PREFACE. At the present time, when there is so much difference of opinion as to the clearest mode of representing the constitution of chemical compounds and the changes in which they are involved, the author of a work on Chemistry is placed in a difficult position. Fully realising this, I should scarcely have ventured to undertake the task, but for the circumstance that, a third edition of "Abel and Bloxam's Handbook of Chemistry" being required, and my valued coadjutor not having leisure to devote to its preparation, it seemed to me a favourable opportunity for re-writing the handbook in such a form as to render it more useful to the general student. The present work, therefore, is designed to give a clear and simple description of the elements and their principal compounds, and of the chemical principles involved in some of the most important branches of manufacture. Keeping this in view, I have employed as few technical terms as possible, especially at the commencement, so that the student may glide into Chemistry without having first to toil through a difficult chapter on the terminology of the science, which he can never appreciate until he has become acquainted with the examples which serve to illustrate its application. Convinced, by experience, of the great assistance afforded to the learner by referring him to a simple illustrative experiment, I have introduced, generally in smaller type, a description, and in most cases a wood-engraving,* of the experiments which I have found most useful in illustrating lectures, hoping that these may prove of These were drawn by Mr Collings and engraved by Mr Hart, to whom I feel much indebted for their patient endeavours to represent faithfully the various forms of apparatus. service in fixing the attention of the student, and may assist those who are desirous of performing such experiments for their own instruction, or for that of a class. In explaining chemical changes by equations, I have, as a general rule, employed symbols representing combining weights (or equivalents), and not atoms, of the elements. Had the work been intended for advanced students, I should have hesitated to incur the reproach of obstinate conservatism, or of being behind the chemical spirit of the time, though even then, which of the more advanced systems was to be adopted would have been a very formidable question, for at present the different modes of representing chemical changes are almost as numerous as chemical writers. When the atomic or molecular system of notation affords a clearer explanation, I have endeavoured to give the student the benefit of it, and this of course occurs most frequently in the department of Organic Chemistry, where the elements concerned in the formation of compounds are few, and atomic constitution becomes of greater importance. In such cases I have represented the atoms of elements by the barred symbols (0, €, &c.), and have adopted essentially the same atomic and molecular formulæ as have been employed by my colleague, Professor Miller, in the later editions of his "Elements of Chemistry."* In general, English weights and measures, and Fahrenheit thermometric degrees, have been employed, as conveying more clearly to the beginner the absolute values expressed, since the mental effort of converting what must still be called the continental systems, slight though it be, might have the effect of diverting the attention of the reader from the chemical question under consideration. The various calculations have been conducted in the simplest arithmetical form, because the more compendious algebraical expressions are not so generally intelligible, and when the principle is once understood, a general algebraical formula for the calculation is easily constructed by the learner. The special attention devoted to Metallurgy and some other I must confess myself under heavy obligation to Dr Miller's splendid volume on Organic Chemistry, the luminous summaries which it contains having frequently spared me the trouble of referring to the original memoirs. branches of Applied Chemistry, will render the work useful to those who are being educated for employment in manufacture. The military student will find more than the usual space allotted to the chemistry of the various substances employed in warlike stores. In fine, it has been my endeavour to produce a Treatise on Chemistry sufficiently comprehensive for those studying the science as a branch of general education, and one which a student may peruse with advantage before commencing his chemical studies at one of the colleges or medical schools, where he will abandon it for the more advanced work placed in his hands by the professor. I am not without hope that this book may also be found useful in enabling the student who has acquired his knowledge of Chemistry with the help of the older system of notation in equivalents, to pass, should he deem it advisable, by an easy transition, into the use of atomic symbols and unitary formulæ. WOOLWICH, January 1867. C. L. B. In the following pages, the smaller type contains not only the descriptions of experiments, but all such matter as would be of less importance to a student desiring only a general knowledge of the subject without going into details. |