 10 ) can only be formed by oxidation by concentrated nitric acid . Antimony also forms a mixed @-@ valence oxide , antimony tetroxide ( Sb 
 10 ) can only be formed by oxidation by concentrated nitric acid . Antimony also <a href='uninflect' title='1'><mark>forms</mark></a> a mixed @-@ valence oxide , antimony tetroxide ( Sb 
10 ) can only b formed by oxidation by concentrated nitric acid . Antimony also form a mixed @-@ valence oxide , antimony tetroxide ( Sb