PREFACE. 



This collection of papers upon the atomic weights of certain common ele- 

 ments embodies the results of researches of which the experimental work has 

 been carried on in the Chemical Laboratory of Harvard College during the 

 past six years. All of the papers have already been published separately both 

 in American and in German periodicals, and references to the places of publi- 

 cation are given at the beginning of each article. 



In reprinting the papers in the present form the only changes of importance 

 which have been made are due to more exact knowledge of the fundamental 

 atomic weights upon which the calculations depend. Many recent investiga- 

 tions, especially that upon the analysis of lithium chloride and perchlorate by 

 Richards and Willard,^ have shown that the atomic weight of silver, referred to 

 oxygen 16.000, is certainly as low as 107.880, and possibly as low as 107.870. 

 Since the International Committee upon Atomic Weights at the date of writ- 

 ing have chosen the higher of these values, the calculations have been based 

 upon the value 107.880 for silver, the atomic weights of chlorine and bromine 

 being assumed to be 35.457^ and 79.916 ^respectively. The effect of a change 

 from 107.880 to 107.870 in the atomic weight of silver is, however, plainly 

 indicated in each instance. 



In the case of cadmium the subject-matter of two papers has been rear- 

 ranged in a manner differing considerably from that of the original publica- 

 tion. In the case of iodine the subject-matter of two papers has been com- 

 bined in one. In all other cases the presentation is essentially that of the 

 original publication. 



Generous grants from the Carnegie Institution of Washington have been 

 of the greatest assistance in the progress of this work, while grants from the 

 Cyrus M. Warren Fund for Research in Harvard University have materially 

 aided all the investigations. G. P. Baxter. 



1 Publications of the Carnegie Institution, No. 125 (1910); Jour. Amer. Chem. Soc., 32, 4. 



2 Publications of the Carnegie Institution, No. 28 (1905); Jour. Amer. Chem. Soc, 27, 

 459; Zeit. anorg. Chem., 47, 56. 



^ Proc. Amer. Acad., 42, 201 (1906); Jour. Amer. Chem. Soc, 28, 1322; Zeit. anorg. 

 Chem. Soc, 389. (See page 49.) 



Ill 



