August, 19731 SUMMARIES OF PAPERS I N THIS ISSUESummaries of Papers in this IssueMass and Charge Transfer Kinetics and Coulometric CurrentEfficienciesPart VII. Conditional Potentials, and Single- scan Voltammetryof Pure Vanadium(V) - Vanadium(1V) Systems in VariousMedia at Platinum Electrodes Pre- treated by Five MethodsThe limited previous work on vanadium is reviewed. Five methods ofelectrode pre-treatment have been selected and are described. The variationof the conditional potential of the vanadium(V) - vanadiurn(1V) systemwith hydrogen-ion concentration is reported. The experimental work iscomplicated by isopolymerisation reactions, of which a t least one is kineti-cally slow. The voltammetric reduction of vanadium (V) in saturated potas-sium sulphate - acetate buffer a t pH 4-0 is examined: the benefit of shiitingsolvent reaction potentials to more negative potentials is nullified by thedirect reduction of un-ionised acetic acid.M sulphuricacid and in one of 2.0 M sulpliuric acid.Possible adsorption effects arecanvassed. The complex behaviour a t intermediate hydrogen-ion concen-trations is discussed, with illustrations drawn from a sulphuric acid mediumof pH 2.0. It isconcluded that the electrochemical behaviour of the vanadium system isstrongly dependent 011 hydrogen-ion concentration and on the electrodepre-treatment. The electrode can be chemically oxidised in vanadium (V)solutions. The mechanism is a one-step one-electron process. No evidencecould be found for reduction below the +4 oxidation state a t platinum.Vanadium( IV) cannot be oxidised without severe loss of current efficiency,nor reduced to vanadium(II1) at platinum electrodes.E.BISHOP and P. H. HITCHCOCKChemistry Department, University of Exeter, Stocker Road, Exeter, EX4 4QD.Analyst, 1973, 98, 553-562.A similar examination is made in a medium of 5 xThe anodic oxidation of vanadium(1V) is briefly examined.Mass and Charge Transfer Kinetics and Coulometric CurrentEfficienciesin the Presence of Chromium, Manganese and Iron, and the KineticParameters of the Vanadium System, at Platinum ElectrodesPre-treated by Five MethodsContinuing the earlier examination of the vanadium system alone, undervarious conditions and with various electrode pre-treatments, the effect ofneighbouring steel-forming d-block elements has been investigated. Chro-mium(V1) at pH 4-0 suppresses the vanadium(V) reduction wave, and thedegree of suppression is quantitatively proportional to the chromium (VI)concentration. Activated electrodes are deactivated by dipping them ina chromium(V1) solution, and remain so even when well washed thereafter,so that chromium(V1) as well as chromium(II1) is adsorbed strongly onplatinum.In 2.0 M sulphuric acid, chromium(V1) and vanadium(V) arereduced at the same rate. Manganese(VI1) in acetate buffer gives a fast,well separated wave, but the separation is not as good in 2.0 M sulphuric acid;slowing the vanadium(V) reduction by using an oxidised electrode effects noimprovement : the manganese wave is similarly affected.Addition ofchromium(V1) to the manganese - vanadium mixture at pH 4 suppressesthe manganese wave only slightly, even when the vanadium wave is com-pletely suppressed. In 2.0 M sulphuric acid, the manganese wave is un-distorted and chromium and vanadium are simultaneously reduced. Iron(II1)in 2-0 M sulphuric acid does not interfere, but the separation of the vanadiumand iron waves is not good. Iron(I1) can, however, act as a potentiostaticintermediate. The kinetic parameters of the vanadium system are repro-ducible in acetate buffer, but only when the electrode is fouled in 2.0 Msulphuric acid. Pattern theory and diffusion-corrected Lewartowicz methodsgive results that agree. The charge-transfer kinetic parameters are shownto be potential dependent in acidic media.The results are compared withthose in earlier reports. The generation current efficiency for vanadium (IV)in acetate buffer was computed.E. BISHOP and P. H. HITCHCOCKChemistry Department, University of Exeter, Stocker Road, Exeter, EX4 4QD.Analyst, 1973, 98, 563-571.Part VIII. Single-scan Voltammetry of Vanadium(V) - Vanadium(1V)...11iV THE ANALYST [August, 1973THE ANALYSTE D I T 0 R I AL AD VI S 0 RY BOARDChairman: H. J. Cluley (Wembley)*L. S. Bark (Salford)R. Belcher (Birmingham)t. J. Bellamy, C.B.E. (Waltham Abbey)L. S. Birks (U.S.A.)E. Bishop (Exeter)E. A. M. F. Dahmen (The Netherlandsj*J. B. Dawson (Leeds)A. C. Docherty (BillinghamjD. Dyrssen (Sweden)*W.T. 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I73-ACCI Name I AddressCity State/Country Zip I Your Nature of Company’sCompany Business0 I am an ACS member 0 I am not an ACS member Bill company 00 Bill me for $- Payment enclosed in the amount of $-(payable to American Chemical SocietySUMMARIES OF PAPERS I N THIS ISSUEManganese and Vanadium - Iron Mixtures and the Influenceof Chromium on the ProcessEarlier voltammetric work permitted the mass and charge transferkinetic parameters of the vanadium system to be calculated for diverse mediaand platinum electrode prc-treatments, and command potentials to beselected for potentiostatic determination of vanadium alone and in certaincombinations with other steel-forming elements. A simple coulometric celland an adaptation of a commercial potentiostat are described.Currentintegration by strip-chart recorder is too inaccurate and so RC integrationis discussed. Philbrick SP456 amplifiers refused capacitive feedback, butvery satisfactory results were given by Solartron AA 1023 amplifiers. Thedesign of a very high quality integrating capacitor from S.T.C. polystyreneelements is described ; leakage and drift tests were very satisfactory. Pre-treatments of electrolytes and electrodes are discussed. Vanadium (V) isdetermined a t -0.128 V in acetate buffer and at +O-247 V in 2.0 M sulpliuricacid, in the latter with a relative standard deviation of 0.27 per cent.anda 95 per cent. confidence level result of (1-008 to 1.011) x 10-1 M comparedwith 1.012 x 10-1 M for a standard solution. Chromium(VT) suppresses allreduction at pH 4.0, and is reduced simultaneously with vanadium in sul-phuric acid. Manganese(VI1) is reduced to manganese(II1) in the first stepat + 0-7 V a t pH 3.5 and manganese(II1) and vanadium (V) are simultaneouslyreduced in the second step at -0.12 V. The separation of iron(II1) is possiblea t +O-9 V but impracticable; simultaneous reduction a t +0.25 V in 2.0 Msulphuric acid followed by re-oxidation of the iron(I1) a t + 1.0 V is reconi-mended.E. BISHOP and P. H. HITCHCOCKChemistry Department, University of Exeter, Stocker Road, ISxeter, EX4 4QU.Analyst, 1973, 98, 572-579.[August, 1973Potentiostatic Coulometric Determination of Vanadium, Vanadium -A Multi-channel Dispenser - Titrator - pH-statA rnulti-channel dispenser - ti trator - pH-stat with switch-selection ofreagents and reagent volume control and with a directly digital read-out isdescribed.A valve driven by a stepper motor is used to select reagents andas a coarse volume control. A drop generator dispensing - deflection mechan-ism is used as a fine volume control. The drop generator is also used to rejectautomatically to waste any reagent contaminated by previously dispensedreagent and, in the titration mode, to add various amounts of reagent tothe reaction mixture. The instrument gives outstanding precision (relativestandard deviation less than 0.2 per cent.over the range 0.5 to 7-0 ml) andlinearity (correlation coefficient Y = 0.999 over the ranges 0.01 to 1.0 and0.25 to 7-0 nil).DOUGLAS G. MITCHELL and KENNETH M. ALDOUSDivision of Laboratories and Research, New York State Department of Health,Albany, New York 12201, U.S.A.Analyst, 1973, 98, 580-584.A Modified Field Test for the Determination of CarbonDisulphide Vapour in AirAn improved and more sensitive method is described for the determinationof carbon disulphide vapour in air a t concentrations up to 40 p.p.m. V / V .Carbon disulphide vapour is absorbed from a 500-ml sample of air into anetlianolic solution containing copper(I1) acetate, diethylamine and triethanol-amine. The yellow colour produced is compared visually with standardcolours or measured spectrophotometrically.For field use, the apparatus isportable and simple to operate, and requires a working time of about 5 minutesper determination.E. C. HUNT, W. A. McNALLY and A. F. SMITHDepartment of Trade and Industry, Laboratory of thc Govcrnnicnt Chemist,Cornwall House, Stamford Strcet, London, SE1 9NQ.Analyst, 1973, 98, 685-592August, 19731 SUMMARIES OF PAPERS I N T H I S ISSUEDetermination of the Antioxidant: 1,3,5-Trimethyl-2,4,6- tri(3’,5’-di- t- butyl- 4’- hydroxybenzy1)benzene in Feeds1,3,5-TrimethyI-2,4,6- tri (3’, 5’-cli- t-buty!-4’-liydrox?ibcnzyl) benzene (Ion-ox 380) is an antioxidant that is uscd for the prcscrvation of plastic foodwrappings. Its use as a fat stabiliser could Le extended to animal feeds.By using the method described, 200 p.p.m.of Ionox 330 in a feed can bedetermined with good reproducibility. The mcthod consists in extractingthe Ionox 330 with chlorofornl, purifying i t by using thin-layer chromato-graphy, and measuring a t 522 nm the colour developed in the presence ofiron(l1 I) chloride and 2,2’-bipyridyl. Possible interference from 2,G-cli-t-butyl-p-cresol (butylated hydroxytoluene; BHT) can be avoided by using this chroni-atograpliic technjque.G. F. BORIESStation Centrale de Nutrition, Centre National de Recherches Zootechniques,78- Jouy-en- Josas, France.Analyst, 1973, 98, 593-595.The Determination of Lead in Foods by Atomic- absorptionSpectrophotometryRapid procedures for the determination of lead in foods by an organicextraction technique and atomic-absorption spectrophotometry are described.The food sample can be dry ashed or digested by using sulphuric acid andhydrogen peroxide. In the latter instance, digestion need not be complete.Lead is extracted from acidic solutions (either the dissolved ashes or theresidual solution after acid digestion) into xylene as its dicthylamnioniumdiethyldithiocarbamate chelate, and then determined by use of atomic-absorption spectrophotometry .Large amounts of iron and tin do notinterfere in the determination. In a 10-g sample, 0.02 p.p.m. o€ lead canbe detected. The standard deviation in the range froni 0.2 to 1.0 p.p.m. oflead is about 0.02 p.p.m. Certain products do not require preliminary diges-tion; in these instances lead is extracted directly from the acidified sample.Liquids, beverages and many canned foods can be nionitored very rapidlyin this way.The chelate - solvent combination used in this method is moreconvenient than the ammonium tetramethylenedithiocarbamate - isobutylmethyl ketone system. The method is applicable also to metals other thanlead ; its use for cadmium has been demonstrated successfully.R. K. ROSCHNIKNest16 Products Technical Assistance Co. Ltd., Control Laboratory, Case Postale 88,Ch-1814, La Tour-de-Peilz, Switzerland.Analyst, 1973, 98, 596-604.A Critical Study of Safranine 0 as a Spectrophotometric Reagent :a Rapid Method for the Determination of Trace Amounts ofAntimony in SteelThe behaviour of Safranine 0 (Basic red 2, C.I.50240) in aqueous solutionsbas been invcstigated and its suitability as a spectrophotonietric reagent iscvaluated and discussed. ,4 rapid method for the determination of antimonyas a hexachloroantimonate(V) ion-association complex with Safranine 0 isdescribed. This complex is extracted into benzene and is determined spectro-photometrically. The method is as sensitive and reproducible as the Rhod-aniine B method but it has the advantage that the determination can becarried out directly on solutions of steel without prior separation. Goodagreement was found with standardised antimony values for five BritishChemical Standards’ steels.C. BURGESS, A. G. FOGG and D. THORBURN BURNSDepartment of Chemistry, University of Technology, Loughborough, Lcicestershire,LEll 3TU.Analyst, 1973, 98, 605-609...V l l l THE ANALYST [August, 1973SPECIALIST ABSTRACTJOURNALSpublished bySCIENCE AND TECHNOLOGY AGENCYAtomic Absorption and FlameEmission Spectroscopy AbstractsVol.5, 1973, bimonthly S30X-Ray Fluorescence SpectrometryAbstractsVol. 4, 1973, quarterly €28Thin-Layer Chromatography AbstractsVol. 3, 1973, bimonthly €28Gas Chromatography-MassSpectrometry AbstractsVol. 4, 1973, quarterly €37Nuclear Magnetic ResonanceSpectrometry AbstractsVol. 3, 1973, bimonthly S30Laser-Raman Spectroscopy AbstractsVol. 2, 1973, quarterly it30X-Ray Diffraction AbstractsVol. 1-2, 1973, quarterly €30Neutron Activation Analysis AbstractsVol. 2-3, 1973, quarterly €30Electron Microscopy AbstractsVol. 1,1973, quarterly €30Liquid Chromatography AbstractsVol. 1, 1973, quarterly €30Electron Spin Resonance SpectroscopyAbstractsVol. 1, 1973, quarterly €30Sample copies on request from:SCIENCE AND TECHNOLOGY AGENCY,3 HARRINGTON ROAD,SOUTH KENSINGTON,LONDON, SW7 3ES01-584 8081INDI-TABSTablets of pre-mixed chemicals. A simpleand economical way of adding indicators toyour titration flask.One hundred tablets each of twelve differentindicators are contained in each of two kitsfor titration of Aluminium, Bismuth,Cadmium, Calcium, Cobalt, Copper, Magne-sium, Nickel, Zinc, etc. etc.Details on request from:-RIDSDALE & CO. LTD.suppliers of “Analoid” compressed chemicalreagentsNewham Hall, Newby,Middlesbrough, Teesside, TS8 9EATel. Middlesbrough 0642 37216Why not use“COLLOID TITRATION”for simple and rapid determination ofCOLLOID PARTICLES in the field ofAgar and Alginic Acid IndustryLeather IndustryFood IndustryPaper and Pulp IndustryS u rfactant I n d u st ryWater Treatmentfor detailed brochure and reagentswrite soon to-DOJINDO CO., LTD.Research LaboratoriesP.O. Box 41, KumamotohigashiKumamoto (862)JAPANTel ex-7627-76 D 0 J I N