BAXTER. — A REVISION OF THE ATOMIC WEIGHT OF RROMINE. 209 



perfectly transparent and of a light yellow color even after the first 

 fusion in air. 



A few shreds of asbestos displaced from the crucible, together with 

 an occasional trace of silver bromide which escaped the crucible, were 

 collected upon a tiny filter paper which was then ignited in a porcelain 

 crucible. Before being weighed the ash was either treated with a drop 

 of nitric and hydrobromic acids and again heated, or else was heated 

 for some minutee in a current of air and bromine. 



The filtrate and washings were evaporated to small bulk. The 

 precipitating fiask and all other glass vessels used in the analysis 

 were rinsed with ammonia and the rinsings were added to the evapo- 

 rated filtrate and wash waters. The whole was then tested in a nephel- 

 ometer for silver and the quantity found was estimated by comparison 

 with standard silver solutions. In most cases the correction thus 

 obtained was less than one tenth of a milligram. 



The asbestos which formed the felt in the Gooch crucible, after 

 having been shredded, was digested for some hours with aqua regia 

 and was then thoroughly washed with water. Before the empty 

 crucible was weighed, the felt was ignited with a Bunsen burner. 

 Crucibles thus treated and then heated to 180° after being moistened 

 with water did not change in weight. 



In the following table are cited all the analyses which were com- 

 pleted without accident. Vacuum corrections of — 0.000031 for every 

 apparent gram of silver and of -f 0.000041 for every apparent gram of 

 silver bromide are applied. ^^ The atomic weight of silver is assumed 

 to be 107.930. 



The platinum plated brass weights were standardized from time to 

 time and were found to retain their original values within a very few 

 hundredths of a milligram in all cases. 



The Ratio of Silver Bromide to Silver Chloride. 



The ratio of silver bromide to silver chloride was determined much 

 as described in previous papers upon the atomic weight of iodine.^^ 

 Pure silver bromide was prepared by precipitation of silver nitrate 

 with an excess of ammonium bromide. The silver employed was 



" The specific gravity of llie weights was determined to be 8..3. 



The specific gravity of silver has been found to be 10.49. Richards and "Wells, 

 Publications of the Carnegie Institution, No. 28, 11. 



The specific gravity of fused silver bromide has been found to be G.473. 

 Baxter and Ilines, Amer. Chem. J., 31, 224. 



20 Baxter, These Proceedings, 40, 4;]2 (1004) ; 41, 75 (1905). 



VOL. XLII. — 14 



