts Institute of Technology, Cambridge, Mass.
T
review summarizes the literature in the period November 1963 through December 1965 and follows very closely the pattern and organization of the previous review (97). I n 1964 the subject was divided, and papers on newer electroanalytical techniques which could be considered polarographic only by adopting a very broad definition of the term-electrode processes, electrode kinet>ics, and many aspects of electrochemical theory-were treated in a separate review by W. H. Reinmuth (180). This approach showed many advantages and is continued in the present set of reviews. As usual, no attempt is made to discuss papers on applications unless they embody new developments in theory, instrunientation or methodology, or unless they suggest a novel type of approach. Those wishing complete coverage of the polarographic literature are advised to follow the excellent continuing bibliographies founded by Heyrovsky (90, 91) and Semerano (26). These not only give comprehensive lists of publications but also list many theses and papers given at scientific meetings. The number of papers appearing annually continues to grow and the problem of keeping u p grows with it. HE PRESENT
02 139
Hallett (85) has given an account of an ambitious program undertaken by the Polarographic Society of Japan which may simplify matters somewhat. -4bstracts and essential data and figures are being printed on cards (marked to be punched according to the user’s own data retrieval system) starting with the year 1961 and working backwards and forwards. The cards will be available on a subscription basis like a n abstract journal. A number of useful review articles have appeared during the biennium. Muller (152) has surveyed the development of polarography and polarographic instrumentation, Zuman (249) the applications of classical polarography, particularly organic polarography, and Taylor (222) analytical applications. The Heyrovski Honour Issue of Talanta issued in December 1965 (220) consisted of seventeen informative reviews on various aspects of polarography, making the issue an excellent general survey of special topics in the field. A number of the reviews in this issue are cited under their particular topics below. Among the books which have appeared the new edition of Lleites’ wellknown “Polarographic Techniques” (145) is especially welcome. The pro-
ceedings of the first Australian conference on electrochemistry in 1963 (174) contain many interesting papers, particularly on alternating current polarography, and Zunian’s new book (860) gives a good treatment of organic polarographic analysis. Standardization of nomenclature definitions and symbols is always a difficult matter and groups both in C I T C E and IUPAC have been at work on the problem. Reports making suggestions for nomenclature, definitions, and sgmbols in electrochemistry have been issued by these groups for study and discussion ( 5 6 , 5 6 , 2 3 1 ) . CLASSICAL POLAROGRAPHY
Instruments a n d Apparatus. Beckm a n Instruments has entered t h e polarographic field with t h e introduction of a remarkably versatile electroanalytical instrument, t h e Electroscan 30, which has capability not only for ordinary polarography b u t according t o its maker a t least 14 other electroanalytical techniques. These include three-electrode potentiostatic polarography, inverse polarography, alternating current polarography, rapid scan voltammetry, chronoamperometry, and VOL. 38, NO. 5, APRIL 1966
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chronopotentioinetry. The Heath Co. now offers the Rlalmstadt-Enke controlled potential polarograph system, consisting of t'he Heath polarographic module together with an operational amplifier control module and a servochart recorder. It is directly applicable to conventional, three-electrode, cyclic, alternating current, ' and oscillographic polarography. The Electrochem Co. of Olympia, Wash., offers a simple device, L'Ahto-Scan,''which serves the purpose of an automatic voltage scanning polarograph (without recorder) a t a very modest cost. Skaltveit and Jehring (198) describe a commercially available East German polarograph, the GWP563, which is suitable for direct current and alternating current polarography. Metrinpes of 13udapest manufactures a pen-recording controlled-potentia1 polarograph and AOIP Nesures of Paris supply a pen recording polarograph of conventional design. Muller (153) describes a variet'y of the electroanalytical instruments made in France, some of which seem not to have commercial ,hierican equivalents. A number of workers described research instruments not commercially available. Parry and Osteryoung (166) describe an electronic, potentiostatic, three-elect,rode polarograph suitable for normal polarography, chronoamperonietry, and pulse and derivative polarography. I>urst et al. (66) give the circuit charaeteristics of a simple electronicscan, controlled-potential polarograph which is much simpler and less espensive than most because it is designed specifically for direct. current polarography rather than for a wide variety of electroanalytical techniques. Harper et al. (87) have built a transistorized threeelectrode recording polarograph based on the principle of Peizker (169) and utilizing a photoelectric compensator. Booman and Holbrook (32) discuss the selection of optimum stability networks for pot,entiostats with particular application to polarographs using transistorized operational amplifiers. Will (239) gives details on a,n electronic device for producing triangular pulses and ramps for voltage sweep methods as well as square pulses and steps for other analytical applicat'ions. Alden et al. (4) have developed operational amplifier circuitry for controlledpotential cyclic vokanimetry, and N a n n (139) has developed an instrument for cyclic voltammetry involving electronic direct current coupled switching. Rabuzin and Pravdiit (178) make use of a n electronic commutator for cyclic chronopotentiometry n-hich obviously is capable of more general application. Breiter (36)has undertaken to automate many of the steps involved in measuring and processing voltammetric data. His apparatus measures current-potential 262 R
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curves and the ohmic and capacitative components of the electrode-solution interface by voltammetry with superimposed alternating current. Xnalogto-digital recording equipment converts the data to punched tape, and three computer programs for processing data are described. It is claimed that the time involved in such studies is cut 90% by this means. Sancollas and Vincent (164) use a self-timing bridge method for measurement of double-layer capacity a t specified times during the life of a drop. -laker (1) has given a n informative discussion of how potentiometer recorder characteristics affect analytical results. The matters of dynamic accuracy, linearity, and interference rejection are considered. Many chemists accept the alleged accuracy of potentiometer recorders a t face value and in view of the ever-increasing percentage of our data which comes to us through the agency of the recording potentiometer, it is worthwhile to give some thought to what the limitations of these devices might be. Miller et al. (160) report the design and performance of a simple manual polarograph of essentially conventional design for which they claim extremely high sensitivities. Polarograms are shown for cadmium and zinc solutions said to be 10-10Jf. The reviewer confesses that he is unable to reconcile the sensitivity claimed with the characteristics quoted for the galvanometer, nor is he able to see how the authors could make valid measurements at such an estreme ratio of capacitative to faradaic currents. Rsbaen (175-1 77) has continued to study the characteristics of the Teflon dropping mercury electrode and has described a Kel-F, Teflon salt bridge for hydrofluoric acid media. The Teflon dropping electrode appears to have the same characteristics as a glass dropping mercury electrode and has given good performance in hydrofluoric acid of concentrationo as high as 1251. Smoler (201) has summarized the advantages of using a capillary inclined a t 45' to the vertical: namely, the elimination of depletion effects, close approsimation to the equations for diffusion currents governed by spherical diffusion, and removal of reaction products such as precipitates or evolved gases. RIetzl and skvitik (146) have devised an improved drop-time control device consisting of a moving coil attached to the capillary and in the field of a larger coil. It can be used as a drop detacher or to make a vibrating dropping electrode, and has the advantages of low inertial mass which permits vibration a t frequencies at hundreds of cycles per second, of being noiseless because there are no metal parts striking one another, and of being easily synchronized with sweep
voltage in rapid-scan or oscilloscopic polarography. It would seem difficult by now to conceive of something new in the design of polarographic cells but new designs continue to appear every year. I n the present period, a cell particularly adapted to serial analyqes (121) and a compact cell with a permanent external reference electrode and having unusually low resistance are described (108). Also reported are a type designed to permit complete and convenient deaeration of the solution n i t h minimum Contamination (241j , a three-compartment cell to minimize ZR errors (49), and one cell for the determination of trace water and active hydrogen compound? in phenyl phosphoi ic dichloride (83). Arthur describes apparatus for removing oyygen from nitrogen with chromous solutions (10). Belew and Raaen (22) shoiv data pointing out the large error in half-wave potential which is possible with improper choice of salt bridge. Giner (76) has suggested the use of a cathodically polarized, platinized platinum hydrogen electrode as a practical reference electrode in polarography. -4lthough it is not intended to compete with classical reference electrodes for applications involving the highest accuracy, it is said to be good to 1 or 2 mv. Others (11) have suggested the use of a long molybdenum wire as an anode in polarography, especially for cathode ray polarography in nonaqueous systems. S o data are available, however, to permit a genuine evaluation of the suggestion. Hayes et al. (88) describe an alternating current technique capable of automatic measurement of drop time to within = t O . O l qecond. It is comforting to learn that some of our apparatus does not deteriorate with time. Vosburg and Bates (235) studied the stability of the modified Keston standard cell, following the characteridics of a number over long periods of time, and reported that they showed only 10- to 20-pv. change on the average in a period of 26 years, even though most were not kept a t a constant temperature and some were eytensively uqed. Half-Wave Potentials. Vandenborgh and Sellers (193, 194, 230) have made studies of the effect of ionic potential, strength on half-wave particularly in concentrated salt media, and have developed an equation which fits experimental data satisfactorily. As would be expected, both the activity coefficient of the electrolyte and the activity of the water are important variables. Kirchmayr (120) finds that the half-ware potential of the reduction of a metal ion to the metal depends on the structure of the amalgam formed, that is to say the surface activity on deposited metal or mercury-metal com-
pound as well as on the activity of the mercury itself. The dependence of potential of cells on the dielectric constant of the medium has been studied by Amis (6) who observes that the potential of many cells is linear with the reciprocal of the dielectric constant, and advances a theory to account for this. Mairanovskii (134) has given a theoretical treatment which considers the effect of adsorption of the components of a reaction taking place a t the electrode. H e has found a set of equations which accounts for changes in the potential of the electrode, both from the rate of electron transfer and the adsorption of reacting components. The effect on the polarographic wave is considered in terms of a simultaneous surface kinetic wave, which he describes as a "quasi-diffusion surface wave," and he suggests that the phenomenon is actually fairly common. Boddy (31)has reviexed the structure of semiconductor-electrolyte interfaces. Butler and Kaye (42) have studied the effect of absence of excess of complexing agent on the polarographic wave in the reduction of complex ions, and HBla (84) has reviewed the literature on the polarographic determination of stability constants of complexes. CURRESTB. Turnham (227) has made a careful study of the extended Ilkovic' equations, determining the coefficient of D1/2 in the Lingane-Loveridge equa_tion and the exponent of t in the Ilkovic equation, by measureinents made during the last 2 seconds of a 15second drop period using niotion picture photography. Previous work on the subject is revieived and the values obtained were found to dellend on the ions involved and the supporting electrolyte. Turnhain lat,er examined polarographic diffusion coefficients of simple cations in various electrolytes, calculated for infinite dilution under polarographic conditions. H e concluded that the Kernst equation using ionic mobilities gives accurate values of polarographic diffusion coefficients at' infinite dilution if the correct value of A is used in the Matsuda equation for diffusion currents (228). Wolf ($42) found a fit to the extended Ilkovii: equation for t'he dependence of current on time at a rapidly dropping electrode where the drop time was controlled by mechanical detachment. Fleming and Berg (69),using very thinwalled capillaries, were unable to eliminate depletion effects completely. They concluded that' an ideal vertical dropping mercury electrode seems impossible to attain, although it is possible to eliminate for all practical purposes depletion effects by use of the Smoler (201) electrode. Kheifets (116) has suggested plotting the logarithm of current us. logarithm of mercury height to zvoid some of the difficulties in determining the dependence of limiting current on mercury height when the
range of heights measured is small. Kheifets suggests that a log plot is more readily amenable to interpretation after least squares fitting than the usual graphical examination of i as a function of h , or D e Levie (69) has studied the socalled capillary response of a dropping mercury electrode and finds that the film of solution, including occasional pockets of solution which are often observed in the lower part of the capillary, is the principal locus of shielding, and he gives a model which represents the electrical charact'eristics of this solution film. The principal concern is with measurement of the double-layer capacity and a graphical method is given for obtaining the corrected value. De Levie has also considered t'he phenomenon of uneven current density distribution on the surface of dropping electrodes and has pointed out the complications which arise from eccentric drop growth. The uneven potential distribution on the drop should be taken into consideration in the derivation of the Ilkovi; equation, and De Levie suggests that the phenomenon has a relation to the production of maxima of the first kind (60). Arinstrong et ul. (9) have used an oscilloscopic technique to d u d y the well known, irregularly shaped waves formed by anodic polarization of the dropping mercury electrode in the presence of electrolytes which form insoluble mercurous salts. They suggest that an analysis of the impedance effects during an electrode reaction permits determination of the nature of the surface process. Zhdanov and &lev (246) have studied the forination of inereuric sulfide films on the dropping electrode in some detail and claim that certain of the peaks observed on the anodic wave correspond to completion of multiples of niononiolecular layers of mercuric sulfide. A single monomolecular layer corresponds to an average change of about 20-mv. ohmic drop, and the number of layers formed is proportional to the polarizing voltage. They point out that the resistance of such films should be taken into account when measuring electrocapillary curves. The problem of iR compensation in high resist'ance systems has been studied by Schaap and NcKinney (189, 190) in two important papers. They first pointed out that a three-electrode polarographic system does not necessarily compensate for solution resistance in all cases, and they developed methods utilizing derivative polarography for the measurement' and evaluation of uncompensated resistance in polarographic cells. They then went on t o apply these techniques, both to a low dielectric constant, high resistance system (n-butylamine) and to high current density aqueous systems, showing that serious errors due to iR drop could be intro-
v'K
duced even with three-electrode systems. The placement of the orifice of the reference electrode with respect to the dropping electrode is of particular importance. It was pointed out that the usual polarographic criteria were not sufficient to show the adequacy of performance of automatic resistance coinpensation in many systems. K6mec (157) has also discussed the effectiveness of ohmic potential drop compensation in controlled-potentia1 polarography, and like Schaap and McKinney he recommends the method of extrapolation to zero limiting current for determination of resistance-free halfwave potentials. Powell and Reynolds (173) suggest the use of a load-line method for interpreting ohmic effects in electrochemistry; this is a graphical technique taken from electronic technology, applicable to resistance in a polarographic cell described in terms of an equivalent circuit. Applications are suggested in ordinary polarography and chronoamperometry. The general principles of iR correction are discussed. ADSORPTIOX EFFECTS.The influence of adsorption a t the dropping electrode has attracted inore interest than ever before. A general review of the significance of adsorption in polarography has been given by I h t e n i n g and Holleek (113). Parsons had developed the theory of adsorption on electrode.; and feels that it is best described in ternis of isotherms a t constant charge (167). Fruinkin (74) and Daniaskin (62) h a r e taken issue with Parsons, claiming that his objections l o the use of the Langinuir isotherm are unjustified, and that potential rather than charge should he the electrical variable in the study of ad+orption isotherms, to n-hich criticism Parsons (168) has replied. lIeibuhr (144) uses electrocapillary curve.; for the dropping elect'rode to determine the extent of adsorption of organic substances. Volke and Ainer (234) have compared the suitability of various methods for determining adsorption in polarographic processes, and concluded that only alternating current polarography and electrocapillary curves are of general applicability for diagnostic purposes. Electrocapillary curves have the disadvantages of poor reproducibility and great sensitivity to capillary positioning. Laitinen and Chambers (130) pointed out both the usefulness and the limitations of chronopotentionietry for the study of adsorption on electrodes, and Uroinan and Murray (38) have utilized chronopotentioinetry to s t d y the adsorption of phenylmercuric ions a t the dropping mercury electrode in connection with the premave shown in the reduction of this substance. I n this instance, it is adsorption of the reactant rather than the product which governs the appearance of the prewave, which indicates that care is needed in applying classical UrdiEka VOL. 38, NO. 5 , APRIL 1966
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approach in interpreting prewaves. The appearance of adsorption waves in irreversible polarographic and chronopotentiometric processes can be governed largely by the rate of adsorption on surface orientation. Kdta and Weber (126) have observed simultaneous effects due to the steric properties of adsorbed molecules inhibiting electrode reactions, while adsorption of species opposite in charge from the depolarizer alters the p s i potential in such a way as to accelerate the electrode reaction. Miller (151) has developed the theory for the effect of adsorbed polyelectrolyt’es on polarographic currents, and with Frei (71) determined experimentally the effect of positively charged polyelectrolytes on cationic depolarizers. Silvestroni and Rampazzo (197) likewise studied the effect of interactions between unreducible adsorbed substances and electrode depolarizers and find agreement between theoretical and observed values. Sathyanarayana (187) has investigated the inhibitory effects of adsorbed n-butanol on the electroreduction of several metal cations, both by classical polarography arid by differential capacity measurements. Jeftib and Branica (203) studying the influence of surface active agent’s on the square wave polarography of uranium found that, the use of the concept of the adsorbed layer as an absorption sieve of the surface of the drop permitted them to develop a means of calculating the stability constants of the uranyl acetylacetono complexes in aqueous solution. The reduction peak of each species on the square wave polarogram was specifically affected. Jehring (104-6) has studied the effect of adsorption on alternating current polarography. Hurwitz (100) discusses theoretically the direct determination of surface excess of specifically adsorbed ions on mercury. Closely connected with adsorption phenomena is the matter of polarographic maxima and their suppression. Abrao (2) recommends the use of Separan as a maximum suppressor. Similar to gelatin in its behavior, Separan suppresses many maxima of metal ions over a wide range of potentials and acidities. I t is stable and has the attractive feature of causing no change in diffusion current. even in concentrations as high as 1%. hlalik and Chand (135) recommend the use of a lauric acid diethanolamine condensate (LDC) for maxima difficult to suppress. I t has the disadvantage of lowering diffusion currents and even suppressing waves completely in large excess, but compared with anionic and cationic detergents a t the same molar concentration it tends to be more efficient. Jacobsen and Kalland (102) have examined cationic and anionic surfactants as maximum suppressors for copper and iron complexes. Charact’eristically, the 264 R
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polarogranis are unaffected when the adsorbed layer has a charge opposite to the depolarizer, but when the charge is the same, the waves are shifted in a negative direction, or greatly distorted. Sathyanarayana (186) has studied the polarographic maxima of cadmium and copper a t the dropping electrode in the presence of camphor. The maxima seem neither to be of the first nor the second kind, and he attributes some of the effects to slow and nonuniform adsorption of surface-active substances a t their desorption points. Sarayan (156) finds that a superimposed alternating current will suppress some maxima, an observation which he attributes to disorientation of the water dipoles of the surface preventing streaming. Okinaka et al. (163) observe maxima on anodic waves a t dropping amalgam electrodes. These can usually be wpprebqed with maximum suppressors, but the Spuleffekt (the stirring within the electrode due to flow of amalgam into the drop) exists even in the presence of maximum suppressors. Bezuglyi and Saliichuk (25), noting that the effectiveness of polyvinyl alcohol in suppressing maxima of the second kind in copper waves was dependent on the degree of polynierization of the polyvinyl alcohol, developed an ingenious method for determination of PVA molecular weight based on this principle. The graph they show indicates applicability from monomer up to molecular weights of around 100,000. METHODOLOGY
Alternating Current Polarography. Hung and Smith (99) have investigated the dependence of alternating current waves on drop time. Originally predictions said that this effect mould be unimportant but later Natsuda (143) suggested that drop time might be significant. Del Mastro and Smith (61) have verified experimentally that the rate of growth and geometric characteriqticb of the drop can be important particularly with qua-i-reversible systems. Aylward and Hayes (14) independently examined the same problem with similar results. They have concluded that there will be significant dependence on drop time whenever a form of inass transfer other than, or in addition to, diffusion is in operation. Tuer and Zaretskii (225) described the phase angle technique in alternating current polarography and mentioned an automatic apparatus, based on phase angle measurements, which they apply to contiol analysis. Tsfarman and Salikhdzhanova (224) have studied the effects of various factors on sensitivity and resolution I\ hen a stationary mercury drop is used in phaqe-sensitive alternating current polarography. Hayes and Reilley (89) describe an operational amplifier alter-
nating current polarograph with admittance recording. They recommend avoiding tuned amplifiers and accomplish phase selection by multiplication of current and voltage signals by electronic multipliers. Hayes et al. ( 8 8 ) )using a conventional operational amplifier a x . polarograph which had been altered slightly to provide a triggering signal for a counter at the fall of each drop, were able to reproduce drop time measurements to hO.01 second. Kowalski and Srzednicki (123) described a device for coupling a sine wave generator to a polarograph for double-layer capacity measurements. Underkofler and Shain (929) have studied alternating current polarography at stationary electrodes and applied the technique using phase sensitive detection to anodic stripping analysis with a considerable increase in sensitivity over that obtained with direct current stripping. LaforgueKantzer and Muxart (129) have observed interesting resonance phenomena connected with alternating current polarography. They observed a mechanical resonance in the drop which is due, they feel, to the periodicity of surface tension with the alternating current and which causes premature detachment of the drop. The phenomenon has bearing on measurements of double-layer impedance and the accuracy of oscilloscopic polarography. They have suggested also t’hepresence of a second type of resonance, a “veritable r6sonance avec l’blectrolyte” of unknown cause. Gupta and Chatterjee (80) have introduced summit-potentials in place of half-wave potentials into the Kolthoff and Lingane equation for the reduction wave of a complex ion, and have shown the equation to be suitable for determining the ligand number and stability constant of the cadmium ammonia complex. They have claimed various advantages such as greater reproducibility-which might be open to question-and that there is no need to analyze the waves for reversibility because only reversible waves give alternating current polarograms. This recommendation is based on the unfortunate implicit assumption that all reductions are either completely reversible or completely irreversible, and could lead to fairly misleading results in the large gray area of partial reversibility, which is occupied by so many real reactions. Gupta, Chat’terjee, and Sharma (81) have applied alternating current polarography and tensammetry to nonaqueous systems. They report lower base currents in methanol than in aqueoui solutions and higher sensitivities with virtual absence of tensammetric peaks. Jehring (104-6) has studied the effects of adsorption of inhibiting agents, such as 1-butanol, on alternating current waves and examined the influence of
mercury flow rate on the adsorption equilibria involved. Gupta and Sharma (82) have made similar studies with amyl alcohol. A number of M orkers have been concerned ith the application of alternating current polarography to the study of reaction kinetics and mechanisms (12, 13, 9s). An interesting new idea suggested by Bauer and Foo (19) is alternating voltage polarography. An alternating current scan is applied to the cell and the resulting alternating voltage peak is measured. Alternating current can be moie easily controlled than alternating voltage in a.c. polarography, and as a result the circuit can be simplified. It is claimed that the new technique is more sensitive and calibration graphs are obtainable Ivith wider useful ranges. The characteristics of the cell are less important, and preliminary result:, a t low concentrations shou- results agreeing well with the calculated for reduction of cadmium and thallium. Instrunientation for alternating voltage polarography has been described by Bauer et al. (18).
The principal activity in square wave polarography has been applications to take advantage of its high sensitivity. Rosset (182) has reviewed the status of current theory and practice. Taylor (221) has desciibed a relatively simple apparatus to be used in connection with a conventional polarograph such a:, the Sargent Model XXI. The circuit avoid> the use of multivibrators and gating circuits, and itq resolution is comparable to that of the Barker-Jenkins equipment, although the wn5itivity is less. Buchanan and MeCarten ( 4 1 ) have described the design and construction of a controlled potential square \\aye polarograph, but have pointed out that it has not been extensively tested on chemical systems. Tajima and others (218) have suggested a simple modification to make the recorder sensitivity in a square wave polarograph continuously variable. Chang et al. (43) have reported briefly on what they call vibrato1 square wave polaiography involving the coupling of a pair of vibrators with a conventional polarograph. Sensitivity is not high. Davis (54) in a review of “recent advances” has discussed the present status of pulse polarography. Brinkman and Los (37) have derived an equation for diffusion controlled processes in pulse polarography, and Parry and Osteryoung (166) h a \ e made a study of the significant parameter:, in the analytical application of pulse polarography. They discuss both the derivative and noiinal modes operation and show that tht. claims for the resolution of pulse, square wave, alternating current or deiivative polarography are often misleading or erroneous. Karayanan and Venkatachalani (166) have used a time-
delay circuit for pulse polarography in which a signal, generated by detachment of the previous drop, is applied to a multivibrator which triggers an audiooscillator. The output of the audiooscillator is counted b y a decatron scaler, timing the application of a square wave of the desired width to the polarographic cell. Lyalikov and his coworkers (133) have applied pulse polarography to solid electrodes, particularly with stripping reactions. Barker and Surnberg (16) have applied to the drop a train of square wave pulqes of 1to 10-psezond individual duration in 1- to 10-kc. frequency for periods of about 0.04 second, and the mean rectification current in the second half of the 0.04 qecond is measured. So far the application has been to the measurement of very rapid reaction rates. The work of Schaap and NcKinney (189) on derivative polarography has already been mentioned. Oscillographic polarography continues to be popular in Europe. ievEik and lletzel (196) have described a new oscillographic polarograph of great versatility. It can, besides the uwal sine wave oscillographic techniques, utilize square or triangular shaped applied voltage and also rectangular current waves. Kalvoda (109, 110) compares square wave alternating cuiient oscillographic polarography with the conventional sine wave mode, and cites as the principal advantage the better defined conditions obtained a t the electrode. Kalvoda has also used oscillopolarography with rectangular alternating current as a means of measuring differential capacity of the dropping electrode (111). Bauer and Berg (17) have applied the technique to flowing systems. Two solutions of reactants are mixed within a fifth of a second, and motion pictures are taken of the oscilloscope screen. This technique allows the determination of moderately rapid reaction rates. e u a n et al. (51) applied oscillopolarography in molten ammonium formate medium and reported better reproducibility than in water for a number of systems. Gladyshev (77) has found it possible to use the oscillographic technique by polarizing the dropping mercury electrode as far as f1.5 volts. This method rewlts in useful incisions on the usual d E / d t curves for some organic compounds and ions, such as sulfate and phosphate. These studies were done in hydrochloric acid or hydrobromic acid solution. Gorodypkii et al. (7s) have w e d a low frequency polarization technique 11ith solid electrodes; a scan i i used slowly enough (several seconds) to allow the charging current to be tivo orders of magnitude loiver than with the conventional oscillographic polarography, while still avoiding some of the problems of passivation, polarization, and changes in active surface u i t h elechrodes having nonrenewable surfaces. Sturrock (211)
describes a preliminary investigation of a new technique which he calls derivative, cyclic constant current voltammetry, which is similar to the classical oscillographic polarography of Heyrovsk? and Forejt. Potential Sweep Chronoamperometry. Osteryoung and Parry (164) have made a study of t h e determination of mixtures b y this technique, which was formerly known as t h e Randles single-sweep method. They find t h e method good for four components in approximately equal amounts in both cathodic reductions and anodic stripping, and suggest t h a t anodic stripping may have slightly better resolution. I n the cathodic technique, starting the sweep on the diffusion plateau of a previous ion was helpful in determining small amounts of a more difficultly reduced constituent. I n this manner it was possible to measure cadmium in the presence of copper at a ratio of 1 to 1000. Mamantov et al. (137) utilized various electrodes including pyrolytic graphite. DeVries and Van Dalen (64) pointed out that distortion through ohmic drop might be serious (158) and that thP electrode position was important. Kalvoda and Ai-Chua (112) noted that certain supporting electrolytes show 10- to 100-fold increased sensitivity with certain constituentq. Perone and Mueller (171) have applied derivative techniques to chronoamperometry with stationary electrodes. Theoretical and analytical characteristics of first, second, and third derivatives were examined, and it was noted that the first derivative gave accuracy and precision comparable to that obtained in regular voltammetry but with about a 10-fold increase in sensitivity possible. Closely spaced reduction waves are more easily resolved and masking by a more easily reduced constituent tends to be minimized. Christie et al. (44) have treated the integration of chronoamperograms theoretically and found the results to check with experiment. Christie and Lingane ( 4 6 ) developed the theory of staircase voltammetry for reversible electrode reactions and have shown it to correspond with experiment. Nigmatullin and Vyaselev (16.9) likewise studied staircase voltage sweeps and concluded that the technique gave greater sensitivity than linear voltage scanning. VOLTAMMETRY WITH OTHER ELECTRODES
Mercury Electrodes. Mercury pool electrodes, although mainly used in chronopotentiometry, are occasionally applied in ordinary voltammetric techniques. Uruckenstein and Rouse (40) studied the effect of curvature of the mercury surface in a mercury pool electrode used for chronopotentiometry. The surface curvature resulted in VOL. 38, NO. 5, APRIL 1966
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an effective surface some 17y0greater than the projected area for a 2-sq. em. pool. This result should have bearing in mercury pool voltammetry also. The authors describe a cell which allows careful adjustment of pool size and position. Rouelle and Verdier (183)studied the Griffiths and Parker pool electrode which has a constant area with renewing surface, found it difficult to reproduce and reported that, although it is possible to get satisfactory results, the electrode does not have enough advantages to make it worthwhile for general use. Vogel (233) has described the design of a stationary hanging drop electrode in which the size of the drop is governed by a screw-driven piston and studied connection currents with it (238). Krasnova and Val’ko (125) described a similar stationary drop electrode involving a horizontal capillary with an upturned end and with the mercury flow governed by a stopcock. Saveant and T’ianello (189) described an easily therniostated hanging drop electrode which involves a steel cylinder and piston with a micrometer screw adjustment. Suzuki and Ozaki (213) recommend a “pushed out” drop electrode which they claim is easier to conqtruct and manipulate than previous designs. Roe and TGni (162) have studied a thin-film nieicury electrode for anodic voltammetry. If the mercury film is sufficiently thin, it is possible to ignore diffusion in the film and to stir the solution. I t is considerably more sensitive than the conventional hanging drop electrode. Matson et al. (142) have developed a composite graphite mercury electrode for anodic stripping voltammetry in which a thin film of mercury is deposited on graphite. The mercury is deposited electrolytically on a polished, way-impregnated graphite electrode. The amount of niercury is in the order of 10-7 moles per sq. cni. It has a decidedly higher hydrogen overvoltage than graphite and can be used repeatedly. Because of its high surface to volume ratio, it gives very sharp current peaks in anodic stripping voltammetry. Solid Electrodes. The disturbing influence of oxide films and other coatings on platinum electrodes are well known. Breiter (35) described the effect of coninion pretreatment processes on the adsorbing properties of smooth platinum electrodes. Schuldinger and Karner (191) suggest linearity in current us. tinie curves in the atoniic oxygen absorption region as a useful index of electrical cleanliness in platinum anodes. Adsorbed impurity is detectable in fractional monolayer amounts. Lingane (132) has derived equations for chronoamperometric constants for unshielded circular planar electrodes and shown the desirability of extrapolating to the T ~ equals zero, or t 1 ’ 2 equals zero intercept, in careful analytical work. Soos and
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’
Lingane (202) have done further work on this problem. Fried and Elving (72) and (73) have treated the rotating disk electrode mathematically and experimentally. Halpert and Foley (86) describe a Clark type cell with an alcoholic electrolyte good for measurement of oxygen tension to temperatures as low as -25’ C., and Horn and Jacob (35) have made a rotating plastic-coated gold electrode for determination of osygen. The electrode is prepared very simply by dipping into a 0.017, polystyrene in chloroform solution and drying. It is said to autoclave successfully and to be good for months of use. The pyrolytic graphite electrode has continued to attract much attention because of its unreactive properties. Chuang et al. (47) describe the construction of such an electrode and Turner and Elving (226) describe another form which they use for oddations in pyridine. Manning and llaniantov (138) give details for the construction of a pyrolytic graphite electrode set in boron nitride, which they describe as suitable for use in molten fluoride electrolytes. I3eilby et al. (20) compare the pyrolytic graphite film electrode with wax-impregnated graphite. Their pyrolytic electrode was prepared by depositing carbon on a ceramic rod a t high temperature. This technique, described in detail, provides means of preparing such electrodes without machine lvork on commercial pyrolytic carbon. They note that the ferricyanide reduction appears more reversible with the pyrolytic electrode than with waxed graphite and emphasize the importance of surface and method of preparation. Zittel and hliller (247) made an electrode by brazing platinum wire to pyrolytic graphite a t high temperature under vacuum and sheathing it in epoxies so that only the “a” plane was exposed. Mamantov et al. (136) found evidence of electrochemical and chemical oxidation producing films on pyrolytic graphite. Electrolytic oxidation and cerium( IV) produced films which differed electrochemically although both reduced at the same potential. The nature of the film was undetermined. Thomason (223) described the use of a pyrolytic graphite cup as both a vessel and electrode for microtitrations. This electrode could conceivably have application in polarography. The glassy carbon electrode has been described by Zittel and Miller (248). The material is a proprietary preparation of the Tokai Electrode Manufacturing Co. of Tokyo, Japan. It is much like pyrolytic graphite, but it is isotropic and therefore avoids the limitations of pyrolytic graphite, which requires special orientation and sealing of the edges Electrodes of glassy ~of crystal planes. carbon require very little maintenance. Some of their properties were originally
described by Yamada and Sato (243) who did not use them as electrodes in analytical chemistry. The carbon paste electrode has attracted a number of workers because of its unusual properties. Beilby and l l a t h e r (21) have pointed out that the resistance of a carbon paste electrode must be considered if the electrodes are farge! and they suggest Lhat other unidentified factors contribute to their unusual behavior. Kuwana and French (188) noted that carbon paste electrodes acted torvard organic compounds much as a mercury pool acts toward metals, and it is possible to electro-oxidize or reduce organic compounds out of or into the electrodes. Schultz and Kuwana (192) dissolved water-insoluble organic compounds in the pasting liquid and added graphite and ground to make electrodes containing the depolarizers. The work was mostly studies of ferrocene by chronopotentiometry. The behavior is analogous to anodic stripping of metals from amalgams. The authors suggest the possibility of concentrating organic constituents by solvent extracting into the electrode before electrolysis. Covington and La Coste (50) make electrodes from carbon and ceresine wax which are suitable for work in solutions containing as much as 80% alcohol. Marcoux ef al. (140) have also developed a carbon paste electrode suitable for nonaqueous solutions; the electrode involves sodium lauryl sulfate and Nujol which avoids preferential wetting of the carbon by nitromethane, acetonitrile, and propylene carbonate, but it is not good for use with dimethylformamide, dimethyl-sulfoxide or acetic acid. I n general, the behavior characteristics of this electrode are equal to or superior to those of the original carbon paste electrode. Emmott (67) has used the carbon paste electrode for the anodic stripping determination of mercury, and Davis and Everhart (53) have noted irreversible behavior of some compounds a t carbon paste electrodes, presumably due to dissolution in the electrode. A new development is the use of tin oxidecontaining conducting glass electrodes (65, 187). Of particular interest is the fact that the electrodes are transparent in the 305 to 700 nip region and that it is possible to monitor spectrophotonietrically species produced in electrolysis. Reddy et al. (179) described ellipsometric examination of films on platinum electrodes, involving the specular reflectivity of polarized light. It is possible to distinguish oxide from chemisorbed oxygen or water on electrodes held a t determinate potentials. Blaedel’s tubular platinum electrode (29) is useful in flowing systems. Studies have been made of so-called suspension electrodes which consist of metal powders in contact with metal electrodes (131). Subcasky (212) describes results in
which current voltage curves obtained with “bubbling” electrodes are recorded automatically and interpreted like polarograms. The repeated covering and uncovering of the electrode surface gives the effect of a semi-infinite diffusion control. Goth et a,l. (79) used a bubbling molybdenum electrode with success. They have found it applicable to molten fluoride systems using argon as the bubbling gas (185). A number of papers (147, 148) treating porous electrodes h a r e been concerned with possible application in fuel cells and seem a t present to have no analytical application. Inverse Polarography. This technique, often referred to as anodic stripping voltammetry or stripping voltammetry, grows increasingly popular because of its high sensitivity and intrinsic simplicity. Reviews have been prepared b y Stromberg and Zakharova (210), Kemula and Kublik (114), and 13arendrecht (15). Stroniberg (208) has discussed the theoretical factors which govern the sensitivity of inverse polarography. The optimum size of the hanging droll electrode depends ,upon the volume of the solution (which should be the smallest possible) and the duration of electrodeposition. As he points out in another paper with Igolinskii (101), the peak height depends on the ratio of electrode surface to the volume in which the metal is distributed. The least favorable form of electrode for high sensitiyity is conventional hanging mercury drop, and he recommends a film of mercury on another metal such as silver. Experimental studies on the effect of the volume of the solution were reported b y Stromberg and Kaplin (209). DeVries and Van Dalen (63) developed an approximate theory to describe anodic stripping from a planar mercury film electrode. The theory was strictly valid only for slow rates of linear potential scan and for thin films. DeVries (62) later presented a more exact mathematical treatment. Roe and Toni (181) have given equations for anodic stripping curves a t thin mercury film electrodes, and Matson et al. (142) using mercury-covered graphite electrodes have found very desirable electrochemical characteristics. Brainina and Kiva (34) used graphite rods impregnated with paraffin or eposy resins in place of hanging mercury drops for inverse polarography of copper and cadmium, and later (53) extended the technique to other metals. Bider and Bruckenstein (27) have pointed out that, in the inverse polarography of silver, oxide films on platinum give errors, which can be avoided by pretreatment. Perone and Oyster (172) have noted that it is possible to adsorb both inorganic and organic constituents on graphite electrodes a,nd determine them by inverse polarography; met,hy-
lene blue is detectable as low as 4 x 10-9LlI. Specker and Schiewe (203) cite paper as a source of error in the inverse polarography of very small amounts of certain metals. The introduction of unknown substances from filter paper can make errors as great as 50% for certain metals. Kemula and Strojek (115) recommend very rapid stripping of deposited metals by an oscilloscopic technique for increased sensitivity. Kozlovskii and his coworkers (124) have used an inverse polarographic technique to determine the amount of metals in amalgams. The inverse polarogram on a stationary drop is carried out until the current falls to one half of its original amount. Skobets and Karnaukhov (199) do inverse polarography in the preqence of supporting electrolytes which form insoluble precipitates with metals as they are stripped off. They claim that certain separations, such as cadniiuin and indium in hydroyide, are more readily achieved using this technique. Zakharov and Stroniberg ($45) have given a polarographic spectiurn of peak potentials of various elements in a variety of supporting electrolytes for inverse polarography. Perone and Birk (170) have applied derivative techniques to inverse voltamnietry using the hanging mercury drop electrode. Higher sensitivities and improved reqolution are claimed. Underkofler and Shain ($29) applied alternating current polarography a t stationary electrodes to the inverse polarographic method and claimed high sensitivity, the increase being of the order of a factor of 10 over direct current stripping. Skobets (200) pulsed currents with claims of higher sensitivity and reproducibility. Lyalikov (133) has a similar approach. Chuang and Elving (46) do solid electrode polarography with subsequent reversal of polarity-a type of low frequency cyclic voltammetry, which corresponds to inverse polarography of materials which do not adhere to the electrode. l r i e l et al. (8) describe a further elaboration of inverse polarography for trace analysis: the method of medium exchange. The metal is concentrated on a microelectrode in the usual way, the electrode transferred to a solution of a favorable supporting electrolyte, and the metal stripped into a very small volume. An ordinary polarographic scan is then done, reducing the metal back into the hanging drop. The potentialities of the method have been further esplored by Yarnitsky and ;2riel (244). The method has particular advantage where the stripping curve is complicated by interaction among the metals or with the electrode. Much higher sensitivity is obtainable than with simple cathodic scanning of the origirial solution. Berg and his coworkers have continued work in photopolarography.
The relative importance of various factors in the measurement has been considered @A$), and the determination of half-wave potentials of excited-state molecules discussed (23). Weller (238) in a theoretical paper used irreversible thermodynamics, continuum mechanics, and electrodynamics to develop a coniplete continuum-theoretical treatment of a polarizable two-phase system with different types of inner changes in a magnetic field; the treatment includes a general theory of i~hotopolarography. The theory is so general that the connection with photopolarography is not a t all evident. Heyrovski (92) has obtained evidence of a significant, photodecomposition of acidified water a t the D.1I.E. when strongly irradiated wit,h a mercury lamp. MISCELLANEOUS
Kolthoff (122) has given an excellent review of the fundamentals of polarography in inert organic solvents with special reference to acetonitrile. Takahashi (219) and Waivzonek (237) have reviewed polarography of inorganic and organic compoiinds in organic solvents, respectively. Various workers have studied pyridine as a solvent, both rvith the dropping mercury electrode (204) and the pyrolytic graphite electrode (226). TT’alter and Rosalie (236) describe the characteristics of aqueous dioxane as a polarographic Polvent, and Serrequi and Rallo (195) the use of liquid ammonium hesafluoroiihosphate ammoniate. llaricle and Hodgson (141) noted the reduction of oxygen to superoxide anion, a one-electron reduction process, in aprotic solvents. Acetonitrile continues to be a popular solvent but a difficult one to purify. Procedures have been suggested by Forcier and Olver (70) and O’Donnell et al. (160). Molten salt polarography has continued to increase in importance, and the subject has been reviewed by Gaur and Sethi (75). Swofford and his coworkers have studied sodiuni nitrate-potassium nitrate eutectic melts and examined the behavior of various cations and anions a t the dropping mercury electrode (214, 215). Swofford and McCormick (216) have done polarographic studies of nitrite and oside in the same medium using platinum electrodes. Snofford and Propp (217 ) esamined bromide and iodide at platinum electrodes in nitrate media. The polarography of metal ions in a lithium-potassium aluminum chloride nielts mas studied by Got6 and his coworkers (184). The same group has made studies in molten fluoride systems, using a molybdenum wire bubbling argon electrode and an alumina cell (185). Nanning and Mamantov (138) have successfully used pyrolytic graphite electrodes in molten fluoride media. Hladik and Norand (94) studied nitriteVOL. 38, NO. 5, APRIL 1966
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nitrate polarography in molten lithiumpotassium chloride eutectic with a vibrated gold electrode. The most interesting result was that they were able to get polarograms, though a t greatly reduced limiting currents, even when the electrodes were frozen into the medium. Reilley and his coworkers (7, 161, 162), among others, have been doing some very interesting work on the electrolysis of very thin layers of solution held between electrodes. The thickness may be less than the thickness of the normal diffusion layer; reproducible close spacing of the electrodes is obtained by means of micrometer control (96). The technique seems to be good for rapid analysis of mixtures of very low concentration. Delahay (48, 57, 58,205) and his associates have been studying open circuit potentials a t mercury electrodes of varying area, These potentials can be correlated with the kinetics of processes taking the place of the electrode. The technique has been suggested as offering possibilities for study of kinetics in media of very low conductivity. Polarographic measurements in flowing systems continue to be of interest and much of $he work has been done by Kimla and Strhfelda. These workers have published several papers on the theory of currents a t electrodes in flowing streams (118, 119, 206, 207). Kalous (107) has studied continuous analysis of protein fractions as they are eluted from a chromatographic column. Blaedel and Laessig (28) have a flowthrough D.M.E. and cell of very small volume for potentiometric measurements. Bruckenstein and Bixler (39) have introduced a new method known as chemical stripping analysis. A reactive metal such as silver is deposited on a rotating platinum electrode in known amount and the time is measured for a solution of an oxidizing agent to strip i t off by chemical reaction. The times are easily correlated with the concentration of the oxidizing agent. The method appears to be applicable down to concentrations as low as lO-'JM, Evans (68) has introduced a novel technique known as spot electrolysis. A droplet of sample is evaporated on a gold foil which is then made anodic or cathodic and plunged quickly into a supporting electrolyte, allowing electrolysis to take place. Less than 1 nanoeq. of electroactive substance is detectable and the useful quantitative range appears to be of the order of 5 to 20 nanoey. Hills (93) has written an unusually readable review of polarographic techniques at high pressures. Blaz'ek and Ragnerovh (SO) have followed up work of Love on polarography of radioactive isotopes with application to thallium and ruthenium. Alonso-Lopez (5) has studied the polarographic characteristics 268 R
ANALYTICAL CHEMISTRY
of cadmium in D 2 0 - H ~ 0 mixtures. The diffusion current of cadmium is surprisingly affected by heavy water concentrations greater than 35%, and the difference has been applied to a determination of the percentage of heavy water in light. Micka (149) has done further work on the depolarization of the dropping mercury electrode by suspensions of insoluble compounds, this time manganese dioxide. Particle size and electrical conductivity are significant variables, and a drop in limiting current at negative potentials is due to repulsion between the charged particles and the D.M.E. Kheifets and his coworkers (117) have proposed an algebraic method for simultaneous determination of two substances with similar half-wave potentials. The method appears to be of very limited application inasmuch as the diffusion coefficients of the two depolarizers must differ appreciably and the sum of the two concentrations must be determined by an independent method. Adams (3) has reviewed the applications of electron paramagnetic resonance techniques in electrochemistry. Wilson (240)has further developed the technique of millicoulometry and suggested apparatus and procedural criteria for improved accuracy and reliability. LITERATURE CITED
(1) Aaker, D. A., ANAL. CHEM.37, 1252 (1965). (2) Abrao, A,, Instituto de Energia Atornica Re@. IEA-56 (1962). (3) Adams, R. N., J . Electroanal. Chem. 8, 151 (1964). (4) Alden, J. R., Chambers, J. Q., Adams, R. N., Zbid., 5, 152 (1963). (5) Alonso-Lopez, J., Electrochim. Acta 10, 803 (1965). (6) Amis, E. S., J . Electroanal. Chem. 8, 413 (1964). 17) Anderson. L. B.. Reillev. " , C. N.. Zbid.. 'IO, 295 (1665). ' (8) Ariel, hf., Eisner, U., Gottesfeld, S., Zbid., 7, 307 (1964). (9) Armstrong, R. D., Fleischmann, &I., Koryta, J., Collection Czech. Chem. Commun. 30. 4342 (1965). (10) Arthur, P., ANAL. CHEM. 36, 70L (1964). (11) Atharale, V. T., Burangey, S. U., Dhaneshwar, R. G., J . Electroanal. Chem. 9, 169 (1965). (12) Aylward, G. H., Hayes, J. W., ANAL. CHEM.37, 195 (1965). (13) Ibid., p. 197. (14) Aylward, G. H., Hayes, J. W., J . Electroanal. Chem. 8, 442 (1964). (15) Barendrecht, E., Chem. Weekblad 60, 345 (1964). (16) Barker, G. C., Nurnberg, H. W., Naturwissenschaften 51 , 191 (1964). (17) Bauer, E., Berg, H., Chem. Zvesti 10, 454 (1964). (18) Bauer, H. H., Britz, D., Foo, D. C. S., J . Electroanal. Chem. 9, 481 (1965). (19) Bauer, H. H., Foo, D. C. S., J . Electroanal. Chem. 7, 392 (1964). (20) Beilby, A. L., Brooks, W., Lawrence, G. L., ANAL.CHEY.36, 22 (1964). (21) Beilby, A. L., Rlather, B. R., Zbid., 37, 766 (1965). (22) Belew, W. L., Raaen, H. P., J . Electroanal. Chem. 8, 475 (1964).
(23) Berg, H., Gollmick, F. A,, Collection Czech. Chem. Commun. 30, 4192 (1965). (24) Berg, H., Schweiss, H., Electrochim. Acta 9, 425 (1964). (25) Bezuglyi, V. D., Saliichuk, E. K., Dokl. Akad. Nauk S.S.S.R. 158, 1309 (1964). (26) Bibliografia Polarographia Supp. No. 15, Cons. Naz. Della Ricerche, Rome, 1964.
(27) Bixler, J. W., Bruckenstein, S., ANAL. CHEM.37, 791 (1965). (28) Blaedel, W. J., Laessig, R. H., Zbid., p. 1255. (29) Blaedel, W. J., Olson, C., Zbid., 36, 3431 (1964). (30) Blaiek, J., WagnerovA, D. AI., Collection Czech. Chem. Commun. 29. 915 (1964). (31) Boddy, P. J., J . Electroanal. Chem. 10, 199 (1965). (32) Booman, G. L., Holbrook, W. B., ANAL.CHEM.37, 975 (1965). (33) Brainina, Kh. Z., Kiva, N. K., Ukr. Khim. Zh. 30, 697 (1964). (34) Brainina, Kh. Z., Kiva, N. K., Zavodsk. Lab. 29, 526 (1963). (35) Breiter, ?*I.W., J . Electroanal. Chem. 8, 230 (1964). (36) Breiter, h1. W., J . Electrochem. SOC. 112, 845 (1965). (37) Brinkman, A. A. A. M.,Los, J. M., J . Electround. Chem. 7, 171 (1964). (38) Broman, R. F., Murray, R. W., ANAL.CHEY.37, 1408 (1965). Zbid., (39) Bruckenstein, S., Bixler, J. W., 786.
(40)Bruckenstein, S., Rouse, T. O., Zbid., 36, 2040 (1964). (41) Buchanan, E. B., hIcCarten, J. B., ASAL. CHEM.37, 29 (1965). (42) Butler, C. G., Kaye, R. C., J . Electroanal. Chem. 8,463 (1964). (43) Chang, Tsu-Hsun et al., Acta Chim. Sinica 30, 108, 111 (1964). (44) Christie, J. H., Lauer, G., Ostervoune. R. A.. J . Eleclrochem. SOC.111. 142011964). ' (45) Christie, J. H., Lingane, P. J., J . Electroanal. Chem. 10, 176 (1965). (46) Chuang, L., Elving, P. J., ANAL. CHEM.37, 1506 (1965). (47) Chuang, L., Fried, I., Elving, P. J., Zbid., 36, 2426 (1964). (48) Cole, H. D. F., Delahay, P., Susbielles, G. G., Collection Czech. Chem. Commun. 30, 3979 (1965). (49) Costa, J. hl., Spritzer, hl. S., Elving, P. J., AKAL.CHEM.36, 698 (1964). (50) Covington, J. R., La Coste, R. J., Zbid., 37, 420 (1965). (51) Cyan, Sun-Pao, Doleial, J., Kalvoda, R., Zyka, J., Collection Czech. Chem. Commun. 30,4111 (1965). (52) Damaskin, B. B., J . Electroanal. Chem. 7, 155 (1964). (53) Davis, D. G., Everhart, &I. S., ANAL. CHEY.36, 38 (1964). J . Roy. Znst. Chem. 88, (54) Davis, H. X., 104 (1964). (55) DeFay, R., et al., J . Electroanal. Chem. 7, 417 (1964). (56) Zbid., 8,412 (1964). ( 5 7 ) Delahay, P., Zbid., 10, l(1965). (58) Delahay, P., J . Phys. Chem. 68, 981 f1964\ \ - - - - I
(59) De Levie, R., J . Electroanal. Chem. 9, 117 (1965). (60) Zbid., p. 311. (61) Del Mastro, J. H., Smith, D. E., Zbicl., 9, 192 (1965). (62) DeYries, W. T., Ibid., 9, 448 (1965). 163) DeVries. W. T.. Tan Dalen. E.. Zbid., 8 , 366 (1964). ' (64) Ibid., 10, 183 (1965). (65) Dubrovinskii, J-. Ya., Kumok, V. N., Zh. Analit. Khim. 19, 1159 (1964). (66) Durst, R. A., Ross, J. W., Hume, D. N., J . Electroanal. Chem. 7, 245 (1964). I
~
,
(67) Emmott, P., Talanta 12, 651 (1965). (68) Evans, I). H., ANAL.CHEM.37, 1520 (1965). (69) Flemming, J., Berg, H., J . Electroanal. Chem. 8, 291 (1964). (70) Forcier, G. A., Olver, J. W., ANAL. CHEY. 37, 1447 (1965). (71) Frei, Y. F., Miller, I. F., J . Phys. Chem. 69, 3018 (1965). (72) Fried, I., Elving, P. J., ANAL.CHEX 37, 464 (1965). (73) Ibid., p. 803. (74) Frumkin, Y., J . Electroanal. Chem. 7, 152 (1964). ( 7 5 ) Gaur, H. C., Sethi, R.S., Ibid., 7,474 (1964). (76) Giner, J., J . Electrochem. SOC.111, 376 (1‘364). (77) Gladyshev, I-.P., Chem. Zvesti 17, 575 (1963). (78) Gorodyskii, A. V. et al., Zavodsk. Lab. 29, 1035 (1963): (79) GotB, H., Suzukii, S., Saito, AI., J . Chem. Soc. Japan, Pure Chem. Sect. 84, 41 (1963). (80) Gupta, S. L., Chatterjee, RI. K., J . Electroanal. Chem. 8, 245 (1964). (81) Gupta, S. L., Chatterjee, bl. K., Sharma, S.K., Ibid., 7, 81 (1964). (82) Gupta, S. L., Sharma, S. K., Talanta 11, 105 (1964). (83) Gutmann, V., Scherzer, J., Schober, G., Monatsh. Chem. 95, 25 (1964). (84) HBla, J., Chem. Listy 59, 365 (1965). (85) Hallett, L. T., ASAL. CHEM.37, No. 8, 95A (1965). (86) Halpert, G., Foley, R. T., J . Electroanal. Chem. 6, 426 (1963). (87) Harper, K. A., Casimir, D. J., Kinnersley, H. W.,Zbid., 9, 477 (1965). Leyden, 11. E., Reilley, (88) Hayes, J. W., C. N., ANAL.CHEM.37, 1444 (1965). (89) Hayes, J. W., Heilley, C. N., Zbid., 37, 1322 (1965). (90) Heyrovsk9, J., bibliography of publications dealing with the polarographic method in 1961, Czech. Acad. Sci., Prague, 1963. (91) Heyrovakj., J., bibliography of publications dealing with the polarographic method in 1962, Czech. Acad. Sci., Prague, 1964. (92) Heyrovskf., ll.,Norrish, R. G. W., A’ature 200, 880 (1963)’. (93) Hills, G. J., Talanta 12, 1317 (1965). (941 Hladik. J.. Norand. G.. Bull. Soc. dhim. France ’1965, p. 828. ’ (95) Horn, G., Jacob, H.-E., Chem. Tech. (Berlin) 16, 237 (1964). (96) Hubbard, A. T., Anson, F. C., ANAL. CHEM.36, 723 (1964). (97) Hume, I). N., Zbid., 36, No. 5, 200R ( 1964). (98) Hung, H. L., Del hlastro, J. R., Smith, D. E., J . Electroanal. Chem. 7, 1 (1964). (99) Hung, H . L., Smith, D. E., ANAL. CHEM. 36, 922 (1964). (100) Hurwitz, H. D., J . Electroanal. Chem. 10, 35 (1965). (101) Igolinskii, V. A., Stromberg, A. G., Zavodsk. Lab. 30, 656 (1964). (102) Jacobsen, E., Kalland, G., Anal. Chim.Acta 30, 240 (1964). (103) JeftiC, Lj., Branica, hI., Croat. Chem. Acta 35,211 (1963). (104) Jehring, H., Chem. Zvesti 10, 313 (1964). (105) Jehring, H., Z . Physik Chem. ( L e i p i g ) 225, 116 (1964). (106) Zbid., 226, 59 (1964). (107) Kalous, V., Chem. Listy 57, 1180 (1963). (108) Kalous, V., J . Electroanal. Chem. 8, 250 (1964). (109) Kalvoda, R., Chem. Zvesti 18, 450 (1964). (110) Kalvoda, R., Collection Czech. Chem. Commun. 29, 1790 (1964). (111) Ibid., 30,4280(1965). ~
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(112) Kalvoda, R., Ai-Chua, J., J . Electroanal. Chem. 8, 378 (1964). 1113) Kastenine. B.. Holleck., L.., Talanta 12, 1259 ( 1 9 a ) . ‘ (114) Kemula, W., Kublik, Z., Adv. Anal. Chem. Instrumentation 2, 123 (1963). (115) Kemula, W., Strojek, J., Chem. Anal., Warsaw 8 , 685 (1963). (116) Kheifets, L. Ya., Zh. Analit. Khim. 20, 388 (1965). (117) Kheifets, L. Ya., Preobrazhenskaya, E. A,, Bezuglgi, lr.D., Ibid., 19, 607 (1964). (118) Kimla, A., Collection Czech. Chem. Commun. 29. 1956 (1964). (119) Kimla, A.,Strkfelda, F., Ibid., 29, 2913 (1964). (120) Kirchmavr. H. R.. Electrochim. Acta 9. 459 fi9k4i. (121) Kdch, K.-H.; Scherff, H. M,,2. Anal. Chem. 199, 244 (1963). (122) Kolthoff, I. hl., J . Polarog. Soc. 10, 22 (1964). (123) Kowalski. Z.. Srzednicki. J..’ J . Electroanl. Chkm. 8, 399 (1964). (124) Kozlovskii, 31.T., Omarova, K. D., Levitskaya, S. A., Vestn. Akad. LVauk Kaz. S.S.R. 20, 81 (1964). (125) Krasnova, I. E., Val’ko, A. T., Zavodsk. Lab. 29, 1148 (1963). (126) KCita, J., Weber, J., Electrochim. Acta 9, 541 (1964). (127) Kuwana, T., Darlington, R. K., Leedy, D. W., ANAL. CHEM.36, 2023 (1964). (128) Kuwana, T. W., French, W. G., Ibid., 36, 243 (1964). (1291 Lafornue-Kantzer. D.. hluxart. 31.. Electrochzk. ilcta 9, 1b1 (1964). (130) Laitinen, H. A , , Chambers, L. hI., AXIL. CHEhf. 36, 5 (1964). (131) Lazorenko-Manevich, R. Jl.,Ushakov, A. T., Dokl. Akad. S a u k S.S.S.R. 161. 156 11966). (132) ’Lingane, P . J., ANAL. CHEM.36, 1723 (1964). (133) Lyalikov, Yii. S., Madan, L. G., Bodyu, T. I., Zavodsk. Lab. 29, 1289 (1963). (134) Mairanovskii, S. G., Dokl. Akad. S a u k S.S.S.R. 154, 683 (1964). (135) Malik, W. U., Chand, P., ANAL. CHEM.37, 1592 (1965). (136) hlamantov, G., Freeman, D. B., Rliller, F. J., Zittel, H. E., J . Electroanal. Chem. 9, 305 (1965). (137) llamantov, G., Manning, D. L., Dale, J. RI., Ibzd., 9, 253 (1965). (138) Rlanning, D. L., llamantov, G., Ibid., 7, 102 (1964). (139) RIann, C. K., ANAL.CHEY.37, 326 (1965). (140) Marcoux, L. S., Prater, K. B., Prater, B. G., Adams, R. N., Ibid., p. 1446. (141) Maricle, D. L., Hodgson, W. G., Ibid., p. 1562. (142) Matson, W. R., Roe, D. K., Carritt, D. E., Ibid., 1594. (143) hlatsuda. H.. 2. Elektrochem. 62. 977 (1958). (144) lleibuhr, S. G., Electrochim. Acta 10, 215 (1965). (145) RIeites, L., “Polarographic Techniques,” Interscience, New York, 1965. (146) Metzl, K., SevEik, F., Chem. Zvesti 18, 462 (1964). (147) Rlicka, K., Collection Czech. Chem. Commun. 29, 1998 (1964). (148) Ibid., 30, 223 (1965). (149) Ibid., p. 235. (150) Miller, G. W., Long, L. E., George, G. hl., ANAL.CHEM.36, 1144 (1964). (151) hliller, I. R., J . Phys. Chem. 69, 2740 (1965). (152) lluller, 0. H., J . Chem. Educ. 41, 320 (1964). (153) Muller, R. H., ANAL.CHEM.36, No. 10, 123A (1964). ,
I
,
I
(154) Nancollas, G. H., Tincent, C. A., Electrochim. Acta 10, 97 (1965). (155) Xarayan, R., Electrochim. Acta 9, 1333 (1964). (156) Xarayanan, 0. H., 1-enkatachalam, K. R., J . Electroanal. Chem. 5, 158 (1963). (157) NEmec, L., Ibid., 8, 166 (1964). (158) Nicholson, R. s., ANAL.CHEM. 37, 667 (1965). (159) Nigmatullin, It. Sh., Vyaselev, M. R., Zh. Analit. Khim. 19,545 (1964). (160) O’Donnell, J. F., Ayres, J. T., Mann, C. K., ANAL.CHEM.37, 1161 (1965). (161) Oglesby, I).RI., Anderson, L. B., RlcI)uffie, B., Reilley, C. N., ANAL. CHEW37, 1317 (1965). (162) Oglesby, D. 31., Omang, S. H., Reilley, C. N., Ibid., p. 1312. (163) Okinaka, Y., Kolthoff, I. AI., llurayama, T., J . Ani. Chem. Soc. 87, 423 (1965). (164) Osteryonng, R. A., Parry, E. P., J . Electroanal. Chem. 9, 299 (1965). (165) Parry, E. P., Osteryoung, R. A., ANAL.CHEM.36, 1366 (1964). (166) Parry, E . P., Osteryoung, R. A., Ibid., 37, 1634 (1965). (167) Parsons, R., J . Electroanal. Chem. 7, 136 (1964). (168) Zbid., 8, 93 (1964). (169) Peizker, J., Collectzon Czech. Chem. Commun. 24, 2405 (1959). (170) Perone, S. P., Birk, J. R., ANAL. CHEM.37, 9 (1965). (171) Perone, S. P., blueller, T. R., Ibzd., p. 2. (172) Perone, S. P., Oyster, T. J., Zbzd., 36, 235 (1964). (173) Powell, K. G., Reynolds, G. F., Electrochzm. Acta 10, 921 (1965). (174) “Proceedings of First Australian Conference on Electrochemistry, February 1963,” Pergamon Press, 1965. (175) Raaen, H. P., AXAL. CHEM. 36, 2420 (1964). (176) Raaen, H. P., Ibzd., 37, 677 (1965). (177) Ibzd., p. 1355. (178) Rabuzin, T., PravdiC, V., J . Electroanal. Chem. 9, 435 (1965). (179) Reddy, A. K. K., Grenshaw, M., Bockris, J. O’hl., Ibzd., 8, 406 (1964). (180) Reinmuth, Wr. H., ANAL.CHEM.36, No. 5, 211R (1964). (181) Roe, 1). K., Toni, J. E. A,, Ibid., 37, 1503 (1965). (182) Rosset, R., Chim. Anal. (Paris) 45, 5Y6 (1963). (183) Rouelle, F., Verdier, E. T., J . Electroanal. Chem. 8 , 409 (1964). (184) Saitb, Jl., Suzuki, S., GotB, H., J . Chem. Soc. Japan, Pure Chem. Sect. 83, 883 (1962). (185) SaitB, RI., Suzuki, S., Got6, H., Sei. Rept. Res. Inst. TBhoku Univ. A17, 80 (1965). (186) Sathyanarayana, S., J . Electroanal. Chem. 10, 56 (1965). (187) Ibzd., p. 119. (188) Saveant, J. AI., Vianello, E., Electrochim. Acta 10, 905 (1965). (189) Schaap, W. B., RIcKinney, P. S., ANAL.CHEM.36, 29 (1964). (190) Ibzd., p. 1251. (191) Schuldinger, S., Warner, T. B., J . Phys. Chem. 68, 1223 (1964). (192) Schultz, F. A., Kuwana, T., J . Electroanal. Chem. 10, 95 (1965). (193) Sellers, D. E., Vandenborgh, N. E., J . Am. Chem. SOC.86, 1934 (1964). (194) Ibid., 87, 1206, 1396 (1965). (195) Serrequi, J., Rallo, F., Ric. Sci. Rend. 4, 209 (1964). (196) SevEik, F., Metzl, K., Chem. Zvesti 18, 4I., ANAL. CHEM.37, 45 (1966). (237) Wawzonek, S., Talanta 12, 1229 il966). (238) geller, K., J . ElectroanaL Chem. 10, 270 (1965). (239) Will, F. G., J . Electrochem. Soc. 112, 1157 (1965). (2401 Wilson. A. h1.. J . Electroanal. Chem. 10. 332 (lg65). (241j Rittick, J. J., Rechnitz, G. A., A x a CHEW ~ 37, 817 (1965). (242) Wolf, D., J . Electroanal. Chem. 5 , 186 (1963). (243) Yamada, S.,Sato, H., Suture 193, 261 (1962). (244) Yarnitsky, Ch., Ariel, AI., J . Electroanal. Chem. 10, 110 (1965). (245) Zakharov, h1. S.,Stromberg, A. G., Zh. Analit. Khim. 19, 913 (1964). (246) Zhdanov, S. I., Kislev, B. A., Dokl. Akad. S a u k S.S.S.R. 155, 651 (1964). (247) Zittel, H. E., hliller, F. J., AKAL. CHEM.36, 45 (1964). (248) Zittel, H. E., Miller, F. J., Ibid., 37, 200 (1965). (249) Zuman, P., in “Advances in Analytical Chemistry and Instrumentation,” C. N. Reilley, ed., p. 219, Wiley, Sew York. 1963 (2jO) Zuman, P., “Organic Polarographic ilnalysis,” Pergamon, New York, 1964. WORK supported in part through funds provided by the U. S. Atomic Energy Commission under Contract AT(30-1)905.
Electrochemical Relaxation Techniques W.
I
H. Reinmuth,
Department o f Chemistry, Columbia University, N e w York, N . Y.
review under the present title ( 1 4 4 , the reviewer presented a general survey of the field. The present paper will confine its attention largely to research appearing in the literature of 1964-65. X o pretense is made to completeness, coverage is confined almost entirely to papers to which the reviewer had direct access a t the time of writing. Because Electroanalytical Abstracts efficiently scavenges the literature for pertinent work, the reader is urged to rely on it for extensive review. and on the present work only for more intensive discussion of selected papers. N THE FIRST
SMALL AMPLITUDE TECHNIQUES
Small amplitude techniques have attracted interest largely as methods for evaluation of kinetic parameters of charge-transfer processes per se. The last two years have seen no dramatic breakthroughs in this area. Rather it seemed a period of consolidation. Basic theory and practice are well established, but early results gave many anomalies. N o w refinements in experimental techniques and methods of
270 R
ANALYTICAL CHEMISTRY
data analysis are elucidating some of the causes of the discrepancies. The transient techniques, galvanostatic, potentiostatic, voltostatic, coulostatic, uniformly suffer from complexity of theory when mass and chargetransfer and double layer capacitance contribute to the observed relaxation even when relatively simple linearized theoretical models are adopted. For galvanostatic results, it has been common practice to determine kinetic parameters by extrapolating data from relatively long tinies where diffusion becomes dominant and theory simpler. However, potential increases with time a t constant current, and, as it does, the basic premise of linearized theory (small potential excursions) becomes less tenable. The criterion by which the applicability of the theory is judged rests on its accuracy of prediction of potential a t any given time. Since deviations due to nonlinearity a t long times are systematic, however, kinetic parameters based on extrapolation may suffer much larger errors than this simple criterion would indicate. Birke and Roe (22) have attempted to deal with this difficulty by extending the
10027
linearized model to include higher order terms. It appears, however, that their approach is faulty (104) and that their result represents a first order approximation equivalent to the linearized approximation though differing from it in form. Sluyters-Rehbach and Sluyters (159) have indicated a related source of error of particular interest in connection with the Hg/Hg2+2 couple. I n the region of interest, the double layer capacitance changes quite dramatically with potential, and these workers suggest that failure to take account of this nonlinearity may have influenced previous results. I n principle nonlinearities of the types described above should be detectable by comparing results obtained by cathodic and anodic perturbation. Under true linear conditions such results would be identical. More detailed theoretical analysis of nonlinearities would be of interest. Birke and Roe (23) have examined a double pulse galvanostatic method which seems to be based on the same philosophy as Gerischer’s original (64), namely to get the double layer charging out of the way on the first pulse so that the faradaic reaction can be examined
