no 



INFRA-RED EMISSION SPECTRA. 



of 3.5 watts, the maximum of the envelope of these emission bands lies at 

 4 to 5 //, and shifts steadily to the short wave-lengths, being at about 1.8 fi 

 for an energy consumption of 14.5 watts. The pure oxide is not an efficient 

 radiator of white light, and only becomes so when a small amount of cerium 

 or thorium oxide is added, which combination is the Nernst glower already 



2 3^-5 



Fig. 78. Zirconium oxide. 



mentioned. Aside from the sharp emission lines at 2.8 and 4.35 fi there 

 are wide hazy bands at 2 and 2.4 /x (appears on 7.5 watts), while from 

 5 to 6 n there is a wide band which is evidently unresolved, the maximum 

 shifting toward the short wave-lengths with rise in temperature. The 

 extraordinary rapidity which characterizes the growth of the emissivity at 



