2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



Because of some uncertainty as to the exact intensity values, how- 

 ever, the form of the curve introduces some uncertainty in the 

 determination of the separation of the maxima. In view of this, and 

 of the inadequate resolution of Burmeister's apparatus. Barker's cal- 

 culation of 13.2x10"*° g. cm.- for the moment of inertia, based on 

 the separation of 58 cm."^, is perhaps in as good agreement as could 

 be expected with the corrected value of Burmeister. As the band 

 occurring at 4.71a is certainly composite, no great significance can be 

 attached to calculations of moments of inertia involving data on this 

 band. 



Recently, R. M. Badger and J. L. Binder' have carried out a 

 photographic investigation of the absorption spectrum in the near 

 infra-red of hydrogen cyanide vapor in a 280 cm. absorption cell. 

 They have observed two bands in this region occurring at A7912 

 and A8563, respectively. In these bands they have been able to resolve 

 the fine structure attributed to rotation in the molecules. On the 

 basis of their measurements, they interpret each of the bands as com- 

 posed of a F and R branch. From this rotational structure they are 

 able to compute an accurate moment of inertia of 18.79 X io~^° g- cm.- 

 This calculation is in a reasonable agreement with the values based on 

 doublet separation for the 14,0. and /jx bands. The absence of a Q 

 branch is in harmony with the observations of a clearly doublet 

 character of both the latter bands. In regard to the apparent central 

 maxima in the bands occurring at 4.7/* and 3.6yu, the question naturally 

 arises as to the possible presence of a Q branch. It should be borne 

 in mind, however, that these may readily be explained as due to 

 overlapping. 



Assuming three fundamental frequencies corresponding to the 

 bands at I4ju,, 4.7,0., and 3.04/A, which have been designated respec- 

 tively as 8, vo and vi, Badger and Binder have interpreted the near 

 infra-red bands as 3V1-I-V2 for the band at A8563 and as 4i'i for the 

 band at A7912. Because of the absence of a Q branch, they have 

 assumed a linear arrangement of atoms, and on the basis of three 

 fundamental frequencies, offered an interpretation of the three funda- 

 mental modes of vibration corresponding to these fundamental fre- 

 quencies. From an analysis of probable atomic distances of separation, 

 they have come to the conclusion that the molecule must be hydrogen 

 cyanide rather than hydrogen isonitrile (HNC). 



' Phys. Rev., vol. 37, p. 800, 1931. 



