Il8 INFRA-RED ABSORPTION SPECTRA. 



and anomalous dispersion. The most conspicuous regions where these 

 ions manifest themselves is at 3.43 and 6.86 /x for CHg compounds, at 

 3.25, 6.25 and 6.75 fi. for benzenes, and at 4.78 fi for mustard oils. The 

 latter is superposed upon the CHg or the benzene vibration depending 

 upon the compound. Alcohols and compounds having NH2 have a 

 band at 2.95 fi. 



To assign the cause of these bands to a particular group of chemical 

 atoms rather than to a less definite, ultra-atomic source does not eluci- 

 date matters very much, although it is true that these bands do not 

 appear until these groups of atoms are introduced into the compound. 



