Abstract
High voltage a. c. arc source, which is secondarily shunted by large capacitor, is used as a excitation source.
Powdered sample is deposited on_a massive copper bar moistened with collodion (diluted with Amyl-acetate), dried at 110°C, and installed as the lower electrode with a cone-shaped upper electrode. As the discharge proceeds to burn, the lower electrode is moved towards the direction perpendicular to the optical axis of the Zeiss Qu-24 spectrograph, exposing fresh sample surfaces for discharge.
Spectral lines are clearly seen under these conditions down to 0.01% for sulfur, selenium, chlorine, bromine, and iodine, but such a high sensitivity can not be obtained for fluorine.
