Modern inorganic chemistry

THE TRANSITION ELEMENTS 373

TESTS FOR TITANIUM

Aqueous solutions containing titanium(IV) give an orange-yellow

colour on addition of hydrogen peroxide; the colour is due to the

formation of peroxo-titanium complexes, but the exact nature of

these is not known.

VANADIUM

THE ELEMENT

Vanadium is by no means as common as titanium, but it occurs in
over sixty widely distributed vanadium ores. It is named after
Vanadis (a name of the Scandinavian goddess Freia), because it
forms compounds having many rich colours. Vanadium is a silver-
grey metal; it is not very useful itself, and most of the metal produced
is in the form of an alloy ferrovanadium, containing between 40 and
90% vanadium. This is adde^ to steel to produce a very tough
'high-speed' steel. Ferrovanac|i|im is obtained by reduction of the
oxide V 2 O 5 with "ferrosilicorfl (Fe 4- Si). The pure metal is very
difficult to prepare because it combines even more readily with
hydrogen, carbon, nitrogen and oxygen than does titanium; as with
the latter, the compounds produced are often interstitial and non-
stoichiometrie, but with oxygen the pentoxide V 2 O 5 is ultimately
obtained. Vanadium dissolves readily in oxidising acids.
With the outer electronic configuration 3d^3 4s^2 vanadium can
attain an oxidation state of + 5, but it shows all oxidation states
between + 5 and + 2 in aqueous solution (cf. titanium).

COMPOUNDS OF VANADIUM

Oxidation state + 5

Although vanadium has formally lost all its outer electrons in this

state, the resemblance to the Group V elements is not so marked

as that of titaniumdV) to Group IV.

HALIDES

The vanadium(V) state is very strongly oxidising; hence the only

stable halide is the fluoride VF 5 , a white, easily hydrolysed solid