Instrumentation and Techniques

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Abstract
It is proposed in this chapter not to list all the available instruments, techniques and procedures used in infrared spectrometry, but to outline, in the light of experience at the Macaulay Institute for Soil Research, what are considered to be the basic instrumental and sample requirements for obtaining meaningful infrared absorption spectra of minerals, and to indicate the type of ancillary equipment which has been found to be most useful in achieving this end. A good extended treatment of the general field of infrared instruments and methods is given in the book edited by Miller and Stace (1972). Commercial infrared spectrometers first became readily available in the mid 1940s and have proliferated greatly since then. The handbook by White (1964), although out of date, contains a good introduction to commercial spectrometers and their capabilities. A more recent listing appears in the book by Stewart (I 970). Choice of instrument will always be governed by funds available and specific needs, but in order to obtain good spectra with adequate resolution over a wavelength range capable of giving the best opportunity of characterizing the mineral, the spectrometer should meet certain minimum requirements. These are, that resolution, particularly in the 4000-2000 cm-1 region, should be better than 2 cm-1 and requirements employ diffraction gratings as the dispersing elements, and if the coverage is to 200 cm-1", will have facilities for purging the radiation path of water vapour which absorbs strongly below 300 cm", For critical work in the range 650-680 cm-1