Minerals and Rocks. P.1. Wyllie, Chicago, Ill. W. von Engelhardt, Tlibingen. T. Hahn, Aachen. Editor in Chief. Editors

Transcription

1 Minerals and Rocks 11 Editor in Chief P.1. Wyllie, Chicago, Ill. Editors W. von Engelhardt, Tlibingen. T. Hahn, Aachen

2 Werner Smykatz-Kloss Differential Thermal Analysis Application and Results in Mineralogy With 82 Figures Springer-Verlag Berlin Heidelberg New York 1974

3 Dr. Werner Smykatz-Kloss Mineralogisches Institut der Universitiit 7500 Karlsruhe/W. Germany Volumes 1 to 9 in this series appeared under the title Minerals, Rocks and Inorganic Materials Library of Congress Cataloging in Publication Data Smykatz-Kloss. Werner Differential thermal analysis. (Minerals and rocks, v. 11) Bibliography: p. I. Thermal analysis. 2. Mineralogy, Determinative. I. Title. QE369D5S58 549', ISBN-13: e-isbn-13: DOT: / This work is subject to copyright. All rights are reserved. whether the \vhole or part of the material is concerned, specifically those of translations. reprinting, fe-use of illustrations. broadcasting. reproduction by photocopying machine or similar means, and storage in data banks. Under ~ 54 of the German Copyright Law where copies are made for other than privatl' use. a fcc is payable to the publisher. the amount of the fcc to be determined by agreement with the publisher. by Springer-Verlag Berlin Heidelberg Softcover reprint of the hardcover 1st edition 1974 The use of registered names. trademarks. etc. in this publication does not imply. even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

4 Dedicated to Elvira, Verena, Bettina, and Nadine

5 Preface At first glance it may seem presumptuous to want to add yet another to the numerous books on Differential Thermal Analysis (DT A). Thermoanalytical methods have been in use for some time, as shown by the more than five thousand publications containing DT A or TG curves listed by SMOTHERS and CHIANG in the bibliography to their handbook and abstracted in the several volumes of Thermal Analysis Abstracts (TAA), edited by J.P.REDFERN for the International Confederation for Thermal Analysis (ICT A). Every three years the proceedings of ICT A meetings are published, bringing the latest results of thermoanalytic research. There is also the Scifax DT A Data Index, edited by R. C. MACKENZIE (1962) and modeled on the ASTM pattern card index (used for X-ray investigations), a compilation of the DT A data for several hundred minerals, and inorganic and organic materials. The theoretical foundations of thermogravimetry and DT A have been described in detail by LEHMANN, DAS and PAETSCH (1953), R.C. MACKENZIE (1957, 1970), DUVAL (1963), WENDLANDT (1964), GARN (1965), F.PAULIK et al. (1966), SMOTHERS and CHIANG (1966), and KEATTCH (1969). Thermoanalytical results are strongly influenced by various factors relative to preparation and equipment (see of this study). This is the reason why we frequently find, in these books as well as in the Scifax-Card catalog, contradictory data on the same substance. Mineralogical publications and textbooks therefore often stress that: "It is possible only in rare cases, and even here only in specific questions, to clearly identify a mineral by means of DT A alone" (GERMAN MULLER, 1964); that: "It is not possible to obtain an accurate quantitative determination of the amount of a mineral in a sample by means of the DT A method" (V AN DER MAREL, 1956); or: "Finer distinctions and hence total mineral determination of ceramic raw materials can only be obtained if DT A is supplemented by other analytical methods, specifically X-ray diffraction" (LIPPMANN, 1959). Several authors have published differing DT A curves for similar minerals, and these have sometimes been interpreted to mean that the minerals reflect chemical or genetic differences, even though no such distinctions would be found

6 VIII Preface under truly comparable test conditions. Many publications give incomplete descriptions of sample preparation and analysis and such details are often omitted. A comparison of DT A data on minerals is thus possible only on a limited basis or not at all, so justifying the above-quoted statements of G. MULLER, LIPPMANN or V AN DER MAREL. With regard to mineralogy, the best textbooks on thermoanalysis frequently merely survey the application of DT A, i.e. they show characteristic curves for particular mineral types and list the often widely differing data found in the literature. It is not often that the causes of these differing data are discussed, as for example they are in the chapter on carbonates by WEBB and KRUGER in MACKENZIE'S Differential Thermal Analysis, Vol. 1 (1970). The disadvantage of all handbooks, even those as carefully compiled as MACKENZIE'S (1957, 1970, 1972), is that they collect and compare the data of many authors obtained under differing conditions of analysis. It is the present author's opinion that, where an analytical method depends so much on the equipment and procedure used as does DT A, one analyst should be asked to work out the DT A characteristics of the most important minerals under the conditions recommended by let A and other bodies. The assignment should include consideration and standardization of all the factors that can influence the shape of DT A curves and their data. Part II of this monograph tackles this problem by facilitating the identification systematics by means of procedural improvements and supplements (cf ; II-lO). Part III of this book concerns special mineralogical applications of DT A beyond the "usual" scope of qualitative and semiquantitative mineral determinations, i.e. the relevance of DT A measurements to the results of crystal chemistry, crystal physics, or petrology. The examples given in Part III for the application of DT A to chemical composition, degree of disorder, or formation of minerals constitute the first steps. There must still be numerous investigative possibilities connected directly with the field of mineralogy. For instance, DT A could be used to some extent for clarification of structural order-disorder phenomena, for detection of high-temperature modifications that are unstable at low temperatures, and for studying variations in thermal behaviour due to mixed-crystal formation, diadochy, etc. DT A, originally a mineralogic method, is now used more frequently in other fields of scientific research, whereas in mineralogy it is employed almost exclusively for routine determinations. About 1930, more than 80% of all DT A determinations dealt with mineralogical matters; today the proportion of DT A publications relating to all earth sciences amounts to only 2 to 5%. This decrease is clearly evident from the two specialized periodicals, Journal oj Thermal Analysis and Thermochimica Acta. Of the approximately 180 papers given at the International

7 Preface IX Coriference on Thermal Analysis in Davos (ICTA III, August 1971) only 10, and of the 305 papers given in Budapest (ICT A IV, July 1974) only 24 dealt with the geosciences. The emphasis of thermoanalytical research seems to have shifted to the fields of chemistry and materials science. The main reason why mineralogists neglect the DT A method is, in the author's opinion, because the possibilities for the application of differential thermal analysis to mineralogy are still far too little known. The results of this study were obtained during the years 1966 to 1973 when the author was working in the mineralogical institutes of the universities of Gottingen and Karlsruhe. I wish to thank all the members of these institutes for their support, especially C. W. CORRENS (Gottingen), E. ALTHAUS and H. WONDRATSCHEK (Karlsruhe) for many critical discussions, H. U. BAMBAUER (MUnster), R. BEISING (Stuttgart), W. ECHLE (Aachen), F.-J. ECKARDT and P. MULLER (Hannover), M. GRAMSE, V. KUPl:IK, R. KURZE, G. MENSCHEL, K.-H. NITSCH, and R. USDOWSKI (Gottingen), K. KAUTZ (Essen), H. KULKE (Bochum), F. LIPP MANN (TUbingen), H. MEIXNER (Salzburg), R. METZ (Karlsruhe), G. MUL LER (Heidelberg), K. H. SCHULLER (Selb), and H.-J. TOBSCHALL (Mainz) for sample material, S. EBEL, R. EMMERMANN and U. LENNARTZ for chemical analysis, R. BENDER and R. BENJES for typing the manuscript, U. FRANK, B. LEST!, H. SCHNITTKA, and H. SIEGEL (all in Karlsruhe) for drawing the figures. Karlsruhe, September 1974 W. SMYKATZ-KLOSS

8 Contents Part I. Methods 1. Thermogravimetry and Differential Thermal Analysis 1 2. Heat Changes and Their Measurement in DT A Cause of Heat Changes DT A Apparatus Characteristics of DT A Curves and DT A Data Factors Which Influence DT A Data Furnace Atmosphere Sample Arrangement Thermocouples Heating Rate Reference Material Grain Size and Packing Density Amount of Sample Preparative Factors The Technique of Measurement and of Standardization Recommendations of ICT A for the Publication of Thermoanalytical Data Standardization and Indirect Characterization by Means of PA-Curve and Standard Temperature Calibration and Exactness of Measurement Calibration Exactness and Reproducibility of Measurements Improvement of the Exactness of Measurement Using Internal Standards Sensibility of Proof

9 XII Contents 4. Quantitative Determinations by DT A Difficulties in Quantitative DT A Determinations of Minerals Determination of Thermodynamic Data Equilibrium Temperatures Heat of Reaction, LI H Methods Combined with DT A 5.1 DT A + High-Temperature X-Ray Analysis 5.2 DT A + High-Temperature Microscopy 5.3 High-Pressure DT A DT A + Mass Spectrometer Other Methods Related to or Combined with DT A Part II. Application of Differential Thermal Analysis to Mineralogy: Identification and Semi-Quantitative Determination of Minerals Elements and Chalcogenides 1.1 Elements 1.2 Chalcogenides 2. Halogenides and Sulfates 2.1 Halogenides 2.2 Sulfates 3. Oxides and Hydroxides 3.1 Oxides Hydroxides 3.3 Soils and Iron Ores 4. Carbonates and Nitrates 4.1 Carbonates Free of Water and without Other Anions 4.2 Carbonates Free of Water with Other Anions 4.3 Hydrated Carbonates without Other Anions 4.4 Hydrated Carbonates with Other Anions 4.5 Nitrates

10 Contents XIII 5. Borates, Phosphates, and Arsenates Borates Phosphates and Arsenates Ortho-, Ring-, and Chain Silicates Sheet Silicates Kaolinites Pyrophyllite and Talc Montmorines (Smectites) and Vermiculites 7.4 Micas 7.5 Chlorites Serpentines Palygorskite and Sepiolite 7.8 Clay Minerals with Mixed-Layer Structure 7.9 Mixtures of Sedimentary Minerals ("Clays") Zeolites Allophane, Opal, and Organic Matter of Soils and Sediments Development of Identification Diagrams Part III. Special Application of Differential Thermal Analysis in Mineralogy: Statements about Chemical Composition, Degree of Disorder, and Genesis of Minerals Influence of the Chemical Composition on the Decomposition Temperatures of Carbonates and Hydroxides Substitution of Ca ++ by Mg + + or Pb ++ in Calcites Substitution of Ca ++ by Sr ++, Ba ++, and Pb ++ in Aragonites Substitution of Mg++ by Fe++ and Mn++ in Dolomites Hydrozincite and Aurichalcite The Incorporation of Al into the Structure of Goethite 114

11 XIV Contents 2. Influence of the Chemical Composition on the Temperatures of Structural Transformations Carbonates Cu-Ag Sulfides Influence of the Chemical Composition on the Curie-Temperatures of Magnetites Contribution to the Classification of Chlorites Smectites and Vermiculites: The Distinction between Di- and Tri-Octahedral Minerals and Grain Size Determination Determination of the Degree of Disorder in Kaolinites The Interdependence of Degree of Disorder, High-Low Inversion, and Temperature of Formation of Low-Temperature Cristobalites The Determination of Inversion Temperatures of Quartz Crystals as a Petrologic Tool The High-Low Inversion Behaviour of Microcrystalline Quartz Crystals References. 159 Subject Index 173