PREFACE.

The object held constantly in view in writing this book has been to
prepare a suitable text-book in Chemistry for the average High
School,--one that shall be simple, practical, experimental, and
inductive, rather than a cyclopaedia of chemical information.

For the accomplishment of this purpose the author has endeavored
to omit superfluous matter, and give only the most useful and
interesting experiments, facts and theories.

In calling attention, by questions, and otherwise, to the more
important phenomena to be observed and facts to be learned, the
best features of the inductive system have been utilized.
Especially is the writing of equations, which constitute the
multum in parvo of chemical knowledge, insisted upon. As soon as
the pupil has become imbued with the spirit and meaning of
chemical equations, he need have little fear of failing to
understand the rest. To this end Chapters IX., XI., and XVI.
should be studied with great care.

In the early stages of the work the equations may with advantage
be memorized, but this can soon be discontinued. Whenever symbols
are employed, pupils should be required to give the corresponding
chemical names, or, better, both names and symbols.

The classification of chemical substances into acids, bases and
salts, and the distinctions and analogies between each of these
classes, have been brought into especial prominence. The general
relationship between the three classes, and the general
principles prevailing in the preparation of each, must be fully
understood before aught but the merest smattering of chemical
science can be known.

Chapters XV.-XXI. should be mastered as a key to the subsequent
parts of the book.

The mathematical and theoretical parts of Chemistry it has been
thought best to intersperse throughout the book, placing each
where it seemed to be especially needed; in this way, it is hoped
that the tedium which pupils find in studying consecutively many
chapters of theories will be avoided, and that the arrangement
will give an occasional change from the discussion of facts and
experiments to that of principles. In these chapters additional
questions should be given, and the pupil should be particularly
encouraged to make new problems of his own, and to solve theta.

It is needless to say that this treatise is primarily designed to
be used in connection with a laboratory. Like all other text-
books on the subject, it can be studied without such an
accessory; but the author attaches very little value to the study
of Chemistry without experimental work. The required apparatus
and chemicals involve but little expense, and the directions for
experimentation are the result of several years' experience with
classes as large as are to be found in the laboratory of any
school or college in the country.

During the present year the author personally supervises the work
of more than 180 different pupils in chemistry. This enables him
not only to assure himself that the experiments of the book are
practical, but that the directions for performing them are ample.
It is found advisable to perform most of the experiments, with
full explanation, in presence of the class, before requiring the
pupils either to do the work or to recite the lesson. In the
laboratory each pupil has a locker under his table, furnished
with apparatus, as specified in the Appendix. Each has also the
author's "Laboratory Manual," which contains on every left-hand
page full directions for an experiment, with observations to be
made, etc. The right-hand page is blank, and on that the pupil
makes a record of his work. These notes are examined at the time,
or subsequently, by the teacher, and the pupil is not allowed to
take the book from the laboratory; nor can he use any other book
on Chemistry while experimenting. By this means he learns to make
his own observations and inferences.

For the benefit of the science and the added interest in the
study, it is earnestly recommended that teachers encourage pupils
to fit up laboratories of their own at home. This need not at
first entail a large outlay. A small attic room with running
water, a very few chemicals, and a little apparatus, are enough
to begin with; these can be added to from time to time, as new
material is wanted. In this way the student will find his love
for science growing apace.

While endeavoring, by securing an able corps of critics, and in
all other ways possible, to reduce errors to a minimum, the
author disclaims any pretensions to a work entirely free from
mistakes, holding himself alone responsible for any shortcomings,
and trusting to the leniency of teachers and critics.

The manuscript has been read by Prof. Henry Carmichael, Ph.D., of
Boston, and to his broad and accurate scholarship, as well as to
his deep personal interest in the work, the author is indebted
for much valuable and original matter. The following persons have
generously read the proof, as a whole or in part, and made
suggestions regarding it, and to them the author would return his
thanks, as well as acknowledge his obligation: Prof. E. J.
Bartlett, Dartmouth College, N.H.; Prof. F. C. Robinson, Bowdoin
College, Me.; Prof. H. S. Carhart, Michigan University; Prof. B.
D. Halsted, Iowa Agricultural College; Prof. W. T. Sedgwick,
Institute of Technology, Boston; Pres. M. E. Wadsworth, Michigan
Mining School; Prof. George Huntington, Carleton College, Minn.;
Prof. Joseph Torrey, Iowa College; Mr. C. J. Lincoln, East Boston
High.School; Mr. W. H. Sylvester, English High School, Boston;
Mr. F. W. Gilley, Chelsea, Mass., High School; the late D. S.
Lewis, Chemist of the Boston Gas Works, and others.

R. P. W.

BOSTON, January 3, 1888.