Selection of Spectral Lines

If very low concentrations of trace constituents are to be determined, it is necessary to select a sensitive line of the element for analytical purposes. If somewhat higher concentrations are to be determined, more spectral lines are available from which to make the choice. Spectral line wavelength and intensity tables should be consulted in order to make the selection. These sources are listed in Chapter 7. Appendixes II and III also give information on some spectral line wavelengths and intensities. 

FIGURE 8-5. Spectrographic plate of comparison standards and samples of wheat grain. 

Metal alloy comparison standards can be made by mixing pure metals or metal alloys of known composition by heating in an induction furnace. The standards can then be formed into solid rods to serve as self-electrodes or flat disks if the point-to-plane technique is to be used. The National Bureau of Standards has available a number of metallurgical standards of certified composition. 

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