i V THE ANALYST [September, 1973THE ANALYSTE D IT0 RIAL AD VI SO RY BOA R DChairman: H. J. Cluley (Wembley)*L. S. Bark (Salford)R. Belcher (Birmingham)L. J. Bellamy, C.B.E. (Waltham Abbey)L. S. Birks (U.S.A.)E. Bishop (Exeter)E. A. M. F. Dahmen (The Netherlands)*J. B. Dawson (feeds)A. C. Docherty (BillinghamjD. Dyrssen (Sweden)*W. T. Elwell (Birmingham)*D. C. Garratt (London)*R. Goulden (Sittingbourne)J. Hoste (Belgium)D. N. Hume (U.S.A.)H. M. N. H. Irving (Leeds)A. G. Jones (Welwyn Garden City)M. T. Kelley (U.S.A.)*J. A. Hunter (Edinburgh)W. Kemula (Poland)*G. F. Kirkbright (London)G. W. C. Milner (Harwell)G. H. Morrison (U.S.A.)*J. M. Ottaway (Glasgow)*G. E. Penketh (Billingham)S. A. Price (Tadworth)D. I. Rees (LondonjE.B. Sandell (U.S.A.)*R. Sawyer (London)A. A. Smales, O.B.E. (Harwell)H. E. Stagg (Manchester)E. Stahl (Germany)A. Walsh (Australia)T. S. West (London)P. Zuman (U.S.A.)*A. Townshend (Birmingham)* Members of the Board serving on the Executive Committee.NOTICE TO SUBSCRIBERSSubscriptions for The Analyst, Analytical Abstracts and Proceedings should beThe Chemical Society, Publications Sales OfFice,Blackhorse Road, Letchworth, Herts.Rates for 1973(a) The Analyst, Analytical Abstracts, and Proceedings, with indexes . . . . €37.00(b) The Analyst, Analytical Abstracts printed on one side of the paper (withoutindex), and Proceedings . . . . . . . . . . . . . . €38.00(c) The Analyst, Analytical Abstracts printed on one side of the paper (withindex), and Proceedings .. . . . . . . . . . . . . €45.00(other than Members of the Society)sent to:The Analyst and Analytical Abstracts without Proceedings-(d) The Analyst and Analytical Abstracts, with indexes . . . . . . . . €34.00(e) The Analyst, and Analytical Abstracts printed on one side of the paper (withoutindex) . . . . . . . . . . . . . . . . . . f35.00( f ) The Analyst, and Analytical Abstracts printed on one side of the paper (withindex) . . . . . . . . . . . . . . . . . . €42-00(Subscriptions are NOT accepted for The Analyst and/or for Proceedings alonevi SUMMARIES OF PAPERS I N THIS ISSUE [September, 1973Summaries of Papers in this IssueMass and Charge Transfer Kinetics and Coulometric CurrentEfficienciesPart IX. An Examination of the Titanium(1V) - Titanium(II1)System and the Effects of Ultratrace Impurities in Sulphuric AcidTitanium (111) has found considerable use as a coulometric intermediate,and is the strongest reductant that can be generated with good efficiencyin aqueous media.Atsuch high concentrations, a surfactant impurity becomes adsorbed on theworking electrode and very seriously reduces the speed of the charge-transferprocess and therefore the current efficiency. A method of purification oftlie sulpliuric acid by electrosorption is shown to give a charge-transfer rateconstant in excess of 1 s-l, but charcoal column purification iswithout effect. Both 7 and 10 M sulpliuric acid media were examined, butbecause tlie mass-transfer rate is decreased by the higher viscosity of the10 M acid there is little difference in current efficiency.Addition of iron(II1)or iron(I1) hinders the adsorption of the impurity and the deactivation ofthe electrode, but offers no special benefit. Electrode kinetic parameters arereported for various treated and untreated media, and current efficienciesfor the generation of titanium (111) are computed. The behaviour in perchloricacid is re-interpreted.E. BISHOP and P. H. HITCHCOCKChemistry Department, University of Exeter, Stocker Road, Exeter, EX4 4QD.Analyst, 1973, 98, 625-634.The medium is restricted to strong sulphuric acid.Mass and Charge Transfer Kinetics and Coulometric CurrentEfficienciesat Platinum and Gold ElectrodesPart X.An Examination of the Tin(1V) - Tin(I1) - Tin(0) SystemsTin(I1) is more readily handled coulometrically than volumetrically, andthe electrode processes are critically evaluated. Zero-current tin (IV) - tin(I1)potentials cahnot be measured or derived from Lewartowicz plots, and charge-transfer kinetic parameters must therefore be referred to 0 V. Gold cathodesare deactivated towards reduction of hydrogen ion by specific adsorptionof bromide ion, and give well separated waves for the reduction of tin(1V)to tin(T1) and to tin metal, with limiting currents proportional to the tin(1V)concentration in 3-0 M bromide plus 0.4 M perchloric or hydrobromic acidmedium. Mass and charge transfer kinetic parameters are derived from thevoltamniogranis. Platinum cathodes become filmed and theories of thenature of the film are reviewed in the light of new work, which shows thatthe film is difficult to remove and was not completely removed in earlier work.'The generation of tin(I1) in bromide medium is superimposed on the filni-suppressed hydrogen-ion wave.Chloride media are unsuitable. Kineticparameters must be derived from anodic voltammograms of tin(II), whichare uncomplicated in the bromide medium. At low bromide concentrations,the platinum anode is filmed with a species such as [SnBr,OHI2-, which blockstlie reaction. The electrode mechanism is discussed. Charge-transfer para-meters vary with potential or current, but synthesised computer-plottedvoltammograms give a good fit with experimental curves.From the kineticparameters the current efficiency for tin(I1) generation is computed, andfor 0.2 M tin(1V) the efficiency is better than 99.98 per cent. over the currentdensity range 100 to 300 mA cm-2 but decreases rapidly outside this range.Sample concentrations must be chosen so as to maintain the intermediatecurrent within range throughout the determination, and platinum cathodesmust be filmed quickly, but not aged for too long.E. BISHOP and P. H. HITCHCOCKChemistry Department, University of Exeter, Stocker Road, Exeter, EX4 4QD.Analyst, 1973, 98, 635-646viii THE ANALYST [Scptcmbcr, 1973What'sfastautomatic and hoes60 proteinhydrolysate runs at weekends. ?and time wasting.protein hydrolysate run takes less thanWith Chromaspek, a singlefazest amino acid analyser in the business.Chromaspek is so sensitive that you can quantitate500 picomole peaks.The sample disc accommodates 60 separatesamples and will analyse each in successionautomatically, without attention, and record the results.So you can set up Chromaspekon Friday, let it workallweekend, and check the finished results on Mondaymorn i ng.And Chromaspek is so simple. 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