Gases And Metals

GASES AND METALS AN INTRODUCTION TO THE STUDY OF GAS-METAL EQUILIBRIA BY COLIN J. SMIJHELLS M. C., D. Sc. Member of the Research Staff of the General Electric Co., Ltd., Wembley Author of Tungsten Impurities in Metals LONDON CHAPMAN HALL, LTD. ii HENRIETTA ST., W. C. 2 1937 PRINTED IN GREAT BRITAIN THE ABERDEEN UNIVERSITY PRESS LIMITED ABERDEEN, SCOTLAND AUTHORS PREFACE. THE behaviour of gases and metals in contact with one another is of fundamental importance in many branches of science and industry. Gas-metal equilibria are being studied from many points of view by different groups of workers. The adsorption of gases on metal surfaces is the controlling factor in many catalytic processes, and is also of great importance in the manu facture of all kinds of vacuum devices, such as electric lamps, thermionic valves, and so on. The diffusion of gases in metals, both solid and liquid, and the solubility of gases in metals, determine success or failure in the manufacture of all metallurgical products. The general principles underlying the equilibria between gases and metals are now generally estab lished, but owing to the diverse nature of the problems which have led to their investigation, the results obtained in different fields are somewhat widely scattered in scientific literature. This book is intended to bring together under one cover the results of research in all these fields, and to emphasise the intimate connection between these different phenomena. I have made no attempt to deal with the practical application of these principles to metallurgical processes. Nevertheless, I hope that this book, by defining the vi PREFACE fundamental principles and collecting the available datarelating to gas-metal equilibria in an accessible form, will be found of help in understanding and solving these problems. I have been very greatly helped in the preparation of the book by my colleagues, Mr. C. E. Ransley, B. Sc., and Mr. Ivor Jenkins, B. Sc., and am glad of this opportunity of expressing my gratitude to them. My thanks are also due to Mr. C. C. Paterson, Director of the Research Laboratories of the General Electric Co., Ltd., at Wembley, for permission to refer to the results of work carried out there. 37 GRANGE ROAD, BUSHEY, 31 December, 1936. CONTENTS. CHAP. PAGE I. ADSORPTION ........ i II. DIFFUSION ........ 77 III. SOLUTION 137 INDEX 213 CHAPTER I. ADSORPTION. SCHEELE, in 1777, was the first to observe that gases or vapours brought into contact with charcoal combined with it in some way, but could be recovered by the application of heat. The process was given the name of adsorption by Bois Reynolds, and although numerous observations of a similar kind were made by others, the subject did not receive serious consideration till nearly 50 years later. The investigations of de Saussure in 1814, and the later work of Graham, Faraday, Chappius, Bunsen, and others, made clear the main phenomena underlying the adsorption of gases by solids. Faraday, 1 in particular, as early as 1833, described experiments on the reactions of hydrogen and oxygen at the surface of platinum plates, and showed a remarkable insight into the mechanism of this catalytic reaction. He believed that the platinum did not itself play any chemical part in the reaction, but that the molecules of the gases, being condensed on its surface, were in far closer proximity to each other, and therefore in amore favourable condition for reaction to occur. He also investigated the poisoning effect of car bon monoxide on the catalytic activity of his platinum plates in promoting oxygen-hydrogen combination, and attributed the effect to the presence of an adsorbed film of carbon monoxide, which hindered the adsorption of the other gases. Faraday had practically no proof at the time that his hypothesis was correct, but we have no reason to modify it essentially now, after 100 years...