Nujol is an important material used in infrared spectroscopy. It is a heavy paraffin oil so it is chemically inert and has a relatively uncomplicated IR spectrum, with major peaks between 2950-2800, 1465-1450, and 1380-1370 cm^-1.

To obtain an IR spectrum of a solid, a sample is combined with nujol to make a mull (a very thick suspension), and is usually sandwiched between potassium- or sodium chloride plates before being placed in the spectrometer. For very reactive samples, the layer of nujol can provide a protective coating, preventing sample decomposition during acquisition of the IR spectrum.