The measurement of the infrared spectra is carried out under the supervision of a Junior Demonstrator on a Perkin-Elmer 1710 Fourier Transfer spectrometer situated in the Upper Teaching Laboratory.
The spectra are determined as 'mulls' (i.e. suspensions) in Nujol, which is a heavy paraffin oil, pressed between rock salt plates. There are copies of other spectra displayed, which you will need for comparison purposes.
The crystals are moderately air stable and a mull can be prepared by grinding a few crystals in an agate motar with one or two drops of Nujol (liquid paraffin) to form a fairly thick paste. The paste is then transferred with a spatula to predried sodium chloride plates, in sufficient quantity (ca. 50 mg) to provide a percentage transmission at 4000 cm-1 of 60-70%.
Handle the NaCl plates with care: they are brittle and their surfaces must remain perfectly optically flat. These surfaces are easily damaged by moisture or perspiration on fingers.