Abstract

In connection with an attempt to develop a method of quantitative spectrographic analysis of oil-field waters a detailed investigation has been made of the determination of strontium in the presence of alkali and other alkaline earth salts. The dried salts, together with a powdered graphite buffer and titanium as internal standard, were placed in cupped water-cooled graphite electrodes of a high voltage a.c. arc regulated by a variable inductance in the primary circuit. The spectrum was photographed with a Hilger E 1 quartz spectrograph, and the intensities of Sr 3380.7A, Ti 3383.8A, and Ti 3387.8A were determined by a means of a step sector and a Dietert densitometer. With constant amounts of SrCl₂ and TiO₂ and various amounts of NaCl, KCl, CaCl₂, BaCl₂, or MgCl₂, exposures were made at different times after the arc was started, and the intensities were determined. In all cases the intensity ratios between strontium and titanium lines were most constant during the period from 2 to 10 minutes after the arc was started. Hence, the weighted averages of the intensity ratios observed during this period have been studied as functions of the amount and composition of the extraneous salts. With NaCl added, the intensity ratio Sr 3380.7/ Ti 3383.8 has a maximum value twice as great as when no extraneous element is present, with MgCl₂ sixteen times as great. When an alkaline earth is added, the concentration of the extraneous substance giving the maximum value of the Sr/Ti intensity ratio decreases with atomic weight. Alkalis show the opposite behavior. When the total concentration of CaCl₂+NaCl is kept constant a maximum of Sr 3380.7/Ti 3383.8 is found for a certain ratio of CaCl₂ to NaCl. On the other hand, when various mixtures of KCl and NaCl are added a minimum value of this intensity ratio is obtained for a certain ratio of KCl to NaCl. In neither case are the effects of the extraneous substances additive.

© 1947 Optical Society of America

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