Abstract
A spectrographic method has been developed for determination of zinc in biological ashes by use of line width as a concentration index. Synthetic standards and analytical samples, in the form of sulfates, are mixed with a potassium sulfate-graphite buffer containing barium and cadmium as internal Controls. Samples are excited in a direct-current arc and spectra recorded with a Littrow quartz spectrograph. The contour of Zn 2138A is recorded with a recording microphotometer and the width determined at the maximum density of the control lines Ba 2255A or Cd 2288A. A plot of the logarithm of this width versus logarithm of zinc concentration prepared from standard samples containing 0.004 to 10 percent zinc serves as an analytical curve. Results determined by ordinary density measurements have been compared with those from width measurements. Although the two methods show comparable reproducibility of repeated exposures at the lower limit of the analysis range, the width method is more precise at higher ranges and has proven applicable even at concentrations where the line density method is limited by self-reversal and low photographic plate contrast. Concentrations as high as 10 percent have been determined, indicating possible application of such a method to the estimation of major constituents in such biological ashes or inorganic powders.
© 1948 Optical Society of America
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