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.

Remember that water has strong, broad bands at about 3750 cm-1 and 1610 cm-1.