A NEW POTENTIOMETRIC METHOD FOR THE DETERMINATION OF TANTALUM IN ALLOYS USING TAF6 ION-SELECTIVE ELECTRODE

In the present paper, a new direct potentiometric method, using ion-selective ectrode based on PVC matrix containing fluorotantalate-ion sensor plus solvent mediator repared in this laboratory developed for the determination of small amounts of tantalum in iokel-base, iron-base, niobium-titanium alloy and niobium metal is presented.In the presenoe f F, tantalum is converted to TaP_6~- and its activity or concentration oan be measured direotly y using the eleotrode. The electrode response, interferences, the use of standard addition ethod and possible application of this method are disoussed.The results show that the lectrode esponese is a linear function of TaF_6~- in10~100μg range of Ta in a medium of 1.0M HF-0.5M H_SO_4 and with a definite concentration of oxalate as metal Complexing agent. In order to minimise the ffect of total ionio strength, the standard addition technique is applied.The influence of the major onstituents of suoh alloys is studied. No interference has been noted for amounts up to 0.1g of Ni~(2+)or, .2g of Fe~(3+). The amount of Al~(3+),Cr~(3+) or Ti~(4+) can be tolerated to 1000-fold of Ta, Zr~(4) r V~(5+) to 50-fold, Mo~(6+), W~(6+) or SiO_3~(2-) to 10-fold and B to 2-fold. The effect of 10mg of iobium is the same as 2.5 μg of tantalum. It does not depend on the proportion of Nb and Ta in the ample, so that the effect can be corrected by the deduction of 0.025% of the Nb content.This eleotrode ase procedure offers considerable advantages of more simplicity, nigher speed and lower oost in omparison with the conventional methods.