PREFACE. 



Of the fundamental importance of the most accurate 

 attainable knowledge concerning the true atomic weights 

 of the elements there can be no two opinions. If the enor- 

 mous mass of known facts relating to the properties of 

 matter is ever to be brought under wide generalizations, it 

 is with the simple substances that a beginning must be 

 made, and with the simplest property of these substances, 

 the relative weights of their ultimate particles. Berzelius 

 held this view and the labors of Mendelejeff, Meyer and 

 others leave no question as to the fact of a relation between 

 the atomic w^eights and the properties of simple and com- 

 pound matter. Accurate information on the subject, how^- 

 ever, is not easily attainable ; different writers on chemistry 

 follow different authorities, and some even take a mean 

 between the results arrived at by experimenters of different 

 degrees of skill and accuracy, or assume some convenient 

 number without experimental foundation. Nowhere, to my 

 knowledge, is there even an approximately complete list of 

 the determinations that have been made. 



Forced back, myself, upon the original memoirs for in- 

 formation, I believed that I should do other chemists a 

 service in presenting to them a short but systematic digest 

 of each investigation on the subject, including the following 

 points, so far as they could be ascertained : The nature of 

 the material experimented upon, and the method of its 

 preparation; the experimental method adopted to effect the 

 determination, and the number of experiments; the mean 

 result reached by the experiments, and the extreme differ- 

 ence between the results; such a record of the constants 

 employed in the calculation as will enable any one to recal- 

 culate the results for different constants; and the place in 

 literature where the original paper is to be found. 



The following pages are the result. From the information 



