August, 1983 SUMhIARIES OF PAPERS IN THIS ISSUEIonic Polymerisation as a Means of End-point Indication inNon-aqueous Thermometric Titrimetry. Part XI. The ReactionMechanism of Iodimetric End -point Indication and an Evaluationof a Copolymerisation Indicator ReactionixThe mechanism of the reactions marking the end-point when ethyl vinylether is used as the indicator reagent in the thermometric titration of iodine-reactive analytes with solutions of iodine in dimethylformamide has beeninvestigated by capillary gas chromatography - mass spectrometry. Threemajor constituents, ICH,CH (OEt) CH,CH(OH) (OEt), I [CH,CH(OEt)],CH,CH-(OH) (OEt) and I[CH,CH(OEt)],CH,CH(OH)(OEt) have been identified,confirming the occurrence of a polymerisation process initiated by the iodoniumion.The hydroxy group in the molecules arises from the use of aqueousthiosulphate to terminate the polymerisation.An improvement in end-point sharpness using this catalytic thermometricprocedure is effected by using a mixture of ethyl vinyl ether and 1,3-dioxolaneas the indicator reagent instead of ethyl vinyl ether alone. The temperaturerise in this copolymerisation reaction is greater than in the ethyl vinyl etherhomopolymerisation, and the end-point inflection is sharper.Keywords : Non-aqueous thermometric iodimetry ; end-point indication ; ethylvinyl ether ; 1,S-dioxolane ; copolymerisationEDWARD J. GREENHOW and C. LOUIS JEYARAJDepartment of Chemistry, Chelsea College, University of London, Manresa Road,London, SW3 6LX.Analyst, 1983, 108, 991-996.Voltammetric Studies of Zomepirac Sodium and its Determinationin Tablets by Differential-pulse PolarographyA simple differential-pulse polarographic method has been developed for thedetermination of zoniepirac sodium in tablets.Britton - Robinson bufferof pH 1 1 0, containing 5:o I./ I’ of methanol, was employed as the supportingelectrolyte. The peak potential occurs a t - 1.50 V. Results obtained bythe proposed method are in excellent agreement with those provided by bothtlie official and tlie manufacturer’s methods of assay. It was found thatcommonly used tablet escipients did not interfere in the analyses.Keywords : Zomepirac sodzuiiz detewuination; dinerendial-pulse polarography ;controlled-potential coulowetvy ; cyclic voltnvlznzetry ; tabletsLESLIE G.CHATTEN, STANLEY PONS and LAWRENCE AMANKWAFaculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton,Alberta, T6G 2N8, Canada.Analyst, 1983, 108, 997-1002X SUMMARIES OF PAPERS IN THIS ISSUETransient Potential Shifts with pH Glass ElectrodesDue to Divalent CationsAugust, 1983The introduction of low concentrations of Cu2+, Ni2+, Co2+, Mn2+, Zn2+, Cd2+and Hg2+ salts into unbuffered aqueous solutions gave rise to transientpotential shifts with glass pH electrodes. These shifts mimic transitory pHdecreases in solution. Removal of the added cation gave rise to a transientpotential shift in the opposite direction. The relative order of magnitude dueto the added cations was studied.The quasi-pH shifts were shown to beparticularly serious in flow cells where the vigour of mixing was less andcould easily lead to the inipression that an actual pH transient had occurred.The effects were shown to be due to a surface action at the glass membrane.A possible mechanism is suggested.Keywords : pH glass electrodes ; divalent cations ; pow cell; transient potentialsCOLIN D. KENNEDYDepartment of Biochemistry, Physiology and Soil Science, Wye College, (Universityof London), Wye, Ashford, Kent, TN25 5 h H .Analyst, 1983, 108, 1003-1006.Influence of Instability of Thiocganate in Argentimetryand MercurimetryThe silver - thiocyanate and mercury(I1) - thiocyanate reactions have beenexamined by precise mass titrimetry for possible errors arising from decomposi-tion of thiocyanate in nitric acid media.For silver, potentiometric titrationin either direction in 0.15 mol kg-l nitric acid is free from error provided stepsare taken to overcome adsorption, but thiocyanate cannot be stored a t thisacid concentration. Using iron(II1) as the indicator, visual titration in theVolhard direction (thiocyanate titrant) is unaffected by time delay, acid con-centration and indicator concentration ; in the reverse direction an error of theorder of 0.5% is incurred and increases as time, acid and indicator concentra-tion increase. For mercury(II), potentiometric titration is unsatisfactory inboth directions. Standard mercury( 11) ion solutions hydrolyse in nitric acidless than 4.0 mol l-l, while thiocyanate is unstable in solutions contakingmore than 0.05 mol 1-1 of nitric acid.Neutral thiocyanate solution andmercury(I1) solution in 4.0 mol 1-1 nitric acid can be titrated in eitherdirection using iron(II1) as the indicator, but the precision is poor and timedelays are not tolerated. Higher indicator concentrations favour betterprecision through increased ease in locating the end-point.Keywords : Thiocyanate titrations ; Volhard titration ; mercury(II) - thio-cyanate titration; iron(III) - thiocyanate indicator; stability of mercury(II)ion and thiocyanate solutionsEDMUND BISHOP, DAVID DARKER, MICHAEL D. JONES, PAUL M.STEWART and SALAH M. SULTANChemistry Department, University of Exeter, Stocker Road, Exeter, EX4 4QD.Analyst, 1983, 108, 1007-1012xii SUMMARIES OF PAPERS I N THIS ISSUE August, 1983Flow Injection Analysis System for Determining Soil pHA flow injection analysis system is described for the determination of soilpH in filtered 0.01 M calcium chloride solution extracts. The system is con-structed entirely from off -the-shelf components and is capable of analysingup to 90 samples in 1 h.The unbuffered nature of filtered soil extracts causesproblems in terms of electrode response times and imposes restrictions onthe composition of the carrier-stream buffer and reference standards.Keywords : Flow injection analysis ; soil p HTONY E. EDMONDS and GRACE COUTTSThe Macaulay Institute for Soil Research, Craigiebuckler, Aberdeen, Scotland.Analyst, 1983, 108, 1013-1017.Rapid Spectrophotometric Determination of Nitrate with PhenolShort PaperKeywords ; Nitrate determination ; spectrophotometry ; phenol ; nitriteNOgL VELGHE and ALBERT CLAEYSLaboratory of Analytical Chemistry, University of Ghent, B-9000 Ghent, Belgium.Analyst, 1983, 108, 1018-1022.Iodimetric Micro - determination of Aliphatic Acids by aPotentiometric Titration Method and Comparison withAcid - Base PotentiometryShort PaperKeywords : Aliphatic acid micro-determination ; potentiometry ; iodate, iodideand sodium hydroxide reagentsANJOU WADHWA and RAJ MOHAN VERMADepartment of Post-Graduate Studies and Research in Chemistry, University ofJabalpur, Jabalpur 482001 (M.P.), India.Analyst, 1983, 108, 1022-1025.Determination of Nitrate in Lake Water by the Adaptation of theHydrazine - Copper Reduction Method for Use on a DiscreteAnalyser : Performance Statistics and an Instrument-inducedDifference from Segmented Flow ConditionsShort PaperKeywords : Nitrate determination ; hydrazine - copper reduction ; lake water ;discrete analyser ; flow injection analysisJOHN HILTON and ERIC RIGGFreshwater Biological Association, Windermere Laboratory, The Ferry House,Far Sawrey, Ambleside, Cumbria, LA22 OLP.Analyst, 1983, 108, 1026-1028