society, and invest with power a people that have never been educated to use it. I am not insensible to the objections which are frequently urged against the introduction of new subjects of instruction; but it has often struck me that some of the subjects usually taught in schools might be got rid of with great advantage to the children. The great object of education with the working classes is its practical value, and they rarely rise above this idea; nor do I think it so low and grovelling as some have described it. Unless you can instruct a boy in some of those principles and things which will help him through life, and supply him with new resources in the time of difficulty, infusing a new sentiment into his labour, and relieving him from the monotony of mere mechanical manipulation,-unless this is done, education loses much of its usefulness, and fails in the estimation of those for whose benefit it is intended. I would not, on this account, ignore everything of an abstract character. A man who can demonstrate the first twenty propositions in Euclid, is raised to an intellectual level above that at which he stood before. But persons who have little capacity for mathematical investigation, often distinguish themselves in the sciences of experiment and observation; and these sciences are not without their logic in the hands of a good teacher. Working men are almost always experimentalists; a difficulty or failure is overcome by trying some other method; they seldom reason out a result,—indeed, results in natural science are rarely so obtained,—and if they reason at all, it is after the result is accomplished. I have endeavoured to render this book as practical as possible; and am not aware that anything of importance is omitted. In the hands of an intelligent teacher, it will admit of much amplification. St. John's Hill, Wandsworth. PREFACE TO THE SECOND EDITION. THIS Edition has been carefully revised and enlarged, and I have endeavoured to make it a convenient and suitable Text Book for pupils in Elementary Chemistry. Chemists have of late years gradually changed their views with reference to the composition of bodies, especially acids and salts; a corresponding change in Notation being thereby rendered necessary. These views are not as yet universal, but there can be no doubt of their ultimate adoption. The modern System of Notation has been introduced into this work; but as we are in a kind of transition state, I have thought it advisable to retain the old method of notation, the new will usually be found in brackets by the side of the old. The work also contains all the former Examination Papers of the Science and Art Department of the Committee of Council on Education. Many of the questions are of a mathematical character, and somewhat difficult. I have given full solutions of all the questions which involve methods of calculation, and a careful study of these questions and their solutions will be of great advantage to those who are reading for Certificates. In preparing this Edition I have sought the advice of several Certificated Teachers of Elementary Science, and hope I have succeeded in producing a book worthy the acceptance of those engaged in teaching and learning the Elements of Chemical Science. St. John's Hill, Wandsworth, S.W. March, 1863. ELEMENTARY CHEMISTRY. THE earth is made up of a variety of solid, liquid, and gaseous materials. Chemistry investigates the relationship between the different kinds of atoms or particles of which these materials are composed. If the earth were composed of only one simple substance, there could be no such science as chemistry. All substances, whether animal, vegetable, or mineral, are either simple or compound. Those which cannot be reduced into any simpler form are called elements, and these elements combine to form an infinite variety of compound bodies. We may illustrate this by the letters of the alphabet, which cannot be separated into any simpler form, but by different combinations form a great variety of words. These words can be separated into their letters, as can the compound bodies into the elements of which they are composed. It is only compound bodies which can thus be separated. Sulphur, iron, zinc, copper, oxygen, hydrogen, cannot be resolved into any simpler substance: they are therefore called elementary bodies. Water can be separated into oxygen and hydrogen, and is therefore a compound body, and not an element, as was once supposed. Again, chalk, or carbonate of lime, is made up of three elementary bodies, -a metal called calcium, oxy B gen, and carbon. Common salt is composed of two elementary bodies,- -a metal called sodium, and chlorine. The great majority of compounds are formed by the union of two, three, or four elementary bodies. The separation of these compound bodies into simpler forms is called analysis, and the formation of compound bodies by the union of simple ones is called synthesis. The Elementary bodies are about seventy in number; but many of them are so rare as not to require special attention. They are divided into metals and metalloids, or non-metallic bodies. The metals have great lustre are good conductors of heat and electricity. These pro perties are never associated in a non-metallic body. This division is not based on any exact principles of science, but as a common means of description. The metalloids or non-metallic bodies in the following table are marked with an asterisk. The rare elements are printed in italics. TABLE OF ELEMENTS. : |