58 INFRA-RED ABSORPTION SPECTRA. 



Since, in all infra-red work, the calibration consists essentially in 

 setting for minimum deviation of some known line, like the D lines, in 

 the visible region, and using that for a base, or " zero setting," and 

 since a slight error in setting for minimum deviation or in the " zero 

 setting " may introduce great errors in the infra-red, it is unfortunate 

 that Konigsberger did not compare the 2.95 fx water of crystallization 

 band with that of pure water, found by Paschen at from 2.916 /x to 

 3.024 /A and by Aschkinass at 3.06 jx. The same is true of Ransohofif,^ 

 who considers the alcohol band at 3.0 /a in coincidence with the 3 /a band 

 of water, as found by Aschkinass, though he made no direct comparison. 

 In the present work, using the large spectrometer, the best value for the 

 water band is 2.95 /n, which agrees with the value found for water of 

 crystallization. (See Appendices V and VI.) 



Alcohols. (Figs. 32 and 38.) 



In the present work alcohols were but briefly studied, because of their 

 great opacity beyond 7 /a, as well as on account of the difficulty of free- 

 ing them from water. The higher alcohols, like glycerin, even if they 

 could be freed from water, are so hygroscopic that they are difficult to 

 investigate. 



Myricyl Alcohol. CmHcoOH. (Fig. 32.) 



Ethyl alcohol was studied with the small spectrometer, and has been 

 discussed with the other simple CHg compounds. Amyl alcohol was 

 examined at 3 )u, with the large spectrometer to compare with the work 

 of Ransohoflf.^ The maxima were found at 2.95 ju, and 3.43 //.. Ranso- 

 hoflf found these bands at 3.0 /x and 3.43 /a. 



The only other alcohol which has been studied thoroughly is myricyl, 

 which is a solid from beeswax. A very thin solid film was obtained 

 by melting between two plates of rock salt. The spectrum is very 

 marked for several strong absorption bands which correspond to those 

 in the petroleum distillates. The dispersion with the large spectro- 

 meter at 3 ju,, curve h, is comparable with that of fluorite, and hence 

 comparison can be made with the work of Ransohofif. In the present 

 work the maxima occur at 1.71 /a, 2.95 ^i, 3.43 ii, and 5.8 jx. The water 

 bands were found at 2.95 /x and 6.0 jm, so that the 2.95 /x band of myricyl 

 alcohol coincides with the one for water, while the one at 5.8 //. does not. 

 The discrepancy at 2.95 ix and 3 /* may be due to inaccuracies in the 

 dispersion of rock salt as compared with that of fluorite. The rock- 

 salt dispersion curve passes through a double curvature at this point, 



^Ransohoff, loc. cit. 



