1902.] 



some Lines in the Spectrum of Lithium. 



165 



The only important differences occur in the lines of the first subor- 

 dinate series. Exner and Haschek have given the wave-lengths of 

 three lines in the spark spectrum* as 2815-55, 3232*91, and 4603-10. 

 The last is described as reversed. Eder and Valenta have given the 

 wave-length of the blue line in the Bunsen flame spectrum as 4602 -4,f 

 and as 4602-46 in the spark spectrum when a condenser was used. J 

 They described the latter measurement as that of the middle of a broad 

 dark line, the less refrangible wing of which was stronger than the 

 other, and diffuse towards the red. They also gave measurements of 

 five other lines, and these agree closely with the arc lines given by 

 Kayser and Eunge. Professor Hartley recorded four lines in the 

 oxyhydrogen flame spectrum of lithium chloride § corresponding to the 

 first, fourth, sixth and eleventh of the lines in the above table. The 

 blue line was measured in the flame spectrum on four plates, and the 

 results differed only in the second decimal place, the figures in which 

 were 8, 7, 6 and 7. Professors Liveing and Dewar made some observa- 

 tions by eye on the appearance of the blue line in the arc spectrum 

 which led them to believe there were two lines, a strong one with a 

 weak line on the more refrangible side,|| and Kayser and Eunge, after 

 referring to this, say : — *fl " Wir haben nur bei zwei Aufnahmen neben 

 der Hauptlinie eine zweite schwache umgekehrte Linie bei 4603*13 

 erhalten ; da aber hier eine Eisenlinie liegt, glauben wir, dass dies eben 

 die Eisenlinie ist, welche sich durch den hellen Hintergruncl der 

 Lithiumlinie umgekehrt hat." 



The wave-length of the line which Kayser and Eunge attributed to 

 iron agrees with that obtained by the author for the bright line in the 

 flame spectrum, and by Exner and Haschek for the reversed line in a 

 spark spectrum. It was decided in view of these differences to take a 

 series of photographs of the arc spectrum of lithium, using the carbo- 

 nate of lithium on carbon poles, and to study especially the appearances 

 of the blue line. The results will now be briefly described. 



A G-ulcher arc lamp with vertical carbons was used. When the arc- 

 was started with a quantity of lithium carbonate on the carbons, a 

 large proportion of the salt was freely volatilised and expelled in the 

 form of a dense vapour. As the arc lamp was placed, the magnetic field 

 produced by the feed mechanism caused the bulk of the vapour to be 

 expelled in the direction of the collimator. Photographs of the 

 spectrum taken at this early stage show the line as a very broad bright 

 line extending from 4610'4 to 4593 - 5, with a narrow dark line extend- 



* ' Sitzber. kais. Akad. Wien,' vol. 106, Abth. 2a (1897), p. 1133. 

 f 'Denkschr. kais. Akad. Wien,' toI. 60 (1893). 

 X ' Denkschr. kais. Akad. Wien,' vol. 67 (1898). 

 § 'Phil. Trans./ A, vol. 185 (1894), p. 177. 

 || « Pbil. Trans.,' vol. 174 (1883), p. 215. 

 f Ibid., p. 20. 



