The application of the vacuum-cup electrode to the spectrographs analysis of solutions of refractory-metal alloys is described. Both citric and oxalic acids in 5% sulfuric acid solution served as suitable completing agents. The absence of interelement effects is demonstrated. Alternate sets of excitation parameters and variation of sample weight and aliquot sizes permit application of the technique to a broad range of element concentrations. Typical coefficients of variation of results obtained by the method are between 3% and 4%.

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The most exasperating obstacles for determining traces of nitrogen in refractory metals and alloys are the inability to dissolve appropriate weights of solid pieces of metal and relatively high blanks. Potassium dichromate, in conjunction with phosphoric and hydrofluoric acids, was found to be an effective combination for the rapid dissolution of up to 5-gram pieces of various refractory metals. Potassium dichromate can be prepared by purification of potassium chromate from an alkaline medium sothat blanks generally are below 0.5 pg of nitrogen.

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