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THE object of this book is twofold. Firstly, it is intended to supply chemical lecturers and teachers with a useful repertoire of experiments, suitable for illustrating upon the lecture table the modes of preparation, and the properties, of the non-metallic elements and their commoner and more important compounds. I have therefore given such full directions for the preparation and performance of the various experiments described, as will enable any experimenter to successfully repeat them. No mere description of experiments, however minute, can entirely take the place of experience, but it has been my endeavour throughout this book to give such details, resulting from my own experience, as shall meet as far as possible the lack of experience in others.
No account of any experiment has been introduced into the book upon the authority solely of any verbal or printed description, but every experiment has been the subject of my personal investigation, and illustrated in every case, with the exception of three,' by woodcuts made from original drawings.
What should be and what should not be included under the head of experiments suitable for illustration upon the lecture table' may be a matter for difference of opinion, and must depend often upon circumstances. I have excluded for the most part all such experiments as are merely illustrative of the ordinary laboratory processes of qualitative analysis ; also all experiments illustrating the action of substances upon animal
1 Figs. 1 and 24, ‘Inorganic Chemistry,' Frankland and Japp; fig. 203, Ganot's Physics.'
life, and, lastly, such as are of either so critical or dangerous a nature as to involve the adoption of any special or elaborate precautions.
Throughout the book the French metrical system has been adopted, but as the English mind, even of scientific men, often continues to conceive of measures of length in inches, long after it has acquired the habit of thinking in grams and cubic centimetres, I have added, when deemed desirable, the English equivalent of the French measures of length. It will be convenient to remember that for all practical purposes 25 millimetres, or 2.5 centimetres, are equal to one inch.
For the convenience of such teachers as may not have ready access to books of reference, I have added, in the form of an appendix, a number of important and useful tables.
Secondly, it is my object to furnish the chemical student with a book which shall serve as a companion to the lectures he may attend—a book in which he will find fully described most, if not all, of the experiments he is likely to see performed upon the lecture table, and which will therefore relieve him from the necessity of laboriously noting them and often sketching the apparatus used. In this way the student will be spared much unnecessary and distracting work during the lecture, and will therefore be better able to give his undivided attention to the explanations or arguments of the lecturer.
Further, to meet the wants of the chemical student, I have given the equations representing the various reactions which are described in the book; and, although this work is not designed to take the place of any existing text-book, it has been so arranged that the student may learn from it the methods of preparation and most of the important properties of the non-metallic elements and their more common compounds.
G. S. N. ROYAL COLLEGE OF SCIENCE, SOUTH KENSINGTON, W.: