Polyatomic ions exhibit characteristic infrared spectra. Although such spectra are potentially useful, there is very little reference to them in the recent literature. In particular, the literature contains no extensive collection of infrared spectra of pure inorganic salts obtained with a modern spectrometer. In order to investigate the possible utility of such data, the infrared spectra of 159 pure inorganic compounds (principally salts of polyatomic ions) have been obtained and are presented here in both graphical and tabular form. A table of characteristic frequencies for 33 polyatomic ions is given. These characteristic frequencies are shown to be useful in the qualitative analysis of inorganic unknowns. Still more fruitful is a combination of emission analysis, infrared examination, and x-ray diffraction, in that order. Several actual examples are given. It is evident that a number of problems involving inorganic salts containing polyatomic ions will benefit by infrared study. The chief limitation at present is the practical necessity of working with powders, which makes it difficult to put the spectra on a quantitative basis.