n8 



INFRA-RED EMISSION SPECTRA. 



tube. The two spectra are similar, with a sharp emission band at 2.85 [i. 

 Other maxima appear at 2, 3.2, 4.1, 5, and 7.5 li. The general outline of 

 the spectrum is similar to that of yttrium. 



Neodymium Oxide (NdO); Manganous Oxide (MnO). 

 (Curve a, NdO; curve b, MnO; fig. 86.) 



The neodymium oxide was deposited in a thick layer upon a strip of 

 platinum, by evaporation from a solution of the nitrate. The radiation 

 curve shows maxima at 3, 4.4, and 4.83 ll. Beyond 6 ll the emissivity is 

 strong and not unlike that of cerium and thorium. The scale of emissivity 

 is one-half of the curve for MnO. 



/ 2 3 4 5 6 



Fig. 86. Neodymium oxide (a); Manganous oxide. 



8/1 



The manganous oxide was a grayish-brown color. The thickness of 

 the layer upon the "heater-tube" was about 1.2 mm. The radiating 

 surface was a dull red. The spectral radiation curve is uniformly smooth 

 throughout its whole length, with but a slight depression at 3.2 11 to be 

 noticed in numerous oxides. In these two curves the sensibility of the 

 instrument is different, as is frequently the case. 



Zinc Oxide (ZnO); Lead Oxide (PbO). 

 (Curve a, ZnO; curve b and c, litharge (PbO), curves e and/, platinum; fig. 87.) 



The zinc oxide became a yellowish-green on heating, resuming its 

 former white color on cooling. In spite of this selective emission in the 

 visible spectrum, the distribution of energy in the infra-red is uniform, 

 with the usual depression at 3.2 ti. Lead oxide ("litharge") melts at a low 

 temperature. On heating the color changes from orange to deep red. 

 Curve b, fig. 87, shows the distribution of energy for the oxide after it had 

 melted into a smooth mass and solidified. Curve c shows the emissivity 



