222 



Profs. G. D. Liveing and J. Dewar. [June 6, 



It would follow that the production of nitric and nitrous oxides 

 with nitrogen, in proportions varying according to the conditions, is 

 due to subsequent changes occurring between nitrous acid and cupric 

 or cuprous nitrate or nitrite in presence of nitric acid. 



I propose to continue these researches, substituting other metals 

 for copper, especially those which are supposed to yield primarily 

 nitrous acid. 



In conclusion, I would express my thanks to Mr. Vernon Harcourt 

 for the suggestion which proved of so much value, and to the 

 authorities of the University for affording me facilities for this 

 investigation. 



[Postscript. — Since the above was written experiments have been 

 made in which the reaction between the copper and dilute nitric acid 

 (sp. gr. = 1*1723), heated to 27° C, was successfully prevented for 

 some time, even in absence of urea, by substituting a current of air 

 for that of carbonic acid. — May 22nd, 1889.] 



VI. " Notes on the Absorption- Spectra of Oxygen and some of 

 its Compounds." By G. D. Liveing, M.A., F.R.S., Professor 

 of Chemistry, and J. Dewau, M.A., F.R.S., Jacksonian 

 Professor, University of Cambridge. Received May 23, 

 1889. 



The absorption -spectrum of oxygen has engaged attention not only 

 on account of the important part which that element plays in the 

 world, but because of the remarkable character of that absorption, so 

 strongly marked, exhibiting bands of two essentially different classes, 

 and extremely variable under varying circumstances of condensation 

 and combination. 



It may be expected that the study of it will reveal something new 

 as to the nature of the molecular changes brought about by different 

 circumstances, physical and chemical. 



We have already published, notes of some of our experiments on 

 this subject ('Phil. Mag.,' September, 1888), and these confirm 

 generally the observations of Egoroff, Janssen, and Olszewski. 



The accompanying diagram represents the absorption of 18 metres 

 of ordinary oxygen gas at a pressure of about 97 atmospheres, 

 that is, of a mass of oxygen rather greater than is contained 

 in a vertical column of equal section of the earth's atmosphere. 

 Under the circumstances of the experiment the absorptions A and B 

 are very black, and the lines of which they are composed appear much 

 broader than in the ordinary solar spectrum. The other bands are 

 all diffuse at their edges, and, so far as we have observed, unresolv- 

 able into lines. It will be noted that the complete absorption of»the 



