BAXTER. — ATOMIC WEIGHT OF IODINE. i.) 



tilization actually took place was certain for two reasons. In the first 

 place, the weight of the bromide in most cases became constant within 

 a few hundredths of a milligram after once being heated, although sub- 

 sequently the salt was maintained at a temperature slightly above its 

 melting point for at least an hour. In the second place, the perforated 

 cover and hard glass delivery tube for the bromine, when rinsed with 

 ammonia and the solution treated with hydrochloric acid in excess, gave 

 no visible trace of opalescence. Before the salt was allowed to solidify 

 it was maintained above its fusing point in air for a few minutes to 

 eliminate dissolved bromine. 



The silver bromide resulting from each analysis was converted into 

 silver chloride by heating in a current of pure dry chlorine in a similar 

 fashion.* Here also constant weight within a very few hundredths of a 

 milligram was easily obtained, and as before the perforated cover and 

 inlet tube were free from weighable amounts of chloride. It lias already 

 been shown that silver chloride and silver iodide, when fused in an 

 atmosphere of the corresponding halogens and then in air, retain none of 

 the halogen. f The quartz crucibles remained almost absolutely constant 

 in weight during these experiments. From the ratio between the origi- 

 nal silver iodide and the silver chloride the atomic weight of iodine was 

 calculated. 



The following vacuum corrections were applied : silver iodide, 

 +0.000071; silver bromide, +0.OUO046 ; silver chloride, +0.000075.$ 

 The analyses of Series II were obtained through the bromide, those of 

 Series III are the results from the previous paper recalculated from the 

 higher atomic weight of chlorine, with the exception of Analysis 18, which 

 was made subsequently. All completed analyses are recorded in the 

 tables. Several were lost, owing to breaking of the crucibles. 



The Ratios p.etween Silver, Iodine, and Silver Iodide. 



In the earlier paper determinations of the ratios of silver to silver 

 iodide and iodine were described. It remained to determine the ratio of 

 iodine to silver iodide. For this purpose iodine was purified as before 



* For preparation ;md purification of chlorine, see earlier paper. 



t See previous paper. Also Richards and Wells, loc. eit , page 59, and Kothner 

 and Aeuer, Liebig's Ann., 337, 127. 



t The value for the specific gravity of silver chloride is assumed to be 5.56, as 

 determined by Richards and Stull in this laboratory. In the previous paper this 

 value was incorrectly taken as 5.62. 



