CONTRIBUTIONS FROM THE CHEMICAL LABORATORY 

 OF HARVARD COLLEGE. 



A REVISION OF THE ATOMIC WEIGHT OF IODINE. 

 SECOND PAPER. 



By Gregory Paul Baxter. 



Presented by T. W. Richards March 8, 1905. Received March 16, 1905. 



Very recently, in an investigation upon the atomic weight of iodine,* 

 the value 126.975 for this constant was obtained as the average from 

 three closely agreeing ratios. Experiments subsequent to the publica- 

 tion of this research have shown that the results of all three methods 

 were subject to slight errors, and that the atomic weight of iodine is even 

 slightly higher than the above value. Following is a description of these 

 experiments, with details where the processes differed from those pre- 

 viously described. For further information the first paper should be 

 consulted. 



The Ratio of Silver Iodide to Silver Bromide and 

 Silver Chloride. 



In the previous investigation the ratio Agl : AgCl was determined by 

 heating silver iodide in a current of chlorine in six experiments which 

 yielded an average result of 126.975, calculated upon the basis of silver 

 107.93 and chlorine 35.467. The latter value for chlorine was a pre- 

 liminary one, found in an investigation by Richards and Wells then in 

 progress in this laboratory. Later experiments by these chemists have 

 shown that the atomic weight of chlorine is in reality 35. 473, f which 

 necessitates a positive correction for the atomic weight of iodine of 0.010. 

 The corrected value, 126.985, agrees very closely with two determina- 

 tions, made in the course of the earlier investigation, in which silver 

 iodide was heated in a current of carbon dioxide and bromine. Assum- 



* Baxter, These Proceedings, 40, 419 (1904). Also Zeit. anorg. Chem., 43, 

 14 ; and Jour. Amer. Cliem. Soc, 26, 1577. 



t Richards and Wells, Publications of the Carnegie Institution, No. 28 (1905)* 

 Also Jour. Amer. Chem. Soc, 27, 459. 



