Abstract
FOUR main types of light source are used for the spectrographic analysis of metals and alloys. They are the low-voltage D.C. arc, the high-voltage A.C. arc, the condensed spark either controlled or uncontrolled, and the low-voltage discharge initiated by a low-energy, high-voltage spark. Since they require only simple and inexpensive equipment, the D.C. arc and the uncontrolled condensed spark are generally used in Britain, the arc for work of high sensitivity but not high accuracy because of its instability, the spark for accurate analysis. For the accuracy and wide field of application required by present-day analysis it is necessary to have available not only the arc and the condensed spark but also the wide range of excitation conditions intermediate between them. A. Walsh (Bull. Brit. Non-Ferrous Metals Res. Assoc, No. 201, 60, March 1946) has constructed such a source unit, which provides a simple condensed spark, a low-voltage D.C. arc, and, by using a triggered low-voltage discharge, a whole series of intermediate excitation conditions. The circuit, described fully in the paper, is similar in principle to that of Hasler and Dietert (J. Opt. Soc. Amer., 33, 218; 1944) but totally different in detail, particularly in regard to the method of triggering and the electrical constants of the discharge circuits. The results of some experiments performed with the new source unit on aluminium-base, zinc-base and lead-base alloys are given in tabular form. These indicate that a high degree of reproducibility is obtainable with the new type of source and that the accuracy is higher than is possible with, a simple condensed-spark unit.
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General Purpose Source-Unit for Spectrographic Analysis. Nature 158, 54–55 (1946). https://doi.org/10.1038/158054d0
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DOI: https://doi.org/10.1038/158054d0