X PRINCIPLES OF CHEMISTRY 



the first and most important aim of this book. The time has ar- 

 rived when a knowledge of physics and chemistry forms as im- 

 portant a part of education as that of the classics did two centuries 

 ago. In those days the nations which excelled in classical learning 

 stood foremost, just as now the most advanced are those which are 

 superior in the knowledge of the natural sciences. I also wished 

 to show in an elementary treatise on chemistry the palpable ad- 

 vantages gained by the application of the periodic law, which I first 

 saw in its entirety in the year 1869 when I was engaged in writing 

 the first edition of this book, in which, indeed, the law was first 

 enunciated. Then, however, this law was not established so firmly 

 as now, when so many of its consequences have been verified by 

 the researches of numerous chemists, and especially by Roscoe, 

 Lecoq de Boisbaudran, Nilson, Brauner, Thorpe, Carnelley, Laurie, 

 Winkler, and others. As the entire scheme of this work 2 is sub- 

 jected to the law of periodicity, which may be illustrated in a 



ance with some special chemical question, studying the original treatises of the 

 investigators of the subject (at first, under the direction of experienced teachers), 

 because in working out particular facts the faculty of judgment and of correct 

 criticism becomes sharpened ; in the third place, to a knowledge of current scien- 

 tific questions through the special chemical journals and papers, and by inter- 

 course with other chemists. The time has come to turn aside from visionary 

 contemplation, from platonic aspirations, and from classical verbosity, and to 

 enter the regions of actual labour for the common weal, and to prove that the 

 study of science is not only an excellent education for youth, but that it instils 

 the virtues of labour and truth, and creates solid national wealth, material and 

 mental, which without it would be imattainable. Science, which deals with the 

 infinite, is itself without bounds. 



2 I recommend those who are commencing to study chemistry with my book 

 to first learn only Ballot is printed in the large type, because in that part I have en- 

 deavoured to concentrate all the fundamental, indispensable knowledge required 

 for the study of chemistry. In the footnotes, printed in small type (which I advise 

 being read only after the large text has been mastered), certain details are dis- 

 cussed ; they are either further examples, or debatable questions on existing ideas 

 which I thought indispensable to lay before those entering into the sphere of 

 science, or certain historical and technical details which might be withdrawn 

 from the fundamental portion of the book. Without intending to attain in my 

 treatise to the completeness of a work of reference, I have still endeavoured 

 to express the principal developments of science as they concern the chemical 

 elements viewed in that aspect in which they appeared to me after long con- 

 tinued study of the subject and participation in the contemporary advance of 

 knowledge. 



