350 Mr Ramage, On the Distribution and Spectra 



On the Distribution and Spectra of Metallic Vapours in Electric 

 Sparks. By Hugh Ramage, B.A., St John's College. 



[Bead 18 January 1904.] 



Some peculiarities observed in certain lines in the arc and 

 spark spectra of lithium were described by the writer in a paper 

 communicated to the Royal Society in November 1902 1 . The 

 blue line, for instance, was found to be broadened in the spectra 

 of the regions near the negative element both in the arc and 

 spark. The broadening of this line was easily observed and 

 photographed in the spectrum of the spark when no Leyden jar 

 was used, and a slight broadening was observed near the positive 

 electrode when no air break was inserted in the secondary circuit 

 and no precautions were taken to keep the electrodes cool. Between 

 these two regions the line was thin and sharp. A further study 

 of electric sparks in air at ordinary pressures has since been made 

 and the results will now be described. 



Two clean platinum wires were fixed horizontally in a holder 

 with their adjacent ends about a centimetre apart. When they 

 were connected with an induction coil and the coil was started, 

 the flame surrounding the sparks had the characteristic colour 

 due to the gases of the atmosphere. The anode was then 

 moistened with a solution of a compound of lithium and the 

 coil again started. Flashes of red were observed in the sparks, 

 but when the anode was heated the flame round the sparks 

 became red throughout its whole length, and there were seen 

 in its spectrum the red lithium line and the yellow sodium lines. 

 It would appear from this that some of the lithium and sodium, 

 present as an impurity, were vapourised by the heat and reduced 

 to the free state by the spark, otherwise, according to Gouy's 

 observations 2 , no colour should be communicated to a flame in 

 presence of so much free oxygen. A quantity of lithium salt was 

 then fused on the end of one of the wires, forming a globule about 

 2 mm. diameter. When the coil was started with this as the 

 anode the red flashes were more frequent and brighter than 

 before, and the orange line of lithium was also observed in the 

 spectrum, but it was extremely feeble. When an air break was 

 inserted in the secondary circuit no red colour was observed as 

 long as the anode remained cold. 



1 Five. Roy. Soc, Vol. lxxi. p. 161. 

 3 Comptes Rendus, Vol. lxxxiii. p. 70. 



