Electrodes for Trace Impurity Analysis and Determination of Traces in Gallium

Abstract

Electrodes of several graphite makers have been evaluated and compared for weight consistency and impurities for the purpose of developing techniques to determine trace impurities in material which can take advantage of preferential volatilization. A technique suitable for pre-arcing graphite electrodes in an argon atmosphere has been developed for minimizing the impurity background in the electrode cup so that ultra-trace determination is possible. The purified and selected electrodes are used in development of a spectrochemical method for determining trace impurities in gallium metal. The technique takes advantage of strong preferential volatilization of the metals in a dc arc with sequential exposures used for improvement of signal-to-noise ratio. A new sampling technique and standardization method are discussed. Special problems related to the analysis of gallium are investigated, and analytical results are shown.