PREFACE

ΤΟ

THE FOURTH EDITION.

THE most important alteration in the present Edition is the introduction of the formulæ representing the various chemical compounds described in the Notes to the Tables. The formulæ are those now generally employed by chemical writers and teachers in this country.

The verbal description of the composition in the Tables of Common Compounds of the several metals has not been altered so as to bring it into perfect harmony with the formulæ, since the description there given generally informs the learner what substances can be obtained by the decomposition of the Common Compounds, which is not so easily to be ascertained by.an inspection of the formula.

For example, thie.composition of saltpetre is described at page 81, as Potash (Potassium and Oxygen) and Nitric Acid, whilst the formula KNO, does not indicate the presence of potash (KO) or of nitric acid (HNO,); but both these substances are obtainable from saltpetre by very

simple chemical operations, and saltpetre may be prod by causing them to act upon each other.

It is true that similar reasoning would justify the s ment that common salt contained soda and hydrochloric instead of sodium and chlorine, but the Author feels an endeavor to be absolutely consistent would injure practical usefulness of so small a book.

May, 1879.

PREFACE

ΤΟ

THE FIRST EDITION.

THIS work is intended for use in the Chemical Laboratory by those who are commencing the study of Practical Chemistry. It contains—

(1) A series of simple Tables for the analysis of unknown

substances of all kinds (not excepting organic bodies) which are known to be single substances, and not mixtures:

(2) A brief description of all the practically important

single substances likely to be met with in ordinary analysis, by which the learner may satisfy himself that his results are correct, and may at the same time become acquainted with the leading properties of the most important. chemicals, and with the foreign substances which they are liable to contain:

(3) Simple directions and illustrations relating to Che

mical Manipulation, not collected into a separate chapter, but given just where the learner requires them in the course of analysis:

(4) A system of Tables for the detection of unkn

substances with the aid of the Blowpipe:

(5) Short instructions upon the purchase and prepara

of the tests, intended for those who have not acces a Laboratory.

The book does not presuppose any knowledge of C mistry on the part of the pupil, and does not enter into & theoretical speculations.

It dispenses with the use of all costly Apparatus a Chemicals, and is divided into separate Exercises or Lesso with Examples for Practice, to facilitate the instruction. large Classes.

The Author hopes that it will be found to contain all t Practical Chemistry required for the various Examination except for the highest Science degrees, such as the B.S and D.Sc. of the University of London.

The method of instruction here followed has been adopte by the Author after twenty-three years' experience as teacher in the Laboratory, by which he has been led t conclude that a knowledge of Analytical Chemistry, or the power of discovering the nature of unknown substances, i the first and often the only requirement of the great majority of learners, and that, independently of the technical value o such knowledge, its acquisition forms a most valuable part of education, by cultivating the powers of observation, and affording excellent examples of the application of logicɛ reasoning in practical work:

The ordinary method of teaching Analytical Chemistry, by causing the pupil to study the Reactions or tests for all the metals and non-metallic bodies, before he proceeds to exa