INFLUENCES OF PHYSICAL AND CHEMICAL PROCESSES IN ELECTRODE CAVITY AND GASEOUS ATMOSPHERE IN ARC ON EMISSION CHARACTERISTICS OF DC ARC FOR SPECTROCHEMICAL ANALYSIS .1. EFFICIENCY OF PARTICLE TRANSPORT FROM ELECTRODE CAVITY TO EXCITATION ZONE

The transfer of atomized material from the electrode cavity to the discharge region of a d.c. 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 twenty 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: (i) type of element; (ii) preliminary fusion of test sample with lithium metaborate; (iii) dilution of test sample with lithium carbonate or lithium fluoride; (iv) two different types of Stallwood-jet device for arc stabilization and control of atmosphere; (v) the composition of the stabilizing gas, viz. the oxygen content of an oxygen-argon gas mixture; (vi) the flow rate of the stabilizing gas. A detailed discussion of the experimental technique includes a description of a new Stallwood-jet device with two independently controlled gas flows permitting both adequate stabilization of the arc and suppression of molecular bands without requiring a chamber. © 1969.