1560-1500 cm.-' and 1350-1300 cm.-l as the frequencies of the C-NO, valence vibrations in aromatic compounds, and comments that absorption bands in the low-frequency region are to be expected from skeletal vibrations and from deformation modes involving the R-NO, group. In an examination of fifty-six nitro-aromatic compounds, he found a band in the 760-700 cm.-l region which was usually absent from comparable substituted aromatics lacking the nitro-group, hut thc intensity of the band varied unaccountably so that any correlation was of limited value.
The symmetrical and asymmetrical NO, stretching frequencies in the nitro-furans examined fell in the ranges 1360-1340 cm.-l and 1535-1505 cm.-l respectively. In all the nitrofurans examined, a strong band or doublet was found in the region 830-805 cm.-', but since a band was also found in some of the furans lacking a nitro-group, no analytical significance is attached thereto at present, although this is still under investigation.
In addition to the compounds listed in this paper, other 5-nitrofurans have been examined, e.g. Furadroxyl, Furadantin, Furazolidone, Furamazone [Reg. Trade Marks] of the general structure O,NC,H,O.CH=X prepared by condensing 5-nitro-2-furaldehyde with substituted hydrazines, semicarbazides, and oxazolidones and similar ring systems. The absorption peaks listed in the paper as identifying characteristics of this class of compound were found to apply in all cases.