INVESTIGATION WITH A ROCK-SALT PRISM. 85 



Dimethyl Aniline. C6HbN(CH3)2. (Figs. 92 and 93.) 



H As in the preceding compound, the 2.98 /x and 



yp^-^Pjj 3.25 //, bands are almost obliterated by the CH3 band 



11 I CH3 ^t 3.43 /i. A new band is found at 10.58 fi, while 



^^^<i*^^^^CH3 the strong 13.35 /a ^^id 14 5. /a bands are in common 



H with methyl aniline. As a whole the introduction 



of CHg-groups has made the derivatives more transparent than aniline. 

 No real shifting of the maxima can be observed in the maxima. 



p-Nitrosodimethylaniline. C«H4(N0)N(CH8)2. (Fig. 94.) 



H This is a solid which is light-green by transmitted 



UQ^ ^c-No light and blue by reflected light. The film was con- 



II ) (-.jj tinuous, but somewhat striated, due to crystalliza- 



\ <*** ^^CH3 tion, which made it unusually opaque. The bands 



H at 3.43 M, 6.86 /i, 7.3/*, 9.3 /x, and at 13.74/* remind 



us of the petroleum distillates, which have maxima in common with this 



compound. The 3.43 fi, 6.86 fx, and 13.74 /* bands are harmonic. 



Xylidine. C6H3(CH3)2NH2. (Fig. 95.) 



Xylidine is an excellent compound to study the effect of the presence 

 of NH2 and CHg at the same time. A similar example was noticed in 

 phenyl mustard oil, where the characteristic vibration of the mustard 

 oils at 4.78 fi is superposed upon that of the benzene nucleus at 3.25 /x 

 (6.25 fi) and 6.75 fi. The 6.1 /x band is to be found in compounds con- 

 taining NHo. 



The large spectrometer resolves the 3 /x band into two maxima, which 

 are at 2.96 /x and 3.42 fj,. It will be noticed that for the smaller disper- 

 sion the 2.95 fi band is not fully resolved. Here the NHj and CH3 

 groups are sufficiently strong to obliterate the benzene band at 3.25 /x, 

 and we have the 2.96 /x and the 3.43 /x bands brought out in their full 

 strength, just as in ammonia and in the petroleum distillates. Several 

 maxima, like those at 8.6 /x and 11.5 /x, are in common with the simpler 

 methyl anilines. As in most of the compounds studied, the region from 

 4 /x to 6 /x is lacking in strong absorption bands. 



This compound had decomposed and was distilled at 214° to 217° 

 just before using. Ordinary xylidine contains five of the six isomeric 

 modifications in which this compound can exist. Their boiling points 

 lie between 212° and 226°. 



Considering this compound with several others containing NHj or 

 NCS, it appears as though certain groups of elements had definite 

 absorption bands which are obliterated by stronger bands, as, for exam- 

 ple, in thiophene and pyrrol, at 2.95 /x and 3.2 /x. This point must be 



