Imágenes de páginas
PDF
EPUB

ON

ELEMENTARY CHEMISTRY

IN

MEESE LIBRARY

THE TEACHING

OF
SCHOOLS AND SCIENCE CLASSES

BY
WILLIAM A. TILDEN, D.Sc., F.R.S.

SECOND EDITION
UNIVERSITY

CALIFORNIA
LONGMANS, GREEN, AND CO.
LONDON, NEW YORK, AND BOMBAY

1896

PROFESSOR OF CHEMISTRY IN THE ROYAL COLLEGE OF SCIENCE, LONDON
EXAMINER IN CHEMISTRY TO THE DEPARTMENT OF SCIENCE AND ART

OF THE

All rights reserved

66664

BY THE SAME AUTHOR,

INTRODUCTION TO THE STUDY OF

CHEMICAL PHILOSOPHY. The Princi-
ples of Theoretical and Systematic Chemistry.
With 5 Woodcuts. With or without the
ANSWERS of Problems. Fcp. 8vo. 45. 6d.

PRACTICAL CHEMISTRY. The Principles

of Qualitative Analysis. Fcp. 8vo. Is. 6d.

LONGMANS, GREEN, & CO.

LONDON, NEW YORK, AND BOMBAY,

[merged small][merged small][ocr errors][merged small]

THE issue of the new Syllabus of Inorganic and Organic Chemistry by the Department of Science and Art marks a very important advance in the history of the teaching of these subjects in this country. In this Syllabus the treatment of Chemistry from the theoretical side remains necessarily at the discretion of the teacher, though from the order in which the subdivisions of the matter for treatment are placed, it is obvious that, in the early stages especially, it is considered desirable to keep theory in a subordinate position, and to make use of it only when a sufficient foundation of fact has been duly acquired by the pupil. According to the experience of the Author, it is scarcely possible to use a purely inductive method in dealing with young students; but, though this may be admitted, the necessity of clearly distinguishing fact from hypothesis requires to be established far more definitely than at present in the minds of a large proportion of the teachers

whose pupils present themselves for the examinations of the Department.

In the earliest stages, the learner's attention and energy are usually wholly used up in the process of exact observation. To see and accurately record the whole of a given phenomenon is enough for young boys and girls, and, until sufficient practice and experience in this direction have been gained, it is a better educational exercise than the attempt to solve problems which, to render them simple enough, require the neglect of part of the phenomena. For example, the investigations of the changes which occur when a piece of sheet copper is heated in the air requires for a complete answer observations (a) on the iridescent colours first visible, (b) the black coating which succeeds, (c) the red lining to the scales which may be separated on cooling, (d) the temperature at which these changes occur, (e) the alteration in weight of the mass, (f) changes in the surrounding air, &c. Observation of all these facts is possible even for the beginner; but when he is in possession of the whole, he would be a wonderful boy indeed who could, without assistance, infer that the products contain oxygen as well as copper, and that there are two oxides of copper of definite composition, to say nothing about the colours of thin films.

Chemistry is a science which, in its modern form, has sprung up almost entirely within the

memory of living man, and its boundaries, already far reaching, are being rapidly extended year by year, and even month by month, by the labours of an army of workers. This condition of growth constitutes a feature of the science which should render it as a study attractive in no ordinary degree ; and the teacher who desires to make use of it as an effective educational agent must devote some part of his time to extending and consolidating his own knowledge. Not that the very latest discovery is necessarily more important than many of the facts which have been long familiar, and the teacher ought to be careful to exercise due discı etion in communicating to a class of young fupils the most recent results of observation, lest their sense of proportion should be unequal to the strain of distinguishing the important from the comparatively unimportant. The discovery of argon in the atmosphere twelve months ago possesses the greatest interest for the advanced student; but oxygen still ranks higher in importance, from all practical as well as theoretical points of view, than the newly discovered gas.

In the new Syllabus issued by the Department the most important changes will be noticed in the part which relates to the practical examinations. Scientific chemistry is based almost wholly upon observation and experiment, and the practical study of this science is one of the most useful means of developing the faculties of observation. But even

« AnteriorContinuar »