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The error in spectrographic analysis is often larger than can be tolerated in the determination of the major constituents of a sample. Some causes of error in spectroscopic sources are considered, and possible methods for improvement of the precision of spectrographic analysis are discussed. Flames are among the most precise sources, but many substances affect the emission of light by elements in the flame. High-temperature flames may reduce the effect of some of these interferences in addition to providing better sensitivity, but adequate data on their properties are not yet available. Errors in arc and spark sources arise from instability of the discharge and variable sampling. Some newer types of arcs provide stable, high-temperature conditions and controlled atmospheres. To adapt these discharges for use as high-precision spectroscopic sources, it will be necessary to devise methods for the controlled introduction of samples. This has been attempted so far only with the plasma jet.
Chemist, National Bureau of Standards, Washington, D. C.