52 INFRA-RED ABSORPTION SPECTRA. 



3.1 /t and 4.65 n, but the absence of bands in the holographs at 3.1 /* 

 would seem to indicate that the broad Y band is not the composite of 

 the CO2 and O bands. 



As mentioned by Rubens and Aschkinass (loc. cit.), the absence of 

 CO2 bands in the curves shows that this gas can not have a great influ- 

 ence upon the general transparency of the earth's atmosphere. 



SuivPHUR Dioxide. 'SO2. 

 (Cell 6.3 cm. ; barom., 74.4 cm. ; temp., 23° ; fig. 23.) 



Generated by adding concentrated H2SO4 to sodium bisulphide 

 (NaHSOs) and drying in P^O^. 



This same gas was fractionally liquefied, and then fractionally dis- 

 tilled, but, as will be noticed, the curves coincide for the two samples, 

 showing that nothing has been eliminated. This is a striking contrast 

 to ethane, in which for successive purifications certain bands continued 

 decreasing in intensity, showing that they were due to impurities. 



Compared with CO2 we have few examples which are more conspicu- 

 ous in showing marked changes by substituting an S for a C atom. 



In the region where CO2 is transparent the SO2 has its greatest 

 absorption bands. The one at 10.4 fi coincides with that of ammonia. 



Certain lines seem to belong to a spectral series, as determined by the 

 law of " constant difference " of the wave-numbers. For example, take 

 the following absorption maxima : 



3-8>ro=6o5 i.to> ^0=610 



Considering that the 8.7 fx. band is broad, and hence not well defined, 

 the agreement is very close, but, unless we find more lines toward the 

 visible spectrum, we can not determine the constants in the spectral 

 series equations. 



The two curves given in fig. 23 are for ordinary SO2 and for the same 

 gas when purified by fractional liquefaction and distillation. 



Hydrogen Sulphide. US. 

 (Cell, 5.7 cm. ; barom., 74.0 cm. ; temp., 21° ; fig. 24.) 



Generated by adding HCl to ZnS, dried in PoOg. 



Oquefied in two fractions, one at — 15°, the other at — 60°. The 

 sample liquefied at — 60° was distilled fractionally, and several fractions 

 were examined, A sample which had been made from ZnS + HoSO^, 

 but not liquefied, showed SO2 bands, which would naturally be expected. 



The changes wrought in the absorption spectrum by substituting 

 hydrogen for oxygen are not so marked as that from CO2 to SO2. For 

 HgS we have a greater number of lines, especially beyond 9 /*, but there 

 are no deep bands like in SO2. It was noticed that the bands were not 



