Analysis of Copper and its Alloys PDF
Preview Analysis of Copper and its Alloys
Analysis of Copper and Its Alloys W. T. ELWELL Chief Analyst, Imperial Metal Industries (Kynoch) Limited and I. R. SCHOLES Technical Officer, Imperial Metal Industries (Kynoch) Limited PERGAMON PRESS OXFORD * LONDON · EDINBURGH · NEW YORK TORONTO · SYDNEY · PARIS * BRAUNSCHWEIG Pergamon Press Ltd., Headington Hill Hall, Oxford 4 & 5 Fitzroy Square, London W.l Pergamon Press (Scotland) Ltd., 2 & 3 Teviot Place, Edinburgh 1 Pergamon Press Inc., 44-01 21st Street, Long Island City, New York 11101 Pergamon of Canada, Ltd., 6 Adelaide Street East, Toronto, Ontario Pergamon Press (Aust.) Pty. Ltd., 20-22 Margaret Street, Sydney, N.S.W. Pergamon Press S.A.R.L., 24 rue des Écoles, Paris 5 Vieweg & Sohn GmbH, Burgplatz 1, Braunschweig Copyright © 1967 Pergamon Press Ltd. First edition 1967 Library of Congress Catalog Card No. 66-28406 PRINTED IN GREAT BRITAIN BY BLACKDE AND SON LTD., BISHOPBRIGGS, GLASGOW 3095/67 ACKNOWLEDGMENTS THE authors acknowledge the assistance given by H. Pugh, R. T. Clark, W. R. Waterman and other members of the Analytical Section of Research Department, Imperial Metal Industries (Kynoch) Ltd., who have been associated with developing or proving the procedures contained in this book. Due acknowledgment is also made to Mrs. C. J. Lewis for typing the manuscript. ix PREFACE THE publication of any book should only be considered after a careful assessment of publications already available on the same subject has been made, and would-be authors must be reasonably satisfied that any new book will fill an outstanding need. Publications are available on the analysis of copper and related products,[1'2'3'4] but it is surprising how often serious practical difficulties are encountered especially in co-operative work with external laboratories. In view of the wide experience of analysts within Imperial Metal Industries (Kynoch) Limited (formerly ICI Metals Division), the publication of a book dealing with up-to-date procedures for the analysis of copper-bearing samples, based on first-hand experience, appears to be justified. The recommended procedures are those currently used in IMI laboratories, and have either been developed or had their reliability confirmed in the Company's Research Department. Modern trends in analysis are towards instrumentation, because improvements in speed, accuracy and precision are thereby invariably achieved, often with a saving in man-power. Thus, it is commonplace within large companies in the non-ferrous metal industry, where X-ray fluorescence equipment is used, for samples to be delivered to the laboratory via a despatch tube, and analytical data to be available within minutes of receipt of the sample. To anyone unfamiliar with this form of analysis it might appear that this is almost the last word in analytical control, but with all the undisputed advantages of X-ray fluorescence and emission spectro- scopy, the need to provide chemical procedures for determining some constituents still remains. Further, the demand for sensitive and highly accurate procedures for the provision of standards, an essential feature of most instrumental methods of analysis, has become more important. xi xii PREFACE In any organisation the choice of a particular procedure is largely dictated by the number of samples to be analysed and, where this is not sufficient to justify expensive instrumentation, rapid routine chemical procedures have to be devised. In some organisations, chemical procedures have been unaltered for many years, but all methods should be re-examined periodically. In this respect alone some sections of this book may be helpful, because a technical preamble to each determination is given, although a background knowledge of the chemical and physico-chemical principles involved has been assumed. Analysis of Copper and Its Alloys is intended as a laboratory compendium, containing essential information for the satisfactory analysis (chiefly chemical) of typical industrial products, rather than a treatise on the analytical chemistry of copper or any of its alloying constituents. For more detailed information, the reader is occasion- ally referred to other publications, although the selected list of over 200 references is not claimed to be a complete bibliography of the subject. For most determinations more than one procedure is given, and the uses and limitations of each are indicated in the preamble. These details will serve as a guide in making a choice between a rapid procedure and one that is intended to provide results of the highest accuracy without undue regard to the time involved. Whilst the Company has made many contributions to analytical chemistry, and published such information externally, no originality is claimed for some of the work described in this book, because many of the principles are of long standing, and full advantage has been taken of the work of other analysts. However, where it has been considered necessary to perpetuate the use of old-established procedures, these have been brought up to date in the light of experience and current analytical knowledge. This book does not contain any detailed information on the use of some of the instruments used by IMI on a large scale, e.g., the spectrograph and X-ray spectrometer. Although several instru- mental methods of analysis have been included, these involve the use of instruments that are commonplace, even in small laboratories, and it is appreciated that some of the instrumental techniques described for a particular determination are capable of a much wider application. For example, four typical atomic-absorption spectrophotometric procedures were chosen for inclusion in the PREFACE xiii book; others are omitted because operational details are very similar, provided that the appropriate hollow-cathode lamp and correct wavelength are used. Hence, where simple colorimetric procedures are available, these have been included, although many of these determinations can also be made by atomic absorption. Irrespective of the determinations to be made on any sample, a knowledge of the copper content is frequently required, because copper can be determined with a very high degree of precision, and an accuracy that is not paralleled by the determination of the parent metal of any other metallurgical product. The electro-deposition of copper is the basis of several procedures, and it is also a useful precursor to the subsequent determination of certain other metals. These factors justify dealing with the determination of copper first; thereafter, elements are dealt with in alphabetical order. All procedures described must be used in strict conjunction with Chapters 1 and 2, dealing with "Sampling" and "General Informa- tion" respectively. In this way it has been possible to present the relevant analytical information without unnecessary duplication, in what is hoped is a simple, clear and unequivocal style. Research Department Imperial Metal Industries (Kynoch) Ltd. Witton, Birmingham 6 February, 1966 CHAPTER 1 SAMPLING THE reason for including a section on sampling is not to advise the reader on ways and means of obtaining a representative sample, because this information is dealt with in more detail elsewhere, [1,1 1.2,1.3] threar j-0 stress the importance of sampling in all its implications, and to highlight some of the more important con- siderations involved. Several factors are common to most methods of sampling copper- base materials, irrespective of the quality or quantity of material to be sampled. For example, it is usual practice to remove extraneous matter, first with a wire brush, then with a soft brush. The degree of brushing, however, must be considered in relation to the nature of the surface. With cathode copper, for example, care must be taken not to remove any loose material; this may have a high impurity content, and its removal would make the sample less representative of the material to be used in the furnace charge. Cathode sheets should be carefully examined for surface imperfec- tions, i.e., heavy nodular deposits and stains. A representative number of sheets should be taken, and from each should be cut out, along its width, strips weighing about 201b each. The individual strips are then cut into pieces of smaller size for subsequent re- melting and casting as an ingot. Re-melting of sampled material in this way ensures the provision of a homogeneous sample, but it must be appreciated that any advantages gained by this method of sampling will be off-set by the extent to which the material undergoes compo- sitional changes during melting. Cutting tools must be clean and sharp, and used at low speeds to minimise oxidation of the turnings or drillings; if iron is to be determined the use of a tungsten carbide tipped drill is advised. Lubricants must be used only when absolutely necessary. All sampled material must be cleaned with a solvent to remove oil, grease, surface contaminants, etc., then dried in air. Extraneous iron ι 2 ANALYSIS OF COPPER AND ITS ALLOYS is best removed by a magnet, but this does not remove iron smears, and all samples to be analysed for iron must be washed in acid. Ideally, the sample for analysis should consist of small pieces about 2 to 3 mm long and 1 to 2 mm thick, and be of reasonably uniform size. Solid (massive) samples are preferred when the material is to be examined for gas content (or analysed spectrographically). Long drillings should be clipped into smaller pieces to ensure intimate mixing of the sampled material, which can then be reduced to a convenient size by coning and quartering. Where the presence of a significant amount of very fine particles is unavoidable, the material should be sieved and proportionate weights of the two fractions taken for analysis. Large ingots and slabs are most conveniently sampled by drilling, say five 0-5-inch diameter holes, completely through the thick- ness of the material at equally spaced intervals along a diagonal line; small ingots or bars should be sampled at similar points, by sawing completely through the material at right angles to the longer axis. To provide a representative sample, swarf from sawings can be collected, or the cut face may be milled. When sampling a large consignment of ingots, a representative number of ingots should be selected, one quarter of the length of each cut off, and the sawings or millings used as indicated earlier. Tube, plate or strip should be sampled in a plane at right angles to the long axis, and sheet at angles up to 45° to the direction of rolling. Thin sheet is usually clipped. Finished material should be sampled at positions representing the whole cross-section of the specimen and include sections of all thicknesses. Where possible, wire should be sampled at intervals along the length or, failing this, at both ends. Chill-cast samples are taken during the melting operation or during the subsequent pouring, depending upon the composition of the material. Even when the sample is chilled very rapidly, some segregation may occur, for example with cupro-nickel, and it may be necessary to resort to heat treatment in order to provide a homogeneous sample. The geometry of the mould is not significant when samples are taken for chemical analysis, but when certain physical methods are used, special attention to detail is necessary, e.g., in X-ray fluorescence and spectrographic analysis. CHAPTER 2 GENERAL INFORMATION IN PRESENTING the information contained in this publication, it is assumed that the reader is fully conversant with the safety pre- cautions pertaining to the handling of reagents, apparatus, etc. On such matters as nomenclature and abbreviations, due cognizance has been taken of the recommendations of the British Standards Institution^2,]1 and the Chemical Society. [2,]2 The use of proprietary names has been kept to a minimum; these include Anhydrone (anhydrous magnesium Perchlorate), Carbosorb (a self-indicating soda-asbestos absorbent) and Drikold (solidified carbon dioxide), but alternative brands may be equally satisfactory. Most books dealing with gravimetric analysis contain information on the care and attention necessary during the drying and ignition of filter papers and filter pads, and this information is not repeated here in detail. It is emphasised, however, that filter papers and filter pads, including the material filtered off, must be well dried, and the paper charred at a conveniently low temperature (less than 500°C) before the final ignition. The container should be provided with a loose- fitting lid, and the paper must not be allowed to inflame and cause mechanical loss of the precipitate. Filter papers used in the recom- mended procedures are 11-12-5 cm diameter, unless an alternative size is given. Filter pads are made from filter-paper clippings pulped with water in a stoppered container. The use of distilled water is implied, except where this is obviously unnecessary. Dilutions must be made with cold distilled water, unless otherwise stated. All solutions must be mixed during or, where appropriate, after any addition or dilution; any necessary temperature adjustment is made at the appropriate stage. Only analytical grade reagents of the highest quality must be used. Where the use of copper is recommended, it must be of a high- purity grade. In blank determinations, the copper must be as free as possible from the element being determined. 2 3 AOC 4 ANALYSIS OF COPPER AND ITS ALLOYS Whenever possible a reagent-blank determination should be made concurrently with the analysis, and a suitable correction or compen- sation applied ; this is most essential in absorptiometric and Polaro- graphie determinations. Reagents must be selected to ensure that all blank values are as low as possible. In absorptiometric determinations, optical densities of solutions are measured at 20±1°C; water is used in the compensating cell, and the same cell (one of a pair) must always be used in the com- pensating position. The recommended wavelengths and cell sizes will serve as a useful guide in the preparation of calibration graphs, irrespective of the type of spectrophotometer used. As far as possible conditions should be adjusted so that the optical density of the test solution is within the range 0-15-0-75; in the preparation of calibra- tion graphs, this range should be slightly extended beyond these lower and upper limits. In most instances it will be obvious when weighings and volumetric measurements are to be made accurately, but where it is not obvious, particularly in volumetric measurements, the volume is specified, e.g., as 10-0ml, and an accurate measurement must be made. All volumetric measurements are made at 20°C. Polarographic potentials are quoted in relation to a mercury-pool anode. To provide a better appreciation of the limitation of the procedures described, the range over which the determination can be applied and the extent to which interfering substances can be tolerated, are given, but this information is only intended as a guide. Reproducibilities are quoted in the form of a standard deviation, obtained from the results of at least six determinations provided by two analysts. Standard deviations have been calculated from determined values and the following equation: (χ,-χ )2 + (x -x ) 2 + ...(x„-x ) 2 Standard deviation = 2 n-\ where x x, . . . x, are the determined values, x~ the mean of the l9 2 n determined values, and η the number of determined values. Detailed operational instructions are not given for the polaro- graph (Mervyn Modular Square-Wave), the spectrophotometer (Unicam), atomic-absorption equipment (Hilger and Watts,
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