Efficiency of Sample Transport from the Electrode Cavity to the Excitation Zone of Gas-Stabilized dc Arcs for Spectrochemical Analysis

Abstract

The transfer of atomized material from the electrode cavity to the discharge region of a dc arc is quantitatively defined in terms of the efficiency with which elements enter the excitation region. Equations inherent in the determination of efficiencies from spectral-line intensities are given. Relative efficiencies were experimentally determined for a synthetic silicate sample containing some 20 test elements as trace or minor constituents. The elements were selected according to volatility and carbide forming properties. The influences of the following variables on the efficiency were investigated: (a) type of element, (b) preliminary fusion of test sample with lithium metaborate, (c) dilution of test sample with lithium carbonate or lithium fluoride, (d) two different types of Stallwood-jet devices for arc stabilization and control of atmosphere, (e) the composition of the stabilizing gas, viz., the oxygen content of an oxygen—argon gas mixture, and (f) the flow rate of the stabilizing gas.