Potassium bromide is widely used as a matrix material in infrared spectroscopy (1). In fact, the KBr pressed pellet technique has almost completely supplanted the mineral oil-mull technique in some laboratories. The KBr method has several inherent advantages such as absence of interfering absorption bands, reproducible concentrations, and use of small 1-2 mg. samples. However, as with any method of sample preparation, the KBr technique has limitations and difficulties. For instance, unusual or misleading effects have been noted in this technique due to grinding (2), pressing (3), and interactions between the solid sample and matrix (4,5). The difficulty of preparing a homogeneous sample seems to have been solved by the use of the mechanical vibrator (6,7).
Neil T. McDevitt and William L. Baun, "Contamination of KBr Pellets by Plastic Mixing Vials," Appl. Spectrosc. 14, 135-136 (1960)