104 



INFRA-RED ABSORPTION SPECTRA. 



present work on aniline we have the original benzene band, at 3.25 /x, 

 and a second at 2.97/1. As already mentioned, it has not yet been 

 shown that the selective absorption of a solid in solution and the intra- 

 molecular absorption of the solvent are closely related, but the question 

 can be better settled by a photometric study as just indicated. (See, 

 further. Appendix IV.) 



There are other bands farther out in the infra-red, which shift back 

 and forth, just as noted above, but here the original benzene bands are 

 more numerous. The most noticeable ones are those of the methyl 

 sulphocyanate at 7.06)11 and 7.61 /i, which occur at 6.91 /i and 7.27/1 in 

 ethyl sulphocyanate. However, in all the benzene derivatives studied 

 the occurrence of an apparently new band in the derivative does not 

 always seem to be a new band, but simply that the derivative has brought 

 about a condition within the molecule such that the original resonating 

 ion has a greater freedom. 



In the gases there is a more definite shifting of the absorption band 

 lying between 3 and 3.5 /i, as shown in the following table. 



In the region at 6.8 /t to 7.0 /i there is a similar shifting, but there is 

 less regularity in the positions of the bands. Angstrom (loc. cit.) has 

 shown that the location of the CO2 band at 4.28 /t and the CO band at 

 4.59 /I invalidates the assumption that the position of an absorption band 

 depends upon molecular weight. Ransohoflf's (loc. cit.) work on the 

 alcohols shows that for the alcohols there is no shifting with increase 

 in molecular weight. 



Within the experimental errors of observation Puccianti's (loc. cit.) 

 work for the region of 1.71 m shows no shifting of the maximum of an 

 absorption band. 



In all my work on the different compounds like methyl and ethyl 

 iodide, nitrate, cyanide, aniline, etc., no shifting can be detected. To 

 make this test conclusive for the marked band at 3.43 /i this region was 

 repeated for both compounds (methyl and ethyl) before setting the 

 spectrometer for another part of the spectrum. In this manner a slight 



