V, like Mo, would accompany Sn(IV) in the
filtrate too. As shown in its predominance-zone
diagram, it is at pH 5.0–5.5 in the state of
vanadyl vanadate, i.e. partly as V(IV) and partly
as V(V) [21]. Hence, effects of both V(V) and
V(IV) should be studied. It was found that in the
presence of EDTA, TDTC does not precipitate
either of them at the stated pH to form the same
yellow product. The only difference lies in that
this precipitation takes place at once in the case of
V(V), but slows down somewhat in the case of
V(IV).