9 o 



INFRA-RED EMISSION SPECTRA. 



fig. 58. The curve for 102 watts was irregular in outline and the values 



of a obtained at different wave-lengths 

 (indicated by crosses, circles, dots, 

 squares, etc.) undergo great variations. 

 On the whole, it is evident that it is 

 hardly permissible to obtain this con- 

 stant on the assumption that the ra- 

 diation law of the Nernst glower is 

 similar to that of platinum or of a 

 complete radiator. The energy curve 

 of a complete radiator having a maxi- 

 mum emission at 1.45 p. falls far be- 

 low the Nernst glower curve (a, fig. 

 58) at 5.5 n, which shows that the 

 emission at 1.45 /* is not as intense as 

 it should be if the emissivity were 

 similar to a complete radiator. For 

 the same reason, the spectral energy 

 curve of a complete radiator having 

 a maximum at 1.32 , lies far above 

 the glower curve (b, fig. 58) at 5.5 fx. 

 In fig. 60 is shown a series of 

 energy curves of an incandescent fila- 

 ment (3 cm. long) of osmium, when 

 on an energy consumption of curve 

 a=2.44 and curve 6=7.38 watts, re- 

 spectively. The corresponding tem- 

 peratures, observed with an optical pyrometer, using red absorption glass, 

 are 1607 and 2000 K. 66A C., respectively, while the computed tempera- 

 tures, on the assumption that the radiation constants are the same as for 

 platinum (for X =1.35 and 1.2 /*), are 1670 C. and 1907 C, respectively. 



Fig. 60. Radiation from osmium. 



c 1 



-4-J 



05 



c 

 o 

 u 



c 

 o 



2 -5 



-a 



DC 



12 3 4-56 7 8 Waits 



Fig. 61. Radiation constant (a) of osmium. 



These filaments were in glass bulbs similar to that of an incandescent 

 lamp, and had short side tubes with fluorite windows. Fig. 61 shows the 

 value of a of osmium (of fig. 60) for variation in energy consumption. 



