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A note on the relationship between the precision of classical methods of rock analysis and the concentration of each constituent

Published online by Cambridge University Press:  14 March 2018

L. H. Ahrens
L. H. Ahrens*
Affiliation:
Department of Geology and Mineralogy, University Museum, Oxford
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Extract

A Granite (G-1) from Westerley, Rhode Island, and a diabase (W-1) from Centerville, Virginia, were recently analysed by some 34 analysts in different countries for the purpose of obtaining thoroughly reliable rock standards for spectrochemical analysis. Most determinations were made by so-called classical methods of chemical analysis. The results of the investigation have been discussed by Fairbairn and others. Fairbairn examined the results statistically and, using the relative deviation (standard deviation expressed as a percentage) as a measure of precision, concluded that precision deteriorated with a decrease in the concentration of a constituent. In the present paper this general observation will be demonstrated quantitatively by means of a graphical presentation, thus providing the petrologist with a guide for rapidly assessing and comparing the precision of classical methods of chemical analysis over considerable concentration ranges.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 30 , Issue 226 , September 1954 , pp. 467 - 470
Copyright
Copyright © 1954, The Mineralogical Society

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References

1 H.W.Fairbairn, W.G.Schlecht, R.E.Stevens, W.H.Demlen, L.H.Ahrens, and F. Chayes, A co-operative investigation of precision and accuracy in chemical, spectrochemical and modal analysis of Silicate rocks. Bull. U.S. Geol. Surv., 1951.no. 980. Schlecht, W.G., Co-operative investigation of precision and accuracy. Anal Chem., 1951. vol. 23, p. 1568 CrossRefGoogle Scholar. Fairbairn, H.W. and Schairer, J.F., A test of the accuracy of chemical analyses of silicate rocks. Amer. Min., 1952. vol. 37, pp. 744-757.Google Scholar [M.A. 12-33.] Fairbairn, H.W., Precision and accuracy of chemical analysis of silicate rocks. Geochim. Cosmoehim. Acta, 195., vol. 4, pp. 143 Google Scholar.I56. [M.A. 12-264.]

2 Positive skewness, negative skewness, irregular distributions, as well as normal and lognormal type distributions have been observed for the particular series of chemical observations under discussion.