Z PREFACE. 



he will find in them, the experienced chemist will, in most 

 cases, I think, be able to decide which determination offers 

 the best guarantees for accuracy, or at least between which 

 determinations his choice must lie, forming his judgment to 

 a great extent independently of the comparative reputation 

 of the observers — not always a safe guide where one is, in a 

 general way, the unquestionable superior of the other — and 

 no guide at all when the names carry on the whole an equal 

 weight. As a record of the direction investigations have 

 taken and of analytical methods of the most exact character 

 also, I hope that this digest may not be without value. 



As this compilation would serve rather to mislead than 

 to assist investigators, unless it be accurate and practically 

 exhaustive, it seems proper to explain the manner in which 

 it has been prepared. Believing it best to work independ- 

 entl}'' of any previous compilations, I selected as my base 

 the three great German journals — Poggendorjfs Annahny 

 Liebig's Annalen^ and JErdmann's Journal filr Praktische 

 Chemie. My choice was determined not only by the posi- 

 tion these journals take in chemico-physical science, but by 

 the fact that their indices are admirable, and their tone 

 cosmopolitan ; all of them, until lately, having furnished 

 their readers with the scientific news of the time, and with 

 abstracts from and translations of the important papers 

 published elsewhere and in whatever language, as well as 

 with original investigations. The indices of these journals 

 I read through from beginning to end, making an extract 

 of every entry which bore on the subject of atomic weights, 

 or which I suspected might do so. In studying the arti- 

 cles thus reached, every reference to other atomic weight 

 determinations was preserved, and the originals, so far as 

 possible, sought out; a task in which the Royal Society's 

 Catalogue of Scientific Papers was of the greatest assistance. 

 Having exhausted the supply of information in these jour- 

 nals, I turned to Berzelius' Jahresbcricht, and to its continua- 

 tion edited by Kopp, Liebig et al., and made a study of their 

 contents by the same method. Later, I made a similar 

 systematic study of the Amiales de Chimie et de Physique, the 

 Bericht der Deutschen Chemischen Gesellschaft, tlie Chemical 



