44S TRANS. ST. LOUIS ACAD. SCIENCE. 



of action of the iodine on the walls of the glass tube it becomes 

 united with alkalies, this hydrogen, finally, is liberated entire- 

 ly, and, instead of an iodine tubc^ we have a hydrogen tube 

 developed. 



On taking a tube containing iodine in an atmosphere of hydro- 

 gen, I found that at first the hydrogen lines wery very bright at 

 ordinary temperatures. However, after a short time, and on 

 continued passage of the spark, the lines became more and more 

 faint, and finally scarcely perceptible. On then heating the tube 

 the hydrogen lines became very brilliant, and on cooling again 

 disappeared almost entirely. On opening such a tube, dense 

 fumes of hydriodic acid were emitted. 



These experiments, I think, show conclusively: firstly, the 

 cause of disappearance of iodine in tubes on long-cotiti)iued 

 sparking ; and, secondly, xvhy the iodine lines are replaced by 

 hydrogeu lines during that process. 



I shall probably be in a position to make further communica- 

 tion on the sparking of iodine in the near future. 



Clicmical Laboratory Wasliington University, St. Louis, Mo., U. S. A. 



