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A Test of the Precision and Sources of Error in Quantitative Analysis of Light, Major Elements in Granitic Rocks by X-Ray Spectrography
Published online by Cambridge University Press: 06 March 2019
Abstract
Quantitative analysis of major elements (Na, Mg, Al, Si, K, Ca, Ti, and Fe) in rocks by classic wet-chemical procedures, in addition to being a costly and laborious process, has been shown to be subject to significant errors. Mineralogists and petrologists, increasingly concerned with determining small elemental differences in rock bodies, have turned to more rapid and precise methods in the field of spectral analysis. The development of X-ray spectrographic techniques in the light-element range has therefore been of particular interest. This paper summarizes the results of a test of the precision and sources of error in the X-ray method as applied to major elements in granitic rocks.
The test, using commerically available equipment and the fusion technique of specimen preparation, was designed for a five-way, completely nested variance analysis. Sources of variance are (1) different lengths of fusion time, (2) replications of a single fusion time, (3) replications of briquetting the fused specimens, (4) replications of individual runs in the spectrograph, and (5) replications of individual spectrograph readings of the Kα line intensity. A total of 64 readings per element were obtained and the significance of each factor tested for each element. Greatest sources of error are shown to be in factors 2 and 4. The total variance for each element is expressed as per cent relative deviation of counts per second. Calibration curves of natural and synthetic granitic rocks, fused with dilutions ranging from 13 to 36% rock in borax, provide conversions from relative deviation in counts per second to relative deviation in weight per cent. These values indicate that the precision of the X-ray method is directly comparable with wet chemistry for Si, probably better for Al, and distinctly superior for K, Ca, Ti, and Fe. Of the major rock-forming elements only Na and Mg are presently beyond the scope of the fusion method.
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- Research Article
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- Copyright © International Centre for Diffraction Data 1961
References
1.
Fairbairn, H. W. and others, “A Cooperative Investigation of Precision and Accuracy in Chemical, Spectrochemical and Modal Analysis of Silicate Rocks,” U.S. Gaol. Survey Bull., 908, 1951.Google Scholar
2.
Stevens, R. E. and others, “Second Report on a Cooperative Investigation of the Composition of Two Silicate Rocks,” U.S. Geol. Survey Bull., p. 1113, 1960.Google Scholar
3.
Fairbairn, H. W. and Schairer, J. F., “A Test of the Accuracy of Chemical Analysis of Silicate Rocks,” Am. Mineralogist, Vol. 37, 1952, p. 744.Google Scholar
4.
Claisse, F., “Accurate X-ray Fluorescence Analysis Without Internal Standard,” Department of Mines, Province of Quebec, Canada, P. R. 327, 1956.Google Scholar
5.
Chodos, A. A. and Engel, C. G., “Fluorescent X-ray Spectrographic Analyses of Amphibolite Rocks ;md Constituent Hornblendes,” Advances in X-Ray Analysis, Vol. 4, University of Denver, Plenum Press, New York, 1961, pp. 401–413.Google Scholar
7.
Klug, H. P. and Alexander, L. E., X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials, John Wiley & Sons, New York, 1954.Google Scholar
8.
Bennett, C. A. and Franklin, N. L., Statistical Analysis in Chemistry and the Chemical Industry, John Wiley & Sons, New York, 1954, p. 319.Google Scholar