A quantitative analysis of salts of the Dead Sea for their rubidium contents was carried out. It was found necessary to use the resonance lines of Rb (at 7800; 7948A) as analysis lines. To eliminate the effect of extraneous elements on the ratio of intensities of the Rb line and the internal standard line, the method of quantitative addition was chosen. This method could not be used without correction for the strong selfabsorption of the Rb resonance lines. Taking into account this self-absorption, a corrected formula was deduced, and with this correction the analyses were carried out with good results for concentrations of rubidium chloride from 0.005 percent to 0.1 percent.
A. HALPERIN and S. SAMBURSKY, "The Use of Self-Absorbing Spectral Lines in Quantitative Determination of Rubidium," J. Opt. Soc. Am. 42, 475-480 (1952)