﻿certain Spectral Lines of Zinc and Titanium. 403 



give lines the wave-lengths of which are much smaller 

 than those given by the arc spectra of brass or of pure 

 ^inc. 



It may be seen that in no instance in the spark spectra of 

 either pure zinc or brass do the lines X 4810 and X 4722 

 attain the maximum values given by Exner and Haschek, 

 that is X 4810*85 and X 4722*50 respectively, although the 

 lines show a displacement in the spark spectra of pure zinc 

 compared with those of the arc. 



Titanium. 



The following table contains the measurements of the 

 titanium lines. 



To obtain the arc and spark spectra of tilanium, pieces of 

 the metal about the size of a pea were placed in the electrode 

 clips and the current passed between points which had been 

 set opposite to each other. The spark was in each case 

 vertical and parallel to the slit. Many photographs of the 

 spectra were taken, the time of exposure in the case of the 

 spark being varied between 2 seconds and 1 minute, and in the 

 case of the arc the strength of the current was varied between 

 4 and 18 amperes. In order to study the influence on the 

 wave-lengths of the titanium lines due to the presence of 

 other elements in the arc and spark, titanium potassium 

 fluoride was used. This salt was dissolved in hot nitric 

 acid which deposited a gelatinous precipitate on cooling, but 

 this went partly into solution on shaking. Carbon elec- 

 trodes were used, and some of this solution of the titanium 

 salt was placed on the lower one. Then photographs were 

 taken of the spark and arc spectra, varying the time of ex- 

 posure and the strength of the current as with the metallic 

 electrodes. As there were no titanium lines obtained by this 

 means in the arc spectrum when a current of 4 amperes was 

 used, a paste of the salt was made with water, and some of 

 this was placed on the lower electrode, and by this method 

 some lines of weak intensity were produced. On increasing 

 the strength of the current more lines appeared on the plate, 

 but with 18 amperes the salt, w T hich seemed to be driven 

 away from the region of the spark, melted and ran down 

 the side of the electrode, so that no titanium lines appeared 

 on the photograph. The thirteen titanium lines which 

 were chosen for the investigation lie between X 4000 and 

 X3300. 



2 D 2 



