GASES IN VACUUM-TUBES. 



oV 



The result is shown in curve a of figure 148, which is of no small 

 significance, especially in the region of 4.75 jx, where no band is to be 

 found. The curve (dots and crosses at 4.75 ix) shows that the radiation 

 from the gas and from the hot cell is of equal intensity in this region. 

 The decrease in the intensity, thus forming an apparent maximum at 

 5.5 IX, is due to the fact that in moving the spectrometer arm the vacuum- 

 tube was not adjusted before the slit, hence the last two readings are 

 for the radiation from the side of the tube instead of its axis. 



In the final work the gases were not studied in the order given here, 

 the CO2 and CO coming last. The absence of the 4.75 fx band in N and 



^ ^ 



^ 



Fig. 148. 



NH3 excluded the possibility of its being due to nitrogen. Several 

 drops of water were introduced into the nitrogen, but no change could 

 be detected in the radiation at 4.75 ,u, showing that this band is not due 

 to water vapor. Hence it remained to be shown whether it is due to 

 CO2 or CO. In discussing these two gases it was shown that the radia- 

 tion from CO is much stronger than for COo at 4.75 [x. 



The presence of strong emission bands just beyond the red having 

 maxima at 0.66 jx, 0.75 ix, o.go fi and 1.06 fx was found only in nitrogen. 

 Helium (loc. cit.) is the only other gas known which has strong lines 

 (bands) in this region, and from the scanty data it appears as though 

 this property were confined to the inert gases. 



A study was then made of these emission bands under constant cur- 



