The use of argon as an environment for the dc arc results in marked prolongation of volatilization, increased initial electrode currents, and enhancement of lines of many elements, particularly volatile ones, when samples are burnt to extinction and compared to helium and argon-helium mixtures. An interdependent relationship between total time necessary for complete volatilization of samples, percentage helium and argon composition of the atmosphere, and sample concentrations is demonstrated. Independently, a relationship between the electrode current, percent helium and argon, and concentration of the sample exists.
BERT L. VALLEE and S. JAMES ADELSTEIN, "The Effects of Argon and Argon-Helium Mixtures on the Direct Current Arc," J. Opt. Soc. Am. 42, 295-295 (1952)