[en] Infrared spectra of LiOH and Li₂CO₃ suspended on KBr discs were measured over the concentration range 20 μg/100 mg KBr to 600 μg/100 mg KBr. The absorbance of a selected infrared band of each sample was carefully determined. The empirical equation, which expresses a correlation between the absorbance and the concentration, was given for each lithium compound. The feasibility of independent and direct determination of the LiOH and Li₂CO₃ content in Li₂O was shown, and the spectroscopic technique was applied to a typical Li₂O sample. It was shown that the detection limit of the analysis was improved by low-temperature measurements of the infrared spectra. (orig.)