[mclennan-zumstein] 



SPECTRA OF LEAD 



11 



Absorption in the infra-red was investigated with one of Hilger's 

 Infra-red Spectrometers, and in the visible and ultra-violet region by 

 Hilger's Quartz Spectrograph of types A and C. Reproductions of 

 the photographs of the absorption spectrum of non-luminous lead 

 vapour are shown in Fig. 1. 



Table I 

 Lead Absorption Spectrum 



The faint absorptions found at A = 2288 A°U and A = 2139 A°U 

 were probably due to traces of cadmium and zinc present as impurities 

 in the lead, as no radiations of these wavelengths were found in either 

 the arc or spark emission spectra of lead. 



No absorption was observed either at A = 10291 A°U or at A = 10500 

 A°U, but it is probable that if any did occur it was masked by the 

 strong radiations of these wavelengths emitted by the furnace. 



The first spectrum shown in Fig. 1 is that of the aluminium 

 spark in air. The second is that obtained with a panchromatic plate 

 of the light from the aluminium spark in air after passing through 

 the lead vapour. The third is the same as the last except that it was 

 taken with a plate of the Schumann type. The fourth is the spectrum 

 of the lead spark in air and the fifth that of a carbon-lead arc in air. 

 From these photographs it will be seen that absorption is well marked 

 at A = 2833 A°U and at A = 2170 A°U. It should also be noted that the 

 wavelength A = 2203 -57 A°U was strongly enhanced in the spark 

 spectrum. 



