Abstract
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.
Ferroniobium or ferrotitanium (0.1 g) is dissolved in a few ml of nitric and hydrofluoric acids and 1 ml of (1 : 1) sulfuric acid, and is evaporated nearly to dryness. A definite amount of the acid for giving the optimum acid concentration {5 ml of 10N sulfuric acid, 5 ml of 60% perchloric acid or 6 ml of (1 : 1) nitric acid} and an amount of 2% ammonium fluoride solution, 20 ml for ferroniobium or 15 ml for ferrotitanium, are added, and the salts are dissolved by gentle heating. After cooling, 5 ml of 1.2% ammonium vanadate and 10 ml of 10% ammonium molybdate are added, and the solution is diluted to about 50 ml with water. After standing for 10 minutes, 10 ml 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.
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 ml in excess. After cooling, the solution is diluted to 200 ml with water. To a 40 ml aliquot are added 5 ml of 1.2% ammonium vanadate and 5 ml of 10% ammonium molybdate, and then the procedure is carried through as above.
The methods are very rapid, and the accuracies are 1.54.0% for ferroniobium or ferrotitanium and 3.56.4% for niobium ore.
