When a mixture of cations in solution is precipitated by the addition of carbonate, the resulting mixed carbonate precipitate, when subjected to infrared examination, does not usually exhibit the individually characteristic absorption bands due to each of the carbonates constituting the mixture. Instead, various interesting anomalies such as blending of bands, shifting of positions, and changing of intensities are observed. Such anomalous behavior may hamper any qualitative or quantitative measurements on such samples. Representative spectra and possible explanations for some of these anomalies are presented.
Gene E. Kalbus, Eugene A. Berg, and Lee H. Kalbus, "Anomalies in the Infrared Spectra of Mixed Carbonate Precipitates," Appl. Spectrosc. 22, 497-501 (1968)