INVESTIGATION WITH A ROCK-SALT PRISM. 6^ 



more transparent. Ransohoff/ using a larger dispersion, found the 

 region a complex of two bands, at 3.0 /x and 3.43 /*, while the band at 

 5.2 /x is deeper and better defined. 



EXHYLHYDROSUtPHIDE. C2H5SH. (Fig. 39.) 



The low boiling-point, 36°, of this ill-smelling compound makes it a 

 difficult subject for investigation, as will be noticed from the curves in 

 fig- 39. which were obtained after giving the cell an additional coating 

 of paraffin to prevent leaking. In depth and number of transmission 

 minima the curve agrees exactly wdth that of Julius, and was used to 

 reduce his values (given for his straight-line extrapolation from 5 fi) 

 back to the true dispersion curve. The last band found by Julius was 

 the one at 10.4 fi. No attempt was made to locate accurately the band 

 found by him at 3.88 /i. 



The curve is quite simple. The deep double band at 7.0 fi and 8.0 fx 

 is strikingly repeated in ethyl sulphide. The 5.9 /a band is not promi- 

 nent, while the ones found in sulphur at 7.9 /t and 12 fi are replaced by 

 a strong minimum a.t S fi and another at 11.6 fi. As a whole this com- 

 pound is quite transparent. 



Ethyl Sulphide. (C2H5)2S. (Fig. 40.) 



As compared with ethylhydrosulphide this compound is very similar 

 in general absorption, as well as in the location of absorption bands. 

 The band at 6.86 /x is worth noticing, since it occurs in so many other 

 compounds. The addition of a CaHg-group for an H atom has not seri- 

 ousty disturbed the spectrum of the hydrosulphide. The latter repre- 

 sents some of the earliest work, using a wider slit, and the evidently 

 complex band at 7.3 fi is resolved in the present compound. In com- 

 parison wath these sulphides it wall be noticed that the allyl is far more 

 opaque. 



TriethylaminE. (CsHOsN. (Fig. 41.) 



In this compound we have an additional ethyl group, while the S has 

 been replaced by an N atom. The result is an increase in the com- 

 plexity of the region from 7 to 10 fi, thus making the compound more 

 opaque as a whole. The greater transparency at 11 to 13 /x is quite a 

 contrast to ethyl alcohol. There is not so marked an effect of the 

 N atom at 3 /x as in the case of aniline and several other benzene deriva- 

 tives. This compound has a strong ammonia odor, and is similar to it, 

 yet with the large spectrometer no marked band of ammonia could be 

 detected at 3 /x; in fact the curve has no resemblance to that of ammonia. 



^Ransohoff, loc. cit. 



