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III. 



MAGISTETIC EESOLUTION OF THE SPECTEUM LINES 

 OF NIOBIUM. 



By EOBEET jack, M.A., Ph.D., D.Sc, 



Lecturer in Physics, Queen's University, Belfast. 



Read June 10. Published Septembeii 6, 1912. 



I. Inteoduction and Proceduke. 



There is still mucii to be done towards finding the connexions between the 

 spectrum lines of the elements. A new means of attacking this problem was 

 given by the discovery in 1896 of the Zeeman Effect by Professor Zeeman 

 of Amsterdam ; and since that date much time has been given to the 

 investigation of this Effect in the spectrum lines of various elements. Such 

 investigations have resulted in the finding of some new laws, not only 

 establishing a connexion between some lines in the spectrum of the same 

 element, but also between these lines and the lines in the spectra of 

 chemically-related elements. Having studied the Zeeman Effect in the 

 elements molybdenum and tungsten,* both of which belong to the si.xth 

 group in the periodic system, I have thought it desirable to examine the 

 Zeeman Effect in niobium, which occupies the same position in the fifth group 

 as molybdenum does in the sixth. The objects of the research therefore were 

 to obtain a record, as complete as possible, of the Zeeman Effect on the 

 spectrum lines of niobium, to test with these results the laws already wholly 

 or partly established, to compare the results for this element with those for 

 other substances, and to seek for new relations. 



The grating apparatus of the Physical Institute, Gottingen, was used. 

 Eeferences relating to this and to the method of obtaining the photographs 

 will be found in my above-mentioned Dissertation. The carbon electrodes 

 were coated with a thin layer of niobium chloride sublimate. The duration 

 of exposures varied between two and three hours ; but owing to an 



* " Zeeman-Effekt un Wolfram uiid Molybdan," Diss., Gottingen, 1908. Annalen der Phvaik, 

 iv, 1032, 1909. 



