ISO 6676:1993
Withdrawn
A Withdrawn Standard is one, which is removed from sale, and its unique number can no longer be used. The Standard can be withdrawn and not replaced, or it can be withdrawn and replaced by a Standard with a different number.
Acid-grade and ceramic-grade fluorspar Determination of total phosphorus content Reduced-molybdophosphate spectrometric method
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22-02-2019
English, French
18-03-1993
The method specified is based on dissolution of a test portion by fusion with a mixture of sodium carbonate, boric acid and sodium nitrate and subsequent acidification with nitric acid, formation of the molybdophosphate complex and extraction with a mixture of ethyl acetate and butyl acetate, followed by selective reduction of the complex to molybdenum blue by means of tin(II) chloride added to the organic phase, spectrometric measurement of the absorbance of the coloured complex at the wavelength of maximum absorption (about 710 nm). Applies to products having total phosphorus contents, expressed as PO4^3-, in the range 0,01 % (m/m) to 1,0 % (m/m).
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