In certain fields, samples submitted to the spectrographer for analysis contain critical impurities and components which are present in such small concentrations as to require a source with a sensitivity comparable to the direct current arc. These impurities or components are usually
so pertinent to the final product that a precision of les than ± 10% cannot be tolerated. In an effort to develop a source which would have great sensitivity and yet good reproducibility. Duffendack and Thompson (1) in 1936 described the use of high voltage alternating current as the
power for the arc. Subsequent investigators have applied this type of source to the analysis of caustic liquors, agricultural and biological materials, metallurgical, fluorescent, geochemical, and ceramic samples with considerable success.