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The analysis of molybdates and tungstates

Published online by Cambridge University Press:  14 March 2018

A. J. Easton
Affiliation:
Department of Mineralogy, British Museum (Nat. Hist.), London, S.W. 7
A. A. Moss
Affiliation:
Department of Mineralogy, British Museum (Nat. Hist.), London, S.W. 7

Summary

The estimation of molybdenum and tungsten when present together has proved difficult, as is indicated by the large number of methods put forward for their determination. Many of the methods given are for one or other of these elements only, a note often being added that the presence of the other invalidates the method. The estimation of molybdate and tungstate in the mineral powellite has been briefly described by one of the authors (A. A. M.): molybdate and tungstate were precipitated as oxinates (Mo,W)O2(C9H6ON)2 and the molybdate (MoO4″) determined by measurement of the optical density at 230 mµ of a solution containing molybdate and tungstate. The amount of tungstate present was then estimated by difference. The property of the molybdate ion, MoO4″, to absorb strongly in the ultra-violet has been further investigated and it has been found that, if a wave-length of 240 mµ is chosen and the proper precautions taken, the MoO4″ ion can be estimated without significant interference by the WO4″ ion. Methods are given for the analysis of the common molybdate and tungstate minerals, together with results obtained during the course of this investigation.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1966

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References

page 995 note 1 Bachman, R. Z. and Banks, C. V., 1965. Anal. Chem., vol. 37, p. 111R.CrossRefGoogle Scholar

page 995 note 2 Batty, M. H. and Moss, A. A., 1962. Min. Mag., vol. 33, p. 160.Google Scholar

page 995 note 3 Anthoinite is an exception, see p. 1001.

page 997 note 1 Distilled water should be stored in glass containers. Water that has been stored in polythene has an appreciable absorption at 240 mμ.

page 997 note 2 All filter papers must be washed with distilled water before use in order to remove soluble substances that absorb at 240 mμ.

page 998 note 1 Silica is determined eolorimetrically.

page 1001 note 1 Experiments using a thermobalance confirmed the temperature recommended by Simpson, E. S., 1926. Journ. Roy. Soc. Western Australia, vol. 12, p. 57 Google Scholar.

page 1001 note 2 Varlamoff, N., 1947. Bull. Soc. Géol. Belgique, vol. 70, p. 153.Google Scholar