The infrared spectra from 300-880 cm-1 of 208 inorganic substances are reported. Nearly all are salts containing polyatomic ions. Spectral curves are presented for 140 of the compounds, and a list of characteristic frequencies is given for twenty ions. Among other matters discussed are: (a) the non-reproducibility of some of the spectra, and reasons for this, (b) absorption due to the torsional oscillation of water molecules, and (c) some vibrational assignments for MnO4(-) and CrO4(2-).