THE CHEMISTRY OF THE COAL-TAR COLOURS. TRANSLATED FROM THE GERMAN OF DR. R. BENEDIKT, AND EDITED, WITH ADDITIONS, BY E. KNECHT, PH.D., F.I.C., HEAD MASTER OF THE CHEMISTRY AND DYEING DEPARTMENT OF THE TECHNICAL COLLEGE, BRADFORD; EDITOR OF THE "JOURNAL OF THE SOCIETY SECOND EDITION, REVISED AND ENLARGED. LONDON: GEORGE BELL AND SONS, YORK STREET, COVENT GARDEN. 0441 1346 1889 PREFACE. ALTHOUGH England may rightly be called the birthplace of the coal-tar-colour industry, it is a remarkable fact that the English literature on the subject is very scanty, and that which does exist is now almost obsolete, owing to the rapid strides which have been made during the last ten years in the manufacture of coal-tar colours. Numerous elaborate works are published from year to year on this important subject both in France and in Germany, but more especially in the latter country, by means of which manufacturers and students are continuously kept informed of the latest methods and theories. The want of a text-book of this kind containing a concise account of all the more important coal-tar colours has long been felt by the author, and has prompted him to undertake the present translation of Dr. Benedikt's excellent little work, " Die Künstlichen Farbstoffe," which has met with such success in all parts of the Continent where German is spoken. The author may therefore not be considered too sanguine in hoping that the present volume will meet with some success in this country, not only as a stepping-stone for those who wish to make the subject a special study, but also among students of chemistry in general. It will also be found useful to those engaged in the dyeing and printing of textile fabrics. The manufacture of coal-tar colours is an industry which cannot possibly thrive by the old "rule of thumb" way of doing business. It is a well-known fact that those who succeed best in this industry now-a-days spare no means to bring the highest scientific training to bear on the subject, while those who are "penny wise and pound foolish" endeavour to save the expense of adequate scientific advice, and thus ultimately find themselves completely surpassed by more enlightened rivals. BRADFORD, E. K. PREFACE TO THE SECOND EDITION. THE large number of new coal-tar colours which has come into the market since the publication of the first edition has necessitated a considerable increase in the size of the present volume. The author has also considered it advisable to rearrange the matter so as to bring the whole of the raw products under one heading, and to make that chapter as complete as the conciseness and scope of the work would allow. During the same period the scientific development of the subject has gone rapidly ahead, and the constitutional formulæ of many products of which we then knew little more than the empirical formule have been definitely proved. With the exception of these alterations, the general arrangement of subjects does not differ materially from that of the first edition. At the suggestion of my friend, Mr. Christopher Rawson, the symbolic rendering of the "azo" group, which is generally represented as -N-N-, has been altered throughout the work to N:N-, because the two bonds joining the nitrogen atoms might sometimes be misleading to beginners on account of the similarity they have to the sign "equals." |