摘要:

118 Analyst, February, 1968, Vol, 93, pp. 118-120 An Improved End-point for the Determination of Fluoride with Thorium Nitrate BY WALTER SELIG (Lawrence Radiation Laboratory, University of California, Liveymore, California) The end-point for the titrimetric determination of fluoride with thorium nitrate has been improved by the use of methylthymol blue indicator. Up to 10 mg of fluoride can be determined in a solution buffered with glycine - per- chlorate at pH 3.35. THORIUM nitrate titration is probably the most commonly used titrimetric technique for the determination of flu0ride.l Alizarin red S is widely used as the indicator, but the end- point is not sharp. By using methylthymol blue as the indicator, in a solution buffered with glycine - perchlorate,2 the end-point has been considerably improved.EXPERIMENTAL REAGENTS- 11 ml of N perchloric acid and make the volume up to 100 ml. nitric acid and make up to 1 litre with 0.001 N nitric acid. (Fisher Scientijc Co., U.S.A.). PROCEDURE- The sample may contain up to 10 mg of fluoride and should be no larger than 15 ml if the indicator solution is used, or about 50ml if indicator tablets are used. The solution is acidified with N perchloric acid to pH 3.35 rfr 0.10 and 2 ml of buffer solution are added. Three drops of indicator solution or one indicator tablet are added, and the fluoride is titrated with thorium nitrate to a deep blue colour. The thorium nitrate is standardised against a known fluoride solution. B u f e r solution-Dissolve 6.7 g of glycine and 11 g of sodium perchlorate in water, add Thorium nitrate, 0.02 M-Dissolve 11.044 g of thorium nitrate tetrahydrate in 0-001 N Methylthymol blue indicator solution, 0-2 per cent.wlv, aqueous, OY Metab indicator tablets DISCUSSION AND RESULTS Thorium nitrate titration is one of the most commonly used titrimetric techniques for the determination of fluoride. The deficiencies of this method, such as its dependence on pH, its non-stoicheiometry, and the difficulties experienced by many workers in perceiving the equivalence point, have been well recognised.1 Kainz and Scholler2 have used a glycine - perchlorate buffer, which ensures stoicheiometry over the range of 1 to 10mg of fluoride. This has recently been confirmed in a critical investigation by Baumgartel and Spre~her.~ Methylthymol blue has been successfully used as an indicator in the titration of thorium with EDTA at pH 3, the end-point being a sharp colour change from blue to y e l l o ~ .~ ~ ~ We have used this indicator for the titration of up to 10 mg of fluoride with thorium nitrate in a solution buffered with glycine - perchlorate. The colour change at the end-point, from yellow to deep blue, is, in the author’s opinion, superior to any described previously for this titration. As the evaluation of colour changes of indicators is a rather subjective matter, the procedure outlined here was submitted to a panel of six analytical chemists at this laboratory. The methylthymol blue end-point was preferred by all of them to the Alizarin red S end-point and the other indicators discussed below.0 SAC and the author.SELIG 119 Schmidt and Ortloff6 recently suggested the use of a mixed indicator, xylenol orange and Chicago blue, for the titration of fluoride with thorium nitrate in a glycine - perchlorate buffered medium, claiming a colour change from brilliant green to violet. Their paper gives no details of indicator concentrations. We have done some work with this type of indicator. With 2 drops of a 0.2 per cent. w/v aqueous solution of xylenol orange and 1 drop of a 0.1 per cent. w/v aqueous solution of Chicago blue B, we found the end-point rather difficult to ascertain. Several other blue dyes at the same concentration were substituted for Chicago blue B. A poor end-point was obtained with China blue. Nile blue, methylene blue and Niagara Sky blue 4B, however, yielded sharp end-points, the last of these being preferred by the author.Another modification of the thorium nitrate titrimetric technique recently suggested by Oliver’ did not produce end-points as sharp as those resulting from our modification of Schmidt and Ortloff’s procedure. TABLE I TITRATION OF 2-525 mg OF FLUORIDE WITH VARIOUS INDICATORS Run No. 1 2 3 4 6 Average .. .. Standard deviation Fluoride found, mg L r Xylenol orange - Niagara Sky blue Alizarin red S 2-53 2-48 2.51 2-49 2.49 2.6 1 2.51 2-48 2.48 2.46 2.504 2.484 0.020 0.018 Meth;l- thymol blue 2-54 2-53 2.51 2.5 1 2.53 2.524 0-008 Results for the titration of a known amount of fluoride with thorium nitrate, with Alizarin red S, xylenol orange - Niagara Sky blue and methylthymol blue indicators, are shown in Table I.It must be pointed out that some operators are unable to recognise the Alizarin red S end-point, while others are unable to obtain good precision. The precision obtained with Alizarin red S (as expressed by the standard deviation) was similar to that for the mixed indicator, xylenol orange - Niagara Sky blue, while the accuracy was somewhat better for the former. With methylthymol blue, however, both precision and accuracy were significantly better than with the other indicators. TABLE I1 EFFECT OF BUFFER AND pH ON RECOVERY OF FLUORIDE (Fluoride taken, 2.525 mg) PH F Imtial 2.60 3-10 3.20 3-30 3.50 3.60 3.70 4.00 6-00 7 Final 2-48 3.04 3.15 3.27 3-42 3-52 3.63 3.94 4.85 Fluoride recovered, mg 3.12 Vague end-point 2-59 - 2-54 - 2.53 - 2-63 - 2-48 - 2.45 - 2.35 - 1.99 - Remarks Withozlt bu.ev- 2-60 2-35 3.34 Vague end-point 3.30 2-25 2-80 4-00 1-85 2-46 - 5.10 1.30 2-14 Vague end-point A study of the effect of buffer and pH on the recovery of a known amount of fluoride is summarised in Table 11.With glycine - perchlorate buffer, satisfactory recoveries are obtained120 SELIG if the final pH is between 3.15 and 3.42. This pH is achieved by an initial pH adjustment to 3-35 & 0.10, as outlined in the procedure. Without the buffer no satisfactory recoveries are obtained. Cations reacting with methylthymol blue interfere in the determination of fluoride. Interference from sulphur and phosphorus can be removed by the method recently outlined by Oliver. This work was carried out under the auspices of the U.S. Atomic Energy Commission. REFERENCES 1. 2. 3. 4. 6. 6. 7. Kolthoff, I. M., and Elving, P. J., Editors, “Treatise on Analytical Chemistry,” Part 11. Vol- Kainz, G., and Scholler, F., Mikrochim. Acta, 1956, 843. Baumgartel, E., and Sprecher, F., 2. Chemie, Lpz., 1964, 4, 341. Belcher, R., and Wilson, C. L., “New Methods of Analytical Chemistry,” Second Edition, Chapman Korbl, J., and Pzibil, R., Chemickd Listy, 1967, 51, 1061. Schmidt, J., and Ortloff, R., 2. Chemie, Lpt., 1965, 5, 236. Oliver, F. H., Analyst, 1966, 91, 771. ume 7, Interscience Publishers, New York and London, 1961, p. 259. and Hall Ltd., London, 1964, p. 46. Received il4arch 13th, 1967

ISSN:0003-2654    

DOI:10.1039/AN9689300118

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

Analyst, February, 1968, Vol. 93, $9. 121-124 121 Book Reviews SUPPLEMENT TO OFFICIAL, STANDARDISED AND RECOMMENDED METHODS OF ANALYSIS. Com- piled and edited by S. C. JOLLY. Pp. xiv + 424. London: The Society for Analytical Chemistry. 1967. Price 126s. This Supplement to the main book, which was published in 1963, contains in Part I additional methods recommended by the Analytical Methods Committee, and in Part I1 an entirely revised bibliography of Official, Standardised and Recommended Methods of Analysis covering forty-three sections with a very wide range of interests. The methods apply primarily to foodstuffs and agricultural products. As with the 1963 publication, the methods in Part I, covering 73 pages, are practical working methods that can be used at the bench, with complete confidence, as they have been exhaustively considered and tested by committees of experts in their fields, either A.M.C.sub-committees or joint committees with other learned societies or government departments. Some of the methods were developed by joint committees of the A.M.C. with the Association of British Manufacturers of Agricultural Chemicals, the Inter-Departmental Advisory Committee on Poisonous Substances Used in Agriculture and Food Storage and the Pharmaceutical Society of Great Britain. The A.M.C. has seen fit to retain the 1963 book, as there is little change in the recommended methods in Part I already published in the main book, and the additional methods in Part I of the Supplement have appeared in the Analyst between the beginning of 1963 and the end of 1966.Thus the 1963 volume retains its value and is supplemented by the new volume. It is unfortunate that in a review such as this, space will not allow the listing of the supple- mentary methods which, at the time of first publication, were needed in their particular fields as being authoritative. The new bibliography, occupying 313 pages, is exhaustive of Official and Standardised Methods, Tentative Methods and Recommended Methods in the individual subjects up to the end of 1966 and invaluable to any worker in the fields covered. There is a cumulative subject index of both the 1963 volume and the Supplement, which greatly assists consultation of both volumes. The format, printing and information given are in identical form familiar to owners of the earlier volume, being lucid, easy to follow and containing all relevant details needed to perform the operation on the bench, and the Supplement is well bound and attractively presented.The Analytical Methods Committee and the Editor are to be congratulated on a further publication of the high standard of the 1963 volume. One could wish that the names of members of sub-committees responsible for the various methods could be published, both to enhance the authority of each method and to enable workers in the same field to correspond with them, if desirable. H. E. BROOKES ANALYSIS OF COPPER AND ITS ALLOYS. By W. T. ELWELL and I. R. SCHOLES. Pp. xiii + 183. Oxford, London, Edinburgh, New York, Toronto, Sydney, Paris and Braunschweig : Pergamon Press.1967. Price 50s. The national bibliography of Metallurgical Analysis has long included specialised works on iron and steel, aluminium and magnesium, to which, within the last few years, have been added books covering titanium, zirconium, hafnium, niobium, tantalum and tungsten. There has, however, always been an outstanding gap in the literature, for there has been no compre- hensive work on the analysis of copper and its alloys written and published in this country. At last, however, this gap has been filled, and worthily filled, by Messrs. Elwell and Scholes, who should be well satisfied by the result of what must have taken much effort and hard work. For so slim a volume, the amount of information is considerable, but, as the authors state in the short preface, the book is intended as a laboratory compendium and not as a treatise on the analytical chemistry of copper or any of its alloying constituents.Chapter 1 contains some advice on the all-important subject of sampling, and this is followed in Chapter 2 by what is described as general information. This is designed to relieve the subsequent analytical methods from unnecessary repetitions and to explain the conventions and terms that are to be used. It includes definitions of the strength of some of the most commonly used reagents, such as the acids, and how certain specified reagents are to be made up.122 BOOK REVIEWS [Autalyst, VOl. 93 The preliminaries over, the next twenty-eight chapters are devoted to methods recommended for the determination of as many elements.The elements dealt with make a comprehensive list: copper, aluminium, antimony, arsenic, bismuth, cadmium, chromium, cobalt, iron, lead, man- ganese, nickel, oxygen, phosphorus, selenium, silicon, sulphur, tellurium, tin and zinc, being frequently required, are of course included, and in addition there are chapters on beryllium, boron, carbon, hydrogen, nitrogen, silver, titanium and zirconium (and hafnium). Pride of place is quite naturally given to copper because it is probably the most commonly determined element, can be determined precisely, and because the electrolytic separation is often used before determining other elements. After this the other elements follow alphabetically. The plan for each chapter is that i t opens with a general discussion of methods available and particularly of those that are to be recommended, and interferences in the determinations by other elements are given full attention.Thereafter, the recommended methods are given in detail. In some cases only one procedure is chosen, but in most several are quoted to cover various cases. The methods are well chosen, and it is pleasing to note that, in addition to gravimetric, volumetric and polarographic procedures, there are some in which the increasingly important atomic-absorption technique is used. The last three chapters consist of a table of atomic numbers and weights, a list of suppliers of reagents and apparatus and a list of references. There is, of course, the indispensable index. The volume seems gratifyingly free from mistakes and only one was noticed.This, an obvious typographical error, occurs on page 19, where the strength of a standard sodium thiosulphate solution is given as being 1 ml = 1.0 mg of copper (approx.) when indeed it should be 1 ml = 10.0 mg of copper (approx.) . This is a book which it is hard to fault, and on which the authors are to be congratulated. It should receive a ready welcome, particularly in those laboratories dealing with the analysis of copper and its alloys that will now have a specialised and essentially practical manual to help them in their work. J. B. PRICE THE CHEMISTRY OF NIOBIUM AND TANTALUM. By F. FAIRBROTHER, D.Sc., F.R.I.C. Pp. xiv + 243. Amsterdam, London and New York: Elsevier Publishing Company. 1967. Price 105s. Over the years following the second World War, increasing interest has been shown in the use of niobium and tantalum in the fields of nuclear engineering, high temperature technology and superconductors, and this has stimulated a study of the metallurgy of these metals and the chemistry of their compounds.The subject matter of this book should, therefore, meet certain outstanding needs, e.g., those of the chemist interested in the most recent developments and researches in these fields. The first chapter (8 pages) deals with Separation and Extraction Metallurgy, with a very short Chapter 2 on Physical Properties of the Metals. The main emphasis of the book, however, is in keeping with its title, and covers colloid chemistry, co-ordination compounds, variable valence, non-integral valence, compounds con- taining metal - metal clusters, and various aspects of solid-state chemistry.Many of the properties and chemical reactions of these two metals and their corresponding compounds are remarkably alike, yet some show distinct contrasts, and it is not surprising that the author deals with these two elements in parallel, in such a way as to emphasise their similarities and differences. Chapter 9, the final chapter, devotes about ten pages to a general survey of the analytical chemistry of these two elements, but this provides no more than a starting point for the analyst confronted with the difficult analytical problems that will be familiar to the expert in this field. W. T. ELWELL CHROMATOGRAPHIC METHODS. By R. STOCK, B.Sc., Ph.D., F.R.I.C., and C.B. F. RICE, BSc., F.R.I.C. Second Edition. Pp. viii + 256. London: Chapman and Hall Ltd. 1967. Price (bound) 42s. ; (paperback) 21s. This book is the second edition of the book first published in 1963. Naturally this book has been brought up-to-date and now contains sections on liquid ion exchangers, gel filtration and inorganic ion exchangers. A completely new chapter on thin-layer chromatography has also been included. Because of these innovations, the book is now very useful for students who wish to haveFebruary, 19681 BOOK REVIEWS 123 a general knowledge of the state of the art in chromatography without having to delve too deeply into specialised volumes or papers. However, the reviewer still feels that Chapter 4, on gas chromatography, is still very weak, because, in spite of the fact that this technique dominates all chromatographic methods at present, the chapter is dated and no attempt has been made a t revising it.This is, therefore, a book that can be recommended, but, with reservations, it should be available for students to read. G. NICKLESS CHEMISTS AND THE LAW. By F. A. ROBINSON, D.Sc., LL.B., F.R.I.C., and F. A. AMIES, B.A., F.C.I.S., F.R.V.A. Edited by H. M. BUKBURY, M.Sc., F.R.I.C. Pp. xx + 231. London: E. & F. N. Spon Ltd. 1967. Price 40s. The authors have set out to provide the chemist in industry with an outline of the various ways in which the law impinges on his activities. It is a very readable book with a blend of discussion and direct information. The subject matter is divided into two parts, that in which Common Law predoniinates and that in which Statute Law is of more consequence.Some chapters are more useful than others; contracts, contracts of employment and negligence in the first part, and factories, patents and copyright in the second portion of the book are of particular value. This is not a book to provide the answers to specific problems in law but rather one for reference, particularly as a pointer to the source of more detailed information. It is hoped that it is the intention of the authors to expand the subject matter in further editions. I t was surprising to find no mention of the Merchandise Marks Act. Comments on the Weights and Measures Act, which must affect product control in many trades, is another subject that would be of value. The bibliography and tables of cases, statutes and orders at the end of each chapter are most useful, and the book is worth recommending for the library shelf.D. C. GARRATT THE ANALYTICAL CHEMISTRY OF PROTACTINIUM. By D. BROWN and A. G. MXDDOCK. EXTRACTION REACTOR MATERIALS. By KENJI MOTOJIMA. THE ANALYTICAL CHEMISTRY OF ACTINIUM. By H. W. KIRBY. PROGRESS IN NUCLEAR ENERGY, SERIES IX: AKALYTICAL CHEMISTRY. Volume 8, Part I. Edited by H. A. ELION and D. C. STEWART. Pp. iv + 139. Oxford, London, Edinburgh, New York, Toronto, Sydney, Paris and Braunschweig : Pergamon Press. 1967. Price 45s.; $7.25. This part of volume 8, in the impressively titled series “Progress in Nuclear Energy (Analytical Chemistry),” contains three review articles on topics of widely differing interest to the chemist or the analyst.Sections I and I11 claim to deal with the analytical chemistry of two of the rarer actinide elements, protactinium and actinium. The second section, having a split title for brevity, deals with the application of extraction photometry with only two reagents, oxine and 2-methyl oxine, to the analysis of a range of possible nuclear-reactor materials for major and minor con- stituents. The authors of Sections I and I1 are conscious of the number of review articles written recently on these elements, and imply an apology for adding yet another. Although Section I on protac- tinium has attempted to be critical in its approach, based on the wide experimental experience of both authors, the usefulness to the analyst is not likely to be very great.The vitally important aspects of the analytical chemistry of protactinium, such as the establishment of the stoicheiometry of a compound, in particular Pa,O,, and the inconclusiveness of the electrochemical approach, are dealt with briefly. The book badly needs a section giving an assessment of the potential or actual usefulness of the many compounds mentioned for the determination of protactinium. In fairness, it has a useful reference section. Section I11 on actinium has a somewhat better layout than Section I, but again contains much material that is of little use to the analyst. Section I1 is very simply written, and has an easily understood layout. Unfortunately, the topics presented represent the work of only one laboratory, as shown by the reference section. Of the 37 references, 30 are to the work of this laboratory.The author has attempted to use just one technique and two reagents, with all the consequent limitations, for the analysis of a wide PHOTOMETRY USING OXINE AND 8-METHYL-OXINE-ANALYSIS OF ESSENTIAL NUCLEAR124 BOOK REVIEWS [Analyst, VOl. 93 range of materials. The section could well have been called “The poor man’s guide to the analysis of essential nuclear reactor materials.” It is unlikely that any other laboratory would wish to specialise to this extent, particularly as many of the determinations could have been carried out more easily by other methods. The book will undoubtedly find its way on to the shelves of many analysts of reactor materials, but it will not be used as much as it could have been, had the analyst been considered more when i t was written.A. J.FUDGE REAGENT CHEMICALS AND STANDARDS: WITH METHODS OF TESTING AND ASSAYING THEM; ALSO THE PREPARATION AND STANDARDIZATION OF VOLUMETRIC SOLUTIONS AND EXTENSIVE TABLES OF EQUIVALENTS. By JOSEPH ROSIN. Fifth Edition. Pp. viii + 641. Princeton, New Jersey, Toronto and London: D. Van Nostrand Company Inc. 1967. Price 132s. Few analysts interested in specifications will need any introduction to “Reagent Chemicals and Standards,” by Joseph Rosin, and the recently published fifth edition follows the format of previous publications. Specifications for some 580 reagents are included in the present edition, thirty of which are new, and it is almost certainly the most comprehensive set of practical speci- fications so far published.Many of the specifications are the same as those issued by the American Chemical Society in “Reagent Chemicals,” but in some cases minor modifications are noted, and one wonders whether these may forecast alterations in the now overdue next edition of A.C.S. “Reagent Chemicals.” As in the past, physical methods of analysis have, to a large extent, been excluded and for this reason the book must appeal to the small laboratory with the minimum of equipment. How- ever, a special chapter on flame photometry, by Dr. Theodore C. Rains of the National Bureau of Standards is included, and possibly points to the greater use of physical methods in the future. One might question the need for some twenty-five chapters of volumetric factors and gravi- metric equivalents, but one must not overlook the possibility of the work being consulted by junior assistants who may find the tables useful.While /3-naphthylamine has been excluded from the last two editions, it is a little surprising to find benzidine still described as a reagent “suitable for the detection of blood” without any indication of the now recognised carcinogenic properties of the compound. Storage conditions are given for a number of items, and it is felt that these could well have been supplemented, with some warning in the case of hazardous compounds. A. G. HILL CHROMATOGRAPHY. Edited by ERICK HEFTMANN. Second Edition. Pp. xlii + 551. New York: The book is envisaged as a survey of all branches of chromatography and electrophoresis for lecturers and research workers engaged or interested in this field.To achieve this end, the earlier edition (1961) has been brought up-to-date, with the consequent increase in size of about 100 pages and 1300 references. The contributors are forty distinguished scientists, and the book is divided into twenty-nine chapters. Although, in general, most of the titles of the chapters and contributors remain unaltered, there are nine new authors, and the original chapter in the first edition on Vitamins and Antibiotics has been separated into two chapters, one entitled Vitamins and the other Antibiotics. Obviously all of the chapters have been revised, often extensively. Other editorial changes are the elimination of the author index and a 3-fold increase in the subject index. The loss of the author index is a very small one, while the increase in accessibility of individual topics in the subject index overcomes earlier objections to the first edition. It is difficult to review this book in general terms because it reflects the multitude of interests of the contributors and the topics on which they work. However, it is felt that mention should be made of the chapter on electrophoretic theory by Wieme; this is a good critical survey of the field. Wieme has made a great effort to standardise the terminology of this field. Considering the diverse interests of the contributors, the style is noticeably uniform, which provides further confirmation of the outstanding calibre of the editor. The tables of RF values, solvent systems and details of individual techniques make the book an invaluable and useful guide for all. Whether or not individual owners of the first edition would consider purchasing this edition is open to debate, but as a general guide to the significant literature the book is unrivalled, especially if regard is given to the question of limitation of space. This book can, therefore, be recom- mended with no reservations and should be available in the library of every institute where chromatography is studied or used. Reinhold Publishing Corporation. 1967. Price kll. In this chapter, the term electrophoresis is chosen over electrochromatography. G. NICKLESS

ISSN:0003-2654    

DOI:10.1039/AN9689300121

出版商:RSC    

年代:1968

数据来源: RSC