Surface and Colloid Science: Volume 11: Experimental Methods

353 Pages·1979·9.052 MB·English

by  Robert J. Good (auth.), Robert J. Good, Robert R. Stromberg (eds.)

SURFACE AND
COLLOID SCIENCE
Volume II
ADVISORY BOARD
BORIS V. DERJAGUIN, Institute of Physical Chemistry, Academy of Science
of the USSR, Moscow, USSR
TOMLINSON FORT, JR., Department of Chemical Engineering, Carnegie
Mellon University, Pittsburgh, Pennsylvania
STIG FRIBERG, Department of Chemistry, University of Missouri-Rolla,
Rolla, Missouri
J. ADIN MANN, JR., Chemical Engineering Division, Case Western Reserve
University, Cleveland, Ohio
BARRY W. NINHAM, Institute of Advanced Studies, Australian National
University, Canbe"a, Australia
ROBERT A. PIEROTTI, Department of Chemistry, Georgia Institute of Tech
nology, Atlanta, Georgia
VELIMIR PRAVDIC, Institute "Rudjer Bo~kovic," Zagreb, Yugoslavia
KOZO SHINODA, Department of Applied Chemistry, Yokohama National
University, Minamiku, Yokohama, Japan
STANISLAS J. TEICHNER, Universite Claude Bernard -Lyon 1, Villeurbanne,
France
CAREL J. VAN OSS, School of Medicine, State University of New York at
Buffalo, Buffalo, New York
AGIENUS VRIJ, Van't Hoff Laboratorium, Rijksuniversiteit, Utrecht, The
Netherlands
ERVIN WOLFRAM, Department ofC olloid Science, Lorand Eotvos University,
Budapest, Hungary
ALBERT C. ZETTLEMOYER, Lehigh University, Bethlehem, Pennsylvania
A Continuation Order Plan is available for this series. A continuation order will bring
delivery of each new volume immediately upon publication. Volumes are billed only upon
actual shipment. For further information please contact the publisher.
SURFACE AND
COLLOID SCIENCE
Volume 11
EXPERIMENTAL METHODS
Edited by
ROBERT 1. GOOD
State University of New York at Buffalo
Amherst, New York
and
ROBERT R. STROMBERG
Bureau of Medical Devices
Food and Drug Administration
Silver Spring, Maryland
PLENUM PRESS· NEW YORK AND LONDON
The Library of Congress cataloged the first Plenum Press edition of this title as follows:
Main entry under title:
Surface and colloid science.
Vol. 10- published by Plenum Press, New York.
Includes bibliographies.
1. Surface chemistry-Collected works. 2. Colloids-Collected works. I. Matijevic, Egon,
1922- ed.
QD506.S78 541'.345 67-29459
ISBN 978-1-4615-7971-7 ISBN 978-1-4615-7969-4 (eBaak)
001 10.1007/978-1-4615-7969-4
This book was edited by Robert R. Stromberg in his private capacity.
No official support or endorsement by the Food and Drug Administration
is intended or should be inferred.
Library of Congress Catalog Card Number 67-29459
ISBN 978-1-4615-7971-7
© 1979 Plenum Press, New York
Softcover reprint of the hardcover 1s t edition 1979
A Division of Plenum Publishing Corporation
227 West 17th Street, New York, N.Y. 10011
All righ ts reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted,
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
Preface
Surface science and colloid science are preeminently experimental subjects.
They constitute complementary aspects of a field which has been notably
active since World War II; there is every reason to expect that the level of
activity will continue to rise in the coming decades, so it is timely to review
certain experimental methods of surface and colloid science as they exist,
and to evaluate and refine those methods. This volume, and others that will
follow, are principally concerned with experimental methods.
The working scientist needs access to the latest techniques, of course.
He also needs to learn of the potentialities of recently developed techniques
which he may not have been aware of. Equally important, or perhaps even
more so, he needs to learn of the pitfalls of existing methods. One might say,
wistfully, that it would be nice to be able to pick up somebody's description
of a new piece of apparatus, to go into the laboratory, to build it, and to have
it work, the first time!
There is, however, a serious problem of the interaction between the
experiment per se and the theory for which the experiment is designed. Very
often, this interaction renders problematic the interpretation of "direct"
observations. An example, from experience of the senior editor of this
volume, is the question of contact angle hysteresis. (See Chapters 1 and 2.)
There is reason to believe that experimenters have, for years, been "throw
ing away" important and easily accessible information about the surfaces
they study, by neglecting to measure retreating angles as well as advancing
angles. The interaction between theory and experiment, in regard to
hysteresis, is a curious one: If a solid surface is flat and homogeneous, and if
sufficient time is allowed in the measurement, theory says there should be no
hysteresis. The theory of hysteresis indicates that it is a phenomenon with
several causes; and it may be a measure both of the nonideality of the solid
and of rate effects that are difficult to control. So there is a natural
temptation for an experimenter to ignore hysteresis, and to assume that he
has prepared his surfaces carefully enough that they are "ideal."
Considerations such as these determine some components of the edi
torial policy for this volume. It was evident to us that chapters on experi-
v
vi Preface
mental methods would have to contain a modicum of what could best be
called the theory of the phenomenon, in addition to the theory of the
experiment per se. It soon became apparent that the relative proportions of
these two types of theories would vary widely from one subject of research to
another.
We have selected contributors who are truly authoritative in their fields,
and have asked them to make their chapters as "critical" as possible. We feel
that, to a major extent, they have succeeded. The proof of this contention
will, of course, be in the utilization of these methods by future experimen
ters. At the very least, this work will be a considerable help in making these
methodologies accessible to working scientists.
The editing of the present volume was started as part of an earlier series,
the first volume of which was Techniques of Surface and Colloid Chemistry
and Physics, Volume I, edited by Good, Stromberg, and Patrick, Marcel
Dekker, Inc., 1972. We have, since 1972, combined forces with Professor
Egon Matijevic, editor of the series, Surface and Colloid Science, and moved
our series to a new publisher. For sake of generality, we have preserved
Professor Matijevic's series title. We believe that the combined strength of
the two efforts, with the support of Plenum Publishing Corporation, will
make it possible to produce a new series which will be appreciably stronger
than the sum of two separate works.
It is intended that the division of labor in editing will be such that Dr.
Matijevic will edit volumes in the series that deal primarily with results, both
theoretical and experimental, in the various areas of surface and colloid
science, while we (Good and Stromberg) will edit volumes that deal pri
marily with experimental methods. As noted above, the distinction is not
always a clear-cut one, but we expect to be able to make it in a logical
fashion.
ROBERT GOOD
ROBERT STROMBERG
Contents
1. Contact Angles and the Surface Free Energy of Solids
Robert 1. Good
1. Introduction ............ 1
2. Solid Surfaces . . . . . . . . . . . . 2
2.1. Requirement of Effective Flatness 2
2.2. Surface Free Energy of a Solid 3
2.3. Heterogeneous Surfaces 4
2.4. Rough Surfaces 6
3. Thermodynamic Theory of Equilibrium Contact Angles on Ideal Solids 6
4. Contact Angles on Nonideal Surfaces, Dynamic Effects, and Hysteresis 10
4.1. Nature of Hysteresis ............... 10
4.2. Test for Contact Angle Equilibrium and Surface Quality 14
4.3. Effect of Curvature of the Three-Phase Line . . . . . 15
5. Treatment of Contact Angle Data Obtained with a Series of Liquids on a
Solid ......... 16
5.1. Series of Pure Liquids ...... 16
5.2. Mixtures of Liquids ...... 21
Appendix. Note on Recent Developments 23
A.1. Microscopic Contact Angles 23
A.2. Acid-Base Interactions at Solid Surfaces 25
References . . . . . . . . . . . . . . . . 27
2. Techniques of Measuring Contact Angles
A. W. Neumann and R. 1. Good
1. Introduction 31
2. Experimental Methods 32
2.1. Flat Plate . . . 32
2.2. Contact Angle Measurement at a Capillary Tube 60
2.3. Elongated Solid Bodies-Cylinders, Rods, and Fibers 63
2.4. Powders ....... . 70
2.5. Consolidated Porous Solids 79
vii
viii Contents
3. Preparation of Liquids 79
4. Preparation of Solid Surfaces 80
5. Standards ....... . 86
6. Note on Liquid-Liquid-Solid Systems 87
References . . . . . . . . . . . . 88
3. Pendant Drop Technique for Measuring Liquid
Boundary Tensions
Durga S. Ambwani and Tomlinson Fort, Jr.
1. Introduction .................... 93
1.1. Fundamental Principles and Outstanding Advantages 93
1.2. Applications of Pendant Drop Technique 94
2. Previous Experimental Studies 95
2.1. Surface Tension Studies . . . . . 95
2.2. Interfacial Tension Studies 95
2.3. Studies of Highly Viscous Materials 96
2.4. Studies in Vacuum and at High Temperatures and Pressures 96
2.5. Studies of Adsorption from Solutions 97
3. Theory . . . . . . . . . . . 97
3.1. Historical Development . . . 97
3.2. Mathematical Derivations . . 98
3.3. Method of the Selected Plane 100
3.4. Tables and Equations for the Method of the Selected Plane 101
3.5. More Recent Methods 104
4. Experimental Apparatus 104
4.1. General Survey 104
4.2. Basic Elements 105
4.3. Light Source and Collimating Lens 105
4.4. Pendant Drop Cell . . . . . . 106
4.5. Pendant Drop Syringe ..... 106
4.6. Photomicrographic Arrangement . 108
4.7. Temperature and Vibration Control 109
4.8. Tests of the Experimental Methods 110
5. Calculation of Boundary Tension 112
6. Error Analysis ........ 113
6.1. Method of Analysis 113
6.2. Error Due to Uncertainties in Known Quantities 114
6.3. Error Due to Measurements of Pendant Drop Dimensions 114
6.4. Expression for Overall Probable Error 116
6.5. An Example of Error Calculation 116
References . . . . . . . . . . . . . . . 118
Contents ix
4. Electrophoresis of Particles in Suspension
Arthur M. James
1. Introduction .................. 121
2. Concept of the Electrical Double Layer ....... 121
3. Mathematical Treatment of Migration in an Electric Field 124
4. Calculation of (-Potentials and Surface Charge Densities 130
5. Principles of Experimental Methods 131
5.1. Theory of the Closed Cell 132
5.2. Types of Closed Cell 136
5.3. Electrode Systems 138
5.4. Electrical Circuit . . 139
5.5. Optical Arrangement 140
5.6. Thermostat 141
6. Experimental Assembly of the Rectangular Cell 142
6.1. Design and Construction 142
6.2. Assembly and Preparation for Use 147
6.3. Mode of Operation . . . . . . . 149
6.4. Calculation of Electrophoretic Mobility and Determination of Cell
Constant ............. 151
6.5. Symmetry of the Observation Chamber 153
6.6. Other Sources of Error . . . . . . . 155
6.7. Determination of Reproducibility 157
6.8. Lateral Mounting of the Rectangular Cell 158
7. Experimental Assembly of the Cylindrical Cell 160
7.1. Design and Construction 160
7.2. Assembly and Preparation for Use 164
7.3. Mode of Operation . . . . . . . 165
7.4. Calculation of the Electrophoretic Mobility 166
7.5. Symmetry of the Observation Chamber and Location of the
Stationary Level . . . . . . . . . . . . . 166
7.6. Other Sources of Error and Reproducibility . 168
8. Additional Precautions Necessary in Determination of Electrophoretic
Mobility ..... . . . . . . . . . . . . 168
8.1. Cleaning of the Electrophoresis Chamber 168
8.2. Suspending Electrolyte 168
8.3. Preparation of Suspensions ...... 170
9. Other Designs of Apparatus 170
10. Applications of the Particulate Electrophoresis Technique 174
10.1. Measurement of Mobility in Solutions of Constant pH and Ionic
Strength ........................ 174
10.2. Variation of Mobility with pH in Solutions of Constant Ionic
Strength ........................ 174
10.3. Variation of Mobility with Ionic Strength in Solutions of Constant
pH . . . . . . . . . . . . . . . . . . . . . . . . . .. 178
x Contents
10.4. Effect of Surface Active Agents on Mobility of Particles Suspended
in Buffer Solutions of Fixed pH 180
11. Nomenclature and Units 180
References . . . . . . . . . . . . 182
5. Methods of Producing Ultrahigh Vacuums and
Measuring Ultralow Pressures
J. P. Hobson
1. Introduction ..... . 187
2. General Problem of UHV 188
3. Pumps for UHV 192
3.1. Diffusion Pumps 193
3.2. Ion Pumps 193
3.3. Getter Pumps 194
3.4. Turbomolecular Pumps 194
3.5. Cryopumps .... . 195
4; Gauges for UHV .... . 196
4.1. Hot-Cathode Total Pressure Gauges 197
4.2. Cold-Cathode Total Pressure Gauges 200
4.3. Partial Pressure Gauges 202
4.4. Gauge Calibration 204
5. UHV Hardware . . . . . . 206
6. Surface Cleaning ..... 207
6.1. Bulk Heating to High Temperature 209
6.2. Chemical Reactions at Elevated Temperatures 209
6.3. Ion Bombardment Followed by Annealing 209
6.4. Electron Bombardment . . . . . 210
6.5. Pulsed Laser Bombardment . . . 210
6.6. Cleaning by Ultraviolet Radiation 211
6.7. Field Desorption . 211
6.8. Vacuum Cleaving 211
6.9. Crushing 211
6.10. Wire Brush 212
6.11. Evaporation 212
6.12. Chemical Deposition (Vapor Plating) 212
7. Conclusion 212
References . . . . . . . . . . . . . . 213
6. Electron Probe Microanalysis
Gudrun A. Hutchins
1. Introduction 217
2. Fundamentals 218
2.1. Measurement Techniques 218