摘要:

Analyst, March, 1968, Vol. 93, $9. 191-192 191 A Sample Holder Cover for Use in the Determination of Light Elements in Liquids and Powders by Vacuum X-ray Fluorescence Spectrometry BY K. G. CARR-BRION AND K. W. PAYNE (Warren Spring Laboratory, Stevenage, Herts.) A simple sample holder cover is described that permits the examination of volatile liquids and powders under vacuum in an X-ray spectrometer. THE determination by X-ray fluorescence of light elements in volatile liquids and in powders is complicated by the need to remove the air from the X-ray path. This is usually achieved by replacing it with helium, but it lacks the convenience of vacuum operation and requires modifications to standard spectrometers. With the more convenient vacuum operation, volatile liquids will boil and a risk exists with fine powders of having them blown around the sample chamber when the air is re-admitted.A simply made cap has been devised to fit standard Philips specimen holders, which allows the safe examination of such samples under vacuum. To make a cap, a sheet of 2-mm thick, low density polythene is suspended above a hot- plate until it clears. It is then rapidly placed on top of a sample holder, and a ring, with a diameter about 2 mm greater than the rim of the holder, pressed over it to a depth of about 1 cm. The polythene is allowed to cool and then levered off and trimmed. Finally, a pin of about 0.5-mm diameter is passed through the centre of the cap to produce a fine hole at about 45" (see Fig. 1). A B A = Cap B = Sample holder C = Pressing ring D = Pin hole Fig.1. Section of cap MODE OF OPERATION- In the case of liquids, when the vacuum is applied to the spectrometer the sample holder slowly evacuates through the pin hole until the pressure equals the vapour pressure of the liquid, when boiling should commence. However, because of the slow rate of diffusion through the pin hole, boiling is limited or does not occur. Evaporation is reduced to a level where quantitative measurement of X-ray intensity can be made on the sample. The pressure on the supporting X-ray window will be only that of the vapour pressure of the liquid. There are, obviously, limits to the volatility of liquids that can be examined, and tests should first be carried out under vacuum outside the spectrometer. For powder samples, when air is re- admitted to the spectrometer it enters the sample holder slowly, thus preventing powder from being blown around the instrument.0 SAC; Controller, H.M. Stationery Office.192 CARR-BRION AND PAYNE RESULTS The capped holders, fitted with 12-p Propathene X-ray windows, were used to measure sulphur in aqueous solutions and chlorine in ethanol. A Philips PW 1212 X-ray spectrometer was used, equipped with a P.E. crystal and a tungsten tube operating at 40 kV and 37 mA. A summary of the results is given below. Exposure time for 1 per cent. Kcc intensity, change in intensity, Sample counts per second minutes 1.0 per cent. of sulphur, as 1070 >3 0-7 per cent. of chlorine, as 1900 2 iron(I1) sulphate in water iron(II1) chloride in ethanol With aqueous solutions, the X-ray intensity is stable, even after several minutes’ exposure to the primary X-ray beam. However, with the more volatile ethanol, appreciable evaporation occurred after 2 to 3 minutes’ exposure. Thus, samples should only be exposed to the beam during the required measuring periods. Received June 26th, 1967

ISSN:0003-2654    

DOI:10.1039/AN9689300191

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

Analyst, March, 1968, Vol. 93, @. 193 193 Detection of Mowra Cake in Oil Cakes BY N. G. WAGLE (General Superinteizdence Co. (India) Private Ltd., Bombay, India) THE detection of adulteration in oil cakes is a common requirement in analytical laboratories, as several international contracts specify freedom from such adulteration. In India, which is one of the largest exporters of de-oiled cakes, mowra [mahua, Madhuca (Bassia) ZatifoZia Macb. Roxb. ; Madhuca (Bassia) Zongifolia Koenig Macb.] is sometimes used as an adulterant. The presence of saponins (mowrin) in mowra cake affords a convenient method for its detection provided, however, the saponins are isolated from the carbohydrates and other non- saponins in the cake, which are likely to cause interference. The haemolytic action of saponins on red blood corpuscles is specific, but this method is not suitable for adoption in all laboratories.A quick and sensitive method, based on the well known reaction between sapogmhs (mowric acid) and concentrated sulphuric acid, is described for the detection of mowra cake in oil cakes, such as those of groundnut, linseed and sesame. 0 SAC and the author.194 WAGLE [Autalysl, VOl. 93 EXPERIMENTAL Ten grams of the sample, after de-oiling with light petroleum (boiling range 40" to 60" C) and air-drying, are refluxed with 200 ml of 5 per cent. w/v hydrochloric acid for 30 minutes and filtered, while hot, through a Buchner funnel fitted with Whatman No. 1 filter-paper. The residue is washed several times with hot water until the washings are colourless (6 to 8 times is sufficient), followed by acetone and diethyl ether. After drying in an air-oven a t 105" C, the residue and the filter-paper are transferred into a flask, 100 ml of isopropyl alcohol added, and the contents refluxed for 2 hours on a boiling water bath.The solution is filtered while hot, and evaporated to dryness on a steam-bath. The extract is boiled for 2 minutes with 10 nil of 5 per cent. w/v trichloroacetic acid solution, cooled and boiled again with 15 ml of 5 per cent. w/v sodium hydroxide for a further 2 minutes. The solution is cooled, diluted to 25 ml with water, and filtered. The filtrate is tested by adding 5 drops (0.2 ml) to about 5 ml of concen- trated sulphuric acid contained in a test-tube, by allowing the drops to run down the side of the tube.The formation of a violet ring a t the interface indicates the presence of mowra cake. At concentrations of 5 per cent. of mowra cake, and above, the violet-coloured ring is formed almost instantaneously, and is intense. At higher concentrations the colour assumes a violet - red hue. At lower concentrations, the development of the colour is gradual but it is distinct (purple or reddish orange) in about 30 seconds, although less intense. The intensity gradually increases and attains a maximum within about 1 hour. With cakes free from mowra cake, the ring is almost colourless or light yellow to light yellowish brown. The intensity of the colour is almost proportional to the amount of rriowra cake present and would serve as a means of determining it quantitatively. The test proposed in this paycr was always found to give a positive reaction with cakes containing as little as 0.5 per cent. of mowra cake. With suitable modifications, such as reduction of the final volume to 10 ml, instead of 25 nil, the test would respond even at lower concentrations. For a routine analytical laboratory this could be regarded as sufficiently sensitivc. First received Noiienaber 28th, 1966 Amended March 6th, 1967

ISSN:0003-2654    

DOI:10.1039/AN968930193b

出版商:RSC    

年代:1968

数据来源: RSC

摘要:

194 [Autalysl, VOl. 93 Book Reviews PARTICLE SIZE ANALYSIS. Pp. viii + 368. London: The Society for Analytical Chemistry. Price 147s. net (plus 5s. postage and packing); $18.25 net (plzis $0.75 postage and This book records the Proceedings of a 3-day Conference on the title subject, organised by the Society for Analytical Chemistry, held at Lougliborough University of Technology in September, 1966. There were over 200 delegates to the Conference from thirteen countries. Seventy-four variants of six basically different methods of size analysis were discussed in twenty-seven papers, but by far the most important part of the Conference was the excellent discussion, in which all facets of the subject were probed. A most important point is that all of those taking part in the discussions were actively engaged in some particular branch of the field under review, either as users, developers or makers of equipment.As this review concerns the book rather than the Conference, let me say at once that the volume is extremely well printed and edited. The illustrations are uniformly produced, and very clear, and the tabulation avoids this particular reviewer’s btte noire, tables that run on to two pages, often in reduced type-size, and sometimes printed by a different process from the main text, giving an untidy set-up, difficult to assimilate into the text. In fact, the only reduced-size printing is in the discussion, and this greatly adds to the ease with which the book can be read, as the reader is at once aware, at any point in the book, whether he is reading the main text or the discussion.With discussions that are sometimes as long as the original papers, this is a valuable advantage. The subject matter dealt with in the 360 pages of the book covers the whole field of size analysis, including optical methods (curiously described as “manual’, methods !) , automatic counting, gravity and centrifugal sedimentation methods, and surface measurement. A chapter 1967. packing).March, 19681 BOOK REVIEWS 196 is also included on applications of particle-size analysis, but this is regrettably short, dealing only with two rather specialised applications (in the ceramic and atomic energy fields). This is a pity as many would-be readers of the book will perhaps be mainly concerned with the ways in which accurate particle-size data can be used to improve the control and efficiency of the very many important processes that involve small particles.The reviewer is glad to see that not too much time has been devoted to argument concerning the statistical accuracy of the various methods of size analysis (particularly microscopic counting) ; instead, a considerable body of accurate test data is put forward for review and criticism. It has long been the writer’s view that equipment makers are too often prone to devote time and energy to elaborate instrumentation of equipment that is basically wrong (either because i t operates under conditions that invalidate the fundamental physical laws under which it purports to operate, or because the makers have not been entirely clear which parameters they seek to measure).In this Conference, the makers and the assessors have come face to face, and the ensuing discussions, so admirably reported in the book, cannot but be of immense value to would-be users, either experienced or novice. The latter should not be daunted by the apparent differences of opinion expressed. The book is not a “popular” treatise on the subject; it is a reasoned presenta- tion of scientific investigation, and, issued under the authority of the Society for Analytical Chemistry, deserves to be well regarded. Read in conjunction with the review paper on “Classi- fication of Methods for Determining Particle Size,” published in The Analyst, 1963, 88, 156), it provides a very valuable summary of present day development of this important field of analytical chemistry.The cry is raised a t several points that all of this has been done before. It has-the reviewer was himself a little sad to see that some of the early “milestones” had toppled, but indeed this is progress. The very important thing is that the principles enunciated in the early work, namely, that we must define precisely what we are trying to measure, and follow up with accurate cross- checking, either by ringing the changes on the type of apparatus, or by carefully preparing multi-model test samples, have been retained. In any case, it was time for another Conference: it is nearly 30 years since Dr. Heywood presented his masterly paper on the measurement of the fineness of powdered materials to the Institution of Mechanical Engineers (PYOC.Instn Me&. Engrs, 1938, 140, 257), and 20 years since the Institution of Chemical Engineers held its Symposium on Particle Size Analysis (“Symposium on Particle Size Analysis,” The Institution of Chemical Engineers, London, 1947). The Proceedings of this Conference was a “best-seller” and, in fact, should still be read in conjunction with the present volume. Closely associated as the reviewer was with the early work, he is happy to say that the present book is even better. Although its price is high (7 guineas), it represents the distillation of thousands of pounds’ worth of work, done under the best possible conditions, and will provide a satisfactory vade mecum for at least a decade, by which time one can expect that the application side will have developed to the extent that automatic determination of particle-size analysis will play an important r81e in computer control of the ever-larger unit process now becoming a common feature of our industry.This book will provide a good introduction to the techniques likely to be involved, and should be on every chemical engineer’s and chemist’s bookshelf. C. J. STAIRMAND PAPER CHROMATOGRAPHY AND ELECTROPHORESIS. Volume 1. By GUNTHER ZWEIG and JOHN R. WHITAKER. ELECTROPHORESIS IN STABILIZING MEDIA. Pp. xiv + 420. New Yorlr and London: Academic Press. 1967. Price 132s. This is the first volume of a comprehensive two-volume work on paper chromatography and electrophoresis in stabilising media, intended to supersede the well known “Manual of Paper Chromatography and Paper Electrophoresis,” by R.J. Block, E. L. Durrum and G. Zweig, the second edition of which appeared in 1958. The rapid advances in this field since then made a complete revision and a great expansion of the text imperative. The inclusion of many stabilising media, other than paper, and the extension of applications of the technique to a much greater variety of compounds than before, largely account for the size of the present volume. The opening chapter deals with theoretical considerations, types of stabilising media, apparatus and basic techniques, including application of sample, detection of components and quantitative196 BOOK REVIEWS [Analyst, VOl. 93 analysis. Although written in a style its economic and concise as possible, there is sufficient infor- mation on each topic to enable the reader to acquire a good understanding of the pertinent theories and facts. The following six chapters cover all the important applications, dealing systematically with a great variety of compounds, such as amines, amino-acids, peptides, proteins, nucleic acids and derivatives, carbohydrates, organic acids, alkaloids, antibiotics and steroids.The final chapter, describing the electrophoresis of inorganic ions, is particularly useful in drawing attention to a surprisingly little used, yet potentially very powerful, method. The references throughout the book are well up-to-date and the indexes quite satisfactory. It can be confidently predicted that this volume, competently written and well endowed with suitable diagrams and tables, will form a welcome addition to every chemical library.D. GROSS ADVANCES IN ELECTROCHEMISTRY AND ELECTROCHEMICAL ENGINEERING. Volume 5. Electro- chemical Engineering. Edited by CHARLES W. TOBIAS. Pp. xii + 325. New York, London and Sydney: Interscience Publishers, a division of John Wiley & Sons Inc. 1967. Price 116s. The fifth volume of this series of books intended for the research worker is a worthy companion to the excellent ones already published. This volume bears the important sub-title “Electro- chemical Engineering” and contains five authoritative reviews of processes and properties that are, or are likely to become, of technological value. In the first review entitled “The Nickel Cadmium Cell,” by P. C. Milner and U.B. Thomas, there is a comprehensive survey of the scientific and technological information on all aspects of this important cell. Not only do the authors discuss the charge - discharge cycles of both elec- trodes, but also the properties of the electrolyte, and the design and construction of both open and sealed cells. The authors could well have treated the wealth of information more critically, but nonetheless the review remains of great value. J. Newman in “Transport Processes” deals with mass transport in electrolyte solutions in terms of the macroscopic theory of electrolytes, but although the subject is worked through in vector notation, it is well written and can be easily read and so provides a very thorough basis for the solution of important diffusion problems in dilute and concentrated electrolytes.In their review of “The Transport Properties of Fused Salts,” G. J. Janz and R. D. Reeve tabulate the most reliable data for density, electrical conductivity and viscosity, together with electrical transport and self-diffusion data for many single molten salts, some binary and a few ternary mixtures. All of the data for single salts are analysed in terms of the most generally acceptable equation for each property. The tables, which constitute the bulk of the review, are prefaced by a critical and well referenced account of methods of measurement, and a brief treatment of the basic concepts of fused-salt electrolytes. A. Brenner, in a review entitled “Electrolysis of Non-aqueous Systems,” may mislead the reader, as he deals almost exclusively with the electrodeposition of metals from organic solutions. Although the review summarises the literature, there is no attempt to support the phenomeno- logical approach with any basic principles, and seldom is there any mention of any property apart from electrodeposit quality. This review has become a rather boring catalogue. The final review, “Electrodeposition of Alloys,” by K. M. Gorbunova and Y. M. Polukarov, is an excellent account of the theoretical basis of the subject, bearing in mind that there is already a review of the practical aspects, which was published in 1963 (A. Brenner, “Electrodeposition of Alloys”). The authors have treated the subject carefully and have drawn several interesting conclusions concerning the structure of electrodeposited alloys. This book should prove invaluable to workers in any of the fields reviewed, but its general interest to analysts must, of necessity, be limited. Like so many specialist publications its price seems unreasonably high. R. D. GILES

ISSN:0003-2654    

DOI:10.1039/AN9689300194

出版商:RSC    

年代:1968

数据来源: RSC