WILLIAM GREGORY, M.D., F.R.S.E. Professor of Chemistry in the University of Edinburgh. THIRD EDITION, CORRECTED AND ENLARGED. LONDON: WALTON AND MABERLY, UPPER GOWER STREET, AND IVY LANE, PATERNOSTER ROW. 1853. 193.6.6. PREFACE TO THE THIRD EDITION. IN preparing a third edition of the present work, I have made no material change in its form or arrangement, but have merely added such recently observed facts as seemed appropriate in an elementary work, and made such changes and corrections as the progress of science had rendered necessary. Without, however, changing the form of the work, I have introduced a brief and elementary notice of the effects produced on matter by Heat, including the phenomena connected with liquefaction and vaporisation. This has been done under the head of water, the first and most important solid or liquid body treated of. In treating of the analysis of water, I have also taken the opportunity of briefly explaining the nature of the galvanic current and of the decomposition of compound bodies by electricity. Finally, under the head of air, I have given a short account of the physical properties of gases and vapours. In all these cases, although the subjects belong to physics, and require, for their full development, even in an elementary work, a much larger space than can here be devoted to them, yet they have so important and direct a bearing on Chemistry that it is desirable to provide the student with some elementary notions of them, leaving him to study them more fully in works specially devoted to these departments of science. I trust that this slight alteration will be found useful to the student. It has been my object, throughout, to avoid minute details, and by confining myself to what is truly elementary to limit the size of the work, so as to render it available to the student attending lectures. It is quite obvious that if the young chemist wish to make himself familiar with the whole details of the science, he must not only make use of larger and fuller treatises, but must also exchange the lecture room for the laboratory, where alone he can acquire a minute and practical knowledge of Chemistry. But to attempt to teach the beginner those minute details of which the science, in its applications, is made up, is only to encumber him with what he cannot appreciate, and greatly to retard his progress. The present edition has been enriched with a number of additional woodcuts, illustrating the different forms of apparatus used in the various operations of Chemistry. I have once more gratefully to acknowledge the favourable reception which my little work has experienced, and to trust, that the present edition may prove worthy of an equally favourable reception. WILLIAM GREGORY. UNIVERSITY OF EDINBURGH, October, 1853. |