60 INFRA-RED ABSORPTION SPECTRA. 



NiTROETHANE. C2H5NO2. (Fig. 33.) 



The 3.4 )u, band is still undisturbed. In the region from 6 fx. to 7.5 fi 

 the addition of a CHa-group seems to have brought about a greater 

 freedom of vibration, and, instead of a continuous band, we find several 

 small sharp lines. The same is true of the 7.9 /x and 10 /x bands, which 

 are also more prominent. There are two new bands located at 11.45 /a 

 and 12.45 P-> as well as the 14 /x, band, which is of frequent occurrence 

 in methyl and ethyl compounds. On viewing these curves with their 

 profusion of absorption bands, one can see why nitrogen compounds 

 are so opaque as compared with the sulphides. The thickness of the 

 cell used was only o.oi mm., while in ethyl sulphide the thickness was 

 ten times as great. In these two compounds the N atom is thought to 

 be trivalent. The spectra are entirely different from nitrobenzene. 



Methyl Cyanide. CH3CN. (Fig. 34.) 



In the pyridine group mention was made of the great opacity of nitro- 

 gen compounds. In those cases the N or NH replaced a CH-group in 

 the ring compounds. In the present compound the N atom is joined to 

 the C atom. The result is a more transparent compound like C2H5CN. 



The 3.4 fj. band appears complex, while a small depression appears at 

 3.0 /x. The 4.37 fi band occurs prominently here, as it does in a few of 

 the succeeding compounds. No band occurs at 5.7 /x, but a small one 

 is found at 6.2 /x, ending in a large band at 7.0 /x. The 8.2 /x band of 

 CH3I is wanting, while the 10.5 /x and 14 /x bands, to be noticed fre- 

 quently in other compounds, are very weak. As a whole, an entirely 

 new series of lines has been produced, most of which are very sharp. 

 The 7.08 /x band is to be noticed in connection with the ethyl cyanide. 

 The band at 3.0 ja is to be found in many compounds containing N 

 atoms. The curves are practically identical for the museum and Kahl- 

 baum's samples. 



Ethyi, Cyanide. H2C5CN. (Fig. 35) 



The difference between methyl and ethyl cyanide is as marked as that 

 of the respective iodides. This is especially true at 11 /x, where the 

 large band of CH3CN is entirely wanting. The 9.6 /x band of CH3CN 

 is found at 9.35 m. The transparent region extending from 11.5/x to 

 13.5 fi in CH3CN is shifted so as to extend from 10.5 /x to 12.5 /x in 

 C2H5CN. The 3.4 fi band occurs in its proper place, while the y.y /x 

 band is probably a new one. The unusually sharp bands at 6.98 /x, 

 9.3 IX, and 12.75 M are very marked, and they make it appear that oxygen 

 is not the only element that sharpens the bands. The 6.98 /x band of 

 C2H5CN is not the same as the 7.04 ai of the CH3CN. To make sure 



