112 



INFRA-RED EMISSION SPECTRA. 



especially the emission bands, are to be observed in the radiation curves 

 of the glower, given in fig. 57. In curve b, fig. 80, is shown the emission 

 spectrum of a commercial "heater-tube." The covering is some refractory 

 substance, perhaps containing aluminum oxide and a silicate binder. 

 There is a sharp band at 2.85 p. and hazy bands at 4.7, 5.3, and 6.3 ;i. 



2 3 4 s 



Fig. 79. Zirconium oxide. 



7JU 



Uranium Oxide (U 2 3 ); Cerium Oxide (Ce0 2 ); Thorium Oxide (Th0 2 ). 

 (Curve a = U 2 3 ; &=Th0 2 ; c = Ce0 2 ; fig. 81.) 



The uranium oxide is a greenish-brown powder which gives a smooth 

 continuous spectrum with hazy maxima at 2.8 and 3.4 ft, respectively. 



The thorium oxide, curve b, shows no marked emission bands, and the 

 whole spectrum is suppressed to 7 /*. Beyond this point the emissivity is 



