Photometric determination of phosphorus in ferroniobium, ferrotitanium and niobium ore
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概要
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A rapid method for the determination of phosphorus in ferroniobium, ferrotitanium and niobium ore, which involves the masking of niobium or titanium with fluoride ion and the extraction of phosphovanadomolybdic acid with methylisobutyl ketone, has been presented. <BR>Ferroniobium or ferrotitanium (0.1 g) is dissolved in a few m<I>l</I> of nitric and hydrofluoric acids and 1 m<I>l </I>of (1 : 1) sulfuric acid, and is evaporated nearly to dryness. A definite amount of the acid for giving the optimum acid concentration {5 m<I>l</I> of 10<I>N</I> sulfuric acid, 5 m<I>l</I> of 60% perchloric acid or 6 m<I>l</I> of (1 : 1) nitric acid} and an amount of 2% ammonium fluoride solution, 20 m<I>l</I> for ferroniobium or 15 m<I>l</I> for ferrotitanium, are added, and the salts are dissolved by gentle heating. After cooling, 5 m<I>l</I> of 1.2% ammonium vanadate and 10 m<I>l</I> of 10% ammonium molybdate are added, and the solution is diluted to about 50 m<I>l</I> with water. After standing for 10 minutes, 10 m<I>l</I> of methylisobutyl ketone is added, and it is shaken for 10 seconds. The organic layer is dry-filtered, and the absorbance is measured at 420 mμ.<BR>Niobium ore (0.5 g) is fused with 34 g of sodium peroxide, and decomposed with water. After additions of 1 g of ammonium fluoride and 1 drop of hydrogen peroxide (30%), the solution is neutralized with nitric acid and then 20 m<I>l </I>in excess. After cooling, the solution is diluted to 200 m<I>l</I> with water. To a 40 m<I>l</I> aliquot are added 5 m<I>l</I> of 1.2% ammonium vanadate and 5 m<I>l</I> of 10% ammonium molybdate, and then the procedure is carried through as above. <BR>The methods are very rapid, and the accuracies are 1.54.0% for ferroniobium or ferrotitanium and 3.56.4% for niobium ore.
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