Potentiometric water analysis

Elecrrochumca

Acta, Vol 37, No

I I, pp 2103-2104,

1992

mnted I” cmt antaln

0

0013-4686/92 SS 00 + 0 00 1992 FWgamon PM Ltd

BOOK REVIEW POTENTIOMETRIC

WATER ANALYSIS

By D MIDGLEY and K TORRANCE

In the preface to this second edition, the authors make an astute observation and Indicate a dlsappomtment They point out that many hundreds of papers have been pubhshed m the past 12 years, dedicated to this or that electrode’s attnbutes and hmltatlons but only a few types have led to new electrodes Over the decade since the first edltlon one m&t have assumed that some space may have been gven to Chem Fets and the like but these are wholly omitted Presumably thus 1s due to the almost non-appearance commercially of these devices or because claims are still made for these laboratory curlosltles that they are not basically potentlometnc devices Thus this book IS devoted to readily available and well proved ISEs and their methods of use, although a number of newer systems are Included The authors’ stated alms are to make the procedures as clear as possible and to point out the advantages and hmltatlons of the electrodes themselves They must be complimented for their admirable achievement The work runmng to almost 600 pages 1s divided mto two parts, the first being devoted to electrochemical and analytical prmclples, general descrlptlon of vanous types of electrodes, measuring equipment, and extensive coverage of tltnmetrlc methods and general analytical practice The major, second part of the book concerns the specdic electrodes and the methods for determmmg about 50 chemlcal species The first two mtroductory chapters are concerned with units, relevant electrochemical prmclples stretching through to activity coefficients, ccl1 potentials, comments on sigmficance of reference electrodes and some sparse comments on hqmd Junction potentials m 10 sides or so A twe-e comment about “recent advances” m electronics and covenng the “now” seemmg ablhty to measure electrical potentials of a high impedance source (such as the glass electrode) sounds a little dated m the early 90s The first lines of Chapter Three suggesting that, and the reviewer quotes, “Modem ion-selective electrodes are membrane electrodes-m which the current IS camed by ions, but the classical metalhc electrodes with electromc rather than ionic transport are still useful for many purposes”, only adds further to the susplclon of obsolescence of the text Clearly m the decade since this the first edition some of the chapters m the “new” edlhon have not received very much attention A superficial statement that whatever the nature of the electrode, the electrode potential should reduce to the form of the Nemst equation at the same time quoting the somewhat non-thermodynanuc quantity “selectivtty” coefliaents for hqmd ion exchanger electrodes IS ambiguous The attempts of recent years to correct the Nernst equation wtth pseudo thermodynamics quantlt:a by the ad&tion of selectivity co&ctents to correct for divergence of the obvtously kmetlcally dlctated relationships has been severely cntlclsed and continues to be so Under the section dlscussmg membrane electrodes coverage 1s lpven for the various ionic hahde spectes,

thlocyanate, sulphlde, and sdver, copper, lead and cadmium as sulpludes However the reviewer questlons the general practice of calling a several mm tick matenal a membrane, for example, the ISE sulphtde electrode, which consists of a silver sulphlde 3 mm tick plug m contact wth a metal conductor Surely glass electrodes and certam ion exchange devices are membrane electrodes A membrane 1s a thm flexible solid sheet or film, a thm sheet-like structure! The glass electrode receives somewhat less attention than it deserves Inclusion of a paragraph on coated wire electrodes seems odd when they are nonthermodynamlcally reversible and not available commercially A followmg section called “mdlrectly selective electrodes” turns out to be. about gas sensmg membrane electrodes This chapter ends nicely however with a good section urlth plenty of detail on reference electrodes A chapter on equipment IS quite chatty and one gets the feeling that one IS obtammg from the authors’ text valuable mformatlon, the result of years of expenence of many types of instruments The mformatlon would be most useful to the mexpenenced and expenenced alike Advantages of microprocessors, dlgtal and analogue outputs, problems of matching and so on are well covered Problems with mdustnal momtonng equipment do not go unnoticed Automatic titration apparatus and flow mjechon analysis are discussed m detail with an emphasis on the use of microprocessors In Chapter Five analytical pnnclples, or treatment of data, are presented m a conventional manner on errors, I and F-tests, and correlation coeffiaents, but unfortunately without worked examples Potentlometnc titrations and related methods as well as the followmg chapter detailing potentiometric analytical prachce, function as precursors to Part II of the book These two chapters are probably the best m the book with clear descnptions and easy reading whch covers considerable ground effortlessly Included IS a detailed hstmg of aad-base, preclpltatlon, complexlmetnc, redox, and tltnmetnc procedures Equivalence point, gran plots and cahbratlon procedures are worked through, and problems and hmltatlons of the various types of titrations are also included Many general practical points too numerous to identify provide for all the background one requnes to apply the parttcular methods described m Part II There are even sections devoted to tracmg faults Part II IS excellent m its layout and the presentation of conctse detads ISthorough Each species determmabon cited commences with general comments about commercml avadablhty, their apparatus reqmrements, reagents con&homng and storage of electrodes, sample collection, concentraton range followed by analytical procedures, sources of errors, comparison wtth other methods and references The practtcal detail gvcn IS superb The very begmner could follow the step by step procedure details, even the most obvtous are mcluded A contents hst at the begmmng of Part II has the various electrodes and theu methods of use class&d by electrode type as well as alphabetic order Oddly however the run of sections of subsequent text IS netther, and to help the

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Book Review

reader avold nussmg items the revlewec suggests that the contents list situated at the begmmng of the book IS the more useful After sections dealing Hrlth measurement of pH and determmatlon of acldlty or alkalinity, covenng alkaline metals and earths, water hardness IS considered, plus a few transition and heavy metal electrode methods Gas sensing membrane electrode methods for carbon dloxlde, sulphur dioxide, oxide of nitrogen and ammonia are a useful mcluslon Many important anions mcludmg sulphlte, mtnte, sulphlde, habdes and tiocyanates are gven space The methods end with a section devoted to surfactant determmatlons, followed by an appendix of some 15 pages containing a nuscellany of information

References are mainly up to date and provide a useful source for further study The book IS aimed at those mvolved unth problems of momtonng the composltlon and concentration of chenucal species of source or discharge waters However, it must not be forgotten that the maJorlty of chemical species on the current proposed “hit” lists for the water industry are reqmred to be measured at concentrations at the ppb and sub ppb level In this respect most of the electrodes and methods discussed m this book are fundamentally unable to reach these levels being limited to ppm range and above Nevertheless the reviewer IS sure that the book will continue to be a chenshed laboratory reference book for years to come JVDCWWN