(1) Friedman, 9. M., Wong, S.,’VValton, J. H., J . A p p l . Phyaiol. 18, 950 (1963). (2) Katz, S. A., Rechnitz, G. A , , 2. Anal. Chem. 196, 248 (1963). (3) Mattock, G., Analyst 89, 350 (1964). (4) Moore, E. W., Wilson, D. W., J . Clin. Invest. 42, 293 (1963).
ACKNOWLEDGMENT
We gratefully acknowledge the technical assistance of F. Russodlesi with the Technicon equipment.
Chemical Bondin
(5) Portnoy, H. D., Gurdjian, E. S., Clin. Chim. Acta 12, 429 (1965). (6) Rechnitz, G. A,, Braurier, J., Talanta
LITERATURE CITED
the average percentage difference was 6.2% with a 95% confidence limit range of -0.19 to f0.82 meq./l.
11, 617 (1964).
(7) Rechnitz, G. A., Zamochnick, S. B., Ibzd..
D. 1061.
HAROLD JACOBSON Squibb Institute for Medical Research Ken- Brunswick, N. J.
ects on Sulfur L
SIR: Fischer and Baun ( I ) reported some remarkable chemical bonding effects on the sulfur L emission spectra. We have also measured sulfur L spectra using x-ray excitation and have observed some discrepancies. EXPERIMENTAL
The sulfur L x-ray lines were observed with the Norelco Vacuum X-ray unit equipped with the demountable Henke type x-ray tube. Procedures described by B. L. Henke (2) were followed with the exception that a copper anode was used in place of the carbon anode for the x-ray tube exciting the sample. Typical operating conditions of the x-ray tube were 100 ma. at 6 kv. For pure sulfur, peak count rates of 400 counts per second were typical. RESULTS
The spectra obtained by Fischer and Baun for Li2SOd and that obtained by us is shown in Figure 1. Our results are in general similar to the work of Fischer and Baun with two exceptions. In the case of Li2S04,ITa2S04,and KzS04we did not observe their peak a t approximately 84 A. This peak is typical of sulfides or elemental sulfur. It is possible that the direct electron excitation, which they used, reduced the sulfate to sulfides. This transformation is presumably less probable with the secondary x-ray excitation that we used. Further neither Fischer and Baun nor we observed a peak for BaS04 a t 84 A. This sulfate is apparently stable to electron bombardment. The second difference we wish to report is that we observed a peak for a nuniber of sulfates and sulfites a t approximately 89 A. Fischer and Baun do not extend their data to this region. This peak falls in the same region where the carbon K a line lies in second order. It is possible that our samples were contaminated with carbon or that the carbon in the lead stearate analyeing crystal was fluorescing and that radiation was Bragg reflected in second order. To eliminate these two possibilities we studied LizSOd and LizCOa. w e set 1954
e
ANALYTICAL CHEMISTRY
Electron Excitation (Fischer and Baun)
90
85
80
75
X. A
Figure 1 . Comparison of sulfur L emission spectra of LizS84 obtained by electron and x-ray excitation
the pulse height analyzer so that the second order carbon K a peak mas not visible from the L i 2 ~ 0sample, 3 cnder these operating condit,ions a peak a t 89 A. was seen for t,he Li2S04sample.
Henke, B. L., “Some Notes on Ultra Soft X-ray Fluorescence AnalYsis 10 to 100 A. Region,” Advances in X-Ray Analysis, 8, 269. W. E. l*Iueller, G. Mallett, ht. Fay, eds., Plenum Press,
(2)
1965.
LlTERATURE CITED
Fischer, D. W.,Baun, W. L., ANAL. CHEM.37, 902, 1965.
(1)
Shell Development CO. Emeryville, Calif.
J. MERRITT E. J. AGAZZI
