AUTHOES PREFACE. ABOUT three years ago I wrote an article for Ladenburgs Handworterbuch der Chemie containing in a concise form an exhaustive account of the history of the Organic Dyestuffs. This article was also published separately, and its good reception induced me to produce the present work, which I have based as far as possible upon the earlier one. The article in question was not complete in itself, and in the present instance certain sections which came under other headings in the Handworterbuch have been added. New material has also been supplied through the advances made in the coal-tar colour industry and in our scientific knowledge of the constitution of dyestuffs during the last three years. Again, some subjects have been dealt with at a greater length than was permitted by the somewhat limited space of the Handworterbuch Conse- quently, the subject-matter of the earlier work has been submitted to a thorough revision, and the systematic classification of dye- stuffs into natural chemical groups attempted in the original book has been carried out in a more complete manner, owing to the advances made in our knowledge of their constitution. The present work cannot therefore be regarded as a second edition of the article from the Handworterbuch and as I have sought to give the whole the form of a small chemical handbook, dealing with dyestuffs from a scientific standpoint, I have selected The Chemistry of the Organic Dyestuffs as a suitable title. In this work, as in the previous one, considerable weight has been laid upon the relationships existent between the constitution and tinctorial properties of the dyestuffs. I have thought it advisable to deal only with the principles involved in the manufacture of individual dyestuffs, as details for their technical production are unreliable, owing to the continuous developments taking place in the industry in question. The application of dyestuffs to textile fibres has been dealt with rather more fully than in the earlier work, but not at a greater length than is in accordance with the character of the book. To technologists requiring further details of the application of dye- stuffs I can recommend Hummers excellent work on The Dyeing of Textile Fabrics Basle, October 1888. TRANSLATORS PREFACE. LITTLE remains for us to add to Prof. Nietzkis account of the design and character of his book. It has met with very general appreciation in Germany, and this made us think that a trans- lation might be of service to English workers in the field which the book covers. Some time has elapsed since the original appeared, and we have attempted as far as possible to bring the subject-matterup to date. New colouring-matters have been introduced without altering Prof. Nietzkis method of classification, a method which has been very generally adopted since its appearance. In some cases Primuline, Thioflavine Pyronine, c. new sections might have been desirable we preferred, however, to leave the book in its original form. The figures in the text apply to the references given on pages 273-288. The references have been left as in the original, with the one exception that, wherever possible, the English-Patent number has been added. Our thanks are due to the Directors of the Farbwerke Hochst Meister, Lucius,and Briining and of the Farbenfabriken, vortnals F. Bayer and Co., Elberfeld, for the ready kindness with which they placed ample information at our disposal. Paisley, May 1892. CONTENTS... --This text refers to the Paperback edition.