THE INFLUENCE OF ATMOSPHERES OF NITROGEN 

 AND HYDROGEN ON THE ARC SPECTRA OF IRON, 

 ZINC, MAGNESIUM, AND TIN, COMPARED WITH THE 

 INFLUENCE OF AN ATMOSPHERE OF AMMONIA. 



By Royal A. Pouter. 



Presented by C. R. Cross, May 14, 1902. Received October 8, 1902. 



It has been frequently assumed that chemical reactions in the electric 

 arc have a considerable influence on the character of its radiations.* It 

 seems not unreasonable to expect that the oxidation of the electrodes at 

 high temperature in air would tend to increase the intensity over that 

 obtained when the arc is operated in nitrogen alone. This presumed 

 higher temperature might be sufficient to produce atomic vibrations 

 entirely distinct from the vibrations at a lower temperature. If the 

 atmosphere does have any such influence, the effect might be apparent 

 in the spectrum of the arc. 



In the case of a hydrogen atmosphere f the most marked effects on the 

 arc spectra of iron, zinc, magnesium, and tin have been found to be a 

 general diminution of intensity and a change of relative intensity among 

 the lines. The lines relatively enhanced by hydrogen are spark lines. 



Liveing and Dewar % have noted the effect of atmospheres of hydrogen 

 and nitrogen on a number of lines in the magnesium arc and spark, and 

 of these and other atmospheres on the cyanogen § bands in the carbon 

 arc, but as far as I am aware no extensive study has been made of the 

 influence of nitrogen and ammonia on the arc spectrum of metals. From 



* Liveing and Dewar, Proc. Roy. Soc, 30, 161 (1880) ; 32, 192 (1881) ; O. H. 

 Basquin, Astroph. Jour., 14, 11-12 (1901) ; A. S. King, Astropli. Jour., 14, 329- 

 330 (1901). 



t II. Crew, Astroph. Jour., 12, 107 (1900) ; Liveing and Dewar, Proc. Roy. Soc, 

 32, 192, 402-403. 



| Proc. Hoy. Soc., 32, 189-203 (1881). 



§ Ibid., 30, 152-102. 



