68 INFRA-RED REFLECTION SPECTRA. 



quartz glass there is a band in common at 8.4 fi, showing a common group 

 of atoms. This band, with the five groups in common with the silicates, 

 makes a total of six groups of bands, the radicals which cause them being, 

 as yet, undetermined. These bands are at 8.4, 8.8, 9.7, to, 10.5, and n /t. 

 This seems to substantiate the view expressed in Carnegie Publication 

 No. 65, p. 95, that in the silicates there appear to be several silicon-oxide 

 radicals, one or more of which are present in each mineral, or even in the 

 different specimens of the same mineral. 



In table III are given the characteristic maxima of the reflection and 

 absorption bands of radicals studied in this and in previous work. 



